TOPICS > Science

Supernova Burns Bright in a Galaxy Not So Far Away

September 7, 2011 at 12:00 AM EST
Lawrence Berkeley National Laboratory scientists recently discovered a supernova about 21 million light years away in the Pinwheel Galaxy. Jeffrey Brown and Peter Nugent, who found the brightest and closest supernova in decades, discuss how the dying star could prove to be "a real treat" for Northern hemisphere stargazers.
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GWEN IFILL: Finally tonight, a supernova burns bright in the night sky.

Jeffrey Brown has the story.

JEFFREY BROWN: In a galaxy not so far away, at least in astronomical terms, the death of a star has created a bright light in the sky. When scientists looked at the Pinwheel Galaxy, about 21 million light years away, on Aug. 22, all looked normal. But over the next two days, a light emerged.

It was a supernova, one of the brightest and closest to us in decades. And, weather permitting, you can see it this week from your own backyard.

Peter Nugent of the Lawrence Berkeley National Lab discovered the supernova and joins us now.

Well, welcome to you.

So, we’re seeing this now, but it happened rather a long time ago, in fact, right?

PETER NUGENT, Lawrence Berkeley National Laboratory: Yes.

When something is 21 million light years away, that means it’s taken 21 million years for that light to get to us. So it has been a long, long time ago in a galaxy far away.

JEFFREY BROWN: And what is it? Remind us of what a supernova is.

PETER NUGENT: So, the supernova that we’re looking at here is the death of a star.

Supernova come in all varieties and shape, from stars that blow up that are ten, 100 times bigger than our sun, but this one actually is a star called a carbon-oxygen white dwarf, which is about the size of the planet Earth.

JEFFREY BROWN: And what makes this one so remarkable?

PETER NUGENT: Well, this supernova is incredible because we caught it so early and it’s going to get so bright that astronomers will be able to use almost any of the telescopes on any of the major observatories in the world to look at it.

This supernova is also one of the supernova that we use to measure distances to other galaxies. So, in that sense, we will have another way of checking out how the universe is accelerating.

JEFFREY BROWN: Well, I want to come back to that — that second thought, but in terms of finding it, how exactly does one find a supernova? This is something you’re always on the lookout for?

PETER NUGENT: So, yes, the collaboration — I belong to the Palomar Transient Factory — takes digital images every night that’s clear down outside of San Diego, about 600 square degrees of sky.

To give you an idea, the moon is only about a half-a-square-degree in size. And we subtract these images that we take each night from images that we have taken weeks, months, or even years before, and we look for things that go bump.

It’s a very difficult process involving a lot of computers to subtract the data and then also tell us which ones are the most interesting types of transient astrophysical objects to look at.

JEFFREY BROWN: Now, I gather another thing that makes this interesting is that you got it in your sights at a point just hours after it exploded, right? Explain that.

PETER NUGENT: Yes.

So the observations that we had taken the night before had shown nothing there at all, to a level about 10,000 times fainter than the human eye can see. And then it increased in brightness the next night by well over a factor of 100. And, so, we knew we had caught it at least within a 24-hour period, and it now looks like we caught it just several hours after it exploded.

JEFFREY BROWN: All right, so, now that we know that, come back to this thought you raised before about explaining the scientific value of something like this.

What exactly is it that this is useful for in understanding about the universe?

PETER NUGENT: So type 1A supernova are unique in that they’re a gazillion-watt light bull that we actually know how bright it is to a small percent.

So by looking and studying these supernova in galaxies at different distances, we can actually measure the distance by recording how much light we receive at the telescope, and then remembering the fact that that light drops off like the square of the distance.

And so supernova that are this bright — and, by the way, this supernova is going to be as bright as all the stars combined in the Pinwheel Galaxy when it reaches peak brightness — we can see these, not 21 million light years away, but eight billion light years away.

So we can see them very shortly after the universe was created, and then we can measure how the distances to objects have changed over that time.

JEFFREY BROWN: Now, you have, I guess — I hope you have piqued people’s interest and talked about the brightness here. How exactly and when and where do people see it?

PETER NUGENT: So this supernova is going to be one of the brightest supernova in the last 40 years, save for 87A, which was in the Southern Hemisphere. So this is a real treat for us in the Northern Hemisphere.

It’s going to reach what we call 10th magnitude in astronomical terms, which is about one-one-hundredth as faint as the human eye can see, but reachable with binoculars, a good pair like 20x80s or 25x100s, or a small telescope, a six-to-eight-inch telescope.

The best time to look for it is shortly after it peaks, which is this weekend. It will still stay relatively bright for a couple weeks, but the full moon occurs on September 12. So, if we wait until just until after that, the moon will rise later and later in the evening, and just after sunset, the Big Dipper will be at its highest point.

So that’s when the skies will be the darkest and the supernova will be at its most easily accessible point in the sky to see.

JEFFREY BROWN: So, a good pair of binoculars; we don’t need your telescope or the Hubble at home, right?

PETER NUGENT: No, no, just the simple six-inch telescope or a very good pair of binoculars, and you should be able to spot it easily.

JEFFREY BROWN: All right.

Peter Nugent of the Lawrence Berkeley National Lab, thanks so much.

PETER NUGENT: Thank you for having me.