HD 240237 b

HD 240237 b
Exoplanet List of exoplanets

Artist's impression of HD 240237 b (foreground) orbiting its host star (bottom). The stellar corona can be seen emitting from the surface.
Parent star
Star HD 240237 (BD+57° 2714)
Constellation Cassiopeia
Right ascension (α) 23h 15m 42.22361s
Declination (δ) +58° 02′ 35.6654″
Apparent magnitude (mV) 8.19
Distance4,900 ly
(1,500[1] pc)
Spectral type K2III[2]
Mass (m) 1.69 (± 0.42)[2] M☉
Radius (r) 32 (± 1)[2] R☉
Temperature (T) 4361 (± 10)[2] K
Metallicity [Fe/H] −0.26 (± 0.07)[2]
Age ~2 Gyr
Physical characteristics
Mass(m)5.3[2] MJ
Radius(r)~1.11 RJ
Stellar flux(F⊙)100.4[3] ⊕
Temperature (T) 781 K (508 °C; 946 °F)
Orbital elements
Semi-major axis(a) 1.9 AU
Eccentricity (e) 0.4 (± 0.1)
Orbital period(P) 745.7 (± 13.8) d
Argument of
periastron		 (ω) 108.1 ± 21.8°
Time of periastron (T0) 54,292 ± 28.3 JD
Semi-amplitude (K) 91.5 ± 12.8 m/s
Discovery information
Discovery date 9 October 2011
Discoverer(s)
Discovery method Doppler spectroscopy
Discovery status Confirmed
Database references
Extrasolar Planets
Encyclopaedia		data
SIMBADdata
Exoplanet Archivedata
Open Exoplanet Cataloguedata

HD 240237 b is a super-Jupiter exoplanet orbiting the K-type giant star HD 240237 about 4,900 light-years (1,500 parsecs, or nearly 4.6×1016 km) away from Earth in the constellation Cassiopeia. It orbits outside of the habitable zone of its star at a distance of 1.9 AU. The exoplanet was found by using the radial velocity method, from radial-velocity measurements via observation of Doppler shifts in the spectrum of the planet's parent star. The planet has a mildly eccentric orbit.

Characteristics

Mass, radius and temperature

HD 240237 b is a "super-Jupiter", an exoplanet that has a radius and mass larger than that of the gas giants Jupiter and Saturn. It has a temperature of 781 K (508 °C; 946 °F), around that of the surface temperature of Venus.[3] It has an estimated mass of around 5.3 MJ and a potential radius of around 9% larger than Jupiter (1.11 RJ, or 12.2 R⊕) based on its mass, since it is more massive than the jovian planet.

Host star

The planet orbits a (K-type) giant star named HD 240237. It has exhausted the hydrogen supply in its core and is currently fusing helium. The star has a mass of 1.69 M☉ and a radius of around 32 R☉. It has a surface temperature of 4361K and is likely 2 billion years old based on its mass and evolution. In comparison, the Sun is about 4.6 billion years old[4] and has a surface temperature of 5778 K.[5]

The star's apparent magnitude, or how bright it appears from Earth's perspective, is 8.19. Therefore, HD 240237 is too dim to be seen with the naked eye.

Orbit

HD 240237 b orbits its star with nearly 331 times the Sun's luminosity (331 L☉) every 746 days at a distance of 1.9 AU (compared to Mars' orbital distance from the Sun, which is 1.52 AU). It has a mildly eccentric orbit, with an eccentricity of 0.4.

Discovery

The planet was detected through Doppler spectroscopy, the method of observing exoplanets through the measurement of radial velocities of a star. If there is a wobble, it could mean that there is a possible planetary companion orbiting it.

Observations were taken with the Hobby-Eberly Telescope equipped with the High-Resolution Spectrograph in a queue-scheduled mode.[2] From July 2004 to October 2009, 40 epochs were measured, with SNR values ranging from 161–450. These observations eventually led the team to conclude that there was in fact a planetary companion orbiting around HD 240237, and they estimated its parameters to be a mass of 5.3 times that of Jupiter, an orbital period of 746 days, an eccentricity of 0.4, and a semi-major axis of 1.9 AU. The discovery, along with 2 other exoplanets, were announced on October 9, 2011.[2]

See also

References

  1. ↑ "Notes for planet HD 240237 b". The Extrasolar Planets Encyclopaedia. Retrieved 2016-07-29.
  2. 1 2 3 4 5 6 7 8 Gettel, S.; Wolszczan, A.; Niedzielski, A.; Nowak, G.; Adamów, M.; Zieliński, P.; Maciejewski, G. (2011). "Substellar-Mass Companions to the K-Giants HD 240237, BD +48 738 and HD 96127". The Astrophysical Journal. 745: 28. arXiv:1110.1641. Bibcode:2012ApJ...745...28G. doi:10.1088/0004-637X/745/1/28.
  3. 1 2 http://www.hpcf.upr.edu/~abel/phl/hec_plots/hec_orbit/hec_orbit_HD_240237_b.png
  4. ↑ Fraser Cain (16 September 2008). "How Old is the Sun?". Universe Today. Retrieved 2011-02-19.
  5. ↑ Fraser Cain (September 15, 2008). "Temperature of the Sun". Universe Today. Retrieved 2011-02-19.
  • "Notes for planet HD 240237 b". The Extrasolar Planets Encyclopaedia. Retrieved 2016-07-29.

Coordinates: 23h 15m 42.22361s, +58° 02′ 35.6654″

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