By Phil Plait
You might think this question would be easy to answer. If it’s big, it should be pretty straightforward to find, right? Yeah, well, the Universe isn’t always that simple.
First, what’s a galaxy? Basically, it’s a collection of stars, gas, and dust (as well as invisible dark matter) bound together by its own gravity. Some are elliptical (giant puff balls), some have disks and spiral arms, some are irregular (shapeless), and some peculiar (they have a shape, but it’s … weird). If you need a refresher, this episode of Crash Course Astronomy explains them:
Most galaxies have billions of stars. Our home galaxy, the Milky Way, has hundreds of billions strewn across a disk about 100,000 light-years in diameter. Some galaxies are much dinkier, and have only millions of stars; those are hard to find, even when they’re nearby, because they’re so faint.
Continue reading by clicking the name of the source below.