XO-1b

Extrasolar planet in the constellation Corona Borealis

XO-1b / Negoiu

Haleakala Observatory, Hawaii[1]
Discovery date	18 May 2006[2]
Detection method	Transit and Radial velocity[1]
Orbital characteristics
Semi-major axis	0.04930+0.00091 −0.00096 AU
Eccentricity	<0.019[3]
Orbital period (sidereal)	3.94150685±0.00000091[4] d
Inclination	88.8 ± 0.2[4]
Semi-amplitude	116 ± 9[1]
Star	XO-1
Physical characteristics
Mean radius	1.21 ± 0.03[4] RJ
Mass	0.913±0.038[3] MJ
Mean density	0.64 ± 0.05 g/cm3 (0.0231 ± 0.0018 lb/cu in)[4]
Surface gravity	15.8 ± 1.5 m/s2 (51.8 ± 4.9 ft/s2)[5]

XO-1b is an

away from Earth.

The planet XO-1b is named Negoiu. The name was selected in the NameExoWorlds campaign by Romania, during the 100th anniversary of the IAU. Negoiu is the second highest peak in Romania.^[6][7]

In 2006, the XO Project, an international team of professional and amateur astronomers, discovered a Jupiter-sized planet, later named XO-1b, orbiting a Sun-like star.^[1] The team, led by Peter R. McCullough of the Space Telescope Science Institute in Baltimore, had four amateur astronomers hailing from North America and Europe.^[8] An independent confirmation of the planet was made by the Wide Angle Search for Planets project later that same year.^[9]

The XO Project team employed the relatively inexpensive

From September 2003 to September 2005, the XO Telescope detected tens of thousands of bright stars. In that time, McCullough's team of amateur astronomers studied a few dozen stars they had previously identified as promising candidates for extrasolar planets. The star XO-1, in particular, was marked as a promising candidate in June 2005. The amateur astronomers observed it from June to July 2005, eventually confirming that a planet-sized object was eclipsing it. McCullough's team then turned to the McDonald Observatory in Texas for information on the object's mass and to confirm it was a planet.^[1]

Transit

McCullough's team found the planet by detecting slight reductions in the star's

of the star. The light from the star reduces by approximately two percent when XO-1b is in transit. Their observation revealed that XO-1b is in a tight, four-day orbit around its parent star.

While astronomers had detected more than

.

Secondary transits and phase curve of this planet have been observed.[11]

Radial velocity

The team confirmed the planet's existence by using the

's. This planet is much larger than its mass would suggest. McCullough has said, "Of the planets that pass in front of their stars, XO-1b is the most similar to Jupiter yet known, and the star XO-1 is the most similar to the Sun, but XO-1b is much, much closer to its star than Jupiter is to the Sun."

The technique used by the team to find XO-1b is an innovative method in that it uses a relatively inexpensive telescope to hunt for extrasolar planets. It, however, is limited primarily to planets orbiting close to their parent stars, and it only finds planets large enough to cause a measurable depression in starlight.

Physical characteristics

As a planet with a mass comparable to that of Jupiter in a close-orbit around its star, this planet falls into the category of hot Jupiters. Like other known transiting hot Jupiters such as HD 209458 b and TrES-1b, the low density of XO-1b indicates that this planet is a gas giant composed mainly of hydrogen and helium.

Observations with the NICMOS instrument on board the Hubble Space Telescope detected the presence of water vapor, methane, carbon dioxide, and possibly carbon monoxide in the atmosphere of XO-1b.^[11] However, an independent reinvestigation of the same data was unable to reproduce these results.^[12] Later studies by the Hubble Space Telescope detected water in the atmosphere of the exoplanet.^[13][14]

See also

• 51 Pegasi b
• HD 209458 b
• Hot Jupiter
• TrES-1b

References

External links

Media related to XO-1b at Wikimedia Commons

• "Astronomers Catch Planet By Unusual Means". SpaceDaily. 19 May 2006. Retrieved 29 June 2008.
• Ayiomamitis, Anthony (4 June 2009). "Astrophotography by Anthony Ayiomamitis". Retrieved 10 June 2009. (Amateur's observation using Differential Photometry)