For the first
time, scientists have detected water vapour in the atmosphere of a Jupiter-like planet orbiting a
nearby star using a novel technique.
The new technique could help researchers
learn about how many planets with water - like Earth - exist within our galaxy,
researchers said.
Researchers at The California Institute of Technology (Caltech) and several other
institutions analysed the gaseous atmospheres of such extrasolar planets and have
made the first detection of water in the atmosphere of the Jupiter-mass planet
orbiting tau Bootis star. Scientists
have previously detected water vapour on a handful of other planets, but these
detections could only take place under very specific circumstances, said
Alexandra Lockwood, the first author of the study. Lockwood and her adviser Geoffrey Blake
applied a novel technique for finding water in a planetary atmosphere. Other
researchers had used similar approaches previously to detect carbon monoxide in
tau Bootis b. The method utilised the radial velocity (RV) technique - a
technique commonly used in the visible region of the spectrum to which our eyes
are sensitive - for discovering non-transiting exoplanets.
Jupiter is the fifth planet from the Sun and the
largest planet in the Solar System. It is a gas giant with mass one-thousandth
of that of the Sun but is two and a half times the mass of all the other
planets in the Solar System combined. Jupiter is classified as a gas giant
along with Saturn, Uranus and Neptune. Together, these four planets are
sometimes referred to as the Jovian or
outer planets. The planet was known by astronomers of ancient times, and
was associated with the mythology and religious beliefs of many cultures. The
Romans named the planet after the Roman god Jupiter. When viewed from Earth,
Jupiter can reach an apparent magnitude of −2.94, bright enough to cast
shadows, and making it on average the third-brightest
object in the night sky after the Moon and Venus. (Mars can briefly match
Jupiter's brightness at certain points in its orbit.) Jupiter is primarily
composed of hydrogen with a quarter of
its mass being helium, although helium only comprises about a tenth of the
number of molecules. It may also have a rocky core of heavier elements, but
like the other gas giants, Jupiter lacks a well-defined solid surface. Because
of its rapid rotation, the planet's shape is that of an oblate spheroid (it
possesses a slight but noticeable bulge around the equator). The outer
atmosphere is visibly segregated into several bands at different latitudes,
resulting in turbulence and storms along their interacting boundaries. A
prominent result is the Great Red Spot, a giant storm that is known to have
existed since at least the 17th century when it was first seen by telescope.
Surrounding Jupiter is a faint planetary ring system and a powerful
magnetosphere. There are also at least 67 moons, including the four large moons
called the Galilean moons that were first
discovered by Galileo Galilei in 1610. Ganymede,
the largest of these moons, has a diameter greater than that of the planet Mercury.
Jupiter has been explored on several
occasions by robotic spacecraft, most notably during the early Pioneer and
Voyager flyby missions and later by the Galileo orbiter. The most recent probe
to visit Jupiter was the Pluto-bound New Horizons spacecraft in late February
2007. The probe used the gravity from Jupiter to increase its speed. Future
targets for exploration in the Jovian system include the possible ice-covered
liquid ocean on the moon Europa.