Almaaz is a distant, luminous star in Auriga, famous because every so often a vast dark disc around an unseen companion passes in front of it.
At a glance
| type | yellow-white giant (class F) |
|---|---|
| distance from the Sun | 2,130 light-years (654 pc) |
| its light left it | 2,130 years ago |
| luminosity | 23,200 × the Sun |
| radius | 95.2 × the Sun |
| surface temperature | 7,300 K |
| constellation | Auriga (Charioteer) |
Read off the piece’s own catalogue, the same values it draws with.
About Almaaz
Almaaz is a yellow-white supergiant, so luminous that it is easily seen even from far beyond most of Auriga’s stars. Its fame comes from its eclipses. At long intervals its light dims and stays dim for many months, far longer than any star could take to cross it.
The explanation that has held up is a companion wrapped in an enormous, opaque disc of dust, seen nearly edge on, which slides across Almaaz and blocks part of its light. Infrared observations during recent eclipses have supported this picture.
The name comes from Arabic for the he-goat. Almaaz is one of the Kids, the small triangle of stars beside Capella, the Goat, carried by the Charioteer.
What you see in the piece
Almaaz sits beside Capella in the sky, but in the piece it lies far beyond it; fly to Capella and Almaaz barely moves, still a distant light behind.
Measured or modelled
The nature of the companion inside the disc is still debated: the usual picture is a hot star, or pair of stars, hidden in the dust, but its mass and type are inferred from models of the eclipses.
Questions
Why does Almaaz dim?
Almaaz is eclipsed by a companion hidden in a huge dark disc of dust, which passes in front of it and blocks part of its light for many months.
How far away is Almaaz?
Almaaz is 2,130 light-years (654 pc) from the Sun.