"How I Killed Pluto" -- a new book by planet hunter (and killer) Mike Brown.
[/caption]
It’s hard to imagine, but in 1992 astronomer Mike Brown didn’t know what the Kuiper Belt was. He had never heard of it. But just a few years later in 1999, he bet another scientist that within five more years he would find another planet out there at the edge of the solar system, past Pluto. It took a five-day extension of the bet, but Brown did it. And so began the death of Pluto as a planet, but the rise of a whole new class of objects called dwarf planets. Brown has written a book about his adventures as a planet hunter and eventual planet killer, called “How I Killed Pluto and Why it Had it Coming.”
His book is a highly readable, first person account of an astronomer who, by chance, realized he had remarkable penchant for discovering small, far away objects. The book is filled with humor, candor, geeky tendencies (he thought the first sonogram of his daughter looked like images from Venera 2 spacecraft from Venus), engaging personal anecdotes – and even romance, intrigue, mystery, fatherly love, and science.
“Discovery is exciting,” Brown writes in his book, “no matter how big or small or close or distant. But in the end, even better is discovering something that is capable of transforming our entire view of the sun and the solar system.”
And Brown’s discoveries have transformed our view of the solar system (some people have changed the world — how many can claim they have changed the solar system?!)
The discoveries of more objects in the Kuiper Belt turned on the heat of the debate of whether everyone’s favorite misfit planet, Pluto, was actually a planet or just a member of a new, quickly growing class of what are now called dwarf planets.
From this, some will claim, our planetary mnemonic went from “My Very Educated Mother Just Served Us Nine Pizzas” to “Mean Very Evil Men Just Shortened Up Nature.”
Mean and evil or educated? You decide.
Want a chance to win a copy of the book? Universe Today has 5 copies to giveaway!
UPDATE: We have winners! They are:
Gadi Eidelheit
Jason McInerney
Sten Thaning
Pam Jacobson
John Wenskovitch
Congrats!
Just send an email to [email protected] with the subject line of “Killing Pluto” by Monday, December 6 at 12 Noon Pacific Daylight Time. We’ll randomly choose 5 emails and notify the winners.
Eris — that pesky big dwarf planet that caused all the brouhaha about planets, dwarf planets, plutoids and the like — has gotten a closer look by a team of astronomers from several different universities, and guess what? Eris and Pluto have a lot in common. Eris appears to have a frozen surface, predominantly covered in nitrogen ice and methane, just like Pluto.
The scientists integrated two years of work conducted in Northern Arizona University’s new ice research laboratory, in addition to astronomical observations of Eris from the Multiple Mirror Telescope Observatory from Mount Hopkins, Ariz., and of Pluto from Steward Observatory from Kitt Peak, Ariz.
“There are only a handful of such labs doing this kind of work in the world,” said Stephen Tegler, from NAU and lead author of “Methane and Nitrogen Abundances on Eris and Pluto,” which was presented this week at the American Astronomical Society’s Divison of Planetary Science meeting. “By studying surfaces of icy dwarf planets, we hope to get a better understanding of the processes that affect their surfaces.”
NAU’s ice lab grew optically clear ice samples of methane, nitrogen, argon, methane-nitrogen mixtures, and methane-argon mixtures in a vacuum chamber at temperatures as low as minus 390 degrees Fahrenheit to simulate the planets’ cold surfaces. Light passed through the samples revealed the “chemical fingerprints” of molecules and atoms, which were compared to telescopic observations of sunlight reflected from the surfaces of Eris and Pluto.
“By combining the astronomical data and laboratory data, we found about 90 percent of Eris’s icy surface is made up of nitrogen ice and about 10 percent is made up of methane ice, which is not all that different from Pluto,” said David Cornelison, coauthor and physicist at Missouri State University.
The scientists say the recent findings will directly enhance NASA’s New Horizons spacecraft mission, currently scheduled to fly by Pluto in 2015, by lending greater value to the continued research of Eris and Pluto.
New Horizons image of Neptune and its largest moon, Triton. June 23, 2010. Credit: NASA
[/caption]
This summer, the New Horizons spacecraft was awoken for its annual systems checkout, and took the opportunity to exercise the long range camera by snapping pictures of Neptune, which at the time, was 3.5 billion km (2.15 billion miles) away. The Long Range Reconnaissance Imager (LORRI) snapped several photos of the gas giant, but Neptune was not alone! The moon Triton made a cameo appearance. And the New Horizons team said that since Triton is often called Pluto’s “twin” it was perfect target practice for imaging its ultimate target, Pluto.
This image gets us excited for 2015 when New Horizons will approach and make the closest flyby ever of Pluto.
“That we were able to see Triton so close to Neptune, which is approximately 100 times brighter, shows us that the camera is working exactly as designed,” said New Horizons Project Scientist Hal Weaver, of the Johns Hopkins Applied Physics Laboratory. “This was a good test for LORRI.”
Weaver pointed out that the solar phase angle (the spacecraft-planet-Sun angle) was 34 degrees and the solar elongation angle (planet-spacecraft-Sun angle) was 95 degrees. Only New Horizons can observe Neptune at such large solar phase angles, which he says is key to studying the light-scattering properties of Neptune’s and Triton’s atmospheres.
“As New Horizons has traveled outward across the solar system, we’ve been using our imagers to make just such special-purpose studies of the giant planets and their moons because this is a small but completely unique contribution that New Horizons can make — because of our position out among the giant planets,” said New Horizons Principal Investigator Alan Stern.
Triton is slightly larger than Pluto, 2,700 kilometers (1,700 miles) in diameter compared to Pluto’s 2,400 kilometers (1,500 miles). Both objects have atmospheres composed mostly of nitrogen gas with a surface pressure only 1/70,000th of Earth’s, and comparably cold surface temperatures approaching minus-400 degrees Fahrenheit. Triton is widely believed to have been a member of the Kuiper Belt (as Pluto still is) that was captured into orbit around Neptune, probably during a collision early in the solar system’s history.
The Planet Pluto crossing in front of Barnard 92. Credit: John Chumack
[/caption]
Last week, Pluto passed in front of what looks like a dark patch in the sky, and astrophotographer John Chumack was ready to capture the event. The dark patch is actually Barnard 92, a dark nebula. Since Pluto is usually very hard to see among the background of stars, it stands out against this dark nebula which blocks out the background stars. Still, Pluto – distant and dim as it is – is just a faint point of light, so John took special measures. “Although Pluto was easily visible in a short 5 minute exposure, I took an hour exposure to show the Dark nebula and the ‘rich & pretty’ surrounding star field,” he said.
The image was taken from John’s observatory in Yellow Springs, Ohio, using his homemade 16” Newtonian telescope and a QHY8CCD single shot color camera, captured from 01:00am until 02:00 am E.S.T. on July 6, 2010. Pluto and B92 sits within the large Sagittarius Star Cloud, M24.
Great shot, John! For more wonderful astronomical images, check out John’s website, Galactic Images.
New images of Pluto from the Hubble Space Telescope. Credit: NASA, ESA, and M. Buie (Southwest Research Institute).
Pluto-philes (and astronomers, too) have always bemoaned the fact that the best image of the principal dwarf planet wase just a fuzzy, pixelized haze. Bemoan no more. The most detailed look to date of the entire surface of Pluto has been constructed from hundreds of images taken by the Hubble Space Telescope. The images were taken during 2002 to 2003, and it took four years of computer crunching and software tweaking to create the global images. Surprisingly, the images show Pluto changed noticeably during the two-year photo shoot; the dwarf planet’s color became “redder,” and astronomers could see Pluto’s ice sheets were shifting.
“These Hubble pictures represent a true-color appearance of what you would see if you were near Pluto, comparable to looking at our own Moon with the naked eye,” said principal investigator Marc Buie of the Southwest Research Institute. “We now know we’re looking at something that has the biggest surface changes of any object in our solar system.”
The pictures show nitrogen ice growing and shrinking, getting brighter in the north and darker in the south.
Buie and planet hunter Mike Brown from Caltech introduced the Hubble images during a teleconference with reporters today, and emphasized how surprised they were with the changes seen on Pluto in just a relatively short period of time. Even accounting for seasonal changes, seasons can last 120 years in some regions of Pluto.
The top picture was taken in 1994 by the European Space Agency’s Faint Object Camera. The bottom image was taken in 2002-2003 by the Advanced Camera for Surveys. The dark band at the bottom of each map is the region that was hidden from view at the time the data were taken. Credit: NASA, ESA, and M. Buie (Southwest Research Institute)
They said the images underscore that Pluto is not simply a ball of ice and rock but a dynamic world that undergoes dramatic atmospheric changes. While they believe the changes are driven by the seasons, it may mostly come from how quickly things can change on Pluto. The seasons are propelled as much by the planet’s 248-year elliptical orbit as its axial tilt — unlike Earth where the tilt alone drives seasons. On Pluto spring transitions to polar summer quickly in the northern hemisphere because Pluto is moving faster along its orbit when it is closer to the Sun.
“If Earth had such an extreme orbit, and we were experiencing a nice springtime day with 60-70 degree F temperatures, as the orbit changed it could suddenly drop to -90 degrees F,” said Brown.
There is also a mysterious bright spot on the center of Pluto, which has been observed in earlier images. But the spot is unusually rich in carbon monoxide frost.
The astronomers said Pluto is so small and distant that the task of resolving the surface is as challenging as trying to see the markings on a soccer ball 40 miles away. Buie said we won’t have a better look at Pluto until the New Horizon’s spacecraft is six months away from the dwarf planet in 2015.
The images were taken with the Advanced Camera for Surveys on HST, and the 348 images taken in 2002 and 2003 were the last ones taken of Pluto with high enough resolution to be useful. “I had time allocated two years ago to look at Pluto, which came just three or four weeks after the high resolution camera failed,” Buie. “That was very disappointing.”
But the images do show Pluto is significantly redder than it had been for the past several decades. Astronomers use the word “red” to mean it reflects more red light than blue or green light. To the human eye, Pluto has a yellowish-orange color, and is about 20% redder than it used to be. “It’s not as red as the surface of Mars, but more red than Io,” Buie said.
Red is usually associated with carbon. The astronomers said there is also methane, which is not usually stable in an environment like Pluto’s.
“This business about the color change had me scared for awhile,” Buie confessed. “I got the result years ago, but it was so hard to understand and believe. I’m still nervous about it. It could be that I completely screwed this up, but I can tell you Charon is on the same images, and Charon has the same color throughout but Pluto changed. I don’t’ know how the camera system on HST could have given me the wrong colors on Pluto.”
This was previously the best image of Pluto, taken in 2000 by HST. Credit: Eliot Young (SwRI) et al., NASA
Someone suggested that Pluto is reddening because of its recent demotion from full planethood. “Yes, people have said that Pluto is mad at me,” said Brown, who has the nickname of the “Pluto killer” because he discovered other Kuiper Belt objects which led to the new class of dwarf planets.
“For a long time Pluto was this lonely oddball that we didn’t have anything else to compare it with,” said Brown. “Understanding this all as a new class of objects is a much more interesting way of looking at the solar system and it is quite a bit of fun, too.”
Artist concept of the New Horizons spacecraft. Credit: NASA/JPL
[/caption]
The New Horizons spacecraft crossed a milestone boundary today: it is now closer to its primary destination, Pluto, than to Earth. But New Horizons –the fastest man-made object — is not yet halfway to the dwarf planet. That won’t happen until February 25, 2010. New Horizons is now 1,440 days into its 9.5-year journey and well past 15 AU (astronomical units) from the Sun. But there is a long haul yet to go: there are still 1,928 days until operations begin for the close encounter, and 2022 days until the spacecraft reaches the closest point to Pluto in the summer of 2015. It is exciting to think what we will learn about Pluto and the Kuiper Belt in five and a half years. Will our perspectives change? Hard to believe they won’t.
New Horizons is currently traveling at about 50,000 kph (31,000 mph) (relative to the Sun) and is located about 2.4 billion kilometers (1.527 billion miles) from Earth.
The spacecraft launched in January 2006.
New Horizons will be taken out of hibernation in early January to repoint the communications dish antenna to keep up with the changing position of the Earth around the Sun. It was last awoken in November to download several months of stored science data from the Venetia Burney Student Dust Counter, to correct a recently discovered bug in the fault protection system software, (last thing anyone wants is to have the spacecraft go into safe mode at closest approach), and to upload instructions to run the spacecraft through early January. Telemetry shows that New Horizons is in very good health and almost exactly on its planned course.
Principal Investigator Alan Stern wrote in his last PI’s Perspective notes that the science team will meet in January to discuss which Kuiper Belt Objects they hope to “fly by and reconnoiter after Pluto. Those searches will begin next summer and continue through 2011 and 2012. Hopefully, they’ll net us four to 10 potential targets.”
New Horizons got a great shot of Neptune’s moon Triton last fall, as it was trucking toward Pluto and the Kuiper Belt.
The mission was 2.33 billion miles (3.75 billion kilometers) from Neptune on Oct. 16, when its Long Range Reconnaissance Imager (LORRI) locked onto the planet and snapped away. The craft was following a programmed sequence of commands as part of its annual checkout. NASA released the image Thursday afternoon.
Mission scientists say the shot was good practice for imaging Pluto, which New Horizons will do in 2015. Neptune’s moon Triton and Pluto — the former planet retitled in 2006 as the ambassador to the Kuiper Belt — have much in common.
“Among the objects visited by spacecraft so far, Triton is by far the best analog of Pluto,” said New Horizons Principal Investigator Alan Stern.
Triton is only slightly larger than Pluto, boasting a 1,700-mile (2,700-kilometers) diameter compared to Pluto’s 1,500-mile (2,400-kilometer) girth. Both objects have atmospheres primarily composed of nitrogen gas with a surface pressure only 1/70,000th of Earth’s, and comparably cold surface temperatures. Temperatures average -390 degrees F (-199 degrees C) on Triton and -370 degrees F (-188 degrees C) on Pluto.
Triton is widely believed to have once been a member of the Kuiper Belt that was captured into orbit around Neptune, probably during a collision early in the solar system’s history. Pluto was the first Kuiper Belt object to be discovered.
Furthermore, “We wanted to test LORRI’s ability to measure a faint object near a much brighter one using a special tracking mode,” said New Horizons Project Scientist Hal Weaver, of Johns Hopkins University, “and the Neptune-Triton pair perfectly fit the bill.”
LORRI was operated in 4-by-4 format (the original pixels are binned in groups of 16), and the spacecraft was put into a special tracking mode to allow for longer exposure times to maximize its sensitivity.
Mission scientists also wanted to measure Triton itself, to follow up on observations made by the Voyager 2 spacecraft during its flyby of Neptune in 1989. Those images revealed evidence of cryovolcanic activity and cantaloupe-like terrain. New Horizons can observe Neptune and Triton at solar phase angles (the Sun-object-spacecraft angle) that are not possible to achieve from Earth-based facilities, yielding new insight into the properties of Titan’s surface and Neptune’s atmosphere.
New Horizons is currently in electronic hibernation, 1.2 billion miles (1.93 billion kilometers) from home, speeding away from the Sun at 38,520 miles (61,991 kilometers) per hour. LORRI will continue to observe the Neptune-Triton pair during annual checkouts until the Pluto encounter in 2015.
LEAD IMAGE CAPTION: The top frame is a composite, full-frame (0.29° by 0.29°) LORRI image of Neptune taken Oct. 16, 2008, using an exposure time of 10 seconds and 4-by-4 pixel re-binning to achieve its highest possible sensitivity. The bottom frame is a twice-magnified view that more clearly shows the detection of Triton, Neptune’s largest moon. Neptune is the brightest object in the field and is saturated (on purpose) in this long exposure. Triton, which is about 16 arcsec east (celestial north is up, east is to the left) of Neptune, is approximately 180 times fainter. All the other objects in the image are background field stars. The dark “tails” on the brightest objects are artifacts of the LORRI charge-coupled device (CCD); the effect is small but easily seen in this logarithmic intensity stretch.(Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute)
Artist’s impression of how the surface of Pluto might look, if patches of pure methane rest on the surface. At the distance of Pluto, the Sun appears about 1,000 times fainter than on Earth. Credit: ESO
Artist’s impression of how the surface of Pluto might look, if patches of pure methane rest on the surface. At the distance of Pluto, the Sun appears about 1,000 times fainter than on Earth. Credit: ESO
Pluto is certainly frigid, but new research has revealed its atmosphere is a bit warmer.
Astronomers using the European Southern Observatory’s Very Large Telescope have found unexpectedly large amounts of methane in Pluto’s atmosphere, which evidently helps it stay about 40 degrees warmer than the dwarf planet’s surface. The atmosphere warms to -180 degrees Celsius (-356 degrees Fahrenheit), compared to a surface that’s usually -220 degrees Celsius (-428 degrees Fahrenheit).
“With lots of methane in the atmosphere, it becomes clear why Pluto’s atmosphere is so warm,” said Emmanuel Lellouch of the Observatoire de Paris in France. Lellouch is lead author of the paper reporting the results, which is in press at the journal Astronomy and Astrophysics.
Pluto, which is about a fifth the size of Earth, is composed primarily of rock and ice and orbits about 40 times further from the Sun than the Earth.
It has been known since the 1980s that Pluto also has a thin, tenuous atmosphere. Abundant nitrogen, along with traces of methane and probably carbon monoxide, are held to the surface by an atmospheric pressure only about one hundred thousandth of that on Earth, or about 0.015 millibars. As Pluto moves away from the Sun, during its 248 year-long orbit, its atmosphere gradually freezes and falls to the ground. In periods when it is closer to the Sun — as it is now — the temperature of Pluto’s solid surface increases, causing the ice to sublimate into gas.
Until recently, only the upper parts of the atmosphere of Pluto could be studied. By observing stellar occultations, a phenomenon that occurs when a Solar System body blocks the light from a background star, astronomers were able to demonstrate that Pluto’s upper atmosphere was some 50 degrees warmer than the surface. Those observations couldn’t shed any light on the atmospheric temperature and pressure near Pluto’s surface. But unique, new observations made with the CRyogenic InfraRed Echelle Spectrograph (CRIRES), attached to ESO’s Very Large Telescope, have now revealed that the atmosphere as a whole, not just the upper atmosphere, has a mean temperature much less frigid than the surface.
Usually, air near the surface of the Earth is warmer than the air above it, largely because the atmosphere is heated from below as solar radiation warms the Earth’s surface, which, in turn, warms the layer of the atmosphere directly above it. Under certain conditions, this situation is inverted so that the air is colder near the surface of the Earth. Meteorologists call this an inversion layer, and it can cause smog build-up.
Most, if not all, of Pluto’s atmosphere is thus undergoing a temperature inversion: the temperature is higher, the higher in the atmosphere you look. The change is about 3 to 15 degrees per kilometer (.62 miles). On Earth, under normal circumstances, the temperature decreases through the atmosphere by about 6 degrees per kilometer.
The reason why Pluto’s surface is so cold is linked to the existence of Pluto’s atmosphere, and is due to the sublimation of the surface ice; much like sweat cools the body as it evaporates from the surface of the skin, this sublimation has a cooling effect on the surface of Pluto.
The CRIRES observations also indicate that methane is the second most common gas in Pluto’s atmosphere, representing half a percent of the molecules. “We were able to show that these quantities of methane play a crucial role in the heating processes in the atmosphere and can explain the elevated atmospheric temperature,” said Lellouch.
Two different models can explain the properties of Pluto’s atmosphere. In the first, the astronomers assume that Pluto’s surface is covered with a thin layer of methane, which will inhibit the sublimation of the nitrogen frost. The second scenario invokes the existence of pure methane patches on the surface.
“Discriminating between the two will require further study of Pluto as it moves away from the Sun,” says Lellouch. “And of course, NASA’s New Horizons space probe will also provide us with more clues when it reaches the dwarf planet in 2015.”
LEAD IMAGE CAPTION: Artist’s impression of how the surface of Pluto might look, if patches of pure methane rest on the surface. At the distance of Pluto, the Sun appears about 1,000 times fainter than on Earth. Credit: ESO
[/caption]Naming Pluto explores the chain of events that lead to Pluto’s naming and in 2007 sees Venetia Phair viewing Pluto for the very first time through a telescope, on her 89th birthday, 77 years after Pluto’s discovery. A wonderful, intimate look into the story behind how Pluto got its name. A review of the short film directed and produced by Ginita Jimenez, distributed by Father Films.
In recent years, Pluto has seen its status change from being a planet to what many people view as a planetary underclass. The reasons behind this have been set out by the International Astronomical Union (IAU) to cater for the increasing number of Solar System bodies being discovered; the traditional nine planets have had to make room for a growing minor planet population. Unfortunately, Pluto was at the front line as it inhabits a region of space dominated by the gas giant Neptune, plus thousands of other Kuiper belt objects. Although the mysterious body lost its planetary status (as it does not have the ability to “clear its own orbit”), it has taken the title of “dwarf planet” and now has an entire class of object named in its honour: “Plutoids”.
However, the recent tumultuous history of the traditional “9th planet” has not impacted the fascination we have for Pluto. It has, and always will be, viewed with intrigue and wonder.
The key to Pluto’s romantic tale begins in the year 1930 when a mysterious heavenly was discovered by Clyde Tombaugh, a 23 year-old astronomer working at the Lowell Observatory in Flagstaff, Arizona. However, the honour of naming Pluto didn’t rest on Tombaugh’s shoulders. Over 5000 miles away in Oxford (UK) an 11 year old girl was having breakfast with her grandfather, wondering what this newly discovered planet should be called…
The Pluto system seen from the surface of Hydra (NASA)Naming Pluto starts out with some stunning visuals from 2006 of NASA’s New Horizons Pluto mission launching from Cape Canaveral. Throughout the opening tour of the Solar System, we can hear the voice of Venetia Burney as she is interviewed by NASA Public Affairs officer Edward Goldstein during the launch.
When Goldstein asks whether she had ever seen Pluto through a telescope, the clear and articulate voice of Venetia replies, “I don’t think I have. I’ve just seen a photograph.” And so the journey begins, where Venetia explains her fascination with Pluto and a number of experts (including the enigmatic Sir Patrick Moore) help to explain the facts behind the discovery of Pluto to the scientific endeavour of the search for “Planet X”.
One of the key moments is when Venetia is describing when she decided on the name for the heavenly body. At age 11, had an acute interest in ancient mythology, so she chose the name because Pluto is the Roman god of the underworld; a fitting name considering the cold, dark nature of Pluto’s 248 year orbit. In a fortuitous chain of events, her grandfather, a former librarian of Oxford University’s Bodleian Library, passed the suggestion via letter to Professor Herbert Hall Turner saying that his granddaughter had chosen a “thoroughly suitable name: PLUTO.” Hall Turner, thrilled with the candidate name, sent Venetia’s idea to colleagues in the USA, at the Lowell Observatory.
A special delight is when Venetia visits St. Anne’s Primary School in Surrey to participate in their class project all about Pluto. It goes to show that even young school children have fallen under Pluto’s spell. One 9 year-old pupil, Katie, shares her concerns about Pluto’s demotion, “Some people say that Pluto isn’t a real planet, so I’m looking forward to Venetia coming because I want to find out if that’s true.”
Other guests on the film uncover the various attributes of Pluto’s discovery, delving into the history and future of the planetary lightweight on the outermost reaches of the Solar System.
“Yes, indeed,” the ever gracious Venetia replies, smiling.
Unfortunately, the UK summer weather conspired against the possibility of clear skies, and any chance of Patrick’s 15″ reflector of spying Pluto was lost. However, there is a fantastic twist in the tale, bringing the whole film to a wonderfully emotional ending.
All in all, Naming Pluto is a fabulous tribute, not only to Venetia, but to the astronomical process. Although Pluto has undergone a change in status these last few years, it remains an important, permanent feature of the Solar System. This well-crafted story gives the viewer an excellent overview of Pluto’s discovery, naming and the magic it holds today for the 9 year-olds at St. Anne’s to Venetia who named the planet nearly 80 years ago…
A big thank you goes to writer, director and producer Ginita Jimenez for sharing this magnificent production with me. My copy will have pride of place with my growing collection of space science DVDs, a timeless memento of a historic time for astronomy.
If you want your own copy, or want to buy it as a gift, contact Ginita at: [email protected]
Naming Pluto is currently on the international film festival circuit so if you’d prefer watching it on the big screen, and are in the area, please see below. There will also be a blog and updates on www.fatherfilms.com.
THROUGH WOMEN’S EYES – USA
WWW.THROUGHWOMENSEYES.COM
30TH & 31ST JANUARY 2009
JAIPUR INTERNATIONAL FILM FESTIVAL – INDIA
WWW.JIFFINDIA.ORG
FEB/MARCH 2009
SEBASTOPOL DOCUMENTARY FILM FESTIVAL – USA
WWW.SEBASTOPOLFILMFESTIVAL.ORG
MARCH 6-8, 2009
CINEQUEST FILM FESTIVAL – USA
WWW.CINEQUEST.ORG
FEB 25-MAR 08 2009
OFFICIAL SELECTION FOR BEST SHORT FILM AWARD
[/caption]Eris, the largest dwarf planet beyond Neptune, is currently at its furthest point in its orbit from the Sun (an aphelion of nearly 100 AU). At this distance Eris doesn’t receive very much sunlight and any heating of the Plutoid will be at a minimum. However, two recent observations of Eris have shown a rapid change in the surface composition of the body. Spectroscopic analysis suggests the concentration of frozen nitrogen has dramatically altered during the two years Eris had been at this furthest point from the Sun. This is very unexpected, there should be very little change in nitrogen concentration at this point in its 557 year orbit.
So what is going on with this strange Plutoid? Is there a mystery mechanism affecting the surface conditions of this frozen moon? Could there be some cryovolcanic process erupting? Or is the explanation a little more mundane?
“We’re really scratching our heads,” says Stephen Tegler of Northern Arizona University in Flagstaff, author of the new Eris research (to be published in the journal Icarus). Tegler and his team analysed spectroscopic data from the 6.5 metre MMT observatory in Arizona and compared their 2007 results with a similar observation campaign by the 4.2 metre William Herschel Telescope in Spain two years earlier in 2005.
During that two year period, the scientists wouldn’t have thought there would be much difference in the two datasets. After all, the reflected sunlight off the surface of Eris should reveal a similar surface composition, right? Actually, the results couldn’t be more surprising. It would appear that within two years, having not changed its distance from the Sun significantly, the surface composition has changed a lot. Normally, this would be expected if a planetary body approaches or travels away from the Sun; the increase or decrease in solar energy would change the weather conditions on the surface. But this situation does not apply to Eris, there is little chance that the Sun could influence the weather on the surface of Eris to any degree (or, indeed, if Eris even has “weather”).
So what have the researchers deduced from the comparison of the 2005/2007 data? It would appear the spectroscopic methane lines have become diluted by an increased quantity of nitrogen. This means that the 2005 results showed a higher concentration of nitrogen near the surface, whereas the 2007 results show a higher concentration below the surface. For a dwarf planet to demonstrate a very fast change in surface composition appears to show some very dynamic process is at work.
So what could have caused this change? In the case of a dynamic weather process, “it’s very hard to imagine that something that dramatic would be happening on a relatively short time scale,” says Mike Brown of Caltech, a scientist not involved with the research. Another possibility is that 2003ub313 is a cryovolcanic body. Cryovolcanoes can erupt on icy moons or bodies in the Kuiper belt, but rather than spewing molten rock (magma), they erupt volatiles like ammonia, water or (in this case) nitrogen and methane. The ejected cryomagma then condenses into a solid, thus changing the surface composition of the icy body.
But it is not known whether Eris is warm enough for such a process to work. More information on trans-Neptunian object (TNO) cryovolcanism will be examined when NASA’s New Horizons mission reaches Eris’ smaller cousin Pluto in 2015. “If a shrimpy little body like Pluto can do it, Eris can too,” said co-author William Grundy of Lowell Observatory in Flagstaff, Arizona.
However, there is a possibility that the surface composition of Eris hasn’t changed at all. The 2005 and 2007 observations may have been analysing two different regions on the dwarf planet, thus the difference in surface composition (after all, the Plutoid has a rotation period of 26 hours, they would have almost definitely have seen different parts of Eris). So the next step for the researchers is to carry out an extended campaign throughout an “Eris day” to see if the surface composition is in fact patchy, which would be an interesting discovery in itself.
