NSF PR 01-82 - October 15, 2000
More Planets Emerge with Solar System-Like Orbits
An international team of astronomers has discovered
eight new extrasolar planets, bringing to nearly 80
the number of planets found orbiting nearby stars.
The latest discoveries, supported by the National
Science Foundation (NSF) and NASA, uncovered more
evidence of what the astronomers are calling a new
class of planets. These planets have circular orbits
similar to the orbits of planets in our solar system.
At least two of the recently detected planets have
approximately circular orbits. This characteristic
is shared by two planets (one of them the size of
Jupiter) previously detected by the same team around
47 Ursae Majoris, a star in the Big Dipper constellation,
and one around the star Epsilon Reticulum. The majority
of the extrasolar planets found to date are in an
elongated, or "eccentric," orbit.
The further a planet lies from its star, the longer
it takes to complete an orbit and the longer astronomers
have to observe to detect it.
"As our search continues, we're finding planets in
larger and larger orbits," said Steve Vogt of the
Lick Observatory, University of California at Santa
Cruz. "Most of the planetary systems we've found have
looked like very distant relatives of the solar system
- no family likeness at all. Now we're starting to
see something like second cousins.
"In a few years' time we could be finding brothers
"This result is very exciting," said Anne Kinney, director
of NASA's Astronomy and Physics Division. "To understand
the formation and evolution of planets and planetary
systems we need a large sample of planets to study.
This result, added to others in the recent past, marks
the beginning of an avalanche of data which will help
to provide the answers."
The recently detected planets range in mass from 0.8
to 10 times the mass of Jupiter, the largest planet
in our solar system. They orbit their stars at distances
ranging from about 0.07 AU (astronomical unit, or
the distance from the Sun to Earth), to three AU.
The astronomers--from the United States, Australia,
Belgium and the United Kingdom--are searching the
nearest 1,200 stars for planets similar to those in
our solar system, particularly Jupiter-like gas giants.
Their findings will help astronomers assess the solar
system's place in the galaxy and whether planetary
systems like our own are common or rare.
For most of their discoveries, the astronomers have
used the Keck 10-meter telescope on Mauna Kea, Hawaii;
the Lick 3-meter in Santa Cruz, California; and the
3.9-meter Anglo-Australian Telescope in New South
Wales, Australia. To find evidence of planets, the
astronomers use a high-precision technique developed
by Paul Butler of the Carnegie Institution of Washington
and Geoff Marcy of the University of California at
Berkeley to measure how much a star "wobbles" in space
as it is affected by a planet's gravity.
The team also receives support from the UK and Australian