Astronomy Buff

Could Eta Carinae Destroy Earth?

by Tony on June 21st, 2007

Many people have already written about the latest image (pictured here) from the Chandra X-Ray Observatory released yesterday depicting the x-ray emissions produced as material is thrown off of the star and into surrounding gas a dust.

Eta Carinae is an extremely unstable nearby star that is very near its death and because of its mass, will end its life in a brilliant supernova explosion. Because of its relative close proximity to Earth, Eta Carinae will be one of the most spectacular events ever seen by humans.

Since many bloggers have written about this, including this excellent post from the Bad Astronomer, I won’t rehash much of what has already been said, but I will take a minute to address a question from one of my readers.

One reader wanted to know if this statement from Phil in his post was true:

When stars like Eta Carinae explode, they tend to shoot of beams of energy and matter that, at its distance of 7500 light years, could kill every living thing on Earth.

I know this seems like an outlandish statement, but it’s true. We are very close to a very massive star (over 100 times larger than ours) that is very old and ready to go, and when stars that big die, they die BIG.

The gamma radiation burst from a supernova explosion 7,500 light years away, in the right orientation to us, could destroy us. That’s a humbling and sobering thought, and it illustrates brilliantly just how much energy is involved with one one of these events.

So now, on top of everything else, we have to worry about global warming, being smashed by a meteorite in 2036 and now, supernova explosions, right?

Technorati Tags: chandra, eta carinae supernova

The important thing to remember about anything relating to astronomical events, is the timescales and distances involved. Things happen in the universe over a time period that is measured in millenia, not decades or human lifetimes, but in millions of years. Things are also very far away from each other.

The universe is not the static place people used to believe it was, and while the timescales involved are very long compared to a human lifetime, with the right timing, an interstellar event could very drastically affect our daily lives.

Here’s an image of the neighborhood Eta Carinae lives in (the star is toward the left of this image):

Illustration Credit: NASA/ESA
Here’s a cool zoomable version

As you can see, there’s a lot going in this nebula, this stellar nursery holds over 100,000 young stars, most of which are faint, small and low mass like the sun. The energy given off by the Eta Carinae supernova, when it does go off, will slam into the surrounding material, compressing gas and dust which will ultimately become new stars.

Even right now, without any explosions, Eta Carinae is giving off more energy than a million suns and has stellar winds of 2,000 kilometers per second, or more than four million miles per hour. This star is interesting no matter if it explodes or not.

I mean, come on, read this little tidbit from Chandra’s Press release:

In the 1840s, Eta Carinae had a massive eruption by ejecting more than 10 times the mass of the sun, to briefly become the second brightest star in the sky.

Now that’s a dynamic event! Imagine shedding 10 Suns at once. That’s a lot of mass, but what makes Eta Carinae so interesting is that the star remained intact afterward. For several years after the 1840, Eta Carina was the second brightest star in the sky.

OK, so now you want to know when it’s gonna explode so you can get the lawn chairs out and sit in your driveway and watch the fun, right?

Astronomers say, any time now. I know, WTF? Remember, these are astronomy timescales we’re talking about here. While our galaxy is a rotating disk full of whirling stars and filled with boiling interstellar gasses, all of this happens very slowly compared to the life span of a human being. It’s like watching weather form, you can see a storm developing over several hours, but it doesn’t seem to happen all that fast.

The Eta Carinae Supernova is imminent. In astronomy-time, that could mean today, tomorrow, next week or a hundred years from now but many astronomers believe it might happen in our lifetime.

One more little tidbit about Eta Carinae. The expansion rate of the gasses and material that came from the 1840 explosion is such that we actually have a two frame movie of the explosion. In other words, the gasses that have come off of that star have actually moved fast enough and far enough that we can compare an image taken not too long after 1840 with another one taken recently, and measure the velocity and see the motion.

This is the only stellar event I know of where this is true. Usually things happen over too long a timescale in astronomy, this is one case where we can see things happening real-time.

I tried to find an old image or at least someone who had put together this two-frame animation but was unable to find anything before I posted this. I’ll try to see if I can put something together.

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POSTED IN: astronomy timescales, general astronomy, stars