θ¹ Orionis B is the faintest of the four Trapezium stars, a blue-white eclipsing star that turns out to be a whole small family of young stars.
At a glance
| type | blue-white star (class B) |
|---|---|
| distance from the Sun | 1,340 light-years (412 pc) |
| its light left it | 1,340 years ago |
| luminosity | 1,000 × the Sun |
| radius | 3 × the Sun |
| surface temperature | 17,000 K |
Read off the piece’s own catalogue, the same values it draws with.
About θ¹ Orionis B
θ¹ Orionis B, also known as BM Orionis, is the northernmost of the four Trapezium stars. It is an eclipsing binary: a companion crosses in front of it at regular intervals and the light dips.
Closer study has shown more members packed around it, so that B is a small multiple system of its own inside the larger cluster. Groups like this are unstable, and interactions within them can fling stars out of young clusters altogether.
It shares the age of the Orion Nebula Cluster, one of the youngest groups of stars near enough to study in detail.
What you see in the piece
Fly to the Orion Nebula and θ¹ Orionis B is the dimmest of the four Trapezium stars, blue-white beside the brilliant C.
Questions
Is θ¹ Orionis B a single star?
No. It is an eclipsing binary with further companions around it, a small multiple system inside the Trapezium.
How bright is θ¹ Orionis B?
It shines about 1,000 × the Sun, far less than its neighbour θ¹ Orionis C.