George Claassen

Who says humans are special?

2005-06-17 08:22

Why would anyone believe that we as Earthlings are so special, that we have been specifically selected by a benign godlike father-figure who guards over us on this little planet in the Milky Way and has put us in charge of his "creation".

This was my first reaction to a news release this week by the American National Science Foundation that a new Earth-like planet has been discovered.

According to the NSF the discovery is a major step forward in the search for Earth-like planets beyond our own solar system. It is the smallest extrasolar planet yet detected. It is about seven-and-a-half times as massive as Earth, with about twice the radius, and it may be the first rocky planet ever found orbiting a normal star not much different from our Sun.

The NSF said all of the nearly 150 other extrasolar planets discovered to date around normal stars have been larger than Uranus, an ice-giant about 15 times the mass of the Earth. The discovery also brings us closer to one of the most profound questions that mankind can ask: Are we alone in the universe?" as Michael Turner phrased it as head of the Mathematical and Physical Sciences Directorate at the NSF, which provided partial funding for the research.

Rocky planet

The team measures a minimum mass for the planet of 5.9 Earth masses, orbiting its star (sun) Gliese 876 with a period of 1.94 days at a distance of 0.021 astronomical units (AU), or 2 million miles.

Though the team has no direct proof that the planet is rocky, its low mass precludes it from retaining gas like Jupiter, emphasised the NSF. Three other purported rocky planets have been reported, but they orbit a pulsar, the flashing corpse of an exploded star.

"This planet answers an ancient question," said team leader Geoffrey Marcy, professor of astronomy at the University of California, Berkeley. "Over 2 000 years ago, the Greek philosophers Aristotle and Epicurus argued about whether there were other Earth-like planets. Now, for the first time, we have evidence for a rocky planet around a normal star."

The research by Marcy, Paul Butler of the Carnegie Institution of Washington, theoretical astronomer Jack Lissauer of NASA/Ames Research Centre, and post-doctoral researcher Eugenio J Rivera of the University of California Observatories/Lick Observatory at UC Santa Cruz, was conducted at the Keck Observatory in Hawaii, and supported by NSF, the National Aeronautics and Space Administration, the University of California and the Carnegie Institution of Washington.

Finding more planets

Gliese 876 (or GJ 876) is a small, red star known as an M dwarf -the most common type of star in the galaxy. It is located in the constellation Aquarius, and, at about one-third the mass of the sun, is the smallest star around which planets have been discovered. Butler and Marcy detected the first planet there in 1998; it proved to be a gas giant about twice the mass of Jupiter.

Then, in 2001, they reported a second planet, another gas giant about half the mass of Jupiter. The two are in resonant orbits, the outer planet taking 60 days to orbit the star, twice the period of the inner giant planet, the NSF reported. Marcy's team plans to continue to observe the star Gliese 876, but is eager to find other terrestrial planets among the 150 or more M dwarf planets they observe regularly with Keck.

"So far we find almost no Jupiter-mass planets among the M dwarf stars we've been observing, which suggests that, instead, there is going to be a large population of smaller mass planets," Butler noted.

Which leaves me to wonder: if there is some sort of life on some of these planets, would they have created gods to their image like us and tell themselves they are special?

Send your comments to George or discuss this column now in our debating forum.

  • George Claassen is a science writer for Die Burger, South Africa's largest Afrikaans daily newspaper. His book Geloof, Bygeloof en Ander Wensdenkery: Hoe Vrees en Vals Hoop Mense Mislei, will be published shortly by Protea Boekhuis.

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