This star is X light-years away, that galaxy is X million light-years away. That beginning the Universe is X billion light-years away. But how do astronomers know? I’m perpetually in a state where I’m talking about objects which are unimaginably far away. It’s pretty much impossible to imagine how huge some our Universe is. Our […]
Fall will soon be at our doorstep. But before the leaves change colors and the smell of pumpkin fills our coffee shops, the Pleiades star cluster will mark the new season with its earlier presence in the night sky. The delicate grouping of blue stars has been a prominent sight since antiquity. But in recent […]
In astronomy we throw around the term “light-year” seemingly as fast as light itself travels. And yet actually measuring this distance is incredibly tricky. A star’s parallax — its tiny apparent shift once a year caused by our moving viewpoint on Earth — tells its distance more truly than any other method. Accurate parallaxes of […]
If you’re into astronomy, or just a fan of any science fiction franchise worth its salt, then chances are you’ve heard the term parsec thrown around. But what is a parsec exactly? Basically, it’s a unit of length used to measure the astronomically large distances between objects beyond our Solar System.
If you’re a semi-serious amateur astronomer, chances are you’ve heard of a variable pair of stars called SS Cygni. When you watch the system for long enough, you’re rewarded with a brightness outburst that then fades away and then returns, regularly, over and over again. Turns out this bright pair is even closer to us than […]
Measuring distance doesn’t sound like a very challenging thing to do — just pick your standard unit of choice and corresponding tool calibrated to it, and see how the numbers add up. Use a meter stick, a tape measure, or perhaps take a drive, and you can get a fairly accurate answer. But in astronomy, […]
[/caption] As the bright Mars-crossing asteroid 433 Eros makes its closest approach to Earth since 1975, astronomers around the globe are taking the opportunity to measure its position in the sky, thereby fine-tuning our working knowledge of distances in the solar system. Using the optical principle of parallax, whereby different viewpoints of the same object […]
[/caption] Parallax is the apparent difference in the position (line of sight to) an object, when the object is viewed from different locations. So, when we observe that a star has apparently moved (not to be confused with it actually having moved – proper motion), when we look at it from two different locations on […]