Artist's conception of GJ 1214 b passing across its host star, as viewed in blue light. Credit: NAOJ
Playing with the filters on a telescope can show us amazing things. In a recent case, Japanese astronomers looked at the star Gilese 1214 in blue light and watched its “super-Earth” planet (Gliese 1214 b, or GJ 1214 b) passing across the surface from the viewpoint of Earth. The result — a probable detection of water in the planet’s atmosphere.
Observations with the Subaru Telescope using a blue filter revealed the atmosphere does not preferentially scatter any light. If the Rayleigh scattering had been observed, this would have shown hydrogen in the atmosphere, researchers said. (On Earth, Rayleigh scattering of the atmosphere makes the sky blue.)
“When combined with the findings of previous observations in other colors, this new observational result implies that GJ 1214 b is likely to have a water-rich atmosphere,” stated the National Astronomical Observatory of Japan.
The planet is an ideal candidate for exoplanet observations because it is relatively close to Earth (40 light years away) and is about 2.7 times the size of our planet, allowing for possible comparisons between the worlds.
Three images showing the relationship between the atmosphere’s composition and the transmitted colors of light. Top: Hydrogen-dominated atmospheres see much of the blue light scattered, meaning that transits become more visible in blue light than red light. Middle: Atmospheres with less hydrogen scatter blue wavelengths more weakly. Bottom: Cloud-covered planets make it more difficult for light to make its way up through the atmosphere, even if the atmosphere is dominated by hydrogen. Credit: NAOJ
There’s still some debate over whether “super-Earths” are closer in nature to Earth or to Uranus or Neptune (each about four times Earth’s diameter), requiring scientists to scrutinize that class of exoplanets to learn more about their properties.
One area under investigation is where the super-Earths form. It is believed that planets arise out of a protoplanetary disk, or cloud of gas, ice and debris that surrounds a young star at the beginning of its life. Hydrogen is a big part of this disk, as well as water ice beyond the “snow line“, or the region in a planetary system where waning heat makes it possible for ice to form.
“Findings about where super-Earths have formed and how they have migrated to their current orbits point to the prediction that hydrogen or water vapor is a major atmospheric component of a super-Earth,” NAOJ stated. “If scientists can determine the major atmospheric component of a super-Earth, they can then infer the planet’s birthplace and formation history.”
The team acknowledges it’s still possible there is hydrogen in GJ 1214 b’s atmosphere, but add their findings do corroborate with past ones suggesting water.
While taking a look at more than a hundred planetary nebulae in our galaxy’s central bulge, astronomers using the NASA/ESA Hubble Space Telescope and ESO’s New Technology Telescope have found something rather incredible. It would appear that butterfly-shaped planetary nebulae – despite their differences – are somehow mysteriously aligned!
We know that stars similar to our Sun end their lives shedding their outer layers into space. Like a reptile’s intact skin casing, this stellar material forms a huge variety of shapes known as planetary nebulae. One of the more common forms is bipolar – which creates a bowtie or butterfly shape around the progenitor star.
Like snowflakes, no two planetary nebulae are exactly alike. They are created in different places, under different circumstances and have very different characteristics. There is no way that any of these nebulae, nor the responsible stars that formed them, could have interacted with other planetary nebulae. However, according to a new study done by astronomers from the University of Manchester, UK, there seems to be a rather incredible coincidence… A surprising number of these stellar shells are lining up the same way from our galactic point of view.
“This really is a surprising find and, if it holds true, a very important one,” explains Bryan Rees of the University of Manchester, one of the paper’s two authors. “Many of these ghostly butterflies appear to have their long axes aligned along the plane of our galaxy. By using images from both Hubble and the NTT we could get a really good view of these objects, so we could study them in great detail.”
According to the news release, the astronomers observed 130 planetary nebulae in the Milky Way’s central bulge. They identified three different types, and closely examined their characteristics and appearance.
“While two of these populations were completely randomly aligned in the sky, as expected, we found that the third — the bipolar nebulae — showed a surprising preference for a particular alignment,” says the paper’s second author Albert Zijlstra, also of the University of Manchester. “While any alignment at all is a surprise, to have it in the crowded central region of the galaxy is even more unexpected.”
What causes a planetary nebula to take on a particular shape? For some time, astronomers figured their appearance may have been affected by the rotation of the star system in which they form. Many factors could contribute, such as whether or not the spawning star is a binary, or if it has a planetary system. Both of these factors could help mold the eventual outcome of the shed stellar material. However, bipolar planetary nebulae are the most extreme. Astronomers theorize their shapes are the product of jets blowing mass from the binary system perpendicular to the orbit.
“The alignment we’re seeing for these bipolar nebulae indicates something bizarre about star systems within the central bulge,” explains Rees. “For them to line up in the way we see, the star systems that formed these nebulae would have to be rotating perpendicular to the interstellar clouds from which they formed, which is very strange.”
We accept the fact that the properties of the parent stars are the biggest contributor to a planetary nebula’s shape, but this new information gives an enigmatic edge to the final outcome. Not only is each unique, but the Milky Way itself adds even more complexity. The entire central bulge rotates around the galactic center, and this bulge may have considerably more influence than we expected… the influence of its magnetic fields. The researchers suggest this “orderly behavior of the planetary nebulae” may have occurred because a strong magnetic field was present when the bulge formed. Since planetary nebulae nearer to us don’t line up in the same orderly fashion, it would be logical to assume these magnetic fields were much stronger when our galaxy first formed.
“We can learn a lot from studying these objects,” concludes Zijlstra. “If they really behave in this unexpected way, it has consequences for not just the past of individual stars, but for the past of our whole galaxy.”
Illustration of the Kepler spacecraft. Kepler's mission is over, but all of the exoplanets it found still need to be confirmed in follow-up observations. (NASA/Kepler mission/Wendy Stenzel)
Kepler may not be hanging up its planet-hunting hat just yet. Even though two of its four reaction wheels — which are crucial to long-duration observations of distant stars — are no longer operating, it could still be able to seek out potentially-habitable exoplanets around smaller stars. In fact, in its new 2-wheel mode, Kepler might actually open up a whole new territory of exoplanet exploration looking for Earth-sized worlds orbiting white dwarfs.
An international team of scientists, led by Mukremin Kilic of the University of Oklahoma’s Department of Physics and Astronomy, are suggesting that NASA’s Kepler spacecraft should turn its gaze toward dim white dwarfs, rather than the brighter main-sequence stars it was previously observing.
“A large fraction of white dwarfs (WDs) may host planets in their habitable zones. These planets may provide our best chance to detect bio-markers on a transiting ex- oplanet, thanks to the diminished contrast ratio between the Earth-sized WD and its Earth-sized planets. The James Webb Space Telescope is capable of obtaining the first spectroscopic measurements of such planets, yet there are no known planets around WDs. Here we propose to take advantage of the unique capability of the Kepler space- craft in the 2-Wheels mode to perform a transit survey that is capable of identifying the first planets in the habitable zone of a WD.”
– Kilic et al.
Any bio-markers — such as molecular oxygen, O2 — could later be identified around such Earth-sized exoplanets by the JWST, they propose.
Will Kepler be able to find the first Earth-sized exoplanet — or even an exomoon — orbiting a white dwarf? (Illustration of Kepler 22b. Credit: NASA/Ames/JPL-Caltech)
Because Kepler’s precision has been greatly reduced by the failure of a second reaction wheel earlier this year, it cannot accurately aim at large stars for the long periods of time required to identify the minute dips in brightness caused by the silhouetted specks of passing planets. But since white dwarfs — the dim remains of stars like our Sun — are much smaller, any eclipsing exoplanets would make a much more pronounced effect on their apparent luminosity.
In effect, exoplanets ranging from Earth- to Jupiter-size orbiting white dwarfs as close as .03 AU — well within their habitable zones — would significantly block their light, making Kepler’s diminished aim not so much of an issue.
“Given the eclipse signature of Earth-size and larger planets around WDs, the systematic errors due to the pointing problems is not the limiting factor for WDHZ observations,” the team assures in their paper “Habitable Planets Around White Dwarfs: an Alternate Mission for the Kepler Spacecraft.”
Even smaller orbiting objects could potentially be spotted in this fashion, they add… perhaps even as small as the Moon.
The team is proposing a 200-day-long survey of 10,000 known white dwarfs within the Sloan Digital Sky Survey (SDSS) area, and expects to find up to 100 exoplanet candidates as well as other “eclipsing short period stellar and sub-stellar companions.”
“If the history of exoplanet science has taught us anything, it is that planets are ubiquitous and they exist in the most unusual places, including very close to their host stars and even around pulsars… Currently there are no known planets around WDs, but we have never looked at a sufficient number of WDs at high cadence to find them through transit observations.”
NASA’s Ames Research Center made an open call for proposals regarding Kepler’s future operations on August 2. Today is the due date for submissions, which will undergo a review process until Nov. 1, 2013.
Added 9/4: For another take on this, check out Paul Gilster’s write-up on Centauri Dreams.
An ultracold vacuum chamber ran a simulation of the early universe and came up with some interesting findings about how the environment looked shortly after the Big Bang occurred.
Specifically, the atoms clustered in patterns similar to the cosmic microwave background — believed to be the echo of the intense burst that formed the beginning of the universe. Scientists have mapped the CMB at progressively higher resolution using several telescopes, but this experiment is the first of its kind to show how structure evolved at the beginning of time as we understand it.
The Big Bang theory (not to be confused with the popular television show) is intended to describe the universe’s evolution. While many pundits say it shows how the universe came “from nothing”, the concordance cosmological model that describes the theory says nothing about where the universe came from. Instead, it focuses on applying two big physics models (general relativity and the standard model of particle physics). Read more about the Big Bang here.
CMB is, more simply stated, electromagnetic radiation that fills the Universe. Scientists believe it shows an echo of a time when the Universe was much smaller, hotter and denser, and filled to the brim with hydrogen plasma. The plasma and radiation surrounding it gradually cooled as the Universe grew bigger. (More information on the CMB is here.) At one time, the glow from the plasma was so dense that the Universe was opaque, but transparency increased as stable atoms formed. But the leftovers are still visible in the microwave range.
WMAP data of the Cosmic Microwave Background. Credit: NASA
The new research used ultracold cesium atoms in a vacuum chamber at the University of Chicago. When the team cooled these atoms to a billionth of a degree above absolute zero (which is -459.67 degrees Fahrenheit, or -273.15 degrees Celsius), the structures they saw appeared very similar to the CMB.
By quenching the 10,000 atoms in the experiment to control how strongly the atoms interact with each other, they were able to generate a phenomenon that is, very roughly speaking, similar to how sound waves move in air.
“At this ultracold temperature, atoms get excited collectively,” stated Cheng Chin, a physics researcher at the University of Chicago who participated in the research. This phenomenon was first described by Russian physicist Andrei Sakharov, and is known as Sakharov acoustic oscillations.
So why is the experiment important? It allows us to more closely track what happened after the Big Bang.
Atom density is greater at left (the beginning of the experiment) than 80 milliseconds after the simulated Big Bang. Credit: Chen-Lung Hung
The CMB is simply a frozen moment of time and is not evolving, requiring researchers to delve into the lab to figure out what is happening.
“In our simulation we can actually monitor the entire evolution of the Sakharov oscillations,” said Chen-Lung Hung, who led the research, earned his Ph.D. in 2011 at the University of Chicago, and is now at the California Institute of Technology.
Both Hung and Chin plan to do more work with the ultracold atoms. Future research directions could include things such as how black holes work, or how galaxies were formed.
Comet ISON shows a small, compact coma and short, faint tail in this photo made by Krisztian Sarneczky on Aug. 31, 2013. Credit: K. Sárneczky / Konkoly Observatory
OK, you’ve waited patiently for Comet ISON to brighten and reappear in the dawn sky. It has. Now you’re chomping at the bit for a look at it in your telescope. Before you set the alarm and venture into the night, let’s prepare for what to expect. The better you know your target, the easier it will be to find.
Astrophotographer Alfons Diepvens captured this view of ISON on Sept. 1, 2013 through his telescope. Tail length and direction are indicated. Click image to see more his photos of ISON and other recent comets. Credit: Alfons Diepvens
The latest brightness estimates from the amateur comet community place ISON around magnitude 13, bright enough to be within reach of 10-inch (25 cm) and larger telescopes. Alan Hale of Arizona, co-discover of Comet Hale-Bopp, was one of the first to see it. Through his 16-inch (41 cm) reflecting telescope on September 1, he noted the comet as a small object about 0.6 arc minutes across (1 arc minute = 1/30 the diameter of the full moon), brighter in the center and shining faintly at magnitude 13.1. Picture a small, dim patch of glowing mist and you’ve got the picture. Hale’s observing conditions were excellent though he did have to contend with light from the nearby crescent moon. Starting tomorrow morning, the moon will finally be out of the picture.
With the moon out of the sky, now is a great time to hunt for Comet ISON. This map shows the sky as you face east tomorrow morning Sept. 3 around 5 a.m. local time just before the start of morning twilight. The comet is near both Mars and the Beehive Cluster. Stellarium
A sharp-eyed observer under the best skies would expect to see a fuzzy object this faint in a telescope as small as 8-inches (20 cm). Most of us will need something a little bigger. A 10-12 incher (25-30 cm) should do the trick until the comet swells into the 11-12 magnitude range. But you’ll need more than a hefty scope. Key to spotting ISON are good charts, a steady atmosphere for sharp images (shaky air blurs faint objects into invisibility) and catching the comet at the right time. I also encourage you to use averted vision, a great technique for spotting faint sky objects. Instead of staring directly at the comet, look off to the side of its position. That way you allow the comet’s feeble photons to flood your eye’s rod cells, those most sensitive to dim light.
This tighter view shows the comet (on Sept. 3) in relation to the naked eye star Gamma Cancri and the pretty Beehive Cluster in Cancer the Crab. North is up, west to the right. Stellarium
While it now rises around 3-3:30 a.m. local time, you’ll get your best – or only – view once ISON has cleared the light-sucking thick air and haze so common near the horizon. The optimum viewing time occurs shortly before the start of morning twilight when the comet will be about 15 degrees high in the northeastern sky. At mid-northern latitudes,where twilight begins about 1.5 hours before sunrise, that’s around 5 a.m. Did I mention you’d lose a few hours sleep in your pursuit?
Comet ISON’s position plotted for 5 a.m. Central Daylight Time tomorrow through the 10th. Stars are shown to 12th magnitude. Click for larger version. Created with Chris Marriott’s SkyMap Pro program
Lucky for us comet hunters, ISON’s location is easy to find only a few degrees east of the 1st magnitude planet Mars and about 2 degrees north of the familiar Beehive Cluster or M44. The first map shows the general view to get you oriented. The second takes us in closer to show the comet’s relation to the Beehive Cluster, and the third provides a detailed telescopic view with stars plotted to about 12th magnitude. The comet positions on the detailed map are plotted for 5 a.m. CDT. Since ISON moves relatively slowly, those positions will be accurate for a time zone or two either way. If you live significantly farther east or west of the U.S. Central Time Zone, you can interpolate between the tick marks.
It’s good news for skywatchers from here on out as ISON continues to brighten and rise higher in the east with each passing night. A month from now, it should be visible in scopes as small as 6-inches (15 cm). Good luck in your comet quest!
Have a discussion about the origins of the Universe and, ere long, someone will inevitably use the term “the Big Bang” to describe the initial moment of expansion of everything that was to everything that is. But in reality “Big Bang” isn’t a very good term since “big” implies size (and when it occurred space didn’t technically exist yet) and there was no “bang.” In fact the name wasn’t ever even meant to be an official moniker, but once it was used (somewhat derisively) by British astronomer Sir Fred Hoyle in a radio broadcast in 1949, it stuck.
Unfortunately it’s just so darn catchy.
This excellent video from minutephysics goes a bit more into depth as to why the name is inaccurate — even though we’ll likely continue using it for quite some time. (Thanks to Sir Hoyle.)
And you have to admit, a television show called “The Everywhere Stretch Theory” would never have caught on. Bazinga!
Mars on September 8th. (Created by the author using Stellarium).
Launch season for Mars missions is almost upon us once again.
This is a time when spacecraft can achieve an optimal trajectory to reach the Red Planet, expending a minimal amount of fuel and taking the shortest period of time. This window of opportunity, which opens once every two years, always opens up about six months prior to Martian opposition.
For you stargazers, this is also the best time to observe the Red Planet as it makes its closest approach to Earth. And no, it won’t appear as large as a Full Moon, but it will make for a fine telescopic target.
During the last launch window in 2011-12, Mars Curiosity made the journey, and Russia’s Phobos-Grunt tried. Hey, it’s a tough business, this spaceflight thing. This time around, The Indian Space Research Organization (ISRO) hopes to launch its first ever interplanetary spacecraft, with its Mars Orbiter Mission departing on October 18th. NASA is also sending its Mars Atmosphere Volatile EvolutioN mission known as MAVEN to study the atmosphere of the Red Planet.
Opposition next occurs on April 8th, 2014, but the start of launch season always finds Mars emerging high to the east at dawn. Starting next week, Mars has some interesting encounters that are worth checking out as a prelude to the upcoming opposition season.
The planet Mars shines at +1.6 magnitude and is about 4” in size in September. This is a far cry from its maximum size of 15.1” that it will achieve next spring, and its grandest maximum size of 25.1” that it reached in 2003. All oppositions of Mars are not created equal, because of the planet’s 9.3% eccentric orbit.
But the good news is, we’re trending towards a better series of oppositions, which follow a roughly 15 year cycle. In 2018, we’ll see an opposition nearly as good as the 2003 one, with Mars appearing 24.1” in size. This is also the time frame that Dennis Tito wants to launch his crewed Mars 2018 flyby.
But back to the present. The action starts on September 2nd when the waning crescent Moon passes 6.1 degrees SSW of Mars.
Mars is currently in the constellation Cancer, and will actually transit (pass in front of) the open star cluster known as the Beehive or Messier 44, standing only 0.23 degrees from its center on September 8th. M44 is 1.5 degrees in size, and this presents an outstanding photo-op.
The path of Mars through the beehive cluster from September 3rd through September 12th. (Created in Starry Night; Image courtesy of Starry Night Education).
At high power, you might just be able to catch the real time motion of Mars against the background stars of M44. Mars currently rises three hours before the Sun, giving you a slim window to accomplish this feat.
Mars is also in the midst of a series of transits of the Beehive Cluster, with one occurring every other year. Mars last crossed M44 on October 1st, 2011. The next time you’ll be able to spy this same alignment won’t be until August 20th, 2015.
But another cosmic interloper may photo-bomb Mars in September.
We’re talking about none other than Comet C/2012 S1 ISON, the big wildcard event of the season. Comet ISON is just peeking out from behind the Sun now, and dedicated amateurs have already managed to recover it. “IF” it follows projected light curve predictions, ISON may reach binocular visibility of greater than +10th magnitude by October 1st and may breech naked eye visibility by early November.
ISON approaches within two degrees of Mars on September 27th. Its closest apparent approach is will be on Oct 18th at a minimum separation of 0.89 degrees, just over the size of a Full Moon. How bright ISON will actually be at that point is the question of the season. To quote veteran comet hunter David Levy, “Comets are like cats. They have tails, and they do whatever they want.” The closest physical approach of Mars and Comet ISON is on October 1st at 0.07 astronomical units, or 10.4 million kilometres apart. Both will be crossing over from the astronomical constellations of Cancer into Leo in late September.
Comet ISON and Mars looking east on the morning of September 27th. (Created in Starry Night; Image courtesy of Starry Night Education).
Mars gets another close shave from a comet next year, when Comet C/2013 A1 Siding Spring passes 123,000 kilometres from Mars on October 19th, 2014. Interestingly, MAVEN will be arriving just a month prior to this if it departs Earth at the start of its 21 day window. Engineers have noted that an increase in cometary dust may be a concern for the newly arrived spacecraft during insertion into Martian orbit.
MAVEN Principal Investigator Bruce Jakosky notes that the first concern is the safety of the spacecraft, the second is studies of Mars, and the third is, just perhaps, to carry out observations of the comet.
Look for more information on Universe Today about the Martian cometary flybys as each event gets closer.
September is a great time to begin observations of the Red Planet. Usually, 8” seconds in diameter is the threshold that is frequently quoted for the first surface features (usually to polar ice caps) to become apparent, but we’re already seeing astro-imagers getting detailed images of Mars, right now.
Be sure to follow Mars on its trek across the September dawn skies as robotic explorers prepare to embark on their epic journeys!
X-ray and infrared image of Sgr A*, the supermassive black hole in the center of the Milky Way
Like most galaxies, our Milky Way has a dark monster in its middle: an enormous black hole with the mass of 4 million Suns inexorably dragging in anything that comes near. But even at this scale, a supermassive black hole like Sgr A* doesn’t actually consume everything that it gets its gravitational claws on — thanks to the Chandra X-ray Observatory, we now know that our SMB is a sloppy eater and most of the material it pulls in gets spit right back out into space.
(Perhaps it should be called the Cookie Monster in the middle.*)
New Chandra images of supermassive black hole Sagittarius A*, located about 26,000 light-years from Earth, indicate that less than 1% of the gas initially within its gravitational grasp ever reaches the event horizon. Instead, much of the gas is ejected before it gets near the event horizon and has a chance to brighten in x-ray emissions.
The new findings are the result of one of the longest campaigns ever performed with Chandra, with observations made over 5 weeks’ time in 2012.
“This new Chandra image is one of the coolest I’ve ever seen,” said study co-author Sera Markoff of the University of Amsterdam in the Netherlands. “We’re watching Sgr A* capture hot gas ejected by nearby stars, and funnel it in towards its event horizon.”
As it turns out, the wholesale ejection of gas is necessary for our resident supermassive black hole to capture any at all. It’s a physics trade-off.
“Most of the gas must be thrown out so that a small amount can reach the black hole”, said co-author Feng Yuan of Shanghai Astronomical Observatory in China. “Contrary to what some people think, black holes do not actually devour everything that’s pulled towards them. Sgr A* is apparently finding much of its food hard to swallow.”
X-ray image of Sgr A*
If it seems odd that such a massive black hole would have problems slurping up gas, there are a couple of reasons for this.
One is pure Newtonian physics: to plunge over the event horizon, material captured — and subsequently accelerated — by a black hole must first lose heat and momentum. The ejection of the majority of matter allows this to occur.
The other is the nature of the environment in the black hole’s vicinity. The gas available to Sgr A* is very diffuse and super-hot, so it is hard for the black hole to capture and swallow it. Other more x-ray-bright black holes that power quasars and produce huge amounts of radiation have much cooler and denser gas reservoirs.
Illustration of gas cloud G2 approaching Sgr A* (ESO/MPE/M.Schartmann/J.Major)
Located relatively nearby, Sgr A* offers scientists an unprecedented view of the feeding behaviors of such an exotic astronomical object. Currently a gas cloud several times the mass of Earth, first spotted in 2011, is moving closer and closer to Sgr A* and is expected to be ripped apart and partially consumed in the coming weeks. Astronomers are eagerly awaiting the results.
“Sgr A* is one of very few black holes close enough for us to actually witness this process,” said Q. Daniel Wang of the University of Massachusetts at Amherst, who led the study.
Phobos transiting the Sun as seen by the Mars Curiosity rover on Sol 369. (Credit: NASA/JPL-Caltech/Malin Space Science Systems/Texas A & M University).
It’s always interesting to consider the astronomical goings-on that occur under alien skies.
On August 17th, Curiosity wowed us once again, catching the above sequence of images of the Martian moon Phobos transiting the Sun.
Such phenomena have been captured by the Curiosity, Opportunity and Spirit rovers before, as the twin Martian moons of Deimos & Phobos cross the face of the Sun. But these recent images taken by Curiosity’s right Mastcam pair are some of the sharpest yet.
Orbiting only an average of 6,000 kilometres above the surface of Mars, Phobos is the closest to its primary of any moon in the solar system. It appears about 11 arc minutes in size when directly overhead, about 3 times smaller than our own Moon does from the Earth.
“This event occurred near noon at Curiosity’s location, which put Phobos at its closest point to the rover, appearing larger against the Sun than it would at other times of the day,” Said co-investigator Mark Lemmon of Texas A&M University in a recent press release. “This is the closest to a total eclipse that you can have on Mars.”
Phobos is 40% more distant from an observer standing on the surface of Mars when it is rising above the local horizon than when it is overhead. The Sun is about 20’ arc minutes across as seen from Mars, 66% of its diameter as seen from the Earth.
The sequence above spans only six seconds in duration. You would easily note the apparent motion of Phobos as it drifted by! Also, since Phobos orbits Mars once every 7.7 hours, it actually rises in the west and sets in the east. The Martian day is over three times this span, at 24.6 hours long. Deimos has a more sedate orbit of 30.4 hours in duration.
The twin Moons of Deimos and Phobos were discovered this month back during the opposition of 1877 by Asaph Hall using the United States Naval Observatory’s newly installed 65 centimetre refractor. The moons are just within the grasp of eagle-eyed amateurs near opposition. You’ve got another opportunity to cross these elusive moons off of your life list coming up in the Spring of 2014.
It’s especially captivating that you can make out the irregular “potato shape” of Phobos in the above images. With low orbital inclinations relative to the equator of Mars of 1.1 degrees for Phobos and 0.9 degrees for Deimos, solar transits are not an uncommon occurrence, transpiring somewhere along the Martian surface with every orbit. If Phobos were twice as close to Mars, it would completely cover the Sun in a total solar eclipse. What Curiosity gave us this month is more akin to an annular eclipse with a ragged central shadow. An annular eclipse occurs when the occulting body is too distant to cover the Sun, leaving a bright, shining ring, or annulus.
On the Earth, we live in an epoch where annular eclipses are slightly more common than total solar eclipses, as the Moon currently recedes from us to the tune of 3.8 centimetres a year. About 1.4 billion years from now, the last total solar eclipse will be seen from the Earth. The next purely annular eclipse as seen from Earth occurs on April 29th, 2014 across Australia and the Antarctic.
Conversely, Phobos is in a “death spiral,” meaning that it will one day crash into Mars about 30-50 million years from now. This also means that in about half that time, it will also be large enough to visually cover the Sun when crossing it near local noon. For a brief time far in the future, jagged total solar eclipses will be visible from Mars. That is, if the gravitational field of Mars doesn’t rip Phobos apart before that!
But beyond just aesthetics, these observations serve a scientific purpose as well. These phenomena serve to refine our understanding of the precise positions of Phobos and Deimos and their orbits.
“This one is by far the most detailed image of any Martian lunar transit ever taken, and it is especially useful because it is annular. It was taken closer to the Sun’s center than predicted, so we learned something.”
The track during the August 17th observation was off by about 2-3 kilometres, allowing for a surprise central transit of the Sun as seen from Curiosity’s location.
Both Phobos and Deimos are captured asteroids only 22.2 & 12.6 kilometres across, respectively. Both must be subject to occasional bombardment from meteorites blasted off of the surface of nearby Mars. Sample return missions to Phobos have been proposed. Russia’s ill-fated Phobos-Grunt mission would’ve done just that.
Will humans ever stand on the surface of the Red Planet and witness an annular eclipse of the Sun by Phobos in person? Well, if we make it there by November 10th, 2084, observers placed on the slopes of Elysium Mons will witness just such an event… with a rare transit of Earth and the Moon to boot!:
Arthur C. Clarke wrote of a transit of Earth from Mars that occurred in 1984 in his science fiction short story Transit of Earth.
Hey, I’m marking my calendar for the 2084 event… assuming, of course, my android body is ready by then!
The two main smoke trails left by the Russian meteorite as it passed over the city of Chelyabinsk. Credit: AP Photo/Chelyabinsk.ru
A collision or “near miss” caused melting in the Chelyabinsk meteor before it slammed into Earth’s atmosphere this February, causing damage and injuries to hundreds in the remote Russian region.
A new study, presented at the Goldschmidt Conference in Florence, Italy, says some meteorite fragments’ composition shows strong evidence of heating, which is an indication of interplanetary violence of some sort.
“The meteorite which landed near Chelyabinsk is a type known as an LL5 chondrite, and it’s fairly common for these to have undergone a melting process before they fall to Earth,” stated Victor Sharygin, a researcher from the Sobolev Institute of Geology and Mineralogy in Russia.
“This almost certainly means that there was a collision between the Chelyabinsk meteorite and another body in the solar system, or a near miss with the Sun.”
Chelyabinsk’s size of 59 feet (18 meters) was by no means a very large meteor, but it was enough to cause car alarms to go off and to shatter glass when it exploded over Russia on Feb. 15. Its arrival brought the danger of space rocks once again to public attention.
Model and satellite data show that four days after the bolide explosion, the faster, higher portion of the plume (red) had snaked its way entirely around the northern hemisphere and back to Chelyabinsk, Russia. Image Credit: NASA’s Goddard Space Flight Center Scientific Visualization
Sharygin’s team analyzed several fragments of the meteorites and put them into three groups: light, dark and intermediate. Lights ones were the most abundant. Dark fragments were most commonly found in the area where the meteorite hit the Earth.
While only three of the dark fragments show there was previous melting, the researchers say it’s quite possible that more samples might be available from the public and most notably, from the main portion that is still at the bottom of Chebarkul Lake.
“The dark fragments include a large proportion of fine-grained material, and their structure, texture and mineral composition shows they were formed by a very intensive melting process,” a press release stated.
“This material is distinct from the ‘fusion crust’ – the thin layer of material on the surface of the meteorite that melts, then solidifies, as it travels through the Earth’s atmosphere.”
A “fusion crust” or melting is visible in this fragment of the Chelyabinsk meteorite. Credit: Victor Sharygin
Researchers also spotted “bubbles” in the dark fragments that they consider either “perfect crystals” of oxides, silicates and metal or little spots that are filled up with sulfide or metal.
They also saw platinum-type elements in the crust, which was a surprise as the time it takes for a crust to fuse is too short for platinum to form.
“We think the appearance (formation) of this platinum group mineral in the fusion crust may be linked to compositional changes in metal-sulfide liquid during remelting and oxidation processes as the meteorite came into contact with atmospheric oxygen,” Sharygin stated.
The work is ongoing, and no submission date for a study for publication was disclosed.
