Hubble Makes First Direct Measurements of Atmosphere on World Around Another Star

Hubble Telescope ^ | November 27, 2001

[The_Victor]

Hubble Makes First Direct Measurements of Atmosphere on World Around Another Star

1. How did they detect the atmosphere?

Astronomers discovered the atmosphere by watching how starlight dimmed slightly when the planet crossed in front of its star, an event known as a transit. During the transit, a small amount of starlight passed through the planet's atmosphere on its way to Earth. Hubble's spectrograph collected the light and dispersed it into the colors of the spectrum, which yielded clues about the atmosphere's chemical makeup. When astronomers analyzed the spectrum, they found the telltale "fingerprint" of sodium.

2. What does sodium reveal about the planet?

Astronomers expected to find sodium in the planet's atmosphere. Discovering sodium does not mean that life exists on the alien planet. In fact, astronomers don't think the planet can sustain life. It is a Jupiter-sized planet made up mostly of gas and is 20 times closer to its star than the Earth is to the Sun. The planet is so close to its star that its atmosphere is heated to a torrid 2000 degrees Fahrenheit (1100 degrees Celsius).

The astronomers, however, actually found less sodium than scientists had predicted for a Jupiter-class planet, leading to one interpretation that high-altitude clouds in the alien atmosphere may have blocked some of the starlight. The astronomers discovered the sodium by analyzing the starlight that passed through the planet's atmosphere.

3. What are the conditions for life?

A key ingredient for life as we know it is oxygen. The most suitable planets for life, where oxygen may be abundant, are small, rocky planets like Earth that orbit at comfortable distances away from their stars. Finding these planets and probing their atmospheres for signs of life is beyond the scope of current telescopes and detection techniques, including the transit method used in this Hubble observation. So far, astronomers have been successful at discovering a parade of alien planets. But all of them are Jupiter-sized giants that are much larger than Earth. Some of them orbit perilously close to their stars, like the planet whirling around the star HD 209458.

[The_Victor]

The title sounds more impressive than the details, but this is still totally cool.

[Tennessee_Bob]

2. What does sodium reveal about the planet?

It's a bad place to go on vacation if you have problems with your blood pressure??

And yes, it is real cool. Part of the reason I've volunteered to work at the college observatory.

[alaskanfan]

When astronomers analyzed the spectrum, they found the telltale "fingerprint" of sodium.

I would guess that this, combined with the proximity to the star and the temp reported in the article, would indicate that sodium exists as a gas on this planet?

[gcruse]

I would guess that this, combined with the proximity to the star
and the temp reported in the article, would indicate that sodium
exists as a gas on this planet

   If I recall correctly, sodium vapor lamps are orange in color.
   The planet might look like a cross between Jupiter and
   and a tangarine.

[cweese]

...so this baby is working just as algore said it would
right after he invented it???
:-)?

[The_Victor]

..so this baby is working just as algore said it would right after he invented it??? :-)?

If algore had invented it, HST would be pointed at the earth. (Voice of excited scientist, "Look, that's the chemical signature for water, and oxygen, and nitrogen. This place could support life!)

[Wright is right!]

"If I recall correctly, sodium vapor lamps are orange in color. The planet might look like a cross between Jupiter and and a tangerine."

Actually, PURE sodium vapor lamps are YELLOW. Mercury vapor lights are bluish. Most of the gas-dischaarge street lighting in use in the US today utilizes a mixture of gases to obtain the characteristic pinkish-orange tint.

Michael

[dr_who]

Something tells me that they couldn't detect the atmosphere of an Earth size planet that way. Or even detect the planet for that matter. Boggles the mind that they can do this anyway.

[Dog]

Ping!

[RadioAstronomer]

I agree. On the surface this does not sound like that big a deal, however, what is does show is that planetary systems and planets are not only surrounding other stars, but retain atmospheres also. IMHO, we will eventually find earth-like planets.

[RadioAstronomer]

Bump

[jennyp]

WAAAAYYYY cool BUMP!

[jennyp]

Hi, RA!

I have a question. Do you know how they did this? Seems to me they either:

A. Took the whole starlight with the planet in front of it & subtracted the colors they'd get without the planet in front of it & the difference is (should be) the colors of the planet's atmosphere, or

B. Were able to mask out the part of the star's image that the planet is not passing in front of, & analyzed that spectrum directly.

Are they able to get a star to show up as more than just a single pixel of light? I.e. how big an image can they produce of the star itself?

And if so, have they ever been able to get a picture of a sunspot?

[Physicist]

Or, just guessing,

C. Looked at the whole spectrum and picked out absorption lines that exhibited a Doppler wobble with respect to the emission lines as the planet moved around the star.

[Physicist]

Whoops, it helps if I read the article. Your "A" is essentially correct, although "C" is the much more elegant technique. ;-)

[PatrickHenry]

Bah! Humbug! The money spent on this stuff would be better spent on food stamps.
</Jesse Jackson mode>

[RightWhale]

how they did this?

Astronomers are using computers to make most of their discoveries these days. It's similar in a way to looking for a signal from a galactic civilization, except in this case, they found the signal of sodium, which is one of the easier ones to find. It will be 10 years until NASA can launch its hyperlarge planet-finder telescope, assuming they somehow retain the budget to do so. At that time they will be able to image extra-solar planets, barely.

[Brett66]

I think we're moving into a 'golden age' of discovery in regards to exo-planets. Once we have the instruments deployed, I think some incredible discoveries will occur. I can envision them finding a planet with 5 times the mass of the Earth with trace amounts of oxygen or some other bizarre environment that doesn't match well to our understanding of life. I can't wait until we can get clear, direct images of these planets. We just need massive space based interferometers to get voyager quality images of exo-planets. With such an interferometor, it would be like owning a starship to tour the interstellar neighborhood. I think it will really capture the public's imagination. At least for a short time.

[Brett66]

Indexing

[RadioAstronomer]

Oh no! I knew I would forget to ping someone. I will make up a ping list! You won't be left out again!!!!