WASP-18 is a
magnitude 9
star
A star is an astronomical object comprising a luminous spheroid of plasma (physics), plasma held together by its gravity. The List of nearest stars and brown dwarfs, nearest star to Earth is the Sun. Many other stars are visible to the naked ...
located in the
Phoenix constellation
A constellation is an area on the celestial sphere in which a group of visible stars forms Asterism (astronomy), a perceived pattern or outline, typically representing an animal, mythological subject, or inanimate object.
The origins of the e ...
of the
southern hemisphere.
It has a mass of 1.25
solar mass
The solar mass () is a standard unit of mass in astronomy, equal to approximately . It is often used to indicate the masses of other stars, as well as stellar clusters, nebulae, galaxies and black holes. It is approximately equal to the mass ...
es.
The star, although similar to Sun in terms of overall contents of heavy elements, is depleted of carbon. Carbon to oxygen molar ratio of 0.23 for WASP-18 is well below solar ratio of 0.55.
Planetary system
In 2009, the
SuperWASP project announced that a large,
hot Jupiter type
extrasolar planet, ''
WASP-18b'', was orbiting very close to this star.
Observations from the
Chandra X-ray Observatory failed to find any
X-rays coming from WASP-18, and it is thought that this is caused by WASP-18b disrupting the star's
magnetic field
A magnetic field is a vector field that describes the magnetic influence on moving electric charges, electric currents, and magnetic materials. A moving charge in a magnetic field experiences a force perpendicular to its own velocity and to ...
by causing a reduction in
convection in the
star's atmosphere. Tidal forces from the planet may also explain the higher amounts of
lithium measured in earlier optical studies of WASP-18.
See also
*
SuperWASP
*
List of extrasolar planets
References
Phoenix (constellation)
Planetary transit variables
F-type subgiants
F-type main-sequence stars
Planetary systems with one confirmed planet
J01372503-4540404
18
10069
07562
0185
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