We can now observe the motions of millions of stars through the sky.
Black Hole On The Radio
When matter accretes around a black hole, some of it is captured, but some of it is pushed away into long jets. In the case of this image, the jets stream out for about 1.5 million light years.
Across the Universe
Just how far is the most distant galaxy known? That depends on what you mean by distance.
Where Are You?
One of the most basic skills in astronomy is know how to find objects in the night sky. That means you need a way to navigate the sky. The simplest way is known as altitude and azimuth. Starting at due north, rotate clockwise along the horizon until you are directly under the star you want, then move above the horizon to reach your star. It is a simple coordinate system, since it is just so many degrees clockwise (azimuth) and so many degrees upward (altitude).
The Far Side
While we’re quite familiar with our side of the Milky Way galaxy, the far side of our galaxy is still a bit of a mystery. The reason for this is that the center of the Milky Way is filled with gas, dust and stars, so it is very difficult to see the other side of our galaxy. The central region is so cluttered with material that it sometimes referred to as the Zone of Avoidance, since we have to exclude that region from observations beyond our galaxy.
Beautiful Theory, Ugly Data
Both MOND and dark matter were introduced to address a problem with the way galaxies behave. At a basic level, the stars in a galaxy such as ours orbit the galactic center in roughly circular orbits. The speed of a star in its orbit should be governed by Newton’s law of gravity. So, using Newton’s gravitational theory, we can predict a star’s speed given its distance from the center and the distribution of matter in our galaxy. Newton’s beautiful theory doesn’t agree with the experimental data.
Point of View
Quasars, blazars, and radio galaxies are all related. It just depends upon your point of view.
Traffic Jam
How do spiral galaxies maintain their spiral shapes? It turns out there are matter waves that cause traffic jams within the spirals. These patterns are stable even as individual stars move through them.
Order and Chaos
How do you deal with chaos in computational astrophysics? It turns out there are ways to analyze the properties of a solution even if you don’t know what the exact solution is.
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