The XO Project is an international team of amateur and professional astronomers tasked with identifying extrasolar planets. They are led by Peter R. McCullough of the Space Telescope Science Institute.[1] It is primarily funded by NASA's Origins Program and the Director's Discretionary Fund of the Space Telescope Science Institute.[2][3]
Preliminary identification of possible star candidates starts at the Haleakala telescope in Hawaii by a team of professional astronomers. Once they identify a star that dims slightly from time to time (the transit method), the information is forwarded to a team of amateur astronomers who then investigate for additional evidence suggesting this dimming is caused by a transiting planet. Once enough data is collected, it is forwarded to the University of Texas McDonald Observatory to confirm the presence of a transiting planet by a second team of professional astronomers.[2]
McCullough and his team employed a relatively inexpensive telescope called the XO Telescope, made from commercial equipment, to search for extrasolar planets. The construction of the one-of-a-kind telescope cost $60,000 for the hardware, and much more than that for the associated software.[4] The telescope consists of two 200-millimeter telephoto camera lenses, and resembles binoculars in shape. It is similar to the TrES survey telescope. It stands on the summit of the Haleakalā volcano and 3,054 m (10,000 foot) in Hawaii.[1] Their first discovery of a Jupiter-sized planet orbiting a Sun-like star 600 light-years from Earth in the constellation Corona Borealis—XO-1b—was reported May 16, 2006 on Newswise.
In 2016 three similar double telescopes were operating, two in Spain and one in Utah.[5]
The XO telescope has discovered six objects so far, five are hot Jupiter planets and one, XO-3b, may be a brown dwarf.
| Star | Constellation | Right ascension |
Declination | App. mag. |
Distance (ly) | Spectral type |
Planet | Mass (MJ) |
Radius (RJ) |
Orbital period (d) |
Semimajor axis (AU) |
Orbital eccentricity |
Inclination (°) |
Discovery year |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| XO-1[6] | Corona Borealis | 16h02m12s | +28° 10′ 11″ | 11.319 | 600 | G1V | XO-1b | 0.9 | 1.3 | 3.941534 | 0.0488 | 0 | 87.7 | 2006 |
| XO-2N[7] | Lynx | 07h48m07s | +50° 13′ 33″ | 11.25 | 486 | K0V | XO-2Nb | 0.57 | 0.973 | 2.615838 | 0.0369 | 0 | 88.58 | 2007 |
| XO-3[8] | Camelopardalis | 04h21m53s | +57° 49′ 01″ | 9.91 | 850 | F5V | XO-3b | 11.79 | 1.217 | 3.1915239 | 0.0454 | 0.26 | 84.2 | 2007 |
| XO-4[9] | Lynx | 07h21m 33.1657s | +58° 16′ 05.005″ | 10.78 | 956 | F5V | XO-4b | 1.72 | 1.34 | 4.12502 | 0.0555 | 0.0024 | 88.7 | 2008 |
| XO-5[10] | Lynx | 07h46m 51.959s | +39° 05′ 40.47″ | 12.1 | 881 | G8V | XO-5b | 1.15 | 1.15 | 4.187732 | 0.0508 | 0.0029 | 86.8 | 2008 |
| XO-6[11] | Camelopardalis | 6h19m 10.31s | +73° 49′ 39.24″ | 10.28 | 760 | F5V | XO-6b | 4.4 | 2.07 | 3.76 | 0.082 | 0 | 86.0 | 2016 |
| XO-7 | Draco | 18h29m 52.30s | 85° 13′ 59.58″ | 10.52 | 763 | G0V | XO-7b | 0.71 | 1.373 | 2.8641424 | 0.04421 | 0.038 | 83.45 | 2019 |
A subset of XO light curves are available at the NASA Exoplanet Archive.
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