Author Topic: Supernova Science  (Read 36760 times)

zookeeperKevin

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Supernova Science
« on: October 12, 2009, 02:13:41 pm »
I'm starting this thread for a discussion about the science behind supernovae. What are they? What kinds of different supernovae are there? What can they teach us? Ask and discuss here!

echo-lily-mai

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Re: Supernova Science
« Reply #1 on: October 13, 2009, 09:48:56 am »
quote from this blog

"Features of supernova spectra are very broad and therefore look like wiggles. Tonight we’re indeed lucky. All the spectra apears to have these wiggles in them. We’ve found a few type Ia supernova so far tonight. Apparently the selection of candidates via the supernova Zoo has been very effective."

Is there a link to the spectra so we could have a look at it? it would be interesting to see.

Also, what is an Ia supernova?

Thanks guys

Echo  :)

Art does not reproduce the visible....  Paul Klee

Richard Scalzo

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Re: Supernova Science
« Reply #2 on: October 13, 2009, 10:57:09 pm »
quote from this blog
Is there a link to the spectra so we could have a look at it? it would be interesting to see.

Also, what is an Ia supernova?

See Dan Kasen's SN Ia page:  http://panisse.lbl.gov/~dnkasen/tutorial/
for a lot of interesting, yet accessible, information about supernovae.  In particular, click on "Supernova Spectra" for nicely labeled spectra of supernovae of various types, including type Ia supernovae (SNe Ia).

Calling something e.g. a "type Ia supernova" is an observational classification based on the chemical elements found in the spectrum (for SNe Ia these are mainly Si, S, Ca, Mg, Fe with no detectable H or He).  We still don't know what exactly they are physically.  We know that the stars which explode in SNe Ia must be in a late stage of their lifetime -- presumably white dwarfs which have little hydrogen or helium left around them, and mostly around 1.4 times the mass of our sun (the "critical mass" for thermonuclear explosion of the star).  We also believe these stars must have binary companions, interactions with which trigger some kind of instability that leads to the explosion.  But the exact details -- what kind of star the binary companion is, how the explosion happens, and so on -- are still being worked out.

There are some fascinating transitional cases -- SNe Ia which might have had progenitor stars more massive than 1.4 solar masses, "SNe IIa" or exploding white dwarfs with strong envelopes of hydrogen, etc.  These are events in which I'm particularly interested.

SNe Ia are, of course, the tools which were used by scientists to discover the "dark energy" causing the universe's expansion to accelerate in recent gigayears, and the best-studied tools currently available to continue to study the nature of the dark energy.  Although scientists are quite confident that something like dark energy must exist, a better understanding of SNe Ia is needed to get any more detailed information about it.  So it's a bit troubling that we still don't know exactly what stars explode in SNe Ia, or how those explosions are triggered and proceed!  It's a very active area of research right now.

-- Richard
« Last Edit: October 13, 2009, 11:04:00 pm by Richard Scalzo »

Lovethetropics

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Re: Supernova Science
« Reply #3 on: October 13, 2009, 11:25:32 pm »
This is Richard Scalzo, a scientist at Yale.  http://pantheon.yale.edu/~rs639/

Part of what he says on his website...seems to me we could help him classifying a few thousand quasars...

Projects I might work on if I had time and/or a student

Individual structure functions for a large (few thousand) sample of SDSS broad-line quasars. The structure function may display characteristic timescales for variability of a system, many of which for quasars relate to the mass of the central black hole (Collier & Peterson 2001). Such work could eventually present a way to measure black hole masses photometrically for a large sample of quasars (e.g. with LSST).

Classification of variable objects in the Palomar/QUEST survey, particularly (with Anne Bauer and Paolo Coppi) optical selection of blazars. Samples of blazars remain small and subject to various selection effects, which must be understood in detail in order to obtain a consistent physical picture of these objects in the framework of a unified model of AGN.

Dr. Scalzo, we are not physicists but we're dedicated, thorough and many. ;D

 *and find lots of asteroids  ;D

Richard Scalzo

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Re: Supernova Science
« Reply #4 on: October 14, 2009, 12:16:29 am »
Thanks Aida for the warm welcome!  Where are my manners, I should have introduced myself properly...  :)  I've been talking a lot lately with Kevin and Mark about the new SN Zoo project and am excited about becoming more involved, so I hope to be seen around here more often soon.

Here at Yale, Kevin has tirelessly advocated the whole Zoo approach to transient/variable science, including AGN from the Palomar and/or La Silla surveys described briefly on my website.  Right now I'm concentrating mainly on SNe Ia, and don't yet have a good feeling for how to incorporate the AGN science into the Zoo framework, but it's certainly something I'd be interested in doing for the future.  Should I ever get traction on that project you all can say you saw it here first.  ;)

In the meantime, please do post your questions about SNe Ia or other kinds of SNe, and I'll do my best to help answer them as I have time available.  It's great to be here!

-- Richard


Lovethetropics

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Re: Supernova Science
« Reply #5 on: October 14, 2009, 12:23:41 am »
Welcome to the Zoo Richard and we are delighted to have you here.   ;D

 *and find lots of asteroids  ;D

Alice

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Re: Supernova Science
« Reply #6 on: October 14, 2009, 12:40:26 am »
Welcome to the zoo Richard! A supvernova-answerer is just what we need! ;D

Here at Yale, Kevin has tirelessly advocated the whole Zoo approach to transient/variable science . . .
I'll bet he has :D

Zeus2007

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Re: Supernova Science
« Reply #7 on: October 14, 2009, 04:26:20 am »
Were the Chinese like the first astronomers to ever discover a supernova? And why is it called supernova? Is nova the Latin equivalent of I don't know, start, light, new? No, it can't be new.
"The journey of a thousand miles must begin with a single step"
Lao Tzu, Ancient Chinese Philosopher.

Lovethetropics

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Re: Supernova Science
« Reply #8 on: October 14, 2009, 04:48:06 am »
Were the Chinese like the first astronomers to ever discover a supernova? And why is it called supernova? Is nova the Latin equivalent of I don't know, start, light, new? No, it can't be new.

It means "new" Zeus...remember in Spanish the "novatos" (newbies in college), that comes from nova too.
From nova also comes "nuevo" in Spanish which is "new" in English.
« Last Edit: October 14, 2009, 04:56:38 am by Lovethetropics »

 *and find lots of asteroids  ;D

Zeus2007

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Re: Supernova Science
« Reply #9 on: October 14, 2009, 05:14:59 am »
But in that case it'll technically mean "super new"...it has no reference no star.
"The journey of a thousand miles must begin with a single step"
Lao Tzu, Ancient Chinese Philosopher.

Richard Scalzo

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Re: Supernova Science
« Reply #10 on: October 14, 2009, 06:19:43 am »
Were the Chinese like the first astronomers to ever discover a supernova? And why is it called supernova? Is nova the Latin equivalent of I don't know, start, light, new? No, it can't be new.

Hi Zeus (et al.),

Yes, the word "supernova" has an interesting history.  The term "nova" was already generically in use for "new stars" in the sky, such as SN 1054 which was seen by the Chinese (the remnant is called the Crab Nebula) and by the Anasazi tribe of Native Americans (see http://www.astronomy.pomona.edu/archeo/outside/chaco/nebula.html).  The term "super nova" was coined by Caltech astronomer Fritz Zwicky, when it became clear that the explosions were probably happening in other galaxies and therefore had to be much brighter than was previously thought.  The taxonomy of types based on spectra I mentioned before came later after more SNe had been found.

Here's a link to Zwicky's first use of the term:  http://adsabs.harvard.edu/abs/1934PNAS...20..254B

There's also this paper of Zwicky's:  http://adsabs.harvard.edu/abs/1938ApJ....88..529Z
which is the first attempt I know about to measure the rate of supernovae.  Zwicky looked at a large sample of known galaxies, much as the Lick Observatory Supernova Search (LOSS) does today (robotically).  The PTF search operating at Palomar today, which supplies supernova candidates to the SN Zoo citizen scientists, doesn't target known galaxies, but looks anywhere on the sky where a supernova might occur.  This is important because different kinds of stars might explode to give different types or subtypes of SNe, and for answering certain science questions about SNe in general (e.g. the environments in which they occur), you want to make sure your sample of SNe doesn't cherry-pick only the types that go off in galaxies like the ones you looked at.

Try reading Zwicky's papers though -- they're remarkably well-written and give a neat window back on a time when the universe seemed smaller than it seems today.  You should be able to click on "Full Refereed Article" in ADS to get scanned copies for free.

-- Richard
« Last Edit: October 14, 2009, 02:30:13 pm by Richard Scalzo »

Blackprojects

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Re: Supernova Science
« Reply #11 on: October 14, 2009, 12:57:56 pm »
Hi Aida

The amount of Quasars you have been finding in the last few Days in the RED Lentil Hunt may well fill the Quasar Requirments for some Researchers for a long time!


I was reading this a little while ago!

http://homepage.mac.com/mrlaurie/btcfolder/astro2002webpages/Period%202/suernova.html

« Last Edit: October 14, 2009, 01:00:15 pm by Blackprojects »

Lovethetropics

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Re: Supernova Science
« Reply #12 on: October 14, 2009, 02:30:58 pm »
Very good information on that link dear Mark, thank you. ;D ;D ;D

 *and find lots of asteroids  ;D

XYZoo

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Re: Supernova Science
« Reply #13 on: October 14, 2009, 02:53:04 pm »
Hello,
I have a silly question about SN1987A (is this allowed in this topic?). When I watch this video:
http://www.spacetelescope.org/videos/html/mov/320px/hst15_sn1987a_movie.html
I wonder why the ring of matter around the SN gets those spots shining in "chunks" and does not shine as a uniform ring. Is the Supernova energy released in definied "beams" and not as a spherical shell? Or is this effect more related with the shape/composition of the ring than with the supernova event itself?
Thanks a lot... I have had this question for a while and I think this is the right place for me to ask it! :-)

Zeus2007

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Re: Supernova Science
« Reply #14 on: October 14, 2009, 11:09:34 pm »
Were the Chinese like the first astronomers to ever discover a supernova? And why is it called supernova? Is nova the Latin equivalent of I don't know, start, light, new? No, it can't be new.

Hi Zeus (et al.),

Yes, the word "supernova" has an interesting history.  The term "nova" was already generically in use for "new stars" in the sky, such as SN 1054 which was seen by the Chinese (the remnant is called the Crab Nebula) and by the Anasazi tribe of Native Americans (see http://www.astronomy.pomona.edu/archeo/outside/chaco/nebula.html).  The term "super nova" was coined by Caltech astronomer Fritz Zwicky, when it became clear that the explosions were probably happening in other galaxies and therefore had to be much brighter than was previously thought.  The taxonomy of types based on spectra I mentioned before came later after more SNe had been found.

Here's a link to Zwicky's first use of the term:  http://adsabs.harvard.edu/abs/1934PNAS...20..254B

There's also this paper of Zwicky's:  http://adsabs.harvard.edu/abs/1938ApJ....88..529Z
which is the first attempt I know about to measure the rate of supernovae.  Zwicky looked at a large sample of known galaxies, much as the Lick Observatory Supernova Search (LOSS) does today (robotically).  The PTF search operating at Palomar today, which supplies supernova candidates to the SN Zoo citizen scientists, doesn't target known galaxies, but looks anywhere on the sky where a supernova might occur.  This is important because different kinds of stars might explode to give different types or subtypes of SNe, and for answering certain science questions about SNe in general (e.g. the environments in which they occur), you want to make sure your sample of SNe doesn't cherry-pick only the types that go off in galaxies like the ones you looked at.

Try reading Zwicky's papers though -- they're remarkably well-written and give a neat window back on a time when the universe seemed smaller than it seems today.  You should be able to click on "Full Refereed Article" in ADS to get scanned copies for free.

-- Richard

Thank you very kindly, Richard, this is all wonderful info.  I'll come back and visit the links you left.  Supernova is indeed an interesting subject.
"The journey of a thousand miles must begin with a single step"
Lao Tzu, Ancient Chinese Philosopher.