Haleakala Telescope Finds New Planet
|Left: The XO telescope, on
the summit of Haleakala, consists of two 200-millimeter telephoto camera
lenses. The lenses are attached to electronic devices that measure
slight dips in light output from stars when an object crosses in front
of them. Credit:
NASA, ESA, and J. Stys (STScI). Right: The location of the star
An international team of astronomers has used a small, automated telescope
located on Haleakala to discover a planet orbiting a Sun-like star 600
light-years from Earth.
The team, led by Peter McCullough of the Space Telescope Science Institute
in Baltimore, includes IfA astronomer James Heasley. They used a relatively
inexpensive telescope made from off-the-shelf components to scan the skies
for extrasolar planets. Called the XO telescope, it consists of two 200-millimeter
telephoto camera lenses and looks like a pair of binoculars.
The team found the planet, dubbed XO-1b, by detecting a two percent dip
in the star's light output when the planet passed in front of the star.
The observation also revealed that XO-1b is in a tight four-day orbit around
its parent star, which is in the constellation Corona Borealis.
The team confirmed XO-1b's existence by using the Harlan J. Smith Telescope
and the Hobby-Eberly Telescope at the University of Texas's McDonald Observatory
to measure the slight wobble induced by the planet on its parent star.
This technique, known as the radial-velocity method, allowed the team to
calculate a precise mass for the planet, which is about nine-tenths the
size of Jupiter.
Of the approximately 200 extrasolar planets found to date, only 10 have
been found using the transit method employed by the XO telescope. All of
the others were found using the radial-velocity method on large telescopes
like the Keck on Mauna Kea. While very powerful for determining whether
a star has a planetary companion, the radial-velocity method is limited
to looking at one star at a time. The transit approach used by XO can be
used to examine many thousands of stars every night.
Heasley stated, "In the future, we can use small telescopes such
as XO to find out which stars might have planets orbiting around them,
and then use larger telescopes such as those on Mauna Kea to confirm such
discoveries. In searching for planets, the game is all about numbers. The
more stars we can examine, the better our chances of actually finding an
Several IfA staff members on Maui—Bill Giebink, Les
Hieda, Jake Kamibayashi, Daniel O'Gara, and Joey Perreira—have
played important roles in the construction and maintenance of the telescope.