And if you’re interested in looking back, here’s an archive to all the past Carnivals of Space. If you’ve got a space-related blog, you should really join the carnival. Just email an entry to [email protected], and the next host will link to it. It will help get awareness out there about your writing, help you meet others in the space community – and community is what blogging is all about. And if you really want to help out, sign up to be a host. Send an email to the above address.
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!
Closeup of the crescent Moon on October 12, 2012. Credit and copyright: Wes Schulstad
If you want to see detail on the Moon, usually the best times and places to look are when the Moon is in a crescent phase, and near the terminator. These recent images uploaded to Universe Today’s Flickr page will attest to that! Enjoy the views:
Closeup of the Moon showing Endymion, Atlas and the distant Mare Humboldtianum. Credit and copyright: Danny Robb.Lunar terminator mosaic, August 26th 2013. Credit and copyright: Russell Bateman.64% illuminated waning gibbous Moon on August 26, 2013. Credit and copyright: Themagster3 on Flickr.Plato to Aristillus to Aristoteles in Color – 8/26/13. Credit and copyright: Fred Locklear.Waning crescent Moon on August 30, 2013. Credit and copyright: Sculptor Lil on Flickr.
To see more information on each image, click on the image to see it on Flickr.
Want to get your astrophoto featured on Universe Today? Join our Flickr group or send us your images by email (this means you’re giving us permission to post them). Please explain what’s in the picture, when you took it, the equipment you used, etc.
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!
Astronaut Drew Feustel reenters the space station after completing an 8-hour, 7-minute spacewalk at on Sunday, May 22, 2011. He and fellow spacewalker Mike Fincke conducted the second of the four EVAs during the STS-134 mission. Credit: NASA
It’s easy to take the International Space Station for granted. It’s been planned, under construction and/or operated for decades. Humans have occupied it continuously for 4,684 days (close to 13 years) as of today. According to two space policy experts, however, NASA should already be thinking of what it’s going to do next after the station’s current agreement expires in 2020.
Ignoring the deadline, they said, could lead to consequences such as (in one scenario) the end of U.S. government spaceflight altogether.
Below are edited excerpts from two officials from George Washington University’s Elliott School of International Affairs. Scott Pace is its director, and John M. Logsdon is a professor emeritus. They spoke with reporters Thursday (Aug. 29) about the coming NASA budget decision and their views on the agency’s future.
We’d also like to get your feedback on their ideas, so please leave your thoughts in the comments.
Pace: In my view, the House numbers are complying with the Budget Control Act in terms of sequestration numbers. In the Senate, the numbers were not in line with the Budget Control Act, but reflected what the priorities of the authorization committee were … I would argue, and we’ll see if others agree, that the Senate has marginalized themselves in this discussion. The appropriations staff will have the larger say in that, but on the House side, the authorizors and the appropriators will be together because they have discussed what their priorities were.”
Where NASA’s direction comes from:
Logsdon: It’s a residual of 40 years of failure to reach consensus of what the U.S. should be doing in space and particularly, human spaceflight. In the first year and a half of the Nixon administration, he was faced with what to do after Apollo and basically punted. He said, “Let’s develop means, rather than set goals.” The means was the shuttle … The lack of leadership of this administration, which is not much different than most presidents since Nixon and including Nixon, have put us in a situation that is unfortunate, and, as Scott [Pace] says, leads to a lot of drift and lack of sense of purpose.
Pace: [One goal for NASA often is to implement] priorities of decadal surveys from the National Academy of Sciences. Things like the asteroid redirect mission, which will burden portions of the human and science programs, have no decadal survey mention or no larger contribution to the science. It’s another capability-driven-evolution sort of project, with some very basic flaws to it in terms of not providing that long-term sense of strategic purpose.
Concept of NASA spacecraft with Asteroid capture mechanism deployed to redirect a small space rock to a stable lunar orbit for later study by astronauts aboard Orion crew capsule. Credit: NASA.
Logsdon: There’s not enough money to have a robust space exploration program and to use the space station at a $3 billion a year level in 2028. None of the current partners — with a possible exception of Canada — but certainly, Europe and Japan are not enthusiastic about spending money on space station post-2020. They really had to be dragged, their governments had to be dragged, to commit the funds for the extension to 2020. It’s not clear, if there is a decision to go beyond, whether the United States will have its early partners [committed.]
Pace: What happens with other major scientific facilities that NASA has, like the Hubble Space Telescope, is you have a senior review. After you’ve met the initial requirements [of the mission], you ask what is the facility costing me, what am I getting out of it, and make a decision whether to continue. You will see, in anticipation of 2020, you will see the beginnings of a senior review to see what will be in the NASA 2020 budget. It is dependent upon data being created now — the scientific and technical benefits — and where will the benefits flow for plans beyond space station. If there are no plans for human flight beyond space station … the default option is to do the station as long as it is technically capable, but eventually it will be deorbited. And there will be an end to U.S. government spaceflight.
A view of the International Space Station as seen by the last departing space shuttle crew, STS-135. Credit: NASA
If government-funded human spaceflight could end in the United States:
Pace: I can imagine a President presiding over the end of human spaceflight, not as a conscious decision but as an unfortunate accident. Drift is the most dangerous thing for NASA.
Logsdon: Would any President be willing to be that person to end the government-sponsored spaceflight program? I’m not sure the answer is no. It could be that a future President could say we’ve done it and there’s no future reasoning to continue at fairly high expense to continue to do it. But I would speculate the more likely answer, given the industrial and regional interests, is some sort of limping through human spaceflight. It’s more similar than different for the past four decades.
What NASA needs right now:
Logsdon: I’m taking less about the NASA leadership than I am the White House and Congressional leadership. What’s missing is a sense of strategic purpose of the organization, what should it be doing, and that is the job of a national leader. It is enunciating for NASA, as well as other government agencies, for what its long-term and even midterm strategic purpose is in terms of the natinoal interest ought to be.
Pace: [The United States must determine] what is the role of international leadership in space for the United States and to what extent are we willing to make plans for beyond the station. 2020 is not that far away. The focus on NASA right now, with ISS, is utilization. The station has been a great diplomatic success, great technical success, but it’s not clear if it will be a great scientific success.
Are Earthlings really Martians ? Did life arise on Mars first and then journey on meteors to our planet and populate Earth billions of years ago? Earth and Mars are compared in size as they look today.
Are Earthlings really Martians ?
Did life arise on Mars first and then journey on rocks to our planet and populate Earth billions of years ago? Earth and Mars are compared in size as they look today. NASA’s upcoming MAVEN Mars orbiter is aimed at answering key questions related to the habitability of Mars, its ancient atmosphere and where did all the water go. Story updated[/caption]
That’s the controversial theory proposed today (Aug. 29) by respected American chemist Professor Steven Benner during a presentation at the annual Goldschmidt Conference of geochemists being held in Florence, Italy. It’s based on new evidence uncovered by his research team and is sure to spark heated debate on the origin of life question.
Benner said the new scientific evidence “supports the long-debated theory that life on Earth may have started on Mars,” in a statement. Universe Today contacted Benner for further details and enlightenment.
“We have chemistry that (at least at the level of hypothesis) makes RNA prebiotically,” Benner told Universe Today. “AND IF you think that life began with RNA, THEN you place life’s origins on Mars.” Benner said he has experimental data as well.
First- How did ancient Mars life, if it ever even existed, reach Earth?
On rocks violently flung up from the Red Planet’s surface during mammoth collisions with asteroids or comets that then traveled millions of miles (kilometers) across interplanetary space to Earth – melting, heating and exploding violently before the remnants crashed into the solid or liquid surface.
An asteroid impacts ancient Mars and send rocks hurtling to space – some reach Earth. Did they transport Mars life to Earth? Or minerals that could catalyze the origin of life on Earth?
“The evidence seems to be building that we are actually all Martians; that life started on Mars and came to Earth on a rock,” says Benner, of The Westheimer Institute of Science and Technology in Florida. That theory is generally known as panspermia.
To date, about 120 Martian meteorites have been discovered on Earth.
And Benner explained that one needs to distinguish between habitability and the origin of life.
“The distinction is being made between habitability (where can life live) and origins (where might life have originated).”
NASA’s new Curiosity Mars rover was expressly dispatched to search for environmental conditions favorable to life and has already discovered a habitable zone on the Red Planet’s surface rocks barely half a year after touchdown inside Gale Crater.
Furthermore, NASA’s next Mars orbiter- named MAVEN – launches later this year and seeks to determine when Mars lost its atmosphere and water- key questions in the Origin of Life debate.
Curiosity accomplished Historic 1st drilling into Martian rock at John Klein outcrop on Feb 8, 2013 (Sol 182) and discovered a habitable zone, shown in this context mosaic view of the Yellowknife Bay basin taken on Jan. 26 (Sol 169). The robotic arm is pressing down on the surface at John Klein outcrop of veined hydrated minerals – dramatically back dropped with her ultimate destination; Mount Sharp. Credit: NASA/JPL-Caltech/Ken Kremer-kenkremer.com/Marco Di Lorenzo
Of course the proposed chemistry leading to life is exceedingly complex and life has never been created from non-life in the lab.
The key new points here are that Benner believes the origin of life involves “deserts” and oxidized forms of the elements Boron (B) and Molybdenum (Mo), namely “borate and molybdate,” Benner told me.
“Life originated some 4 billion years ago ± 0.5 billon,” Benner stated.
He says that there are two paradoxes which make it difficult for scientists to understand how life could have started on Earth – involving organic tars and water.
Life as we know it is based on organic molecules, the chemistry of carbon and its compounds.
But just discovering the presence of organic compounds is not the equivalent of finding life. Nor is it sufficient for the creation of life.
And simply mixing organic compounds aimlessly in the lab and heating them leads to globs of useless tars, as every organic chemist and lab student knows.
Benner dubs that the ‘tar paradox’.
Although Curiosity has not yet discovered organic molecules on Mars, she is now speeding towards a towering 3 mile (5 km) high Martian mountain known as Mount Sharp.
Curiosity Spies Mount Sharp – her primary destination
Curiosity will ascend mysterious Mount Sharp and investigate the sedimentary layers searching for clues to the history and habitability of the Red Planet over billions of years. This mosaic was assembled from over 3 dozen Mastcam camera images taken on Sol 352 (Aug 2, 2013. Credit: NASA/JPL-Caltech/MSSS/ Marco Di Lorenzo/Ken Kremer-kenkremer.com
Upon arrival sometime next spring or summer, scientists will target the state of the art robot to investigate the lower sedimentary layers of Mount Sharp in search of clues to habitability and preserved organics that could shed light on the origin of life question and the presence of borates and molybdates.
It’s clear that many different catalysts were required for the origin of life. How much and their identity is a big part of Benner’s research focus.
“Certain elements seem able to control the propensity of organic materials to turn into tar, particularly boron and molybdenum, so we believe that minerals containing both were fundamental to life first starting,” says Benner in a statement. “Analysis of a Martian meteorite recently showed that there was boron on Mars; we now believe that the oxidized form of molybdenum was there too.”
The second paradox relates to water. He says that there was too much water covering the early Earth’s surface, thereby causing a struggle for life to survive. Not exactly the conventional wisdom.
“Not only would this have prevented sufficient concentrations of boron forming – it’s currently only found in very dry places like Death Valley – but water is corrosive to RNA, which scientists believe was the first genetic molecule to appear. Although there was water on Mars, it covered much smaller areas than on early Earth.”
Parts of ancient Mars were covered by oceans, lakes and streams of liquid water in this artists concept, unlike the arid and bone dry Martian surface of today. Subsurface water ice is what remains of Martian water.
I asked Benner to add some context on the beneficial effects of deserts and oxidized boron and molybdenum.
“We have chemistry that (at least at the level of hypothesis) makes RNA prebiotically,” Benner explained to Universe Today.
“We require mineral species like borate (to capture organic species before they devolve to tar), molybdate (to arrange that material to give ribose), and deserts (to dry things out, to avoid the water problem).”
“Various geologists will not let us have these [borates and molybdates] on early Earth, but they will let us have them on Mars.”
“So IF you believe what the geologists are telling you about the structure of early Earth, AND you think that you need our chemistry to get RNA, AND IF you think that life began with RNA, THEN you place life’s origins on Mars,” Benner elaborated.
“The assembly of RNA building blocks is thermodynamically disfavored in water. We want a desert to get rid of the water intermittently.”
I asked Benner whether his lab has run experiments in support of his hypothesis and how much borate and molybdate are required.
“Yes, we have run many lab experiments. The borate is stoichiometric [meaning roughly equivalent to organics on a molar basis]; The molybdate is catalytic,” Benner responded.
“And borate has now been found in meteorites from Mars, that was reported about three months ago.
At his talk, Benner outlined some of the chemical reactions involved.
Although some scientists have invoked water, minerals and organics brought to ancient Earth by comets as a potential pathway to the origin of life, Benner thinks differently about the role of comets.
“Not comets, because comets do not have deserts, borate and molybdate,” Benner told Universe Today.
MAVEN is NASA’s next Mars orbiter and seeks to determine when Mars lost its atmosphere and water- key questions in the Origin of Life debate. MAVEN is slated to blastoff for Mars on Nov. 18, 2013. It is shown here with solar panels deployed as part of environmental testing procedures at Lockheed Martin Space Systems in Waterton, Colorado, before shipment to Florida in early August. Credit: Lockheed Martin
Benner has developed a logic tree outlining his proposal that life on Earth may have started on Mars.
“It explains how you get to the conclusion that life originated on Mars. As you can see from the tree, you can escape that conclusion by diverging from the logic path.”
Finally, Benner is not one who blindly accepts controversial proposals himself.
He was an early skeptic of the claims concerning arsenic based life announced a few years back at a NASA sponsored press conference, and also of the claims of Mars life discovered in the famous Mars meteorite known as ALH 84001.
“I am afraid that what we thought were fossils in ALH 84001 are not.”
The debate on whether Earthlings are really Martians will continue as science research progresses and until definitive proof is discovered and accepted by a consensus of the science community of Earthlings – whatever our origin.
On Nov. 18, NASA will launch its next mission to Mars – the MAVEN orbiter. Its aimed at studying the upper Martian atmosphere for the first time.
“MAVENS’s goal is determining the composition of the ancient Martian atmosphere and when it was lost, where did all the water go and how and when was it lost,” said Bruce Jakosky to Universe Today at a MAVEN conference at the University of Colorado- Boulder. Jakosky, of CU-Boulder, is the MAVEN Principal Investigator.
MAVEN will shed light on the habitability of Mars billions of years ago and provide insight on the origin of life questions and chemistry raised by Benner and others.
…………….
Learn more about Mars, the Origin of Life, LADEE, Cygnus, Antares, MAVEN, Orion, Mars rovers and more at Ken’s upcoming presentations
Sep 5/6/16/17: “LADEE Lunar & Antares/Cygnus ISS Rocket Launches from Virginia”; Rodeway Inn, Chincoteague, VA, 8 PM
Oct 3: “Curiosity, MAVEN and the Search for Life on Mars – (3-D)”, STAR Astronomy Club, Brookdale Community College & Monmouth Museum, Lincroft, NJ, 8 PM
Oct 9: “LADEE Lunar & Antares/Cygnus ISS Rocket Launches from Virginia”; Princeton University, Amateur Astronomers Assoc of Princeton (AAAP), Princeton, NJ, 8 PM
The NASA P-3B's shadow on sea ice off of southeast Greenland during an IceBridge survey on Apr. 9, 2013. Flying at a low altitude allows IceBridge researchers to gather detailed data. Credit: NASA / Jim Yungel
There’s a “Chuck Norris fact” that says Chuck once went skydiving but promised never to do it again, saying one Grand Canyon is enough. But Chuck must have taken another jump millions of years ago.
Data gathered by NASA’s Operation IceBridge, an aerial science observation mission, has uncovered a previously unknown massive canyon in Greenland, hidden under a kilometer of ice.
The canyon, found by airborne radar data, has the same characteristics of a winding river channel like the Grand Canyon in Arizona. It is at least 750 kilometers (460 miles) long, making it longer than the Grand Canyon. In some places, it is as deep as 800 meters (2,600 feet), on scale with parts of the Grand Canyon. This immense feature is thought to predate the ice sheet that has covered Greenland for the last few million years.
“One might assume that the landscape of the Earth has been fully explored and mapped,” said Jonathan Bamber, professor of physical geography at the University of Bristol in the United Kingdom, and lead author of the study. “Our research shows there’s still a lot left to discover.”
While additional airborne radar data was used, the majority of the data was collected by IceBridge flights over Greenland during flights from 2009 to 2013. IceBridge’s Multichannel Coherent Radar Depth Sounder can see through vast layers of ice to measure its thickness and the shape of bedrock below.
In their analysis of the radar data, Bamber and his team discovered a continuous bedrock canyon that extends from almost the center of the island and ends beneath the Petermann Glacier fjord in northern Greenland.
At certain frequencies, radio waves can travel through the ice and bounce off the bedrock underneath. The amount of time the radio waves took to bounce back helped researchers determine the depth of the canyon. The longer it took, the deeper the bedrock feature.
The researchers believe the canyon plays an important role in transporting sub-glacial meltwater from the interior of Greenland to the edge of the ice sheet into the ocean. Evidence suggests that before the presence of the ice sheet, as much as 4 million years ago, water flowed in the canyon from the interior to the coast and was a major river system.
“It is quite remarkable that a channel the size of the Grand Canyon is discovered in the 21st century below the Greenland ice sheet,” said Studinger. “It shows how little we still know about the bedrock below large continental ice sheets.”
The IceBridge campaign will return to Greenland in March 2014 to continue collecting data on land and sea ice in the Arctic using a suite of instruments that includes ice-penetrating radar.
Bamber and his team had their findings published in the journal Science.
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!
One of three discovery images of 2011 QF99 taken from CFHT on 2011 October 24 (2011 QF99 is inside the green circle). This is the first of three images of the same patch of sky, taken one hour apart, that were then compared to find moving light-sources.
What’s new in the outer reaches of our solar system? Try the discovery of a Trojan asteroid orbiting Uranus. While a plethora of puns exist for this simple fact, the reality check is that this means there are far more of these objects out there than astronomers expected. The new Trojan even has a name – 2011 QF99!
A Trojan asteroid is a transient space rock which is temporarily captured by the gravity of a giant planet. It shares the planet’s orbital path, locked into a specific position known as a Lagrange point. What makes 2011 QF99 unusual is its presence in the outer solar system. Researchers found the scenario a bit unlikely. Why? The answer is simply because of planet size. According to theory, the strong gravitational pull of the larger neighboring planets should have destabilized any captured asteroid’s orbit and shot Uranian Trojans out of the neighborhood long ago.
So just how did this 60 kilometer-wide conglomeration of ice and rock end up circling Uranus? Astronomers turned towards computer modeling for the answer. The research team, including UBC astronomers Brett Gladman, Sarah Greenstreet and colleagues at the National Research Council of Canada and Observatoire de Besancon in France, did a simulation of the solar system and its co-orbital objects – including Trojan asteroids. A short-term animation showing the motion of 2011 QF99, as seen from above the north pole of the solar system can be found here.
“Surprisingly, our model predicts that at any given time three percent of scattered objects between Jupiter and Neptune should be co-orbitals of Uranus or Neptune,” says Mike Alexandersen, lead author of the study to be published tomorrow in the journal Science.
Until now, no one had made any estimates on the percentage of possible outer solar system Trojans. Unexpectedly, the amount ended up being far greater than earlier estimates. Just over the last 10 years, several temporary Trojans and co-orbitals have been cataloged and 2011 QF99 is one of them. It made its home around Uranus within the last few hundred thousand years and will eventually – in about a million years – escape Uranus’ gravity.
“This tells us something about the current evolution of the solar system,” says Alexandersen. “By studying the process by which Trojans become temporarily captured, one can better understand how objects migrate into the planetary region of the solar system.”
