APOD: Another Nearby Supernova in the... (2011 Jun 05)

[APOD Robot]

Another Nearby Supernova in the Whirlpool Galaxy

Explanation: One of the brightest supernovas in recent years has just been recorded in the nearby Whirlpool galaxy (M51). Surprisingly, a seemingly similar supernova was recorded in M51 during 2005, following yet another one that occurred in 1994. Three supernovas in 17 years is a lot for single galaxy, and reasons for the supernova surge in M51 are being debated. Pictured above are two images of M51 taken with a small telescope: one taken on May 30 that does not show the supernova, and one taken on June 2 which does. The June 2 image is one of the first images reported to contain the supernova. The images are blinked to show the location of the exploded star. Although most supernovas follow classic brightness patterns, the precise brightening and dimming pattern of this or any supernova is hard to predict in advance and can tell astronomers much about what is happening. Currently, the M51 supernova, designated SN 2011dh, is still bright enough to follow with a small telescope. Therefore, sky enthusiasts are encouraged to image the Whirlpool galaxy as often as possible to fill in time gaps left by intermittent observations made by the world's most powerful telescopes. Views of the developing supernova are being uploaded here.

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[Guest]

Something that is common knowledge, but it always strikes me each time I see it. Like in this APOD, with its descriptions of the relatively recently photographed supernovas. As we read, it is as if this supernova, just photographed, just occurred, almost right before our very eyes, when actually, in fact, these supernovas happened about 31 million years ago, relative to the distance of M51, and to the speed of light.

Sometimes it is pretty easy to forget that we are actually seeing into the very distant past, as if we were looking through the windows of a "time machine", as we "observe" into the far reaches of this great universe, with our various optics and sensors.

The APOD site is a tremendous asset! Thanks so very much

Robert

[Ann]

Good choice. The supernova may have happened 31 million years ago, but to us it is the latest news, and the latest news is always a good choice for any APOD.

This reminds me of an old ballad that was popular in Sweden in 1872. The lyrics went like this: Have you heard of the horrible thing/ that is true 'casue it happened right now/ how the king(!) of North America/ was shot - yes, shot right through and through.

Abraham Lincoln was shot in 1865, but it took five years for the news to "percolate" down into the minds of the general public in Sweden, on the other side of the Atlantic. News didn't travel instantly in the 1860s, and it still doesn't, although today it may travel at pretty much the speed of light. That still means we have to wait for 31 million years for the news of the latest supernova in M51 to reach us.

Ann

[Star*Hopper]

In the presentations I used to give at our local planetarium, one of them focused on the speed of light & vastness of space. For the ending of that particular show, I used the line:
"I mentioned the Andromeda galaxy earlier - and that it's the farthest object we can see with the naked eye. I've always found it somewhat humbling to know we can go outside on a clear night and if we know ju-u-ust where to look" (circling where M31 'lives' on the dome with my laser pointer), "the light photons that are entering our eyes were created over 20-THOUSAND CENTURIES before humans first walked on the Earth."

And I still do.

[DLH]

"Pictured above are two images of M51..."

I see only one image.

[owlice]

The images are blinked to show the location of the exploded star.

One image shows the galaxy before the supernova, the other shows the galaxy after the supernova explosion.

[Chris Peterson]

Something that is common knowledge, but it always strikes me each time I see it. Like in this APOD, with its descriptions of the relatively recently photographed supernovas. As we read, it is as if this supernova, just photographed, just occurred, almost right before our very eyes, when actually, in fact, these supernovas happened about 31 million years ago, relative to the distance of M51, and to the speed of light.

That is true in a sense. But modern physics has a more complex way of dealing with the idea of now (or of simultaneity). Since the speed of information transfer is limited to c, the "now" of an event is generally defined by a light cone- that is, "now" for some event at some point is when a photon from that event could reach that point. This all has to do with the concept of space-time, as well.

In a very real sense, in the sense most often used by physicists, this supernova happened a few days ago, not 31 million years ago.

[biddie67]

I looked for a picture of M51 that showed the locations of all 3 supernovas in that galaxy - were they scattered throughout or in the same general area of M51?

[NoelC]

I see only one image.

Do you not see it blinking between the two images?

If so, your browser is failing to animate the GIF file. You may wish to try a different browser.

-Noel

[Wolf kotenberg]

with any luck, Eta carinae will also bathe us in starlight in my lifetime. Gotta move to Brazil, though.

[BobStein-VisiBone]

Excellent points Guest and Ann. A trivial Wikipedia-induced correction: latest estimates are that M51 is 23 ± 4 million light-years distant from Earth.

Re "reasons for the supernova surge in M51 are being debated." Hunh? Is there any credible reason to believe there IS a surge at all? Other than in some woowoo sense, due to our entirely coincidental viewpoint that is. Here's the thing, even if we are viewing M51 perfectly perpendicularly, there is still great variation in the distance from Earth to its individual stars. If M51 is 1:100 shaped (as is estimated for the Milky Way) then because it is 76,000 ly in diameter it is about 760 ly thick. So I don't believe we can even know the distance to these "three supernovas in 17 years" with an accuracy of 760 ly. Hence the events are likely to be randomly distributed over at least 760 years and probably much wider.

Also from Wikipedia: "supernovae are relatively rare events within a galaxy, occurring about once every 50 years in the Milky Way"

So 3 supernova in 760+ years is no surge.

Unless um Wikipedia is wrong and supernova are more common...

[Chris Peterson]

So 3 supernova in 760+ years is no surge.

As noted previously, simultaneity is a tricky concept. The events are not separated in time by 760 years, but by 17 years. It doesn't matter how far apart they lie, or how many light years away. Three supernovas in a single galaxy in 17 years is a statistical oddity- but I think that's all it is. These things happen (consider the unlikelihood of Brahe's and Kepler's supernovas in 1572 and 1604). Supernovas can probably be considered as occurring according to Poisson statistics, and that means that every now and then you'll see something that we would call a "cluster", even though there is no causal connection between them.

[Ann]

Three supernovas in a single galaxy in 17 years is a statistical oddity- but I think that's all it is. These things happen (consider the unlikelihood of Brahe's and Kepler's supernovas in 1572 and 1604). Supernovas can probably be considered as occurring according to Poisson statistics, and that means that every now and then you'll see something that we would call a "cluster", even though there is no causal connection between them.

I think so, too.

Also bear in mind that M51 is a largish galaxy with a lot of star formation. Star formation has clearly been going on for quite some time here, which is obvious from the many different generations that the galaxy contains. And because star formation in M51 is vigorous, and has been vigorous for a relatively long time, the statistical odds for a "cluster" of supernovae occurring in this galaxy is much greater than in a large galaxy with a much lower rate of star formation, like M88, or in a much smaller galaxy with a high rate of star formation, like M33.

This doesn't explain why there have been so relatively few supernovae in M101. But, indeed, we are talking statistical flukes here.

Ann

[BobStein-VisiBone]

The events are not separated in time by 760 years, but by 17 years.

Ah, true of observations from Earth. But observations of these same three supernovae from other points in the universe must definitely be separated on the order of 76,000 years (the time it takes light to cross the diameter of M51). My point is that our viewpoint is a major randomizing factor in the oddity of this statistic. So a surge in (Earth) observations must have no more "reason" (the article's word) than any other rare pattern in randomness.

Now I'm curious if it was even a surge of observations. Does anyone know when we started to be able to observe a supernova in M51? Certainly not in Brahe's and Kepler's time. Their supernovae were in The Milky Way, correct? If it was say 20 years ago then this may less a statistical oddity, and more an indication of a higher rate of supernova occurrence, at least in M51.

[rguyg]

sh sh.. I was just told by aliens that 200 Supernova's occurred within ten years over 4 millon years ago in the Pin Wheel

I like the way we talk about what just happened; like this newly found Supernova. Just to think what's happened since..

[Chris Peterson]

Ah, true of observations from Earth. But observations of these same three supernovae from other points in the universe must definitely be separated on the order of 76,000 years. My point is that our viewpoint is a major factor in the oddity of this statistic.

And my point was that there's nothing peculiar about viewpoint. We assess the frequency of supernovas in other galaxies only by when we observe them to occur. There is no other metric of timing used.

Does anyone know when we started to be able to observe a supernova in M51? (Certainly not in Brahe's and Kepler's time. Their supernovae were in The Milky Way, correct?) If it was say 20 years ago then this may not be a statistical oddity, it may indicate a higher rate of supernova occurrence, at least in M51.

Only three supernovas have been observed in M51: 1994, 2005, and 2011. M51 has been under close enough observation to note a supernova for at least 100 years. And of course, unless there was something very peculiar about M51 (which there doesn't seem to be), we should expect its supernova statistics to be similar to other galaxies of its type, for which we must have many thousands of years of total observation time in a statistical sense.

[Star*Hopper]

sh sh.. I was just told by aliens that 200 Supernova's occurred within ten years over 4 millon years ago in the Pin Wheel
I like the way we talk about what just happened; like this newly found Supernova. Just to think what's happened since..

We can settle this. I checked the data logs of the SWIFT satellite for all supernovae prior to 1994 and they were absolutely blank. So obviously there haven't been any others.

[rjtonnis]

What is the other light at about 5 o'clock from the supernova that is moving relative to the other light sources?

[Wolf kotenberg]

I just had a thought. We, as insignifican residents in the vey large sea sent out puny messages in golden disks to some aliens out there and they turn around and send us gynormous explosions. I think prof Hawking could very well been right, maybe we don't want these denizens around here.

[Ann]

What is the other light at about 5 o'clock from the supernova that is moving relative to the other light sources?

I don't think anything is moving. You see two images, one with the supernova, the other one without. The image without the supernova is a bit brighter than the other one, so the stars look brighter there. Today's APOD is rapidly "blinking" between the two images, creating a slight feeling of movement, which is an illusion.

Ann

[geek]

.

Aliens are Harvesting heavy elements by causing those nova clusters.

Just wait til Andromeda gets here.

.

[Wolf Kotenberg]

That is going to be like us insignificant ones having our own private big Bang

[neufer]

<<Recent simulations bear out that M51's spiral structure was caused by NGC 5195 passing through the main disk of M51 about 500 to 600 million years ago. In this model, NGC 5195 came from behind M51 through the disk towards the observer and made another disk crossing as recently as 50 to 100 Myrs ago until it is where we observe it to be now, slightly behind M51. Induced spiral structure in the larger galaxy isn't the only effect of the interaction. Significant compression of hydrogen gas occurs that leads to the development of starbirth regions. In pictures of M51 these show up as the bright blue 'knots' throughout the spiral arms.>>

Type II supernova in M51 were probably induced by NGC 5195:
http://asterisk.apod.com/viewtopic.php? ... 54#p124054

[bystander]

Type II supernova in M51 were probably induced by NGC 5195:

A type II supernova … results from the rapid collapse and violent explosion of a massive star. …

When the mass of the inert core exceeds the Chandrasekhar limit of about 1.44 solar masses, electron degeneracy alone is no longer sufficient to counter gravity. A cataclysmic implosion takes place within seconds, … The collapse is halted by neutron degeneracy, causing the implosion to bounce outward. The energy of this expanding shock wave is sufficient to detach the surrounding stellar material, forming a supernova explosion, … Because of the underlying mechanism, the resulting variable star is also described as a core-collapse supernova.

I'm not sure I understand how this is induced by galactic interaction. Seems to me to be simply a property of massive stars. Unless you are saying the birth of these massive stars were caused by the interaction, but that's somewhat different than saying the supernova were induced by NGC 5195.

[neufer]

A type II supernova … results from the rapid collapse and violent explosion of a massive star. …

When the mass of the inert core exceeds the Chandrasekhar limit of about 1.44 solar masses, electron degeneracy alone is no longer sufficient to counter gravity. A cataclysmic implosion takes place within seconds, … The collapse is halted by neutron degeneracy, causing the implosion to bounce outward. The energy of this expanding shock wave is sufficient to detach the surrounding stellar material, forming a supernova explosion, … Because of the underlying mechanism, the resulting variable star is also described as a core-collapse supernova.

I'm not sure I understand how this is induced by galactic interaction. Seems to me to be simply a property of massive stars. Unless you are saying the birth of these massive stars were caused by the interaction, but that's somewhat different than saying the supernova were induced by NGC 5195.

• 1) Massive stars have short lives.
  
  2) NGC 5195 has recently induced massive star formation which has lead to Type II Supernovae.