HR8799
 HR 8799 (center) with HR 8799e (right), HR 8799d (lower right), HR 8799c (upper right), HR 8799b (upper left) from W. M. Keck Observatory |
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| Observation data Epoch J2000.0 Equinox J2000.0 (ICRS) |
|
|---|---|
| Constellation | Pegasus |
| Right ascension | 23h 07m 28.7150s |
| Declination | +21° 08′ 03.302″ |
| Apparent magnitude (V) | 5.964 |
| Characteristics | |
| Spectral type | kA5 hF0 mA5 V; λ Boo |
| U−B color index | −0.04 |
| B−V color index | 0.234 |
| Variable type | Gamma Doradus variable |
| Astrometry | |
| Radial velocity (Rv) | −11.5±2 km/s |
| Proper motion (μ) |
RA: 107.93±0.60 mas/yr Dec.: −49.63±0.46 mas/yr |
| Parallax (π) | 25.38 ± 0.70mas |
| Distance | 129 ± 4 ly (39 ± 1 pc) |
| Absolute magnitude (MV) | 2.98±0.08 |
| Details | |
| Mass | 1.47±0.30 M☉ |
| Radius | 1.34±0.05 R☉ |
| Luminosity (bolometric) | 4.92±0.41 L☉ |
| Surface gravity (log g) | 4.35±0.05 cgs |
| Temperature | 7430±75 K |
| Metallicity [Fe/H] | −0.47±0.10 dex |
| Rotational velocity (v sin i) | 37.5±2 km/s |
| Age |
30+20 −10 million years |
| Other designations | |
| Database references | |
| SIMBAD | data |
| Exoplanet Archive | data |
| Extrasolar Planets Encyclopaedia |
data |
HR 8799 is a roughly 30 million-year-old main-sequence star located 129 light years (39 parsecs) away from Earth in the constellation of Pegasus. It has roughly 1.5 times the Sun's mass and 4.9 times its luminosity. It is part of a system that also contains a debris disk and at least four massive planets. Those planets, along with Fomalhaut b, were the first extrasolar planets whose orbital motion was confirmed via direct imaging. The designation HR 8799 is the star's identifier in the Bright Star Catalogue. The star is a Gamma Doradus variable: its luminosity changes because of non-radial pulsations of its surface. The star is also classified as a Lambda Boötis star, which means its surface layers are depleted in iron peak elements. This may be due to the accretion of metal-poor circumstellar gas. It is the only known star which is simultaneously a Gamma Doradus variable, a Lambda Boötis type, and a Vega-like star (a star with excess infrared emission caused by a circumstellar disk).
The star HR 8799 is a member of the Lambda Boötis (λ Boo) class, a group of peculiar stars with an unusual lack of metals—elements heavier than hydrogen and helium—in their upper atmosphere. Because of this special status, stars like HR 8799 have a very complex spectral type. The luminosity profile of the Balmer lines in the star's spectrum, as well as the star's effective temperature, best match the typical properties of an F0 V star. However, the strength of the calcium II K absorption line and the other metallic lines are more like those of an A5 V star. The star's spectral type is therefore written as kA5 hF0 mA5 V; λ Boo.
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