HD 15082

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HD 15082
Observation data
Epoch J2000      Equinox J2000
Constellation Andromeda
Right ascension 02h 26m 51.05823s[1]
Declination +37° 33′ 01.7330″[1]
Apparent magnitude (V) 8.3[2]
Spectral type kA5 hA8 mF4[3]
Variable type δ Sct[2]
Proper motion (μ) RA: –1.26[1] mas/yr
Dec.: –9.22[1] mas/yr
Parallax (π) 8.65 ± 0.80[1] mas
Distance 380 ± 30 ly
(120 ± 10 pc)
Mass 1.55 ± 0.04[3] M
Surface gravity (log g) 4.3 ± 0.2[2] cgs
Temperature 7,400 ± 200[2] K
Metallicity [Fe/H] 0.1 ± 0.2[3] dex
Rotational velocity (v sin i) 86[2] km/s
Age 100[4] Myr
Other designations
BD+36 489, HD 15082, HIP 11397, WASP-33.

HD 15082 (also known as WASP-33) is a star located roughly 378 light years away[3] in the northern constellation of Andromeda.[5] The star is a Delta Scuti variable and a planetary transit variable. It is the first Delta Scuti variable known to host a planet.[6] A hot Jupiter type extrasolar planet orbits this star with an orbital period of 1.22 days.

In common with many rapidly rotating stars of spectral type A, the stellar classification of HD 15082 is more challenging to discern. The hydrogen lines and effective temperature of the star are similar to spectral type A8, however the calcium II K line resembles that of an A5 star, and the metallic lines are more similar to an F4 star. The spectral type is thus written kA5 hA8 mF4.[3] This suggests that HD 15082 is an Am star.[3]

It orbits so close to its star that its surface temperature is about 5,800°C (10,472°F). It is the hottest planet ever observed in the Universe.[7]


In 2010, the SuperWASP project announced the discovery of an extrasolar planet, designated HD 15082 b, orbiting the star. The discovery was made by detecting the transit of the planet as it passes in front of its star, an event which occurs every 1.22 days. As the planet crosses the star's disc, it causes the rotational broadening signature in the star's spectrum to change, enabling the determination of the sky-projected angle between the star's equator and the orbital plane of the planet to be determined. (This differs from the Rossiter-McLaughlin effect which is observed for radial velocity measurements). For HD 15082 b, this angle is about 250 degrees, indicating that it is in a retrograde orbit. Limits from radial velocity measurements imply it has less than 4.1 times the mass of Jupiter.[3]

The HD 15082 planetary system[3][note 1]
(in order from star)
Mass Semimajor axis
Orbital period
Eccentricity Inclination Radius
b < 4.59 MJ 0.02558 (± 0.00023) 1.21986967 (± 4.5e-07) 0 87.67° 1.438 RJ

Non-Keplerian features of motion for HD 15082 b[edit]

In view of the high rotational speed of its parent star, the orbital motion of HD 15082 b may be affected in a measurable way by non-Keplerian effects like, e.g., the huge oblateness of the star and the general relativistic gravitomagnetic field. More precisely, the gravitational field of the distorted star is different from that coming from the usual Newtonian inverse-square law. The same holds also for the terms arising from general relativity, yielding the well-known frame-dragging precession. As a consequence, the orbital trajectory of HD 15082 b is shifted with respect to the purely Keplerian ellipse.


  1. ^ Parameters from the photometric + radial velocity solution in table 3 of Cameron et al. (2010). Different analysis methods result in slightly different parameters, see Cameron et al. (2010) for details.


  1. ^ a b c d e van Leeuwen, F. (November 2007), "Validation of the new Hipparcos reduction", Astronomy and Astrophysics 474 (2): 653–664, arXiv:0708.1752, Bibcode:2007A&A...474..653V, doi:10.1051/0004-6361:20078357 
  2. ^ a b c d e Herrero, E. et al. (February 2011), "WASP-33: the first δ Scuti exoplanet host star", Astronomy and Astrophysics 526: L10, arXiv:1010.1173, Bibcode:2011A&A...526L..10H, doi:10.1051/0004-6361/201015875 
  3. ^ a b c d e f g h Collier Cameron, A. et al. (2010). "Line-profile tomography of exoplanet transits - II. A gas-giant planet transiting a rapidly rotating A5 star". Monthly Notices of the Royal Astronomical Society 407: 507. arXiv:1004.4551. Bibcode:2010MNRAS.407..507C. doi:10.1111/j.1365-2966.2010.16922.x. 
  4. ^ Moya, A. et al. (November 2011), "High spatial resolution imaging of the star with a transiting planet WASP-33", Astronomy & Astrophysics 535: A110, arXiv:1110.3160, Bibcode:2011A&A...535A.110M, doi:10.1051/0004-6361/201116889 
  5. ^ "WASP-33 b". ETD - Exoplanet Transit Database. Retrieved 2010-04-28. 
  6. ^ "Discovery Of A Pulsating Star That Hosts A Giant Planet", Science Daily, January 19, 2011 
  7. ^ How the Universe Works 3. Jupiter: Destroyer or Savior?. Discovery Channel. 2014.