Ten New Extrasolar Planets Announced

By Keith Cowing
August 7, 2000
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extrasolar planetA total of ten new planets was announced this morning at a meeting of the International Astronomical Union (IAU) in Manchester, UK. The total number of extrasolar planets now known is 50.

Jupiter-class planet orbiting Sunlike star Epsilon Eridani

Dr. William Cochran of the McDonald Observatory announced the discovery of a planet orbiting Epsilon Eridani in an elliptical and somewhat eccentric orbit with a semi-major axis of 297 million miles – a distance roughly equivalent to the distance that the asteroid belt is from our own sun. The planet is suspected of being a gas giant ranging from 80% to 160% the size of Jupiter and takes approximately 7 years to complete one orbit. [see detailed SpaceRef article for more information on the Epsilon Eridani discovery]

Three extrasolar planets from the US and evidence that multi-planet systems are common

The research team of Geoff Marcy (UC Berkeley) and Paul Butler (Carnegie Institute of Washington) announced that they had identified three new extrasolar planets. According to a press release, they are:

  • The star HD12661 is located at a distance of 121 light years, on the border of the constellation Aries near Triangulum. The planet’s period is 250 days, with an average distance from its
    star of 0.80 AU. (One astronomical unit, or AU, is 93 million miles, the distance from the Earth to the Sun.) The lower limit on its mass is 2.8 Jupiter masses.

  • The star HD 92788 is located 104 light years from Earth in the constellation Sextans. The planet’s period is 341.7 days, and it orbits at an average distance of 0.98 AU. Its mass is at
    least 3.7 Jupiter masses.

  • The star HD 38529 is 137 light years away, in the constellation Orion. The planet’s period is 14.3 days; its average distance from the star is 0.13 AU. The lower limit on its mass is
    0.77 Jupiter masses.

In addition to these three discoveries, analysis by Debra A. Fischer, a post-doctoral fellow at UC Berkeley, suggests that many of the previously identified extrasolar planets may well be members of multi-planet solar systems. Fischer examined data that had been collected for 12 stars that had been observed long enough to provide evidence that planets might be present. In her analysis, Fischer found that 5 of the systems “exhibit unexplained wobbles that could result from the tug of a companion, whether another planet, an unseen star or something in between.”

Seven Planets from Europe- two of which are the size of Saturn

Astromomers working with the European Southern Observatory announced the discovery of 7 new planets – one of which (orbiting star HD 92788) is a confirmation of data obtained by Marcy and Butler’s team. 5 of the extrasolar planets were discovered with CORALIE including a 2 Saturnian planet system.
1 extrasolar planet was detected with ELODIE. One detection, orbiting HD 168443 system may reresent planet and a brown dwarf.

The planets discovered are:

  • HD 168443 (planet and a brown dwarf?)
  • HD 6434 – spectrum G3IV; distance 40.3 parsecs (131 light years); period 22.09 days; eccentricity 0.3; m2sin i (minimum mass) 0.48 Jupiter mases; semimajor axis (a) 0.15
    AU; site – ESO.

  • HD 19994 – spectrum F8V; distance 22.2 parsecs (72 light years); period 454.2 days; eccentricity 0.2; m2sin i (minimum mass) 1.8 Jupiter mases; semimajor axis (a) 1.3

  • HD 92788 – spectrum G5; distance 32.3 parsecs (105 light years); period 340.8 days; eccentricity 0.36; m2sin i (minimum mass) 3.8 Jupiter mases; semimajor axis (a) 0.94

  • HD 121504 – spectrum G2V; distance 44.4 parsecs (145 light years); period 64.62 days; eccentricity 0.13; m2sin i (minimum mass) 0.89 Jupiter mases; semimajor axis (a)
    0.32 AU

  • HD 190228 – spectrum G5IV; distance 62.1 parsecs (203 light years); period 1127 days; eccentricity 0.43; m2sin i (minimum mass) 5.0 Jupiter mases; semimajor axis (a) 2.3
  • HD 83443 – 2 Saturn-class planets

Two Saturn-class planets have been observed orbiting star HD 83443. According to ESO their characteristics are:

  • HD 83443 b. Period 2.9853 day; minimum mass (m2 sin i) 0.35 Jupiter masses [1.17 Saturn masses] ; eccentricity 0.08; semi-major axis (a) 0.038 astronomical units; K velocity 56 m/s.

  • HD 83443 c. Period 29.83 day; minimum mass (m2 sin i) 0.15 Jupiter masses [0.50 Saturn masses]; eccentricity 0.42; semi-major axis (a) 0.17 astronomical units; K velocity 14 m/s.

Related Links

° Astronomers report discovery of three new extrasolar planets, plus hints of many multi-planet systems, press release, UC Berkeley

° European Southern Observatory: Six Extrasolar Planets Discovered, press release

° Extrasolar Planet Discoveries, Geneva Extrasolar Planet Search Programmes

° Press Releases, International Astronomical Union XXIVth General Assembly, 7 – 18 August 2000 Manchester, UK

° The Geneva Extrasolar Planet Search Programmes

Background Information

° Discovery of Smallest Known Brown Dwarf Announced, SpaceRef

° Brown Dwarf “Missing Links” Found, SpaceRef

° Eight Extrasolar Planets Discovered Circling Sun-like Stars, SpaceRef

° Eight New Very Low-Mass Companions to Solar-Type Stars Discovered at La Silla, ESO press release

° NASA Announces a Significant Advance in Planet Hunting, SpaceRef

° Extrasolar Planets, SpaceRef Directory

° Very Early Planetary Formation Observed in Orion?, SpaceRef

° Hubble Confirms Abundance of Protoplanetary Disks Around Newborn Stars, Space Telescope Science Institute, 1994

° Hot Jupiters and Rare Earths: Planets are common. Are we?, SpaceRef

° NASA’s Ames Research Center Uses Transit Photometry to Confirm Existence of Extrasolar Planet Circling HD 209548, SpaceRef

° Six New Extrasolar Planets Discovered, SpaceRef

° Of Planetary Transits Near and Far, SpaceRef

SpaceRef co-founder, Explorers Club Fellow, ex-NASA, Away Teams, Journalist, Space & Astrobiology, Lapsed climber.