Planet 581c

SETI Institute Scientsts Comment on Discovery of Planet 581c

The SETI (Search for ExtraTerrestrial Intelligence) Institute is a scentific non-profit whose mission is "to explore, understand and explain the origin, nature and prevalence of life in the universe."

According to an article on the SETI Institute's  website,

Gliese 581 has been targeted for SETI searches twice in the past with no hint of a radio signal, but this new information may mean a third search with the more powerful Allen Telescope Array.

The article also lists the major media outlets that have quoted SETI Institute scientists, including Frank Drake, on the discovery of Gliese 581c.

Astroprof Blogger: Habitable Planet? Maybe Not!

A blogger who identifies himself as a "college professor teaching physics and astronomy" calls attention to how Gliese 581c may not be "habitable" in the ways we expect them to be.  He notes that "we really don't know how planet form around red dwarf stars... We can't say much of anything about the composition of the planet.  so, how can we call it Earth-like?"  He also points that with a mass 5 times Earth's, and a radius 1.5 times Earth's, acceleration due to gravity would be roughly twice as on Earth, which "would make the planet not very comfortable to life forms like us."

On the matter of the temperature and climate, he notes:

But, there is a more serious concern... This planet, Gliese 581c, is indeed close: about 11 million kilometers from the star. It takes the planet only about 12.9 days to orbit the star. At that distance, it may well be that the planet is tidally locked to the star. That would mean that one side of the planet perpetually faces the star, much like one side of the Moon perpetually faces Earth. In that case, habitability becomes problematic. The side facing the star will be baked. The star will never set. The temperature will rise higher and higher. My back-of-the-envelope calculations suggest a sub-stellar temperature possibly up to 200° C (possibly even much hotter), but certainly well above the boiling point of water. The nighttime temperature would be always well below freezing. Only a tiny zone near the terminator would have any hope of habitability, but even that would be tenuous, and it would be likely wracked by storms of unbelievable intensity... The other possibility might be a coupling with the much larger planet that orbits just a little closer to the star than Gliese 581c. If it were to couple to that planet, then it might rotate fast enough that some hope of habitability might exist. Of course, it still would likely have nothing approximating an Earth climate.

http://astroprofspage.com/archives/889

He concludes though, that planet 581c does "bring hope of finding others that are even more of match for what we expect a habitable planet to be like."

European Southern Observatory Releases Video on the Discovery of Planet 581c

ESO has made available a QuickTime (and iPod) video discussing the discovery of planet 581c.  It's at:

http://www.eso.org/outreach/press-rel/pr-2007/vid-22-07.html

Warning: the video is very large (64MB QuickTime/17MB iPod).  We'll let you know if we find a more compressed version or a local mirror site.

Some highlights from ESO's video:

1. It contains interviews with HARPS principal investigator Michael Mayor and lead author Stephane Udry, both from the Geneva Observatory, so you can see what these two people are like.
2. It also provides an animation which illustrates how 581c was detected using the radial-velocity method.

The video runs about 4 and a half minutes.

European Southern Observatory Issues Definitive Science Release: Astronomers Find First Earth-like Planet in Habitable Zone

The European Southern Observatory (ESO) released a science release on April 25, 2007 announcing their discovery:

http://www.eso.org/outreach/press-rel/pr-2007/pr-22-07.html

It opens:

Astronomers Find First Earth-like Planet in Habitable Zone
The Dwarf Carried Other Worlds Too!
Astronomers have discovered the most Earth-like planet outside our Solar System to date, an exoplanet with a radius only 50% larger than the Earth and capable of having liquid water. Using the ESO 3.6-m telescope, a team of Swiss, French and Portuguese scientists discovered a super-Earth about 5 times the mass of the Earth that orbits a red dwarf, already known to harbour a Neptune-mass planet. The astronomers have also strong evidence for the presence of a third planet with a mass about 8 Earth masses.

Not surprisingly, this science release provides definitive details on planet 581c -- its size (a radius 50% longer than earth's), orbit (13 days), and distance to its sun (14 times closer than Earth is to its).  The release also explains that the host star, Gliese 581, is "among the closest 100 stars to us... only 20.5 light years away in the constellation Libra."  Gliese 581, a red dwarf star, has a mass only one third the mass of our sun and is "intrinsically at least 50 times fainter." 

The release closes with this optimistic note by HARPS principal investigator Michel Mayor:

"And we are confident that, given the results obtained so far, finding a planet with the mass of the Earth around a red dwarf is within reach."

We certainly hope so.

Space.com: Closer to the Holy Grail

In this interesting article at Space.com, at: http://www.space.com/scienceastronomy/070424_exoplanet_side.html

Ker Than provides a nice overview of different planet hunting techniques:

The scores of newly identified exoplanets are the result of the numerous techniques now available to planet-hunting scientists. Peg 51 b was discovered using the radial velocity technique whereby astronomers look for slight wiggles in a star’s motion caused by the gravitational tug of orbiting planets. This so-called wobble technique was also used to spot Gliese 581 C.

The transit method, another tool used by planet hunters, requires that a planet pass directly in front of its star as seen from Earth. The planet blocks some of the star’s light that would reach Earth, and this slight dip in starlight can be used to calculate the planet’s size.

Scientists can also spot alien worlds by observing the way a planet-harboring foreground star bends and brightens light from a background star. This technique is called gravitational microlensing. The presence of an extrasolar planet can also be inferred from the dusty debris disks that shroud some stars.

The article also overviews up-and-coming missions by NASA and the European Space Agency to find earth-sized planets:

Stakes in the search for extrasolar planets have risen even higher with the recent launch of the European Space Agency’s planet-hunting spacecraft, COROT, which will use the transit technique to monitor thousands of stars simultaneously. Over the course of its two-and-a-half year mission, it is expected to find up to 40 new rocky worlds, along with tens of new gas giants.

The NASA Kepler mission, scheduled to launch next year, is even more ambitious. The spacecraft would be the first capable of detecting Earth-sized planets in our galaxy. NASA’s Terrestrial Planet Finder mission is currently on the backburner indefinitely, but it would have the same capability as Kepler. If launched, the satellites will mark an important step in the quest to answer one of humanity’s oldest questions: Are we alone in the universe?

NY Times Coverage, Dr. Sasslove: "These Kinds of Planets Are Very Common."

According to Dennis Overbye's article in Wednesday's NY Times article:

http://www.nytimes.com/2007/04/25/science/space/25planetcnd.html?hp

According to models of planet formation developed by Dr. Sasselov and his colleagues, such a planet should be about half again as large as the Earth and be composed of rock and water, what the astronomers now call a “super Earth.”

The most exciting part of the new find, Dr. Sasselov said, is that it “basically tells you these kinds of planets are very common.” Because they could stay geologically active for billions and billion of years, Dr. Sasselov said he suspects that such planets could be even more congenial for life than the Earth. NASA’s coming Kepler mission, he added, would probably find hundreds of these super Earths.

Illustration of Planet 581c by the European Southern Observatory

Welcome!

"On the treasure map of the universe, one would be tempted to mark this planet with an X."   -- Xavier Delfosse

This blog is all about the discovery of planet 581c, which, so far, is the planet most likely to support extraterrestrial life.

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