VLT Detects First Superstorm on HD209458b

View previous topic View next topic Go down

VLT Detects First Superstorm on HD209458b

Post by Stalker on 23rd June 2010, 3:17 pm


_________________
avatar
Stalker
Jovian
Jovian

Number of posts : 530
Age : 26
Location : Paris, France
Registration date : 2008-06-16

View user profile http://exoplanetes.wetpaint.com/

Back to top Go down

Re: VLT Detects First Superstorm on HD209458b

Post by Lazarus on 23rd June 2010, 4:00 pm

Now that is impressive. Measurement of the orbital velocity of the planet, allowing direct determination of the mass of the star. I guess this is the first double-lined eclipsing binary where one component is a planet.

(Incidentally it is nice to see that ESO makes the papers available with the press release.)
avatar
Lazarus
dG star
dG star

Number of posts : 2872
Registration date : 2008-06-12

View user profile

Back to top Go down

Re: VLT Detects First Superstorm on HD209458b

Post by Sirius_Alpha on 23rd June 2010, 4:13 pm

Wow that is remarkable.

The mass of the star is quoted as 1.00 0.22 Msol But the planet mass has a much lower error, 0.64 0.09 MJ. Why is the planet's mass much more constrained than the stars?

Edit: I wonder if they could determine the wind speed as a function of latitude by carefully watching the planet's atmospheric absorption lines red shift during transit ingress and egress. It'd have to be some pretty darned fast measurements as they'd only have a few minutes to do it, but it might allow us to map zones and belts on the planet.

Edit2: Just realised... this suffers from inclination degeneracy effects too. Not knowing the planetary rotation axis, is this only a lower limit to the wind speed?

_________________
Caps Lock: Cruise control for 'Cool'!
avatar
Sirius_Alpha
Admin
Admin

Number of posts : 3514
Location : Earth
Registration date : 2008-04-06

View user profile http://solar-flux.forumandco.com/

Back to top Go down

Re: VLT Detects First Superstorm on HD209458b

Post by exoplanet on 24th June 2010, 6:38 am

This is indeed awesome.

I guess this is the first double-lined eclipsing binary where one component is a planet.

Nicely put Lazarus Smile

I just think that the public release should be more precise. After all they did not detect a "Storm" but apparently a super-rotating wind.

exoplanet
Planetesimal
Planetesimal

Number of posts : 124
Location : here
Registration date : 2008-06-16

View user profile

Back to top Go down

Re: VLT Detects First Superstorm on HD209458b

Post by Lazarus on 24th June 2010, 6:13 pm

Sirius_Alpha wrote:The mass of the star is quoted as 1.00 0.22 Msol But the planet mass has a much lower error, 0.64 0.09 MJ. Why is the planet's mass much more constrained than the stars?
Good question.

From the equations of motion it is possible to write the expressions for star and planet mass as follows:

m1 = (P K23 (1 + K1 / K2)2) / (2π G sin3 i)

swap index 1 and 2 to get planet mass.

Error bars are given for K1, K2 and i, so the error on the mass can be expressed:

σm2 = ((∂m / ∂K1) σK₁)2 + ((∂m / ∂K2) σK₂)2 + ((∂m / ∂i) σi)2

Working through that does give the uncertainties quoted in the paper, so that all checks out.

Uncertainty basically comes down to which of K23(1 + K1/K2)2 (in the expression for star mass) and K13(1 + K2/K1)2 (in the expression for planet mass) has greater uncertainty. Very handwavey way of looking at it, K2 has significantly higher uncertainty than K1, and in the expression for star mass the highest order term is in K23 as opposed to K22 in the expression for planet mass.
avatar
Lazarus
dG star
dG star

Number of posts : 2872
Registration date : 2008-06-12

View user profile

Back to top Go down

Re: VLT Detects First Superstorm on HD209458b

Post by Sirius_Alpha on 25th June 2010, 1:27 pm

Ahhh alright. That makes sense. Thanks.

_________________
Caps Lock: Cruise control for 'Cool'!
avatar
Sirius_Alpha
Admin
Admin

Number of posts : 3514
Location : Earth
Registration date : 2008-04-06

View user profile http://solar-flux.forumandco.com/

Back to top Go down

Re: VLT Detects First Superstorm on HD209458b

Post by Borislav on 25th July 2010, 3:53 am


Borislav
Jovian
Jovian

Number of posts : 561
Registration date : 2008-11-12

View user profile

Back to top Go down

Re: VLT Detects First Superstorm on HD209458b

Post by Lazarus on 3rd February 2011, 6:38 pm

avatar
Lazarus
dG star
dG star

Number of posts : 2872
Registration date : 2008-06-12

View user profile

Back to top Go down

Re: VLT Detects First Superstorm on HD209458b

Post by Sponsored content


Sponsored content


Back to top Go down

View previous topic View next topic Back to top


 
Permissions in this forum:
You cannot reply to topics in this forum