Supernova Precursor Discovered in Spiral Galaxy NGC 2397

by Ian O'Neill on April 5, 2008

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It’s a bit like trying to find a needle in a haystack when looking for a star in a galaxy. Although hard to do, astronomers using images from the Hubble Space Telescope (HST) are doing just that, trying to find stars before they explode as supernovae. In 2006, supernova SN 2006bc was spotted in spiral galaxy NGC 2397, so astronomers got to work, sifting through previous images taken by the HST. They found that star, in the rising stage of brightness as it exploded. Usually we don’t get to see this stage of a supernova, as we can’t predict which star is going to blow. But retracing years of HST observational data, scientists are able to piece together the cosmic forensic evidence and see the star before it died…

SN 2006bc was seen in the spiral galaxy NGC 2397, located nearly 60 million light years from the Milky Way, back in 2006. There was no warning or any indication that that star was going to blow in that galaxy (after all, there’s a lot out there), but Hubble’s Advanced Camera for Surveys (ACS) captured the galaxy after it happened. So astronomers watched the afterglow of the event. While a lot of good science can be done by analysing the remnants of a supernova, wouldn’t it be great to see a star before it explodes? Perhaps then we can analyse the emissions from an unstable star before it dies…

Predicting cosmic events is no new thing, and much effort is being put into various forecasting techniques. A few examples include:

  • Solar radiation: The main focus for solar physicists is to predict “space weather” to help protect us against the dangerous onslaught of high energy particles (particularly solar flares).
  • Detecting supernova neutrinos: An “early warning” system is already in place to detect the neutrinos that are blasted from a star’s core at the moment of a star’s collapse (leading to a supernova). The SuperNova Early Warning System (SNEWS) has been set up to detect these neutrinos.
  • Gamma ray bursts (GRBs): The Polish “Pi of the Sky” GRB detector is an array of cameras looking out for optical flashes (or transients) in the night sky above the Chilean mountains. Combined with NASA’s Swift gamma ray observatory in orbit, the burst is detected, immediately signalling other observatories to watch the event.

The above examples usually detect the sudden event of a solar flare, GRB or surge of neutrinos right at the point of initiation. Fortunately for solar physicists, we have a vast amount of high-spatial and high-temporal resolution data about our closest star. Should a flare be launched, we can “rewind the tape” and see the location of flare initiation and work out the conditions before the flare was launched. From this, we are able to be better informed and possibly predict where the next flare will be launched from. Supernova astronomers aren’t so lucky. The cosmos is a big place after all, only a tiny proportion of the night sky has been observed in any great detail, and the chances that the same region has been imaged more than once at high resolution are few and far between.

Although the chances are slim, researchers from Queen’s University Belfast in Northern Ireland, led by Professor Stephen J. Smartt used Hubble Space Telescope (HST) images to “rewind the tape” before supernova SN 2006bc occurred. By confining their search for “pre-supernova” stars in local galaxies, there was a better chance of studying galaxies that have been imaged at high resolution and imaged more than once in the past. SN 2006bc turned out to be the perfect candidate.

The group has done this before. Of the six precursor stars discovered to date, Smartt’s team found five of them. From their analysis, it is hoped that the characteristics of a star before it dies can be worked out as the conditions for a supernova to occur is poorly understood.

After ten years of surveying, the group presented their discoveries of supernova precursor stars at this year’s National Astronomy Meeting 2008 in Belfast, last week. It appears that stars with masses as low as seven times the size of our Sun can explode as supernovae. They go on to hypothesise that the massive stars may not explode as supernovae and may just die through collapse and form as a black hole. The emission from such an event may be too faint to observe and the most energetic supernovae may be restricted to the smaller stars.

However, six supernova precursor stars are not a large number to make any big conclusions quite yet, but it is a big step in the right direction to better understand the mechanisms at work in a star just about to explode…

Source: ESA

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Hello! My name is Ian O'Neill and I've been writing for the Universe Today since December 2007. I am a solar physics doctor, but my space interests are wide-ranging. Since becoming a science writer I have been drawn to the more extreme astrophysics concepts (like black hole dynamics), high energy physics (getting excited about the LHC!) and general space colonization efforts. I am also heavily involved with the Mars Homestead project (run by the Mars Foundation), an international organization to advance our settlement concepts on Mars. I also run my own space physics blog: Astroengine.com, be sure to check it out!

Yael Dragwyla April 5, 2008 at 11:02 PM

I wonder if somewhere out there, on a galaxy well south of the Milky Way, millions of years from now, astronomers on a world in that galaxy will observe the gigantic explosion that is Eta Carinae going supernovae at last, and wonder if any stars near Eta Car harbored life that somehow managed to flee the fire in time.

Doug Van Houten April 5, 2008 at 7:37 PM

I just can’t help to hope there isn’t a planet, with life, that will be affected, and if so, they have the technology to travel else where.

JERRY April 5, 2008 at 10:02 PM

WITH THE HUNDERDS OFTHOUANDS OF
GALAXIES I HAVE NO DOUBT THERE IS LIFE.THE NUMBERS SAY IT FOR THEM SELFS BUT WE DO NOT HAVE THE TECHNOLOGY YET TO KNOW WHO MAY BE AFFECTED OR NOT.EVEN IF THEY WOULD HAVE THE TECHNOLOGY TO GO FROM ONE PLACE TO AN OTHER WITH THE TIME IT WOULD TAKE I DO NOT KNOW HOW IT COULD BE DONE,IF EVER.

pradipta kumar mohapatra April 5, 2008 at 11:50 PM

From the ancestral time the world space research established on blind theory. We although demand that we have discovered lots of mysteries viz. milk ways, galaxies, nebulas, white drafts, black holes etcs., in real they are creation of space mirror. SPACE MIRROR is the truth and hidden mystery of the space. Since we are unknown about space mirror, our research has diverted from original truth and we have spent lots of time and money behind the false truth.
Therefore it invites to visit http://www.spacemirrormystery.com and for prosperous space research.

paul victor April 6, 2008 at 1:05 PM

nice theory, but you need to bone up on your english.

Max Vondel April 6, 2008 at 7:33 PM

I wouldn’t believe Pradipta, Pure Indian Mysticism and money making, $100- To find out the secret, $1000- to find out the lot. This is not a commercial site, better get back to your Indian telemarketing job!!!!!

alokmohan April 7, 2008 at 12:19 AM

Padipta we are both fom India.You may learn supernova.When a star of more than 1.4 solar mass implodes we get supenova.1.4 is Chandrasekhar limit.He was of Indian origin.Read white dwarf ,it b is Indian science.Chana found it out.

Ignoramus April 7, 2008 at 6:10 AM

paul victor says “nice theory, but you need to bone up on your english”.
How is your Urdu?
Pretentious prick!

Harin April 9, 2008 at 11:11 PM

Max, Indian astronomy far preceded Western scientific thinking. THere is vast ancient knowledge into subjects like astronomy, math etc.

I presume you have been recently laid off from your job and replaced by an Indian who does the same job better, faster and for a lesser pay.

Given that this guy Pradipta appears a nutcase, but please can you ignore him and get on with your life? And try to get a job soon.

pradipta April 14, 2008 at 6:48 AM

Mirror reflects frontier. Mirror functions like a wall. There is nothing ahead of mirror but reflection makes lively atmosphere into mirror. If two mirrors face each other in parallel position the concerned area between mirrors is converted to a biggest atmosphere because the concerned area reflected unlimitedly as front side and backside into each mirror frequently. Space mirror is based on above rule and we are unknown about space mirror. From sun the objects of area 225 million kilometer to 300 million kilometer of solar system reflects unlimitedly, we find a very deep space and through giant telescopes we watch mystery after mystery. Telescope enlarges view not closes near view. Following may clear the concept “A visitor of a desert often find mirage. If he moves mirage also moves. He can never reach near the mirage. If he tries he can see enlarge view of mirage as smoky atmosphere through a telescopic instrument”.
Giant telescope like Hubble and others may be the milestone of our technology but it can not help the real space research since we search the unnatural truth light years away. Unnatural truth also includes supernova and white dwarf.
Which Jupiter we observe at the distance of 772million kilometer from sun is mere image of real Jupiter; appears to us as 12 times bigger than earth. The real distance between real Jupiter to sun is 238millon kilometer and in size it is only 1.7 times bigger than earth. From calculation it appears that real Saturn, Uranus & Neptune are all smaller than earth although we observe there images as bigger than earth.
Watch mirror and find out truth and make the space science grand better imposing your genius mind.

pradipta April 14, 2008 at 6:59 AM

I am really weak in English. Thanks for suggestion.

Dutch January 11, 2009 at 10:16 PM

Wow that makes no sense at all. You offer exactly nothing in the terms of theory, proof or anything else for that matter, Pradipta. Except of course for a shameless rip-off of peoples hard-earned money. What you say is plainly ridiculous and I cannot imagine that an advocate, as you claim to be on that website, would go ahead and so blatantly embarrass himself/herself like that.

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