The end of a short life

Eta Carinae is destined to die young. Most stars live for billions of years, but stars as massive and active as Eta Carinae burn through their fuel in an extremely short time -- as short as one million years or so, very quick for a star. They almost always end the same way: With a supernova explosion, a massive detonation that blows the star apart and scatters its remains for trillions of miles (kilometers) around.

That's how most supermassive stars end, but Eta Carinae is such an extreme case that another possibility exists: It could end as a hypernova, a super-supernova that at its peak will outshine the entire galaxy.

Chandra's X-ray image of Eta Carinae reveals a hot inner core and three distinct structures racing outward at high speeds.

The blazing violence of such an event is difficult to describe. Were it much closer it could even wipe out all life on Earth, eradicating our thin biosphere just like an ultraviolet lamp kills microbes. Fortunately it's not that close, but at 7,500 light-years it's still close enough to do some damage.

However, the likely damage is not to humans directly, but to satellites and the upper atmosphere. That's because an explosion of this type generates huge amounts of high-energy radiation such as gamma rays. We on Earth are well shielded from gamma rays by our atmosphere, but satellites in space would be vulnerable and some of their electronics could be damaged by such an event.

Some have speculated that a huge blast of gamma rays could also affect the upper atmosphere, including the ozone layer. But that remains only speculation, and any such effect is likely to be very transient because the blast of gamma rays would be fairly brief.

The only humans who might suffer directly from Eta Carinae's violent demise would be astronauts in space. Outside of the Earth's protective atmosphere they would be subject to the same powerful radiation as satellites, with conceivably lethal effect. While our own sun is also capable of lethal emissions, such as coronal mass ejections that could be harmful to astronauts, the difference is that our sun's eruptions usually give us some warning, whereas Eta Carinae would not.