Celestia Forums

http://news.bbc.co.uk/2/hi/science/nature/3599496.stm

...though at 14 times the mass of the Earth and with an orbital period of only 9.5 days, it's not really that "earth-like"... for comparison, Uranus and Neptune are 14 and 17 times the mass of the Earth, but it seems unlikely that this could be an icy giant that close to the star, particularly given that there's as bigger jovian further out. Could it be a "hydrogen giant" (a la Saturn or Jupiter) that's lost most of its mass? I'm a little skeptical about it being a terrestrial world, unless it's one of these massive water worlds (but then would the water survive that close to the star?)

Does anyone have more info on this? Or any ideas?

If you want to take a look at it in Celestia, here's a preliminary definition. I've designated it "a" meantime, in emulation of the practice followed when a new inner planet was discovered around PSR 1257+12. But I doubt if such an odd approach will catch on ... I'll be interested to see what designation this planet attracts.

Grant

Interesting planet; using Mike Wong's planetary parameter calculator, I make the surface gravity 2.4 gee and the escape velocity 26.9 km/s.

(I always like to use a calculator if available- don'y know if it is accurate tho')

For some reason I think I'll make it brownish in colour, expecting a lot of dirty organic compounds.

ooh- do you think it is tidally locked?

it sounds somewhat similar to my imaginary planet Sisyphos, a Chthonian planet, in that case- although that world is closer still...

Dang, I figured out all this stuff about the planet then found that there was a paper about it here that had totally different luminosity values for the star.

I don't get that. Solstation claims that Mu Arae is an old high metallicity main sequence star about to become a subgiant, with luminosity 1.7 Sols - but the paper linked in the URL above claims that the star's absolute magnitude is 4.2, which if I figured it out correctly (according to the text box at the bottom of this page) translates to a luminosity of only 0.56 Sols?!

That makes a huge difference to the temperature of the planet. If it was 1.7 Sols it wouldn't be able to hold onto hydrogen or helium at all and would have been rather more interesting. If it is 0.56 Sols then at best it can hold onto both gases, and at worst it can only hold onto helium.

Is the Santos et al paper likely to be more accurate?!

An absolute magnitude of 4.2 implies that Mu Ara is brighter than the Sun (which has absolute bolometric magnitude of 4.75). It's brighter by a factor of 2.512^(4.75-4.2) = 1.7.
QED.

I think you must have used a negative exponent.

Grant

...at last, something to use the "venuslike.jpg" texture on, and I was just wondering why it was kept around...

EDIT - SolStation is apparently using the designation "d", however I'm not sure if that's official yet.

As far as I'm aware, the letters are assigned in order of discovery, not distance from the star. So "d" should be proper.

Not my favorite designation scheme, but oh well....

...John...

chaos syndrome wrote:...at last, something to use the "venuslike.jpg" texture on, and I was just wondering why it was kept around...

EDIT - SolStation is apparently using the designation "d", however I'm not sure if that's official yet.

Dollan wrote:As far as I'm aware, the letters are assigned in order of discovery, not distance from the star. So "d" should be proper.

Seems reasonable. Unfortunately the discoverers of PSR 1257+12 a thought differently. Sigh.

Grant

That's true. I'm trying to remember, but I think there was a lot of shuffling around of the planetary layout in the 1257 system before they finally settled. Or maybe I'm thinking of the other pulsar system (I forget the name now) which was eventually disproven.

My only gripe with this system is that it is easy to confuse the planets with other solar companions. Granted, in the written word a planet designation "b", for example, is hard to mix up with the upper case solar designation "B". But sometimes the eye glosses over that distinction.

Anyway, I kind of wish that they would come up with some proper names for these new planets. Maybe follow the same guidlines as are used with asteroids, but with just a bit tighter regulation by the IAU (no Mr. Spock planets, in other words!)

...John...

granthutchison wrote: Seems reasonable. Unfortunately the discoverers of PSR 1257+12 a thought differently. Sigh.

Grant

Guys,

I have Celestia 1.3.1 (Mac OSX), and I don't have those textures you're talking about. Where can I get them ?

Venuslike.jpg ???

I've got 'venuslike', but I haven't got 'extrasolar-lok';

anyway, I've made my own, a highly modified version of one of the textures in the Mostly Harmless planet generator;
and I have called my version Semele, after the mythical woman who was burned by getting too close to Zeus...

eburacum45 wrote:I've got 'venuslike', but I haven't got 'extrasolar-lok'

Extrasolar-lok.jpg went out with 1.3.2 final - it's just a grey mask that indicates we have no knowledge of the surface appearance of the planet when the user selects "limit of knowledge" view.

Grant

Cham wrote:Guys,

I have Celestia 1.3.1 (Mac OSX), and I don't have those textures you're talking about. Where can I get them ?

Venuslike.jpg ???

venuslike.jpg is still in the CVS repository, whether its part of the current versions I don't know.

Try checking Celestia\Textures\medres.

extrasolar-lok is also in the CVS repository.

Venuslike.jpg certainly distributed with both 1.3.1 and 1.3.2, Windows version. It would be a bit annoying if you don't have it in the Mac distribution, since I was considering using it as the default for these close-in objects of "intermediate" mass.

Grant

Oups !

I'm sorry, I had venuslike.jpg.

Here's my suggestion for this new planet. I think it may be a bit (?) more accurate for a planet that close to its star, and it's much nicer to look at, in Celestia :


"a" "HD 160691" # Mu ara
{
Texture "venuslike.jpg" # Massive atmosphere (?)
#SpecularColor [1 0.6 0.6]
SpecularColor [0.7 0.3 0.3]
SpecularPower 10.0

Mass 14
Radius 15400 # Earth-like density (?)

EllipticalOrbit {

Period 0.0260
SemiMajorAxis 0.09
}

Atmosphere {
Height 1000
Lower [ 0.4 0.4 0.5 ]
Upper [ 0.1 0.1 0.15 ]
Sky [ 0.8 0.8 0.5 ]
Sunset [ 1.0 0.6 0.2 ]
}
}


What do you think ?

http://www.obspm.fr/encycl/HD160691.html


HD 160691 b

HD 160691 c

HD 160691 d NEW!!!!

From the ESO Press Release the estimate given is ~1/10th the mass of the planet as atmosphere.

That would be ~1.4 Earth masses atmosphere, which would be pretty thick I would think.

Cham - it might be more "realistic" to make the venuslike texture the cloud layer, and have asteroid.jpg as the surface - not sure about this though...

So, if you have that much atmosphere, wonder what the prospects for oceans of liquid metals would be?

symaski62 wrote:http://www.obspm.fr/encycl/HD160691.html


HD 160691 b

HD 160691 c

HD 160691 d NEW!!!!

The "d" planet quoted there is the same as the "a" planet we are discussing. So there are three planets orbiting the HD 160691 star : a, b and c, OR b, c and d.

The Epoch command line is laking for our new "a" (or "d") planet. Any idea ?