Posted on by Tammy Plotner

Messier 19 (M19) – The NGC 6273 Globular Cluster

Messier Object 19, as imaged with an amateur telescope.Credit: Hewholooks/Wikipedia Commons

Welcome back to Messier Monday! In our ongoing tribute to the great Tammy Plotner, we take a look at the Messier 19 globular star cluster. Enjoy!

In the 18th century, while searching the night sky for comets, French astronomer Charles Messier began noticing a series of “nebulous objects” in the night sky. Hoping to ensure that other astronomers did not make the same mistake, he began compiling a list of these objects,. Known to posterity as the Messier Catalog, this list has come to be one of the most important milestones in the research of Deep Sky objects.

One of these objects is Messier 19, a globular star cluster located in the constellation Ophiuchus. Of all the known globular clusters, M19 appears to be one of the most oblate (i.e. flattest) in the night sky. Discovered by William Herschel, this cluster is relatively difficult to spot with the naked eye, and appears as a fuzzy point of light with the help of magnification.

Description:

Speeding away from us at a rate of 146 kilometers per second, this gravitationally bound ball of stars measuring 140 light years in diameter, is one of the Messier globular clusters that has the distinction of being closest to the center of the Milky Way. At a little more than 5000 light-years from the intense gravitation of our own galactic core, it has played havoc on M19’s round shape.

In essence, Milky Way’s gravity has caused M19 to become one of the most oblate of all globular clusters, with twice as many stars along the major axis as along the minor. And, although it is 28,000 light-years from Earth, it’s actually on the opposite side of the galactic core. For all of its rich, dense mass, four RR Lyrae variable stars have been found in M19.

The constellation Ophiuchis. Credit: iau.org
The constellation Ophiuchis. Credit: iau.org

Is Messier 19 unique? It has some stellar branch properties that are difficult to pinpoint. And even its age (though estimated at around 11.9 billion years old) is indeterminate. Says F. Meissner and A. Weiss in their 2006 study, “Global fitting of globular cluster age indicators“:

“The determination of globular cluster (GC) ages rests on the fact that colour-magnitude diagrams (CMDs) of single-age single composition stellar populations exhibit specific time-dependent features. Most importantly, this is the location of the turn-off (TO), which – together with the cluster’s distance – serves as the most straightforward and widely used age indicator. However, there are other parts of the CMD that change their colour or brightness with age, too. Since the sensitivity to time is different for the various parts of the cluster CMD, it is possible to use either the various indicators independently, or the differences in colour and brightness between pairs of them; these latter methods have the advantage of being independent of distance.”

What’s occurring is a horizontal branch gap – an not-quite explainable difference in the way the stars inside M19 are aging. However, science is looking for the answer. As G. Busso et al. explained in their 2008 paper titled “The Peculiar Horizontal Branch Morphology of the Galactic Globular Clusters NGC 6388 and NGC 6441“:

“I show that a possible solution of the puzzle is to assume that a small fraction of the stellar population in the two clusters is strongly helium enriched. The presence of two distinct stellar populations characterized by two different initial He contents can help in explaining the brightness difference between the red portion of the HB and the blue component.”

The Messier 19 globular cluster, as viewed by the Two Micron All-Sky Survey (2MASS). Credit: 2MASS/ipac.caltech.edu
The Messier 19 globular cluster, as viewed by the Two Micron All-Sky Survey (2MASS). Credit: 2MASS/ipac.caltech.edu

Is helium the answer? Quite probably so. M. Salaris Astrophysics Research Institute and an international team of researchers explained in their 2004 study “The initial helium abundance of the Galactic globular cluster system“:

“Based on a recently updated set of stellar evolution models, we performed an accurate statistical analysis in order to assess whether GGCs show a statistically significant spread in their initial He abundances, and whether there is a correlation with the cluster metallicity. As in previous works on the subject, we do not find any significant dependence of the He abundance on the cluster metallicity; this provides an important constraint for models of Galaxy formation and evolution. Apart from GGCs with the bluest Horizontal Branch morphology, the observed spread in the individual helium abundances is statistically compatible with the individual errors. This means that either there is no intrinsic abundance spread among the GGCs, or that this is masked by the errors. In the latter case we have estimated a firm upper limit of 0.019 to the possible intrinsic spread. In case of the GGCs with the bluest Horizontal Branch morphology we detect a significant spread towards higher abundances inconsistent with the individual errors; this can be fully explained by additional effects not accounted for in our theoretical calibrations, which do not affect the abundances estimated for the clusters with redder Horizontal Branch morphology.”

History of Observation:

M19 was one of Charles Messier’s original discoveries, which he first observed on June 5th, 1764. In his notes, he wrote:

“I have discovered a nebula, situated on the parallel of Antares, between Scorpius and the right foot of Ophiuchus: that nebula is round & doesn’t contain any star; I have examined it with a Gregorian telescope which magnified 104 times, it is about 3 minutes of arc in diameter: one sees it very well with an ordinary refractor of 3 feet and a half. I have observed its passage of the Medirian, and compared it with that of the star Antares; I have determined the right ascension of that nebula of 252d 1′ 45″, and its declination of 25d 54′ 46″ south. The known star closest to that nebula is the 28th of the constellation Ophiuchus, after the catalog of Flamsteed, of sixth magnitude.”

Messier 19 and Antares. Credit: Wikisky
The Messier 19 globular cluster, relative to M4, M80 and Antares. Credit: Wikisky

While Charles didn’t resolve it, we must give him due credit for discovery, for its size wouldn’t make it a particularly easy object given his optics. Later, in 1784, William Herschel would become the first to open up its true identity:

“When the 19th of the Connoiss. is viewed with a magnifying power of 120, the stars are visible; the cluster is insulated; some of the small stars scattered in the neighborhood are near it; but they are larger than those belonging to the cluster. With 240 it is better resolved, and is much condensed in the centre. With 300 no nucleus or central body can be seen. The diameter with the 10 feet is 3’16”, and the stars in the centre are too accumulated to be separately seen. It will not be necessary to add that the two last mentioned globular clusters, viewed with more powerful instruments, are of equal beauty with the rest; and from what has been said it is obvious that here the exertion of a clustering power has brought the accumulation and artificial construction of these wonderful celestial objects to the highest degree of mysterious perfection.”

While you may – or may not – resolve Messier 19’s individual stars, even small telescopes can pick up on some of its ellipticity and larger telescopes will make out a definite blue tinge to its coloration. Before you yawn at viewing another globular cluster, remember that you are looking at the other side of our galactic center and think on the words about M19 from Admiral Symth.

“The whole vicinity,” he wrote, “afford a grand conception of the grandeur and richness even of the exterior creation; and indicate the beautious gradation and variety of the heaven of heavens. Truly has it been said, “Stars teach us as well as shine.” This is near the large opening or hole, about 4deg broad, in the Scorpion’s body, which WH [William Herschel] found almost destitute of stars.”

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The Messier 19 globular cluster, as imaged by the Hubble Space Telescope. Credit:NASA/STSc /HST/WikiSky

Locating Messier 19:

Finding M19’s location in binoculars is quite easy – it’s less than a fistwidth (8 degrees) east of Antares (Alpha Scorpi). However, ‘seeing’ M19 in binoculars (especially smaller ones) is a little more problematic. The steadier the binoculars are, the better your chances, since it will appear almost stellar at first glance. A good indicator is to have optical double 26 Ophiuchi in the field at the 2:00 position and look for the star that won’t quite come to focus in the 8:00 position.

Star 26 also makes for a great finderscope lead when locating M19 in a telescope as well. Even for aperture sizes as small as 114mm, this globular cluster will show quite easily in a telescope and reveal its oblate nature. When aperture size increase to the 8″ range, it will begin resolution and as it nears 12″ or more, you’ll pick up on blue stars.

And for your convenience, here are the quick facts of M19:

Object Name: Messier 19
Alternative Designations: M19, NGC 6273
Object Type: Class VIII Globular Star Cluster
Constellation: Ophiuchus
Right Ascension: 17 : 02.6 (h:m)
Declination: -26 : 16 (deg:m)
Distance: 28.0 (kly)
Visual Brightness: 6.8 (mag)
Apparent Dimension: 17.0 (arc min)

We have written many interesting articles about Messier Objects here at Universe Today. Here’s Tammy Plotner’s Introduction to the Messier Objects, , M1 – The Crab Nebula, M8 – The Lagoon Nebula, and David Dickison’s articles on the 2013 and 2014 Messier Marathons.

Be to sure to check out our complete Messier Catalog. And for more information, check out the SEDS Messier Database.

Posted on by Matt Williams

Jupiter Compared to Earth

Rough visual comparison of Jupiter, Earth, and the Great Red Spot. Approximate scale is 44 km/px. Credit: NASA/Brian0918/ Wikipedia Commons

Ever since Galileo Galilei first observed Jupiter closely in 1610 using a telescope of his own design, scientists and astronomers have been immensely fascinated by the Jovian planet. Not only is it the Solar System’s largest planet, but there are still things about this world – despite centuries of research and numerous exploration missions – that continue to mystify even our greatest minds.

One of the main reasons for this is because Jupiter is so starkly different from what we Earth-dwellers consider to be normal. Between its incredible size, mass, composition, the mysteries of its magnetic and gravitational fields, and its impressive system of moons, its existence has shown us just how diverse planets can truly be.

Size, Mass and Density:

Earth’s has a mean radius of 6,371 km (3,958.8 mi), and a mass of 5.97 × 1024 kg, whereas Jupiter has a mean radius of 69,911 ± 6 km (43441 mi) and a mass of 1.8986×1027 kg. In short, Jupiter is almost 11 times the size of Earth, and just under 318 times as massive. However, Earth’s density is significantly higher, since it is a terrestrial planet – 5.514 g/cm3 compared to 1.326 g/cm³.

Because of this, Jupiter’s “surface” gravity is significantly higher than Earth normal – i.e. 9.8 m/s² or 1 g. While, as a gas giant, Jupiter has no surface per se, astronomers believe that within Jupiter’s atmosphere where the atmospheric pressure is equal to 1 bar (which is equal to Earth’s at sea level), Jupiter experiences a gravitational force of 24.79 m/s2 (which is the equivalent of 2.528 g).

Jupiter/Earth comparison. Credit: NASA/SDO/Goddard/Tdadamemd
Jupiter/Earth comparison. Credit: NASA/SDO/Goddard/Tdadamemd

Composition and Structure:

Earth is a terrestrial planet, which means it is composed of silicate minerals and metal that are differentiated between a metal core and a silicate mantle and crust. The core itself is also differentiated, between an inner core and outer core (which spins in the opposite direction of Earth’s rotation). As one descends from the crust to the interior, temperatures and pressure increase.

The shape of Earth approximates that of an oblate spheroid, a sphere flattened along the axis from pole to pole such that there is a bulge around the equator. This bulge results from the rotation of Earth, and causes the diameter at the equator to be 43 kilometers (27 mi) larger than the pole-to-pole diameter.

In contrast, Jupiter is composed primarily of gaseous and liquid matter which is divided between a gaseous outer atmosphere and a denser interior. It’s upper atmosphere is composed of about 88–92% hydrogen and 8–12% helium by volume of gas molecules, and approx. 75% hydrogen and 24% helium by mass, with the remaining one percent consisting of other elements.

The atmosphere contains trace amounts of methane, water vapor, ammonia, and silicon-based compounds as well as trace amounts of benzene and other hydrocarbons. There are also traces of carbon, ethane, hydrogen sulfide, neon, oxygen, phosphine, and sulfur. Crystals of frozen ammonia have also been observed in the outermost layer of the atmosphere.

upiter's structure and composition. (Image Credit: Kelvinsong CC by S.A. 3.0)
Jupiter’s structure and composition. (Image Credit: Kelvinsong CC by S.A. 3.0)

The denser interior is composed of roughly 71% hydrogen, 24% helium and 5% other elements by mass. It is believed that Jupiter’s core is a dense mix of elements – a surrounding layer of liquid metallic hydrogen with some helium, and an outer layer predominantly of molecular hydrogen. The core has also been inferred as being rocky, but this remains unknown as well.

And much like Earth, temperatures and pressures inside Jupiter increase dramatically toward the core. At the “surface”, the pressure and temperature are believed to be 10 bars and 340 K (67 °C, 152 °F). In the region where hydrogen becomes metallic, it is believed that temperatures reach 10,000 K (9,700 °C; 17,500 °F) and pressures 200 GPa. The temperature at the core boundary is estimated to be 36,000 K (35,700 °C; 64,300 °F) and the interior pressure at roughly 3,000–4,500 GPa.

Also like Earth, Jupiter’s shape is that of an oblate spheroid. In fact, Jupiter’s polar flattening is greater than that of Earth’s  – 0.06487 ± 0.00015 compared to 0.00335. This is due to Jupiter’s rapid rotation on its axis, and is why the planet’s equatorial radius is approximately 4600 km larger than its polar radius.

Orbital Parameters:

Earth has a very minor orbital eccentricity (approx. 0.0167) and ranges in distance from 147,095,000 km (0.983 AU) from the Sun at perihelion to 151,930,000 km (1.015 AU) at aphelion. This works out to an average distance (aka. semi-major axis) of 149,598,261 km, which is the basis of a single Astronomical Unit (AU).

The asteroids of the inner Solar System and Jupiter: The donut-shaped asteroid belt is located between the orbits of Jupiter and Mars. Credit: Wikipedia Commons
The orbits of the inner planets of the Solar System, with Jupiter and the donut-shaped asteroid belt is located between them. Credit: Wikipedia Commons

The Earth has an orbital period of 365.25 days, which is the equivalent of 1.000017 Julian years. This means that every four years (in what is known as a Leap Year), the Earth calendar must include an extra day. Though technically a full day is considered to be 24 hours long, our planet takes precisely 23h 56m and 4 s to complete a single sidereal rotation (0.997 Earth days). But combined with its orbital period around the Sun, the time between one sunrise and another (a Solar Day) is 24 hours.

Viewed from the celestial north pole, the motion of Earth and its axial rotation appear counterclockwise. From the vantage point above the north poles of both the Sun and Earth, Earth orbits the Sun in a counterclockwise direction. Earth’s axis is tilted also 23.4° towards the ecliptic of the Sun, which is responsible for producing seasonal variations on the planet’s surface. In addition to producing variations in temperature, this also results in variations in the amount of sunlight a hemisphere receives during the course of a year.

Meanwhile, Jupiter orbits the Sun at an average distance (semi-major axis) of 778,299,000 km (5.2 AU), ranging from 740,550,000 km (4.95 AU) at perihelion and 816,040,000 km (5.455 AU) at aphelion. At this distance, Jupiter takes 11.8618 Earth years to complete a single orbit of the Sun. In other words, a single Jovian year lasts the equivalent of 4,332.59 Earth days.

The Juno spacecraft isn't the first one to visit Jupiter. Galileo went there in the mid 90's, and Voyager 1 snapped a nice picture of the clouds on its mission. Image: NASA
The banded appearance of Jupiter’s upper atmopshere, which is partly due to its rapid rotation. Credit: NASA

However, Jupiter’s rotation is the fastest of all the Solar System’s planets, completing a single rotation on its axis in slightly less than ten hours (9 hours, 55 minutes and 30 seconds). Therefore, a single Jovian year lasts 10,475.8 Jovian solar days.

Atmospheres:

Earth’s atmosphere is made up of five main layers – the Troposphere, the Stratosphere, the Mesosphere, the Thermosphere, and the Exosphere. As a rule, air pressure and density decrease the higher one goes into the atmosphere and the farther one is from the surface. However, the relationship between temperature and altitude is more complicated, and may even rise with altitude in some cases.

The troposphere contains roughly 80% of the mass of Earth’s atmosphere, with some 50% located in the lower 5.6 km (3.48 mi), making it denser than all its overlying atmospheric layers. It is primarily composed of nitrogen (78%) and oxygen (21%) with trace concentrations of water vapor, carbon dioxide, and other gaseous molecules.

Nearly all atmospheric water vapor or moisture is found in the troposphere, so it is the layer where most of Earth’s meteorological phenomena (clouds, rain, snow, lightning storms) take place. The one exception is the Thermoposphere, where the phenomena known as Aurora Borealis and Aurara Australis (aka. The Northern and Southern Lights) are known to take place.

As already noted, Jupiter’s atmosphere is composed primarily of hydrogen and helium, with trace amounts of other elements. Much like Earth, Jupiter experiences auroras near its northern and southern poles. But on Jupiter, the auroral activity is much more intense and rarely ever stops. The intense radiation, Jupiter’s magnetic field, and the abundance of material from Io’s volcanoes that react with Jupiter’s ionosphere create a light show that is truly spectacular.

Jupiter also experiences violent weather patterns. Wind speeds of 100 m/s (360 km/h) are common in zonal jets, and can reach as high as 620 kph (385 mph). Storms form within hours and can become thousands of km in diameter overnight. One storm, the Great Red Spot, has been raging since at least the late 1600s. The storm has been shrinking and expanding throughout its history; but in 2012, it was suggested that the Giant Red Spot might eventually disappear.

Jupiter is perpetually covered with clouds composed of ammonia crystals and possibly ammonium hydrosulfide. These clouds are located in the tropopause and are arranged into bands of different latitudes, known as “tropical regions”. The cloud layer is only about 50 km (31 mi) deep, and consists of at least two decks of clouds: a thick lower deck and a thin clearer region.

Composite images from the Chandra X-Ray Observatory and the Hubble Space Telescope show the hyper-energetic x-ray auroras at Jupiter. The image on the left is of the auroras when the coronal mass ejection reached Jupiter, the image on the right is when the auroras subsided. The auroras were triggered by a coronal mass ejection from the Sun that reached the planet in 2011. Image: X-ray: NASA/CXC/UCL/W.Dunn et al, Optical: NASA/STScI
Composite images from the Chandra X-Ray Observatory and the Hubble Space Telescope show the hyper-energetic x-ray auroras at Jupiter. Credit: NASA/CXC/UCL/W.Dunn et al/STScI

There may also be a thin layer of water clouds underlying the ammonia layer, as evidenced by flashes of lightning detected in the atmosphere of Jupiter, which would be caused by the water’s polarity creating the charge separation needed for lightning. Observations of these electrical discharges indicate that they can be up to a thousand times as powerful as those observed here on the Earth.

Moons:

Earth has only one orbiting satellite, The Moon. It’s existence has been known of since prehistoric times, and it has played a major role in the mythological and astronomical traditions of all human cultures and has a significant effect on Earth’s tides. In the modern era, the Moon has continued to serve as a focal point for astronomical and scientific research, as well as space exploration.

In fact, the Moon is the only celestial body outside of Earth that humans have actually walked on. The first Moon landing took place on July 20th, 1969, and Neil Armstrong was the first person to set foot on the surface. Since that time, a total of 13 astronauts have been to the Moon, and the research that they carried out has been instrumental in helping us to learn about its composition and formation.

Thanks to examinations of Moon rocks that were brought back to Earth, the predominant theory states that the Moon was created roughly 4.5 billion years ago from a collision between Earth and a Mars-sized object (known as Theia). This collision created a massive cloud of debris that began circling our planet, which eventually coalesced to form the Moon we see today.

Illustration of Jupiter and the Galilean satellites. Credit: NASA
Illustration of Jupiter and the Galilean satellites. Credit: NASA

The Moon is one of the largest natural satellites in the Solar System and is the second-densest satellite of those whose densities are known (after Jupiter’s satellite Io). It is also tidally locked with Earth, meaning that one side is constantly facing towards us while the other is facing away. The far side, known as the “Dark Side”, remained unknown to humans until probes were sent to photograph it.

The Jovian system, on the other hand, has 67 known moons. The four largest are known as the Galilean Moons, which are named after their discoverer, Galileo Galilei. They include: Io, the most volcanically active body in our Solar System; Europa, which is suspected of having a massive subsurface ocean; Ganymede, the largest moon in our Solar System; and Callisto, which is also thought to have a subsurface ocean and features some of the oldest surface material in the Solar System.

Then there’s the Inner Group (or Amalthea group), which is made up of four small moons that have diameters of less than 200 km, orbit at radii less than 200,000 km, and have orbital inclinations of less than half a degree. This groups includes the moons of Metis, Adrastea, Amalthea, and Thebe. Along with a number of as-yet-unseen inner moonlets, these moons replenish and maintain Jupiter’s faint ring system.

Jupiter also has an array of Irregular Satellites, which are substantially smaller and have more distant and eccentric orbits than the others. These moons are broken down into families that have similarities in orbit and composition, and are believed to be largely the result of collisions from large objects that were captured by Jupiter’s gravity.

In just about every way imaginable, Earth and Jupiter could not be more different. And there are still many things about the Jovian planet that we do not yet fully understand. Speaking of which, be sure to stay tuned to Universe Today for the latest updates from NASA’s Juno mission.

We have written many interesting articles about the planets of the Solar System here at Universe Today. Here’s Earth Compared to Mercury, Earth Compared to Venus, The Moon Compared to Earth, Earth Compared to Mars, Saturn Compared to Earth, and Neptune Compared to Earth.

Want more information on Jupiter? Here’s a link to Hubblesite’s News Releases about Jupiter, and here’s NASA’s Solar System Exploration Guide.

We have recorded a podcast just about Jupiter for Astronomy Cast. Click here and listen to Episode 56: Jupiter.

Posted on by Bob King

We’re Finally Sending Ears to Mars

Be patient. We'll soon be hearing from Mars. Left: Wikipedia CC BY-SA 3.0; right: NASA/JPL-Caltech
The Curiosity rover took this photo of the Martian landscape on July 12, 2016. Imagine if we could listen to it at the same time. NASA now plans to include a microphone on the upcoming Mars 2020 Mission. Credit: NASA/JPL-Caltech
The Curiosity rover took this photo of the Martian landscape on July 12, 2016. Imagine if we could hear the wind passing by. We will soon. NASA plans to include a microphone on the upcoming Mars 2020 Mission. Credit: NASA/JPL-Caltech

We all love that feeling of “being there” when it comes to missions to other planets.  Juno’s arrival at Jupiter, New Horizons’ flyby of Pluto and the daily upload of raw images from the Mars Curiosity rover makes each of us an armchair explorer of alien landscapes. But there’s always been something missing. Something essential in shaping our environment — sound.

The microphone selected for the Mars 2020 Mission would be mounted It would be mounted on a tiny tube that protrudes from the warm electronics box, on the bracket that holds the window for the SuperCam instrument. Credit: S. Mauric et. all, 47th Lunar and Planetary Science Conference
The microphone selected for the Mars 2020 Mission would be mounted It would be mounted on a tiny tube that protrudes from the warm electronics box, on the bracket that holds the window for the SuperCam instrument. Credit: S. Mauric et. all, 47th Lunar and Planetary Science Conference

NASA recently gave the go-ahead for the Mars 2020 rover that will bristle with a new suite of science instruments including a microphone. Hallelujah! Finally, we’ll get to listen to the sound of the Martian wind, the occasional whirl of dust devils, the crunch of rocks beneath the rover’s wheels and even sharp pops from laser-zapped rocks!

These photos show the microphones used in two earlier missions. Neither was ever used. On left, the Mars Descent Imager and microphone for the Phoenix lander; right, the device for the failed Mars Polar Lander. Credit: NASA/JPL-Caltech
Microphones were included on two earlier missions but never used. On left, the Mars Descent Imager and microphone for the Phoenix lander; right, the device for the failed Mars Polar Lander mission. Credit: NASA/JPL-Caltech

The staff and membership of The Planetary Society have been trying for 20 years to get a working microphone to the Red Planet. One flew aboard NASA’s Mars Polar Lander mission in 1998 but that probe crashed landed when its engine shut down prematurely during the descent phase. In 2008 the Society partnered with Malin Space Science Systems to include its next microphone in the descent imager package on the Mars Phoenix lander in 2008. While that mission was successful,  the imager (along with its microphone) was turned off for fear it might cause an electrical problem with a critical landing system. Mission planners hoped it might be turned on later but whether it was a money issue or fear of shorting out other critical lander instruments, it never happened. Heartbreaking.

One sound souvenir we did get from Phoenix comes to us from the European Space Agency’s Mars which recorded the radio transmissions from the lander as it descended. The signals were then processed into audio within the range of human hearing. Give a listen, there’s a music to it.

The microphone for the upcoming Mars mission will be attached to the SuperCam, seen here in this illustration zapping a rock with its laser. Credit: NASA/JPL-Caltech
The microphone for the upcoming Mars mission will be attached to the rover’s SuperCam, seen here in this illustration zapping a rock with its laser. Credit: NASA/JPL-Caltech

The Mars 2020 mission, which is expected to launch in the summer of 2020 and land the following February, will search directly for signs of ancient Martian life as well as identify and cache samples and specimens at several locations on the surface for pick-up by later missions. The microphone would be housed with the rover’s SuperCam, a souped-up version of Curiosity’s ChemCam, which fires a laser at rocks and soils from a distance to analyze the resulting vapors for their elemental composition.

SuperCam will also shoot a laser to vaporize rocks and spectroscopy to tease out their molecular and mineral composition. The microphone would be mounted on a tube sticking out of the electronics box housing SuperCam and used for scientific purposes but I suspect for public outreach as well. One of its more intriguing uses will be to record the ‘snap’ or ‘pop’ when a rock is struck with the laser. Based on the volume of the sound, scientists can estimate the specimen’s mass.

NASA plans to land the 1-ton rover using the same sky crane method that settled Curiosity to the surface in dramatic fashion. While the rover will be busy photographing the entry, descent and landing sequence, the microphone will record the ambient sound. Synched together, this should make for one of the most compelling videos ever!

A beautiful dust devil recorded by NASA's Opportunity rover. Wouldn't it be wonderful to hear it at the same time as viewing the photo? Credit: NASA/JPL-Caltech/James Sorenson
A tall, beautiful dust devil recorded by NASA’s Opportunity rover. Wouldn’t it be wonderful to hear it at the same time as viewing the photo? Credit: NASA/JPL-Caltech/James Sorenson

The microphone will also be used to augment studies of Martian weather (the aforementioned winds and dust devils) and listen to the rover’s creaks, groans and whir of its motors as the car-sized machine rolls across the alternately sandy and rocky surface of Mars. The Planetary Society is collaborating with the SuperCam team to make the most of the microphone. Who knows what else we might hear? Exploding fireball overhead? Static electricity? Rhythmic winds? Blowing sand? Slime-slap of alien pseudopods? OK, probably not the last one, but new instruments often reveal completely unexpected phenomena.

It’s been hard as hell getting a microphone on a space mission. They’ve had to compete with other instruments considered more essential not to mention the precious space the device would take up and the burden of additional mass. Mission planners consider every fraction of a gram when building a space probe because getting it into Earth orbit and blasting it to a planet takes energy. Rockets only hold so much fuel!


Your Voice on Mars

You might wonder if Mars’ atmosphere is thick enough to carry sound. The good news is that it is, but unlike Earth’s much denser nitrogen-oxygen mix, Martian air is 100 times thinner and composed of 95% carbon dioxide. If you could snap off your helmet and talk out loud on the Red Planet, your voice would sound deeper and not travel as far. Scientists liken it to having a conversation at 100,000 feet (30,500 meters) above Earth’s surface. Check out the crazy video for a simulation.

Now that you’ve made it to the end of this story, sit back and pump up the volume. We’ll have ears on Mars soon!


Pump Up the Volume by M|A|R|R|S

Posted on by Matt Williams

Dark Energy Illuminated By Largest Galactic Map Ten Years In The Making

A section of the 3D map constructed by BOSS. The rectangle on the far left shows a cutout of 1000 sq. degrees in the sky containing nearly 120,000 galaxies, or roughly 10% of the total survey. Credit: Jeremy Tinker/SDSS-III

In 1929, Edwin Hubble forever changed our understanding of the cosmos by showing that the Universe is in a state of expansion. By the 1990s, astronomers determined that the rate at which it is expanding is actually speeding up, which in turn led to the theory of “Dark Energy“. Since that time, astronomers and physicists have sought to determine the existence of this force by measuring the influence it has on the cosmos.

The latest in these efforts comes from the Sloan Digital Sky Survey III (SDSS III), where an international team of researchers have announced that they have finished creating the most precise measurements of the Universe to date. Known as the Baryon Oscillation Spectroscopic Survey (BOSS), their measurements have placed new constraints on the properties of Dark Energy.

The new measurements were presented by Harvard University astronomer Daniel Eisenstein at a recent meeting of the American Astronomical Society. As the director of the Sloan Digital Sky Survey III (SDSS-III), he and his team have spent the past ten years measuring the cosmos and the periodic fluctuations in the density of normal matter to see how galaxies are distributed throughout the Universe.

An illustration of the concept of baryon acoustic oscillations, which are imprinted in the early universe and can still be seen today in galaxy surveys like BOSS (Illustration courtesy of Chris Blake and Sam Moorfield).
An illustration of baryon acoustic oscillations, which are imprinted in the early universe and can still be seen today in galaxy surveys like BOSS. Credit: Chris Blake and Sam Moorfield

And after a decade of research, the BOSS team was able to produce a three-dimensional map of the cosmos that covers more than six billion light-years. And while other recent surveys have looked further afield – up to distances of 9 and 13 billion light years – the BOSS map is unique in that it boasts the highest accuracy of any cosmological map.

In fact, the BOSS team was able to measure the distribution of galaxies in the cosmos, and at a distance of 6 billion light-years, to within an unprecedented 1% margin of error. Determining the nature of cosmic objects at great distances is no easy matter, due the effects of relativity. As Dr. Eisenstein told Universe Today via email:

“Distances are a long-standing challenge in astronomy. Whereas humans often can judge distance because of our binocular vision, galaxies beyond the Milky Way are much too far away to use that. And because galaxies come in a wide range of intrinsic sizes, it is hard to judge their distance. It’s like looking at a far-away mountain; one’s judgement of its distance is tied up with one’s judgement of its height.”

In the past, astronomers have made accurate measurements of objects within the local universe (i.e. planets, neighboring stars, star clusters) by relying on everything from radar to redshift – the degree to which the wavelength of light is shifted towards the red end of the spectrum. However, the greater the distance of an object, the greater the degree of uncertainty.

An artist's concept of the latest, highly accurate measurement of the Universe from BOSS. The spheres show the current size of the "baryon acoustic oscillations" (BAOs) from the early universe, which have helped to set the distribution of galaxies that we see in the universe today. Galaxies have a slight tendency to align along the edges of the spheres — the alignment has been greatly exaggerated in this illustration. BAOs can be used as a "standard ruler" (white line) to measure the distances to all the galaxies in the universe. Credit: Zosia Rostomian, Lawrence Berkeley National Laboratory
An artist’s concept of the latest, highly accurate measurement of the Universe from BOSS. Credit: Zosia Rostomian/Lawrence Berkeley National Laboratory

And until now, only objects that are a few thousand light-years from Earth – i.e. within the Milky Way galaxy – have had their distances measured to within a one-percent margin of error. As the largest of the four projects that make up the Sloan Digital Sky Survey III (SDSS-III), what sets BOSS apart is the fact that it relies primarily on the measurement of what are called “baryon acoustic oscillations” (BAOs).

These are essentially subtle periodic ripples in the distribution of visible baryonic (i.e. normal) matter in the cosmos. As Dr. Daniel Eisenstein explained:

“BOSS measures the expansion of the Universe in two primary ways. The first is by using the baryon acoustic oscillations (hence the name of the survey). Sound waves traveling in the first 400,000 years after the Big Bang create a preferred scale for separations of pairs of galaxies. By measuring this preferred separation in a sample of many galaxies, we can infer the distance to the sample. 

“The second method is to measure how clustering of galaxies differs between pairs oriented along the line of sight compared to transverse to the line of sight. The expansion of the Universe can cause this clustering to be asymmetric if one uses the wrong expansion history when converting redshifts to distance.”

With these new, highly-accurate distance measurements, BOSS astronomers will be able to study the influence of Dark Matter with far greater precision. “Different dark energy models vary in how the acceleration of the expansion of the Universe proceeds over time,” said Eisenstein. “BOSS is measuring the expansion history, which allows us to infer the acceleration rate. We find results that are highly consistent with the predictions of the cosmological constant model, that is, the model in which dark energy has a constant density over time.”

An international team of researchers have produced the largest 3-D map of the universe to date, which validates Einstein's theory of General Relativity. Credit: NAOJ/CFHT/ SDSS
Discerning the large-scale structure of the universe, and the role played by Dark Energy, is key to unlocking its mysteries. Credit: NAOJ/CFHT/ SDSS

In addition to measuring the distribution of normal matter to determine the influence of Dark Energy, the SDSS-III Collaboration is working to map the Milky Way and search for extrasolar planets. The BOSS measurements are detailed in a series of articles that were submitted to journals by the BOSS collaboration last month, all of which are now available online.

And BOSS is not the only effort to understand the large-scale structure of our Universe, and how all its mysterious forces have shaped it. Just last month, Professor Stephen Hawking announced that the COSMOS supercomputing center at Cambridge University would be creating the most detailed 3D map of the Universe to date.

Relying on data obtained by the CMB data obtained by the ESA’s Planck satellite and information from the Dark Energy Survey, they also hope to measure the influence Dark Energy has had on the distribution of matter in our Universe. Who knows? In a few years time, we may very well come to understand how all the fundamental forces governing the Universe work together.

Further Reading: SDSIII

Posted on by Tammy Plotner

The Constellation Boötes

The northern constellation of Bootes, one of the 88 modern constellations recognized by the IAU. Credit: smokymtnastro.org

Welcome back to Constellation Friday! Today, in honor of our dear friend and contributor, Tammy Plotner, we examine the Bootes constellation. Enjoy!

In the 2nd century CE, Greek-Egyptian astronomer Claudius Ptolemaeus (aka. Ptolemy) compiled a list of the then-known 48 constellations. Until the development of modern astronomy, his treatise (known as the Almagest) would serve as the authoritative source of astronomy. This list has since come to be expanded to include the 88 constellation that are recognized by the International Astronomical Union (IAU) today.

The constellation Boötes (pronounced Bu-Oh-Tays) is one of these constellations, and was also among those listed in the Almagest. It is frequently called the “Watcher of the Bear”, guarding over the northern constellations of both Ursa Major and Ursa Minor (the Greater and Lesser Bears). It is bordered by Canes Venatici, Coma Berenices, Corona Borealis, Draco, Hercules, Serpens Caput, Virgo and Ursa Major.

Name and Meaning:

According to myth, Boötes is credited for inventing the plough, which prompted the goddess Ceres – a goddess of agriculture, grain crops, fertility and motherly love – to place him in the heavens. There are also versions where Bootes represents a form of Atlas, holding up the weight of the world as it turns on its axis (yet another of Hercules’ labors).

Most commonly, Boötes is taken to represent Arcas, the son of Zeus and Callisto. In this source, Arcas was brought up by Callisto father, the Arcadian king Lycaon. One day, Lycaon decided to test Zeus by serving him his own son for a meal. Zeus saw through Lycaon’s intentions and transformed the king into a wolf, killed his sons, and brought Arcas back to life.

Boötes as depicted in Urania's Mirror, a set of constellation cards published in London c.1825. In his left hand he holds his hunting dogs, Canes Venatici. Below them is the constellation Coma Berenices. Above the head of Boötes is Quadrans Muralis, now obsolete, but which lives on as the name of the early January Quadrantid meteor shower. Mons Mænalus can be seen at his feet. Credit: Wikipedia Commons/Sidney Hall
Boötes as depicted in Urania’s Mirror, a set of constellation cards published in London c.1825. Credit: Wikipedia Commons/Sidney

Having heard of her husband’s infidelity, Zeus’ wife Hera transformed Callisto into a bear. For years, she roamed the woods until she met her son, who was now grown up. Arcas didn’t recognize his mother and began to chase her. To avoid a tragic end, Zeus intervened by placing them both in the sky, where Callisto became Ursa Major (aka. The Big Dipper, or “Great Bear”) and Arcas became Boötes.

In another story, Boötes is taken to represent Icarius, a grape grower who was given the secret of wine-making by Dionysus. Icarius used this to create a wonderful wine that he shared with all his neighbors. After overindulging, they woke up the next day with terrible hangovers and believed Icarius had tried to poison them. They killed him in his sleep, and a saddened Dionysus placed his friend among the stars.

Notable Features:

Bootes contains the third brightest star in the night sky – Arcturus (aka. alpha Boötis) – whose Greek name “Arktos” also means “bear”, and is associated with all things northern (including the aurora). Arcturus is quite important, being a type K1.5 IIIpe red giant star. The letters “pe” stand for “peculiar emission,” which indicates the spectrum of the star is unusual and full of emission lines. This is not uncommon in red giants, but Arcturus is particularly strong.

The Bootes contellation. Credit: IAU/Sky and Telescope
The location of the Bootes contellation. Credit: IAU/Sky and Telescope

Arcturus is about 110 times more luminous than our nearest star, but the total power output is about 180 times that of the Sun (when infrared radiation is considered). Arcturus is also notable for its high proper motion, larger than any first magnitude star in the stellar neighborhood other than Alpha Centauri. It is now almost at its closest and is moving rapidly (122 km/s) relative to the Solar System.

Arcturus is also thought to be an old disk star, and appears to be moving with a group of 52 others of its type. Its mass is hard to determine exactly, but it may have the same mass as Sol, or perhaps 1.5 times as much. Arcturus may also be older than the Sun, and much like what the Sun will be in its Red Giant Phase.

Arcturus achieved fame when its light was used to open the 1933 Chicago World’s Fair. The star was chosen because it was thought that light from the star had started its journey at about the same time of the previous Chicago World’s Fair (1893). Technically the star is 36.7 light years away, so the light would have started its journey in 1896. Arcturus’ light was still focused onto a cell that powered the switch for the lights that eventually shined so bright that Arcturus was no longer visible.

Arcturus, along with its neighboring stars, also form the curious “Colonial Viper” formation, a triangular asterism invented by dedicated SkyWatcher, Ed Murray. It is so-named because it resembles a Colonial Viper being launched from a tube on the TV series Battlestar Galactica. The “Launch Tube” is formed by the intersection of Arcturus, Alphekka (Alpha Corona Borealis) and Gamma Bootis, while Izar (Epsilon Bootes) is the Viper.

A Colonial Viper leaving the Launch Tube aboard the Battlestar Galactica. Credit: battlestararies-bsr26.net
A Colonial Viper leaving the Launch Tube aboard the Battlestar Galactica. Credit: battlestararies-bsr26.net

Other notable stars include Nekkar (Beta Boötis), a yellow G-type giant that is 219 light years from Earth. It is a flare star, which is a type of variable star that shows dramatic increases in luminosity for a few minutes. The name Nekkar derives from the Arabic word for “cattle driver”. Then there’s Seginus (Gamma Boötis), a Delta-Scuti type variable star that is approximately 85 light years from Earth. It shows variations in its brightness due to both radial and non-radial pulsations on its surface.

Izar (Epislon Boötis) is a binary star located approximately 300 light years away which consists of a bright orange giant and a smaller and fainter main sequence star. Epsilon Boötis is also sometimes knows as Pulcherrima, which means “the lovieliest” in Latin. The name Izar comes from the Arabic word for “veil.” The star’s other traditional names are Mirak (“the loins” in Arabic) and Mizar.

Muphrid (Eta Boötis) is a spectroscopic binary star that is 37 light years from Earth and close to Arcturus in the sky. The star’s traditional name is Muphrid, derived from the Arabic phrase for “the single one of the lancer.” It belongs to the spectral class G0 IV and has a significant excess of elements heavier than hydrogen.

Boötes is also home to many Deep Sky Objects. This includes the Boötes void (aka. the Great Void, the Supervoid). This sphere-shaped region of the sky is almost 250 million light years in diameter and contains 60 galaxies. The void was originally discovered by Robert P. Kirshner – a Harvard College Professor of Astronomy – in 1981, as part of a survey of galactic redshifts.

The very loose globular cluster NGC 5466, Credit: NASA, ESA
The very loose globular cluster NGC 5466 located in the Boots consetllation, Credit: NASA, ESA/Wikisky

Then there is the Boötes Dwarf Galaxy (Boötes I), a dwarf spheroidal galaxy located approximately 197,000 light years from Earth that measures about 720 light years across. It was only discovered in 2006, owing to the fact that it is one of the faintest galaxies known (with an absolute magnitude of -5.8 and apparent magnitude of 13.1). Boötes I orbits the Milky Way and is believed to be tidally disrupted by its gravity, as evidenced by its shape.

And there’s also NGC 5466, a globular cluster approximately 51,800 light years from Earth and 52,800 light years from the Galactic center. The cluster was first discovered by the German-born British astronomer William Herschel in 1784. It is believed that this cluster is the source of a star stream called the 45 Degree Tidal Stream, which was discovered in 2006.

History of Observation:

The earliest recorded mentions of the stars associated with Boötes come from ancient Babylonia, where it was listed as SHU.PA. These stars were apparently depicted as the god Enlil, who was the leader of the Babylonian pantheon and special patron of farmers. It is likely that this is the source of mythological representations of Bootes as “the ploughman” in Greco-Roman astronomy.

The name Boötes was first used by Homer in The Odyssey as a celestial reference point for navigation. The name literally means “ox-driver” or “herdsman”, and the ancient Greeks saw the asterism now called the “Big Dipper” or “Plough” as a cart with oxen. His dogs, Chara and Asterion, were represented by the constellation of Canes Venatici (the Hunting Dogs) who drove the oxen on and kept the wheels of the sky turning.

Phecda
The Big Dipper, the asterism that neighbors the Bootes constellation. Credit: Jerry Lodriguss

In traditional Chinese astronomy, many of the stars in Boötes were associated with different Chinese constellations. Arcturus was one of the most prominent, variously designated as the celestial king’s throne (Tian Wang) or the Blue Dragon’s horn (Daijiao). Arcturus was also very important in Chinese celestial mythology because it is the brightest star in the northern sky, and marked the beginning of the lunar calendar.

Flanking Daijiao were the constellations of Yousheti on the right and Zuosheti on the left, which represented the companions that orchestrated the seasons. Dixi, the Emperor’s ceremonial banquet mat, was north of Arcturus. Another northern constellation was Qigong, the Seven Dukes, which was mostly across the Boötes-Hercules border.

The other Chinese constellations made up of the stars of Boötes existed in the modern constellation’s north. These are all representations of weapons –  Tianqiang, the spear; Genghe, variously representing a lance or shield; Xuange, the halberd; and Zhaoyao, either the sword or the spear.

Finding Bootes:

Bootes can be found south of Ursa Major, just off the handle of the Big Dipper. Because the Big Dipper is easy for most observers to find, the handle is used to point to other important stars. Bootes’ brightest star, Arcturus, is also part of a mnemonic device used to orient people, which goes: “Arc to Arcturus, speed on to Spica.” This means you follow the curve in the Dipper’s handle away from Ursa Major until you run into Arcturus. The other star – Spica – is part of the neighboring Virgo constellation.

Arcturus, the brightest star in the Boötes constellation. Credit: astropixels.com
Arcturus, the brightest star in the Boötes constellation. Credit: astropixels.com

For those using binoculars, check out Tau Bootis, a yellow-white dwarf approximately 51 light-years from Earth. It is a binary star system, with the secondary star being a red dwarf. In 1999, an extrasolar planet was confirmed to be orbiting the primary star by a team of astronomers led by Geoff Marcy and R. Paul Butler. Maybe you’d like to look at long term variable star R Boötis? It ranges from 6.2 to 13.1 every 223.4 days.

For those using telescopes, there are plenty of excellent binary star systems to be seen. Pi Boötis is located approximately 317 light years from our solar system and the primary component, P¹ Boötis, is a blue-white B-type main sequence dwarf with an apparent magnitude of +4.49. It’s companion, P² Boötis, is a white A-type main sequence dwarf with an apparent magnitude of +5.88.

Now try looking at Xi Boötis, a binary star system which lies 21.8 light years away. The primary star, Xi Boötis A, is a BY Draconis variable, yellow G-type main sequence dwarf with an apparent magnitude that varies from +4.52 to +4.67. with a period just over 10 days long. Small velocity changes in the orbit of the companion star, Xi Boötis B – an orange K-type main sequence dwarf – indicate the presence of a small companion with less than nine times the mass of Jupiter.

The AB binary can be resolved even through smaller telescopes. The primary star (A) has been identified as a candidate for possessing a Kuiper-like belt, based on infrared observations. The estimated minimum mass of this dust disk is 2.4 times the mass of the Earth’s Moon.

The location of Mu Bootis (Alkalurops) in the Bootes constllation. Credit: universeguide.com
The location of Mu Bootis (Alkalurops) in the Bootes constellation. Credit: universeguide.com

Then there’s the triple system, Mu Boötis. The primary component, Mu¹ Boötis, is a yellow-white F-type sub giant with an apparent magnitude of +4.31. Separated from the primary by 108 arc seconds is the binary star Mu² Boötis, which has a combined spectral type of G1V and a combined brightness of +6.51 magnitudes. The components of Mu² Boötis have apparent magnitudes of +7.2 and +7.8 and are separated by 2.2 arc seconds.

They complete one orbit about their common center of mass every 260 years. How about colorful yellow and blue Kappa Boötis? Kappa2 Boötis is classified as a Delta Scuti type variable star and its brightness varies from magnitude +4.50 to +4.58 with a period of 1.83 hours. The companion star, Kappa¹ Boötis, has magnitude +6.58 and spectral class F1V.

For deep sky observers with large telescopes, try checking out the globular cluster NGC 5466, which is about a fist’s width north of Arcturus. This class XII, 9th magnitude globular was discovered in 1784 by Sir William Herschel and presents an nice challenge for experienced stargazers and amateur astronomers.

Or try compact spiral galaxy NGC 5248. It’s about a fist width south of Arcturus and about a finger width southwest. It’s part of the Virgo cluster of galaxies and could be as far as 50 million light years away. It’s another great grand design spiral which shows spiral galaxy structure when viewed in long exposure photographs. You can mark it on your list as Caldwell 45.

The NGC 5248 spiral galaxy, as imaged with a 32-inch telescope. Credit and Copyright: Adam Block/Mount Lemmon SkyCenter/University of Arizona
The NGC 5248 spiral galaxy, as imaged with a 32-inch telescope. Credit and Copyright: Adam Block/Mount Lemmon SkyCenter/University of Arizona

But if you’d just like to have some fun, then why not try picking out the aforementioned “Colonial Viper and Launch Tube” asterism. If you’re a longstanding Battlestar Galactica fan, then you’ll recognize this ultra-cool spaceship as it sits in its triangular shaped launch tube. To find it, just draw a line between Arcturus, Alphekka (Alpha Corona Borealis) and Gamma Bootis which make up the “Launch Tube”, while Izar (Epsilon Bootes) is the Viper.

We have written many interesting articles about the constellation here at Universe Today. Here is What Are The Constellations?, What Is The Zodiac?, and Zodiac Signs And Their Dates.

Be sure to check out The Messier Catalog while you’re at it!

For more information, check out the IAUs list of Constellations, and the Students for the Exploration and Development of Space page on Bootes and Constellation Families.

Posted on by Matt Williams

Lightweight Telescopes In CubeSats Using Carbon Nanotube Mirrors

A team of NASA engineers has fashioned the world's first telescope mirrors made from carbon nanotubes. Credit: NASA

Ever since they were first produced, carbon nanotubes have managed to set off a flurry excitement in the scientific community. With applications ranging from water treatment and electronics, to biomedicine and construction, this should come as no surprise. But a team of NASA engineers from the Goddard Space Flight Center in Greenbelt, Maryland, has pioneered the use of carbon nanotubes for yet another purpose – space-based telescopes.

Using carbon nanotubes, the Goddard team – which is led by Dr. Theodor Kostiuk of NASA’s Planetary Systems Laboratory and Solar System Exploration Division – have created a revolutionary new type of telescope mirror. These mirrors will be deployed as part of a CubeSat, one which may represent a new breed of low-cost, highly effective space-based telescopes.

This latest innovation also takes advantage of another field that has seen a lot of development of late. CubeSats, like other small satellites, have been playing an increasingly important role in recent years. Unlike the larger, bulkier satellites of yesteryear, miniature satellites are a low-cost platform for conducting space missions and scientific research.

John Kolasinski (left), Ted Kostiuk (center), and Tilak Hewagama (right) hold mirrors made of carbon nanotubes in an epoxy resin. The mirror is being tested for potential use in a lightweight telescope specifically for CubeSat scientific investigations. Credits: NASA/W. Hrybyk
Dr. Ted Kostiuk (center), flanked by John Kolasinski (left), and Tilak Hewagama (right), holding mirrors made of carbon nanotubes in an epoxy resin. Credit: NASA/W. Hrybyk

Beyond federal space agencies like NASA, they also offer private business and research institutions the opportunity to conduct communications, research and observation from space. On top of that, they are also a low-cost way to engage students in all phases of satellite construction, deployment, and space-based research.

Granted, missions that rely on miniature satellites are not likely to generate the same amount of interest or scientific research as large-scale operations like the Juno mission or the New Horizons space probe. But they can provide vital information as part of larger missions, or work in groups to gather greater amounts of data.

With the help of funding from Goddard’s Internal Research and Development program, the team created a laboratory optical bench made of regular off-the-shelf components to test the telescope’s overall design. This bench consists of a series of miniature spectrometers tuned to the ultraviolet,  visible, and near-infrared wavelengths, which are connected to the focused beam of the nanotube mirrors via an optic cable.

Using this bench, the team is testing the optical mirrors, seeing how they stand up to different wavelengths of light. Peter Chen – the president of Lightweight Telescopes a Maryland-based company – is one of the contractors working with the Goddard team to create the CubeSat telescope. As he was quoted as saying by a recent NASA press release:

“No one has been able to make a mirror using a carbon-nanotube resin. This is a unique technology currently available only at Goddard. The technology is too new to fly in space, and first must go through the various levels of technological advancement. But this is what my Goddard colleagues (Kostiuk, Tilak Hewagama, and John Kolasinski) are trying to accomplish through the CubeSat program.

The laboratory breadboard that is being used to test a conceptual telescope for use on CubeSat missions. Credits: NASA/W. Hrybyk
The laboratory breadboard that is being used to test a conceptual telescope for use on CubeSat missions. Credits: NASA/W. Hrybyk

Unlike other mirrors, the one created by Dr. Kostiuk’s team was fabricated out of carbon nanotubes embedded in an epoxy resin. Naturally, carbon nanotubes offer a wide range of advantages, not the least of which are structural strength, unique electrical properties, and efficient conduction of heat. But the Goddard team also chose this material for their lenses because it offers a lightweight, highly stable and easily reproducible option for creating telescope mirrors.

What’s more, mirrors made of carbon-nanotubes do not require polishing, which is a time-consuming and expensive process when it comes to space-based telescopes. The team hopes that this new method will prove useful in creating a new class of low-cost, CubeSat space telescopes, as well as helping to reduce costs when it comes to larger ground-based and space-based telescopes.

Such mirrors would be especially useful in telescopes that use multiple mirror segments (like the Keck Observatory at Mauna Kea and the James Webb Space Telescope). Such mirrors would be a real cost-cutter since they can be easily produced and would eliminate the need for expensive polishing and grinding.

Other potential applications include deep-space communications, improved electronics, and structural materials for spacecraft. Currently, the production of carbon nanotubes is quite limited. But as it becomes more widespread, we can expect this miracle material to be making its way into all aspects of space exploration and research.

Further Reading: NASA

Posted on by Tammy Plotner

What is Galileo’s Telescope?

The original Galileo telescope, which is preserved today at the Museo Galileo in Italy. Credit: museogalileo.it

In 1610, Italian astronomer Galileo Galilei looked up at the heavens using a telescope of his making. And what he saw would forever revolutionize the field of astronomy, our understanding of the Universe, and our place in it. Centuries later, Galileo’s is still held in such high esteem; not only for the groundbreaking research he conducted, but because of his immense ingenuity in developing his own research tools.

And at the center of it all is Galileo’s famous telescope, which still inspires curiosity centuries later. How exactly did he invent it. How exactly was it an improvement on then-current designs? What exactly did he see with it when he looked up at the night sky? And what has become of it today? Luckily, all of these are questions we are able to answer.

Description:

Galileo’s telescope was the prototype of the modern day refractor telescope. As you can see from this diagram below, which is taken from Galileo’s own work – Sidereus Nuncius (“The Starry Messenger”) – it was a simple arrangement of lenses that first began with optician’s glass fixed to either end of a hollow cylinder.

Diagram of Galileo's telescope, taken from Sidereus Nuncius. Credit: hps.cam.ac.uk
Diagram of Galileo’s refractor telescope, taken from Sidereus Nuncius (1610). Credit: hps.cam.ac.uk

Galileo had no diagrams to work from, and instead relied on his own system of trial and error to achieve the proper placement of the lenses. In Galileo’s telescope the objective lens was convex and the eye lens was concave (today’s telescopes make use of two convex lenses). Galileo knew that light from an object placed at a distance from a convex lens created an identical image on the opposite side of the lens.

He also knew that if he used a concave lens, the object would appear on the same side of the lens where the object was located. If moved at a distance, it appeared larger than the object. It took a lot of work and different arrangements to get the lens the proper sizes and distances apart, but Galileo’s telescope remained the most powerful and accurately built for a great many years.

History of Galileo’s Telescope:

Naturally, Galileo’s telescope had some historical antecedents. In the late summer of 1608, a new invention was all the rage in Europe – the spyglass. These low power telescopes were likely made by almost all advanced opticians, but the very first was credited to Hans Lippershey of Holland. These primitive telescopes only magnified the view a few times over.

Much like our modern times, the manufacturers were quickly trying to corner the market with their invention. But Galileo Galilei’s friends convinced his own government to wait – sure that he could improve the design. When Galileo heard of this new optical instrument he set about engineering and making improved versions, with higher magnification.

Galileo Galilei showing the Doge of Venice how to use the telescope by Giuseppe Bertini (1858). Credit: gabrielevanin.it
Galileo Galilei showing the Doge of Venice how to use the telescope by Giuseppe Bertini (1858). Credit: gabrielevanin.it

Galileo’s telescope was similar to how a pair of opera glasses work – a simple arrangement of glass lenses to magnify objects. His first versions only improved the view to the eighth power, but Galileo’s telescope steadily improved. Within a few years, he began grinding his own lenses and changing his arrays. Galileo’s telescope was now capable of magnifying normal vision by a factor of 10, but it had a very narrow field of view.

However, this limited ability didn’t stop Galileo from using his telescope to make some amazing observations of the heavens. And what he saw, and recorded for posterity, was nothing short of game-changing.

What Galileo Observed:

One fine Fall evening, Galileo pointed his telescope towards the one thing that people thought was perfectly smooth and as polished as a gemstone – the Moon. Imagine his surprise when found that it, in his own words, was “uneven, rough, full of cavities and prominences.” Galileo’s telescope had its flaws, such as a narrow field of view that could only show about one quarter of the lunar disk without repositioning.

Nevertheless, a revolution in astronomy had begun! Months passed, and Galileo’s telescope improved. On January 7th, 1610, he turned his new 30 power telescope towards Jupiter, and found three small, bright “stars” near the planet. One was off to the west, the other two were to the east, and all three were in a straight line. The following evening, Galileo once again took a look at Jupiter, and found that all three of the “stars” were now west of the planet – still in a straight line!

Cardinal Bellarmine had written in 1615 that the Copernican system could not be defended without "a true physical demonstration that the sun does not circle the earth but the earth circles the sun". Galileo considered his theory of the tides to provide the required physical proof of the motion of the earth. This theory was so important to him that he originally intended to entitle his Dialogue on the Two Chief World Systems the Dialogue on the Ebb and Flow of the Sea. For Galileo, the tides were caused by the sloshing back and forth of water in the seas as a point on the Earth's surface sped up and slowed down because of the Earth's rotation on its axis and revolution around the Sun. He circulated his first account of the tides in 1616, addressed to Cardinal Orsini. His theory gave the first insight into the importance of the shapes of ocean basins in the size and timing of tides; he correctly accounted, for instance, for the negligible tides halfway along the Adriatic Sea compared to those at the ends. As a general account of the cause of tides, however, his theory was a failure. If this theory were correct, there would be only one high tide per day. Galileo and his contemporaries were aware of this inadequacy because there are two daily high tides at Venice instead of one, about twelve hours apart. Galileo dismissed this anomaly as the result of several secondary causes including the shape of the sea, its depth, and other factors. Against the assertion that Galileo was deceptive in making these arguments, Albert Einstein expressed the opinion that Galileo developed his "fascinating arguments" and accepted them uncritically out of a desire for physical proof of the motion of the Earth. Galileo dismissed the idea, held by his contemporary Johannes Kepler, that the moon caused the tides. He also refused to accept Kepler's elliptical orbits of the planets, considering the circle the "perfect" shape for planetary orbits.Cardinal Bellarmine had written in 1615 that the Copernican system could not be defended without "a true physical demonstration that the sun does not circle the earth but the earth circles the sun". Galileo considered his theory of the tides to provide the required physical proof of the motion of the earth. This theory was so important to him that he originally intended to entitle his Dialogue on the Two Chief World Systems the Dialogue on the Ebb and Flow of the Sea. For Galileo, the tides were caused by the sloshing back and forth of water in the seas as a point on the Earth's surface sped up and slowed down because of the Earth's rotation on its axis and revolution around the Sun. He circulated his first account of the tides in 1616, addressed to Cardinal Orsini. His theory gave the first insight into the importance of the shapes of ocean basins in the size and timing of tides; he correctly accounted, for instance, for the negligible tides halfway along the Adriatic Sea compared to those at the ends. As a general account of the cause of tides, however, his theory was a failure. If this theory were correct, there would be only one high tide per day. Galileo and his contemporaries were aware of this inadequacy because there are two daily high tides at Venice instead of one, about twelve hours apart. Galileo dismissed this anomaly as the result of several secondary causes including the shape of the sea, its depth, and other factors. Against the assertion that Galileo was deceptive in making these arguments, Albert Einstein expressed the opinion that Galileo developed his "fascinating arguments" and accepted them uncritically out of a desire for physical proof of the motion of the Earth. Galileo dismissed the idea, held by his contemporary Johannes Kepler, that the moon caused the tides. He also refused to accept Kepler's elliptical orbits of the planets, considering the circle the "perfect" shape for planetary orbits.
Galileo’s Sidereus Nuncius (“Starry Messenger”) shared the discoveries he made of Jupiter with his telescope. Credit and Copyright: brunelleschi.imss.fi.it

And there were more discoveries awaiting Galileo’s telescope: the appearance of bumps next to the planet Saturn (the edges of Saturn’s rings), spots on the Sun’s surface (aka. Sunspots), and seeing Venus change from a full disk to a slender crescent. Galileo Galilei published all of these findings in a small book titled Sidereus Nuncius (“The Starry Messenger”) in 1610.

While Galileo was not the first astronomer to point a telescope towards the heavens, he was the first to do so scientifically and methodically. Not only that, but the comprehensive notes he took on his observations, and the publication of his discoveries, would have a revolutionary impact on astronomy and many other fields of science.

Galileo’s Telescope Today:

Today, over 400 years later, Galileo’s Telescope still survives under the constant care of the Istituto e Museo di Storia della Scienza (renamed the Museo Galileo in 2010) in Italy. The Museum holds exhibitions on Galileo’s telescope and the observations he made with it. The displays consist of these rare and precious instruments – including the objective lens created by the master and the only two existing telescopes built by Galileo himself.

Thanks to Galileo’s careful record keeping, craftsmen around the world have recreated Galileo’s telescope for museums and replicas are now sold for amateurs and collectors as well. Despite the fact that astronomers now have telescopes of immense power at their disposal, many still prefer to go the DIY route, just like Galileo!

A replica of the earliest surviving telescope attributed to Galileo Galilei, on display at the Griffith Observatory. Credit: Wikipedia Commons/Mike Dunn
A replica of the earliest surviving telescope attributed to Galileo Galilei, on display at the Griffith Observatory. Credit: Wikipedia Commons/Mike Dunn

Few scientists and astronomers have had the same impact Galileo had. Even fewer are regarded as pioneers in the sciences, or revolutionary thinkers who forever changed humanity’s perception of the heavens and their place within it. Little wonder then why his most prized instrument is kept so well preserved, and is still the subject of study over four centuries later.

We have written many interesting articles on Galileo here at Universe Today. Here’s

Astronomy Cast also has an interesting episode on telescope making – Episode 327: Telescope Making, Part I

For more information, be sure to check out the Museo Galileo‘s website.

Posted on by Matt Williams

Where is Earth in the Milky Way?

Artist's impression of The Milky Way Galaxy. Based on current estimates and exoplanet data, it is believed that there could be tens of billions of habitable planets out there. Credit: NASA

For thousand of years, astronomers and astrologers believed that the Earth was at the center of our Universe. This perception was due in part to the fact that Earth-based observations were complicated by the fact that the Earth is embedded in the Solar System. It was only after many centuries of continued observation and calculations that we discovered that the Earth (and all other bodies in the Solar System) actually orbits the Sun.

Much the same is true about our Solar System’s position within the Milky Way. In truth, we’ve only been aware of the fact that we are part of a much larger disk of stars that orbits a common center for about a century. And given that we are embedded within it, it has been historically difficult to ascertain our exact position. But thanks to ongoing efforts, astronomers now know where our Sun resides in the galaxy.

Size of the Milky Way:

For starters, the Milky Way is really, really big! Not only does it measure some 100,000–120,000 light-years in diameter and about 1,000 light-years thick, but up to 400 billion stars are located within it (though some estimates think there are even more). Since one light year is about 9.5 x 1012 km (9.5 trillion km) long, the diameter of the Milky Way galaxy is about 9.5 x 1017 to 11.4 x 1017 km, or 9,500 to 11,400 quadrillion km.

It became its current size and shape by eating up other galaxies, and is still doing so today. In fact, the Canis Major Dwarf Galaxy is the closest galaxy to the Milky Way because its stars are currently being added to the Milky Way’s disk. And our galaxy has consumed others in its long history, such as the Sagittarius Dwarf Galaxy.

And yet, our galaxy is only a middle-weight when compared to other galaxies in the local Universe. Andromeda, the closest major galaxy to our own, is about twice as large as our own. It measures 220,000 light years in diameter, and has an estimated 400-800 billion stars within it.

Structure of the Milky Way:

If you could travel outside the galaxy and look down on it from above, you’d see that the Milky Way is a barred spiral galaxy. For the longest time, the Milky Way was thought to have 4 spiral arms, but newer surveys have determined that it actually seems to just have two spiral arms, called Scutum–Centaurus and Carina–Sagittarius.

The spiral arms are formed from density waves that orbit around the Milky Way – i.e. stars and clouds of gas clustered together. As these density waves move through an area, they compress the gas and dust, leading to a period of active star formation for the region. However, the existence of these arms has been determined from observing parts of the Milky Way – as well as other galaxies in our universe.

The Milky Way's basic structure is believed to involve two main spiral arms emanating from opposite ends of an elongated central bar. But only parts of the arms can be seen - gray segments indicate portions not yet detected. Other known spiral arm segments--including the Sun's own spur--are omitted for clarity. Credit: T. Dame
The Milky Way’s basic structure is believed to involve two main spiral arms emanating from opposite ends of an elongated central bar. Credit: T. Dame

In truth, all the pictures that depict our galaxy are either artist’s renditions or pictures of other spiral galaxies, and not the result of direct observation of the whole. Until recently, it was very difficult for scientists to gauge what the Milky Way really looks like, mainly because we’re inside it. It has only been through decades of observation, reconstruction and comparison to other galaxies that they have been to get a clear picture of what the Milky Way looks like from the outside.

From ongoing surveys of the night sky with ground-based telescopes, and more recent missions involving space telescopes, astronomers now estimate that there are between 100 and 400 billion stars in the Milky Way. They also think that each star has at least one planet, which means there are likely to be hundreds of billions of planets in the Milky Way – billions of which are believed to be the size and mass of the Earth.

As noted, much of the Milky Way’s arms is made up of dust and gas. This matter makes up a whopping 10-15% of all the “luminous matter” (i.e. that which is visible) in our galaxy, with the remainder being the stars. Our galaxy is roughly 100,000 light years across, and we can only see about 6,000 light years into the disk in the visible spectrum.

Still, when light pollution is not significant, the dusty ring of the Milky Way can be discerned in the night sky. What’s more, infrared astronomy and viewing the Universe in other, non-visible wavelengths has allowed astronomers to be able to see more of it.

The Milky Way, like all galaxies, is also surrounded by a vast halo of dark matter, which accounts for some 90% of its mass. Nobody knows precisely what dark matter is, but its mass has been inferred by observations of how fast the galaxy rotates and other general behaviors. More importantly, it is believed that this mass helps keep the galaxy from tearing itself apart as it rotates.

The Solar System:

The Solar System (and Earth) is located about 25,000 light-years to the galactic center and 25,000 light-years away from the rim. So basically, if you were to think of the Milky Way as a big record, we would be the spot that’s roughly halfway between the center and the edge.

Astronomers have agreed that the Milky Way probably has two major spiral arms – Perseus arm and the Scutum-Centaurus arm – with several smaller arms and spurs. The Solar System is located in a region in between the two arms called the Orion-Cygnus arm. This arm measures 3,500 light-years across and is 10,000 light-years in length, where it breaks off from the Sagittarius Arm.

our location in the Orion Spur of the Milky Way galaxy. image credit: Roberto Mura/Public Domain
The location of our Solar Systemin the Orion Spur of the Milky Way galaxy. Credit: Roberto Mura/Public Domain

The fact that the Milky Way divides the night sky into two roughly equal hemispheres indicates that the Solar System lies near the galactic plane. The Milky Way has a relatively low surface brightness due to the gases and dust that fills the galactic disk. That prevents us from seeing the bright galactic center or from observing clearly what is on the other side of it.

You might be surprised to learn that it takes the Sun 250 million years to complete one rotation around the Milky Way – this is what is known as a “Galactic Year” or “Cosmic Year”. The last time the Solar System was in this position in the Milky Way, there were still dinosaurs on Earth. The next time, who knows? Humanity might be extinct, or it might have evolved into something else entirely.

As you can see, the Milky Way alone is a very big place. And discerning our location within it has been no simple task. And as our knowledge of the Universe has expanded, we’ve come to learn two things. Not only is the Universe much larger than we could have ever imagined, but our place within in continues to shrink! Our Solar System, it seems, is both insignificant in the grand scheme of things, but also extremely precious!

We have written many articles about the Milky Way for Universe Today. Here’s 10 Interesting Facts about the Milky Way, How Big is the Milky Way?, What is the Closest Galaxy to the Milky Way?, and How Many Stars Are There in the Milky Way?

If you’d like more info on the Milky Way, check out Hubblesite’s News Releases on Galaxies, and here’s NASA’s Science Page on Galaxies.

We’ve also recorded an episode of Astronomy Cast all about the Milky Way. Listen here, Episode 99: The Milky Way.

Posted on by Matt Williams

ESA Discovers Where All The Missing Socks Have Been Going

earth's atmosphere has an ozone hole (not seen here)
Earth’s atmosphere seen from space. The top layer of the stratosphere is the ozone layer, which protects us from harmful solar UV. Scientists are tracking the ozone hole over the Antarctic. Credit: NASA

We here at Earth are fortunate that we have a viable atmosphere, one that is protected by Earth’s magnetosphere. Without this protective envelope, life on the surface would be bombarded by harmful radiation emanating from the Sun. However, Earth’s upper atmosphere is still slowly leaking, with about 90 tonnes of material a day escaping from the upper atmosphere and streaming into space.

And although astronomers have been investigating this leakage for some time, there are still many unanswered questions. For example, how much material is being lost to space, what kinds, and how does this interact with solar wind to influence our magnetic environment? Such has been the purpose of the European Space Agency’s Cluster project, a series of four identical spacecraft that have been measuring Earth’s magnetic environment for the past 15 years.

Understanding our atmosphere’s interaction with solar wind first requires that we understand how Earth’s magnetic field works. For starters, it extends from the interior of our planet (and is believed to be the result of a dynamo effect in the core), and reaches all the way out into space. This region of space, which our magnetic field exerts influence over, is known as the magnetosphere.

The four Cluster spacecraft crossing the northern cusp of Earth's magnetosphere. Credit: ESA/AOES Medialab
The four Cluster spacecraft crossing the northern cusp of Earth’s magnetosphere. Credit: ESA/AOES Medialab

The inner portion of this magnetosphere is called the plasmasphere, a donut-shaped region which extends to a distance of about 20,000 km from the Earth and co-rotates with it. The magnetosphere is also flooded with charged particles and ions that get trapped inside, and then are sent bouncing back and forth along the region’s field lines.

At its forward, Sun-facing edge, the magnetosphere meets the solar wind – a stream of charged particles flowing from the Sun into space. The spot where they make contact is known as the “Bow Shock”, which is so-named because its magnetic field lines force solar wind to take on the shape of a bow as they pass over and around us.

As the solar wind passes over Earth’s magnetosphere, it comes together again behind our planet to form a magnetotail – an elongated tube which contains trapped sheets of plasma and interacting field lines. Without this protective envelope, Earth’s atmosphere would have been slowly stripped away billions of years ago, a fate that is now believed to have befallen Mars.

That being said, Earth’s magnetic field is not exactly hermetically sealed. For example, at our planet’s poles, the field lines are open, which allows solar particles to enter and fill our magnetosphere with energetic particles. This process is what is responsible for Aurora Borealis and Aurora Australis (aka. the Northern and Southern Lights).

An illustration showing the natural barrier Earth gives us against solar radiation. Credit: NASA.
An illustration showing the natural barrier Earth gives us against solar radiation. Credit: NASA.

At the same time, particles from Earth’s upper atmosphere (the ionosphere) can escape the same way, traveling up through the poles and being lost to space. Despite learning much about Earth’s magnetic fields and how plasma is formed through its interaction with various particles, much about the whole process has been unclear until quite recently.

As Arnaud Masson, ESA’s Deputy Project Scientist for the Cluster mission stated in an ESA press release:

“The question of plasma transport and atmospheric loss is relevant for both planets and stars, and is an incredibly fascinating and important topic. Understanding how atmospheric matter escapes is crucial to understanding how life can develop on a planet. The interaction between incoming and outgoing material in Earth’s magnetosphere is a hot topic at the moment; where exactly is this stuff coming from? How did it enter our patch of space?“

Given that our atmosphere contains 5 quadrillion tons of matter (that’s 5 x 1015, or 5,000,000 billion tons), a loss of 90 tons a day doesn’t amount to much. However, this number does not include the mass of “cold ions” that are regularly being added. This term is typically used to described the hydrogen ions that we now know are being lost to the magnetosphere on a regular basis (along with oxygen and helium ions).

Since hydrogen requires less energy to escape our atmosphere, the ions that are created once this hydrogen becomes part of the plasmasphere also have low energy. As a result, they have been very difficult to detect in the past. What’s more, scientists have only known about this flow of oxygen, hydrogen and helium ions – which come from the Earth’s polar regions and replenish plasma in the magnetosphere – for a few decades.

Illustration of ions flowing out from the polar cap towards the magnetotail. Credit: ESA - C. Carreau
Illustration of ions flowing out from the polar cap towards the magnetotail. Credit: ESA – C. Carreau

Prior to this, scientists believed that solar particles alone were responsible for plasma in Earth’s magnetosphere. But in more recent years, they have come to understand that two other sources contribute to the plasmasphere. The first are sporadic “plumes” of plasma that grow within the plasmasphere and travel outwards towards the edge of the magnetosphere, where they interact with solar wind plasma coming the other way.

The other source? The aforementioned atmospheric leakage. Whereas this consists of abundant oxygen, helium and hydrogen ions, the cold hydrogen ions appear to play the most important role. Not only do they constitute a significant amount of matter lost to space, and may play a key role in shaping our magnetic environment. What’s more, most of the satellites currently orbiting Earth are unable to detect the cold ions being added to the mix, something which Cluster is able to do.

In 2009 and in 2013, the Cluster probes were able to characterize their strength, as well as that of other sources of plasma being added to the Earth’s magnetosphere. When only the cold ions are considered, the amount of atmosphere being lost o space amounts to several thousand tons per year. In short, its like losing socks. Not a big deal, but you’d like to know where they are going, right?

This has been another area of focus for the Cluster mission, which for the last decade and a half has been attempting to explore how these ions are lost, where they come from, and the like. As Philippe Escoubet, ESA’s Project Scientist for the Cluster mission, put it:

“In essence, we need to figure out how cold plasma ends up at the magnetopause. There are a few different aspects to this; we need to know the processes involved in transporting it there, how these processes depend on the dynamic solar wind and the conditions of the magnetosphere, and where plasma is coming from in the first place – does it originate in the ionosphere, the plasmasphere, or somewhere else?“

Color illustration showing the scale of planets in our solar system, focusing on Jupiter and Saturn. Credit: NASA
Color illustration showing the scale of planets in our solar system, focusing on Jupiter and Saturn. Credit: NASA

The reasons for understanding this are clear. High energy particles, usually in the form of solar flares, can pose a threat to space-based technology. In addition, understanding how our atmosphere interacts with solar wind is also useful when it comes to space exploration in general. Consider our current efforts to locate life beyond our own planet in the Solar System. If there is one thing that decades of missions to nearby planets has taught us, it is that a planet’s atmosphere and magnetic environment are crucial in determining habitability.

Within close proximity to Earth, there are two examples of this: Mars, which has a thin atmosphere and is too cold; and Venus, who’s atmosphere is too dense and far too hot. In the outer Solar System, Saturn’s moon Titan continues to intrigue us, mainly because of the unusual atmosphere. As the only body with a nitrogen-rich atmosphere besides Earth, it is also the only known planet where liquid transfer takes place between the surface and the atmosphere – albeit with petrochemicals instead of water.

Moreover, NASA’s Juno mission will spend the next two years exploring Jupiter’s own magnetic field and atmosphere. This information will tell us much about the Solar System’s largest planet, but it is also hoped to shed some light on the history planetary formation in the Solar System.

In the past fifteen years, Cluster has been able to tell astronomers a great deal about how Earth’s atmosphere interacts with solar wind, and has helped to explore magnetic field phenomena that we have only begun to understand. And while there is much more to be learned, scientists agree that what has been uncovered so far would have been impossible without a mission like Cluster.

Further Reading: ESA

Posted on by Evan Gough

New Dwarf Planet Discovered Beyond Neptune

2015 RR245's orbit takes it 120 times further from the Sun than the Earth is. Image: OSSOS/Alex Parker
2015 RR245's orbit takes it 120 times further from the Sun than the Earth is. Image: OSSOS/Alex Parker

A new dwarf planet has been discovered beyond Neptune, in the disk of small icy worlds that resides there. The planet was discovered by an international team of astronomers as part of the Outer Solar Systems Origins Survey (OSSOS). The instrument that found it was the Canada-France Hawaii Telescope at Maunakea, Hawaii.

The planet is about 700 km in size, and has been given the name 2015 RR245. It was first sighted by Dr. JJ Kavelaars, of the National Research Council of Canada, in images taken in 2015. Dwarf planets are notoriously difficult to spot, but they’re important pieces of the puzzle in tracing the evolution of our Solar System.

Dr. Michele Bannister, of the University of Victoria in British Columbia, describes the moment when the planet was discovered: “There it was on the screen— this dot of light moving so slowly that it had to be at least twice as far as Neptune from the Sun.”

These images show 3 hours of RR245's movement. Image: OSSOS
These images show 3 hours of RR245’s movement. Image: OSSOS

“The icy worlds beyond Neptune trace how the giant planets formed and then moved out from the Sun. They let us piece together the history of our Solar System. But almost all of these icy worlds are painfully small and faint: it’s really exciting to find one that’s large and bright enough that we can study it in detail.” said Bannister.

As the New Horizons mission has shown us, these far-flung, cold bodies can have exotic features in their geological landscapes. Where once Pluto, king of the dwarf planets, was thought to be a frozen body locked in time, New Horizons revealed it to be a much more dynamic place. The same may be true of RR245, but for now, not much is known about it.

The 700 km size number is really just a guess at this point. More measurements will need to be taken of its surface properties to verify its size. “It’s either small and shiny, or large and dull.” said Bannister.

As our Solar System evolved, most dwarf planets like RR245 were destroyed in collisions, or else flung out into deep space by gravitational interactions as the gas giants migrated to their current positions. RR245 is one of the few that have survived. It now spends its time the same way other dwarf planets like Pluto and Eris do, among the tens of thousands of small bodies that orbit the sun beyond Neptune.

RR245 has not been observed for long, so much of what’s known about its orbit will be refined by further observation. But at this point it appears to have a 700 year orbit around the Sun. And it looks like for at least the last 100 million years it has travelled its current, highly elliptical orbit. For hundreds of years, it has been further than 12 billion km (80 AU)from the Sun, but by 2096 it should come within 5 billion km (34 AU) of the Sun.

The discovery of RR 245 came as a bit of a surprise to the OSSOS team, as that’s not their primary role. “OSSOS was designed to map the orbital structure of the outer Solar System to decipher its history,” said Prof. Brett Gladman of the University of British Columbia in Vancouver. “While not designed to efficiently detect dwarf planets, we’re delighted to have found one on such an interesting orbit”.

OSSOS has discovered over 500 hundred trans-Neptunian objects, but this is the first dwarf planet it’s found. “OSSOS is only possible due to the exceptional observing capabilities of the Canada-France-Hawaii Telescope. CFHT is located at one of the best optical observing locations on Earth, is equipped with an enormous wide-field imager, and can quickly adapt its observing each night to new discoveries we make. This facility is truly world leading.” said Gladman.

If RR 245's diameter is conclusively measured as 700 km, it will be smaller than the dwarf planet Ceres, which is 945 km in diameter. Image courtesy of NASA.
If RR 245’s diameter is conclusively measured as 700 km, it will be smaller than the dwarf planet Ceres, which is 945 km in diameter. Image courtesy of NASA.

A lot of work has been done to find dwarf planets in the far reaches of our Solar System. It may be that RR 245 is the last one we find. If there are any more out there, they may have to wait until larger and more powerful telescopes become available. In the mid-2020’s, the Large Synoptic Survey Telescope (LSST) will come on-line in Chile. That ‘scope features a 3200 megapixel camera, and each image it captures will be the size of 40 full Moons. It’ll be hard for any remaining dwarf planets to hide from that kind of imaging power.

As for RR 245’s rather uninspiring name, it will have to do for a while. But as the discoverers of the new dwarf planet, the OSSOS team will get to submit their preferred name for the planet. After that, it’s up the International Astronomical Union (IAU) to settle on one.

What do you think? If this is indeed the last dwarf planet to be found in our Solar System what should we call it?