NASA's Next Big Thing

Interview by Jennifer Rainey Marquez

When it launches in 2019, the James Webb Space Telescope (JWST) will be NASA’s most powerful observatory in space — capable of peering deep into the universe. More than 100 teams of scientists competed to carry out the first research using the telescope, and recently the space agency announced it had chosen 13 proposals to study a wide range of targets. One of those inaugural teams will be led by Dr. Misty Bentz, an associate professor in Georgia State’s Department of Physics and Astronomy. We recently spoke with her about the galaxy she plans to study.

Congratulations on being among the first researchers selected to use the JWST, which some people are calling the next Hubble. How do the two telescopes compare?

It’s not exactly a replacement for Hubble. It’s a different kind of tool. Hubble can see three types of light: visible light, ultraviolet light, which is what burns your skin, and infrared light, which you can’t see but you can feel. Think of a heat lamp.

However, Hubble’s limitation is that its mirror is relatively small. The bigger the mirror, the more light it can collect and the fainter the objects it can see. The JWST’s mirror is more than seven times the size of Hubble’s mirror, so it will be able to see objects that are very faint and far away. But the JWST has a limitation as well, which is that it only works in infrared light and the red part of the visible light.

We as scientists need to figure out how to best use this new tool, and our project will very carefully test one of the specific instruments on the telescope.

What exactly will you be testing?

This particular instrument can measure spectra from many different positions. People say a picture is worth 1,000 words, but a spectrum is worth 1,000 pictures, because it provides so much information about temperatures, densities, chemical compositions, motions—all these things we want to be able to learn more about. And if we can study spectra at all these different positions, now we have a huge amount of information that can show us the physics of what’s happening in the galaxy.

We’ll be using this instrument to observe a galaxy that’s about 60 million light years away. We’re evaluating how the data from this new instrument compare to the data we can get using telescopes that we have here on the ground on Earth.

How did you choose this galaxy to study?

In the process of doing these tests, we’ll be trying to determine the mass of the supermassive black hole in the center of the galaxy. We call black holes “black” because they’re invisible, which makes them very difficult to observe — unless they’re actively feeding. When a black hole “eats” matter that material gets super-heated, which makes it glow, just like a metal rod when you stick it in a fire.

But black holes that are actively feeding are pretty rare in the universe these days. There are only about six or seven feeding black holes that are relatively close by, in terms of things in outer space. Of those, we chose this one because we have good data from the ground already, so we can directly compare our observations to what we’ve been able to observe before.

What can we learn by studying these kinds of black holes?

We’ve found that the mass of a black hole is actually related to several other characteristics of the surrounding galaxy. Which is interesting — why would you have this enormous extended galaxy that seems to reflect something about this relatively small compact thing in the middle? From what we’ve been able to tell, they actually regulate the growth of one another.

As a black hole is feeding, it’s releasing a lot of energy into the galaxy. That energy can run into gas clouds and shut down star formation. Or it can throw material out of the galaxy, which shuts down the feeding process. So it seems that galaxies and black holes have evolved together over the history of the universe.

Studying black holes may provide insight into other questions like: Why does the universe look the way it does? Why does our galaxy look the way it does today? What can that tell me about how things have changed over the last 14 billion years? And is it somehow related to why we’re here?

When will your project begin?

It will most likely be about two years from now. After launch, which is scheduled for spring 2019, the JWST will fly for a month to get a million miles out to its location. Then there will be some tests to make sure everything is turned on and working properly. It’s expected that about six months after launch is when these 13 research projects will commence.

Why do you think that yours was one of the projects chosen this first round?

I think I convincingly made the case that these are important questions to answer in order to potentially open up new areas of scientific research.

Hopefully, we’ll find that you can do all sorts of interesting work with this new instrument, and then that will inspire other people to say, “Well if that’s the case, then I have this great idea.” And, of course, I’d like to be one of those people too. But it’s important to actually do the test first.

What has it been like since you got the go-ahead from NASA?

As so many colleagues have reached out — and they’re all so excited for me — it has started to sink in that this is kind of a big deal. I’ve done a lot of proposals for the Hubble telescope before, and most of the time you are told “no.” So a real honor to get a “yes.”

Top photo by Steven Thackston