Transients

The starry dome of the night sky seldom changes. The stars shine steadily night after night, century after century. Occasionally, though, a bright new star appears — an explosion known as a nova or supernova.

If our eyes could see deeper into the sky, and at wavelengths other than visible light, we’d see outbursts all the time — thousands of them every night. Astronomers have discovered many classes of these transient events — flashes that last anywhere from a fraction of a second to months or years.

The list includes gamma-ray bursts — the death of a massive star that briefly outshines everything else in the universe. It also includes the mergers of stellar corpses known as neutron stars, the destruction of stars by black holes, intense flares from normal stars, and many others.

The most recent class of transient is fast radio bursts. These objects emit flashes of radio waves that can last for less than a thousandth of a second. In that time, though, they can outshine hundreds of galaxies as big as the Milky Way.

Astronomers have seen a few dozen of these events. Most of them pop off just once. But a couple have repeated themselves. That means they can’t be produced by stellar explosions, because there’d be nothing left to flash again. They may be highly magnetic neutron stars or other exotic objects, perhaps near supermassive black holes — objects that flicker from across the universe.

More tomorrow.

Script by Damond Benningfield