It’s possible that most people on Earth have never seen the Milky Way, the galaxy in which we live. The Milky Way used to be a part of every human’s life experience, but now that the majority of mankind lives in cities, with their light pollution, the Milky Way is rarely seen.
Our Milky Way galaxy is at its best for the next couple of weeks, but most of you will need to make a special effort to see it. It will probably require a drive of an hour or more to reach a dark enough location, where the Milky Way will be visible. Then it will require another 20 minutes for your eyes to become adjusted to the dark.
On visual inspection M94 appears to be a series of ring like structures. As one of the closest starburst-ringed galaxies it possesses one of the highest optical surface brightness nuclei known.
At its center is a 1400 light year stellar bar which has been an important influence on the overall morphology of the galaxy. Surrounding the central bar is an inner stellar disk with a radius of about 2300 light years. Further out at a radius of about 3500 light years is an almost perfectly circular starburst ring.
The Veil Nebula is a cloud of heated and ionized gas and dust in the constellation Cygnus. It constitutes the visible portions of the Cygnus Loop, a large but relatively faint supernova remnant. The source supernova exploded some 5,000 to 8,000 years ago, and the remnants have since expanded to cover an area roughly 3 degrees in diameter. The distance to the nebula is not precisely known, but recent evidence from the Far Ultraviolet Spectroscopic Explorer (FUSE) supports a distance of about 1,470 light-years.
One topic that people always ask astronomers about is black holes. These seemingly mysterious and bizarre objects are known to gobble up everything around them, even light, and physics as we know it cannot accurately describe what goes on inside.
From the outside, however, we consider black holes to be pretty simple objects, described completely by their mass, or size, spin and charge. This is often called the “no-hair” theorem of black holes.
For the most part, something that massive is almost certainly neutral, so astronomers really only care about how big a black hole is and how fast it is spinning.
As you might imagine, actually measuring these quantities can be a bit tricky.