View a gallery of other shimmering supernova remnants (move your mouse over the images to read the captions).
A supernova remnant near the centre of the Milky Way has turned out to be the youngest known in our galaxy, plugging a puzzling gap in the astronomical record.
Known as G1.9+0.3, the remnant lies about 28,000 light years away. It was first identified as a ring-like supernova remnant in the early 1980s. Now, observations by NASA's Chandra X-ray Observatory and the Very Large Array in New Mexico have shown that the diameter of the glowing gas shell has expanded by 16 per cent over the past 22 years.
If the speed of expansion is roughly constant, then the remnant is only about 140 years old, in the Earth's time frame, making it the youngest in the Milky Way. Previously, the most recent supernova was thought to have occurred around the year 1680, creating the ghostly remnant Cassiopeia A.
The latest supernova would not have been visible to 19th-century astronomers because it occurred in dense gas and dust near the galactic centre. "The best telescopes at that time would not have been able to collect enough light to see it," says Stephen Reynolds of North Carolina State University in Raleigh, who led the Chandra study and revealed the results this week. "But the remnant shines in radio waves and X-rays, so X-ray and radio telescopes can see it."
The discovery of the young remnant helps plug a mysterious gap in our galaxy's supernova history. Measurements of supernova rates in other galaxies suggest that about three supernovae should rattle the Milky Way every century. If so, our galaxy should contain roughly 10 remnants younger than Cassiopeia A. Many of the "missing" remnants may never turn up, Reynolds suspects.
Some stars might explode and leave no trace, perhaps because the star somehow creates a bubble of empty space around it before exploding. The shock wave from the blast would then expand in such a low-density gas that its glow would be invisible.
Cosmology - Keep up with the latest ideas in our special report.
By Jdl
Wed May 14 19:56:54 BST 2008
"...the diameter of the glowing gas shell has expanded by 16 per cent over the past 22 years. If the speed of expansion is roughly constant, then the remnant is only about 140 years old..."By Dave
Thu May 15 04:01:01 BST 2008
Newton's first law.By Equilibrium
Thu May 15 06:42:39 BST 2008
If the remnant is at 28,000 light years distance, then it must have been atleast 28,000 years, because that is how long it would take light to reach us. But the article says, 140 years.By William
Thu May 15 08:21:25 BST 2008
I was scratching my head over exactly the same question Equilibrium. Would someone more knowledgeable please explain how we can be viewing an even 28 000 light years away only 140 years after it occurred?By Pamela Aguila Catilo
Thu May 15 08:26:20 BST 2008
Some article say the star was about 26,000 light-years away. So the actual explosion occurred about 26,000 years ago, and the light from the blast traveled that long to arrive at Earth no more than 150 years ago.By Michael Marshall, Online Editorial Assistant
Thu May 15 10:25:02 BST 2008
Hi Equilibrium, and everyone else confused by this. This may have been a little unclear. What we were trying to get across was that the light from the supernova first reached us 140 years ago, so that's when (in theory at least) we could first have seen it. But of course, the supernova is 28,000 light years away, meaning it actually occurred around 28,000 years ago. I've inserted an extra phrase to clarify this.By Erte
Thu May 15 10:57:19 BST 2008
You write "Some stars might explode and leave no trace". Shouldn't this apply also to supernovae in other galaxies, and have some effect on the expected rate in our galaxy?By Erte
Thu May 15 12:29:21 BST 2008
Well, eh.., no.., The supernovae in other galaxies are all assumed to be visible, but some traces in our galaxy are not. (Did I get it right now?)By Eric Kvaalen
Fri May 16 22:32:12 BST 2008
We see most galaxies obliquely, whereas we see the Milky Way edgewise. Therefore, for many stars in the Milky Way, their light has to pass through hundreds of thousands of light-years of dust clouds to get to us, but the light from stars in other galaxies only has to go through a relatively short distance in those galaxies before it is out of the galaxy and continues through fairly empty space till it gets to us. This explains why many supernovae "in our own backyard" are harder to see than ones in distant galaxies.All comments should respect the New Scientist House Rules. If you think a particular comment breaks these rules then please use the "Report" link in that comment to report it to us.
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