HR 8799

HR 8799

Star

HR 8799 — a hot, young A/F-type star about 1.5 times the Sun's mass, ~134 light-years away in Pegasus. At only ~30 million years old it is a chemically peculiar (λ Boötis) star, still surrounded by a dusty disk — and by four giant planets bright enough to photograph.

Open in 3D viewSee HR 8799 in the live, interactive 3D map

Key facts

Mass
2.98 × 10³⁰ kg
1.5 M☉
Radius
1,036,593 km
1.49× wider than the Sun
Surface temperature
7,300 K (7027 °C)
Spectral type
A5 / F0 (λ Boötis — chemically peculiar), young

Science

Physical

Mass
2.98 × 10³⁰ kg · 1.5 M☉
Radius
1,036,593 km · 1.49× wider than the Sun
Density
639 kg/m³ · 0.64× water
Spectral type
A5 / F0 (λ Boötis — chemically peculiar), young

Composition

By mass
A hot, young main-sequence star about 1.5 solar masses, only ~30 million years old and still ringed by a dusty debris disk. Its youth is what makes its giant planets photographable — they are still hot from formation and glow in the infrared.

Temperature

Surface
7,300 K (7027 °C)

Radiation & temperature

Luminosity
2.17 × 10²⁷ W · 5.68 L☉
Surface temperature
7,300 K (7027 °C)
Peak wavelength
397 nm · violet-blue light

Discovery & history

Name
A Bright Star Catalogue designation; no proper name.

Catalogued long ago as a bright star, it became famous in 2008 as the first star whose planets — several at once — were captured in direct images rather than inferred.

Images

A time-lapse of the four planets orbiting HR 8799, assembled from REAL telescope images (W. M. Keck Observatory) — actual photographs of the planets, not an artist's concept.
Jason Wang / Christian Marois (CC BY 3.0) · Wikimedia Commons
The HR 8799 planetary system imaged by the Hubble Space Telescope — a REAL photograph; the star's overwhelming light is masked so the planets show.
NASA / ESA / STScI (CC BY 4.0) · Wikimedia Commons
Where to find it — in Pegasus, the Winged Horse (IAU constellation chart). To the eye it is a single point of light; no telescope has imaged its surface.
IAU / Sky & Telescope, R. Sinnott & R. Fienberg (CC BY 3.0) · Wikimedia Commons

Images from open archives · credit shown per image