Astroblog

Wednesday, April 22, 2009

Welcome, Gliese 581e (Oh, Yeah, Gliese 581d IS in the habitable zone)

Image Credit ESO (click to embiggen).

The Gliese 581 system delivers again. Giese 581 is a red dwarf star 20.4 light years away that until recently boasted the lightest extrasolar planet ever found. At 5 Earth masses, Gliese 581c was not exactly a second Earth, but it and 7 Earth mass Gliese 581d captured the worlds imagination as they seemed to be in the habitable zone of their parent star, where liquid water can exist.

Now the smallest mass planet ever has been discovered around Gliese 581, a 1.9 mass planet Gliese 581e, presumably rocky, that screams around Gliese 581 in a little over three days. At a mere 0.03 Astronomical Units from its star, Gliese 581e is a Mercury-like world, baking in the close embrace of the Red Dwarf.

Importantly, the orbit for Gliese 581d has been refined too. It is now definitely within the habitable zone of its star. Gliese 581d is likely very unlike Earth, and it and Gliese 581c are probably water worlds. The refinement of the orbit of 581d means it is very-likely covered in liquid water, when the planet was first described it seemed more likely it would be an ice world (but Gliese 581c is more likely to be Venus-like).

Unfortunately, even though Gliese 581 is so close that we can almost touch it, astronomically speaking, we won't be travelling there for a while. You can go there virtually though if you have the 3D space rending program Celestia, I have made an ssc file for the Gliese 581 system. If you have Celestia 1.5 and above, the program already comes with Gliese 591b, c and d (you will have to comment b and c out in my file, and comment out d in the extrasolar.ssc file as it has the old orbit).

Download the file Wolf_562.ssc (the alternate name for Gliese 581) and put it in your Celestia extras folder and go exploring.

For the original ESO press release go here. For a PDF of the discovery paper go here. And a Nature News commentary is here.

Naturally the blogosphere has already caught on. Here's Stuart's take, Centauri Dreams, Dynamics of Cats, Starts with a Bang (and his update here), Science After Suneclipse on how long it would take to get to Gliese 581 and the Questionable Authority on what this means for finding alien civilizations (and how much you would weigh on Gliese 581d).

Labels: exoplanet, extrasolar planet, Gliese 581

# posted by Ian Musgrave @ 9:46 pm 1 comments

Thursday, June 07, 2007

No transits for Gliese 581

The news has been officially released at the the annual meeting of the Canadian Astronomical Society at the Royal Military College in Kingston, Ontario. Gliese 581 is a nice stable star, but no transits were detected by MOST. This wasn't really surprising, as there was only between a 1 in 20 and 1 in 50 chance of a transit. Quoting from the press release:

The MOST results ... rule out dips in the starlight down to a level of about 0.1%

that would be caused by a transiting planet roughly the size of the

Earth. That doesn't mean there's no planet, just that from Earth, we

don't see its orbit nearly edge-on. But it does mean we can't directly

measure the size of the planet Gliese 581c, to test models of its

structure. That's the disappointing news.

The encouraging news is that the star itself seems remarkably stable

over the six weeks it was monitored by MOST. The brightness of the star

changed by only a few tenths of a percent over that time. This level of

stability means that this red dwarf star provides a stable source of

light, hence heat, to the surface of planet Gliese 581c. "The climate

there should not be a wild rollercoaster ride that would make it

difficult for life to get a foothold," notes MOST Mission Scientist Dr.

Jaymie Matthews, a professor in the Department of Physics & Astronomy

at the University of British Columbia. "It also suggests the star is

quite old, and settled in its ways, so that the planets around it have

been around for billions of years. We know it took about three and a

half billion years for life on Earth to reach the level of complexity

that we call human, so it's more encouraging for the prospects of

complex life on any planet around Gliese 581 if it's been around for

at least as long."

So, the results while disappointing in that we miss out on finding more about Gliese 581c (or d), but we know a lot of interesting information about the system. I'll blog some of my ideas about this later on. Centauri Dreams also has some good discussion of this report.

Labels: exoplanet, Gliese 581, transit

# posted by Ian Musgrave @ 10:42 pm 0 comments

Wednesday, May 02, 2007

Updated Gliese 581 Celestia file

I've updated the Celestia ssc file for the Gliese 581 system. (The extrasolar system with an Earth-like exoplanet in the habitable zone). I've rejigged the files so there is more information in them, the info URL actually points to the right place now, I've fixed the vesion 1.3-1.4 texture bug and made some of the orbital periods slightly more accurate. Download the file Wolf_562.ssc (the alternate name for Gliese 581) and put it in your Celestia extras folder and go exploring.

Labels: celestia, exoplanet, Gliese 581

# posted by Ian Musgrave @ 7:44 pm 3 comments