How do you study astronomy?

There are two main branches of astronomy - observational and theoretical. Observational astronomers are those who observe light from the universe through one of many telescopes, and describe what they are seeing in terms of what we believe must be producing that light. Theoretical astronomers, by contrast, develop detailed models of the universe to help explain what the observers are seeing. These two branches are extremely complimentary approaches to understanding the universe, and if either branch of astronomy were not equally well-developed as the other, our understanding of the skies would suffer for it.

If you’re an observer, you’ll work with a group of people to put together a proposal to use a specific telescope - whichever telescope is best suited for your particular science. To figure out which one is best suited, you’ll have to answer a series of questions. What wavelength of light will be most useful in answering the question? How small of a feature do you need to be able to see? How faint is your object? There’s no absolute “best” telescope - it will always depend on what you’re trying to do. The world’s most sensitive optical telescope is useless if your science question can only be answered by looking at radio waves. As you answer these questions, you’ll narrow down the field of options dramatically. Usually by the time you’re done, there are only a few telescopes in the world that can actually do what you want to be able to do.

The proposal to use your chosen telescope has to be extremely convincing. Everyone who wants to use that telescope is in competition to get time on the telescope, and the telescope operators want to make sure that they give time to people with the best ideas. Most telescopes have requests for at least twice as much time as they have to give out, but some of the bigger telescopes can get requests for over ten times the amount of time they have to work with. As a result of this “oversubscription”, a lot of proposals are rejected at this point.

Assuming your idea is approved, you can then hope that you actually get the data! If you happen to be using a space telescope, this is almost never a problem unless the telescope breaks. However, if you’re using a telescope on the ground, the weather can get in the way. Most telescopes use a ranking - if your science requires pristine conditions, they’ll wait for them to happen, and as soon as the weather gets that good, they will take your data for you. You don’t have to physically be present at the telescope at all - you’ll just get an email saying that the telescope took data for you. If your science doesn’t need perfect, clear skies, then you have better odds of having your data taken, since the skies are imperfect more often than not. For some kinds of radio astronomy, useful data can be taken both during the day and in the rain - if you’re doing this kind of science, once you get through the proposal, you’ve got very good odds of getting data.

Once you get your data, it usually has to be massaged into a useful format - this step is called data reduction. This is usually the most time consuming part of the whole process, and involves astronomy’s secret: there is a ton of programming involved in astronomy. Once the data has yielded the results you were after, you can dive into the world of analysis; what do those numbers mean for the way we understand the universe? Do they fit neatly in with previous research, or do pieces of our understanding need to be updated or replaced? Sometimes there’s no clear explanation, and the only thing to do is to turn to the theorists and ask, “What does this mean? How could this happen?”

Theorists do almost exactly the same thing - the difference is that instead of applying for time on a telescope, they will apply for time on a supercomputer. If you need to run a simulation of the universe, there are a ton of numbers to crunch and equations to solve at each step in time - this is usually too much for a single computer, so their science must be sent off to a supercomputer to do the heavy lifting. The other difference here is that most theorists don’t have to worry about bad weather when they’re scheduled to use the supercomputer. But other than those differences, theorists and observers approach questions in a very similar way, both starting from a science question or three. Perhaps that question was inspired by an observer, or perhaps by an earlier simulation, they can replicate what might be happening in outer space, testing how things would change if various things were to change in importance, or be removed or included. They can then turn to the observers and say, “You should look for some of these things - our models say they should be important.”

Each new piece of knowledge builds on what has already been done, and the most progress can be made when you have a diverse group of people with different backgrounds within astronomy. Because astronomy is such a small field, this often means international collaborations are built up as people move around the world and collect friends and experts into their projects.

By the same token, if a link in the astronomical chain is broken, it affects far more than just that one link. If a telescope breaks down, it affects everyone, worldwide, that wanted to use that telescope. If telescopes are shut down, or astronomers are kept from doing work, it doesn’t just affect the people working at those telescopes and those astronomers’ ability to do their own research. It affects everyone who works with them.

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