Topic: Supernovae

[Astronuc]

Supernovae are interesting and spectacular phenomena.

Here are some references:

Wikipedia - Supernova

Supernova - What are the progenitors of the supernova type 1A explosion?
Jakob van Bethlehem

See also Supernovae thread in "Ask the Astronomer".

Cosmic Rays and Supernova Source  in this forum.

Related thread 18 Supernovas Discovered by The Subaru Telescope

SNEWS: SuperNova Early Warning System
http://snews.bnl.gov/

[Astronuc]

(AOL/AP/NASA) - This titanic explosion took place in the Large Magellanic Cloud, a nearby neighbor galaxy some 160,000 light-years away.

STScI-PRC2005-30  -  NASA Space Observatories Glimpse Faint Afterglow of Nearby Stellar Explosion

Intricate wisps of glowing gas float amid a myriad of stars in this image created by combining data from NASA's Hubble Space Telescope and Chandra X-ray Observatory. The gas is a supernova remnant, cataloged as N132D, ejected from the explosion of a massive star that occurred some 3,000 years ago. This titanic explosion took place in the Large Magellanic Cloud, a nearby neighbor galaxy of our own Milky Way.

The complex structure of N132D is due to the expanding supersonic shock wave from the explosion impacting the interstellar gas of the LMC. Deep within the remnant, the Hubble visible light image reveals a crescent-shaped cloud of pink emission from hydrogen gas, and soft purple wisps that correspond to regions of glowing oxygen emission. A dense background of colorful stars in the LMC is also shown in the Hubble image.

The large horseshoe-shaped gas cloud on the left-hand side of the remnant is glowing in X-rays, as imaged by Chandra. In order to emit X-rays, the gas must have been heated to a temperature of about 18 million °F (10 million °C). A supernova-generated shock wave traveling at a velocity of more than four million miles per hour (2,000 kilometers per second) is continuing to propagate through the low-density medium today. The shock front where the material from the supernova collides with ambient interstellar material in the LMC is responsible for these high temperatures.

It is estimated that the star that exploded as a supernova to produce the N132D remnant was 10 to 15 times more massive than our own Sun. As fast-moving ejecta from the explosion slam into the cool, dense interstellar clouds in the LMC, complex shock fronts are created.

A supernova remnant like N132D provides a rare opportunity for direct observation of stellar material, because it is made of gas that was recently hidden deep inside a star. Thus it provides information on stellar evolution and the creation of chemical elements such as oxygen through nuclear reactions in their cores. Such observations also help reveal how the interstellar medium (the gas that occupies the vast spaces between the stars) is enriched with chemical elements because of supernova explosions. Later on, these elements are incorporated into new generations of stars and their accompanying planets.

Visible only from Earth's southern hemisphere, the LMC is an irregular galaxy lying about 160,000 light-years from the Milky Way. The supernova remnant appears to be about 3,000 years old, but since its light took 160,000 years to reach us, the explosion actually occurred some 163,000 years ago.

This composite image of N132D was created by the Hubble Heritage team from visible-light data taken in January 2004 with Hubble's Advanced Camera for Surveys, and X-ray images obtained in July 2000 by Chandra's Advanced CCD Imaging Spectrometer. This marks the first Hubble Heritage image that combines pictures taken by two separate space observatories. The Hubble data include color filters that sample starlight in the blue, green, and red portions of the spectrum, as well as the pink emission from glowing hydrogen gas. The Chandra data are assigned blue in the color composite, in accordance with the much higher energy of the X-rays, emitted from extremely hot gas. This gas does not emit a significant amount of optical light, and was only detected by Chandra.

[Astronuc]

A rather spectacular site - Vela supernova remnant - images from Anglo-Australian Observatory

A supernova event marks the catastrophic end-point in the life of a massive star. The self-destruction of the star releases a huge amount of energy as radiation of all kinds, but a substantial fraction of the force of the explosion blasts the outer part of the supernova into an expanding shell of matter that travels through the almost empty space between the stars. As the rapidly moving blast wave encounters the relatively stationary interstellar medium it creates a very narrow, luminous shock front that appears as a faint nebula. Because the shock front is very convoluted the nebulosity appears to be highly structured and the various colours define different energy levels within the interaction. Though the star responsible for the Vela supernova remnant exploded 12,000 years ago, it is still affecting its environment.

[Astronuc]

http://www.rochesterastronomy.org/SNIMAGES/

http://heasarc.gsfc.nasa.gov/docs/snr.html

Hidden Star Explains Supernova Oddity
by Tariq Malik
http://www.space.com/scienceastronomy/060504_supernova_companion.html
(Space.com has adds and popups  >:(  :P )

A star once hidden by a stellar death shroud is the source of odd behavior of its companion supernova, a new study has found.

The find has laid to rest lingering questions over how the supernova, known as SN2001ig, seemed to change its cosmic stripes within weeks while astronomers looked on.

"It was quite satisfying to be able to hold up a picture and see that there was a companion star right where we predicted," said Stuart Ryder, an astronomer with the Anglo-Australian Observatory in Sydney, Australia, in a telephone interview.

Ryder and his team suspected a companion star was to blame for SN2001ig's shift from a hydrogen-rich supernova, known as a Type II, to a Type I variety devoid of detectable hydrogen, based on previous radio observations. But it was only after debris from the initial stellar explosion cleared that the star's existence, and its likely role in stripping hydrogen from the supernova, were confirmed by optical observations.

 

Bright Supernovae (2001) -

http://ftp.ru.postgresql.org/mirrors/isn/sn2001/index.html

http://ftp.ru.postgresql.org/mirrors/isn/sn2001/upd01.html

Edit (05-11-06): Companion Explains "Chameleon" Supernova
http://www.gemini.edu/index.php?option=content&task=view&id=184

Australian astronomers have found a predicted "companion" star left behind when its partner exploded as a very unusual supernova. The presence of the companion explains why the supernova, which started off looking like one kind of exploding star, seemed to change its identity after a few weeks.

Renowned Australian supernova hunter Bob Evans first spotted supernova 2001ig in December 2001. It lies in the outskirts of a spiral galaxy NGC 7424, which is about 37 million light-years away in the southern constellation of Grus (the Crane).

 

[Retrospector]

I'd like to see a little more explanation about how the spectral type changes, I know space.com isn't the best place to find that kind of detail. ;) From what I can discern, I assume that it's the usual model, meaning that the companion star was dumping hydrogen on the supernova pregenitor which caused the mass of the star to rise and the carbon core to begin thermonuclear fusion. So if I'm reading this right, hydrogen being blown away from the top layers would have been observed at the very beginning of the event but not later.

I guess it's also implied that this would be a common pattern for Type I (I think actually Type Ia) supernovae but by the nature of such events they are generally not seen at the very beginning of their detonations.

I've seen it theorized that this class of supernovae usually blow their companion stars away when they ignite, which is why its been hard to find direct evidence for the companion star model.

[Astronuc]

Some good comments and observations.

Here is an article from ESA on supernovae, particularly one SN 1993J, where there is sufficient observational evidence to elucidate the behavior of a companion.
http://hubble.esa.int/science-e/www/object/index.cfm?fobjectid=34455

The second brightest supernova discovered in modern times, SN 1993J, was found in the beautiful spiral galaxy M81 on 28 March 1993. From archival images of this galaxy taken before the explosion, a red supergiant was identified as the mother star in 1993 - only the second time astronomers have actually seen the progenitor of a supernova explosion (the first was SN 1987A, the supernova that exploded in 1987 in our neighbouring galaxy, the Large Magellanic Cloud). Initially rather ordinary, SN 1993J began to puzzle astronomers as its ejecta seemed too rich in the chemical element helium and instead of fading normally it showed a bizarre sharp increase in brightness. The astronomers realised that a normal red supergiant alone could not have given rise to such a weird supernova. It was suggested that the red supergiant orbited a companion star that had shredded its outer layers just before the explosion.

 
I need to dig further into the spectral type of the progenitor (a red supergiant) and then look into other similar binaries, and then see what has been observed in the last two years.

Meanwhile - "A method to identify the companion stars of type Ia supernovae in young supernova remnants," Jin Ozaki, Toshikazu Shigeyama
http://arxiv.org/PS_cache/astro-ph/pdf/0602/0602574.pdf

Some more background on supernovae - http://www.pha.jhu.edu/~qzhang/seminar1bfigs/seminar1bfigs.html

[Retrospector]

I looked at a book (popular science category) on cosmic catastrophes this weekend. I'll post the reference in a bit. There are many sites that discuss the various supernova phenomena. Here's a Wikepedia link (more technical detail is available elsewhere.)

http://en.wikipedia.org/wiki/Supernova

Drawing from my memory of what I read here's a simple breakdown of the supernovae types.

Type Ia-detonation of a carbon core white dwarf star-mechanism not confirmed but presumed to occur from some kind of mass addition-perhaps from a companion star or from a collision with another white dwarf. Spectral characteristics-no hydrogen, no helium, strong silicon line at maximum, large amount of iron at later stages.

Type Ib-detonation of a massive star due to core collapse. Spectral characteristics-no hydrogen, but helium, absence of strong silicon line, iron present. Presumably this is due to a large star collapsing which had its outer envelope of hydrogen stripped before the collapse.

Type Ic-detonation of a massive star due to core collapse. Spectral characteristics-no hydrogen, no helium, absence of strong silicon line, iron present. Like Type Ib, the hydrogen envelope is presumed to have been stripped prior to the collapse but here the helium shell is gone too.

Type II-detonation of a massive star due to core collapse. Spectral characteristics-hydrogen, helium present, as are a whole range of light to very heavy elements. The progenitor star is presumed to have retained all the shells of its history of fusing heavier and heavier elements until it comes to a stop at iron.

The Type Ia's are the really distinctive ones-what they call a deflagration ignition in a relatively small stellar remnant.

Articles like the space.com one really frustrate me. I'd like to know more about what the supernova type is theorized to have been.

[Astronuc]

I agree about space.com articles - they don't have much in the way of substantive discussion, partricularly the physics.  Spacedaily articles are better, but I usually have to contact the person doing the research, or track down relevant articles which have been published.

I am also very curious about supernovaes and the subsequent remnants - nebulae and neutron stars - and the companion stars.

I'd like to know more about the binary star systems, and the type of stars which go supernovae.

It would be interesting to be able to predict which stars might go SN.

There is also a thread on Magnetars and Neutron Stars.  I have to wonder if the initial nova or supernova was observed.

Unfortunately, there aren't any good records of stellar spectra going back hundreds or thousands of years, and I am not sure if we have sufficient data on magnitudes of stars that went SN.

[Retrospector]

Among presumed core collapse supernovae, there is the well known example of the Crab Nebula which contains a pulsar-that star detonated almost a thousand years ago.

Then there's the famous example of Supernova 1987A which was observed in the Large Magellenic Cloud nineteen years ago. It appears to have been a core collapse type. It's a great story how the burst of neutrinos was detected by the Kamiokande detectors before anyone knew the star had exploded.

http://hep.bu.edu/~superk/gc.html

According to the core collapse model, a neutron star should have been left after the explosion. The mystery that continues to this day is why a neutron star-pulsar still hasn't been observed at the center of the explosion.

[Astronuc]

Retrospector, if you have have links to other sites or papers, particularly more technical detail, please post them.

Meanwhile, I found a list of supernovae -
http://cfa-www.harvard.edu/cfa/ps/lists/Supernovae.html

List of Supernovae - gives details on all supernovae reported since 1885, as well as four earlier galactic supernovae. All coordinates given in the table below are J2000.0 positions. Date refers to the date of discovery, Mag. to the magnitude at discovery and Offset to the offset from the nucleus of the host galaxy as reported at time of discovery. Disc. Ref. is the reference to the discovery report, Posn. Ref. is the source of the accurate position and Type is the supernova's type (as reported at or near the time of discovery). Note that the preferred hierarchy for host-galaxy catalogue designations is M/NGC/IC, UGC, MCG; all other catalogues are considered "Anon" below.

 

Well this answers some questions I had as to where, when and what kind of SN.  ;D

and this -

While many supernovae have been seen in nearby galaxies, they are relatively rare events in our own galaxy. The last to be seen was Kepler's star in 1604. This remnant has been studied by many X-ray astronomy satellites, including ROSAT. There are, however, many remnants of Supernovae explosions in our galaxy, that are seen as X-ray shell like structures caused by the shock wave propagating out into the interstellar medium. Another famous remnant is the Crab Nebula which exploded in 1054. In this case a pulsar is seen which rotates 30 times a second and emits a rotating beam of X-rays (like a lighthouse). Another dramatic supernova remnant is the Cygnus Loop.

  from http://heasarc.gsfc.nasa.gov/docs/snr.html

Now I have some questions to formulate and some information to sift through.

I would like to understand more about the precursor stars.  I wonder what fractions of supernovae involve precursors in a binary system.

And more resources on the web regarding supernovae -
http://rsd-www.nrl.navy.mil/7212/montes/sne.html

 :koala

[Astronuc]

Brief overview of supernovae on hyperphysics - http://hyperphysics.phy-astr.gsu.edu/HBASE/astro/snovcn.html

Formation of heavy elements
http://hyperphysics.phy-astr.gsu.edu/HBASE/astro/nucsyn.html#c1

Supernova 1987A
http://hyperphysics.phy-astr.gsu.edu/HBASE/astro/sn87a.html#c1

The discovery of Supernova 1987A was a great opportunity for detailed observation of the dynamics of a supernova. This supernova was unusual in that it did not rise abruptly to its maximum brightness, but paused briefly before increasing its luminosity by another factor of ten. It increased for about 85 days and then began a gradual decline which was more characteristic of other observed supernovae.

Another unique feature about this supernova is that the star which exploded had been observed and named Sk-69202. It was a blue supergiant presumed to have a mass of about 20 solar masses.

 

and this reference of Harvard's Chandra site -
http://chandra.harvard.edu/xray_sources/supernovas.html

Interestingly this page - http://chandra.harvard.edu/resources/illustrations/superNeutron.html -shows a red giant, which explodes and forms a neutron star.

[Astronuc]

Here's a list of supernovae in our Milky Way Galaxy
http://www.seds.org/messier/more/mw_sn.html

Information on the historical supernovae - Michael Richmond (March 19, 1997)
http://stupendous.rit.edu/richmond/answers/historical.html

Types - http://a188-l009.rit.edu/richmond/answers/sntypes.txt

HISTORICAL RECORDS OF SUPERNOVAE
http://astrosun2.astro.cornell.edu/academics/courses//astro201/sn_history.htm

[Retrospector]

Astronuc, I've seen some good links and a lot of pictures in recent years. I need to trace them and organize some posts.

It's a bit of a mystery why no naked eye supernova has been observed in our home galaxy for more than four centuries. The only naked eye supernova that has occurred since that time occurred in 1987, in the Large Magellenic Cloud (close to the Milky Way, but no cigar.) Some astronomers speculate that since there is so much dust between us and the inner regions of the galaxy, that is what has blocked the naked eye views of many supernova events in the Milky Way (although there are other ways now to detect the explosions themselves.)

There is relatively nearby supernova remnant, it is a radio source known as Cassiopeia A. It is in our galaxy about 11,000 ly away, relatively close, and the mystery is why it wasn't observed by anyone as a naked eye supernova in the late 17th Century. Here's a short link:

http://www.seds.org/~spider/spider/Vars/casA.html

The remnant really looks like an explosion! And there is what may be a neutron star at the centre.




This is thought to have been a supernova resulting from a core collapse, such as the one which presumably created the Crab Nebula.

The supernovae of most interest in recent years have been the Type Ia's, which are thought to result from the explosion of white dwarf stars in binary systems. They appear to serve as "standard candles", objects whose absolute brightness can be judged from their luminosity-time characteristics and therefore allow distances to their parent galaxies-even over billions of light years-to be accurately judged.

What historical supernova events in our galaxy were Type Ia is an extremely interesting topic. At present I believe the most likely candidates are the 1572 event seen in Cassiopeia-called "Tycho's Star" because of the observations of Danish astronomer Tycho Brahe, and the great supernova even of 1006-we just passed the 1,000th anniversary of its sighting. That was likely the brightest supernova observed in recorded times, and the distance to its remnant has been measured to be only 7,100 ly.

http://www.noao.edu/outreach/press/pr03/pr0304.html

Edit: I should add that the Cassiopeia A picture is from the seds.org link posted above it, and that it is a Chandra X-Ray Observatory X-Ray image.

[Astronuc]

Interesting comment on seds.org

Similar to other galaxies (including the Messier galaxies), there occur supernovae in our Milky Way at irregular intervals of time. 

If they are not too heavily obscurred by interstellar matter, they can be seen as very spectacular events in the sky. Unfortunately, though, none of them has been well visible since the invention of the telescope, although modern estimates predict that every few decades one supernova should occur in a galaxy like the Milky Way!

 

But we haven't seen any.

[Astronuc]

Historical Supernovae and their Remnants by F. Richard Stephenson and David A. Green.

This book, written by two leading astrophysicists, reviews the historical observations of supernova explosions in our Galaxy over the past two thousand years and discusses modern observations of the remnants of these explosions at radio and other wavelengths.

 This seems like an interseting book, although it's a bit pricey at $169.50.