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.