Category Archives: exoplanets

exoplanets

Looking for Earths

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In All the Right Places

Astronomers using the HARPS spectrograph on the 3.6-meter European Southern Observatory telescope in Chile found another planet around Gliese 581. The four known planets are shown here: they have masses of about 1.9 (planet e, left in the foreground), 16 (planet b, nearest to the star), 5 (planet c, center), and 7 Earth-masses (planet d, with the bluish color). The planet farthest out, Gliese 581 d, orbits its host star in 66.8 days, while Gliese 581 e completes its orbit in 3.15 days. (Click to embiggen.)
Astronomers using the HARPS spectrograph on the 3.6-meter European Southern Observatory telescope in Chile found another planet around Gliese 581. The four known planets are shown here: they have masses of about 1.9 (planet e, left in the foreground), 16 (planet b, nearest to the star), 5 (planet c, center), and 7 Earth-masses (planet d, with the bluish color). The planet farthest out, Gliese 581 d, orbits its host star in 66.8 days, while Gliese 581 e completes its orbit in 3.15 days. (Click to embiggen.)

The exoplanet discoveries just keep on rolling in as astronomers use some of the most sophisticated instruments and techniques available to look for them. The latest focus of attention is a small planet only about twice the size of Earth that is rushing like mad around its star.  The planet, called Gliese 581 e is one of four planets found so far orbiting the star Gliese 581.  It turns out, according to team leader and Geneva Observatory astronomer Michel Mayor, that it’s also the lightest exoplanet found so far.

This extraordinary find was announced today at the JENAM conference during the European Week of Astronomy & Space Science, which is taking place at the University of Hertfordshire, U.K.  If you’re a professional astronomer and want to read the paper where these results are discussed, you will be able to find it in a future edition of the research journal Astronomy & Astrophysics (“The HARPS search for southern extra-solar planets: XVIII. An Earth-mass planet in the GJ 581 planetary system”, by Mayor et al., 2009), so keep your eyes peeled for that one.

The main goal of the work done by Mayor and other exoplanet searchers is to find an Earth-like planet orbiting in the so-called “habitable zone” around its star.  That zone is the place where conditions are not too hot, not too cold and safe enough for life to originate and evolve.

The newly found planet “e” around Gliese 581 is not in the habitable zone. However, there’s another planet in the system that is and it could have water.  New observations of the system made by Mayor’s European team let them take a closer spectral look at that planet — called 581 d.  It’s the most distant planet from the star, and orbits in 66.8 days.  According to team member Stephane Udry, “Gliese 581 d is probably too massive to be made only of rocky material, but we can speculate that it is an icy planet that has migrated closer to the star.”

If true, it has migrated right into the habitable zone for that star, and Udry says that the planet could even be covered by a large and deep ocean. That would be very exciting and if this is confirmed, 581 d could be the first serious ‘water world’ candidate around another star. There’s more info and some very cool images and video about this project over at the European Southern Observatory’s website. Check it out!

exoplanets, exploration, Kepler mission

Planet Hunting Will Commence

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First Light for Kepler

Star Cluster NGC 6791 from Kepler First Light Image
NGC 6791 -- Kepler's first-light image. (Click to embiggen.)

Kepler, the planet-hunting satellite, has sent back its first light image —  a 100-square-degree patch of sky that contains a star cluster called NGC 6791. This is only a part of Kepler’s full field of view, but even from this image, it’s clear that Kepler has pretty good eyesight.

The Kepler spacecraft is equipped with a telescope and photometer, and is out there looking for planets like Earth and will be on the  hunt for the next 3.5 years.  It is focused on 100,000 pre-selected stars — and will continuously study their light output to watch for periods when these stars look a bit dimmer.  Such dips in brightness will be a very good indication that planets are crossing in front of the star, blocking out some of the light from their parent stars.

Kepler needs a very precise view to do this — and to be able to spot planets as small as Earth, the images are intentionally blurred slightly. This minimizes the number of saturated stars. Saturation, or “blooming,” occurs when the brightest stars overload individual pixels, causing the signal to spill out into nearby pixels.

The mission scientists and technicians for Kepler are now in a period of calibration and engineering testing, which will help astronomers tweak the focus and adjust its onboard instruments.  When that work is done, the serious work of planet-hunting will get started. It’s going to be a very exciting time for planet-hunters, who are already jazzed by the numbers of planets already found. But, Kepler gives them the chance to seek out Earth-type worlds — and who knows what they’ll find.  Stay tuned!