Two supernovae, no waiting

By Phil Plait | November 20, 2006 11:18 pm

Sometimes, stars blow up.

The circumstances have to be just right. Sometimes, a star is really, really massive — like 40 or more times the mass ofthe Sun — and it ends its life with a bang. Its life was short, maybe a couple of million years, but it burned hot, and died hard. That kind is called a Type II supernova.

Other times, a star like the Sun lives a long time, blows off its outer layers, and becomes a dense, hot, white dwarf. If it orbits another star, that second star might lose matter which accumulates on the white dwarf. The immense gravity of the dwarf squeezes that gas, and if it piles up just right, BANG! It fuses all at once like an enormous bomb. The star rips itself to shreds. That’s a Type I supernova. Note that the star has to be pretty old for it to happen: one of the two stars started out like the Sun, but had to go through its whole life first, maybe a billion years or more. Type I supernovae are from old stars.

Weirdly, both kinds of supernova put out about the same amount of energy, even though they are very different events. The energy is staggering: about a million million million times the energy the Sun puts out. Yikes.

Anyway, in a typical galaxy, you get roughly one supernova per century. It depends on a lot of things, but hey– close enough. Some galaxies are underachievers (we haven’t seen one on our own Galaxy since the 1600s!), and others are brown-nosers, blowing stars up left and right.

Meet NGC 1316.

By any standard, NGC 1316 is a weirdo. It’s oddly shaped, sorta like a spiral, but sorta like an elliptical. It has a smaller galaxy nearby with which it appears to be interacting. It’s a huge radio source. It has weird streamers of dust running through it, which you can see in this Hubble image:

It’s weird for another reason. Up until this year, it is one of the very few galaxies which have been seen to host more than supernova. Then, in June 2006, another one went off, raising the total known exploding stars in the galaxy to three. All in just 26 years, which is quite a feat.

Then, in November of 2006, a fourth was discovered!

The Swift satellite, launched two years ago yesterday in 2004, has as part of its mission the task of observing new, bright supernovae. It took this image just the other day:

The two supernova are above and to the left and right of center (the object farther to the left is a star in our own Galaxy). The supernova on the right (SN2006dd) was the first one from June, and the one on the left (SN2006mr) is the newer one, first seen on November 5. The image from Swift is from its Ultraviolet/Optical Telescope. It has an X-ray telescope as well, and I expect we’ll see some X-ray images eventually. That should be cool.

Two simultaneous supernovae is rare, but not unheard of. It’s happened in NGC 772 and NGC 664, for example. But it’s still interesting.

Even more interesting: both of the supernovae in NGC 1316 have been determined to be Type I! Sometimes, in peculiar galaxies, there can be a burst of star formation, which — after a couple of million years — leads to lots of Type II supernovae. But to see more than one Type I is a little weird, since they take so long to "cook". I wouldn’t say there is anything cosmic in the timing (haha); more that it’s just pretty nifty.

But it’s also cool that this is a relatively nearby galaxy. Type I’s are used to get the distance to very distant galaxies, and we need to understand them as well as we can to do that. The more that happen nearby the easier it is to study them. So this may turn out to be a real boon to astronomers.

CATEGORIZED UNDER: Astronomy, Cool stuff, NASA, Science

Comments (16)

  1. bswift

    The interesting thing about these simultaneous supernovae like this, is that the SNe likely aren’t simultaneous in their host galaxy. The host systems are thousands of light years apart, occurring thousands of years apart from each other, only appearing simultaneous to us (or anyone along our line of sight, for that matter).

  2. This is typical, just like waiting for a bus. You wait centuries and then four turn up at once.

  3. Gary Ansorge

    Gee, looks like a drunk I once knew,,,

    With the distance between them, looks like we should be able to obtain a very accurate distance determination, which really helps with analyzing the total energy distribution of these type 1As.

    Way cool!!!

    GAry 7

  4. Melusine

    Off-topic: the Google ad was freaking out, but I saved it. Sometimes the ads are quite good.

    I don’t think it’s nice to talk about NGC 1316 that way, but it’s fascinating information nevertheless. The numbers are mind-boggling.

  5. ioresult

    Don’t white dwarfs have to pass through a series of novae before finally going through the type I supernova when it collapses into a neutron star?

  6. ThePolynomial

    Naive question: How close would a type I supernova need to be to be dangerous? In the grand list of doomsday scenarios, I’ve never heard “nearest white dwarf pounds us with radiation.” I have heard “supernova blows up and we have 24 hour daylight for a while.” How do all of these orders of magnitude match up? Thanks.

  7. jackd

    Wasn’t the use of Type Ia supernovae as ‘standard candles’ questioned recently? What’s the latest status?

  8. Lauren

    I found this article to being really ironic. I’m a freshmad astronomy/astrophysics major and I decided to take a break from some homework (I was reading about supernovae and white stars) to check out BA, and here’s an article on the same thing as the chapter in my book. Amazing. I find supernovae amazing. I few seconds completely undo something that took millions of years to make. It’s really cool that they found two Type 1 right next to each other.

  9. Glenn Becker

    There’s no chance this is a “doubled by gravitational lensing” of a single event, is there? That’s a naive question, I guess …

  10. Peter Barrett

    So there’s no chance that a war between two alien empires is reaching the stage where they’re blowing up each others’ stars? :-)

  11. And that we are next 😮

  12. mungascr

    The nearest (eventual) type I supernova may be the brightest (apparent mag) star inour skies – Sirius. Its got a white dwarf star orbiting an A-type main-sequence star, a star that’s going to turn into a red giant soon-ish , wellastronomicalyspeaking anyhow. Its about 8 light years way – one of thecloests star systems to ours.

    I’ve read an SF novel where Sirius B actually errupts into a supernova – its got some very good science and a science-versus-religion theme too so I reckon the BA and others here would enjoy it if they haven’t read it already. Its titled plainly enough, ‘Supernova’ by Roger MacBride Allen & Eric Kotani, Avon books, 1991. One slight drawback tho’ – it does feature the now-past millennnium as a minor element being mostly set in 1999-2000-2001 approx.

  13. Devo Raine

    Loks like an S0 type galaxy – a borderline elliptical /spiral sometimes also called a lenticular galaxy. Not necessarily the sort of Galaxy you’d expect to star with supernovae. (The sort I’d expect, well for type II anyway, would be starburst galaxies eg. M82) Most type II & type Ib would occur from massive young supergiant stars found in young spiral galaxies in the disk mainly. Most old stars occur as populations in the bulges of spirals and in ellipticals so .. well the cosmos confounds expectations again!

    Working on an article about the white dwarf Van Maanen’s Star at present – another neat co-incidence.

    Nearby white dwarfs : Sirius B & Procyon B (F-type star a bit brighter and hotter than our Sun, 11 ly off) which are both orbiting larger main-sequence stars and could perhaps one day become nova or supernovae and then the third nearest and first single white dwarf, Van Maanen’s Star -which won’t become a supernova (SN) – at a distance of 14 light years away. Needless to say if Sirius or Procyon B do turn SN it won’t be for millions of years.

    In answer to ‘ThePolynomial’ : From my recollection &/or gut-feeling I’d say we’d be in serious mass extinction territory if a supernova goes off closer than about 20-30 ly away. One closer than 50 would likely cause serious problems for us & one at about 100 ly would be getting a little close for comfort. One thats 200 or further away and its more a case of lets enjoy the show! 😉

    As for gravitat’l lensing, Glenn Becker, I very much doubt it could duplicate a single star or SN and not the entire galaxy. Not a naive question btw but a good one.

    ioresult -yep. Your understanding and mine are identical on this because that’s right! 😉

    SN do occur after novae outbursts – many of them as the mass builds up. Unless the progenitor white dwarf was very close to the mass limit anyhow …

    White dwarfs may vary slightly with age and mass so it makes sense that
    they may not all be identical and hence not the best standard candles. Haven’t heard any news about recent doubts on their use as such, ‘jackd’ but it wouldn’t surprise me if they were a LOT less accurate as measuring
    sticks than Cepheids etc ..

  14. Devo (again)

    “It’s weird for another reason. Up until this year, it is one of the very few galaxies which have been seen to host more than supernova.”

    Au contraire, its perfectly normal for glaxies to host more than supernova, they host hugenumbers of stars, dark and bright nebulae of allvarieties, dark matter and black holes among other things. Supernovae are what’s quite rare! 😉

    Sorry, I couldn’t resist that … I think you a word out there BA, ‘two’ or ‘one’ perhaps I’m guessing?

    Incidentally – can a neutron star ever become the equivalent of a type Ia supernova? If it gathers too much mass the same way a white dwarf does a pulsar or magnetar just collapse into a black hole or can it start nuclear fusion and blow itself apart as well? & if one did, could we tell the SN apart from white dwarf ones? Anyone know?

  15. scatha

    “Can a neutron star ever become the equivalent of a type Ia supernova ?”

    I believe yes, and I believe you would “see” an extremely energetic gamma ray with similar energy to a supernova- just most of it not as visible light. Very different to a supernova type Ia.

    “Don’t white dwarfs have to pass through a series of novae before finally going through the type I supernova when it collapses into a neutron star?”

    The matter (generally hydrogen) falling bit by bit onto the white dwarf produces nuclear fusions which make it much brighter each time a larger amount of hydrogen falls on it. That’s the series of novae you heard about.
    When the critical mass (1.4 solar masses) is reached, it will collapse but it won’t become a neutron star, but instead, the carbon and oxygen it mostly consists of, will fuse to heavier elements in an extremely fast star-wide total nuclear reaction, thus making it explode again, producing a huge amount of energy very fast- nothing remains except a gas cloud, consisting of a lot of different elements from carbon onwards to iron.


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