Two Hot Jupiters found to be in triple star systems.

The discovery of a large number of Hot Jupiter type planets (large gas giant planets orbiting very close to their parent stars) in recent years has challenged out theories of stellar system formation. In theory gas giant type planets should only be able to form in the outer parts of a star system, beyond the 'snow line' where ice particles can accumulate within a protoplanetary disk. Since such planets could not form close to the stars, it was originally theorized that they must have formed in the outer part of the stellar system and then spiraled inwards for some reason. However this should lead to planets that still orbited in the plane on which the star rotated (plane of the stellar system), whereas many such planets seem to have orbits quite strongly tilted with regard to this plane. This has led to the development of two further theories, firstly that such systems could come about due to disruption of protoplanetary disks by strong magnetic fields from the host star, and the presence of undetected companion stars in the system, able to disrupt protoplanetary disks through gravitational torque.

In a paper published on the arXiv database at Cornell University Library on 30 March 2014, a team of scientists led by Eric Bechter of the Department of Physics at the University of Notre Dame describe the first results of the 'Friends of Hot Jupiters' program, which aims to systematically search for undetected companions to stars with known Hot Jupiters, with an emphasis on looking for dim Red Dwarfs (stars with masses less than 40% of that of the Sun) or Brown Dwarfs (which mass to fuse hydrogen in their cores like true stars, but are massive enough to fuse deuterium) detectable at infrared wavelengths.

Bechter et al. report the existence of new companion stars in two systems; WASP-12 and HAT-P-8, both of which were already known to be binary systems, with remote Red Dwarf companions orbiting the primary star. Both were directly imaged using the Keck II AO system at the W.M. Keck Observatory on Mauna Kea, Hawaii.

The Wasp-12 system was discovered in 2009. The primary star, WASP-12A, is a yellow dwarf star slightly larger than the Sun, roughly 800 light years from Earth in the constellation of Auriga. This is orbited by a planet, WASP-12b (when naming objects in other star systems stars are identified with upper case letters and planets lower case letters) with about 1.41 times the mass of Jupiter orbiting every 1.09 days at a distance of 0.0229 AU (2.29% of the distance at which the Earth orbits the Sun), this planet having an orbit tilted 59° to the plane of rotation of WASP-12A. In 2011 a second star was detected in the WASP-12 system, a red dwarf with approximately 38% of the Sun's mass named WASP-12B.  

Betcher et al. report closer examination of this companion star reveals that it also has a smaller companion, named WASP-12C, a red dwarf with 37% of the Sun's mass. These two stars orbit one-another at a distance of 21 AU.

Keck AO discovery image of WASP-12 B,C taken on 2 February 2012. North is up and east is left (east is reversed in astronomical images compared to standard maps, as the observer is looking up not down). Follow up observations separated by more than one year recovered the companion. Betcher et al. (2014).

The HAT-P-8 system was discovered in 2008. Its primary star, HAT-P-8A, is an F-type yellow-white dwarf star with roughly 1.28 times the mass of our Sun 750 light years from Earth in the constellation Pegasus. This is orbited every 3.08 days by a planet, HAT-P-8b with a mass 1.52 times as large as Jupiter at a distance of 0.487 AU (4.87% of the distance between the Earth and the Sun), the orbit of this planet being at 15° to the plane of the star's rotation. This system was found to have a companion star, HAT-P-8B, in 2011, this being an M-type red dwarf star with a mass 22% that of the Sun's.

Betcher et al. report the discovery of a third star in the system, HAT-P-8C, a smaller red dwarf with roughly 18% of the Sun's mass. This orbits HAT-P-8B at a distance of about 15 AU.

Keck AO discovery images of HAT-P-8 B,C taken on UT 24 June 2012. North is up and east is left. Follow up observations separated by more than one year recover the companion. Betcher et al. (2014).

See also...

 Kepler 63b; a giant planet in a polar orbit.

KIC 11554435 (or Kepler Input Catalogue 11554435) is a young, sunlike star 652 light years from the Earth. It is thought to be between 200 and 300 million years old with a mass 98% of the Sun's and an effective surface temperature of ~5576 K, as opposed to 5778 K for the Sun. As a young star it rotates considerably faster than the Sun, roughly once every 5.4 days, while the Sun takes slightly under 24.5 days to complete a rotation, and has a high level of starspot activity (the same as sunspot activity but on a different star).

 The atmosphere of Wasp 12b.

Wasp-12b is a super-Jovian Hot Jupiter type planet (a planet larger than Jupiter orbiting very close to its parent star) 871 light years from Earth in the constellation of Auriga. It orbits Wasp-12A, a G-type yellow dwarf star slightly bigger and hotter than our sun (1.35 × the Sun's mass, with a surface temperature of 6300 K, as opposed...

 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...

Follow Sciency Thoughts on Facebook.

Sunset on Osiris.

'Osiris' is an informal name given to the planet HD 209458b, the first transiting exoplanet (planet in another solar system, detected as its orbit regularly brings it in front of its star when seen from Earth), discovered by the European Space Agency's Hippacaros Satellite in 1999, when press interest in exoplanets still warranted their being given names rather than just numbers. It is a Hot Jupiter type planet, with a mass 69% of that of Jupiter and a volume 250% of Jupiter's (the lower mass of the planet makes for less gravity to pull it into a tighter ball, and the higher temperature also makes the planet expand, leading to a planet with a smaller mass but a larger volume than Jupiter) orbiting a sun-like star 150 light years from Earth in the constellation of Pegasus. The planet orbits the star at a distance of 0.044 AU; 4.4% of the distance between the Earth and the Sun, or 12.5% of the distance at which Mercury orbits the sun. It has a year of only 84 hours.

Later studies by the Spitzer Space Telescope, and the Very Large Telescope revealed the planet to have a circular orbit, a surface temperature of at least 750 °C, and an atmosphere rich in Carbon Monoxide (CO) with clouds of silica dust (SiO₂), and superstorms with winds reaching 7000 km/h.

In 2008 a team lead by David Sing of the Institute d'Astrophysique de Paris at Université Pierre et Marie Curie was able to create a complete optical spectrum for the planet, using data gathered by the Hubble Space Telescope, their results being published in a paper in the Astrophysical Journal. Sing et al. found sodium and hydrogen ions (Na⁺ and H⁺) as well as Vanadium and Titanium Oxides. They also found that the planets atmosphere has a temperature inversion and distinct troposphere and stratosphere, as on Earth. They calculated that the atmospheric temperature at the bottom of the atmosphere would be around 1700 °C, falling to about 500 °C at the top of the troposphere, then rising again slowly in the stratosphere. They calculated that this could led to clouds of liquid sodium at the top of the troposphere, leading to sodium 'rain' that would evaporate in the hotter lower troposphere to rise up and recondense in the cloudy layer.

On 6 January 2012, Frédéric Pont of the University of Exeter published an image of a sunset on Osiris on the ExoClimes Website based upon the Hubble spectrographic data. This has a strange, greenish tinge to it, due to the absorption of light in the orange part of the spectrum by the gaseous sodium. Pont acknowledges that this image was influenced by an earlier video of a sunset on Osiris that appeared on the Instítut national des sciences de l'univers website in 2008, and may also have been influenced by the fact that David Sing now works at Exeter.

Pont's image of a sunset on Osiris.

Pont also produced an image of a sunset on HD 189733b, another Hot Jupiter type planet with a well studied atmosphere. HD 189733b lies in a binary system 63 light years from Earth in the constellation of Vulpecula. The planet orbits close to the system's primary star (HD 189733A), an orange dwarf with 82% of the mass of the sun, a radius 75% of the suns and 26% of its luminosity. A second star, a dim red dwarf (HD 189733B) orbits every 2300 years at a distance of 216 AU (i.e. 216 times the distance at which the Earth orbits the Sun, or seven times the distance at which Neptune orbits the Sun). HD 189733b is only 0.03 AU from HD 189733A (3% of the distance between the Earth and the Sun), and is slowly boiling away into space as a consequence. It orbits the star once every 53 hours. Sodium, Potasium and Carbon Dioxide have been found in its atmosphere, which is thought to lack an inversion layer and distinct stratosphere and troposphere, due to the extreme heating caused by the close-by star. None of this appears to be visible in the sunset picture,

Pont's image of a sunset on HD 189733b.

See also A fresh look at Wasp-43b, A planet disintegrating in the heat of its own sun, Wasp-19b: a highly irradiated Hot Jupiter, The atmosphere of GJ1214b and Exoplanets on Sciency Thoughts YouTube.