Polis is a distant blue-white supergiant above the Teapot of Sagittarius, a hot, massive star whose distance has never been measured well.
At a glance
| type | blue-white supergiant (class B) |
|---|---|
| distance from the Sun | not measured: no usable parallax. The piece draws it at 3,260 light-years (1 kpc)model |
| luminosity | 178,000 × the Sunmodel |
| radius | 29 × the Sunmodel |
| surface temperature | 22,000 K |
| constellation | Sagittarius (Archer) |
Read off the piece’s own catalogue, the same values it draws with. Model marks a property of the piece’s galaxy model rather than a measurement.
About Polis
Polis, Mu Sagittarii, is a hot, massive supergiant of class B. Its parallax is too small and uncertain to give a usable distance, so how far away it lies, and so how luminous and how large it really is, has to be inferred from its spectrum rather than measured.
Its light reaches us through the dusty plane of the Milky Way, which dims and reddens it. It sits in the rich star fields north of the Teapot, near the Archer’s bow.
What you see in the piece
From Earth it looks like one of the Archer’s modest stars. With no measured distance to place it by, the piece sets it at a stand-in distance, so where it sits when you fly out is a placeholder, not a position.
Measured or modelled
The distance on the card is a stand-in chosen by the piece, not a measurement, and the luminosity and radius are worked out from it; they would change with a real distance.
Questions
How far away is Polis?
Its distance is not measured: there is no usable parallax. The piece draws it at 3,260 light-years (1 kpc) as a stand-in.
How luminous is Mu Sagittarii?
Its true luminosity is not known. The card’s 178,000 × the Sun is a model value that follows from the stand-in distance, not a measurement.