Mira compared to the Sun

A red giant that pulses over about 332 days, swinging from an easy naked-eye star to far too faint to see without a telescope.

How big is Mira compared to the Sun?

Mira is roughly 350 times as wide as the Sun.

Mira has roughly one and a quarter times the mass of the Sun.

Mira’s surface is 2,645 °C. The Sun’s surface is 5,499 °C.

You see Mira as it was about 300 years ago.

What it is: A red giant near the end of its life, so bloated that if it sat where the Sun does it would swallow Mars. It pulses in and out over about 332 days, and its brightness swings by a factor of hundreds or more as it does.; How we know: Four centuries of people writing down how bright it looked, night after night, build a curve that repeats — and the swing in that curve is huge: as the star swells and cools, molecules form in its outer atmosphere and swallow much of its visible light, and as it shrinks and heats they break up again.
The star that is sometimes not there: Visual magnitude runs from about 2.0 at maximum to about 10.1 at minimum.
It leaves a tail: Discovered by GALEX in 2007; the tail spans 2 degrees of sky — 10.47 light-years at the distance used here (about 300 light-years) — and holds material shed over roughly the last 26,000 years.; How we know: The trail glows only in far ultraviolet, which never reaches the ground — Earth’s air blocks it. It took a telescope above the atmosphere, taking a picture in a colour no eye has, to see something that had been streaming behind a naked-eye star the whole time.
Its name and its story: David Fabricius saw it in 1596, watched it fade, and assumed he had caught a nova. When it came back in 1609 he had found something nobody had a word for: a star that was neither steady nor gone. Hevelius named it Mira, “the wonderful one”, and the whole class is named after it.

The numbers