There a region of space about 150 million light years away that is gravitationally attracting the galaxies in its region, including ours. It is known as the great attractor, and we’re not entirely sure what’s there. The problem is it happens to lie in the direction of the zone of avoidance, so our own galaxy is blocking our view.
Our location within the Milky Way means that our view of the cosmos is somewhat obscured. One way we deal with this is by defining a zone of avoidance.
For scientific imagery you want the data your camera gathers be “raw.” In other words, you don’t want the image to be compressed or manipulated in any way. For this reason a different image format is used, known as the Flexible Image Transport System, or FITS.
It can be quite useful to have a stationary star in the sky, particularly when trying to navigate the open oceans without modern tools such as GPS. So Polaris is a happy coincidence. Of course, Polaris hasn’t always been the north star, nor will it be for long (on an astronomical scale).
In our modern age, we measure time by clocks calibrated to an international standard. With the exception of the occasional leap second, each day is exactly 24 hours long. So you might figure that the time between noon on Monday and noon on Tuesday is likewise 24 hours, but things are not quite so simple.
The first known binary stars were observed in the 1800s, but it wasn’t until the 1900s with the introduction of the filar micrometer that decently accurate measurements could be made. This device allowed you to center your telescope on the primary star, and then measure the position of the secondary star relative to the primary. By taking measurements over time (sometimes years or decades) you can start to see the companion star trace its path.
The figure below shows the positions of more than a thousand galaxies in the universe. You might think that tells us things about the history and evolution of the universe, and you’d be right. But it also tells us something about how we observe the universe. Knowing the latter is important, because all measurements have biases. If you don’t account for observation biases, you might mis-interpret your data.
The brightness of a star depends not only on how bright it actually is, but also on how far away it is. This is why we use quantities such as apparent magnitude and absolute magnitude.