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 (7,027 °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; Computed from mass and radius
Spectral type: A5 / F0 (λ Boötis — chemically peculiar), young

Motion through space

Proper motion: 0.119 arcseconds per year · its drift across our sky; SIMBAD — 2020yCat.1350....0G, 2022yCat.1355....0G
Radial velocity: -10.4 km/s · approaching the Sun; SIMBAD — 2020yCat.1350....0G, 2022yCat.1355....0G
Speed across our line of sight: 23.1 km/s; Computed from proper motion and parallax
Speed through space, relative to the Sun: 25.4 km/s; Computed from proper motion, parallax and radial velocity

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 (7,027 °C)

Radiation & temperature

Luminosity: 2.17 × 10²⁷ W · 5.68 L☉
Surface temperature: 7,300 K (7,027 °C)
Peak wavelength: 397 nm · violet-blue light; Computed (Wien's law) from the surface temperature

Discovery & history

Method: Telescope
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

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