Astronomy

One of the things that always amazes me about astronomy is the ingenious ways astronomers come up with to squeeze information out of seemingly tiny bits of data, and to find data in unexpected places.

This story about recent research on the star Eta Carinae is a good example of that. Eta Carinae currently appears to the naked eye as a fairly dim star, with an apparent magnitude of about 4.5, but its brightness has varied greatly during its observational history, from too dim to be seen with the naked eye at all, to being the second-brightest star in the night sky, after Sirius. Its bright episode lasted 20 years, and the peak brightness, with an apparent magnitude of -0.8, was observed in 1843. Unfortunately, astronomers at that time were not able to measure all the things about it that we would like to know about its unusual outburst. But some astronomers have come up with an ingenious way to observe the light from the outburst. The light from the outburst takes time to travel. Some of it took a while to reach some interstellar dust clouds, which then reflected it, sending some of its light back towards earth. That light is just reaching us now. So by observing the changes in the light reflected from those dust clouds, the astronomers can see changes in the light given off by Eta Carinae during its outburst.

It turns out that the Fried Egg Nebula (IRAS 17163-3907) surrounds a yellow hypergiant star. The star itself has about 20 times the Sun's mass, and its radius is almost as much as the radius of Jupiter's orbit. The nebula surrounding it has a radius of about 10,000 AU. (For a different solar system comparison, that's about 10 times Sedna's aphelion distance.)

Here's another article.