APOD: A Giant Planet for Beta Pic (2010 Jul 03)

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APOD: A Giant Planet for Beta Pic (2010 Jul 03)

Post by APOD Robot » Sat Jul 03, 2010 4:05 am

Image A Giant Planet for Beta Pic

Explanation: A mere 50 light-years away, young star Beta Pictoris became one of the most important stars in the sky in the early 1980s. Satellite and ground-based telescopic observations revealed the presence of a surrounding outer, dusty, debris disk and an inner clear zone about the size of our solar system -- strong evidence for the formation of planets. Infrared observations from European Southern Observatory telescopes subsequently detected a source in the clear zone, now confirmed as a giant planet orbiting Beta Pic. The confirmation comes as the planet is detected at two different positions in its orbit. Designated Beta Pictoris b, the giant planet must have formed rapidly as Beta Pic itself is only 8 to 20 million years old. With an orbital period estimated between 17 and 44 years, Beta Pictoris b could lie near the orbit of Saturn if found in our solar system, making it the closest planet to its parent star directly imaged ... so far.

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Re: APOD: A Giant Planet for Beta Pic (2010 Jul 03)

Post by Ann » Sat Jul 03, 2010 7:41 am

It's really fascinating to actually see a direct photo of a planet orbiting another star!

Me being a color freak and preferring the color blue over all other colors, I find it fascinating that this alien planet is actually orbiting a blue star. (Yes, yes, I know that astronomy officially defines Beta Pictoris as a white star since it is of spectral class A, but to me class A stars are blue. At least, they are blue in the same way that emission nebulae are red: they may not actually look that color, but they would if our eyes were only a bit more sensitive!)

Also, I find it interesting that planet-hunting astronomers preferentially scrutinize low-mass stars, stars with the same mass as the Sun or less. You get the impression - or at least I get the impression - that the low-mass stars are the ones that are most likely to have planets. And yet, the first planet directly imaged and photographed is orbiting a star which is about twice as massive as the Sun.

And yes, I know that the low-mass stars are so very much more common than the high-mass stars, but still...

Okay, don't tell me. It's about finding life-bearing planets, and planets orbiting hot short-lived stars don't qualify. Well, I got a kick out of Beta Pictoris b, all the same!

Ann
Last edited by Ann on Sat Jul 03, 2010 10:22 am, edited 1 time in total.
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Re: APOD: A Giant Planet for Beta Pic (2010 Jul 03)

Post by Ann » Sat Jul 03, 2010 10:13 am

Well, it appears I was wrong when I said that Beta Pictoris b was the first directly imaged planet orbiting another star. That honor apparently goes to Fomalhaut b:

Image

All right, but Fomalhaut is another blue star of spectral class A! So the first two directly imaged planets orbiting other stars are in orbit around two different class A stars, which are both about twice as massive as the Sun! What a coincidence!

Speaking about the importance of a star's spectral class and its likelihood to have planets, it is my impression, as I have said, that astronomers are very interested in low-mass stars, even stars which are a lot more lightweight than the Sun. Of course the real reason for this is almost certainly that astronomers are really looking for potentially life-bearing planets, and then conventional wisdom has it that planets orbiting high-mass stars won't do.

So what do the experts say? Why do we live on a planet orbiting a G2V star? Stars of spectral class G most certainly aren't rare in our galaxy, but they definitely arent typical, either. Compared with small cool stars of spectral class M, stars like our Sun are few indeed. In view of the fact that stars of class M are so very much more common than stars of class G like our Sun, isn't it strange that we orbit a star that is so, well, untypical?

The way I see it, there are two possible reasons why our living planet orbits a star of spectral class G. One possibility would be that life might be so commmon in our galaxy that most stars can be expected to have at least one life-bearing planet, and in that case it is sheer coincidence that our star is of untypical spectral class G. It also follows from that line of reasoning that if we manage to travel to a star of class M, we can expect to find a life-bearing planet in orbit around it.

The other possibility would be that life, at least complex life, is very very uncommon, and it only comes into existence where conditions are just right. If so, it is probably no coincidence that our Sun is of spectral class G, and it also follows from that reasoning that if we travel to a star of spectral class M, we probably won't find life on any of its potential planets.

A third possibility is that "the life-friendliness of the spectral class of a star" is a function of the age of the universe. Perhaps life is far more probable on a planet orbiting a class G star now than on a planet orbiting a class M star, now that the universe is about 14 billion years old. It could be that when the universe is twice as old, or five times as old, most G stars like our Sun will have burnt out and any life on their planets will have expired. The M dwarfs will remain essentially the same, however, and life will have time to keep trying to come into existence on planets orbiting these tiny stars. The likelihood of life existing on planets orbiting stars of class M may increase over time, while it will almost certainly decline over time for stars of class G.

Well, these things are certainly interesting, in any case!

Ann
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Re: APOD: A Giant Planet for Beta Pic (2010 Jul 03)

Post by orin stepanek » Sat Jul 03, 2010 12:55 pm

I find that it is interesting that so many exoplanets have been found already; over 400, and Kepler has candidates for 750 or so! http://www.planetary.org/exoplanets/list.php
http://upcoming.current.com/search?q=Ne ... Candidates
Orin

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Re: APOD: A Giant Planet for Beta Pic (2010 Jul 03)

Post by León » Sat Jul 03, 2010 1:40 pm

The image and the subject of today I call for the following considerations:
1 .- As the image comes from the planet's orbit be elliptical because it is closer to the star at one end than the other.

2 .- It seems that the travel speed, using the average estimate is similar to that of Saturn.

3.-Nothing but the presumption indicates that the planet may have formed from the debris and dust.

4.-That as a disk orbiting a far greater distance from the star.

It is my opinion that the stars after their birth will begin a transition and incorporating the waste found along the way, as today we can deduce by observing the trans-Neptunian planets of the solar system.

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Re: APOD: A Giant Planet for Beta Pic (2010 Jul 03)

Post by ChazNAustin » Sat Jul 03, 2010 1:58 pm

I guess this question is not that important given the short life of this class of star. BUT, if Beta Pictoris is 8.6 times as hot as the sun, then presumably 8.6 more times Beta Pic energy reaches Pic Beta than reaches Saturn. Does that mean the planet gets as much energy as an object in Sol's asteroid belt receives? Not enough energy for liquid water I guess, though a planet that large and young may have a large amount of internal heat. Life wouldn't have time to evolve very far I guess. What is the average lifetime of this star class?

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Re: APOD: A Giant Planet for Beta Pic (2010 Jul 03)

Post by Henning Makholm » Sat Jul 03, 2010 2:25 pm

ChazNAustin wrote:I guess this question is not that important given the short life of this class of star. BUT, if Beta Pictoris is 8.6 times as hot as the sun,
Irrelevant correction: In terms of temperature, it is 1.43 times as hot as the sun. According to the Stefan-Boltzmann law, that makes each square meter of its surface radiate 4.2 times as much energy as a square meter of the sun. But the star itself is also a bit larger, so the total energy radiated is 8.6 times the sun's output.
Does that mean the planet gets as much energy as an object in Sol's asteroid belt receives?
Yes, though rather on the outer side, around 4 AU from the sun. That's only 1/16 of the flux that hits Earth.
Not enough energy for liquid water I guess, though a planet that large and young may have a large amount of internal heat.
It could have an Europa-like moon, though.
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Re: APOD: A Giant Planet for Beta Pic (2010 Jul 03)

Post by jman » Sat Jul 03, 2010 5:34 pm

Why doesn't the debris appear as a full disk?

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Re: APOD: A Giant Planet for Beta Pic (2010 Jul 03)

Post by Ray-Optics » Sat Jul 03, 2010 6:02 pm

Ann notices that astronomers have concentrated on low-mass stars, but this one has a higher mass. That's because the first exoplanet searches were limited to Doppler shifts of the star, and the smaller the star (and larger and closer the planet) the greater the shift. So the ones showing up first were giants up close to small stars, because they showed the greatest effects. What makes this notable is that it's a direct image of the planet. And while the planet's reflected light drops with the square of the distance to the star, the greater separation allows for much better masking of the star's brilliance, and a brighter star means a brighter planet.

Leon conjectures that the planet's orbit is elliptical because it's farther at "one end" than the other. But we don't know those are the *ends* of the orbit as projected towards Earth; just two different times. That's why the orbital period is uncertain. We'd have to take several images separated in time and see how the lateral velocity changes to come up with a good orbit.

Jman asks why the dust doesn't appear as a full disk. Here's an experiment: Cut a donut crosswise in several parallel sections The cut that just intersects the inside ring of the donut is the longest cut - it would appear brightest. The cut bisecting the donut is much shorter.

Hope this helps.

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Re: APOD: A Giant Planet for Beta Pic (2010 Jul 03)

Post by León » Sat Jul 03, 2010 7:32 pm

Yes Ray-Optics same thought, but I guessed from the picture that emerges from http://www.eso.org/public/news/eso1024/ in which the planet is observed in the antipodes. Si Ray-Optics lo mismo pensé, pero la deduje a partir de la imagen que surge de http://www.eso.org/public/news/eso1024/ en el que el planeta se observa en la antípodas

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Re: APOD: A Giant Planet for Beta Pic (2010 Jul 03)

Post by Wolf kotenberg » Sun Jul 04, 2010 2:09 am

fantastic revelation. I have a fascination with what is going to happen next at APOD. Ya'll doing a great service to the community and from a humble user
pass the ice cold one, please

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Re: APOD: A Giant Planet for Beta Pic (2010 Jul 03)

Post by Beyond » Fri Jul 16, 2010 4:35 pm

Here ya go. :b: :b: Have two - they're FREE!!
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Re: APOD: A Giant Planet for Beta Pic (2010 Jul 03)

Post by rstevenson » Fri Jul 16, 2010 7:15 pm

TGIF!
Photo on 2010-07-16 at 16.12.jpg
Rob

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