Thursday, February 22, 2007

Clouds, But No Water, Detected On Distant Planet - space.com

http://space.com/scienceastronomy/070221_exoplanet_atmosphere.html


By Ker Than
Staff Writer
posted: 21 February 2007
01:0
1 pm ET

The most detailed analysis ever of light from the atmospheres of planets outside our solar system has turned up no evidence of water but possible hints of clouds, scientists said today.

“We’re getting our first sniffs of air from an alien world,” said David Charbonneau of the Harvard-Smithsonian Center for Astrophysics. “And what we found surprised us. Or more accurately, what we didn’t find surprised us.”

Using NASA’s infrared Spitzer space telescope, Charbonneau and his team studied a so-called hot Jupiter planet [image] called HD 189733b. Hot Jupiters are large gas giants like our own Jupiter, but they orbit so close to their parent stars that they are extremely hot. A year on HD 189733b is only 2.2 Earth days long and the planet is a broiling 1,700 degrees Fahrenheit. HD 189733b is located about 60 light years away in the constellation Vulpecula.

The technology to tease apart the light from a distant planet and star is not available yet, so scientists use a different trick [image].

“Instead of separating the [light from the planet and star] in space, we separate them in time,” Charbonneau explained. “We wait for the planet to pass out of view behind the star, and then we measure the brightness of the star very carefully. Then we gather data at any other time, when both the planet and star are in view. If you take their difference, then whatever’s left over has got to be the light from the planet.”

In 2001, Charbonneau’s team used the Hubble Space Telescope and a different technique to detect small amounts of sodium in the atmosphere of an exoplanet. The discovery marked the first time that astronomers had ever detected the atmosphere of a planet orbiting another star.

“Now we’re able to look over many different colors,” Charbonneau explained. “In the past, we had to target this one wavelength and this one feature due to this one atom. It was exciting at the time, but these data that we’re presenting now are much more informative.”

The study by Charbonneau's team is detailed online in the journal Astrophysical Journal Letters .

No signs of water

After obtaining the light spectrum of HD 189733b, Charbonneau’s team scanned it for tell-tale “fingerprints” of specific molecules.

Theory predicts that hot Jupiters contain large amounts of water vapor and also methane. Planets form from the same material as their stars, and stars like the one HD 189733b orbits contain many different elements, including hydrogen, helium, carbon and oxygen. Therefore, these elements must also be present in the makeup of planets around the star.

On hot Jupiters, there is “so much hydrogen and oxygen that they will react and turn into a water molecule. At those pressures, it’s inevitable,” Charbonneau told SPACE.com.

Similarly, carbon and hydrogen are thought to combine on hot Jupiters to form methane.

However, to the researchers’ great surprise, no signs of either of these two molecules were detected.

“We expected that the planet would appear fainter, due to absorption by water molecules in the atmosphere,” Charbonneau said. “That was a very strong prediction and made by many different groups that had tried to predict what these atmospheres would be like.”

High Clouds and hidden water

Results obtained by another team suggest the water and methane are present, but hidden by thick clouds.

A team led by Jeremy Richardson of NASA’s Goddard Space Flight Center also used Spitzer to obtain the spectrum of HD 209458b, another hot Jupiter located about 150 light years away in the constellation Pegasus.

The spectrum Richardson’s team obtained also showed no signs of water or methane, but it did reveal hints of silicate—molecules containing silicon and oxygen. On Earth, silicates are a major component of rocks. On hot Jupiters, under scorching temperatures, silicates would exist as tiny dust grains that could coalesce to form clouds.

The study by Richardson's team is detailed in the Feb. 22 issue of the journal Nature.

“It might explain why we don’t see the water,” Charbonneau said. “If there is a high cloud deck, it would prevent us looking down into the atmosphere.”

Mark Swain, a researcher at NASA's Jet Propulsion Laboratory and the leader of another team which independently analyzed HD 209458b, agrees that there are probably clouds on the hot Jupiter but is not convinced the clouds are made of silicate.

“In our view, the silicate case is not proven,” Swain said. “We find [the spectrum] to be consistent with featureless thermal emissions from dust.”

“I think it’s certainly true that we don’t understand the details of what we see,” Richardson said. “The feature that we see is real. Is it possible that something else could cause that feature? Maybe. Maybe a different element. I think it’s probably silicates.”

Still exciting

Further studies of HD 189733b, HD 209458b and other hot Jupiters are planned to help clear up the mystery.

“Right now, it’s a puzzle,” Charbonneau said. “With a few more puzzle pieces, the picture should become clearer.”

Despite not finding evidence for water on the two hot Jupiters, the ability to do so is itself exciting, said Alan Boss, a planet-formation theorist at the Carnegie Institution of Washington who was not involved in any of the studies.

“This is the first time that we have been able to look for water in the atmosphere of a distant extrasolar planet,” Boss said in an email interview. “The NASA mantra for looking for life on Mars is ‘follow the water’ and the same holds true for extrasolar planets. Looking for water will be one of the main goals of the Terrestrial Planet Finder (TPF), and this new result just whets our appetite for what is to come when TPF flies.”

Monday, February 19, 2007

"Gravity Tractor," Super Telescopes Enlisted to Battle Killer Asteroids - National Geographics

http://news.nationalgeographic.com/news/2007/02/070217-asteroid-impact_2.html

Elizabeth Svoboda in San Francisco, California
for National Geographic News

February 17, 2007

A giant asteroid named Apophis could be on a trajectory to careen into Earth in 2036. That was the prediction NASA scientists made in 2004, suggesting a 1 in 37 chance that the space rock would hit our planet.

The danger has since receded—the revised likelihood that Apophis will hit Earth is 1 in 45,000. But the close call has galvanized efforts among scientists to predict and hopefully prevent a potentially apocalyptic impact.

Asteroid impact image


A slate of new proposals for addressing the asteroid menace was presented today at a meeting of the American Association for the Advancement of Science in San Francisco.

The aim, researchers said, is to defend the planet from an asteroid strike such as the one that slammed into Mexico's Yucatán peninsula some 65 million years ago—a cataclysmic event that many scientists think caused the extinction of the dinosaurs.

"There are 127 near-Earth objects we know about that have some chance of hitting us," said Russell Schweickart, a former Apollo astronaut and founder of the Houston, Texas-based Association of Space Explorers.

"You have to act when it looks like things are going to happen. If you wait until you're certain, it's going to be too late."

"Gravity Tractor," Super Scopes

Edward Lu, an astronaut and physicist at NASA, has developed a novel way to nudge off course any asteroids that appear to be headed for Earth.

Lu's proposed "gravitational tractor" is a spacecraft so massive—up to 20 tons (18 metric tons)—that it could divert an asteroid's path just by thrusting its engines in a specific direction while in the asteroid's vicinity.

"You don't aim your engines at the asteroids, you aim them to the side," he said. "That enables you to tow the asteroid just by the force of gravity."

In order for the gravitational tractor to work effectively, Lu said, international authorities would have to decide to use it long before an anticipated impact.

"You want many years or even decades of notice," he said. "It's like billiards—when you make a slight change before the bank shot, it creates a big change [in where the ball goes]."

Lu thinks other proposed interventions, such as detonating a nuclear bomb near an asteroid, would create more danger for Earth than they would avert.

  • "There's a possibility of breaking chunks off, and even small chunks could cause tremendously bad effects," he said.

(See an interactive feature on asteroid impacts on Earth.)

Scientists also described two massive new survey-telescope projects to detect would-be killer asteroids.

One, dubbed Pan-STARRS, is slated to begin operation later this year. The project will use an array of four 6-foot-wide (1.8-meter-wide) telescopes in Hawaii to scan the skies.

The other program, the Large Synoptic Survey Telescope in Chile, will use a giant 27.5-foot-wide (8.4-meter-wide) telescope to search for killer asteroids. This telescope is scheduled for completion sometime between 2010 and 2015.

(Related news: "Google Partners With High-Tech Telescope to Map Universe" [January 10, 2007].)

When both of these new telescope projects go online, they will be able to detect objects much fainter than anything today's scopes pick up, the scientists said.

David Morrison, an astronomer at NASA's Ames Research Center, said that "the rate of discoveries is going to ramp up. We're going to see discoveries being made at 50 to 100 times the current rate."

"You can expect asteroids like Apophis [to be found] every month."

International Plans

The influx of new discoveries will likely increase public anxieties about the asteroid threat, which makes a concrete scientific plan of action all the more necessary, the experts said.

In the wake of the Apophis incident, many lawmakers have become convinced of the importance of devoting more attention to asteroid searches.

In 2005 the U.S. Congress amended the Space Act to entrust NASA with the specific responsibility to "detect, track, catalog and characterize" asteroids and other near-Earth objects.

But to some scientists, these efforts aren't enough.

Schweickart, the former astronaut, thinks the United Nations needs to draft a treaty detailing standardized international measures that will be carried out in response to any asteroid threat.

His group, the Association of Space Explorers, has started building a team of scientists, risk specialists, and policymakers to draft such a treaty, which will be submitted to the UN for consideration in 2009.

Schweickart believes the uncertainty involved in predicting the path of an incoming asteroid makes a coordinated global response essential.

"When you look at where something like Apophis is going to hit, it's not going to be a single point, it's going to be a line of potential points," he said. "Therefore this is going to be inherently an international decision.

"We can't prevent a hurricane or a tornado," he continued. "But we can prevent an asteroid impact, and we can do it by slightly reshaping the solar system to enhance the survival of life on Earth.

"If we don't do that, we're not that far past the dinosaurs."

Saturday, February 17, 2007

As death increases, compassion recedes - LiveScience

http://www.msnbc.msn.com/id/17186270

Study finds mass death fails to spur emotion the way one tragedy can


By Sara Goudarzi
Staff Writer
Updated: 11:56 a.m. ET Feb. 16, 2007

SAN FRANCISCO - While a person's accidental death reported on the evening news can bring viewers to tears, mass killings reported as statistics fail to tickle human emotions, a new study finds.

The Internet and other modern communications bring atrocities such as killings in Darfur, Sudan into homes and office cubicles. But knowledge of these events fails to motivate most to take action, said Paul Slovic, a University of Oregon researcher.

People typically react very strongly to one death but their emotions fade as the number of victims increase, Slovic reported here yesterday at the annual meeting of the American Association for the Advancement of Science.

"We go all out to save a single identified victim, be it a person or an animal, but as the numbers increase, we level off," Slovic said. "We don't feel any different to say 88 people dying than we do to 87. This is a disturbing model, because it means that lives are not equal, and that as problems become bigger we become insensitive to the prospect of additional deaths."

Human insensitivity to large-scale human suffering has been observed in the past century with genocides in Armenia, the Ukraine, Nazi Germany and Rwanda, among others.

"We have to understand what it is in our makeup — psychologically, socially, politically and institutionally — that has allowed genocide to go unabated for a century," Slovic said. "If we don't answer that question and use the answer to change things, we will see another century of horrible atrocities around the world."

Slovic previously studied this phenomenon by presenting photographs to a group of subjects. In the first photograph eight children needed $300,000 to receive medical attention in order to save their lives. In the next photograph, one child needed $300,000 for medical bills.

Most subjects were willing to donate to the one and not the group of children.

Friday, February 16, 2007

Live Earth

A major event yesterday was a press conference announcing the organization of a massive global warming awareness event called "Live Earth".

"Live Earth is a series of concerts planned for July 7, 2007 (7/7/07) to raise awareness of global climate change. An anouncement was made on February 15, 2007 by former U.S. Vice President Al Gore and other activists as part of a campaign called Save Our Selves (SOS). The concert series is modeled after the 1985 Live Aid concerts and 2005's Live8." (Wikipedia)

Here is the announcement's video
http://liveearth.msn.com/?GT1=9033

Sailom

Monday, February 12, 2007

US claims against Iran: why now? - BBC News

http://news.bbc.co.uk/2/hi/middle_east/6353489.stm




Analysis
By Paul Reynolds
World affairs correspondent, BBC news website

In October 2005, the then British ambassador to Iraq William Patey told reporters in London that Iran had been supplying technology used to kill British troops in Basra.

US photo of bomb damage from an EFP - explosively formed penetrator
US photo of bomb damage from an EFP - explosively formed penetrator

He said he had complained to the Iranian ambassador in Baghdad about it.

The claim was that elements connected to the Shia militia in the south, the Mehdi army, had been using specially shaped charges, in which the force of the explosion is directed narrowly in one direction, thereby enabling it to penetrate armoured vehicles.

No evidence was produced, other than a suggestion that the Iranian-supported Lebanese group Hezbollah had also used such charges, so the common origin had to be Iran.

US officials have made similar claims over the last year. General George Casey, the then US commander in Iraq, said so in June 2006.

Evidence

In a briefing in Baghdad on Sunday, US military and intelligence officers finally laid out their evidence.

The question has to be asked as to why it has taken at least 14 months for this to happen.

So, why now?

If you take the claims at face value, the reason is that only now has the evidence become substantial enough to be made public. The number of attacks is said to have grown as well, so that is another explanation put forward for going public now.

But there are other possibilities as well.

Softening up?

For a start, the fear among some is that the US is softening up world opinion for an attack on Iran. Such an attack would be aimed at Iran's nuclear facilities.

At the moment, the US lacks a casus belli and by claiming that Iran is responsible for killing USA troops, it could be laying the groundwork for a 'self-defence' justification.

Vehicle burning after roadside bombing

The new chairman of the Senate Intelligence Committee, Senator John Rockefeller said recently: "To be quite honest, I'm a little concerned that it's Iraq again."

There is also the fact that the US is launching its 'surge' policy of moving extra troops into Baghdad. These claims are being made against Shia militias, including the Mehdi army, one of the main targets of the latest policy.

Blaming Shia Iran for supporting Iraqi Shia militias makes it easier for the US to sell that policy at home and abroad.

Blaming others

Then there is the old tactic of blaming someone else for your own problems.

Many people will not distinguish between the Shia militias that Iran is said to supply - and which have ties to the Iraqi government - and the Sunni insurgents who have been the cause of much of the violence.

The allegedly Iranian supplied bombs are said to have caused the deaths of 170 American soldiers, but overall 2497 soldiers have been killed in hostile incidents, most of them at hands of the Sunnis.

The claim serves the purpose of helping to lay the blame for the whole insurgency at Iran's door.

There are also other possible reasons for this timing.

Council deadline

The UN Security Council has laid down that Iran must suspend its enrichment of uranium by 21 February. If it does not, and if the International Atomic Energy Agency confirms this, the resolution says that further economic sanctions will be considered.

The officials said such an assertion [that Iran was the source of components for the explosive devises] was an inference based on general intelligence assessments
New York Times
The US is preparing to argue for tougher sanctions, so making claims against Iran over Iraq might help it in its arguments that Iran is a threat.

On the wider front, the Bush administration is engaged in a campaign against the Iranian government in order to isolate it and eventually maybe see its end under internal pressure from the Iranian people.

The latest claims against Iran could be a part of that campaign.

The claims

What of the claims themselves?

They are based on physical evidence, from bombs and their effects. The bombs now even have their own name and acronym - explosively formed penetrators or EFPs.

Previously they had been lumped in the generalised description of IEDs - improvised explosive devices.

The implication is that now they are less improvised and more planned.

They are said to be provided by Iran in kit form and to be smuggled across the often-open border.

However the officials who presented the evidence could not make a direct link to Iran.

"The officials said such an assertion was an inference based on general intelligence assessments," stated the New York Times.

They did make much of the detention in Irbil of five Iranians who were said to be members of the Quds force of the Iranian revolutionary Guards.

The Quds (the word means Jerusalem) force was said by the US officials to be controlled directly by the "highest levels of the Iranian government".

That last statement is significant in that the US is now making a charge against the Iranian government itself, not just against its agents.

Scepticism

Against the inference that this all comes from Iran is the concept that Iraqis themselves would be capable of copying a design and therefore do not need to get bombs from Iran.

And there have been a number of news reports over the last year expressing scepticism, even among military personnel, about the link to Iran.

The Washington Post reported last October that British troops in the south doubted the claim.

A year ago, the London Times said that British officers in Basra had stopped making any such claim, saying only that the technology matched bomb-making found elsewhere in the Middle East, including Lebanon and Syria.


Paul.Reynolds-INTERNET@bbc.co.uk

Thursday, February 08, 2007

Thai woman tells of 25-year detour after catching wrong bus - AFP

http://news.yahoo.com/s/afp/20070208/od_afp/thailandmissingoffbeat

by Rapee Mama Thu Feb 8, 2:55 AM ET

DUSONGYO, Thailand (AFP) - A Thai mother who was lost for 25 years after catching the wrong bus home has spoken of her ordeal after being reunited with her family thanks to simple song.


The last time Jaeyaena Beuraheng saw her seven children was in 1982 when she left south Thailand on one of her regular shopping trips across the border to nearby Malaysia.

She never returned, and police later told her family that she had apparently been killed in a traffic accident.

In fact, Jaeyaena had simply taken the wrong bus home -- an error that would have been easy to fix except that she only speaks the local dialect of Malay known as Yawi, according to officials at the homeless shelter where the 76-year-old has lived for two decades.

"I didn't tell anybody where I was going on that day, because I went there quite often," she told AFP, crying as she spoke.

She was heading home from her shopping trip when she mistakenly hopped on a bus to Bangkok, some 1,150 kilometers (700 miles) north of her home in Narathiwat province.

In Bangkok, unable to read Thai and speaking a language few Thais can understand, she again took a wrong bus, this time to Chiang Mai, another 700 kilometers (430 miles) further north.

There she ended up as a beggar for five years, until she was sent to a homeless shelter in the central Thai province of Phitsanulok in 1987.

"I thought I would die in Phitsanulok. I thought about running away many times, but then I worried I would not be able to make it home. I really missed my children," Jaeyaena said.

Officials at the shelter told AFP that she was known as "Auntie Mon," because her speech sounded similar to the language of ethnic Mon living along the border with Myanmar.

But still no one could understand her, until last week when three health students from Narathiwat arrived on an exchange program to research the problem of homelessness at the shelter.

She sang a song for the visitors, one that the staff at the shelter had often heard but did not understand.

"She sang her same old song, one that nobody could understand until those three students from Narathiwat told us that she was sing in Yawi, a Malay dialect," the official said.

"So we asked them to talk to her and find out if she had relatives," official said.

Jaeyaena told the students that she had a Malaysian husband and seven children, recounting her entire story of the bus and how she had become lost in northern Thailand.

Her shocked family sent her youngest son and her eldest daughter to meet her and bring her home on Tuesday, the official said.

"She remembered all of her children's names. But at first she couldn't recognise her youngest son, but she recognised her eldest daughter," said the official, who was at their reunion.

Her children took her back to their family home in Dusongyo village, in a remote corner of Narathiwat, where her children and grandchildren were still hugging and kissing her two days after her return.

Wednesday, February 07, 2007

Couple still hugging 5,000 years on - MSNBC

http://www.msnbc.msn.com/id/17011786

Image: Eternal embrace
Enrico Pajello / Reuters
A pair of human skeletons lie in an eternal embrace at an Neolithic archaeological dig site near Mantova, Italy. Archaeologists in northern Italy believe the couple was buried 5,000-6,000 years ago, their arms still wrapped around each other in an eternal embrace.


Saturday, February 03, 2007

Mammoth Cloud Engulfs Titan’s North Pole - space.com

http://www.space.com/scienceastronomy/070202_titan_moon.html



By Ker Than
Staff Writer
posted: 02 February 2007
10:43 am ET

A mammoth cloud half the size of the contiguous United States and spotted on Saturn’s moon Titan might be what’s filling up lakes discovered there last year, scientists say.

“This cloud system may be a key element in the global formation of organics and their interactions with the surface,” said study team member Christophe Sotin of the University of Nantes, France.

Imaged by NASA’s Cassini spacecraft on Dec. 29, 2006, the cloud [image] is about 1,500 miles (2,400 km) in diameter and engulfs Titan’s entire north pole. It only recently became visible, emerging from a shadow as winter turns to spring on the moon.

Unlike Earth’s clouds, which contain mostly water vapor, the Titan clouds are thought to consist of ethane, methane and other organics.

Scientists had predicted the existence of such a cloud system, but one had never been imaged in such detail before.

Cassini spotted partially filled lakes on Titan’s north pole last summer. Scientists speculated that methane rains down onto the moon’s surface to form lakes and then evaporates to form clouds, in what they called the “methane-ologic cycle.” The new finding supports this idea.

Ground-based observations show the Titan cloud system comes and goes with the seasons. A season on the Saturn moon is equivalent to about seven Earth years. Scientists speculate such cloud activity can last for as long as 25 Earth years before nearly vanishing for four to five years and then reappearing for another 25 years.

The same cloud system observed last December was still there two weeks later during a Jan. 13, 2007, flyby. Scientists expect the newly spotted cloud to linger for several years, possibly shifting down to Titan’s south pole as the seasons change.

“With 16 more flybys to come this year," said study team member Stephane Le Mouelic, also of the University of Nantes, "we should have the opportunity to monitor the evolution of this cloud system over time.”

Friday, February 02, 2007

U.N. panel says global warming man-made - Reuters

http://today.reuters.co.uk/news/CrisesArticle.aspx?storyId=L01604940&WTmodLoc=World-R5-Alertnet-2

By Gerard Wynn and Alister Doyle

PARIS (Reuters) - The U.N. climate panel issued its strongest warning yet on Friday that human activities are heating the planet, adding pressure on governments to do more to combat accelerating global warming.

The IPCC, the most authoritative group on warming grouping 2,500 scientists from more than 130 nations, predicted more severe rains, melting glaciers, droughts, heatwaves and rising sea levels, especially if Antarctica or Greenland thaw.

The final text said it was "very likely" -- or a probability of more than 90 percent -- that human activities led by burning fossil fuels explained most of the warming in the past 50 years.

That is a toughening from the last report, in 2001, when the IPCC said the link was "likely", or 66 percent probable. Signs of change range from drought in Australia to record high January temperatures in Europe.

"February 2, 2007 may be remembered as the day the question mark was removed from whether (people) are to blame for climate change," Achim Steiner, the head of the U.N. Environment Programme, told a news conference.

He urged governments to inject more momentum into stalled talks on long-term cuts in emissions. Greenhouse gas levels in the atmosphere have not been higher in 650,000 years.

"We are in a sense doing things that have not happened in 650,000 years, based on the scientific evidence," Rajendra Pachauri, the head of the IPCC, told a news conference.

A 21-page summary of scientific findings for policy makers outlines wrenching change such as a possible melting of Arctic sea ice in summers by 2100 and says it is "more likely than not" that greenhouse gases have made tropical cyclones more intense.

The report predicts a "best estimate" that temperatures would rise by between 1.8 and 4.0 Celsius (3.2 and 7.8 Fahrenheit) in the 21st century, within a likely range from 1.1 to 6.4 Celsius.

Temperatures rose 0.7 degrees in the 20th century and the 10 hottest years since records began in the 1850s have been since 1994.

U.N. officials hope the report will prompt governments -- led by the United States, the top emitter -- and companies to do more to cut greenhouse gases, released mainly by burning fossil fuels in power plants, factories and cars.

CORAL ATOLLS

Many backers of the U.N.'s Kyoto Protocol, a plan binding 35 industrial nations to cut emissions of greenhouse gases by 2012, want outsiders to get more involved. The United States and China are not bound by Kyoto targets.

The head of the U.S. delegation said that President George W. Bush's policies, braking the rise of emissions rather than cutting them, were working.

"The President has put in place a comprehensive set of policies to address what he has called the 'serious challenge' of climate change," Sharon Hays, Associate Director of the White House Office of Science & Technology Policy, told Reuters.

Bush pulled out of Kyoto in 2001, saying caps would harm the economy and that Kyoto unfairly omitted developing nations from a first period to 2012. He focuses instead on big investments in technologies such as hydrogen and biofuels.

The President of Kiribati, a group of 33 Pacific coral atolls threatened by rising seas, said time was running out.

"The question is, what can we do now? There's very little we can do about arresting the process," President Anote Tong said.

The report projects a rise in sea levels of between 18 and 59 centimetres (7 and 23 inches) in the 21st century -- and said that bigger gains could not be ruled out if ice sheets in Antarctica and Greenland thaw.

Some leading scientists had criticised an earlier draft for cutting the range after the 2001 forecast a rise between 9 and 88 cms by 2100. Rising seas threaten countries such as Kiribati and cities from Shanghai to Buenos Aires.



© Reuters 2007. All Rights Reserved.

Thursday, February 01, 2007

Neptune May Have Thousands of Escorts - space.com

http://by127fd.bay127.hotmail.msn.com/cgi-bin/getmsg?msg=C9308900-AB37-4AB1-BBBB-D0F604133557&start=0&len=10289&imgsafe=y&curmbox=00000000%2d0000%2d0000%2d0000%2d000000000001&a=7e0d96477eba89b16e22cc54e8d37e6ffa3b5268a5ed312dca29a9ac967f870a




By David Powell
Special to SPACE.com
posted: 30 January 2007
06:01 am ET

Neptune may be escorted in its orbit by thousands of asteroid-like objects, perhaps more than exist in the entire asteroid belt.

So far, five of these enigmatic bodies, known as Trojans, have been found at one of Neptune’s Lagrange points. These are places where the gravity of a planet and that of the Sun interact to create an area of gravitationally stability.

Jupiter’s Lagrange regions are home to legions of Trojans, and around 2,000 cluster at these gravity graves along Jupiter's orbit 60 degrees ahead and 60 degrees behind the gas giant.


Lagrange points exist in any two-body system. Find out how they work.


The first Neptune Trojan was discovered in 2001 as part of the NASA funded Deep Ecliptic Survey at the Lagrange region 60 degrees and 3.1 billion miles (5 billion kilometers) ahead of Neptune.

A further three Neptune Trojans between 37 and 87 miles (60 and 140 kilometers) in diameter and shaded a pale red color have since been identified by Scott Sheppard of the Carnegie Institution of Washington and Chadwick Trujillo of the Gemini Observatory in Hawaiiusing the 6.5-meter Magellan telescope in Chile.

Despite their diminutive size and brightness, the Neptune Trojans quickly betrayed their existence by their distinct motion against background stars. The most recent Trojan discovered by Sheppard and Trujillo is moving at an unusual inclination of 25 degrees relative to the plane of the solar system (the ecliptic).

”The sky we covered searching for Neptune Trojans was all within 1.5 degrees of the ecliptic,” Sheppard said. “High inclination objects will spend the majority of their time off the ecliptic. Thus detecting a high inclination Trojan in our survey suggests there is a large population of such objects. In fact, the high inclination objects appear to outnumber the low inclination objects by a ratio of four to one."

If so, there would be swarms of Trojans accompanying Neptune, perhaps up to twenty times more than at Jupiter. The sheer number of Trojans Neptune is thought to harbor reveal that these objects are an established part of Neptune’s entourage, dating back to shortly after the planet’s formation.

“Neptune cannot currently efficiently capture Trojans for long periods of time,” Sheppard said. “Just after the planet formation epoch Neptune's orbit was likely much more eccentric due to its interactions with the other planets. Neptune's interactions with the myriad small bodies around its orbit which included comets, Kuiper Belt objects and other debris which formed nearby would have slowly circularized Neptune's orbit.”

This process would have trapped many diverse objects at the Neptune Lagrange points irrespective of their inclination. This diversity is exciting as in 2014 we may get the opportunity to see a Trojan up close courtesy of the New Horizons spacecraft currently en-route to Pluto.

“If a Neptune Trojan could be found which the New Horizons spacecraft could image it would be one of the highlights of the mission," Sheppard said. "The Neptune Trojans are very faint and thus hard to observe from our location on Earth. Thus little is known about their surface properties or composition. The Neptune Trojans may be a unique type of solar system object of which no other stable reservoir currently exists."

At present this flyby of a Neptune Trojan is far from a certainty due to the fact that New Horizons will pass 60 degrees behind Neptune through the trailing Lagrange region known as “L5” where no Trojans have yet been identified.

”We are attempting to discover possible Neptune L5 Trojans, but because of the high background star confusion it will be a tough task for the next several years," Sheppard said. "The constraints on the New Horizons spacecraft are also severe since it will not be able to maneuver too far from its current trajectory. Thus, there is only a very low probability that a Neptune Trojan happens to be in a favorable location for the spacecraft to encounter."