HAT-P-1b
| Exoplanet | List of exoplanets | |
|---|---|---|
 |
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| Parent star | ||
| Star | HAT-P-1 (ADS 16402 B) | |
| Constellation | Lacerta | |
| Right ascension | (α) | 22h 57m 46.844s |
| Declination | (δ) | +38° 40′ 30.33″ |
| Distance | 450+72 −62 ly (139 +22 −19 pc) |
|
| Spectral type | G0V | |
| Orbital elements | ||
| Semi-major axis | (a) | 0.05561 ± 0.00083AU |
| Eccentricity | (e) | <0.067 |
| Orbital period | (P) | 4.4652968 ± 0.0000018d |
| Inclination | (i) | 85.634 ± 0.056° |
| Time of transit | (Tt) | 2,453,979.93165 ± 0.00025JD |
| Semi-amplitude | (K) | 59.3 ± 1.4m/s |
| Physical characteristics | ||
| Mass | (m) | 0.529 ± 0.020MJ |
| Radius | (r) | 1.319 ± 0.019RJ |
| Temperature | (T) | 1322 ± 15 |
| Discovery information | ||
| Discovery date | Thurs, Sept 14, 2006 | |
| Discoverer(s) | HATNet Project | |
| Discovery method | Transit, radial velocity | |
| Discovery site | Arizona and Hawaii | |
| Discovery status | Published | |
HAT-P-1b is an extrasolar planet orbiting the Sun-like star HAT-P-1, also known as ADS 16402 B. HAT-P-1 is the dimmer component of the ADS 16402 binary star system. It is located roughly 450 light years away from Earth in the constellation Lacerta. HAT-P-1b is among the least dense of any of the known extrasolar planets.
HAT-P-1b was detected by searching for astronomical transits of the parent star by orbiting planets. As the planet passes in front of its parent star (as seen from Earth), it blocks a small amount of the light reaching us from the star. HAT-P-1b was first detected by a dip of 0.6% in the light from the star. This enabled determination of the planet's radius and orbital period. The discovery was made by the HATNet Project (Hungarian Automated Telescope Network) using telescopes in Arizona and Hawaii and announced on September 14, 2006.
HAT-P-1b is located in a very close orbit to its star, taking only 4.47 days to complete. It therefore falls into the category of hot Jupiters. At only 8.27 million kilometers from the star, tidal forces would circularise the orbit unless another perturbing body exists in the system. At the present time, the existing measurements are not sufficient to determine the orbital eccentricity, so a perfectly circular orbit has been assumed by the discoverers. However, the eccentricity of the planet was calculated to be no greater than 0.067.
In order to determine the mass of the planet, measurements of the star's radial velocity variations were made by the N2K Consortium. This was done by observing the Doppler shift in the star's spectrum. Combined with the known inclination of the orbit as determined by the transit observations, this revealed the mass of the planet to be 0.53±0.04 times that of Jupiter.
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