Ardra, and a star that is dying while we watch

Find Orion in the east before dawn. Three bright stars in a short row come up nearly upright, and above them and to the left stand two more. The lower of that pair is orange. That is Betelgeuse, and it is bright enough to see from a lit street.

The essay is that star's life story. Betelgeuse is a red supergiant: a heavy star that has used up the hydrogen in its middle, swollen enormously, and cooled at the surface as it swelled. Cool stars look red. Put it where the sun is and it would take in the earth and reach out past Mars.

Nobody knows exactly how far away it is: published distances run from about 500 to over 700 light years. The star looks so wide through a telescope, and its surface churns so much, that the small wobble used to measure distance gets lost in the blur.

It is young and nearly finished. The sun is 4,500 million years old and not yet halfway through its life. Betelgeuse is under 10 million years old and close to the end of its. Heavy stars burn fast.

You can watch it change. Its brightness moves between about 0.0 and 1.6 on the astronomers' scale, on a beat of roughly 400 days. John Herschel noticed this by eye in 1836.

In late 2019 it faded further than it ever had on record. Telescopes later showed why: the star threw off a bubble of gas, a patch of its surface cooled, and there the gas turned into solid dust that hid part of the star from us. It was normal again by April 2020.

One day it will explode as a supernova. The usual estimate is sometime within the next hundred thousand years, which is not a statement about anybody's lifetime.

The station's name, Ardra, means wet. Its deity is Rudra, a storm god. The essay declines to turn that into a paragraph about stormy personalities, and offers the plain sense of the word: wet things can still be shaped, and dry things cannot.