HD209458 Planetary System Data

Planet DesignationOrbital Elements Orbital Period (years) Mass (ME) Equatorial Radius (RE) Discovery
Semimajor Axis (AU)Eccentricity Discoverer NameAnnouncement Date
HD209458 b 0.0460.02 0.009648200 18 G. Marcy, et al1999 Nov 12
1 AU = 1.49597870691·1011 m            1 year = 365.25 days = 31557600 s            1 ME = 5.9742·1024 kg            1 RE = 6.378136·106 m

Transits of the star HD209458 by its planet, HD209458 b, have been detected.
HD209458 is the first planetary system for which such transits have been detected.

These transits have allowed the mass of the planet to be calculated, and the composition of the planet's atmosphere to be measured.

The atmosphere of the planet contains less sodium than expected for a Jupiter-class planet.
This may indicate the presence of high-altitude clouds in the atmosphere.

The discovery of the planet and the determination of its mass were announced on 1999 Nov 12.
The measurement of the planet's atmospheric composition was announced on 2001 Nov 27.

The detection of hydrogen escaping from the atmosphere of the planet was announced on 2003 Mar 12.

Copyright © 1996, Alexander J. Willman, Jr. All rights reserved.
The URL of this page is: http://www.princeton.edu/~willman/Planetary_systems/HD209458.html
This page was last updated: 2003 Apr 9
You may contact Alex at: willman@Princeton.EDU

Go Back to the table of Known Planetary Systems
Go Back to the list of Alex Willman's Recent Work
Go Back to Alex Willman's Home Page