Posted on by Fraser Cain

Iceberg Smashes Off a Chunk of Antarctica

Maps of Antarctica need to be amended. The long-awaited collision between the vast B-15A iceberg and the landfast Drygalski ice tongue has taken place. This Envisat radar image shows the ice tongue ? large and permanent enough to feature in Antarctic atlases – has come off worst.

An image acquired by Envisat on 15 April 2005 shows that a five-kilometre-long section at the seaward end of Drygalski has broken off following a collision with the drifting B-15A. The iceberg itself appears so far unaffected. With more than half the iceberg still to clear the floating pier of ice, Drygalski may undergo more damage in coming days.

It is an old philosophical paradox: what happens when an irresistible force meets an immovable object? For the past few months, ESA’s Envisat satellite has been watching an answer play out in ice, as the B-15A iceberg converged on the Drygalski ice tongue.

The sheer scale of B-15A is best appreciated from space. The bottle-shaped Antarctic iceberg is around 115 kilometres long, with an area exceeding 2500 square kilometres, making it about as large as the entire country of Luxembourg.

From January the iceberg has been drifting towards, then past, the 70-kilometre-long Drygalski ice tongue in McMurdo Sound on the Ross Sea. In the last month prevailing currents have been slowly edging B-15A along past the northern edge of Drygalski.

Envisat’s Advanced Synthetic Aperture Radar (ASAR) instrument has been monitoring events since the start of the year, gathering the highest frequency weather-independent satellite dataset of this area ever.

Ice in opposition
B-15A is the largest remaining section of the even larger B-15 iceberg that calved from the Ross Ice Shelf in March 2000. Equivalent in size to Jamaica, B-15 had an initial area of 11 655 square kilometres but subsequently broke up into smaller pieces.

Since then, the largest piece – B-15A – has found its way to McMurdo Sound, where its presence has blocked ocean currents and led to a build-up of sea ice. With the Antarctic summer now at an end and in-situ observations therefore limited, the ASAR instrument aboard Envisat becomes even more useful for monitoring changes in polar ice and tracking icebergs.

Its radar signals pass freely through the thickest polar storm clouds or local darkness. And because ASAR is sensitive to surface texture as well as physical and chemical properties, the sensor is extremely sensitive to different types of ice ? for example clearly delineating the older rougher surface of the Drygalski ice tongue and iceberg B15A from the surrounding sea ice pack.

The Drygalski ice tongue is located at the opposite end of McMurdo Sound from the US and New Zealand bases. The long narrow tongue stretches out to sea as an extension of the land-based David Glacier, which flows through coastal mountains of Victoria Land.

Twin-mode ASAR Antarctic observations
Envisat’s ASAR instrument monitors Antarctica in two different modes: Global Monitoring Mode (GMM) provides 400-kilometre swath one-kilometre resolution images, enabling rapid mosaicking of the whole of Antarctica to monitor changes in sea ice extent, ice shelves and iceberg movement.

Wide Swath Mode (WSM) possesses the same swath but with 150-metre resolution for a detailed view of areas of particular interest.

ASAR GMM images are routinely provided to a variety of users including the US National Oceanic and Atmospheric Administration (NOAA) National Ice Centre, responsible for tracking icebergs worldwide.

ASAR imagery is also being used operationally to track icebergs in the Arctic by the Northern View and ICEMON consortia, which provide ice monitoring services as part of the Global Monitoring for Environment and Security (GMES) initiative, jointly backed by ESA and the European Union.

This year also sees the launch of CryoSat, a dedicated ice-watching mission designed to precisely map changes in the thickness of polar ice sheets and floating sea ice.

CryoSat, in connection with regular Envisat ASAR GMM mosaics and SAR interferometry ? a technique used to combine radar images to measure tiny centimetre-scale shifts between acquisitions – should answer the question of whether the kind of ice-shelf calving that gave rise to B-15 and its descendants are a consequence of ice sheet dynamics or other factors.

Together they will provide insight into whether such iceberg calving occurrences are becoming more common, as well as improving our understanding of the relationship between the Earth’s ice cover and the global climate.

Original Source: ESA News Release

Posted on by Fraser Cain

Expedition 11’s Soyuz Docks

Image credit: NASA
New residents arrived at the International Space Station tonight to begin a six-month mission and to prepare for the arrival of the first Space Shuttle crew to visit the complex since November 2002.

With Expedition 11 Commander Sergei Krikalev at the controls, the Soyuz TMA-6 spacecraft automatically linked up to the Pirs Docking Compartment at 9:20 p.m. CDT as the Soyuz and the Station flew over eastern Asia. Within minutes, hooks and latches between the two vehicles joined together to form a tight seal.

Aboard the Soyuz with Krikalev were NASA Expedition 11 Flight Engineer and Science Officer John Phillips and European Space Agency (ESA) Astronaut Roberto Vittori of Italy.

Hatches between the Soyuz and the Station were opened at 11:45 p.m. Saturday. The two crews greeted one another with handshakes and hugs. The first activity scheduled for the five crewmembers was a safety briefing to familiarize the newly arrived trio with emergency escape procedures.

Krikalev and Phillips will remain on board the Station until October. Vittori will return to Earth next week after eight days of scientific experiments on the complex under a commercial agreement between ESA and the Russian Federal Space Agency. The trio launched at dawn Friday from the Baikonur Cosmodrome in Kazakhstan for their two-day journey to the outpost.

Aboard the Station at the time of docking were Expedition 10 Commander and NASA Science Officer Leroy Chiao and Flight Engineer Salizhan Sharipov, who are wrapping up their six-month mission and who will ride home on their Soyuz TMA-5 capsule with Vittori on April 25 for a pre-dawn landing in central Kazakhstan. Saturday marked the 185th day in space for Chiao and Sharipov and their 183rd day on the Station.

Krikalev and Phillips will relocate the new Soyuz from Pirs to the Zarya module docking port this summer.

On hand for the docking activities at the Russian Mission Control Center outside Moscow were NASA Deputy Administrator Fred Gregory, NASA Deputy Associate Administrator for Space Station and Space Shuttle Programs Michael Kostelnik, NASA Deputy Associate Administrator for Exploration Systems Craig Steidle and ISS Program Manager William Gerstenmaier along with Russian and European space officials.

On Sunday before they begin an extended sleep period, the new crew will transfer their custom-made Soyuz seatliners as well as cargo carried aloft on the Soyuz for the complex. Later in the day, initial briefings on the handover from the current residents to their replacements will be conducted and the new Soyuz? systems will be deactivated.

Over the next week, Krikalev and Phillips will familiarize themselves with Station systems and stowed equipment, conduct robotics training with the Canadarm2 robot arm, and receive detailed briefings on scientific payloads. Phillips and Chiao will also continue the maintenance and repair work on the cooling systems in the U.S. airlock Quest for the resumption of spacewalk capability from the Station this summer.

In addition, they will pack discarded gear and equipment for return to Earth on the Raffaello cargo module that will be brought to the Station on the Space Shuttle?s Return to Flight mission, STS-114, targeted to arrive next month on the Shuttle Discovery.

Information on the crew’s activities aboard the Space Station, future launch dates, as well as Station sighting opportunities from anywhere on the Earth, is available on the Internet at:


http://spaceflight.nasa.gov/

Original Source: NASA News Release

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Podcast: Oldest Star Discovered

Let’s say you’re browsing around the comic book store and happened to notice a perfect copy of Action Comics #1 on the rack mixed in with the current stuff. It’s in mint condition, untouched since it was first printed almost 70 years ago. Now imagine the same situation… except with stars. Anna Frebel is a PhD student at the Research School of Astronomy & Astrophysics at the Australian National University. She’s working with a team of astronomers who have found the oldest star ever seen – possibly untouched since shortly after the Big Bang.
Continue reading “Podcast: Oldest Star Discovered”

Posted on by Fraser Cain

Matter is Incinerated When it Falls into a Black Hole

Image credit: ESA
Contrary to established scientific thinking, you’d be roasted and not “spaghettified” if you stumbled into a supermassive black hole. New research being presented at the Institute of Physics conference Physics 2005 in Warwick will take a new look at the diet of the universe’s most intriguing object, black holes.

Black holes stand at the very edge of scientific theory. Most scientists believe they exist, although many of their theories break down under the extreme conditions within. But Professor Andrew Hamilton of the University of Colorado says he knows what you would find inside, and challenges the traditional idea that gravity would cause you death by “spaghettification”.

Most people have heard of the event horizon of a black hole, as the point of no return. But astronomically realistic black holes are more complex and should have two horizons, an outer and an inner. In the bizarre physics of black holes, time and space are exchanged when you cross an event horizon, but at a second horizon they would switch back again.

Traveling into a black hole, you would therefore pass through a strange region where space is falling inward faster than light, before finally entering a zone of normal space at the core. It’s this core of normal space which Professor Hamilton has been working on.

A so-called singularity sits at the centre of the core, swallowing up matter. But according to Professor Hamilton, the strange laws of general relativity temper its appetite. If the singularity ate too quickly, it would become gravitationally repulsive, so instead, matter piles up in a hot, dense plasma filling the core of the black hole and siphoning gradually into the singularity.

Depending on the size of the black hole, this plasma could be the cause of a space traveller’s demise. Most books will tell you that under the extreme gravitational conditions of a black hole, your feet would experience gravity more strongly than your head, and your body would be stretched out like spaghetti.

For a small black hole with the mass of several suns, this should still be true. But for a supermassive black hole weighing millions or billions of suns, explains Professor Hamilton, the tidal forces which cause spaghettification are relatively weak. You would instead be roasted by the heat of the plasma.

Professor Andrew Hamilton is Professor of Astrophysics at the Department of Astrophysical and Planetary Sciences, University of Colorado.

Original Source: Institute of Physics News Release

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Michael Griffin Takes the Helm at NASA

Michael Griffin is returning to NASA as the Agency’s 11th Administrator.

He reported to work at NASA Headquarters in Washington on Thursday, April 14, the same day the Expedition 11 crew launched to the International Space Station.

“I have great confidence in the team that will carry out our nation’s exciting, outward-focused, destination-oriented program,” said Griffin. “I share with the agency a great sense of privilege that we have been given the wonderful opportunity to extend humanity’s reach throughout the solar system.”

Administrator Griffin, who served as NASA’s Chief Engineer earlier in his career, takes the helm of the Agency as it’s charting a new course. The Space Shuttle fleet is poised to Return to Flight, the first step in fulfilling the Vision for Space Exploration — a bold plan to return humans to the Moon, journey to Mars and beyond.

In his first address to NASA employees, Griffin said he would focus immediately on Return to Flight efforts, and noted that the Agency has much on its plate right now. “It’s going to be difficult, it’s going to be hectic, but we will do it together,” he said.

He also told employees that he saw “nothing but cheers” in the public reaction to the Vision. “People want a space program that goes somewhere and does something,” he said.

Griffin was nominated by President George W. Bush on March 14, 2005, and confirmed by the United States Senate on April 13, 2005. At his confirmation hearing on April 12, he made clear that the “strategic vision for the U.S. manned space program is of exploration beyond low Earth orbit.”

In his statement to the committee, Griffin said, “It is a daring move at any time for a national leader to call for the bold exploration of unknown worlds, a major effort at the very limit of the technical state of the art,” adding later, “in the twenty-first century and beyond, for America to continue to be preeminent among nations, it is necessary for us also to be the preeminent spacefaring nation.”

A holder of five master’s degrees and a Ph.D., Griffin also made clear that, despite limited resources, “NASA can do more than one thing at a time.”

“My conclusion is that we as a nation can clearly afford well-executed, vigorous programs in both robotic and human space exploration as well as in aeronautics. We know this. We did it,” he said, referring back to the Agency’s accomplishments during the Apollo era.

He closed his statement with a call for exploration: “I believe that, if money is to be spent on space, there is little doubt that the huge majority of Americans would prefer to spend it on an exciting, outward-focused, destination-oriented program. And that is what the President’s Vision for Space Exploration is about.”

Prior to his appointment, Griffin was serving as Space Department Head at Johns Hopkins University Applied Physics Laboratory. Prior to that, he was President and Chief Operating Officer of In-Q-Tel, Inc. He also served in several positions within Orbital Sciences Corporation, including Chief Executive Officer of Magellan Systems, Inc.

Earlier in his career, Griffin served as chief engineer and associate administrator for exploration at NASA Headquarters and also worked at NASA’s Jet Propulsion Laboratory. He also served as Deputy for Technology at the Strategic Defense Initiative Organization.

Griffin received a bachelor’s degree in Physics from Johns Hopkins University; a master’s degree in Aerospace Science from Catholic University of America; a Ph.D. in Aerospace Engineering from the University of Maryland; a master’s degree in Electrical Engineering from the University of Southern California; a master’s degree in Applied Physics from Johns Hopkins University; a master’s degree in Business Administration from Loyola College; and a master’s degree in Civil Engineering from George Washington University.

Original Source: NASA News Release

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Expedition 11 Blasts Off for the Station

The Expedition 11 crew — Cosmonaut Sergei Krikalev and Astronaut John Phillips — launched from the Baikonur Cosmodrome in Kazakhstan at 8:46 p.m. EDT Thursday, right on schedule.

Their Soyuz TMA capsule reached orbit a little less than nine minutes after liftoff. Russian flight controllers reported the spacecraft’s solar arrays had deployed as scheduled, and that all appeared normal.

With this 11th crew of the International Space Station is European Space Agency Astronaut Roberto Vittori of Italy. Their Soyuz is scheduled to dock with the Space Station at 10:19 p.m. EDT April 16.

Expedition 11’s Krikalev and Phillips will spend about six months aboard the Space Station. Vittori will spend almost eight days on the Station conducting scientific experiments, and return to Earth with the Expedition 10 crew.

That crew, Commander Leroy Chiao and Cosmonaut Salizhan Sharipov, has been on the station since October. They will leave the station April 24 in the Soyuz that brought them to the orbiting laboratory. Their landing is scheduled for 6:09 p.m. EDT that day in Kazakhstan.

Highlights of the new crew’s mission include welcoming the crew of the Space Shuttle Discovery on its STS-114 mission, the first Shuttle flight since the Columbia accident. Discovery crewmembers will conduct three spacewalks at the Station, deliver several tons of equipment and supplies and return to Earth with equipment and scientific experiments and trash from the Station.

Krikalev, 46, and Phillips, 54, will receive extensive handover briefings from their Expedition 10 predecessors, and will get training on the Station’s robotic Canadarm2.

They also may see the addition of a third crewmember to the Station this summer brought to the station by Atlantis on the STS-121 mission. Plans call for them to do two spacewalks, the first in August from the U.S airlock Quest in U.S. spacesuits, and the second, in September, in Russian spacesuits from the Pirs airlock. The spacewalkers will continue outfitting the station’s exterior and work with scientific experiments.

Krikalev and Phillips also will welcome the arrival of two Progress unpiloted supply vehicles. ISS Progress 18 is scheduled to reach the Station in June and ISS Progress 19 should be launched near the end of August.

In August, Krikalev, who also is Soyuz commander, and Phillips, who also will have the title of NASA ISS science officer, will move their Soyuz spacecraft from the Pirs docking compartment to the Zarya docking port. That will permit use of the Pirs airlock for spacewalk activity.

Krikalev is a veteran of five previous spaceflights, including two missions to the Russian space station Mir and two Shuttle flights. He was a member of the first Station Crew, serving aboard a much smaller ISS from Nov. 2, 2000, to March 18, 2001. He has spent a year, 5 months and 10 days in space. This flight should see him become the world’s most experienced space traveler.

Born in Leningrad (now St. Petersburg), Russia, he graduated from what is now St. Petersburg Technical University in 1981 and then joined NPO Energia, the Russian organization responsible for human spaceflight. He was selected as a cosmonaut in 1985.

Record or not, just being in space isn’t what’s important, Krikalev says. “The job itself is very interesting for me, being there and being able to look back on Earth, to do something challenging.” He said he probably hasn’t paid enough attention to that record.

Philips was born in Fort Belvoir, Va., and considers Scottsdale, Ariz., his home. He graduated from the Naval Academy in 1972 and became a Naval aviator. After leaving the Navy in 1982, he earned a masters and doctorate in geophysics and space physics from the University of California in 1984 and 1987. He did postdoctoral work at the Los Alamos Scientific Laboratory in New Mexico.

He was selected as an astronaut in 1996. He was a member of the STS-100 crew of Endeavour in 2001. On that mission he coordinated two spacewalks at the Station to install Canadarm2.

Phillips has wanted to return to the Station ever since. “It was a wonderful place to be,” he said. “The crew was doing a great job; they were having a good time.” He wanted to stay longer then. Now he’ll have about six months there.

Krikalev and Phillips are the Station’s fifth two-person crew. After the Columbia accident on Feb. 1, 2003, the ISS Program and the international partners determined that because of limitations on supplies the Station would be occupied by two crewmembers instead of three until Shuttle flights resume.

The 11th crew will continue science activities, initially with facilities and samples already on the station, but later with experiments scheduled to arrive at the station aboard Discovery.

The science team at the Payload Operations Center at the Marshall Space Flight Center in Huntsville, Ala., will continue to operate some experiments without crew input and other experiments are designed to function autonomously.

Krikalev and Phillips are scheduled to spend about 180 days on the Station, returning to Earth in October, a little over a week after the arrival of their Expedition 12 successors.

Original Source: NASA News Release

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Enceladus Above Saturn’s Rings

Saturn’s bright moon Enceladus hovers here, in front of a rings darkened by Saturn’s shadow. Enceladus is 505 kilometers (314 miles) across.

This view is from less than one degree beneath the ring plane. If seen from directly beneath the rings, the planet’s giant shadow would appear as an elongated half-ellipse; the acute viewing angle makes the shadow look more like a strip here. (See The Greatest Saturn Portrait…Yet, for a different viewing angle). The dark shadow first takes a bite out of the rings at the right, where the distant, outermost ring material appears to taper and fade.

Ring features visible in this image from the outer ring edge inward include: the A ring, the Cassini Division and the B ring. The C ring is the darker region that dominates the rings here. The two gaps visible near the center and below the left of the center are the Titan Gap, about 77,800 kilometers (48,300 miles) from Saturn, and an unnamed gap about 75,800 kilometers (47,100 miles) from the planet.

The image was taken in visible light with the Cassini spacecraft narrow-angle camera on March 7, 2005, at a distance of approximately 1.1 million kilometers (650,000 miles) from Enceladus and at a Sun-Enceladus-spacecraft, or phase, angle of 30 degrees. The pixel scale is 6 kilometers (4 miles) per pixel.

The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the mission for NASA’s Science Mission Directorate, Washington, D.C. The Cassini orbiter and its two onboard cameras were designed, developed and assembled at JPL. The imaging team is based at the Space Science Institute, Boulder, Colo.

For more information about the Cassini-Huygens mission visit http://saturn.jpl.nasa.gov . For additional images visit the Cassini imaging team homepage http://ciclops.org .

Original Source: NASA/JPL/SSI News Release

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Podcasts: Best Spot for a Lunar Base

In case you missed the news, NASA is headed back to the Moon in the next decade. A permanent lunar base could be down the road, so scientists are starting to consider where we should build. Ben Bussey, with Johns Hopkins University Applied Physics Laboratory in Maryland likes the Moon’s North Pole. It’s got everything you might need for a long-term stay: permanent sunlight, relatively stable temperatures, and lots of lunar soil. And as an added bonus, there might be plenty of frozen water hiding in lunar craters.
Continue reading “Podcasts: Best Spot for a Lunar Base”

Posted on by Fraser Cain

Audio: Best Spot for a Lunar Base

In case you missed the news, NASA is headed back to the Moon in the next decade. A permanent lunar base could be down the road, so scientists are starting to consider where we should build. Ben Bussey, with Johns Hopkins University Applied Physics Laboratory in Maryland likes the Moon’s North Pole. It’s got everything you might need for a long-term stay: permanent sunlight, relatively stable temperatures, and lots of lunar soil. And as an added bonus, there might be plenty of frozen water hiding in lunar craters.

Listen to the interview: North Pole Lunar Base (2.9 mb)

Or subscribe to the Podcast: universetoday.com/audio.xml

Posted on by Fraser Cain

Strange Extrasolar Planet Orbits Explained

Image credit: NWU
The peculiar orbits of three planets looping around a faraway star can be explained only if an unseen fourth planet blundered through and knocked them out of their circular orbits, according to a new study by researchers at the University of California, Berkeley, and Northwestern University.

The conclusion is based on computer extrapolations from 13 years of observations of planet motions around the star Upsilon Andromedae. It suggests that the non-circular and often highly elliptical orbits of many of the extrasolar planets discovered to date may be the result of planets scattering off one another. In such a scenario, the perturbing planet could be shot out of the system entirely or could be kicked into a far-off orbit, leaving the inner planets with eccentric orbits.

“This is probably one of the two or three extrasolar systems that have the best observations and tightest constraints, and it tells a unique story,” said Eric Ford, a Miller postdoctoral fellow at UC Berkeley. “Our explanation is that the outer planet’s original orbit was circular, but it got this sudden kick that permanently changed its orbit to being highly eccentric. To provide that kick, we’ve hypothesized that there was an additional planet that we don’t see now. We believe we now understand how this system works.”

If such a planet had caromed through our solar system early in its history, the researchers noted, the inner planets might not now have such nicely circular orbits, and, based on current assumptions about the origins of life, Earth’s climate might have fluctuated too much for life to have arisen.

“While the planets in our solar system remain stable for billions of years, that wasn’t the case for the planets orbiting Upsilon Andromedae,” Ford said. “While those planets might have formed similarly to Jupiter and Saturn, their current orbits were sculpted by a late phase of chaotic and violent interactions.”

According to Ford’s colleague, Frederic A. Rasio, associate professor of physics and astronomy at Northwestern, “Our results show that a simple mechanism, often called ‘planet-planet scattering’ – a sort of slingshot effect due to the sudden gravitational pull between two planets when they come very near each other – must be responsible for the highly eccentric orbits observed in the Upsilon Andromedae system. We believe planet-planet scattering occurred frequently in extrasolar planetary systems, not just this one, resulting from strong instabilities. So, while planetary systems around other stars may be common, the kinds of systems that could support life, which, like our solar system, presumably must remain stable over very long time scales, may not be so common.”

The computer simulations are reported in the April 14 issue of the journal Nature by Ford, Rasio and Verene Lystad, an undergraduate student majoring in physics at Northwestern. Ford was a student of Rasio’s at the Massachusetts Institute of Technology before pursuing graduate studies at Princeton University and arriving at UC Berkeley in 2004.

The planetary system around Upsilon Andromedae is one of the most studied of the 160-some systems with planets discovered so far outside our own solar system. The inner planet, a “hot Jupiter” so close to the star that its orbit is only a few days, was discovered in 1996 by UC Berkeley’s Geoff Marcy and his planet-hunting team. The two outer planets, with elongated orbits that perturb each other strongly, were discovered in 1999. These three, huge, Jupiter-like planets around Upsilon Andromedae comprised the first extrasolar multi-planet system discovered by Doppler spectroscopy.

Because of the unusual nature of the planetary orbits around Upsilon Andromedae, Marcy and his team have studied it intensely, making nearly 500 observations – 10 times more than for most other extrasolar planets that have been found. These observations, the wobbles in the star’s motion induced by the orbiting planets, allow a very precise charting of the planets’ motions around the star.

“The observations are so precise that we can watch and predict what will happen for tens of thousands of years in the future,” Ford said.

Today, while the innermost planet huddles close to the star, the two outer planets orbit in egg-shaped orbits. Computer simulations of past and future orbital changes showed, however, that the outer planets are engaged in a repetitive dance that, once every 7,000 years, brings the orbit of the middle planet to a circle.

“That property of returning to a very circular orbit is quite remarkable and generally doesn’t happen,” Ford said. “The natural explanation is that they were once both in circular orbits, and one got a big kick that caused it to become eccentric. Then, the subsequent evolution caused the other planet to grow its eccentricity, but because of the conservation of energy and angular momentum, it returns periodically to a very nearly circular orbit.”

Previously, astronomers had proposed two possible scenarios for the formation of Upsilon Andromedae’s planet system, but the observational data was not yet sufficient to distinguish the two models. Another astronomer, Renu Malhotra at the University of Arizona, had previously suggested that planet-planet scattering might have excited the eccentricities in Upsilon Andromedae. But an alternative explanation claimed that interactions among the planets and a gas disk surrounding the star could also have produced such eccentric orbits. By combining additional observational data with new computer models, Ford and his colleagues were able to show that interactions with a gas disk would not have produced the observed orbits, but that interactions with another planet would naturally produce them.

“The key distinguishing feature between those theories was that interactions with an outer disk would cause the orbits to change very slowly, and a strong interaction with a passing planet would cause the orbits to change very quickly compared to the 7,000-year time scale for the orbits to evolve,” Ford said. “Because the two hypotheses make different predictions for the evolution of the system, we can constrain the history of the system based on the current planetary orbits.”

Ford said that as the planets formed inside a disk of gas and dust, the drag on the planets would have kept their orbits circular. Once the dust and gas dissipated, however, only an interaction with a passing planet could have created the particular orbits of the two outer planets observed today. Perhaps, he noted, the perturbing planet was knocked into the inner planets by interactions with other planets far from the central star.

However it started, the resulting chaotic interactions would have created a very eccentric orbit for the third planet, which then also gradually perturbed the second planet’s orbit. Because the outer planet dominates the system, over time it perturbed the middle planet’s orbit enough to deform it slowly into an eccentric orbit as well, which is what is seen today, although every 7,000 years or so, the middle planet returns gradually to a circular orbit.

“This is what makes the system so peculiar,” said Rasio. “Ordinarily, the gravitational coupling between two elliptic orbits would never make one go back to a nearly perfect circle. A circle is very special.”

“Originally the main objective of our research was to simulate the Upsilon Andromedae planetary system, essentially in order to determine whether the outer two planets lie in the same plane like the planets in the solar system do,” said Lystad, who started working with Rasio when she was a sophomore and did many of the computer integrations as part of her senior thesis. “We were surprised to find that, for many of our simulations, it was difficult to tell whether the planets were in the same plane due to the fact that the middle planet’s orbit periodically became so very nearly circular. Once we noticed this strange behavior was present in all of our simulations, we recognized it as an earmark of a system that had undergone planet-planet scattering. We realized there was something much more interesting going on than anyone had found before.”

Understanding what happened during the formation and evolution of Upsilon Andromedae and other extrasolar planetary systems has major implications for our own solar system.

“Once you realize that most of the known extrasolar planets have highly eccentric orbits (like the planets in Upsilon Andromedae), you begin to wonder if there might be something special about our solar system,” Ford said. “Could violent planet-planet scattering be so common that few planetary systems remain calm and habitable? Fortunately, astronomers – led by Geoff Marcy, a professor of astronomy at UC Berkeley – are diligently making the observations that will eventually answer this exciting question.”

The research was supported by the National Science Foundation and UC Berkeley’s Miller Institute for Basic Research.

Original Source: Berkeley News Release