The Search for Extraterrestrials Narrows

A large number of experts participated recently at the Astrobiology Science Conference, which was held near Houston, Texas. At the meeting, scientists and NASA representatives spoke about the challenges still ahead in discovering forms of life on other planet, both in our solar system and beyond. The participants also addressed the controversy that famed physicists Stephen Hawking set in motion recently, when he said that Earth may be better off not searching for signs of extraterrestrial intelligence.

According to prominent scientists, the best possible places to look for alien life are currently in the process of being pinned down, and addressed in future space missions. The conference was held to mark the 50th anniversary of the quest for life in other places in the Universe. On Wednesday, NASA experts said that the American space agency was at the time considering a number of no less than 28 future space missions, all of which will be aimed at discovering alien life.

“We're interested and prepared to discover any form of life,” explained during a teleconference NASA Headquarters senior astrobiology scientist Mary Voytek. “Astrobiology and the search for life is really central to what we should be doing next in the exploration of the solar system,” added Steve Squyres, who is a planetary scientists at the Cornell University, in Ithaca, New York. The expert is also the principal science investigator of the Mars Exploration Rovers project, which manages the twin geology robots Spirit and Opportunity.

He mentioned that potential targets for astrobiology research could include the Red Planet, Mercury, as well as numerous moons of gas giants such as Jupiter and Saturn, such as Titan, Enceladus and Europa. According to Squyres, a sample-return mission to Mars would prove “invaluable” for this field of research, and would contribute to advancing our knowledge of how the planet looked like before it became the cold, desolate wasteland it is today.

“I personally think if we're ever going to be able to show that there was past life on Mars – if there was past life on Mars – I think we're going to need to study the samples here on Earth rather than [with robots]. I think if we had the rocks back tomorrow and I had them in my lab, I think we could solve this problem,” added University of California in Los Angeles (UCLA) research scientist Bill Schopf, quoted by Space.

NASA's Spitzer Space Telescope Discovers Extrasolar Planet Lacking Methane

PASADENA, Calif. - NASA's Spitzer Space Telescope has discovered something odd about a distant planet -- it lacks methane, an ingredient common to many of the planets in our solar system.

"It's a big puzzle," said Kevin Stevenson, a planetary sciences graduate student at the University of Central Florida in Orlando, lead author of a study appearing tomorrow, April 22 in the journal Nature. "Models tell us that the carbon in this planet should be in the form of methane. Theorists are going to be quite busy trying to figure this one out."

The discovery brings astronomers one step closer to probing the atmospheres of distant planets the size of Earth. The methane-free planet, called GJ 436b, is about the size of Neptune, making it the smallest distant planet that any telescope has successfully "tasted," or analyzed. Eventually, a larger space telescope could use the same kind of technique to search smaller, Earth-like worlds for methane and other chemical signs of life, such as water, oxygen and carbon dioxide.

"Ultimately, we want to find biosignatures on a small, rocky world. Oxygen, especially with even a little methane, would tell us that we humans might not be alone," said Stevenson.

"In this case, we expected to find methane not because of the presence of life, but because of the planet's chemistry. This type of planet should have cooked up methane. It's like dipping bread into beaten eggs, frying it, and getting oatmeal in the end," said Joseph Harrington of the University of Central Florida, the principal investigator of the research.

Methane is present on our life-bearing planet, manufactured primarily by microbes living in cows and soaking in waterlogged rice fields. All of the giant planets in our solar system have methane too, despite their lack of cows. Neptune is blue because of this chemical, which absorbs red light. Methane is a common ingredient of relatively cool bodies, including "failed" stars, which are called brown dwarfs.

In fact, any world with the common atmospheric mix of hydrogen, carbon and oxygen, and a temperature up to 1,000 Kelvin (1,340 degrees Fahrenheit) is expected to have a large amount of methane and a small amount of carbon monoxide. The carbon should "prefer" to be in the form of methane at these temperatures.

At 800 Kelvin (or 980 degrees Fahrenheit), GJ 436b is supposed to have abundant methane and little carbon monoxide. Spitzer observations have shown the opposite. The space telescope has captured the planet's light in six infrared wavelengths, showing evidence for carbon monoxide but not methane.

"We're scratching our heads," said Harrington. "But what this does tell us is that there is room for improvement in our models. Now we have actual data on faraway planets that will teach us what's really going on in their atmospheres."

GJ 436b is located 33 light-years away in the constellation Leo, the Lion. It rides in a tight, 2.64-day orbit around its small star, an "M-dwarf" much cooler than our sun. The planet transits, or crosses in front of, its star as viewed from Earth.

Spitzer was able to detect the faint glow of GJ 436b by watching it slip behind its star, an event called a secondary eclipse. As the planet disappears, the total light observed from the star system drops -- this drop is then measured to find the brightness of the planet at various wavelengths. The technique, first pioneered by Spitzer in 2005, has since been used to measure atmospheric components of several Jupiter-sized exoplanets, the so-called "hot Jupiters," and now the Neptune-sized GJ 436b.

"The Spitzer technique is being pushed to smaller, cooler planets more like our Earth than the previously studied hot Jupiters," said Charles Beichman, director of NASA's Exoplanet Science Institute at NASA's Jet Propulsion Laboratory and the California Institute of Technology, both in Pasadena, Calif. "In coming years, we can expect that a space telescope could characterize the atmosphere of a rocky planet a few times the size of the Earth. Such a planet might show signposts of life."

This research was performed before Spitzer ran out of its liquid coolant in May 2009, officially beginning its "warm" mission.

Other authors include: Sarah Nymeyer, William C. Bowman, Ryan A. Hardy and Nate B. Lust from the University of Central Florida; Nikku Madhusudhan and Sara Seager of the Massachusetts Institute of Technology, Cambridge; Drake Deming of NASA's Goddard Space Flight Center, Greenbelt, Md.; and Emily Rauscher of Columbia University, New York.

JPL manages the Spitzer Space Telescope mission for NASA's Science Mission Directorate, Washington. Science operations are conducted at the Spitzer Science Center at Caltech. Caltech manages JPL for NASA. For more information about Spitzer, visit http://www.spitzer.caltech.edu/spitzer and http://www.nasa.gov/spitzer.

New Technique Can Spot Smaller Exoplanets

Image comment: This image of the planets in the HR8799 system were found using vortex coronagraph
Image credits: NASA / JPL-Caltech / Palomar Observatory

Up until now, methods of detecting exoplanets beyond our solar system could only see space rocks that were very large, and also fairly far away from their parent stars. These limitations occur on account of the fact that the brightness of exoplanets can rarely be observed directly, due to the light the stars they orbit emit. This means that small planets, about the size of Earth, can only be detected with incredible difficulties. However, this class of celestial objects is thought to be the most likely to support alien life. Now, a new observations technology could surpass the previous limitations.

According to the investigators behind the new method, the technique is especially suitable for detecting small exoplanets, that orbit their parent star closer to, or even within, their respective habitable zones. The method can also detect these bodies at larger distances from our solar system than ever before, which could significantly increase the chances of astronomers finding planets that have temperatures suitable for maintaining liquid water on their surface. Experts plan to find these objects using a small instrument called a “vortex coronagraph.”

Unlike other detection methods, which rely on the use of impressively-large telescopes, this device only uses a small portion of an observatory. In a demonstrative study, the technique was used on the 1.5-meter (5-foot) Hale Telescope, located at the Palomar Observatory, in San Diego. The study team, led by NASA Jet Propulsion Laboratory (JPL) expert Gene Serabyn, managed to find three already-discovered planets using this small telescope. The space rocks orbit the star called HR 8799, and they are all gas giants similar to Jupiter, though more massive.

Initially, these bodies were found using the Mauna Kea, Hawaii-based 10-meter (33-foot) telescopes of the W.M. Keck Observatory, and the 8.0-meter (26-foot) Gemini North Observatory. “We managed to see these planets with a telescope that's smaller than one panel on the Keck telescope. What this [vortex coronagraphy] does is it allows you to consider using a much smaller telescope, and something that's much more affordable, to look for Earth-like planets,” the JPL expert tells Space. Details of how the device works can be found in the April 15 issue of the esteemed scientific publication Nature.

New Method of Classifying Planets Proposed

Image comment: Artist's drawing depicting the dwarf planet Haumea, with its tow moons. The body has a prolonged shape that puzzles astronomers

Image credits: A. Feild (Space Telescope Science Institute)

The way the International Astronomical Union (IAU) goes about defining planets is a topic that many are uncomfortable with. A large proportion of all astronomers in the organization do not agree with the definitions by which the IAU decided which space object is classified as a planet, and which as a dwarf planet. This was made very obvious in 2006, when the organization voted – with only a few members in attendance – that Pluto was a dwarf planet, and not a real, full-size one. Now, experts propose a new method of defining what planets are, Technology Review reports.

The international scientific community has been trying to determine the best possible way of defining a planet for many ears, but most propositions on how to do that have thus far fallen short of their original goal. For instance, experts cannot classify an object on a planet based only on size, as throughout the Universe, size varies widely among planets. The IAU currently employs three criteria. The first is that the body needs to be orbiting the Sun, the second is that it must have sufficient mass to have formed a nearly spherical shape, and the third is that it needs to have cleared its orbit.

Pluto was deemed to be meeting the first two criteria, but not the third, because it passes through the orbit of Neptune. But critics say that, if Pluto was not deemed a planet because of this, then neither should Neptune be considered a planet, as it also failed the third criteria. Australian National University in Canberra expert Charles Lineweaver and Marc Norman decided to investigate the matter on their own, and the team now proposes a new approach to defining what a planet is. They basically suggest that any body which is not potato-shaped, and which has a diameter of more than 200 kilometers, can be considered a dwarf planet.

The problem with their approach is the fact that this definition raises the number of dwarf planets in the solar system considerably, while at the same time making the asteroid Vesta – a potato-shaped space rock much larger than 200 kilometers – a cosmic oddity. This method of defining space objects again puts Pluto as the number one dwarf planet, but it's unlikely to sit well with those who want to see the body established to its former “glory”. The main issue here remains elevating interest in this type of research, as more often than not, this translates into increased funding for this type of studies.

Source;- http://www.technologyreview.com/blog/arxiv/25034/

Is densest Kuiper belt object a wayward asteroid?

Quaoar, a large object in the outer solar system, is mostly made of rock, unlike its icy neighbours (Illustration: NASA/G. Bacon/STScI)

A giant rock is walking among the "dirty iceballs" in the outer solar system, a new study suggests. Researchers say it may have journeyed there from the asteroid belt near Mars, or it may have been the victim of a cosmic crash that blasted away its once-icy exterior.

Quaoar was discovered in 2002 in the Kuiper belt, a ring of icy bodies beyond Neptune. At about 900 kilometres across, or 40 per cent as wide as Pluto, it is not the biggest denizen of the belt, but researchers now say it may be the densest.

Wesley Fraser and Michael Brown of Caltech confirmed its size by studying archival images from the Hubble Space Telescope. They also used Hubble images to study the motion of its moon, Weywot, which allowed them to calculate Quaoar's mass.

Combining the size and mass revealed Quaoar's density to be between 2.9 and 5.5 grams per cubic centimetre. That is much higher than that of other Kuiper belt residents like Pluto, which has a density of about 2.0 grams per cubic centimetre.

Quaoar's high density suggests it is made almost entirely of rock, unlike its neighbours, which are a mixture of ice and rock, the researchers conclude. They say the rocky world may be a refugee from the asteroid belt between Mars and Jupiter, thrown outwards early in the solar system's history, when the orbits of the giant planets are thought to have shifted.

'Far-fetched' scenario

Previously, other researchers have suggested that the same upheaval threw some Kuiper belt objects into the asteroid belt, so the new study suggests the migration may have been a two-way street.

But Renu Malhotra of the University of Arizona in Tucson says that hurling Quaoar from the asteroid belt to the Kuiper belt would have left it with an elongated orbit, making it hard to explain why Quaoar is on a nearly circular orbit today.

"I think that's pretty far-fetched," she says.

She favours the other possible explanation that Fraser and Brown suggest – that a collision with another Kuiper belt object blasted off most of Quaoar's ice, leaving behind only its dense, rocky core.

"That kind of thing seems a lot more possible to me," she says, noting that there were probably far more objects in the early Kuiper belt than there are today, making collisions more common in the past.

Journal reference: Astrophysical Journal Letters (in press)

Source:- NewScientist.com

Happy 50th Birthday SETI

SETI's Allen Telescope Array via SETI Institute

Fifty years ago today, on April 8th, 1960, a Cornell astronomy professor named Frank Drake pointed a radio telescope at the star Tau Ceti in the hope of hearing broadcasts from extraterrestrial intelligence. Naturally, he didn't hear anything out of the ordinary. But with this experiment, Drake began the decades-long search for aliens, known as the Search for Extraterrestrial Intelligence (SETI), that celebrates its 50th anniversary today. Over the last half century, SETI has failed at its initial goal of contacting aliens, but succeeded mightily in bringing new attention to astronomy, helping to develop cloud computing, and inspiring generations of new scientists.

In the 1960s, SETI drew considerable interest from NASA, the National Science Foundation, and the famous astronomer Carl Sagan, but 1977 marked the high point for SETI. In that year, Drake and Sagan successfully lobbied NASA to equip the the Voyager Probe with a golden disc inscribed with information about Earth on one side, and recordings of pop, classical, and traditional music on the other. Ideally, when Voyager left our solar system, it would be found by aliens who would decode the disc, learning about our planet's life. It remains the only physical SETI message every sent out into deep space.

Also in 1977, the SETI-operated Big Ear radio telescope received the historic "Wow!" signal, a 72-second-long burst of powerful radio waves. At the time, the scientists interpreted the Wow signal as the only burst ever detected that might have actually originated in an extraterrestrial civilization. Subsequent searches failed to find a repeat of the signal, and in the years since scientists have produced a number of more likely explanations for the signal's source. However, the Wow signal is still the closest SETI ever got to receiving a message from ET.

While SETI obviously failed at finding actual alien intelligence, it continues to inspire to this day. SETI At Home, a screen saver that helped scientists parse through huge amounts of data, set the stage for programs used today by Berkley's biology lab and the Large Hadron Collider. And closer to SETI's original mission, the development of telescope technology advanced enough to detect exoplanets has revitalized the search for ET's in recent years by locating Earth-like planets circling distant stars.

So happy 50th, SETI! Here's to another 50 years as productive as the last, and maybe even finding some little green men in your next half century of groundbreaking research.

A Planet-Like Companion Growing up in the Fast Lane

Hubble Space Telescope (top) and Gemini North (bottom) images of the 2M J044144 system showing the smaller companion at 8:00 position. The companion has an estimated mass of between 5-10 times the mass of Jupiter. In the right panel of both the HST and Gemini images the brighter light from the brown dwarf has been removed to show the companion more clearly.

The cliché that youth grow up so fast is about to take on a new twist. This is due to the discovery of a very young planet-like object (with a mass somewhere between 5-10 times that of Jupiter), paired with a low-mass brown dwarf. What is unique about this system is that the planet-like body appears to have formed in about a million years–more rapidly than some theories of planet formation predict.

Kamen Todorov of Pennsylvania State University and co-investigators made the discovery using the keen visible-light eyesight of the Hubble Space Telescope combined with high-resolution adaptive optics infrared images from the Gemini Observatory. The images of the pair were obtained as part of a survey of 32 young brown dwarfs in the Taurus star-forming region located some 450 light years away. The team’s paper is in press for an upcoming issue of the Astrophysical Journal Letters, http://iopscience.iop.org/2041-8205/714/1/L84.

Identified as 2M044144, the primary brown dwarf is likely about 20 times the mass of Jupiter and separated from the smaller body by about 3.6 billion kilometers – for comparison, Saturn is about 2.25 billion kilometers from the Sun.

However, it’s the age of the smaller object that is most compelling. According to team-member Kevin Luhman of the Center for Exoplanets and Habitable Worlds at Pennsylvania State University, “This is the youngest planetary-mass companion that has been found so far, and its extreme youth provides constraints on how it could have formed. The formation mechanism of this companion in turn can tell us whether it is truly a planet.”

While different processes or combinations may be relevant for each system, here are three possible scenarios for the formation of planetary-mass companions: 1) Dust in a circumstellar disk slowly agglomerates to form a rocky planet 10 times larger than the Earth, which then accumulates a large gaseous envelope; 2) the disk is unstable causing a clump of gas to quickly collapse and form an object the size of a gas-giant planet; or, 3) rather than forming in a disk, a companion forms from the collapse of the vast cloud of gas and dust in the same manner and at the same time as the primary body.

If the last scenario does occur, then this discovery demonstrates that nature can make planetary-mass bodies through the same mechanism that builds stars. This is the likely solution because the planet-like companion is too young to have formed by the first scenario, which is very slow. The second mechanism occurs rapidly, but any disk around this low-mass brown dwarf probably did not contain enough material to make an object with a mass of 5-10 Jupiter masses.

“The most interesting implication of this result is that it shows that the process that makes binary stars extends all the way down to planetary masses. So it appears that nature is able to make planetary-mass companions through two very different mechanisms,” says Luhman. If 2M044144’s companion formed through cloud collapse and fragmentation, as stellar binary systems do, then the companion is not a planet by the definition that planets build up inside disks.

Brown dwarfs are typically tens of times the mass of Jupiter, and they are too small to sustain nuclear fusion and shine as stars do. Low mass objects like these glow primarily due to internal heating from the collapsing material, and they are warmer when very young, as in the case of the 2M044144 system.

Additional evidence to indicate that the new planetary-mass companion formed like a binary star comes from the presence of a nearby small red star that is gravitationally connected to the pair. When the Gemini observations were made, the adaptive optics system used the distant red star as a reference guide star (see background below). In the process, Gemini discovered yet another brown dwarf very close to the distant red star, making 2M044144 a possible member of a quadruple system. Luhman believes that all four objects may have formed in the same cloud collapse: “The configuration closely resembles quadruple star systems, suggesting that all of its components formed like stars,” Luhman said.