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Close Encounters of the Stellar Kind

In Stars by Brian Koberlein9 Comments

A star known as HIP 85605 is on a collision course with our solar system. Not a collision course as in Armageddon, or When Worlds Collide, but rather on a path to come within 0.04 parsecs of the Sun. That might seem close, but that would make it more than 8,000 times more distant than Earth at its closest approach (8,000 AU). Distant Eris is only 100 AU by comparison. Given that stellar distances are typically measured in light years, and this encounter would be only 50 light days away, that’s remarkably close by astronomical standards. This close encounter won’t occur for another 400,000 years or so. Currently HIP 85605 is about 16 light years away, so we have time to plan for its visit. But it does raise an interesting question as to how such a close encounter could affect our solar system.

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It’s Gonna Blow!

In Stars by Brian Koberlein0 Comments

Eta Carinae is about 7,500 light years away, and its going to explode any time now. Mind you, “any time now” means sometime over the next ten to twenty thousand years or so. But recently the star been in the news again as an existential threat to our planet. It must be that time of year again.

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In Stars by Brian Koberlein1 Comment

One of the popular astronomy facts that gets passed around every so often is how small our Sun is compared to other stars. The Sun appears large to us, but it’s tiny compared to giant stars like Betelgeuse. While this is true, it isn’t the best metric for comparing stars. While Betelgeuse has a diameter 1,000 times that of the Sun, it only has 10 – 20 times the mass. Betelgeuse is much larger than our Sun, but also much less dense.

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Kissing Cousins

In Stars by Brian Koberlein3 Comments

In the constellation of Camelopardalis (also known as the Giraffe) is a faint star known as MY Cam. It appears faint because it is about 13,000 light years away, but its spectrum showed that it was actually a blue supergiant. Then recently, detailed measurements indicated that it was a spectroscopic binary consisting of two blue supergiants. Now a new paper in Astronomy & Astrophysics has revealed that the two stars orbit very, very closely.

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All Alone in the Night

In Stars by Brian Koberlein2 Comments

Although we think of deep space as being dark, that isn’t entirely true. The universe is filled with a background glow of radiation. The most famous is the cosmic microwave background, which is the remnant glow of the big bang. There is also the x-ray background, caused by things like active galactic nuclei, the radio background. This week new research on the infrared background has been published in Science, and the results are somewhat surprising.

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Holding It Together

In Stars by Brian Koberlein5 Comments

In the center of our Milky Way galaxy is a supermassive black hole. We can’t see this black hole directly because there is too much dust in the direction of galactic center, but radio waves can penetrate that dust, so we can observe the radio signals of hot stars and gas near galactic center. We’ve been observing these signals over several years, and we’ve noticed how the stars near galactic center orbit the region very quickly. From their orbital motion and a simple use of Kepler’s laws we can get a pretty good idea of the mass of the black hole. It turns out to be about 4 million solar masses. While this is a huge black hole, most of the stars orbiting it aren’t too terribly close. So for the time being they aren’t at risk of being ripped apart by the intense forces near the black hole. But there was one object recently that did make a very close approach.