More images of exoplanet show it orbiting its star

By Phil Plait | March 3, 2011 12:34 pm

Although well over 500 planets orbiting other stars are known to exist — and we know of many, many more awaiting confirmation — direct images of the planets are very rare. That’s because stars are billions of times brighter than planets, and the planets tend to huddle so closely to their star that their feeble light gets overwhelmed.

But it’s possible, and we have several images of such exoplanets. One of them is Beta Pictoris b, a super-Jupiter orbiting the star Beta Pic (as we in the know call it) about as far out as Saturn orbits the Sun. Its existence was confirmed in 2009, but it was also seen in earlier images in 2003 and 2008. The motion of the planet from one side of the star was obvious, and now observations from March 2010 again show it has moved as it orbits the star:

Pretty cool! These infrared images from the Very Large Telescope all have the starlight removed to show the faint planet (the faint rings and other blobs are optical effects and can be ignored). The upper left picture is from 2003; the upper right from 2009 with the planet’s position in 2003 labeled; and the bottom is the new image from 2010 with both previous positions marked. The orbit of Saturn (tilted to the same inclination as Beta Pic b) is shown for comparison. You can see the planet moved a wee bit between 2009 and 2010, just as predicted.

Besides helping nail down the planet’s orbit, the new observations allow astronomers to find that the mass of the planet is between 7 and 11 times that of Jupiter, and the temperature probably between 1100 and 1700°C (2000 to 3100° F). The star is more massive and hotter than the Sun, which is one reason why the planet can be so hot even that far out.

The other is that system is actually very young as well, being only about 12 million years old — compare that to our solar system, which is 4.6 billion years old! So the planet is still glowing with the leftover heat of its formation. In fact, the temperature measurements are critical, because scientists who study the way planets form predict how hot planets will be at different times in their life… and this planet is hotter than some computer models predict. Observations like this help theoretical astronomers figure out which models are correct, and which still need work.

But even aside from all that, this image is still pretty amazing. That planet is 630 trillion km (390 trillion miles) from Earth — that’s 630,000,000,000,000 kilometers! And there it is.

Think about that. In 1992 we didn’t even know if planets outside our solar system existed. Then we discovered some weird ones, and just three years later the first planet orbiting a sun-like star was found. And now, just 16 years later, we’ve directly seen more than a half dozen of them!

Incredible.

Image credit: M. Bonnefoy et al., published in Astronomy & Astrophysics, 2011, vol. 528, L15


Below is a gallery of all the exoplanets we’ve seen so far. I have several shots of Beta Pic b in there, so take a look at these and marvel at what we humans can do!

[Click the picture or use the slider to see the next image.]

exoplanet_betapic3
exoplanet_1rxs1609b
exoplanet_2m1207b
exoplanet_betapicb1
exoplanet_betapicb2
exoplanet_fomalhautb
exoplanet_fomalhautb2
exoplanet_gliese581c_art
exoplanet_hr8799
exoplanet_hr8799b_art
exoplanet_hr8799cspec
hr8799e
hst_hr8799_1998
lkca-15-b_andstar
vlt_betapicb_2011


Related posts:

Astronomers see exoplanet orbiting its parent star!
Get ready to see lots more exoplanet images soon
Kepler finds a mini solar system!
Exoplanet found… from another galaxy!

CATEGORIZED UNDER: Astronomy, Cool stuff, Pretty pictures

Comments (37)

  1. It’s like a planetary baby picture. :) It’s so cute!

  2. Grizzly

    Wow. I love pics of Beta Pic.

  3. Gareth

    Hah. Cool. In my boredom, I decided to see if I could calculate the mass of Beta Pictoris based on those images – estimating the orbital radius at 20 AU, and the period at 12 years. Got a mass of 3.6E+27 kg. Then I checked Wikipedia, and it says Beta Pictoris is 1.75 times the mass of the sun. Dividing 3.6E+27 by 1.75 gives 2.05E+27 kg, which is very approximately the mass of the sun (a little bit more, but then I did just guess the numbers based on one picture!)

    It may be 13 years since I finished my astrophysics degree and I’ve not used it since, but I’ve still got it… ;o)

  4. Gareth

    EDIT from above:

    Maybe I haven’t still got it completely. I’ve missed a factor of 1000 off somewhere in there. Should be 3.6E+30 kg, not E+27! Ooops.

  5. Trebuchet

    I love/hate the galleries. Love them because they’re always pretty cool. And hate them because they’re completely unusable when I’m stuck in the land of dial-up, as I am about half the time, including right now.

  6. John

    That sucker must really be moving to go from one end of its orbit to another in 6 years, when it takes Saturn almost 15 years to do the same. Or have I misunderstood something?

  7. NoOneOfConsequence

    Does that mean it orbits its star once every 14 Earth years? That seems REALLY fast for something as far out as Saturn.

  8. JohnW

    It’s very considerate of Beta Pic to be star-shaped like that.

  9. BJN

    I’m not seeing six months of movement in the third picture, assuming that between 2003 and 2009 the travel is a little less than half an orbit. Six months would be about 15 degrees, no?

  10. Combat Astronomer

    I don’t presume to know a whole lot about orbital mechanics. But, it seems a bit odd to me that a planet that presumably orbits slighter closer to it’s star than Saturn ours, yet it only has approx. a 12 year orbital period. Wouldn’t that mean there were some extreme masses involved? Anyone with some insight would be greatly appreciated!

  11. Jamie

    Combat Astronomyer,

    Did you read Phil’s post at all?
    “Besides helping nail down the planet’s orbit, the new observations allow astronomers to find that the mass of the planet is between 7 and 11 times that of Jupiter,”

  12. Tom (H. Type)

    Not being an astrophysicist, I got to ask, does a Sun’s mass stay constant over time?

    Doesn’t it loose a significant amount of mass from converting mass to energy, therefore making it difficult for large fast moving objects to be very far out from the sun? Relatively speaking.

  13. chris j.

    Combat Astronomer, a planet’s orbital period is dependent on its distance from its star, the star’s mass, and the planet’s mass, per Kepler’s 3d law. increasing the masses will reduce the orbital period. i’d give you the actual calculations, which i attempted on the back of a napkin (really!), but i came up with about 4-6 years so i must be doing something wrong.

  14. Tom (12): Actually, I calculated that a while back on my original BA site. Turns out the mass loss from solar wind is a tiny fraction of the loss due to nuclear fusion in the Sun’s core, and even that isn’t much compared to the mass of the whole star.

  15. Messier Tidy Upper

    Superluminous news! :-D 8)

    For more on Beta Pictoris see : http://stars.astro.illinois.edu/sow/betapic.html

    with a finder chart here : http://stars.astro.illinois.edu/sow/pup-t.html

    Thanks to Kaler’s stars website. Love this news! :-D

  16. Gareth

    Combat Astronomer: as I say in my post, a 12 year period at roughly 20AU is consistent with a stellar mass of about 3.6E+30 kg, which is about what Wiki claims is Beta Pic’s mass: http://en.wikipedia.org/wiki/Beta_Pictoris )

    BTW – in case anyone’s interested (and hasn’t already worked it out), my factor of 1000 mistake was due to me converting the AU into kilometres rather than metres! Schoolboy error… :o$

  17. Gareth

    I’m having a really bad evening, aren’t I? Saturn is at approximately 10AU, not 20AU!

    Perhaps I should just go back to school… :oD

  18. Gareth

    Ok, I’m feeling a bit stupid now, of course, but I thought I’d give it another go from a different angle.

    If the orbital radius is slightly less than Saturn’s orbital radius, i.e. at around 8 or 9 AU, and the mass of Beta Pic is around 3.5E+30kg, I get an orbital period of around 20 years.

    Phew.

    If there’s one thing I’ve learned tonight it’s that when I get bored, I need to find something other than calculations of orbital mechanics to occupy my time… (BTW, yes I was this bad while doing the aforementioned astrophysics degree too…)

  19. Tom (H. Type)

    Thanks Phil, that explains it.
    You’ve been at this for a while…same old questions, you have ready made explanations.

    …and no, I’m not a “Young Earther”. It’s just the scale problem again. 4.4 million kg per second over billions of years seems that there would be nothing left, until you put the total mass into perspective.

    Suns are Huge…really Huge! That kind of mass makes a big divot in the old Space/time fabric.

  20. Messier Tidy Upper

    @17. Gareth Says:

    I’m having a really bad evening, aren’t I? Saturn is at approximately 10AU, not 20AU! Perhaps I should just go back to school…

    Oh well, we all have our good days and our bad

  21. Robert

    @Tom:

    The solar wind is pretty insignificant in terms of the amount of material lost, like Phil said. However, after the sun evolves a bit more, when it becomes a red giant, it will probably have a fairly significant wind. We see other giant stars that lose mass at rates of a millionth of a solar mass per year, which may not sound like much, but is a heck of a lot of stuff, particularly when you realize that at that rate the star would be gone in only ~1 million years.

  22. Messier Tidy Upper

    CONTINUED from #20 :
    _________________________

    … ones, that’s understood & okay.

    We’re all human and as such fallible. (Like how I’ve messed up this comment, *sigh*.)

    So no worries. ;-)

    (Some of us are just more fallible than others but anyhow.)

  23. Tobin Dax

    This just evokes a visceral response from me. It is so cool that we can actually pictures of an exoplanet. This post really made my day

    @ Gareth – You mean it’s possible to quit doing astrophysics for fun? Not that I’m sure if I want to. :)

  24. Messier Tidy Upper

    @21. Robert Says:

    @Tom : The solar wind is pretty insignificant in terms of the amount of material lost, like Phil said. However, after the sun evolves a bit more, when it becomes a red giant, it will probably have a fairly significant wind. We see other giant stars that lose mass at rates of a millionth of a solar mass per year, which may not sound like much, but is a heck of a lot of stuff, particularly when you realize that at that rate the star would be gone in only ~1 million years.

    We also see such red giants doing wnderful things like this :

    http://blogs.discovermagazine.com/badastronomy/2007/08/15/the-wonderful/

    Where Mira has left a comet-like tail of material light-years in length behind it!

    Also things like this :

    http://kencroswell.com/RHydraeBowShock.html

    Bowshock around the similar Mira star, R Hydrae.

    Plus its not just red giants that do these things as you’ll find from reading this old BA blog post :

    http://blogs.discovermagazine.com/badastronomy/2011/01/24/shocking-star-is-shocking-shocking-i-say/

    about Zeta Ophiuchi, an 09 type blue supergiant. :-)

    Seconding your comments on the Sun’s red giant solar wind increase too – the mass loss involved may save our planet – or at least some of it, the Earth’s crust will still be rendered molten and the atmosphere probably stripped away into space! ;-)

  25. Messier Tidy Upper

    Incidentally, if its okay to do this – hope it is & my apologies if not – I’m going to note that the current (April 2011) issue of Sky &Telescope magazine has a good article on stars that host planets incl. an explanation on why A type stars are good candidates for directly imaging any exoplanets that may orbit them. :-)

    As we’ve done here & for Fomalhaut and HR 8799 or “Gadolabove” as I call it!

    (No, I don’t work for the magazine or get any commission or anything like that! Just love reading it & thinking that others might too. ;-) )

  26. Messier Tidy Upper

    Other exoplanetary news of remarkable findings :

    http://www.newscientist.com/article/dn20160-two-planets-found-sharing-one-orbit.html%20

    Can’t remember if I’ve posted this here before or not. If so, sorry.

  27. QuietDesperation

    Hmm. OK.

    How much ya want for it?

  28. Combat Astronomer

    @Jamie – Yeah, I did read the post. I was inferring that I suspected that even that mass was too low. But, I DID overlook the mass of it’s star is greater than ours too. So that might help explain. So my question to you is, are you typically antagonistic when responding to questions?

    @ Gareth – Thank you for explaining! Yeah, I had a basic understanding of Keppler’s laws of gravitation and that is probably where the problem lied. Enough knowledge to wonder, not enough to say anything intelligent. lol

  29. Steveo

    Dibs on the Starbucks franchises!

  30. Movius

    I remember watching space documentaries as a child in the late 80s/early 90s. The picture of Beta Pictoris’ circumstellar disc would always be shown as the iconic “Maybe there are planets here” star. It is amazing to me that they are now directly imaging planets around the star.

  31. NoAstronomer

    @chris j

    “…a planet’s orbital period is dependent on its distance from its star, the star’s mass, and the planet’s mass, per Kepler’s 3d law.”

    Unless something has changed since I dropped out of my Astrophysics class 28 years ago*, a planet’s mass has no effect on it’s orbital period. That’s only going to depend on it’s distance from the star and the star’s mass.

    I’m just guessing but the authors of the paper probably determined the mass of Beta Pictoris b by using it’s apparent temperature and brightness to determine it’s size. Then assuming it is a gas giant with around the same density as Jupiter/Saturn you can work out an estimate for the mass.

    7-11 Jupiter masses is a fairly wide range.

    Mike

    * Kudos to Gareth for sticking with it.

  32. Bubba

    Gasp! FSM help us. We are not alone.

  33. NoAstronomer

    I’ll also note that the upper limit for the projected mass of Beta Pictoris b butts right up against the lower limits for a brown dwarf.

  34. Messier Tidy Upper

    @33. Bubba : Gasp! FSM help us. We are not alone.

    Almost certainly not – but it’ still too early to say we know that for sure. :-)

    Although the probability of there being life and even intelligent sentient life is exceedingly high (95% or more I’d guess) we still don’t know of any actual alien species or sentiences out there.

  35. mike burkhart

    OK now for the big question.Do any of these planets have life on them? Some might only have the chemical reaction ”soup” that will leed to life forms millons of years later,like on Earth billons of years ago.

  36. DigitalAxis

    Another reason Beta Pic b is easy to see, is that the star Beta Pic is only about 12 million years old. That 7-12 Jupiter Mass planet is still gravitationally contracting and producing energy.

    Also, at 12 Myr old, that planet there isn’t much older than the human species! (unless my anthropology is way off. Which it easily could be…)

    @31 NoAstronomer: Actually, the mass of the planet technically does count. The formula you remember is Mass*Period^2=semimajorAxis^3, where M is the TOTAL mass of the system in question (thus, it works for binary star systems too). It’s just that Beta Pic, at 1.75 Solar Masses, vastly outweighs Beta Pic b, at 0.007 – 0.012 Solar Masses; the answer for a 1.762 solar mass system is going to be basically identical.

NEW ON DISCOVER
OPEN
CITIZEN SCIENCE
ADVERTISEMENT

Discover's Newsletter

Sign up to get the latest science news delivered weekly right to your inbox!

ADVERTISEMENT

See More

ADVERTISEMENT
Collapse bottom bar
+

Login to your Account

X
E-mail address:
Password:
Remember me
Forgot your password?
No problem. Click here to have it e-mailed to you.

Not Registered Yet?

Register now for FREE. Registration only takes a few minutes to complete. Register now »