Astronomy Archives

March 31, 2014December 30, 2015 by David Dickinson

Observing Alert: Watch the Moon Cross the Hyades This Week

A photogenic grouping greets evening sky watchers this week providing a fine teaser leading up to a spectacular eclipse.

On the evening of Thursday, April 3^rd headed into the morning of the 4^th, the waxing crescent Moon crosses in front of the Hyades open star cluster. This is the V-shaped asterism that marks the head on Taurus the Bull, highlighted by the brilliant foreground star Aldebaran as the bull’s “eye”. Viewers across North America will have a ring-side seat to this “bull-fight” as the 20% illuminated Moon stampedes over several members of the Hyades in its path.

The passage of the Moon through the Hyades over a three hour span on the night of April 3rd (April 4th in Universal Time) comparing the North American locales of Tampa, Florida and Seattle, Washington. (Credit: Starry Night Education Software).

The brightest stars to be occulted are the Delta Tauri trio of stars ranging in magnitudes from +3.8 (Delta Tauri^1) to +4.8(2) and +4.3(3). Such occlusions – known in astronomy as occultations – are fun to watch, and can reveal the existence of close binary companions as they wink out behind the lunar limb. Several dozen occultations of stars brighter than +5^th magnitude by the Moon happen each year, and the best events occur when the Moon is waxing and the stars disappear against its dark leading edge. We recently caught one such event last month when the Moon occulted the bright star Lambda Geminorum:

We are currently seeing the Moon cross the Hyades during every lunation until the year 2020, though it’s a particularly favorable time to catch the event in April 2014 as the Moon is a slender crescent. Notice that you can just make out the dark limb of the Moon with the naked eye? What you’re seeing is termed Earthshine, and that’s just what it is: the nighttime side of the Moon being illuminated by sunlight that is reflected off of the Earth. Standing on the Earthward side of the Moon, an observer would see a waning gibbous Earth about two degrees across. Yutu has a great view!

Credit Occult 4.0 — The occultation footprint for Delta Tauri^1. Credit: Occult 4.0

The Moon will cross its descending node where its apparent path intersects the ecliptic on April 1^st (no joke, we swear) at 2:30 Universal Time or 10:30 PM EDT on March 31^st. The next nodal crossing now occurs in just two weeks, and the Earth’s shadow will be there to greet the Moon on the morning of April 15^th in the first of four total lunar eclipses that span 2014 and 2015. The month of April also sees the Moon’s orbit at its least eccentric, a time at which perigee – the Moon’s closest point to Earth – is at its most distant and apogee – its farthest point – is at its closest. This currently happens near the equinoxes, through the nodes slowly travel across the ecliptic completing one revolution every 18.6 years. Perigee can vary from 356,400 to 370,400 kilometres, and apogee can span a distance from 404,000 to 406,700 kilometres.

Looking west from the US SE at about 10PM local on the evening of April 3rd. Credit: Stellarium.

We’re also headed towards a “shallow year” in 2015 when the Moon has the least variability in respect to its declination. This trend will then reverse, climaxing with a “Long Nights Moon” riding high in the sky in 2025, which last occurred in 2006. The Moon will inch ever closer to Aldebaran on every successive lunation now, and begins a series of occultations of Aldebaran on January 29^th, 2015 through the end of 2018. Occultations of Aldebaran always occur near these shallow years, and will be followed by a cycle of occultations of Regulus starting in 2017. We caught an excellent daytime occultation of Aldebaran by the Moon from North Pole, Alaska during the last cycle in the late 1990s.

Photos by Author — The Moon passing between the Hyades and Pleiades in 2011 with Earthshine highlighted. Photos by author.

Now for the wow factor. Our Moon is 3,474 kilometres across and located just over one light second away. The Hyades star cluster covers about 6 ½ degrees of sky – about 7 times the size of the Full Moon – but is the closest open cluster to the Earth at 153 light years distant and has a core diameter of about 18 light years across. As mentioned previous, Aldebaran isn’t physically associated with the Hyades, but is merely located in the same direction at 65 light years distant.

The Hyades star cluster also provided early 20^thastronomers with an excellent study in galactic motion. At an estimated 625 million years in age, the Hyades are slowly getting disbanded and strewn about the Milky Way galaxy in a process known as evaporation. The Hyades are also part of a larger stellar incorporation known as the Taurus Moving Cluster. Moving at an average of about 43 kilometres a second, the members of the Hyades are receding from us towards a divergent point near the bright star Betelgeuse in the shoulder of Orion. 50 million years hence, the Hyades will be invisible to the naked eye as seen from Earth, looking like a non-descript open cluster and providing a much smaller target for the Moon to occult at 20’ across. Astronomer Lewis Boss was the first to plot the motion of the Hyades through space in 1908, and the cluster stands as an essential rung on the cosmic distance ladder, with agreeing measurements independently made by both Hubble and Hipparcos and soon to be refined by Gaia.

Photographing and documenting this week’s passage of our Moon across the Hyades is easy with a DSLR camera: don’t be afraid to vary those ISO and shutter speeds to get the mix of the brilliant crescent Moon, the fainter earthshine, and background stars just right. The more adventurous might want to try actually catching the numerous occultations of bright stars on video. And U.S. and Canadian west coast observers are well placed to catch the Moon cross right though the core of the Hyades… a video animation of the event is not out of the question!

And from there, the Moon heads on to its date with destiny and a fine total lunar eclipse on April 15^th which favors North American longitudes. We’ll be back later this week with our complete and comprehensive eclipse guide!

March 31, 2014March 8, 2017 by Fraser Cain

How Far Can You See in the Universe?

When you look into the night sky, you’re seeing tremendous distances away, even with your bare eyeball. But what’s the most distant object you can see with the unaided eye? And what if you get help with a pair of binoculars, a telescope, or even with the Hubble Space Telescope.

Standing at sea level, your head is at an altitude of 2 meters, and the horizon appears to be about 3 miles, or 5 km away. We’re able to see more distant objects if they’re taller, like buildings or mountains, or when we’re higher up in the air. If you get to an altitude of 20 meters, the horizon stretches out to about 11 km. But we can see objects in space which are even more distant with the naked eye. The Moon is 385,000 km away and the Sun is a whopping 150 million km. Visible all the way down here on Earth, the most distant object in the solar system we can see, without a telescope, is Saturn at 1.5 billion km away.

In the very darkest conditions, the human eye can see stars at magnitude 6.5 or greater. Which works about to about 9,000 individual stars. Sirius, the brightest star in the sky, is 8.6 light years. The most distant bright star, Deneb, is about 1500 light years away from Earth. If someone was looking back at us, right now, they could be seeing the election of the 52nd pope, St. Hormidas, in the 6th Century.
There are even a couple of really bright stars in the 8000 light year range, that we might just barely be able to see without a telescope. If a star detonates, we can see it much further away. The famous 1006 supernova was the brightest in history, recorded in China, Japan and the Middle East.

It was a total of 7,200 light years away and was visible in the daytime. There’s even large structures we can see. Outside the galaxy, the Large Magellanic Cloud is 160,000 light years and the Small Magellanic Cloud is almost 200,000 light years away. Unfortunately for us up North, these are only visible from Southern Hemisphere.The most distant thing we can see with our bare eyeballs is Andromeda at 2.6 million light years, which in dark skies looks like a fuzzy blob.

If we cheat and get a little help, say with binoculars – you can see magnitude 10 – fainter stars and galaxies at more than 10 million light-years away. With a telescope you can see much, much further. A regular 8-inch telescope would let you see the brightest quasars, more than 2 billion light years away. Using gravitational lensing the amazing Hubble space telescope can see galaxies, incredibly far out, where the light had left them just hundreds of millions of years after the Big Bang.

If you could see in other wavelengths, you could see different distances. Fortunately for our precious radiation sensitive organs, Gamma and X rays are blocked by our atmosphere. But if you could see in that spectrum, you could see objects exploding billions of light years away. And if you could see in the radio spectrum, you’d be able to see the cosmic microwave background radiation, surrounding us in all directions and marking the edge of the observable universe.

Wouldn’t that be cool? Well, maybe we can… just a little. Turn on your television, some of the static on the screen is this very background radiation, the afterglow of the Big Bang.

What do you think? If you could see far out in the Universe what would you like a close up view of? Tell us in the comments below.

March 28, 2014May 25, 2023 by David Dickinson

Adventures in (Radio) Amateur Astronomy

Is there truly anything new under the Sun? Well, when it comes to amateur astronomy, many observers are branching out beyond the optical. And while it’s true that you can’t carry out infrared or X-ray astronomy from your backyard — or at least, not until amateurs begin launching their own space telescopes — you can join in the exciting world of amateur radio astronomy.

We’ll admit right out the gate that we’re a relative neophyte when it comes to the realm of radio astronomy. We have done radio observations of meteor showers in tandem with optical observations, and have delved into the trove of information on constructing radio telescopes over the years. Consider this post a primer of sorts, an intro into the world of radio amateur astronomy. If there’s enough interest, we’ll follow up with a multi-part saga, constructing and utilizing our own ad-hoc “redneck array” in our very own backyard with which to alarm the neighbors and probe the radio cosmos.

Repurposing a TV Dish for amatuater astronomy. Credit: NSF/NRAO/Assoc. Universities, Inc. — The “Itty-Bitty Array”- Re-purposing a TV Dish for amateur astronomy. Credit: NSF/NRAO/Assoc. Universities, Inc.

…And much like our exploits in planetary webcam imaging, we’ve discovered that you may have gear kicking around in the form of an old TV dish – remember satellite TV? – in your very own backyard. A simple radio telescope setup need not consist of anything more sophisticated than a dish (receiver), a signal strength detector (often standard for pointing a dish at a satellite during traditional installation) and a recorder. As you get into radio astronomy, you’ll want to include such essentials as mixers, oscillators, and amplifiers to boost your signal.

Frequency is the name of the game in amateur radio astronomy, and most scopes are geared towards the 18 megahertz to 10,000 megahertz range. A program known as Radio-SkyPipe makes a good graphic interface to turn your laptop into a recorder.

Radio astronomy was born in 1931, when Karl Jansky began researching the source of a faint background radio hiss with his dipole array while working for Bell Telephone. Jansky noticed the signal strength corresponded to the passage of the sidereal day, and correctly deduced that it was coming from the core of our Milky Way Galaxy located in the constellation Sagittarius. Just over a decade later, Australian radio astronomer Ruby Payne-Scott pioneered solar radio astronomy at the end of World War II, making the first ever observations of Type I and III solar bursts as well as conducting the first radio interferometry observations.

A replica of Jansky's first steerable antanta at Green Bank, West Virginia. — A replica of Jansky’s first steerable antenna at Green Bank, West Virginia. (Public Domain image)

What possible targets exist for the radio amateur astronomer? Well, just like those astronomers of yore, you’ll be able to detect the Sun, the Milky Way Galaxy, Geostationary and geosynchronous communication satellites and more. The simple dish system described above can also detect temperature changes on the surface of the Moon as it passes through its phases. Jupiter is also a fairly bright radio target for amateurs as well.

Radio meteors are also within the reach of your FM dial. If you’ve ever had your car radio on during a thunderstorm, you’ve probably heard the crackle across the radio spectrum caused by a nearby stroke of lightning. A directional antenna is preferred, but even a decent portable FM radio will pick up meteors on vacant bands outdoors. These are often heard as ‘pings’ or temporary reflections of distant radio stations off of the trail of ionized gas left in the wake of a meteor. Like with visual observing, radio meteors peak in activity towards local sunrise as the observer is being rotated forward into the Earth’s orbit.

Amateur SETI is also taking off, and no, we’re not talking about your crazy uncle who sits out at the end of runways watching for UFOs. BAMBI is a serious amateur-led project. Robert Gray chronicled his hunt for the elusive Wow! signal in his book by the same name, and continues an ad hoc SETI campaign. With increasingly more complex rigs and lots of time on their hands, it’s not out of the question that an amateur SETI detection could be achieved.

Another exciting possibility in radio astronomy is tracking satellites. HAM radio operators are able to listen in on the ISS on FM frequencies (click here for a list of uplink and downlink frequencies), and have even communicated with the ISS on occasion. AMSAT-UK maintains a great site that chronicles the world of amateur radio satellite tracking.

Amateur radio equipment that eventually made its way to to ISS aboard STS-106. (Credit: NASA).

Old TV dishes are being procured for professional use as well. One team in South Africa did just that back in 2011, scouring the continent for old defunct telecommunications dished to turn them into a low cost but effective radio array.

Several student projects exist out there as well. One fine example is NASA’s Radio JOVE project, which seeks student amateur radio observations of Jupiter and the Sun. A complete Radio Jove Kit, to include receiver and Radio-SkyPipe and Radio-Jupiter Pro software can be had for just under 300$ USD. You’d have a tough time putting together a high quality radio telescope for less than that! And that’s just in time for prime Jupiter observing as the giant planet approaches quadrature on April 1^st (no fooling, we swear) and is favorably placed for evening observing, both radio and optical.

Fearing what the local homeowner’s association will say when you deploy your very own version of Jodrell Bank in your backyard? There are several online radio astronomy projects to engage in as well. SETI@Home is the original crowd sourced search for ET online. The Zooniverse now hosts Radio Galaxy Zoo, hunting for erupting black holes in data provided by the Karl Jansky Very Large Array and the Australia Telescope Compact Array. PULSE@Parkes is another exciting student opportunity that lets users control an actual professional telescope. Or you can just listen for meteor pings online via NASA’s forward scatter meteor radar based out of the Marshall Space Flight Center in Huntsville, Alabama. Adrian West also hosts live radio meteor tracking on his outstanding Meteorwatch website during times of peak activity.

Forward Scatter — A diagram of a basic forward scatter radar system for meteor observing. Credit: NASA

Interested? Other possibilities exist for the advanced user, including monitoring radio aurorae, interferometry, catching the hiss of the cosmic microwave background and even receiving signals from more distant spacecraft, such as China’s Yutu rover on the Moon.

Think of this post as a primer to the exciting world of amateur radio astronomy. If there’s enough interest, we’ll do a follow up “how-to” article as we assemble and operate a functional amateur radio telescope. Or perhaps you’re an accomplished amateur radio astronomer, with some tips and tricks to share. There’s more to the universe than meets the eye!

-Also be sure to check out SARA, the Society of Amateur Radio Astronomers.

March 28, 2014December 23, 2015 by Elizabeth Howell

Slip-Sliding Away: Solar Flare’s Magnetic Lines Go For A Loop In This Video

Our own Sun produces flares, but we are protected by our magnetosphere, and by the distance from the Sun to Earth. Credit: NASA/ Solar Dynamics Observatory,

When will the next big solar flare occur? How much damage could it cause to power lines and satellites? These are important questions for those looking to protect our infrastructure, but there’s still a lot we need to figure out concerning space weather.

The video above, however, shows magnetic lines weaving together from the surface of the Sun in 2012, eventually creating an eruption that was 35 times our planet’s size and sending out a surge of energy. It’s these energetic flares that can hit Earth’s atmosphere and cause auroras and power surges.

While models of this have been made before, this is the first time the phenomenon was caught in action. Scientists saw it using NASA’s Solar Dynamics Observatory.

Models of the flares show they typically occur amid distorted magnetic fields, the University of Cambridge noted, showing that the lines can “reconnect while slipping and flipping around each other.” Before the flare happens, the magnetic field lines line up in an arc across the sun’s surface (photosphere). That phenonemon is called field line footprints.

“In a smooth, non-entangled arc the magnetic energy levels are low, but entanglement will occur naturally as the footpoints move about each other,” the release added. “Their movement is caused as they are jostled from below by powerful convection currents rising and falling beneath the photosphere. As the movement continues, the entanglement of field lines causes magnetic energy to build up.”

When the energy gets to great, the lines let go of the energy, creating the solar flare and coronal mass ejection that can send material streaming away from the sun. A note, this observation was made of an X-class flare — the strongest kind of flare — and scientists say they are not sure if this phenomenon is true of all kinds of flares. That said, the phenomenon would be harder to spot in smaller flares.

You can read more about the research in the Astrophysical Journal or in preprint version on Arxiv. It was led by Jaroslav Dudik, a researcher at the University of Cambridge’s center for mathemetical sciences.

Source: University of Cambridge

March 27, 2014December 23, 2015 by Bob King

Mars-Bound Comet Siding Spring Sprouts Multiple Jets

Hubble Space Telescope picture of comet C/2013 A1 Siding Spring as observed on March 11, 2014. At that time the comet was 353 million miles from Earth. When the glow of the coma is subtracted through image processing, which incorporates a smooth model of the coma's light distribution, Hubble resolves what appear to be two jets of dust coming off the nucleus in opposite directions. This means that only portions of the surface of the nucleus are presently active as they are warmed by sunlight, say researchers. Credit: NASA, ESA, and J.-Y. Li (Planetary Science Institute)

Comet Siding Spring, on its way to a close brush with Mars on October 19, has been kicking up a storm lately. New images from Hubble Space Telescope taken on March 11, when the comet was just this side of Jupiter, reveal multiple jets of gas and dust.

Illustration showing Comet Siding Spring's orbit and close pass of Mars as it swings around the sun this year. Credit: NASA — Illustration showing Comet Siding Spring’s orbit and close pass of Mars as it plies its way through the inner solar system this year. Credit: NASA

Discovered in January 2013 by Robert H. McNaught at Siding Spring Observatory in Australia, the comet is falling toward the sun along a roughly 1 million year orbit. It will gradually brighten through spring and summer until reaching binocular brightness this fall when it passes 130 million miles (209 million km) from Earth.

Views of the comet on three different dates. Top shows a series of unfiltered images while the bottom are filtered to better show the jets. Credit: — Views of the comet on three different dates. Top shows a series of unfiltered images while the bottom are filtered to better show the jets. Comet Siding Spring’s hazy coma measures about 12,000 miles across and it’s presently about 353 million miles (568 million km) from the sun. Credit: NASA, ESA, J.-Y. Li (Planetary Science Institute)

Astronomers were particularly interested in getting images when Earth crossed the comet’s orbital plane, the path the comet takes as it orbits the sun. The positioning of the two bodies allowed Hubble to make crucial observations of how fast dust particles streamed off the nucleus.

Comet C/2013 A1 Siding Spring photographed from Australia on March 4, 2014. Credit: Rolando Ligustri

“This is critical information that we need to determine whether, and to what degree, dust grains in the coma of the comet will impact Mars and spacecraft in the vicinity of Mars,” said Jian-Yang Li of the Planetary Science Institute in Tucson, Arizona.

On October 19 this year, Comet Siding Spring will pass within 84,000 miles (135,000 km) of Mars or less than half the distance of our moon. There’s a distinct possibility that orbiting Mars probes like NASA’s Mars Reconnaissance Orbiter and the European Mars Express might be enveloped by the comet’s coma (hazy atmosphere) and pelted by dust.

Mars and Comet C/2013 A1 Siding Spring will overlap as seen from Earth on Oct. 19, 2014 when the comet might pass as close as 25,700 miles (41,300 km) from the planet’s center. View shows the sky at the end of evening twilight facing southwest. Stellarium

While comet dust particles are only 1 to 1/10,000 of a centimeter wide, they’ll be moving at 124,000 mph (200,000 km/hr). At that speed even dust motes small can be destructive. Plans are being considered to alter the orbits of the spacecraft to evade the worst of the potential blast. On the bright side, the Red Planet may witness a spectacular meteor storm! Protected by the atmosphere, the Martian rovers aren’t expected to be affected.

I know where I’ll be on October 19 – in the front yard peering at Mars through my telescope. Even if the comet doesn’t affect the planet, seeing the two overlap in conjunction will be a sight not to miss.

March 27, 2014December 23, 2015 by Elizabeth Howell

Rosetta Spacecraft Spies Its Comet As It Prepares For An August Encounter

The Rosetta spacecraft saw its destination (Comet 67P/Churymov-Gerasimenko) on March 20, 2014 from about three million miles (five million kilometers) away. The comet is in the small circle next to the globular star cluster M107. ESA/MPS for OSIRIS-Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA

As Rosetta limbers up for its close-up encounter with a comet, we have visual confirmation that it’s on the right track! The comet spied its destination — Comet 67P/Churymov-Gerasimenko — using its OSIRIS wide-angle camera and narrow-angle camera on March 20 and March 21.

“Finally seeing our target after a 10 year journey through space is an incredible feeling,” stated OSIRIS principal investigator Holger Sierks from the Max Planck Institute for Solar System Research in Germany. “These first images taken from such a huge distance show us that OSIRIS is ready for the upcoming adventure.”

The image comes as Rosetta is preparing its science instruments for its encounter in August.

“Currently, Rosetta is on a trajectory that would, if unchanged, take it past the comet at a distance of approximately 50 000 km and at a relative speed of 800 m/s. A critical series of manoeuvres beginning in May will gradually reduce Rosetta’s velocity relative to the comet to just 1 m/s and bring it to within 100 km by the first week of August,” the European Space Agency stated.

Here’s an animation of how big the comet will appear to Rosetta as it gets closer:

“Between May and August the 4 km-wide comet will gradually ‘grow’ in Rosetta’s field of view from appearing to have a diameter of less than one camera pixel to well over 2000 pixels – equivalent to a resolution of around 2 m per pixel – allowing the first surface features to be resolved.”

For more information on the science commissioning, check out the Rosetta blog.

Artist's impression (not to scale) of the Rosetta orbiter deploying the Philae lander to comet 67P/Churyumov–Gerasimenko. Credit: ESA–C. Carreau/ATG medialab. — Artist’s impression (not to scale) of the Rosetta orbiter deploying the Philae lander to comet 67P/Churyumov–Gerasimenko. Credit: ESA–C. Carreau/ATG medialab.

March 26, 2014December 23, 2015 by Elizabeth Howell

Discovery! Possible Dwarf Planet Found Far Beyond Pluto’s Orbit

Artist's conception of Sedna, a dwarf planet in the solar system that only gets within 76 astronomical units (Earth-sun distances) of our sun. Credit: NASA/JPL-Caltech

What is a dwarf planet? Some astronomers have been asking that question after Pluto was demoted from planethood almost a decade ago, partly due to discoveries of other worlds of similar proportions.

Today, astronomers announced the discovery of 2012 VP113, a world that, assuming its reflectivity is moderate, is 280 miles (450 kilometers) in size and orbiting even further away from the sun than Pluto or even the more distant Sedna (announced in 2004). If 2012 VP113 is made up mostly of ice, this would make it large (and round) enough to be a dwarf planet, the astronomers said.

Peering further into 2012 VP113’s discovery, however, brings up several questions. What are the boundaries of the Oort Cloud, the region of icy bodies where the co-discoverers say it resides? Was it placed there due to a sort of Planet X? And what is the definition of a dwarf planet anyway?

First, a bit about 2012 VP113. Its closest approach to the Sun is about 80 astronomical units, making it 80 times further from the Sun than Earth is. This puts the object in a region of space previously known only to contain Sedna (76 AU away). It’s also far away from the Kuiper Belt, a region of rocky and icy bodies between 30 and 50 AU that includes Pluto.

The discovery images of 2012 VP113. Each one was taken about two hours apart on Nov. 5, 2012. Behind the object, you can see background stars and galaxies that remained still (from Earth's perspective) in the picture frame. Credit: Scott S. Sheppard: Carnegie Institution for Science — The discovery images of 2012 VP113. Each one was taken about two hours apart on Nov. 5, 2012. Behind the object, you can see background stars and galaxies that remained still (from Earth’s perspective) in the picture frame. Credit: Scott S. Sheppard: Carnegie Institution for Science

“The detection of 2012 VP113 confirms that Sedna is not an isolated object; instead, both bodies may be members of the inner Oort Cloud, whose objects could outnumber all other dynamically stable populations in the Solar System,” the authors wrote in their discovery paper, published today in Nature.

The Oort cloud (named after the Dutch astronomer Jan Oort, who first proposed it) is thought to contain a vast number of smallish, icy bodies. This NASA web page defines its boundaries as between 5,000 and 100,000 AUs, so 2012 VP113 obviously falls short of this measure.

The astronomers hypothesize that 2012 VP113 is part of a collection of “inner Oort cloud objects” that make their closest approach at a distance of more than 50 AU, a boundary that is thought to avoid any “significant” interference from Neptune. Orbits of these objects would range no further than 1,500 AU, a location hypothesized as part of the “outer Oort cloud” — the spot where “galactic tides start to become important in the formation process,” the team wrote.

“Some of these inner Oort cloud objects could rival the size of Mars or even Earth. This is because many of the inner Oort cloud objects are so distant that even very large ones would be too faint to detect with current technology,” stated Scott Sheppard, co-author of the paper and a solar system researcher at the Carnegie Institution for Science. (The lead author is the Gemini Observatory’s Chadwick Trujillo, who co-discovered several dwarf planets with the California Institute of Technology’s Mike Brown.)

The layout of the solar system, including the Oort Cloud, on a logarithmic scale. Credit: NASA

One large question is how 2012 VP113 and Sedna came to be. And of course, with only two objects, it’s hard to draw any definitive conclusions. Theory 1 supposes that the gas giant planets beyond Earth ejected a “rogue” planet (or planets) that in turn threw objects from the Kuiper Belt to the more distant inner Oort Cloud. “These planet-sized objects could either remain (unseen) in the Solar System or have been ejected from the Solar System during the creation of the inner Oort Cloud,” the researchers wrote.

(Planet X hopers: Note that NASA just released results from its Wide-Field Infrared Survey Explorer that found nothing Saturn’s size (or bigger) as far as 10,000 AU, and nothing bigger than Jupiter at 26,000 AU.)

Theory 2 postulates that a passing star moved objects closer to the Sun into the inner Oort cloud. The last, “less-explored” theory is that these objects are “extrasolar planetesimals” — small worlds from other stars — that happened to be close to the Sun when it was born in a field of stars.

However these objects came to be, the astronomers estimate there are 900 objects with orbits similar to Sedna and 2012 VP113 that have diameters larger than 620 miles (1,000 kilometers). How do we know which are dwarf planets, however, given their distance and small size?

Artist's impression of Makemake, a dwarf planet about two-thirds Pluto's size. Credit: ESO/L. Calçada/Nick Risinger (skysurvey.org) — Artist’s impression of Makemake, a dwarf planet about two-thirds Pluto’s size. Credit: ESO/L. Calçada/Nick Risinger (skysurvey.org)

The International Astronomical Union’s definition of a dwarf planet doesn’t mention how big an object has to be to qualify as a dwarf planet. It reads: “A dwarf planet is an object in orbit around the Sun that is large enough (massive enough) to have its own gravity pull itself into a round (or nearly round) shape. Generally, a dwarf planet is smaller than Mercury. A dwarf planet may also orbit in a zone that has many other objects in it. For example, an orbit within the asteroid belt is in a zone with lots of other objects.”

That same page mentions there are only five recognized dwarf planets: Ceres, Pluto, Eris, Makemake and Haumea. Brown led the discovery of the last three dwarf planets in this list, and calls himself “the man who killed Pluto” because his finds helped demote Pluto from planethood to dwarf planet status.

It’s hard for official bodies to keep up with the pace of discovery, however. Brown’s webpage lists 46 “likely” dwarf planets, which under this definition would give him 15 discoveries.

“Reality … does not pay much attention to official lists kept by the IAU or by anyone else,” he wrote on that page. “A more interesting question to ask is: how many round objects are there in the solar system that are not planets? These are, by the definition, dwarf planets, whether or not they ever make it to any offiicially sanctioned list. If the category of dwarf planet is important, then it is the reality that is important, not the official list.”

Artist's impression of the dwarf planet Haumea and its moons, Hi'aka and Namaka. Credit: NASA — Artist’s impression of the dwarf planet Haumea and its moons, Hi’aka and Namaka. Credit: NASA

His analysis (which focuses on Kuiper Belt objects) notes that most objects are too faint for us to notice if they are round or not, but you can get a sense of how round an object is by its size and composition. The asteroid belt’s Ceres (at 560 miles or 900 km) is the only known round, rocky object.

For icier objects, he suggested looking to icy moons to understand how small an object can be and still be round. Saturn’s moon Mimas is round at 250 miles (400 km), which he classifies as a “reasonable lower limit” (since observed satellites of 125 miles/200 km are not round).

Discovery of 2012 VP113 came courtesy of the new Dark Energy Camera (DECam) at the National Optical Astronomy Observatory’s 4-meter telescope in Chile. The orbit was determined with the Magellan 6.5-meter telescope at Carnegie’s Las Campanas Observatory, also in Chile.

The paper, called “A Sedna-like body with a perihelion of 80 astronomical units”, will soon be available on Nature’s website.

March 26, 2014December 23, 2015 by Elizabeth Howell

Surprise! Asteroid Hosts A Two-Ring Circus Above Its Surface

Artist's impression of what the rings of the asteroid Chariklo would look like from the small body's surface. The rings' discovery was a first for an asteroid. Credit: ESO/L. Calçada/Nick Risinger (skysurvey.org)

Rings are a tough phenomenon to spot. As late as 1977, astronomers thought that the only thing in the solar system with rings was the planet Saturn. Now, we can add the first asteroid to the list of ringed bodies nearby us. The asteroid 10199 Chariklo hosts two rings, perhaps due to a collision that caused a chain of debris circling its tiny surface.

Besides the 250-kilometer (155-mile) Chariklo, the only other ringed bodies known to us so far are (in order of discovery) Saturn, Uranus, Jupiter and Neptune.

“We weren’t looking for a ring and didn’t think small bodies like Chariklo had them at all, so the discovery — and the amazing amount of detail we saw in the system — came as a complete surprise,” stated Felipe Braga-Ribas of the National Observatory (Observatório Nacional) in Brazil, who led the paper about the discovery.

Illustration of how Asteroid Chariklo may have gotten its rings. Copyright: Estevan Guzman for Universe Today.

The rings came to light, so to speak, when astronomers watched Chariklo passing in front of the star UCAC4 248-108672 on June 3, 2013 from seven locations in South America. While watching, they saw two dips in the star’s apparent brightness just before and after the occultation. Better yet, with seven sites watching, researchers could compare the timing to figure out more about the orientation, shape, width and more about the rings.

The observations revealed what is likely a 12.4-mile (20-kilometer)-wide ring system that is about 1,000 times closer to the asteroid than Earth is to the moon. What’s more, astronomers suspect there could be a moon lying amidst the asteroid’s ring debris.

Artist's impression of two rings discovered around the asteroid Chariklo. It was the first such discovery made for an asteroid. Credit: ESO/L. Calçada/M. Kornmesser/Nick Risinger (skysurvey.org) — Artist’s impression of two rings discovered around the asteroid Chariklo. It was the first such discovery made for an asteroid. Credit: ESO/L. Calçada/M. Kornmesser/Nick Risinger (skysurvey.org)

If these rings are the leftovers of a collision as astronomers suspect, this would give fodder to the idea that moons (such as our own moon) come to be from collisions of smaller bits of material. This is also a theory for how planets came to be around stars.

The rings haven’t been named officially yet, but the astronomers are nicknaming them Oiapoque and Chuí after two rivers near the northern and southern ends of Brazil.

Because these occultation events are so rare and can show us more about asteroids, astronomers pay attention when they occur. Part of the Eastern Seabord enjoyed a more recent asteroid-star occultation on March 20.

The original paper, “A ring system detected around the Centaur (10199) Chariklo”, will soon be available on the Nature website.

Source: European Southern Observatory

Artist's impression of rings around the asteroid Chariklo. This was the first asteroid where rings were discovered. Credit: ESO/L. Calçada/M. Kornmesser/Nick Risinger (skysurvey.org) — Artist’s impression of rings around the asteroid Chariklo. This was the first asteroid where rings were discovered. Credit: ESO/L. Calçada/M. Kornmesser/Nick Risinger (skysurvey.org)

March 26, 2014December 23, 2015 by Elizabeth Howell

Rocky Alien Planet Leftovers ‘Polluted’ White Dwarf Stars With Metal

Artist’s impression of a massive asteroid belt in orbit around a star. Earth's water may not have all come from asteroids and comets, so maybe that's true for exoplanets. Credit: NASA-JPL / Caltech / T. Pyle (SSC)

What’s with all the metals in the atmosphere of white dwarfs, those things that are corpses of stars like our own Sun? While before scientists had theories about levitating star layers that “polluted” the white dwarfs, new research shows it’s more likely due to rocky material. More specifically, material left over from planet formation.

Researchers surveyed 89 of these objects with the Far Ultraviolet Spectroscopic Explorer, a NASA space telescope which operated from 1999 to 2008. The stars’ spectra was analyzed to see what distinctive wavelengths of elements showed up.

Scientists discovered that in one-third of these stars, the ratio of silicon to carbon material is pretty close to what is seen in rocks, and is much higher than what would be expected in stars. The work implies that only a fraction of stars like our Sun would have terrestrial planets, researchers added.

Artist’s impression of debris around a white dwarf star. Credit: NASA, ESA, STScI, and G. Bacon (STScI)

“The mystery of the composition of these stars is a problem we have been trying to solve for more than 20 years,” stated Martin Barstow of the University of Leicester, who led the research.

“It is exciting to realize that they are swallowing up the leftovers from planetary systems, perhaps like our own, with the prospect that more detailed follow-up work will be able to tell us about the composition of rocky planets orbiting other stars.”

You can read more about the research in the Monthly Notices of the Royal Astronomical Society. The research team includes Barstow’s daughter, Jo, who was doing a summer work placement in Leicester at the time. She is now working at Oxford University in the field of extrasolar planets.

Source: Royal Astronomical Society

March 24, 2014December 23, 2015 by David Dickinson

Ready, Set, Messier Marathon: A 2014 Guide

Patiently awaiting darkness at the starting line... Credit and copyright: John Chumack.

Have YOU seen all 110?

The passage of the northward equinox last week on March 20^th means one thing in the minds of many a backyard observer: the start of Messier Marathon season. This is a time of year during which a dedicated observer can conceivably spot all of the objects in Charles Messier’s famous deep sky catalog in the span of one night.

We’ve written about some tips and tricks to completing this challenge previously, as well as the optimal dates for carrying a marathon out. Typically, the New Moon weekend nearest the March equinox is the best time of year for northern hemisphere observers to target all of the objects on Messier’s list. This works because a majority of the Messier objects are clustered into two regions: towards the core of our galaxy in Sagittarius — where the Sun sits during the December solstice — up through the summer triangle constellations of Cygnus, Aquila and Lyra, and in the bowl of Virgo asterism and its super cluster of galaxies that extends northward into the constellation of Coma Berenices. In March through early April the Sun sits in the constellation of Pisces, well away from the galactic plane.

The prospects for completing a Messier marathon in 2014 favor the last weekend on March on the 29^th-30^th. The Moon reaches New on Sunday, March 30^th at 18:45 Universal Time/2:45 PM EDT.

Messier marathons first came into vogue in the early 1970s right around the time Schmidt-Cassegrain and large Dobsonian “light bucket” telescopes came into general use.

Charles Messier began noting the curious objects that he would later incorporate into his famous catalog during the summer of 1758, with his description of the Crab Nebula in Taurus, which would become Messier object number one or M1. Messier was a prolific comet hunter and discovered 21 comets in his lifetime. The catalog was compiled over the span of 13 years from 1771 to 1784. Messier’s original list contained 45 objects, and was later expanded in subsequent editions 103, with Messier’s assistant Pierre Méchain adding six more objects to the catalog. The list is generally tallied at 110 objects, with one famous controversy being M102, which is generally cited as a re-observation of M101 or the galaxy NGC 5866.

The catalog itself contains a grab bag of open and globular clusters, galaxies, planetary and diffuse nebulae, and one double star (M40). The Messier catalog spans the sky down to M7, an object also known as the Ptolemy Cluster, which is the southernmost object on the list at latitude -34 degrees 48’ south.

The first page of Messier's third revision of his catalog describing M1 through M5. Image in th Public Domain. — The first page of Messier’s third revision of his catalog, describing M1 through M5. Image in the Public Domain.

Messier observed from Paris at latitude +48 degrees 51’ north using two primary telescopes of the almost one dozen that he owned for his discoveries: a 6.4” Gregorian reflector and a 3.5” refractor. Messier knew nothing of the nature of these “faint fuzzies” that he’d periodically stumbled across in his cometary vigil. His original intent was to compile a list of “comet imposters” in the night sky for comet hunters to be aware of in their quests. In his words:

“What made me produce this catalog was the nebula which I had seen in Taurus while I was observing the comet of that year (1758). The shape and brightness of that nebula reminded me so much of a comet, that I undertook to find more of its kind, to save astronomers from confusing these nebulae with comets.”

“Beware, here doth not lie comets,” Messier admonishes future generations of observers. Still, some peculiarities remain in the catalog: why did Messier, for example, include such obvious “non-comets” as the Pleiades (M45), but skip over the brilliant Double Cluster in Perseus?

Charles Messier's 1771 sketch of the Orion nebula, M42 in the Messier Catalog. Image in the public domain. — Charles Messier’s 1771 sketch of the Orion nebula, M42 in the Messier Catalog. Image in the public domain.

Alas, such mysteries are known only to Messier, who was interred at the famous Père Lachaise cemetery after his death in 1817. When we visit Paris, we’ll bypass Jim Morison to leave a copy of Burnham’s Celestial Handbook at Messier’s grave.

And just like the road variety, “running the Messier marathon” takes all of the stamina and pacing that a visual athlete can muster. You’ll want to grab M77 and M74 immediately after dusk, or the marathon will be over before it starts. From there, move on up north to the famous Andromeda galaxy (M31) and the scattering of objects around it before settling in for a more leisurely observing pace moving westward through the constellations of Orion, Leo and surrounding objects.

An all-sky map showing the distribution of Messier objects. (Click to enlarge). Credit: Jim Cornmell under a Wikimedia Commons Attribution-Share Alike 3.0 Unported license.

Now towards the approach of local midnight comes the first large group: the Virgo cluster of galaxies extending through Coma Berenices, rising to the east. After this batch, you can catch some quick shut-eye before bagging the Messier objects towards the galactic center and up through Cygnus in the pre-dawn. Plan ahead; M52, M2 and M30 are especially notoriously difficult in the spring dawn sky!

It’s also worth noting your “attitude versus latitude” plays a role as well. To this end, Ed Kotapish compiled this nifty perpetual chart of when the entire Messier catalog is visible from respective latitudes:

A chart calculating number of total Messier objects that are visible on the dates (vertical column in month-day format) versus north latitude (top row). Note that this chart is pertpetual for non-leap years, and does not take into account the pahse of the Moon. Click to enlarge. Credit: Edward Kotapish.

“The bounds of the chart are for a variety of objects,” Ed told Universe Today. “I used nautical twilight (when the Sun falls below -12 degrees in elevation) as the starting and ending condition.” Ed also notes that the top curve of the chart on the morning side is bounded by the difficulty in finding troublesome M30, while the left bottom evening boundary is limited by the observability of M110 and M74, which can be a problem for observers at higher latitudes.

Alternate versions of the Messier marathon exist as well, such as imaging or even sketching all 110 objects in one night.

Why complete a Messier marathon? Well, not only does such a feat hone your visual skills as an observer, but it also familiarizes you with the entire catalog… and there’s nothing that says you have to complete it all in one evening, except of course, for bragging rights at the next star party!

Good luck!

-Here’s a handy list of all 110 of the Messier objects in the catalog.

-Be sure to send those pics of Messier objects and more in to Universe Today’s Flickr forum!