Featured Research

from universities, journals, and other organizations

Astronomers Witness Silhouette Of Planet Crossing Distant Star, Proving The Existence Of Extra-Solar Planets

Date:
November 16, 1999
Source:
W. M. Keck Observatory
Summary:
Astronomers have witnessed for the first time a distant planet passing in front of its star, providing direct and independent confirmation of the existence of extrasolar planets that to date have been inferred only from the wobble of their star.

MAUNA KEA, HI - Astronomers have witnessed for the first time a distant planet passing in front of its star, providing direct and independent confirmation of the existence of extrasolar planets that to date have been inferred only from the wobble of their star.

"This is the first independent confirmation of a planet, and it also gives us the first-ever measure of the size of one of these planets," said Geoffrey Marcy, a professor of astronomy at the University of California, Berkeley.

Marcy and his colleagues, Paul Butler of the Dept. of Terrestrial Magnetism at the Carnegie Inst. of Washington and Steve Vogt of UC Santa Cruz and Lick Observatory, first detected a wobble on Nov. 5, 1999 with the Keck I telescope in the star called HD 209458. Ascribing the wobble to a nearby planet, they were able to estimate its orbit and approximate mass.

As with all new planets they detect, the team immediately brought it to the attention of a collaborator at Tennessee State University, astronomer Greg Henry, who works at the Center of Excellence in Information Systems. He operates several telescopes at the privately funded Fairborn Observatory in the Patagonia mountains of southern Arizona.

Henry turned his automated telescope on the star at the time Marcy and Butler predicted the planet would cross the face of the star IF the planet's orbital plane were lucky enough to carry it between Earth and the star. Until now, none of the 18 other extrasolar planets Marcy and Butler have discovered has had its orbital plane oriented edge-on to Earth so that the planet could be seen to transit the star, nor have any of the other planets discovered by other researchers.

This time, however, on Nov. 7, Henry observed a 1.7 percent dip in the star's brightness. A repeat measurement will take place on Nov. 14 as the planet orbits its star once every 3.523 days.

"This planetary transit occurred at exactly the time predicted from Marcy's observations, confirming absolutely the presence of a companion," Henry said. "This says that our indirect evidence for planets, the change in radial velocity of the star, really is due to planets. We've essentially seen the shadow of the planet." The parent star’s brightness has been observed constantly in the past four days and has not dimmed or “blinked,” except during the transit.

The star HD 209458 is 47 parsecs (153 light years or 1.4 million billion kilometers or 859,000 billion miles) away in the constellation of Pegasus, and is about the same age, color and size as our own Sun. It is very near the star, 51 Pegasi, around which the first extrasolar planet was discovered in 1995.

With the orbital plane of the planet known, the astronomers for the first time could determine precisely the mass of the planet and its density.

Interestingly, while the planet's mass is only about two-thirds (63 percent) of Jupiter's mass, its radius is 60 percent bigger than that of Jupiter. This fits with theories that predict a bloated planet when, as here, the planet is very close to the star.

The density, about 0.2 grams per cubic centimeter, means it is a gas giant like Jupiter. However, such gas giants could not have formed at the distance this planet is from its star, Henry said.

Various groups around the world have been searching for planets by looking for dimming of stars., or as Marcy says, "staring at the sky and seeing if any star blinks." To date, none of these searches has turned up a new planet.

"With this one, everything hangs together," Marcy said. "This is what we've been waiting for."

The research was supported by the National Aeronautics and Space Administration, the National Science Foundation, Sun Microsystems and the Richard Lounsbery Foundation.

-----------------------------------------

Transit of HD209458 G.Henry, Tennessee State Univ, G.Marcy, U.C. Berkeley, R.P.Butler, Dept. of Terrestrial Magnetism, and S.S.Vogt, UCO Lick Observatory report that HD 209458 (G0V) exhibits sinusoidal velocity variations with semi-amplitude of 81 m/s, indicating presence of a companion with Msini = 0.63 Jupiter masses and an orbital period of 3.523 d.

Photometry reveals a transit ingress at JD 2451490.70 with depth of 0.017 mag, consistent with the transit time predicted from the velocities. Further measurements of transits and velocities would be valuable. The next three predicted times of ingress occur at UT times: 15 Nov 6:19, 18 Nov 18:53, 22 Nov 7:28, all times uncertain by 1 hour.

If correct, the inferred mass is 0.63 Mjup and radius is 1.6 Rjup, implying a density of 0.21 g/cc . The enlarged radius is consistent with models of Jovian planets thermally expanded by stellar radiation (Saumon et al. 1996; Burrows et al. 1998). HD 209458 resides at a distance of 47 pc, with rotational Vsini = 3 km/s, and is chromospherically inactive, with an estimated age of 4.5 Gyr. Coordinates: RA = 22 03 10.7, DEC = +18 53 04 (2000), Vmag=7.65.


Story Source:

The above story is based on materials provided by W. M. Keck Observatory. Note: Materials may be edited for content and length.


Cite This Page:

W. M. Keck Observatory. "Astronomers Witness Silhouette Of Planet Crossing Distant Star, Proving The Existence Of Extra-Solar Planets." ScienceDaily. ScienceDaily, 16 November 1999. <www.sciencedaily.com/releases/1999/11/991116061234.htm>.
W. M. Keck Observatory. (1999, November 16). Astronomers Witness Silhouette Of Planet Crossing Distant Star, Proving The Existence Of Extra-Solar Planets. ScienceDaily. Retrieved September 2, 2014 from www.sciencedaily.com/releases/1999/11/991116061234.htm
W. M. Keck Observatory. "Astronomers Witness Silhouette Of Planet Crossing Distant Star, Proving The Existence Of Extra-Solar Planets." ScienceDaily. www.sciencedaily.com/releases/1999/11/991116061234.htm (accessed September 2, 2014).

Share This




More Space & Time News

Tuesday, September 2, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Raw: NASA Captures Solar Flare

Raw: NASA Captures Solar Flare

AP (Sep. 1, 2014) NASA reported the sun emitted a mid-level solar flare, on August 24th. NASA's Solar Dynamics Observatory captured the images of the flare, which erupted on the left side of the sun. (Sept. 1) Video provided by AP
Powered by NewsLook.com
Space Shuttle Discovery's Legacy, 30 Years Later

Space Shuttle Discovery's Legacy, 30 Years Later

Newsy (Aug. 30, 2014) The space shuttle Discovery launched for the very first time 30 years ago. Here's a look back at its legacy. Video provided by Newsy
Powered by NewsLook.com
Experiment Tests Whether Universe Is Actually A Hologram

Experiment Tests Whether Universe Is Actually A Hologram

Newsy (Aug. 27, 2014) Researchers at Fermilab are using a device called "The Holometer" to test whether our universe is actually a 2-D hologram that just seems 3-D. Video provided by Newsy
Powered by NewsLook.com
SpaceX’s Falcon 9 Rocket Explodes After Liftoff

SpaceX’s Falcon 9 Rocket Explodes After Liftoff

Newsy (Aug. 23, 2014) The private spaceflight company says it is preparing a thorough investigation into Friday's mishap. 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:
from the past week

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