XO-3b
Encyclopedia
XO-3b is an exoplanet with about 11.79 times the mass of Jupiter
, and an orbit around its parent star
in about 3.2 days. The radius of this object is 1.217 times that of Jupiter. Astronomers announced their discovery on May 30, 2007, at the American Astronomical Society
in Honolulu, Hawaii
. Its discovery is attributed to the combined effort of amateur and professional astronomers working together on the XO Project
using a telescope
located on the Haleakala summit in Hawaii.
Dubbed an "oddball" planet, the planet stands out from over 350 other extrasolar planets as the most massive planet found in close proximity to a star, yet the orbit is significantly elliptical instead of circular, as would be expected. It is also considered a transiting planet, passing in front of its parent star during each orbit. It is the third such planet to be found by the XO Project which was specifically created to locate them.
allow a determination of the angle between the planet's orbital plane and the equator of the parent star. Initial reports suggested this angle was very large, at 70 ± 15 degrees, which is significantly larger than that of the other transiting planets for which this measurement has been made. The authors cautioned that systematic
effects may have affected the measurements, and a later determination by an independent group of astronomers determined a reduced value of 37.3 ± 3.7 degrees. This value is however still larger than the misalignment between the Sun's equator and the orbital plane of Jupiter, which is only 6°. The misalignment may indicate that in the past an encounter with another planet altered its orbit, kicking it out of the plane of the planetary system. Another planetary system that may have also undergone such planet-planet interactions is Upsilon Andromedae
.
or a brown dwarf
. One of the leading astronomers in this discussion is Christopher Johns-Krull, who indicated that the debate is still quite lively. This is not particularly unusual or strange, as it would not be the first of many brown dwarfs orbiting mother stars.
The light curve that better match the steepness of ingress and egress implies a planetary radius of 1.32 ± 0.15 RJ and a mass of 11.71 ± 0.46 MJ.
Jupiter
Jupiter is the fifth planet from the Sun and the largest planet within the Solar System. It is a gas giant with mass one-thousandth that of the Sun but is two and a half times the mass of all the other planets in our Solar System combined. Jupiter is classified as a gas giant along with Saturn,...
, and an orbit around its parent star
Star
A star is a massive, luminous sphere of plasma held together by gravity. At the end of its lifetime, a star can also contain a proportion of degenerate matter. The nearest star to Earth is the Sun, which is the source of most of the energy on Earth...
in about 3.2 days. The radius of this object is 1.217 times that of Jupiter. Astronomers announced their discovery on May 30, 2007, at the American Astronomical Society
American Astronomical Society
The American Astronomical Society is an American society of professional astronomers and other interested individuals, headquartered in Washington, DC...
in Honolulu, Hawaii
Honolulu, Hawaii
Honolulu is the capital and the most populous city of the U.S. state of Hawaii. Honolulu is the southernmost major U.S. city. Although the name "Honolulu" refers to the urban area on the southeastern shore of the island of Oahu, the city and county government are consolidated as the City and...
. Its discovery is attributed to the combined effort of amateur and professional astronomers working together on the XO Project
XO Project
The XO Project is an international team of amateur and professional astronomers tasked with identifying extrasolar planets. They are led by Peter McCullough of the Space Telescope Science Institute...
using a telescope
Telescope
A telescope is an instrument that aids in the observation of remote objects by collecting electromagnetic radiation . The first known practical telescopes were invented in the Netherlands at the beginning of the 1600s , using glass lenses...
located on the Haleakala summit in Hawaii.
Dubbed an "oddball" planet, the planet stands out from over 350 other extrasolar planets as the most massive planet found in close proximity to a star, yet the orbit is significantly elliptical instead of circular, as would be expected. It is also considered a transiting planet, passing in front of its parent star during each orbit. It is the third such planet to be found by the XO Project which was specifically created to locate them.
Orbital inclination
Measurements of the Rossiter-McLaughlin effectRossiter-McLaughlin effect
The Rossiter–McLaughlin effect is a spectroscopic phenomenon observed when either an eclipsing binary's secondary star or an extrasolar planet is seen to transit across the face of the primary or parent star. As the main star rotates on its axis, one quadrant of its photosphere will be seen to be...
allow a determination of the angle between the planet's orbital plane and the equator of the parent star. Initial reports suggested this angle was very large, at 70 ± 15 degrees, which is significantly larger than that of the other transiting planets for which this measurement has been made. The authors cautioned that systematic
Systematic error
Systematic errors are biases in measurement which lead to the situation where the mean of many separate measurements differs significantly from the actual value of the measured attribute. All measurements are prone to systematic errors, often of several different types...
effects may have affected the measurements, and a later determination by an independent group of astronomers determined a reduced value of 37.3 ± 3.7 degrees. This value is however still larger than the misalignment between the Sun's equator and the orbital plane of Jupiter, which is only 6°. The misalignment may indicate that in the past an encounter with another planet altered its orbit, kicking it out of the plane of the planetary system. Another planetary system that may have also undergone such planet-planet interactions is Upsilon Andromedae
Upsilon Andromedae
Upsilon Andromedae is a binary star located approximately 44 light-years away from Earth in the constellation Andromeda. The primary star is a yellow-white dwarf star that is somewhat younger than the Sun...
.
Debate
There is currently a debate over the classification of this object as either a planetPlanet
A planet is a celestial body orbiting a star or stellar remnant that is massive enough to be rounded by its own gravity, is not massive enough to cause thermonuclear fusion, and has cleared its neighbouring region of planetesimals.The term planet is ancient, with ties to history, science,...
or a brown dwarf
Brown dwarf
Brown dwarfs are sub-stellar objects which are too low in mass to sustain hydrogen-1 fusion reactions in their cores, which is characteristic of stars on the main sequence. Brown dwarfs have fully convective surfaces and interiors, with no chemical differentiation by depth...
. One of the leading astronomers in this discussion is Christopher Johns-Krull, who indicated that the debate is still quite lively. This is not particularly unusual or strange, as it would not be the first of many brown dwarfs orbiting mother stars.
The light curve that better match the steepness of ingress and egress implies a planetary radius of 1.32 ± 0.15 RJ and a mass of 11.71 ± 0.46 MJ.