Friday, 7 September 2012

The HATNet project announces the discovery of three new Hot Jupiter type planets.

The HATNet (Hungarian made Automated Telescope Network) project uses eight small (11 cm diameter lens) telescopes located at the  Fred Lawrence Whipple Observatory in Arizona and the Mauna Kea Observatory in Hawaii, to search for exoplanets. Such Earth-based networks are playing an increasingly important role in the search for exoplanets, since while they do not discover the shear number of planets that the space-based telescopes find, the planets they do discover tend to be more amicable to follow-up observations by Earth-based observatories.

In a paper published on the online arXiv database at the Cornell University Library on 13 July 2012, a team of scientists led by Joel Hartman of the Department of Astrophysical Sciences at Princeton University, announce the discovery of three new Hot-Jupiter type planets by the HATNet project. All three planets have been observed both by the light they occlude when they pass in front of their host stars, and by the movement they cause in the star as they orbit about it. This enables scientists to estimate both the volume and the mass of the planets, revealing that all of the planets have lower masses, but higher volumes than Jupiter, which matches predictions that gaseous planets close to stars will expand due to the heat of the star.

The first new planet obits the star GSC 1364-01424; this is the 39th star found to have a planet by HATNet, and the system is therefore renamed HAT-P-39, with the star being HAT-P-39A and the planet HAT-P-39b (naming conventions dictate that stars are given upper case letters and planets lower case letters. 

HAT-P-39A is about 2094 light years from Earth in the constellation of Gemini. It is an F-class star, slightly larger and hotter than our Sun, with a mass 1.4 times the Sun's and a radius 1.6 times the Sun's. It's effective surface temperature is 6430 K, compared to 5778 K for our Sun. The star is thought to be about 2 billion years old.

HAT-P-39b orbits this star at a distance of 0.0509 AU (that is to say 5.09% of the distance at which the Earth orbits the Sun), completing one orbit every 3.54 days (85 hours). It has a mass equivalent to 0.599 times that of Jupiter, but a radius 1.57 times Jupiter's. It is thought to have an average equatorial temperature of 1752 K, compared to 303 K for Earth or 152 K for Jupiter.

Diagram showing the mass of HAT-P-39b compared to the planets of out Solar System. Visual Exoplanet Catalogue.

The second new planet orbits the star GSC 3607-01028, now renamed HAT-P-40A, another F-class star, 1634 light years from Earth in the constellation of Lacerta. HAT-P-40A has a mass 1.5 times that of the Sun, and 2.2 times the Sun's radius. Its effective surface temperature is 6080 K, and it is thought to be about 2.7 billion years old.

HAT-P-40b orbits this star at a distance of 0.0608 AU (6.08% of the distance at which the Earth orbits the Sun), taking 4.46 days (107 hours) to complete one circuit about the star. I has 0.615 times the mass of Jupiter, and 1.73 times the radius. Its average equatorial temperature is 1770 K.

Diagram showing the comparative masses of HAT-P-40b and the planets of our Solar System. Visual Exoplanet Catalogue.

The final new planet orbits GSC 0488-02442, now renamed HAT-P-41A, another F-class star, this one  1014 light years away in the constellation of Aquila. HAT-P-41 A has 1.42 times the Sun's mass and 1.68 times the Sun's radius. It has an effective surface temperature of 6390 K, and is thought to be 1.5 billion years old.

H-band AO image of HAT-P-41. Hartman et al. (2012).

The planet HAT-P-41b orbits this star every 2.69 days (65 hours) at a distance of 0.0424 AU (4.24% of the distance between the Earth and the Sun). It has 0.8 times he mass of Jupiter and 1.68 times Jupiter's radius. It's average equatorial temperature is thought to be 1941 K.

Diagram showing the comparative masses of HAT-P-41b and the planets of our Solar System. Visual Exoplanet Catalogue.

See also A fourth body in the KOI-13 systemTwo Hot Jupiters found in the Beehive ClusterA new study of the Kepler 11 planetary systemThe object orbiting GD66 is probably a planet, not a Brown Dwarf and Exoplanets on Sciency Thoughts YouTube.

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