Explanation:
This crowded star field
towards the center of our Milky Way Galaxy
turns out to be a great place to search for
planets beyond
our solar system.
In fact, repeatedly imaging about 180,000 stars
in the field
over a one week period, the Hubble Space Telescope
enabled astronomers to conduct the Sagittarius Window Eclipsing
Extrasolar Planet Search (SWEEPS).
Their search looked for brief, periodic dips in
brightness caused as a large planet
eclipses
or transits its parent star.
Since chances of seeing such an eclipse are slim,
it was a definite advantage to examine as many stars as possible.
In the end, SWEEPS astronomers
found 16
candidate stars (green circles identify 11 in this cropped picture)
that are likely closely orbited by large Jupiter-sized planets
with periods of a few days or less.
Large planets orbiting so close to their stars are termed
hot Jupiters.
Kepler,
a future NASA mission, is intended to extend
the transit technique to search for
Earth-sized planets.
