HAT-P-2 System

Exoplanetary Scratchpad [SysBP Img]

Hat-P-2b (aka HD 147506b) is the most massive measured exoplanet discovered that is clearly not a Brown Dwarf and the first transiting Hot Super Planet discovered. It is the first known transiting planet with a significantly eccentric orbit (2.8 to 9.3 million miles) and experiences significant seasons. It briefly held the record of furthest out transiting planet. It takes about a day to heat up and 4-5 days to cool down. Spitzer can measure different depths with different infrared wavelengths. Its temperature was mapped out. Its daytime is as high as 2400K, while its night is 1200K. It would have winds blowing thousands of miles per hour.

HD Hat-P-2 System Web Pages

• Wikipedia
• Extrasolar Planet Encyclopedia

HD Hat-P-2 System In the News

Massive Planet Discovered (2007)

http://www.arxiv.org/abs/0705.0126
HAT-P-2b: A Super-Massive Planet in an Eccentric Orbit - Extrasolar Visions BBS Thread
http://dsc.discovery.com/news/2007/05/07/fatplanet_spa_zoom0.html?category=space&guid=20070507093000 HAT-P-2b: ‘A Really Weird Planet’ - Centauri Dreams BLOG
http://www.cfa.harvard.edu/press/2007/pr200711.html
http://news.nationalgeographic.com/news/2007/05/070503-new-planet.html

Atmosphere Modelled (2007)

http://oklo.org/?p=210

Parameters Refined (Jun 2007)

http://www.arxiv.org/abs/0707.0679

Temperature Mapped (May 2013)

• http://science.nasa.gov/science-news/science-at-nasa/2013/24may_hotjupiters/ - includes video
• http://www.sen.com/news/spitzer-puts-exoplanets-in-the-lab.html
• http://news.discovery.com/space/alien-life-exoplanets/astronomers-capture-exoplanet-prods-it-in-the-lab-130506.htm

System Factoids

• 440 light years away
• Hot star with one or two planets
• In the constellation Hercules
• 4th brightest star that has a transiting planet
• Visual Magnitude of 8.7, visible in small 3 inch telescopes
• 2.7 Giga years old
• Almost twice as large as the Sun (1.8 RS)
• Mass is 1.3 MS.

Hat-P-2 Star Factoids

• Star is also known as HD 147506.
• A hot White Main Sequence Star (F8 V)
• Almost twice as big as the Sun.

Planet b Factoids

• Planet so unusual that its discoverers at first thought it was a false alarm.

Physical Characteristics

• The most massive measured planet discovered so far.
• Nicknamed "the heavyweight champion of extrasolar planets".
• When first discovered, it was thought its Mass was 8.17 MJ and Radius 1.18RJ.
• When first discovered, it was believed its density was as great as a terrestrial planet (6.6 gcm^-3, even though it is likely made up of hydrogen and helium.
• Updated measurements give it Mass of 8.64 Jupiter, radius of 0.954, and an even higher density of 12.41 g cm^-3.
• Density is now between that of a typical hot jupiter (1 g cm^-3) and low mass star (50 g cm^-3).
• Updated surface gravity is 227 m s^-1.
• Its measurements conform to current theory
• The first discovered transiting planet that is not a Hot Jupiter. This is much larger and denser than a Jupiter class planet.
• If it had 50% more mass, it would start limited fusion and be a Brown Dwarf.
• Has greatest surface gravity of any measured planet, 14 time's Earth's.
• Per earlier measurements, a 150 pound person would weigh 2100 pounds on its cloud tops.
• Per earlier measurements Surface gravity is 5 times that of any other transiting exoplanet.

Orbit Characteristics

• If Earth's orbit was as eccentric, it would extend from Mercury to Mars.
• Orbits in an eccentric orbit near its star (e = 0.5).
• No other known planet is as close in with such a high eccentricity (all other transiting planets are rather circular).
• Its short period of 5.63 days is actually the longest of all known transiting planets and its transits last longer than any other.
• Ranges from 0.03 AU to 0.1 AU (a = 0.06 AU)
• The difference in heat it receives from its star is 9 times from periastron to apastron.
• Temperatures range from 1000 C to 2000 C.

Hypothetical Outer Planet

• An outer planet could explain the great eccentricity of planet b
• There is no other evidense supporting or refuting this planet's existance

See Also

• Aliases: HAT-P-2 System, HD 147506 System
• Transiting Planets, HAT-P Planets, Bright Stars With Transiting Planets
• HD 189733 System (The first planet with a temperature map made this way)