Register to reply

Gliese 581 d

by DaveC426913
Tags: gliese
Share this thread:
DaveC426913
#1
May12-07, 12:14 AM
DaveC426913's Avatar
P: 15,319
I'm trying to find a reasonable estimate of the density of Gliese 581 d (not c).

According to Wiki, d is ~1.96x the radius of Earth and ~7.7x the mass. This makes for a density very near Earth's (2^3=8). Yet they then go on to list its density as 730kg/m^3 or 0.73g/cm^3 - almost as rarefied as Saturn.

Can anyone point me at some more authoritative numbers? I know we're only estimating, but clearly one of those three numbers r,d or m is spurious.
Phys.Org News Partner Astronomy news on Phys.org
Transiting exoplanet with longest known year
Mysterious dance of dwarfs may force a cosmic rethink
Study shows oceans vital for possibility for alien life
Brad_Ad23
#2
May12-07, 11:51 PM
P: 499
Quote Quote by DaveC426913 View Post
I'm trying to find a reasonable estimate of the density of Gliese 581 d (not c).

According to Wiki, d is ~1.96x the radius of Earth and ~7.7x the mass. This makes for a density very near Earth's (2^3=8). Yet they then go on to list its density as 730kg/m^3 or 0.73g/cm^3 - almost as rarefied as Saturn.

Can anyone point me at some more authoritative numbers? I know we're only estimating, but clearly one of those three numbers r,d or m is spurious.
They all could be right due to a few things. When you calculate the density via M/V you are basically assuming a constant density throughout the entire planet, but usually that is a decent for a very rough approximation.

I notice the article you mention is lacking citations on both the radius and the density, so it is possible those are flawed as well.


Register to reply

Related Discussions
Gliese 581c/d and their Red Sun? Astronomy & Astrophysics 4
Habitability of Gliese 581 D Astronomy & Astrophysics 0