In celebration of the Hubble Space Telescope’s 31st year, NASA astronomers aimed the famed observatory at what is called a “celebrity star,” or one that is one of the brightest in our galaxy. This one, named AG Carinae, is wavering on the edge of self-destruction.
Originally noted by DPReview, the reason AG Carinae is so bright is that its glowing halo of gas and dust is the result of “a tug-of-war between gravity and radiation,” as NASA puts it. The giant visible structure was created from what NASA believes was one or more giant eruptions on the surface of the star about 10,000 years ago which blasted the outer layers of the AG Carinae into the space around its edges.
“The star’s outer layers were blown into space – like a boiling teapot popping off its lid,” NASA writes. “The expelled material amounts to roughly 10 times our Sun’s mass.”
NASA estimates that the shell of gas and dust is about five light-years wide, or approximately the distance from Earth to the nearest star, Proxima Centauri. In short, it’s huge.
“These outbursts are the typical life of a rare breed of star called a luminous blue variable, a brief convulsive phase in the short life of an ultra-bright, glamorous star that lives fast and dies young,” NASA continues.
The huge bursts of energy that produced this beautiful sight occur once or twice during a luminous blue variable’s lifetime. Such a star only casts off material when it is in danger of self-destruction as a supernova. Because of their massive size and super-hot temperatures, stars like AG Carinae are constantly in a struggle to maintain their own stability.
That struggle is caused by a constant battle of its own internal radiation pressure pushing outward while gravity pushes inward. As a result, the star is constantly expanding and contracting.
“The outward pressure occasionally wins the battle, and the star expands to such an immense size that it blows off its outer layers, like a volcano erupting,” NASA explains. “But this outburst only happens when the star is on the verge of coming apart. After the star ejects the material, it contracts to its normal size, settles back down, and becomes quiescent for a while.”
This kind of constant energy battle and instability has an effect on the star’s lifespan, however.
“These stars are among the most massive and brightest stars known. They live for only a few million years, compared to the roughly 10-billion-year lifetime of our Sun. AG Carinae is a few million years old and resides 20,000 light-years away inside our Milky Way galaxy,” NASA writes.
Luminous blue stars are rare, as NASA only knows of around 50 in our local group of neighboring galaxies. And while they are not particularly long-lived by star standards, they still exist for much longer than humans. They spend tens of thousands of years in this delicately balanced stage on the edge of self-destruction before ending their existence in a giant supernova blast. While this time seems like an eternity to us, it’s just a blink of an eye to the universe.
Image credits: Photo by NASA, ESA, STScI
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