Big Changes

For most of a star’s long life, things happen slowly. A star like the Sun, for example, steadily converts hydrogen to helium in its core for about 10 billion years. At the end of that run, the pace picks up. And in the star’s final, colorful act, major changes can happen over just a few centuries.

One star that may be going through that last act is in Hydra, the water snake, which slithers quite low across the southwest at nightfall.

V Hydra appears to consist of two stars. The main star is the same mass as the Sun. It’s at the very end of its life, though, so it’s puffed up to more than 400 times the Sun’s diameter. The star pulses in and out like a beating heart, and it’s ejecting a lot of gas into space.

The second star orbits the bigger one every eight and a half years on a stretched-out path. When it gets close to the bigger star, it grabs some of the expelled gas, forming a disk. When enough gas builds up, some of it may be flung back into space as a “cannonball” — a blob that’s twice as heavy as the planet Mars.

So today, astronomers are seeing big changes in V Hydra every few years. And the changes could come even faster in the not-too-distant future. The bigger star may soon expel all of its outer layers of gas into space, forming a colorful nebula. The companion may sculpt it into an exotic shape — perhaps an hourglass, or even a butterfly. It’s a process that could play out very soon — a fast-paced change for a Sun-like star.


Script by Damond Benningfield

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