HR 8799
Where is HR 8799?
Look south, about 60° up at 23:08 in Pegasus.
- Rises
- 15:10
- Highest
- 23:10
- Sets
- 07:11
- Best after dark
- 23:08 · 60°
Can I see HR 8799?
No. The planets of HR 8799 can’t be seen with the eye, binoculars or any amateur telescope: they are lost in their star’s light. What you can do is point toward the star.
From London tonight, the star HR 8799 is above the horizon all night. It’s highest after dark at 23:08, in the south at 60°.
Why is HR 8799 interesting?
HR 8799 has 5 known planets, discovered between 2008 and 2023 by the astrometry and imaging methods.
What can you see?
Eyes
Direction onlyAround magnitude 6: at the limit of naked-eye visibility under dark skies.
Binoculars
Visible as a faint star near the Great Square of Pegasus.
Telescope
A white star. The planets themselves can’t be seen with any backyard telescope. Imaging them requires the world’s largest telescopes and special techniques to block the starlight.
About
HR 8799 is a young white star about 130 light-years away in Pegasus. In 2008 it became the first star whose planets were photographed directly as a family: astronomers imaged several giant planets around it.
At least four giant planets orbit the star, each several times the mass of Jupiter, at distances similar to or beyond the outer planets of our Solar System. Because the system is young, the planets still glow from the heat of their formation, which is why they can be imaged.
Sequences of images taken over years show the planets slowly moving around their star.
HR 8799 is only about 30 million years old. Its known planets orbit at distances of roughly 15 to 70 times Earth’s distance from the Sun, taking decades to centuries to go around once.
The system also has belts of dust and debris inside and outside the planets, a little like the asteroid belt and Kuiper Belt around the Sun.
The HR 8799 system
| Planet | Mass | Radius | Orbit | From star | Found | Method |
|---|---|---|---|---|---|---|
| HR 8799 f | 11.50 M♃ | — | — | 2.5 AU | 2023 | Astrometry |
| HR 8799 e | 11.67 M♃ | 1.17 R♃ | 49.3 years | 15.8 AU | 2010 | Imaging |
| HR 8799 d | 9.17 M♃ | 1.20 R♃ | 112.4 years | 25.85 AU | 2008 | Imaging |
| HR 8799 c | 9.02 M♃ | 1.30 R♃ | 224.9 years | 43.44 AU | 2008 | Imaging |
| HR 8799 b | 4.65 M♃ | 1.20 R♃ | 449.7 years | 68.79 AU | 2008 | Imaging |
Questions
If the planets were photographed, can I see them?
Sources: The Extrasolar Planets Encyclopaedia (CC BY 4.0); star chart: Wikidata (CC0). Positions computed for your place and time with astronomy-engine. Data & Licences