Planets in ALF Cen officially real

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Planets in ALF Cen officially real

Post #1by PlutonianEmpire » 17.10.2012, 00:40

http://www.eso.org/public/news/eso1241/

European astronomers have discovered a planet with about the mass of the Earth orbiting a star in the Alpha Centauri system — the nearest to Earth. It is also the lightest exoplanet ever discovered around a star like the Sun. The planet was detected using the HARPS instrument on the 3.6-metre telescope at ESO’s La Silla Observatory in Chile. The results will appear online in the journal Nature on 17 October 2012.

There was an embargo, but someone broke it, so they had to say something.
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Re: Planets in ALF Cen officially real

Post #2by abramson » 17.10.2012, 01:12

This is so frakking cool. We must go!

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Re: Planets in ALF Cen officially real

Post #3by wieczor » 17.10.2012, 05:08

Good new but do not forget the suntan oil ! :lol:
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Re: Planets in ALF Cen officially real

Post #4by kristoffer » 17.10.2012, 14:53

I were so happy when I saw this news :)
I was almost going to jump and start dancing :wink:

Too bad the planet is very hot for life, but I hope they will find more planets in Alpha Centauri B

Is there maybe, existing a world like Pandora in Avatar there?
Who knows
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Re: Planets in ALF Cen officially real

Post #5by Hungry4info » 17.10.2012, 16:06

kristoffer wrote:Is there maybe, existing a world like Pandora in Avatar there?

No. RV data has ruled out giant planets around Alpha Centauri A and B. If any (more) planets exist around either star, they are super-Earths at most.
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Re: Planets in ALF Cen officially real

Post #6by granthutchison » 17.10.2012, 19:11

I've added Alf Cen B b to extrasolar.ssc on the SVN tree:
http://celestia.svn.sourceforge.net/vie ... c?view=log

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Re: Planets in ALF Cen officially real

Post #7by t00fri » 17.10.2012, 20:57

Just landed on the newly discovered planet b of Alf_CEN_B using the extrasolar.ssc file that Grant has committed to SVN about 2 hours ago.

With rising alf_CEN_B it looks like so in celestia.Sci (assuming there is no atmosphere):

[Click on image by all means!]
alf_cen_B_b.jpg


Here is a somewhat different perspective with alf_CEN_A in the background left of alf_CEN_B.

[Click on image by all means!]
alf_cen_B_b2.jpg


Finally, here is a scene with both alf_CEN stars visible and the new planet being marked near the bottom right:

[Click on image by all means!]
alf_cen_B_b3.jpg


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Re: Planets in ALF Cen officially real

Post #8by PlutonianEmpire » 17.10.2012, 23:33

granthutchison wrote:I've added Alf Cen B b to extrasolar.ssc on the SVN tree:
http://celestia.svn.sourceforge.net/vie ... c?view=log

Grant
That has to be a record, right? ;)

This is probably the earliest I've seen a new planet added to it after its discovery. :lol:
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Re: Planets in ALF Cen officially real

Post #9by granthutchison » 17.10.2012, 23:44

PlutonianEmpire wrote:That has to be a record, right? ;)

This is probably the earliest I've seen a new planet added to it after its discovery. :lol:
There have been a few quick updates over the years. :)
I generally add new systems to my local files pretty promptly, if only to prevent a backlog of work building up. But I tend to commit the changes to SVN more occasionally, unless I see an update I know will be generating a lot of interest - like this one.

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Re: Planets in ALF Cen officially real

Post #10by PlutonianEmpire » 17.10.2012, 23:48

granthutchison wrote:
PlutonianEmpire wrote:That has to be a record, right? ;)

This is probably the earliest I've seen a new planet added to it after its discovery. :lol:
There have been a few quick updates over the years. :)
I generally add new systems to my local files pretty promptly, if only to prevent a backlog of work building up. But I tend to commit the changes to SVN more occasionally, unless I see an update I know will be generating a lot of interest - like this one.

Grant
Ah, makes sense then. Cool. :)
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Re: Planets in ALF Cen officially real

Post #11by wieczor » 18.10.2012, 04:51

Do not forget that the star is of type K so it must be orange and not white as above.
In addition, the planet is very close to its surface must be magmatic in part ...
alfcenbb.jpg
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Re: Planets in ALF Cen officially real

Post #12by PlutonianEmpire » 18.10.2012, 05:28

wieczor wrote:Do not forget that the star is of type K so it must be orange and not white as above.
In addition, the planet is very close to its surface must be magmatic in part ...
alfcenbb.jpg
Ummmm.... No. :P

Correct me if I'm wrong, but...

https://en.wikipedia.org/wiki/Thermal_radiation

Specifically, this: https://en.wikipedia.org/wiki/Thermal_r ... l_radiator

480 c = 753.15 k = faint red glow
580 c = 853.15 k = dark red
730 c = 1003.15 k = bright red, slightly orange
930 c = 1203.15 k = bright orange
1100 c = 1373.15 k = pale yellowish orange
1300 c = 1573.15 k = yellowish white
> 1400 c = 1673.15 k = white (yellowish if seen from a distance through atmosphere)

(The Wiki article doesn't list the kelvins, I used a converter to find the numbers).

All stars are hotter than 2000 k, IIRC. The only light-emitting space objects even remotely capable of showing heat-related color to the naked human eye, at least on just the planetary and stellar scales, are brown dwarves, based on what I know of temperature/spectral type association.

Hope this helps. :)
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Re: Planets in ALF Cen officially real

Post #13by wieczor » 18.10.2012, 05:44

Everything is in the title: "Subjective color to the eye of a black body radiator thermal"
Unless I am mistaken, it should not be confused with the plasma of a stellar body ...

What is therefore the diagram H.R.?
http://en.wikipedia.org/wiki/Hertzsprung%E2%80%93Russell_diagram
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Re: Planets in ALF Cen officially real

Post #14by granthutchison » 18.10.2012, 08:23

Alf Cen B is hotter than the filament of an incandescent light bulb, and has a pretty continuous visual spectrum (no deep dark gaps). It would therefore look white (just as the red-dwarf-temperature light bulb filament looks white) when close enough to display a disc.
The only time it would appear orange would be if there were a hotter, comparably bright source also visible (as daylight looks blue if you're sitting under incandescent light, and incandescent light looks yellow if you look in from daylight).
It's a trick of visual physiology that any very roughly continuous, very roughly flat visual spectrum will become your local "white point" if it's your main source of illumination. Stars hotter than cool red dwarfs do a pretty good job of approximating black bodies and spanning the visual spectrum, so they fall into that category of illuminants that will appear white if they're the main source of illumination.
Celestia doesn't deal with such physiological subtleties, but it does offer a variety of different ways of displaying stars, some of which are more realistic than others under some circumstances.
So HR diagrams are generally colour-coded, rather than realistically coloured.

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Re: Planets in ALF Cen officially real

Post #15by t00fri » 18.10.2012, 09:58

bdfd wrote:Do not forget that the star is of type K so it must be orange and not white as above.

How about learning some physics (and visual physiology) before criticizing a professional (astro) physicist...I mean understanding NOT merely clicking webpages.

I have little to add to Grant's explanations, of course.

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Re: Planets in ALF Cen officially real

Post #16by Hungry4info » 18.10.2012, 12:09

wieczor wrote:Do not forget that the star is of type K so it must be orange

Next time the sun is up, go out and look at it and note it's colour. I know it's bright but it'll be a good science lesson. Is it yellow, as you would seem to expect for a G-type star?
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Re: Planets in ALF Cen officially real

Post #17by granthutchison » 18.10.2012, 15:13

Hungry4info wrote:
wieczor wrote:Do not forget that the star is of type K so it must be orange

Next time the sun is up, go out and look at it and note it's colour. I know it's bright but it'll be a good science lesson. Is it yellow, as you would seem to expect for a G-type star?
Interestingly, a lot of people will assure you that the sun does look yellow, even at noon. (There was once a very, very long thread about this over on the old BAUT forum.)
To some extent this is what you might expect when you glance at an oversaturated light source against a blue "background" - the complementary colour appears. And certainly people who look at the solar disc through the (more-or-less) neutral filter of clouds will generally report it to be white when they look at it against a neutral grey "background".
But I think there's also a psychological aspect to this - from childhood, we're exposed to cartoons and drawings of a yellow sun in a blue sky. Squinting and glancing at something that's too bright to examine closely, we can easily see just what we expect to see.

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Re: Planets in ALF Cen officially real

Post #18by Hungry4info » 18.10.2012, 15:47

That's a very legitimate argument, so let's look at light bulbs instead. (I'm sure this was mentioned on the BAUT forum as well)
A 2700 K (dM star temp) light bulb looks yellowish.
A 3500 K (still dM star temp) light bulb looks white.

To the human eye, I suspect that stars up close will probably appear white for all but the coldest stars. At least until you get into the B- and O-type.
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Re: Planets in ALF Cen officially real

Post #19by t00fri » 21.10.2012, 13:36

Here is another ghostly scene with ? CEN B, planet b, the Milkyway below and towards the top LMC and SMC. No doubt that it's pretty hot on planet b...

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[Click on image by all means!]
alf_cen_B_b4.jpg
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Re: Planets in ALF Cen officially real

Post #20by buggs_moran » 12.11.2012, 22:35

It has been a long time since I have done anything with Celestia. Life has a habit of interrupting fun. Anyway, I am confused about the generation of planets in a multiple star system in an ssc, specifically in the Alf Cen B case.

When an extrasolar planet is added, which star naming designation do you have to use HIP, HD, etc. after the planet?

I always thought you could use any of the names listed.

In the ssc file you have "planet name" "star designation"

I notice that Grant uses a Draper number in the ssc, but in the starnames.dat and nearstars.stc the Hipparchos designation is used. Where is the HD number defined for Alf Cen B?

"b" "HD 128621" # Alf Cen B


I am trying to create a temporary planet in orbit around a 40 Eri A. 40 Eri A is orbiting around barycenter which has the HD and HIP designation (HD 26965, HIP 19849). 40 Eri A should have those designations, not the barycenter I think. 40 Eri B has yet another HD designation. I've created the planet fine around the barycenter, but that's not what I am trying to do. I was showing one of my students how a habitable zone could exist in a more compact trinary system than the Alpha Cen B system. He asked me what it would look like. So far, no go...

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