I don’t know what’s more amazing about this press release; the idea that a star can spin so rapidly it can be so flat, or that the observations have error bars that are 10 microarcseconds in size. Just so’s you know, a microarcsecond is a teeny weeny angle, about 2.7 x 10^-10 (0.00000000027) degrees. Ten of them is still pretty small.
Still not seeing it?
Okay then, reach into your pocket and grab a quarter. Hold it up at arm’s length. It subtends an angle of roughly 2 degrees (four times the size of the Moon in the sky).
Now stretch your arm. A long way. When your hand is 40,000 miles past the distance to the Moon, stop. Now the quarter is 10 microarcseconds across.
Pretty cool what us hairless apes can do, eh? In this case, our grasp outextends our reach.
I make 10 microarcseconds to be 2.7…x10[sup]-11[/sup]. It’s too late for me to correct the rest, so we’ll pretend it’s fine. It’s only one order of magnitude.
Okay, you people are killing this thread with math. Stoppit. Who cares what the exponent on the stupid microarcsecond is. Although they do say that Achernar appears the same size as a car on the moon. That’s kind of cool.
For people who care less about the telescopes used to observe and more about what the star itself is doing, Achernar is spinning so fast that it looks like this. It’s near its breakup speed, the rotation speed above which, if you were standing on the surface, you would be thrown off. So… yeah. Hold on tight.
Wow. That’s all I can say really. Wow. And I thought that determining the spatial extent of the X-ray emission of a galaxy 190 Mpc away was impressive.
I take it that the green vs. red dots on the data plot indicates which of the two arms of the interferometer was used. Does anybody else find it suspiscious that the direction of the interferometer arms coincide so well with the star’s orientation? Inteferometry isn’t my field but it looks like it can be instrumental error. Then again, I don’t suppose they would make such an elementary mistake…
It’s still an impressive accomplishment though. Did everyone see the VLTI homepage? It’s the instrument used to obtain this data. It consists of four 8-meter telescopes. To put that into perspective, until just 10 years ago the largest telescope in the world had a 6-meter (18 feet) diameter mirror. Even today there are only about 10 telescopes larger than 7 meters. The VLTI links 4 of those telescopes to function as a single telescope. And interferometry means if you link two telescopes that are 100 meters apart, you get the angular resolution of a 100-meter telescope.
Although they do say that Achernar appears the same size as a car on the moon. That’s kind of cool.
