Featured Research

from universities, journals, and other organizations

Astronomers Report Discovery Of Three New Extrasolar Planets, Plus Hints Of Many Multi-Planet Systems

Date:
August 8, 2000
Source:
University Of California, Berkeley
Summary:
As they add another three to the list of 41 known planets outside our solar system, a team of astronomers based at the University of California, Berkeley, is beginning to see patterns, including hints that many extrasolar planets may have siblings.

Manchester, England -- As they add another three to the list of 41 known planets outside our solar system, a team of astronomers based at the University of California, Berkeley, is beginning to see patterns, including hints that many extrasolar planets may have siblings.

Related Articles


To date, only one Sun-like star has been found with multiple planets: Upsilon Andromedae, around which the same team discovered three planets last year.

However, Debra A. Fischer, a post-doctoral fellow at UC Berkeley, looked more closely at data for 12 stars her team has been observing long enough to betray the existence of long-period planets, if any, and around which they had already discovered one planet. She found that five -- nearly 50 percent -- exhibit unexplained wobbles that could result from the tug of a companion, whether another planet, an unseen star or something in between.

"This is the first time anyone has noticed that such a high percentage of stars with one known planet show evidence of a second companion," Fischer said.

All five planets with a possible second planetary companion are large gas giants very near their central star, so close that most astronomers think such planets must have formed farther out and later migrated inward.

"It's important to know if there are other companions out there," Fischer said, "because anything else in the system will affect the dynamics and theories of how the planets moved in and parked in their current orbits."

The analysis, plus data on the three new extrasolar planets, will be presented Aug. 7 by team leaders Geoffrey Marcy, professor of astronomy at UC Berkeley, and Paul Butler, an astronomer at the Carnegie Institution of Washington, at the International Astronomical Union meeting in Manchester, England. A paper describing the results by Fischer, Marcy, Butler and their colleagues will appear soon in the Astrophysical Journal.

The three new planets discovered around the stars HD12661, HD 92788 and HD 38529 are large gas giants similar to the planet Jupiter. All are in highly eccentric orbits that alternately bring them close to the planet and carry them far away. This dance alternately drags the star toward and away from Earth by a distance about half the radius of the star, causing a Doppler shift in the star's light that astronomers can detect.

--------------------LIST OF NEW PLANETS

The star HD12661 is located at a distance of 121 light years, on the border of the constellation Aries near Triangulum. Its 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. Its 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. Its 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.---------------------

One of the stars, HD 38529, has a planet that whips around in 14.3 days. This planet alone cannot explain the observed wobble in the star, however, leading Fisher and her colleagues to speculate that it has a second companion at a much greater distance from the star.

"We see indication of a second companion, but we can't be sure because we only see a portion of the orbit," Fischer said. "The companion could be a dim star, a brown dwarf or another planet."

Brown dwarfs are failed stars -- large objects just shy of the mass necessary to sustain hydrogen burning in their core.

More data on another star, 55 Cancri, around which the team found a planet in 1996, indicates it may have a second companion too, Fischer noted. Such a planet, if real, would be at least 3-4 solar masses and have a period of 4,715 days -- about 13 Earth years -- in a highly eccentric orbit at an average distance of 5.5 AU, similar to Jupiter's orbit around our Sun. One astronomical unit, or AU, is 93 million miles, the distance from the Earth to the Sun.

"This is still speculative," she cautioned. Still, it led her to look more closely at the dozen stars with known planets for which her team had at least two years of data, enough to show evidence of a second, more distant companion orbiting with a long period.

Five of these planets turned out to have "residual velocities" that could not be explained by a single planet, suggesting the presence of a second companion. The team must collect data for a complete orbit before concluding that another companion exists.

The authors noted that detecting a second companion requires an accurate knowledge of the wobbles caused by the already known planet, which is possible only when that planet is near the star and has a short period. Thus, stars with more distant planets might well have other companions that would not be detectable using the Doppler method.

Interestingly, all three of the new stars are rich in the heaviest atoms, like iron, meaning the stars were formed from dust that had already been cycled through at least one other star. This continues a trend of high metallicity among stars with known planets.

Marcy, Butler, Fischer and their colleagues are monitoring about 900 stars in the northern sky using the University of California's Lick Observatory in California and the Keck Observatories in Hawaii, plus another 200 in the southern sky with the Anglo-Australian Telescope. They look for wobbles that indicate a planet may be circling the distant sun. To date they have discovered 30 extrasolar planets, including the three reported today. In all, there are now 44 known stars with planets or planetary systems, excluding our own.

"We're now at a stage where we are finding planets faster than we can investigate them and write up the results," Marcy said. "It's wonderful. Planet-hunting has morphed from the marvelous to the mundane."

The data are feeding other projects, too, including a test of adaptive optics at the Keck Telescopes. With adaptive optics, astronomers could potentially see larger planets around nearby stars. Such observations underway now could set upper limits on the masses of the planets, whereas Doppler observations set only a lower limit for the mass.

###

Complete information on extrasolar planets can be found at the team's Web site, http://www.exoplanets.org/.


Story Source:

The above story is based on materials provided by University Of California, Berkeley. Note: Materials may be edited for content and length.


Cite This Page:

University Of California, Berkeley. "Astronomers Report Discovery Of Three New Extrasolar Planets, Plus Hints Of Many Multi-Planet Systems." ScienceDaily. ScienceDaily, 8 August 2000. <www.sciencedaily.com/releases/2000/08/000807062604.htm>.
University Of California, Berkeley. (2000, August 8). Astronomers Report Discovery Of Three New Extrasolar Planets, Plus Hints Of Many Multi-Planet Systems. ScienceDaily. Retrieved October 25, 2014 from www.sciencedaily.com/releases/2000/08/000807062604.htm
University Of California, Berkeley. "Astronomers Report Discovery Of Three New Extrasolar Planets, Plus Hints Of Many Multi-Planet Systems." ScienceDaily. www.sciencedaily.com/releases/2000/08/000807062604.htm (accessed October 25, 2014).

Share This



More Space & Time News

Saturday, October 25, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Raw: China Launches Moon Orbiter

Raw: China Launches Moon Orbiter

AP (Oct. 24, 2014) China launched an experimental spacecraft Friday to fly around the moon and back to Earth in preparation for the country's first unmanned return trip to the lunar surface. (Oct. 24) Video provided by AP
Powered by NewsLook.com
China Prepares Unmanned Mission To Lunar Orbit

China Prepares Unmanned Mission To Lunar Orbit

Newsy (Oct. 23, 2014) The mission is China's next step toward automated sample-return missions and eventual manned missions to the moon. Video provided by Newsy
Powered by NewsLook.com
Russian Cosmonauts Kick Off Final Spacewalk of 2014

Russian Cosmonauts Kick Off Final Spacewalk of 2014

Reuters - US Online Video (Oct. 22, 2014) Russian cosmonauts Maxim Suraev and Alexander Samokutyaev step outside the International Space Station to perform work on the exterior of the station's Russian module. Rough Cut (no reporter narration) Video provided by Reuters
Powered by NewsLook.com
Comet Siding Spring Grazes Mars' Atmosphere

Comet Siding Spring Grazes Mars' Atmosphere

Newsy (Oct. 19, 2014) A comet from the farthest reaches of the solar system passed extremely close to Mars this weekend, giving astronomers a rare opportunity to study it. Video provided by Newsy
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:

Breaking News:

Strange & Offbeat Stories


Space & Time

Matter & Energy

Computers & Math

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile: iPhone Android Web
Follow: Facebook Twitter Google+
Subscribe: RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins