A successor to Hubble

We look at the telescope that's hoping to fill Hubble's sizable boots.
08 September 2020

Interview with 

Dominic Benford, NASA


The Milky Way galaxy.


Adam Murphy’s been looking at the Nancy Grace Roman telescope, a project that’s set to be a successor to the Hubble space telescope, one of the most famous telescopes of all time, with project scientist at NASA, Dominic Benford…

Adam - The Hubble space telescope is iconic. Sent into space in 1990, the images Hubble sent back are amazing and captured the imagination of millions, but it is 30 years old. It's getting on a bit. So a new generation of telescopes are being planned to attempt to fill Hubble's sizable boots. One of them is the Nancy Grace Roman telescope named for the first female executive of NASA, this telescope will seek to continue Hubble's legacy. I spoke to Dominic Benford, programme scientist for the telescope.

Dominic - We have designed the Roman space telescope to be able to conduct the kind of survey that astronomers haven't been able to do with any of the sets of tools they have had during the past generations. And that is to focus on being able to take very sharp images of wide areas of the sky with tremendous sensitivity, being able to see very, very distant objects and also to be optimised in the near infrared, which is wavelengths just slightly longer than what our eyes are sensitive to, because the near infrared wavelengths penetrate dust better, so it will allow us to see further into our own galaxy. And also, we'll be able to see the red shifted light from very, very distant galaxies. So it enables us to see farther. And so this combination of being able to see far into our own galaxy and far out into other galaxies, and to be able to do this very quickly, very efficiently, means that we can start conducting surveys where instead of looking at a few objects, a few galaxies or a few stars, we can start studying, monitoring and understanding millions or even hundreds of millions of galaxies, millions of stars, all the same time, to be able to conduct surveys that are more demographic where we really understand the whole, the entirety of these aspects of the universe all at once.

Adam - That means the Nancy Grace Roman telescope is designed to be more like a wide angle lens for space instead of a zoom lens. But how is it going to carry out its mission?

Dominic - The Roman space telescope surveys are designed to be able to answer pressing questions, both in cosmology and in exoplanet science. For cosmology, we will take a number of surveys of the distant universe so that we can understand the distribution of galaxies and how the universe has expanded over cosmic time. From a time when the universe was only a few billion years old to the present, when the universe is now 13.7 billion years old. And through watching the way the galaxies evolve, how they form, how they move towards and away from each other, we can infer the effects of dark matter, which is a large unknown component of the mass of the universe and dark energy, which is a recently discovered mysterious force that appears to be pushing the universe apart and therefore pushing all the matter in the universe away from all the other matter. And that we'll be able to take definitive measurements of this kind to understand the effects of these so that we might understand better the fundamental physics that drives the universe in its evolution.

Adam - And what about our own galaxy? What can be achieved when the telescope is pointed to the centre of the Milky Way?

Dominic - We plan on conducting a survey where we will look at the galactic bulge of our own Milky Way, which is where most of the stars in the galaxy can be found. So we'll stare at a wide patch of our Milky Way galaxy, tracking the brightnesses of millions and millions of stars, taking images every roughly 15 minutes over the course of many, many months. And we will look for the chance encounter when a star happens to pass in front of some other background star. And when it does this, because of general relativity, the light from the background star will be focused much like a lens by the foreground star and focused on us, as the stars move slowly through the galaxy. And that brightening is something that we can measure.

And by measuring the brightening with time, we'll be able to infer what the foreground star was like. And if the foreground star has planets, we'll see brightening from those as well. And in fact, even if these planets have large moons, we'll be able to see the brightening from the moons of the planets around those stars. And by doing this with millions of stars, we'll be able to track enough planets, thousands we think, of planets around other stars that we'll be able to make a complete demographic census of what planetary systems are like. In our own solar system we have the eight planets and that we can see essentially all the planets like that around another star, maybe not mercury because it's very small and close in, but certainly every other planet, even planets like Mars, we will be able to detect around such stars and be able to answer the question definitively, "is our solar system common in the galaxy? Is it rare in the galaxy? Or it may even be unique". And so doing this, we will understand our own place in the universe and how our source system got to be the way it is.


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