Mira is the red giant in Cetus that grows bright and then fades out of naked-eye view over most of a year, the prototype of the long-period variable stars.
At a glance
| type | red giant (class M) |
|---|---|
| distance from the Sun | 299 light-years (91.7 pc) |
| its light left it | 299 years ago |
| luminosity | 173 × the Sun |
| radius | 47.1 × the Sun |
| surface temperature | 3,050 K |
| constellation | Cetus (Sea Monster) |
Read off the piece’s own catalogue, the same values it draws with.
About Mira
Mira is a red giant near the end of its life, so swollen and cool that its outer layers no longer hold steady. The star pulsates, and as it swells and shrinks its brightness changes enormously: at its peak it is an easy naked-eye star, at its faintest it needs a telescope. Each cycle is slightly different from the last.
Its variability was noticed in the age of the first telescopes, and Mira, Latin for wonderful, was the name given to the star that came and went. It became the first known example of a whole class of pulsating giants, the Mira variables, which are the fate of stars like the Sun.
Mira is shedding gas into space as it moves, and ultraviolet images show a long tail of that gas trailing behind it. A smaller companion, thought to be a white dwarf, orbits it and draws on the giant’s outflow.
What you see in the piece
In the piece Mira is a deep orange-red point, its colour set by its cool surface. Its brightness is drawn at its catalogue value; in the real sky it would be vanishing or blazing depending on the month.
Questions
Why does Mira change brightness?
Mira is a pulsating red giant: it swells and shrinks over a cycle of most of a year, and its brightness rises and falls dramatically with it.
How far away is Mira?
Mira is 299 light-years (91.7 pc) from the Sun.