Zeta Leporis, a 50 to 200 million year-old main sequence star in the northeastern section of the constellation Lepus (The Hare), became an interest to astronomers in the 1980s when a satellite using infrared measurements showed that dust orbited the star. Additional information was gathered in 2001 by American astronomers Michael Jura and Christine Chen from the University of California, Los Angeles. They discovered through Long Wavelength Spectrometer observations at the Keck Observatory in Hawaii that the dust was positioned in a disk roughly 6 astronomical units (AUs) away from Zeta Leporis. As a comparison, the planet Jupiter is about 5.3 AUs from the Sun—about 500 million miles (800 million kilometers).

More precise measurements were made in 2005 by Charles Telesco and Margaret Moerchen from the University of Florida, Gainesville. Using the Gemini South telescope in Chile, the two astronomers found that the majority of dust is located 3 AUs away from the star. (This distance is similar to the main asteroid belt located within our solar system, which primarily resides between 2.06 and 3.27 AUs from the Sun, or between the orbits of the planets Mars and Jupiter.) The mass of the belt is about 200 times the mass of our solar system’s asteroid belt.

Telesco, Moerchen, and colleagues report in a 2007 issue of Astrophysical Journal Letters that new measurements confirm the disk is 3 AUs from Zeta Leporis. Moerchen and Telesco theorize that the dust originated either from a steady bumping and grinding of several small asteroids or an isolated collision between two gigantic asteroids. In either case, it resulted in planetesimals, or solid objects in protoplanetary disks.

Such evidence by Telesco and Moerchen support the contention of astronomers that planets are forming around stars. This belief it held because asteroids result after planets are formed. Much like the creation of our solar system, asteroids were left behind after our planets formed.

Telesco and Moerchen will next determine the shape of the dust disk surrounding Zeta Leporis. They contend that a circular and uniform shape will show up if the disk was formed by the grinding of many small asteroids; whereas, it will appear noncircular and irregular if a large collision occurred. In any case, the astronomy team continues to gather data concerning the idea that Earth-sized planets are forming outside the solar system. (Any planet around a star other than the Sun is called an exosolar planet, or exoplanet.)

Important in this idea is the possibility that life may also exist on these Earth-sized exoplanets.

NOTE:

As of January 2007, astronomers have discovered 209 extrasolar planets—however; all but two of these planets have masses that are over ten times the mass of the Earth. The other two planets have masses a couple of times the mass of the Earth. Although most exoplanets have been very large in comparison to the Earth, our detection methods have been (so-far) restricted to only finding these larger planets.

However, on December 27, 2006, a French-led multinational team (consisting of the European Space Agency, Austria, Belgium, Brazil, Germany, and Spain) launched the first ever spacecraft to exclusively study planets outside the Earth’s solar system. The spacecraft Corot, which stands for COnvection ROtation and planetary Transits, will look for exoplanets closer to the size of the Earth.

More information about Corot can be found at: http://smsc.cnes.fr/COROT/ and http://www.esa.int/esaSC/120372_index_0_m.html.

Additional information about the asteroid belt around Zeta Leporis can be found at: http://www.spaceref.com:16080/news/viewpr.html?pid=5052.

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Astronomy  Research  Science  Solar system  Space  William Atkins