Earth search

By Bryan Hance
Arizona Daily Wildcat
April 8, 1996

Arizona Daily Wildcat

illustration courtesy j. robert angel and neville woolf UA astronomers J. Robert Angel, right, and Neville Woolf say the hypothetical telescope OASES, above, could bring researchers closer to finding Earth-like planets and possibly extraterrestrial life.


Two UA astronomers are hastening the search for a celestial 'holy grail,'-the discovery of other Earth-like planets that could possibly contain life similar to that on Earth.

Regents astronomy professor J. Roger Angel and university astronomy professor Neville Woolf have been focusing attention on the search for Earth-like planets for years.

From their offices in the Steward Observatory-offices so cluttered and paper-strewn they give the impression the astronomers have literally 'plunged' into their work-Angel and Woolf are developing ideas that have attracted the interest of the international scientific community.

Their most recent endeavors have provided NASA with an outline on ways to search other solar systems for Earth-like planets and, hopefully, some form of extraterrestrial life.

Angel recently headed an international team of researchers to develop OASES, a hypothetical telescope array that would scan the heavens for planets similar in size and orbital placement to Earth. OASES would be placed in solar orbit, perhaps as far out as Jupiter, and could examine a star a day for surrounding planets.

In February, Angel told the American Association for the Advancement of Science that an OASES-like device could search solar systems 30 to 50 light years away.

Current methods to locate planets look for a star's gravitational 'wobble' caused by the presence of a nearby planet. While this technique can point out the existence of a planet, it gives astronomers no information other than the planet's location and mass.

Examining objects close to stars is a difficult task because the star's brightness obscures anything nearby.

An article authored by Angel and Woolf for the April edition of Scientific American calls such a search "as challenging as trying

to pick out a glowworm sitting next to a searchlight, both of which are thousands of kilometers away."

The OASES, an acronym for Outpost for Analysis and Spectroscopy of Exo-Solar Systems, would avoid such problems because its would 'cancel out' the star's light and leave only the light reflected by the planet.

The OASES array would also employ a technique pioneered by Woolf and Angel and ex-UA student Andrew Cheng in order to discern the planet's chemical makeup. In 1986, the three proposed examining a planet's mid-infrared wavelengths instead of the visible spectrum to determine what chemicals are present in a planet's atmosphere.

Specifically, the telescope would search for planets in the "Goldilocks orbit" surrounding stars. In this orbit, conditions are neither too hot or too cold, but 'just right,' and allow the right mix of oxygen, carbon dioxide and water to support life.

While the discovery of such a planet would not guarantee the discovery of a civilization of advanced beings, the planet could contain the equally exciting discovery of algae or other oxygen-producing organisms.

"To me, the question of whether other planets form life is as fundamental as you can get," Angel says.

The two astronomers are also involved with developments to advance the clarity of ground-based telescopes. The interference of Earth's atmosphere limits the clarity of ground-based telescopes, and the science of finding ways to eliminate this distortion is known as the science of adaptive optics.

The clearer the image, the better astronomers can look into the heavens for any number of things, including planets. While adaptive optics allows astronomers to better work from the ground, Angel says, the key to the OASES system is the adaptation of ground-based image corrections techniques to a space-based telescope.

Although the proposal submitted to NASA states that the OASES array could be developed and launched for around $2 billion by the year 2007, Angel says there is still a large amount of technological advancement that needs to take place.

"All the big telescopes push technology to the limit," Angel says. "This one more than any of them draws on just about all the advanced technology NASA has."

The space-based telescopic search for other planets could be delayed by a number of factors, such as bureaucratic delays or technological hang-ups. Angel says he is optimistic, however, because the promise of finding an Earth-like planet has an "extraordinary appeal" to both the public and to the scientific community.

Woolf says a colleague at one conference said such a system could be in place by 2015. Whether he lives to see such an endeavor become part of the space program is not the point, he says.

"You don't do this for yourself," Woolf says. "In science, you do it for the future."