79Views11Replies

Author Options:

Terrestrial mass planet measured orbiting nearby red dwarf Answered

From Science Magazine:
A group of astronomers today announced the discovery of the least massive planet yet detected outside of our solar system. It is lightweight enough--between two and three times the mass of Earth--to almost certainly be rocky like Earth rather than a huge ball of gas. Although the planet orbits too close to its star to be habitable, a new analysis of one of its neighbors suggests a world with deep oceans.

The observation of Gliese 581e, made with the usual radial-velocity residuals fit, is of a terrestrial-mass planet orbiting insanely close to a red dwarf star. Nevertheless, it marks a substantial improvement (a factor of three in mass) in the precision of the radial-velocity technique.

Read the whole article (let me know if it's password protected) for details.

Another news article (including a very nice diagram of the habitable zone as a function of the mass of Gliese 581) is available from Science News.

Tags:Gliese

Discussions

0
None
Gjdj3

10 years ago

That's cool! Just one question (I don't know much about astronomy). Why is its proximity to its sun so "insane"?

0
None
kelseymhGjdj3

Reply 10 years ago

It orbits the star in 3.15 days. In other words, that's how long its year is! The distance (according to Wikipedia) is 0.03 AU, or 4.5 million kilometers.

0
None
Gjdj3kelseymh

Reply 10 years ago

Haha, wow that is close.

0
None
lemonie

10 years ago

Bit too hot, and close! What more do we know about Gliese 581 d? L

0
None
kelseymhlemonie

Reply 10 years ago

Fifth paragraph of the above article (did the link work for you?):
But the group also announced a correction to their calculated orbit for Gliese 581 e's massive planetary neighbor, Gliese 581 d, bringing it in from an 83-day orbit to a 67-day orbit. That puts it in the habitable zone, where it would be warm enough for any water to be liquid but not so hot as to boil it away. Gliese 581 d "could even be covered by a large and deep ocean," team member Stephane Udry of the Observatory said in a statement. "It is the first serious 'water world' candidate."

Note that the letters are assigned in order of discovery, not order of distance.

0
None
lemoniekelseymh

Reply 10 years ago

Yes I did read that, I meant more by way of planetary mass, diameter and any other information? I did have a quick look on the site but "d" turned up as various -ed's

L

0
None
kelseymhlemonie

Reply 10 years ago

Oh, sorry. Gliese 581d is estimated at about 7mEarth . According to the Wikipedia articles on the system and planets, the orbital plane is too inclined for decent transits. Without a transit light curve, getting the diameter (and hence a tighter mass constraint than m sini) is not possible.

0
None
lemoniekelseymh

Reply 10 years ago

Thanks for the update, I hadn't thought to try Wikipedia. L

0
None
kelseymhlemonie

Reply 10 years ago

For many things, Wikipedia is suspect at best, and pure crap at worst. My experience with narrow scientific topics, at least those which are not "popularly controversial" is that it's pretty good. The articles tend to be written by people in the field who are interested (or studying :-) the topic.

0
None
NachoMahma

10 years ago

. Tres kewl. . Both links work for me.

0
None
Rock Soldier

10 years ago

That is awesome! I have to tell my science teacher that.