Astronomy Archives

February 19, 2015December 23, 2015 by Elizabeth Howell

Interesting Facts About Mercury

Caloris in Color – An enhanced-color view of Mercury from the cameras on board the MESSENGER spacecraft. The circular, orange area near the center-top of the disc is Caloris Basin. Credit: NASA / Johns Hopkins University Applied Physics Laboratory / Carnegie Institution of Washington

Close by the Sun is Mercury, a practically atmosphere-like world that has a lot of craters. Until NASA’s MESSENGER spacecraft arrived there in 2008, we knew very little about the planet — only part of it had been imaged! But now that the spacecraft has been circling the planet for a few years, we know a heck of a lot more. Here is some stuff about Mercury that’s useful to know.

1. Mercury has water ice and organics.

This may sound surprising given that the planet is so close to the Sun, but the ice is in permanently shadowed craters that don’t receive any sunlight. Organics, a building block for life, were also found on the planet’s surface. While Mercury doesn’t have enough atmosphere and is too hot for life as we know it, finding organics there demonstrates how those compounds were distributed throughout the solar system. There’s also quite a bit of sulfur on the surface, something that scientists are still trying to understand since no other planet in the Solar System has it in such high concentrations.

2. The water ice appears younger than we would expect.

Close examination of the ice shows sharp boundaries, which implies that it wasn’t deposited that long ago; if it was, the ice would be somewhat eroded and mixed in with Mercury’s regolith surface. So somehow, the ice perhaps came there recently — but how? What’s more, it appears the ice deposits on the Moon and the ice deposits on Mercury are different ages, which could imply different conditions for both of the bodies.

A forced perspective view of Mercury's north pole (NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington) — A forced perspective view of Mercury’s north pole (NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington)

3. Mercury has an atmosphere that changes with its distance to the Sun.

The planet has a very thin atmosphere that is known as an “exosphere” (something that is also present on the Moon, for example.) Scientists have detected calcium, sodium and magnesium in it — all elements that appear to change in concentration as the planet gets closer and further from the Sun in its orbit. The changes appear to be linked to how much solar radiation pressure falls on the planet.

4. Mercury’s magnetic field is different at its poles.

Mercury is somehow generating a magnetic field in its interior, but it’s quite weak (just 1% that of Earth’s). That said, scientists have observed differences in the north and the south pole magnetic strength. Specifically, at the south pole, the magnetic field lines have a bigger “hole” for charged particles from the Sun to strike the planet. Those charged particles are believed to erode Mercury’s surface and also to contribute to its composition.

Illustration of MESSENGER in orbit around Mercury (NASA/JPL/APL)

5. Despite Mercury’s weak magnetic field, it behaves similarly to Earth’s.

Specifically, the magnetic field does deflect charged particles similarly to how Earth does, creating a “hot flow anomaly” that has been observed on other planets. Because particles flowing from the Sun don’t come uniformly, they can get turbulent when they encounter a planet’s magnetic field. When plasma from the turbulence gets trapped, the superheated gas also generates magnetic fields and creates the HFA.

6. Mercury’s eccentric orbit helped prove Einstein’s theory of relativity.

Mercury’s eccentric orbit relative to the other planets, and its close distance to the Sun, helped scientists confirm Einstein’s general theory of relativity. Simply put, the theory deals with how the light of a star changes when another planet or star orbits nearby. According to Encyclopedia Britannica, scientists confirmed the theory in part by reflecting radar signals off of Mercury. The theory says that the path of the signals will change slightly if the Sun was there, compared to if it was not. The path matched what general relativity predicted.

A hot flow anomaly, or HFA, has been identified around Mercury (Credit: NASA/Duberstein)

7. Mercury is hard to spot in the sky, but has been known for millennia.

Mercury tends to play peekaboo with the Sun, which makes it somewhat of an observing challenge. The planet rises or sets very close to when the Sun does, which means amateur astronomers are often fighting against twilight to observe the tiny planet. That being said, the ancients had darker skies than we did (no light pollution) and were able to see Mercury pretty well. So the planet has been known for thousands of years, and was linked to some of the gods in ancient cultures.

8. Mercury has no moons or rings.

Scientists are still trying to understand how the Solar System formed, and one of the ways they do so is by comparing the planets. Interesting to note about Mercury: it has no rings or moons, which makes it different from just about every other planet in our Solar System. The exception is Venus, which also has no moons or rings.

February 18, 2015December 23, 2015 by Tim Reyes

A Star Passed Through the Solar System Just 70,000 Years Ago

A binary star system Credit: Michael Osadciw/University of Rochester

Astronomers have reported the discovery of a star that passed within the outer reaches of our Solar System just 70,000 years ago, when early humans were beginning to take a foothold here on Earth. The stellar flyby was likely close enough to have influenced the orbits of comets in the outer Oort Cloud, but Neandertals and Cro Magnons – our early ancestors – were not in danger. But now astronomers are ready to look for more stars like this one.

A comparison of the Solar System and its Oort Cloud. 70,000 years ago, Scholz's Star and companion passed along the outer boundaries of our Solar System (Credit: NASA, Michael Osadciw/University of Rochester) — A comparison of the Solar System and its Oort Cloud. 70,000 years ago, Scholz’s Star and companion passed along the outer boundaries of our Solar System (Credit: NASA, Michael Osadciw/University of Rochester, Illustration-T.Reyes)

Lead author Eric Mamajek from the University of Rochester and collaborators report in The Closest Known Flyby Of A Star To The Solar System (published in Astrophysical Journal on February 12, 2015) that “the flyby of this system likely caused negligible impact on the flux of long-period comets, the recent discovery of this binary highlights that dynamically important Oort Cloud perturbers may be lurking among nearby stars.”

The star, named Scholz’s star, was just 8/10ths of a light year at closest approach to the Sun. In comparison, the nearest known star to the Sun is Proxima Centauri at 4.2 light years.

While the internet has been rife with threads and accusations of a Nemesis star that is approaching the inner Solar System and is somehow being “hidden” by NASA, this small red dwarf star with a companion represents the real thing.

In 1984, the paleontologists David Raup and Jack Sepkoski postulated that a dim dwarf star, now widely known on the internet as the Nemesis Star, was in a very long period Solar orbit. The elliptical orbit brought the proposed star into the inner Solar System every 26 million years, causing a rain of comets and mass extinctions on that time period. By no coincidence, because of the sheer numbers of red dwarfs throughout the galaxy, Scholz’s star nearly fits such a scenario. Nemesis was proposed to be in a orbit extending 95,000 A.U. compared to Scholz’s nearest flyby distance of 50,000 A.U. Recent studies of impact rates on Earth, the Moon and Mars have discounted the existence of a Nemesis star (see New Impact Rate Count Lays Nemesis Theory to Rest, Universe Today, 8/1/2011)

But Scholz’s star — a real-life Oort Cloud perturber — was a small red dwarf star star with a M9 spectral classification. M-class stars are the most common star in our galaxy and likely the whole Universe, as 75% of all stars are of this type. Scholz’s is just 15% of the mass of our Sun. Furthermore, Scholz’s is a binary star system with the secondary being a brown dwarf of class T5. Brown Dwarfs are believed to be plentiful in the Universe but due to their very low intrinsic brightness, they are very difficult to discover … except, as in this case, as companions to brighter stars.

The astronomers reported that their survey of new astrometric data of nearby stars identified Scholz’s as an object of interest. The star’s transverse velocity was very low, that is, the stars sideways motion. Additionally, they recognized that its radial velocity – motion towards or away from us, was quite high. For Scholz’s, the star was speeding directly away from our Solar System. How close could Scholz’s star have been to our system in the past? They needed more accurate data.

The collaborators turned to two large telescopes in the southern hemisphere. Spectrographs were employed on the Southern African Large Telescope (SALT) in South Africa and the Magellan telescope at Las Campanas Observatory, Chile. With more accurate trangental and radial velocities, the researchers were able to calculate the trajectory, accounting for the Sun’s and Scholz’s motion around the Milky Way galaxy.

Scholz’s star is an active star and the researchers added that while it was nearby, it shined at a dimly of about 11th magnitude but eruptions and flares on its surface could have raised its brightness to visible levels and could have been seen as a “new” star by primitive humans of the time.

The relative sizes of the inner Solar System, Kuiper Belt and the Oort Cloud. (Credit: NASA, William Crochot)

At present, Scholz’s star is 20 light years away, one of the 70 closest stars to our Solar System. However, the astronomers calculated, with a 98% certainty, that Scholz’s passed within 0.5 light years, approximately 50,000 Astronomical Units (A.U.) of the Sun.

An A.U. is the mean distance from the Earth to the Sun and 50,000 is an important mile marker in our Solar System. It is the outer reaches of the Oort Cloud where billions of comets reside in cold storage, in orbits that take hundreds of thousands of years to circle the Sun.

With this first extraordinary close encounter discovered, the collaborators of this paper as well as other researchers are planning new searches for “Nemesis” type stars. The Large Synoptic Survey Telescope (LSST) and other telescopes within the next decade will bring an incredible array of data sets that will uncover many more red dwarf, brown dwarf and possibly orphan planets roaming in nearby space. Some of these could likewise be traced to past or future near misses to the Sun and Earth system.

February 18, 2015December 23, 2015 by Ramin Skibba

How do Gas and Stars Build a Galaxy?

ALMA image of the galaxy NGC 253, with a diffuse envelope of carbon monoxide gas (in red) which surrounds star-forming regions (in yellow). The ALMA data are superimposed on a Hubble image that covers part of the same region. Credit: Credit: B. Saxton (NRAO/AUI/NSF); ALMA (NRAO/ESO/NAOJ); A. Leroy; STScI/NASA, ST-ECF/ESA, CADC/NRC/CSA

When we look up at the night sky outside of the bright city, we can see a dazzling array of stars and galaxies. It is more difficult to see the clouds of gas within galaxies, however, but gas is required to form new stars and allow galaxies to grow. Although gas makes up less than 1% of the matter in the universe, “it’s the gas that drives the evolution of the galaxy, not the other way around,” says Felix “Jay” Lockman of the National Radio Astronomy Observatory (NRAO).

With radio telescopes and surveys such as the Green Bank Telescope (GBT) in West Virginia, the Atacama Large Millimeter/submillimeter Array (ALMA), and the Arecibo Legacy Fast ALFA (ALFALFA) survey, Lockman and other astronomers are learning more about the role of gas in galaxy formation. They presented their results at the annual American Association for the Advancement of Science (AAAS) meeting in San Jose.

Although we have an excellent view of our part of the Milky Way, and we can tell that it has a disk-shaped structure — that is the origin of its name, after all — it is not so simple to study how the galaxy formed. Lockman described the situation with an analogy: if you were trying to understand how your own house was built without leaving it, you would look and listen throughout the house and you would look out the window to learn what you can from your neighbors’ homes. Andromeda is the Milky Way’s largest neighbor, and they both have “satellite” galaxies traveling around them, some of which appear to have gas.

In addition, Lockman and his colleagues found clouds of gas between Andromeda and one of its satellites, Triangulum, which could be a “source of fuel for future star formation” for the galaxies. As a dramatic example of high-velocity clouds, Lockman presented new GBT images of the Smith Cloud, which was first discovered in 1963 by a student in the Netherlands. The Smith Cloud is a newcomer to the Milky Way and could provide enough gas to form a million stars and solar systems. Based on its speed and trajectory, “we think in a few million years, splash!” as it collides with our galaxy.

Artist's impression of the Smith Cloud approaching the Milky Way, with which it will collide in approximately 30 million years. The cloud's image from the GBT can be seen at bottom. Credit: NRAO/AUI/NSF — Artist’s impression of the Smith Cloud approaching the Milky Way, with which it will collide in approximately 30 million years. The cloud’s image from the GBT can be seen at bottom. Credit: NRAO/AUI/NSF

Kartik Sheth, another scientist at NRAO, continued with a description of astronomers’ current state of knowledge of the assembly of disk and spiral galaxies, of which the Milky Way and Andromeda are only two examples. Spiral galaxies typically have many gas clouds forming new stars, often referred to as stellar nurseries, and now with ALMA, “a fantastic telescope at 16,500-ft elevation,” Sheth and his colleagues are studying them in more detail.

In particular, Sheth presented newly published results by Adam Leroy in the Astrophysical Journal, in which they examine star-forming clouds in the heart of the nearby starbursting galaxy, Sculptor, to study “the physics of how gas got converted into stars.” Sculptor and other starbursts form stars at a rate about 1,000 times faster than typical spiral galaxies like the Milky Way. “Only with ALMA can we actually accomplish observations like this” of objects outside our galaxy. By comparing the concentration and distribution of ten gas clouds in Sculptor, they find that the clouds are more massive, ten times denser, and more turbulent than similar clouds in more typical galaxies. Because of the density of these stellar nurseries, they can form stars much more efficiently.

Other astronomers at the AAAS meeting, such as Claudia Scarlata (University of Minnesota) and Eric Wilcots (University of Wisconsin), presented a larger-scale picture of how spiral galaxies collide with each other to form more massive elliptical-shaped galaxies. These galaxies typically appear older and have stopped forming stars, but they can grow by “merging” with a neighboring galaxy in its group. “I will contend that most galaxy transformations take place in groups,” says Wilcots. In a paper based on ALFALFA data published in the Astronomical Journal, Kelley Hess and Wilcots find gas-rich galaxies distributed primarily in the outskirts of groups, and therefore these systems tend to grow from the inside out.

In a related issue, both Priyamvada Natarajan (Yale University) and Scarlata discussed how the evolution of massive black holes at the centers of galaxies appear to be related to that of the galaxy as a whole, when astronomers follow them from “cradle to adulthood.” In particular, Natarajan explained how mature galaxies’ black holes can heat the gas in a galaxy and drive gas outflows, thus preventing continued star formation in the galaxy.

Finally, astronomers look forward to much more upcoming cutting-edge research on gas in galaxies. Ximena Fernández (Columbia University) described the COSMOS HI Large Extragalactic Survey (CHILES) of hydrogen gas in galaxies with the Very Large Array. They have completed a pilot survey so far, in which they have obtained the most distant detection so far of a galaxy containing gas. They plan to peer even further into the distant past than previous surveys, expecting to detect gas in 300 galaxies up to 5 billion light-years away—250 times further than the galaxy observed by Leroy.

Fernández also described MeerKAT, a radio telescope under construction in South Africa, and the Deep Investigation of Neutral Gas Origins (DINGO) in Australia, both of which will serve as precursors for the Square Kilometer Array in the 2020s. These new telescopes will add to astronomers’ increasingly complex view of the formation and evolution of galaxies.

February 18, 2015December 23, 2015 by David Dickinson

Black Moon: Why the New Moon on February 18th is Special

Did you hear the one about last month’s ‘supermoon?’

Yeah, we know. The hype was actually for an event that was less than spectacular, as it revolved around the first New Moon of 2015 on January 20^th. Said suspect Moon was touted as ‘super’ (we prefer the quixotic term proxigean) as it occurred 18 hours prior to perigee.

Not that the first lunar perigee of 2015 was an especially close one in time or space at 359,642 kilometres distant. Is every New and Full Moon now destined to become branded ‘super’ in the never ending SEO quest to get eyeballs on web pages?

But wait, there’s more. We’ve noticed as of late that another popular term is creeping into the popular astronomical vernacular: that of a ‘Black Moon’.

Black Moons for the next decade. Created by the author.

We’ve written lots about Moons both of the Black and Blue variety before. We’ll also let you in on a small secret: astronomers rarely sit around observatories discussing these Moons, be they Blue, Black or Super. At most, astronomers note the weeks surrounding New as the ‘Dark of the Moon,’ a prime time to go deep for faint objects while the light polluting Moon is safely out of the sky. And yes, terms such as ‘Super’ or ‘Black Moon’ have dubious roots in astrology, while the term Blue Moon comes down to us via a curious mix-up from Sky and Telescope and the Maine Farmer’s Almanac.

Simply put, a Black Moon is the New Moon version of a Blue Moon, and is either:

A month missing a Full or New Moon… this can only occur in February, as the lunar synodic period from like phase to phase is 29.5 days long. This last occurred in 2014 and will next occur in 2018.
The second New Moon in a month with two. This can happen in any calendar month except February.
And now for the most convoluted definition: the third New Moon in an astronomical season with four.

We bring this up because the February 18^th New Moon is ‘Black’ in the sense that it meets the requirements expressed in rule 3. The fourth New Moon of the season falls on March 20^th, just 13 hours before the northward equinox on the same date.

Credit: David Blanchflower. — An extremely thin crescent Moon against a low contrast twilight sky. Credit and copyright: David Blanchflower.

Such are the curious vagaries of the juxtaposition of the lunar cycle on our modern day Gregorian calendar. Unfortunately, this doesn’t mean you’ll win the lottery or be lucky in love: any Earthly woes are strictly your own affairs to deal with, Black Moon or no. Continue reading “Black Moon: Why the New Moon on February 18th is Special”

February 18, 2015December 23, 2015 by Bob King

When Light Just Isn’t Fast Enough

A pile of Skittles candy seen at rest. Credit: PiccoloNamek

Take a speed of light trip across the solar system starting at the Sun

We’ve heard it over and over. There’s nothing faster than the speed of light. Einstein set the speed limit at 186,000 miles per second (299,792 km/sec). No material object can theoretically travel faster. For all practical purposes, only light is lithe enough to travel at the speed of light.

Moving in such haste, a beam of light can zip around the Earth 8 times in just one second. A trip to the moon takes just 1.3 seconds. Fast for sure but unfortunately not fast enough. Hit play on the video and you’ll soon know what I mean. The view begins at the Sun and travels outward into the solar system at the speed of light.

Planet           Distance in AU            Travel time
....................................................................
Mercury              0.387        193.0 seconds   or    3.2 minutes
Venus                0.723        360.0 seconds   or    6.0 minutes
Earth                1.000        499.0 seconds   or    8.3 minutes
Mars                 1.523        759.9 seconds   or   12.6 minutes
Jupiter              5.203       2595.0 seconds   or   43.2 minutes
Saturn               9.538       4759.0 seconds   or   79.3 minutes
Uranus              19.819       9575.0 seconds   or  159.6 minutes
Neptune             30.058      14998.0 seconds   or    4.1 hours
Pluto               39.44       19680.0 seconds   or    5.5 hours
...................................................................

Distances and light times to the planets and Pluto (from Alphonse Swinehart)

You might first think that moving that fast will get us across the orbits of the eight planets in a hurry. I shouldn’t have been surprised, but I found myself already getting impatient by the time Mercury flew by … after 3.2 minutes. Earth was still 5 minutes away and Jupiter another 40! That’s why the video cuts off at Jupiter – no one would stick around for Pluto’s appearance 5 1/2 hours later.

As the video tediously but effectively demonstrates we live in a solar system where a few planets are separated by vast spaces. Not even light is fast enough to satisfy the human need for speed. But just to put things in perspective, the fastest current human-made objects is NASA’s Voyager I spacecraft, which recently reached interstellar space traveling at 38,000 mph (17 km/sec) or nearly 18,000 times slower than light speed.

Let’s explore further. Any material object, a Skittle for instance, moving that fast would become infinitely massive. Why? You’d need an infinite amount of energy to accelerate the Skittle to the exact speed of light. Since matter and energy are two faces of the same coin, all that energy creates an infinitely massive Skittle. Sweet revenge if there ever was.

You can however accelerate the pill-like candy to 99.9999% light speed with a finite if incredibly large amount of energy. Einstein’s cool with that. Here’s the weird thing. If you were travelling along at the speed of light it would look like a perfectly normal piece of candy, but if you were to look at it from the outside world, the sugary treat would be the entire universe. Both viewpoints are equally valid, and that’s the essence of relatively.

Wave-particle duality of light

To better imagine a day in the life of a photon, let’s go along for the ride. Photons are the particle form of light, which for a long time was only understood as waves of electromagnetic energy. In the weirdness of quantum world, light is both a particle and a wave. From our perspective, a photon rip by at 186,000 miles per second, but to the photon itself, the world stands still and time stops. Photons are everywhere at once. Omnipresent. No time passes for them.

In relativity theory, the movement of anything is defined entirely from an observer’s point of view. From the photon’s perspective, it’s at rest. From ours, it’s moving across time and space. We all have our own “coordinate frame”, so that wherever we are, we’re at rest. That’s relativity for you – all frames are equally valid.

Let say you’re in a plane. That sad bag of pretzels you were just handed is at rest because it’s in your coordinate frame. The person next to you is likewise at rest (and hopefully not snoring). Even the plane’s at rest. According to Einstein, it’s just as valid to picture the world outside the airplane window moving while the plane itself remains at rest. Next time you fly, close your eyes once the plane reaches altitude and a constant speed. You’ll hear the noise of engines, but there’s no way to know you’re actually moving.

Diagram showing how an object (sphere) contracts in the direction of motion as its speed increases. At far left, its velocity (V) is 0.3 times the speed of light. Credit: Askamathematician.com

Relativity also predicts that objects contract in the direction of their motion. Strange as it sounds, this has been verified by many experiments. The faster things travel, the more they contract.

The effect doesn’t become noticeable until an object approaches light speed, but the Apollo 10 service and crew modules reached a velocity of 0.0037% the speed of light. From the perspective of someone on the ground, the 11.03-meter-long module shrank by approximately 7.5 nanometers, an exceedingly tiny but measurable amount. (A sheet of paper is 100,000 nanometers thick). Likewise, distances contract, bottoming out at zero at light speed.

Length contraction occurs because a stationary observer sees a speedy spaceship traveler’s time tick by more slowly. Since light is measured in time units – light seconds, light years – in order for the two to agree on the speed of light (a constant across the universe) the traveler’s “ruler” has to be shorter. And it really is from your stationary perspective if you could somehow peer inside the ship. Traveling at 10% light speed, a 200-foot spaceship shrinks to 199 feet. At 86.5%, it’s 100 feet or half the size and at 99.99% only 3 feet!

We’ve traveled far today – sitting quietly in our frames of reference.

February 18, 2015January 6, 2016 by Elizabeth Howell

Interesting Facts About The Moon

A full Moon flyby, as seen from Paris, France. Credit and copyright: Sebastien Lebrigand.

Shining like a beacon in Earth’s sky is the Moon. We’ve seen so much of it in our lifetimes that it’s easy to take it for granted; even the human landings on the Moon in the 1960s and 1970s were eventually taken for granted by the public.

Fortunately for science, we haven’t stopped looking at the Moon in the decades after Neil Armstrong took his first step. Here are a few things to consider about Earth’s closest big neighbor.

Continue reading “Interesting Facts About The Moon”

February 17, 2015December 23, 2015 by Elizabeth Howell

Interesting Facts About Pluto

Artist's impression of New Horizons' encounter with Pluto and Charon. Credit: NASA/Thierry Lombry

As the New Horizons spacecraft gets closer and closer to Pluto in advance of its July 2015 flyby, it manages to and gathers more and more information. As a result, we learning more about the dwarf planet on an almost regular basis.

Pluto is now becoming more to the public than just the planet that no longer was; before long, we’ll be able to understand much about its atmosphere, its moons and how it fits into the story of the Solar System’s history. Here are some of the most interesting things we know about Pluto so far.

1. Its definition of “dwarf planet” is controversial:
Back in 2006, the International Astronomical Union deemed Pluto is a dwarf planet and not a planet. The reasoning came after a few other objects were discovered far out in the Solar System that are close to Pluto’s size. That said, the principal investigator for New Horizons, Alan Stern, does not agree with the definition. At the time of the vote, he pointed out that the IAC’s definition of planet was not completely true of any larger body; for example, Earth does not clear the entire neighborhood of debris, which is one of the parts of the definition.

2. Pluto has several moons:
For decades, astronomers knew of Pluto and its moon, Charon. The two are so close in size that some people considered the system a double planet, but now that’s thrown in doubt with the dwarf planet designation. In any case, in the last decade humanity has discovered several more moons as telescope resolution and observing techniques improved. The other moons are called Nix, Hydra, Kerberos and Styx. For now we don’t know much about these smaller moons because it’s so difficult to resolve features on their tiny size.

*HST Image of Pluto-Charon system. Also shown are Nix and Hydra. Image Credit: NASA/ESA*

3. Charon might have an ocean on it:
It seems unbelieveable that Charon could have an ocean given it’s so far away from the Sun, but at least one study suggests that it could be possible. Essentially, the tidal force imparted by Pluto’s gravity early in Charon’s history could have stretched the moon’s insides and warmed them up enough to create liquid. That said, it’s also possible that the ocean is now frozen as Charon’s orbit is not as eccentric as it was in the past.

4. Charon’s formation could have spawned the other moons:
As with our own Moon, some scientists believe Charon was created after a large object smashed into Pluto billions of years ago. This would have created a chain of debris circling the dwarf planet, which eventually coalesced into Charon. However, the other moons we know of near Pluto have almost exact resonances with Charon. This suggests that they also formed from the debris, one study says.

This "movie" of Pluto and its largest moon, Charon b yNASA's New Horizons spacecraft taken in July 2014 clearly shows that the barycenter -center of mass of the two bodies - resides outside (between) both bodies. The 12 images that make up the movie were taken by the spacecraft’s best telescopic camera – the Long Range Reconnaissance Imager (LORRI) – at distances ranging from about 267 million to 262 million miles (429 million to 422 million kilometers). Charon is orbiting approximately 11,200 miles (about 18,000 kilometers) above Pluto's surface. (Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute) — *Footage of Charon, captured by NASA’s New Horizons spacecraft, taken in July 2014. Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute*

5. Pluto has an atmosphere:
Pluto is a tiny world, but like the Moon and Mercury it does have a very tenuous atmosphere that is called an “exosphere.” Astronomers first spotted signs of it in 1985. As Pluto passed in front of a star, they saw the star very slightly dim before Pluto completely blocked the star. The composition of this atmosphere is mostly made up of nitrogen and methane, and it freezes when Pluto is furthest from the Sun.

6. Pluto can get closer to the Sun than Neptune:
We used to think of Pluto as the furthest planet from the Sun, but in reality its orbit is so eccentric that it comes closer to the Sun than Neptune. According to NASA, its average distance from the Sun is 39.5 astronomical units (Earth-Sun distances), but it can come as close as 29.7 AU and as far away as 49.7 AU. It was last “inside” Neptune’s orbit between 1979 and 1999.

Pluto's surface as viewed from the Hubble Space Telescope in several pictures taken in 2002 and 2003. Though the telescope is a powerful tool, the dwarf planet is so small that it is difficult to resolve its surface. Astronomers noted a bright spot (180 degrees) with an unusual abundance of carbon monoxide frost. Credit: NASA — Pluto’s surface as viewed from the Hubble Space Telescope in several pictures taken in 2002 and 2003. Though the telescope is a powerful tool, the dwarf planet is so small that it is difficult to resolve its surface. Astronomers noted a bright spot (180 degrees) with an unusual abundance of carbon monoxide frost. Credit: NASA

7. Astronomers think Pluto looks a lot like Neptune’s moon, Triton:
Let’s be clear that Triton and Pluto have very different histories; for example, Triton was likely captured by Neptune long ago, an event that drastically altered its surface and its insides. But Pluto and Triton likely do have some similarities: the frozen volatiles (elements with low boiling points), the faint nitrogen atmospheres, and their similar composition of ice and rock. Scientists are pulling out old Voyager 2 pictures to make the comparisons as Pluto pictures arrive from New Horizons.

8. Pluto could have a ring system:
It’s not a guarantee, but at least one research team suggests that debris floating around Pluto could coalesce into a faint ring system. This wouldn’t be a large surprise, by the by, as we already know of at least one asteroid that has rings — so it is possible. Researchers on New Horizons will also be on the lookout for more moons and interesting features on Pluto’s surface such as cracks.

We have many interesting articles on Pluto here at Universe Today. For example, here’s Is There Life on Pluto?, Why Pluto is No Longer a Planet? and How Long Does it Takes to Get to Pluto?

And for more information on the New Horizons mission, check out our articles, New Horizons Exits Safe Mode and Pluto’s Time to Shine Just Hours Away. And be sure to check out NASA’s New Horizons mission homepage.

February 17, 2015December 23, 2015 by Tim Reyes

Nobody Knows What These Mysterious Plumes are on Mars

In the Journal Nature, astronomers deliver an exhaustive study of limited albeit high quality ground-based observations of Mars and come up short. A Martian mystery remains. What caused the extremely high-altitude plumes on Mars? (Credit: Nature, Sánchez-Lavega, A. et al. Feb 16, 2015, Figures 1a, 2)

In March 2012, amateur astronomers began observing unusual clouds or plumes along the western limb of the red planet Mars. The plumes, in the southern hemisphere rose to over 200 kilometers altitude persisting for several days and then reappeared weeks later.

So a group of astronomers from Spain, the Netherlands, France, UK and USA have now reported their analysis of the phenomena. Their conclusions are inconclusive but they present two possible explanations.

Was dust lofted to extreme altitudes or ice crystals transported into space.? Hubble images show cloud formations (left) and the effects of a global dust storm on Mars (Credit: NASA/Hubbble)

Mars and mystery are synonymous. Among Martian mysteries, this one has persisted for three years. Our own planet, much more dynamic than Mars, continues to raise new questions and mysteries but Mars is a frozen desert. Frozen in time are features unchanged for billions of years.

An animated sequence of images taken by Wayne Jaeschke on March 20, 2012 showing the mystery plume over the western limb of the red planet (upper right). South is up in the photo. (Credit: W. Jaeschke)

In March 2012, the news of the observations caught the attention of Universe Today contributing writer Bob King. Reported on his March 22nd 2012 AstroBob blog page, the plumes or clouds were clear to see. The amateur observer, Wayne Jaeschke used his 14 inch telescope to capture still images which he stitched together into an animation to show the dynamics of the phenomena.

Now on February 16 of this year, a team of researchers led by Agustín Sánchez-Lavega of the University of the Basque Country in Bilbao, Spain, published their analysis in the journal Nature of the numerous observations, presenting two possible explanations. Their work is entitled: “An Extremely high-altitude plume seen at Mars morning terminator.”

Map from the Mars Global Surveyor of the current magnetic fields on Mars. Credit: NASA/JPL

The phenomena occurred over the Terra Cimmeria region centered at 45 degree south latitude. This area includes the tiger stripe array of magnetic fields emanating from concentrations of ferrous (iron) ore deposits on Mars; discovered by the Mars Global Surveyor magnetometer during low altitude aerobraking maneuvers at the beginning of the mission in 1998. Auroral events have been observed over this area from the interaction of the Martian magnetic field with streams of energetic particles streaming from the Sun. Sánchez-Lavega states that if these plumes are auroras, they would have to be over 1000 times brighter than those observed over the Earth.

Auroras photographed from The International Space Station. The distinct Manicouagan impact crater is seen in northern Canada. Terrestial aurora exist at altitudes of 100 km (60 miles) (Credit: NASA)

The researchers also state that another problem with this scenario is the altitude. Auroras over Mars in this region have been observed up to 130 km, only half the height of the features. In the Earth’s field, aurora are confined to ionospheric altitudes – 100 km (60 miles). The Martian atmosphere at 200 km is exceedingly tenuous and the production of persistent and very bright aurora at such an altitude seems highly improbable.

The duration of the plumes – March 12th to 23rd, eleven days (after which observations of the area ended) and April 6th to 16th – is also a problem for this explanation. Auroral arcs on Earth are capable of persisting for hours. The Earth’s magnetic field functions like a capacitor storing charged particles from the Sun and some of these particles are discharged and produced the auroral oval and arcs. Over Mars, there is no equivalent capacitive storage of particles. Auroras over Mars are “WYSIWYG” – what you see is what you get – directly from the Sun. Concentrated solar high energy streams persisting for this long are unheard of.

The second explanation assessed by the astronomers is dust or ice crystals lofted to this high altitude. Again the altitude is the big issue. Martian dust storms will routinely lift dust to 60 km, still only one-third the height of the plumes. Martian dust devils will lift particles to 20 km. However, it is this second explanation involving ice crystals – Carbon Dioxide and Water – that the researchers give the most credence. In either instance, the particles must be concentrated and their reflectivity must account for the total brightness of the plumes. Ice crystals would be more easily transported to these heights, and also would be most highly reflective.

The paper also considered the shape of the plumes. The remarkable quality of modern amateur astrophotography cannot be overemphasized. Also the duration of the plumes was considered. By local noon and thereafter they were not observed. Again, the capabilities tendered by ground-based observations were unique and could not be duplicated by the present set of instruments orbiting Mars.

A Martian dust devil roughly 12 miles (20 kilometers) high was captured on Amazonis Planitia region of Mars, March 14, 2012 by the HiRISE camera on NASA's Mars Reconnaissance Orbiter. The plume is little more than three-quarters of a football field wide (70 yards, or 70 meters). (Image credit: NASA/JPL-Caltech/UA) — A Martian dust devil roughly 12 miles (20 kilometers) high was captured on Amazonis Planitia region of Mars, March 14, 2012 by the HiRISE camera on NASA’s Mars Reconnaissance Orbiter. The plume is little more than three-quarters of a football field wide (70 yards, or 70 meters). (Image credit: NASA/JPL-Caltech/UA)

Still too many questions remain and the researchers state that “both explanations defy our present understanding of the Mars’ upper atmosphere.” By March 20th and 21st, the researchers summarized that at least 18 amateur astronomers observed the plume using from 20 to 40 cm telescopes (8 to 16 inch diameter) at wavelengths from blue to red. At Mars, the Mars Color Imager on MRO (MARCI) could not detect the event due to the 2 hour periodic scans that are compiled to make global images.

Of the many ground observations, the researchers utilized two sets from the venerable astrophotographers Don Parker and Daiman Peach. While observations and measurements were limited, the researchers analysis was exhaustive and included modeling assuming CO2, Water and dust particles. The researchers did find a Hubble observation from 1997 that compared favorably with the 2012 events and likewise modeled that event for comparison. However, Hubble results provided a single observation and the height estimate could not be narrowly constrained.

Explanation of these events in 2012 are left open-ended by the research paper. Additional observations are clearly necessary. With increased interest from amateurs and continued quality improvements plus the addition of the Maven spacecraft suite of instruments plus India’s Mars Orbiter mission, observations will eventually be gained and a Martian mystery solved to make way for yet another.

References:

An Extremely High-Altitude Plume seen at Mars’ Morning Terminator, Journal Nature, February 16, 2015

Amateur astronomer photographs curious cloud on Mars, AstroBob, March 22, 2012

February 17, 2015April 26, 2016 by David Dickinson

Catch a ‘Conjunction Triple Play’ on February 20th as the Moon Meets Venus & Mars

The Moon passes Mars and Venus last month... this week's pass is much closer! (Photo by Author).

Fear not, the chill of late February. This Friday gives lovers of the sky a reason to brave the cold and look westward for a spectacular close triple conjunction of the planets Mars, Venus and the waxing crescent Moon.

This week’s New Moon is auspicious for several reasons. We discussed the vagaries of the Black Moon of February 2015 last week, and the lunacy surrounding the proliferation of the perigee supermoon. And Happy ‘Year of the Goat’ as reckoned on the Chinese luni-solar calendar, as this week’s New Moon marks the start of the Chinese New Year on February 19^th. Or do you say Ram or Sheep? Technical timing for the New Moon is on Wednesday, February 18^th at 23:47 UT/6:47 PM EST, marking the start of lunation 1140. The next New Moon on March 20^th sees the start of the first of two eclipse seasons for 2015, with a total solar eclipse for the high Arctic. More on that next month!
Continue reading “Catch a ‘Conjunction Triple Play’ on February 20th as the Moon Meets Venus & Mars”

February 16, 2015December 23, 2015 by Elizabeth Howell

Interesting Facts About the Solar System

Artist's conception of the solar system, often used in the Eyes on the Solar System 3D Simulator. Credit: NASA

While most of us are stuck on planet Earth, we’re lucky enough to have a fairly transparent atmosphere. This allows us to look up at the sky and observe changes. The ancients noticed planets wandering across the sky, and occasional visitors such as comets.

Thousands of years ago, most thought the stars ruled our destiny. Today, however, we can see science at work in the planets, asteroids and comets close to home. So why take a look at the Solar System? What can it teach us?

1. The definition of a planet and a moon is fuzzy.

We all know of that famous International Astronomical Union vote in 2006 where Pluto was demoted from planethood into a newly created class called “dwarf planets.” But the definition drew controversy among some, who pointed out that no planet — dwarf or otherwise — perfectly clears the neighborhood in its orbit of asteroids, for example. Moons are considered to orbit around planets, but that doesn’t cover situations such as moons orbiting asteroids or double planets, for example. Goes to show you the Solar System requires more study to figure this out.

2. Comets and asteroids are leftovers.

No, we don’t mean leftovers to eat — we mean leftovers of what the Solar System used to look like. So while it’s easy to get distracted by the weather and craters and prospects for life on planets and moons, it’s important to remember that we must also pay attention to the smaller bodies. Comets and asteroids, for example, could have brought organics and water ice to our own planet — providing what we need for life.

Four images of Comet 67P/Churyumov–Gerasimenko taken on Nov. 30, 2014 by the orbiting Rosetta spacecraft. Credit: ESA/Rosetta/NAVCAM – CC BY-SA IGO 3.0

3. The planets are all on the same “plane” and orbit in the same direction.

When considering the IAU’s definition of planets, we come up with eight: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune. You’ll notice that these bodies tend to follow the same path in the sky (called the ecliptic) and that they orbit the Sun in the same direction. That supports the leading theory for the Solar System’s formation, which is that the planets and moons and Sun formed from a large gas and dust cloud that condensed and spun.

4. We’re nowhere near the center of the galaxy.

We can measure vast distances across the universe by looking at things such as “standard candles” — a type of exploding stars that tend to have the same luminosity, which makes it easier to predict how far away they are from us. At any rate, looking at our neighborhood, we’ve been able to figure out we’re nowhere near the Milky Way galaxy’s center. We’re about 165 quadrillion miles away from the center supermassive black hole, NASA says, which is probably a good thing.

A still photo from an animated flythrough of the universe using SDSS data. This image shows our Milky Way Galaxy. The galaxy shape is an artist’s conception, and each of the small white dots is one of the hundreds of thousands of stars as seen by the SDSS. Image credit: Dana Berry / SkyWorks Digital, Inc. and Jonathan Bird (Vanderbilt University) — A still photo from an animated flythrough of the universe using SDSS data. This image shows our Milky Way Galaxy. The galaxy shape is an artist’s conception, and each of the small white dots is one of the hundreds of thousands of stars as seen by the SDSS. Image credit:
Dana Berry / SkyWorks Digital, Inc. and Jonathan Bird (Vanderbilt University)

5. But the Solar System is bigger than you think.

Beyond the orbit of Neptune (the furthermost planet), it takes a long time to leave the Solar System. In 2012, some 35 years after leaving Earth on a one-way trip to the outer solar Solar System, Voyager 1 passed through the area where the Sun’s magnetic and gas environment gives way to that of the stars, meaning that it is interstellar space. That was an astounding 11 billion miles (17 billion kilometers) away from Earth, or roughly 118 equivalent Earth-sun distances (astronomical units).

6. The Sun is hugely massive.

Just how massive? 99.86% of the Solar System’s mass is in our local star, which goes to show you where the real heavyweight is. The Sun is made up of hydrogen and helium, which shows you that these gases are far more abundant in our neighborhood (and the Universe generally) than the rocks and metals we are more familiar with here on Earth.

Solar prominences and filaments on the Sun on September 18, 2014, as seen with a hydrogen alpha filter. Credit and copyright: John Chumack/Galactic Images.

7. We haven’t finished searching for life here.

So we know for sure that life exists on Earth, but that doesn’t rule out a whole bunch of other places. Mars had water flowing on it in the ancient past, and has frozen water at its poles — making astrobiologists think it might be a good candidate. There also are a range of icy moons that could have oceans with life below the surfaces, such as Europa (at Jupiter) and Enceladus (at Saturn). There’s also the interesting world of Titan, which has “prebiotic chemistry” — chemistry that was a precursor to life — on its surface.

8. We can use the Solar System to better understand exoplanets.

Exoplanets are so far away, and so small in our telescopes, that it’s difficult to see very much detail in their atmospheres. But by looking at the chemistry of Jupiter, for example, we can make some predictions about gas giants further afield. If we look at Earth and Neptune, we can get a better sense of the range of planetary sizes on which life could exist (those “super-Earths” and “mini-Neptunes” you sometimes hear mentioned.) And even looking at where water freezes in our own Solar System can help us better understand the ice line in other locations.

We have written articles about the solar system for Universe Today. Here are facts about the planets in the Solar System. We have recorded a whole series of podcasts about the Solar System at Astronomy Cast. Check them out here.