Category Archives: origins of life

extrasolar planets, origins of life

Methane!

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An Organic Molecule Worth Detecting

Organic molecules are the key ingredients for life. They are what scientists call life’s “building blocks.” So, it’s a big deal when astronomers detect such things in interstellar space. Even more so when they find them in places where life might form — like on extrasolar planets.

Astronomers using the Hubble Space Telescope have made the first detection ever of molecules of the gas methane in the atmosphere of a planet orbiting another star. As you can imagine, this is a huge breakthrough because identifying signs of life on other planets depends on finding evidence of such organic molecules. Under the right circumstances methane can play a key role in the chemical reactions that have to occur in the life-creation chain.

Methane has been detected on most of the planets, and many moons and comets in our Solar System in both gas and ice form. However, this is the first time any organic molecule like methane has been detected on a world orbiting another star. It was found in the atmosphere of a Jupiter-sized planet called HD 189733b by scientists using HST’s Near-infrared Camera and Multi-object Spectrograph (NICMOS) to break down the light from a more-distant star as it passed through the planet’s atmosphere. The planet happened to pass in front of the star, and as the star’s light traveled through the atmosphere, some of it was absorbed by gases, including methane and water vapor. That left a unique fingerprint in the spectral data, telling the astronomers that those gases exist at the planet.

Methane is composed of carbon and hydrogen. On Earth, methane is a naturally occurring product, and is also produced by a processes and life forms as varied a cattle, termines, the decay of matter in ocean and wetland environments, waste landfills and as a by-product of energy generation. It’s pretty unlikely that the methane on the distant planet around HD 189733b is generated by life, since the planet’s atmosphere is much too hot. Chances are HST noted higher methane levels on the night side of the planet, where the gas can exist in greater amounts. On the day side, the higher heat would tear apart the molecules, resulting in a lower amount of methane.

These measurements are a big step toward understanding other atmospheric conditions at this planet, or others where organic molecules will be found with HST, Spitzer, and the future James Webb Telescope.

exoplanets, extrasolar planets, HII regions, molecular clouds, origins of life

The Science of Life

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What Came First?

Yesterday I was at an all-day symposium about the Origins of Life, held by the Radcliffe Institute and the Harvard University Origins of Life Initiative. The keynote speakers covered some of the major bases in a very complex field of play and I came away with the notion that there are no “chicken and egg” questions here, only a lot of people wondering which PART of the egg came first.The image “https://i0.wp.com/www.eso.org/public/outreach/press-rel/pr-2008/images/phot-06-08-preview.jpg?resize=397%2C307” cannot be displayed, because it contains errors.

While I was at the meeting, a couple of press releases plopped into my Email box. Both of them were about subjects that come up whenever you talk about origins of life in the universe. The first was from the European Southern Observatory, showing an artistically beautiful set of data from astronomers who have mapped the distribution of material inside a dark nebula called the Corona Australis molecular cloud. Molecular clouds are places where astronomers have found a number of organic molecules needed for the creation of life. They’re also quite dusty, threaded with the metallic minerals that life also needs. So, it stands to reason that such places would be part of the “egg” that we study when we ask questions about how life got started here on Earth. This is because the solar system formed from such a cloud some 5 billion years ago.

The ESO image is actually a composite of near-infrared scans of the cloud made using an instrument sensitive to such wavelengths. Near infrared light helps astronomers probe the insides of such clouds to understand how they form and evolve.

The other press release that landed in my IN box was from the University of California at Santa Cruz and deals with exoplanets, another piece of the “origins of life” egg. These are worlds around other stars, and are places where we hope to find more life in the universe, some day. In particular, the news here is that a new study suggests that a planet similar to Earth (a “terrestrial type”) could be orbiting one of the stars in the Alpha Centauri system, the closest stars to our own. They lie about 4.3 light-years from us, which for celestial neighborhoods, is basically the house next door. If it does exist, might it look like Earth (as shown in this artist’s conception, done by Mark Fisher)? We won’t know until we find it.

Now, the news here is really that the planet MAY be orbiting the star and that astronomers could detect it using techniques that are in use today to look for stars around other planets. The techniques, which came in for some discussion at Radcliffe yesterday, center around using something called the Doppler detection method. It doesn’t image a planet directly because finding something as small as a planet in the glow of a star’s light is quite difficult, if not impossible in many cases. The Doppler method measures the shifts in light that we see coming from a star as a planet orbits around it. The gravitational pull of the planet is just enough to cause the star to wobble, and that affects how it looks through a spectroscope (the instrument used to study the spectra of light coming from objects).

Detecting the wobbles from big planets, what are often called “Jupiter-sized” planets is pretty straightforward because they induce big wobbles. Little planets, like potential Earth-like ones, cause small wobbles. These are harder to detect. But, according to a computer simulation done by the folks at UC-Santa Cruz, it can be done. The two astron0mers who did the study, Gregory Laughlin (of UCSC) and Debra Fischer (of San Francisco State University), are now leading an international program to study Alpha Centauri using the 1.5-meter telescope at Cerro Tololo Inter-American Observatory in Chile. They are hoping to find real planets, based on their simulation and using the technique of Doppler detection.

These two studies are chewy and tasty pieces of the larger pie that is the search for life (and its origins) in the cosmos. It’s only a matter of time before those other planets will be found (if they’re there). We continue to study how life began on our own planet. What we learn should be helpful if and when we ever find life elsewhere in the cosmos.