Comparison of Transiting Planet HD149026 with other
Transiting Planets
The recently discovered transit of a Hot Saturn orbiting HD149026 is
the shallowest, most challenging exoplanet transit detection acheived
to date. This transit, combined with radial velocity data, allows us
to measure the planet's size, mass and thus density. This allows us
to compare it to other known planets, both those within our solar
system and also transiting exoplanets. As more such discoveries are
made, comparitive planetology will enable us to understand how our own
planet, Earth, fits into the overall planetary scheme.
Transit Path for HD149026
This figure shows a full resolution diagram of a transit
of HD146026, with planet and star shown to scale. It represents
our best knowledge of the geometry of the system and comes
from the discovery paper,
Sato et al 2005, which provides full details.
Planet/Star Size Comparison
To give a rough idea of the sizes of known planets and their
stars, we compare the HD149026 system with the two other known
transiting exoplanets with well-determined sizes. Also shown are
the relative sizes of Jupiter and the Sun. Although Sun-Jupiter
transits cannot be seen from Earth, they could be seen from
a spacecraft in the outer solar system. Because HD149026 orbits
a somewhat older and more evolved sub-giant star, and because
the planet HD149026b is so dense, the small planet/star size ratio
causes a much smaller transit.
Transits of Mercury (1999, 2003) and Venus (2004)
One year ago, for the first time in a over century, the world
experienced a transit of the Sun by the planet Venus. In 1999,
(the same year as the discovery of the transiting exoplanet HD209458), and again in 2003 the
planet Mercury transited in front of the Sun. Here is a
comparison of these two solar system transits with the transit of
HD149026.
Venus (seen through cloud)
HD149026
Mercury (indicated by arrow)
For more beautiful images of the rare Venus transit, please
see NASA's Venus transit website at Science.NASA.gov
