Hubble smelt who dealt it

By Phil Plait | March 19, 2008 2:30 pm

Scientists have used Hubble to detect methane in the atmosphere of a planet orbiting another star for the first time and to confirm the existence of water vapor there as well.

This is not an easy thing to do! The planet is so close to its star that they can’t be separated in an image, and the star totally overwhelms the light from the planet. However, when the planet is between the star and us (think of it as a tiny and very distant eclipse) the starlight passes through the planet’s atmosphere, which absorbs some of the light. Methane is very good at sucking down infrared light in fact, so when you look in the infrared you see the star looking a bit dimmer.

If you take a spectrum — break the light up into individual colors — you can get pretty detailed information about the starlight. In this case, the absorption by methane in the planet’s atmosphere is pretty clear.

A spectrum is like a fingerprint: it identifies the element or molecule, how much of it there is, and even in some cases its temperature. The spectrum obtained using Hubble indicates the presence of methane and water vapor.

This is an important first step in understanding exoplanetary atmospheres, especially since we don’t know all that much about these giant Jupiters that orbit close in to their parent stars. In this case, the planet, called HD 189733b, is about 63 light years away, and orbits its star in just about two days. We don’t expect there to be life on it — the tops of the clouds are at about 1700 degrees Fahrenheit — but just finding these two molecules means they must be abundant in other planetary systems.

Now here’s a dash of some slightly chillier water on these findings. First, they aren’t surprising: I’d be far more surprised if we didn’t find these molecules in the planet’s atmosphere. We’ve seen plenty of both water and methane in space; in fact I worked on spectra of a brown dwarf that showed water vapor (literally steam in this case) in its atmosphere — plus, the water vapor was previously detected using Spitzer (the telescope, not the governor). Methane is a very simple molecule, and should form anywhere there is carbon, hydrogen, and low enough temperatures so that the molecule doesn’t break apart.

To me, the import of these findings is that with equipment we already have, we can probe the atmosphere of a planet over 600 trillion kilometers away. That’s cool. That implies very strongly that with the next generation of space and ground-based telescopes being built now, we’ll soon have an even better glimpse into the air out there.

And yes, I know that methane is not what makes, um, human emissions smell bad, but I couldn’t resist the title.

CATEGORIZED UNDER: Astronomy, Cool stuff, NASA, Science

Comments (23)

  1. MandyDax

    That is just amazing. :) Gotta love spectroscopic analysis, ya?

    Jack: What’s that smell?
    Cotton’s Parrot: Mercaptan, my captain!

  2. Joe Meils

    We can now detect farts at the distance of several hundred light years…

    Does this mean that this particular extra solar planet has Taco Bells?

    Seriously, it’s amazing to me that so much can be gleaned from what little we have to work with.

  3. Dennis

    Best title of a post ever!

  4. veritas36

    I can’t resist either —
    my 2 1/2 year old grandson named all the planets accurately and then explained, “Jupiter and Saturn stink because they are made of poop!”

  5. BoC

    Prof. Farnsworth would be proud.

  6. I agree on the Methane isn’t surprising front. When I saw that I thought “Wow! They’ll be finding Hydrogen in space next!!!” ūüėÄ

  7. billg

    How do we know the place isn’t crawling with billions of heat-resistant cows?

    But, seriously, here’s a question:

    At our current level of technology, are we able to detect anything that uniquely indicates the presence of at least equivalent technology on one of these planets? Could they detect us?

  8. Kullat Nunu

    Strictly OT: A possible naked eye gamma-ray burst detected. If you were last night on a very dark location and watched towards the right spot in the sky, you could have seen light from billions of light years away, unaided!

  9. Radwaste

    Say, Dr. Phil – what kind of forces conspire to keep methane, or any other gas, present on any body orbiting so close to its star? You mentioned a temperature twice that of Venus, and I like to think Mars had a bit more atmosphere before a couple of hard impacts tore it up; the Moon trails sodium atoms…

    So what does it take to blow off an atmosphere?

  10. decius

    How can it be affirmed with certainty that the water observed in the red dwarves spectra is in fact part of the objects atmosphere and not, for instance, orbiting them or otherwise placed between them and the observer?

    Isn’t it quite odd that a stellar object, albeit a rather cool one, would contain water?

  11. decius


    I meant to write brown dwarves, not red.

  12. Michael Lonergan

    This proves my theory that cows are the most populous life-form in the Universe.


    Actually, this is exciting. How long will it be before we can detect Earth-size planets? Also, when we are able to detect them, will we then pursue SETI on a more vigorous scale.

    This is slightly off topic, but I read an interesting article somewhere recently that addressed the question of the silence from the stars in relation to SETI. The author made an interesting point that basically stated the more technologically advanced we become, the quieter we become. Instead of signals “Leaking” into outer space, they are now more contained through fibre-optic networks and the internet. It was a little more in-depth than that, but I thought it was very thought provoking.

    In essence, what he was saying is that we should not expect to hear from advanced civilizations, unless they want us to, because they have gone quiet.

    Now, if we could just find a way to stop them from coming into my room late at night and taking me away… :()

  13. “This proves my theory that cows are the most populous life-form in the Universe.”
    Don’t take this the wrong way, Michael, but that statement is “udderly” ridiculous.

  14. blitzio

    The Smelloscope works!

  15. themadlolscientist

    ‚ÄúJupiter and Saturn stink because they are made of poop!‚ÄĚ ROFL

  16. Dave Hall

    Just what we need–a planet with an excess of dietary fiber.

  17. Jonas

    “the tops of the clouds are at about 1700 degrees Fahrenheit”

    Since when does astronomers use Fahrenheit?

  18. Jayson

    Sounds like we found planet Terserus, from the Rowan Adkinson Doctor Who spoof. “Planet of the Bottom Burpers.”

    Doctor: “They could communicate only through precicely modulated gastric emissions.”

    Companion: “What happened to them?”

    Doctor: “They discovered fire.”

    Seriously, though, every time I learn about new planet discoveries, I just can’t stop reading. It’s so cool!

  19. KC

    When the first exoplanet was discovered by a star’s “wobble,” I thought that was truly amazing. Now astronomers are able to pick out molecules in the atmospheres of exoplanets when it happens to pass between us and it’s star. In my lifetime we’ve gone from speculating about exoplanets to detecting them to picking out details about their atmospheres. What was once the stuff of Science Fiction is now in the realm of Science Fact. Truly amazing.

    Now, if we can just detect a planet around Alpha Centauri . . .

  20. Michael Lonergan

    You’re “milking” this for all it’s worth.

  21. Do does the presence of methane support theories that these planets started farther out and came up close to hug their stars? Otherwise I thought it was rarer the closer you got in (being rather abundant in our outer systems, and on earth created through different processes).

  22. Michael Lonergan

    Not necessarily. I do believe it supports my theory stated above, that there must be an extraordinary population of bovines on most planets. What really gives my theory credibility is the fact that cows are frequently mutilated or abducted by aliens, which are probably a highly evolved species of intelligent bovine. How else could they build and pilot their UFO’s across the vast reaches of space to earth?

  23. Tom Marking

    Here is an article written 28 years ago concerning the detection of an alien biosphere remotely. Even though this is almost three decades ago I’m sure the basic idea hasn’t changed that much in the intervening years – namely, that life causes a chemical disequilibrium in the planetary atmosphere which may be detected remotely.


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