APOD: Supernova 1994D and the Unexpected... (2015 May 31)

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APOD: Supernova 1994D and the Unexpected... (2015 May 31)

Postby APOD Robot » Sun May 31, 2015 4:09 am

Image Supernova 1994D and the Unexpected Universe

Explanation: Long ago, far away, a star exploded. Supernova 1994D, visible as the bright spot on the lower left, occurred in the outskirts of disk galaxy NGC 4526. Supernova 1994D was not of interest for how different it was, but rather for how similar it was to other supernovae. In fact, the light emitted during the weeks after its explosion caused it to be given the familiar designation of a Type Ia supernova. If all Type 1a supernovae have the same intrinsic brightness, then the dimmer a supernova appears, the farther away it must be. By calibrating a precise brightness-distance relation, astronomers are able to estimate not only the expansion rate of the universe (parameterized by the Hubble Constant), but also the geometry of the universe we live in (parameterized by Omega and Lambda). The large number and great distances to supernovae measured over the past few years, when combined with other observations, are interpreted as indicating that we live in a previously unexpected universe.

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Re: APOD: Supernova 1994D and the Unexpected... (2015 May 31

Postby Boomer12k » Sun May 31, 2015 4:45 am

And as recently reported... Not all Type1a Supernova are of actual equal brightness... Thus putting into question the rush of the expansion of the Universe, as well as the concept of how much dark energy there may be....
And throwing off the concept of a standard candle...

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Re: APOD: Supernova 1994D and the Unexpected... (2015 May 31

Postby Ann » Sun May 31, 2015 4:59 am

It is interesting that this galaxy has been classified as a lenticular, in view of the fact that it contains a significant dust disk. This image also shows that the near side of the disk of NGC 4526 is partly bluish, which means that it must contain a number of relatively young stars. It is interesting to compare the near side of the disk of NGC 4526 with the near side of the disk of M104, which isn't bluish at all. I'd say that more of the disk is young in NGC 4526 than in M104.

Here is another picture of NGC 2546, where you can see both the bluish supernova and a Milky Way foreground star apparently located to the left of it. Again you can see the bluish tint of young stars in the dust disk.

I believe that supernovas, even Type Ia supernovas, are more likely to appear in galaxies with a young population than in galaxies that all but lack young stars. According to this catalog, there have been no recorded supernovas at all in "old" M104. Fascinatingly though, M84, an elliptical galaxy, has hosted three supernovas. M84 also has a rotating dust disk near its center, although in this picture I can see no signs of stars in the dust, let alone young blue stars.

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Re: APOD: Supernova 1994D and the Unexpected... (2015 May 31

Postby RocketRon » Sun May 31, 2015 5:31 am

On a more mundane matter, and also unexpected, is that the displayed date on this APOD has regressed.
27th May was 4 days ago, by Earths solar calendar.
No doubt it will be correct someplace in the universe, but folks might bear it in mind anyway... :?:

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Re: APOD: Supernova 1994D and the Unexpected... (2015 May 31

Postby Boomer12k » Sun May 31, 2015 5:33 am

What a DUSTY GALAXY????? Is that a NEW CLASS?????

It also shows...that far beyond the disk.... there are stars...


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Re: APOD: Supernova 1994D and the Unexpected... (2015 May 31

Postby Kaius » Sun May 31, 2015 6:15 am

Ann wrote:It is interesting to compare the near side of the disk of NGC 4526 with the near side of the disk of M104, which isn't bluish at all. I'd say that more of the disk is young in NGC 4526 than in M104.
Ann


I can understand that blue stars are young since they are massive and approach the end of their lives quickly. But is it possible that the stars in the disk of M104 are also young, but just with a smaller mass? Not sure if this is a stupid question, but I'm new to astronomy.

Ann wrote:I believe that supernovas, even Type Ia supernovas, are more likely to appear in galaxies with a young population than in galaxies that all but lack young stars. Ann


Is there a physical explanation for this? Are all types of supernovae more likely to appear in galaxies with a younger star population?

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Re: APOD: Supernova 1994D and the Unexpected... (2015 May 31

Postby Ann » Sun May 31, 2015 6:33 am

Kaius wrote:
Ann wrote:It is interesting to compare the near side of the disk of NGC 4526 with the near side of the disk of M104, which isn't bluish at all. I'd say that more of the disk is young in NGC 4526 than in M104.
Ann


I can understand that blue stars are young since they are massive and approach the end of their lives quickly. But is it possible that the stars in the disk of M104 are also young, but just with a smaller mass? Not sure if this is a stupid question, but I'm new to astronomy.

Ann wrote:I believe that supernovas, even Type Ia supernovas, are more likely to appear in galaxies with a young population than in galaxies that all but lack young stars. Ann


Is there a physical explanation for this? Are all types of supernovae more likely to appear in galaxies with a younger star population?


Good questions, Kaius.

Yes, it is definitely possible to have low-mass star formation. So like you said, there might be low-mass young stars in the disk of M104. Such stars, however, will not go core-collapse, Type II supernova. Can they go Type Ia supernova? I think it is harder for them to do it, and it takes a longer time. It is in fact possible that it takes such a long time to do it that the universe is not old enough for stars like the Sun to have gone pop yet!

Consider. There are main sequence stars rather similar to the Sun in globular clusters, which are typically about 12 billion years old. The universe is about 14 billion years old, and it didn't start producing stars right away. To have a supernova Type Ia you first need a main sequence star, and then that star must evolve until it is ready to go supernova Ia. Astronomers are fairly certain that it takes either a white dwarf and a red giant to produce a Type Ia supernova, or else two white dwarfs. Main sequence stars don't produce supernovas. In order to get a white dwarf, a main sequence star first has to evolve into a red giant and then into a white dwarf. For low-mass stars, that takes a long time. For higher mass stars it happens a lot quicker. There are no stars similar to A0-type star Vega, about tree times more massive than the Sun, in globular clusters. Yes, there just might be blue stragglers, which are likely products of merging low-mass stars. But even the blue stragglers are unlikely to be as blue and bright as Vega. And in any case, there are no blue stragglers similar to B7-type 3.4 solar mass star Regulus in globular clusters. Regulus and Vega are destined to become white dwarfs, and that will happen to them while the Sun, which is much older than either of them, is still a main sequence star.

Interestingly, while Vega is a single star, Regulus does indeed seem to have a companion:

Jim Kaler wrote:
Much more intriguing is a tight fourth companion detected only spectroscopically that orbits Regulus proper with a period of a mere 40.11 days. Analysis suggests that it is white dwarf with an anomolously low mass of just 0.3 solar, far below the minimum of 0.55 allowed by current stellar evolution. Kepler's laws then give a separation of about 0.35 Astronomical Units. Astronomers speculate that when the white dwarf was a luminous giant (far larger and brighter than Regulus is now) that it transferred much of its mass (through tidal interaction) to the star that is now Regulus, and in doing so, sped it up to its current fast rotation rate (which fits with the white dwarf scenario.


It is unclear (at least to me) if a 0.3 solar mass white dwarf can go supernova. But if it can, it is possible that the Regulus star system may produce a supernova in the future, when Regulus evolves into a red giant and starts spilling material on its white dwarf companion.

Ann
Last edited by Ann on Sun May 31, 2015 7:15 am, edited 3 times in total.
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Re: APOD: Supernova 1994D and the Unexpected... (2015 May 31

Postby geckzilla » Sun May 31, 2015 6:34 am

RocketRon wrote:On a more mundane matter, and also unexpected, is that the displayed date on this APOD has regressed.
27th May was 4 days ago, by Earths solar calendar.
No doubt it will be correct someplace in the universe, but folks might bear it in mind anyway... :?:

I noticed this earlier and thought I was going nuts. Sent Bob an email. He'll probably fix it when he can.
Just call me "geck" because "zilla" is like a last name.

mundane matters

Re: APOD: Supernova 1994D and the Unexpected... (2015 May 31

Postby mundane matters » Sun May 31, 2015 6:49 am

quick oops dept.: where's the full resolution file? when you click on the picture http://apod.nasa.gov/apod/image/1505/sn94d_hiZ_2068.jpg you get a 404 error. just fyi. :-)

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Re: APOD: Supernova 1994D and the Unexpected... (2015 May 31

Postby geckzilla » Sun May 31, 2015 8:14 am

mundane matters wrote:quick oops dept.: where's the full resolution file? when you click on the picture http://apod.nasa.gov/apod/image/1505/sn94d_hiZ_2068.jpg you get a 404 error. just fyi. :-)

The 0 and 6 in the URL were transposed. You can find the full res file here: http://apod.nasa.gov/apod/image/1505/sn94d_hiZ_2608.jpg
(Bystander notified the editors about this.)
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hoohaw

Re: APOD: Supernova 1994D and the Unexpected... (2015 May 31

Postby hoohaw » Sun May 31, 2015 9:12 am

geckzilla wrote:
RocketRon wrote:On a more mundane matter, and also unexpected, is that the displayed date on this APOD has regressed.
27th May was 4 days ago, by Earths solar calendar.
No doubt it will be correct someplace in the universe, but folks might bear it in mind anyway... :?:

I noticed this earlier and thought I was going nuts. Sent Bob an email. He'll probably fix it when he can.


Are we quite sure it is not a relativistic effect, perhaps induced by the Supernova? Hmmmmm!

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Re: APOD: Supernova 1994D and the Unexpected... (2015 May 31

Postby Craine » Sun May 31, 2015 1:10 pm

And then there was this:
http://www.sci-news.com/astronomy/science-type-ia-supernovae-02688.html

It may well be that Type Ia supernovae do not all have the same brightness. In which case the expansion rate of the universe may be far less then previously thought.

Science! She is a fickle mistress.

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Re: APOD: Supernova 1994D and the Unexpected... (2015 May 31

Postby rj rl » Sun May 31, 2015 3:09 pm

So, is the universe considered flat or curved based on the latest observations? I always thought it has negative curvature, although where I got that from I can't quite remember.

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Re: APOD: Supernova 1994D and the Unexpected... (2015 May 31

Postby Ann » Sun May 31, 2015 3:11 pm

rj rl wrote:So, is the universe considered flat or curved based on the latest observations? I always thought it has negative curvature, although where I got that from I can't quite remember.


Wikipedia wrote:
Although the shape of the Universe is still a matter of debate in physical cosmology, the recent Wilkinson Microwave Anisotropy Probe (WMAP) measurements allow the statement that "We now know that the universe is flat with only a 0.4% margin of error", according to NASA scientists.


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Re: APOD: Supernova 1994D and the Unexpected... (2015 May 31

Postby Guest » Sun May 31, 2015 7:47 pm

Boomer12k wrote:What a DUSTY GALAXY????? Is that a NEW CLASS?????

It also shows...that far beyond the disk.... there are stars...


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Agreed. It looks like a galaxy that has all the gravitational dynamics except those that collapse gas and dust clouds into stars in a wholesale orgy of fusion, like other galaxies. Maybe it started out with more than its share of gas and dust ? If something like this appeared on the main viewer of a spacecraft in a space movie, it would be the 'evil' galaxy.

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Re: APOD: Supernova 1994D and the Unexpected... (2015 May 31

Postby Ann » Sun May 31, 2015 11:36 pm

Guest wrote:
Boomer12k wrote:What a DUSTY GALAXY????? Is that a NEW CLASS?????

It also shows...that far beyond the disk.... there are stars...


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Agreed. It looks like a galaxy that has all the gravitational dynamics except those that collapse gas and dust clouds into stars in a wholesale orgy of fusion, like other galaxies. Maybe it started out with more than its share of gas and dust ? If something like this appeared on the main viewer of a spacecraft in a space movie, it would be the 'evil' galaxy.


ESA/Hubble & NASA, Acknowledgement: Judy Schmidt


As this image shows, NGC 4526 isn't very dusty at all. It just has a small dust disk near its center.

The bright star seen to the right of the dust disk in this image is a foreground Milky Way star.

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Re: APOD: Supernova 1994D and the Unexpected... (2015 May 31

Postby DavidLeodis » Mon Jun 01, 2015 9:46 pm

In information that I've found about the High-Z Supernova Search project it states "The High-Z Supernova Search Team was an international cosmology collaboration which used Type Ia supernovae to chart the expansion of the universe. The team was formed in 1994...The original project was awarded four nights of telescope time on the CTIO Victor M. Blanco Telescope on the nights of February 25, 1995, and March 6, 24, and 29, 1995". As supernova 1994D was therefore discovered before the project began I am confused about when the image was taken. Did the supernova still show its presence being seen as a star-like object long after the event? Thanks for any help.

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Re: APOD: Supernova 1994D and the Unexpected... (2015 May 31

Postby Ann » Mon Jun 01, 2015 11:46 pm

DavidLeodis wrote:In information that I've found about the High-Z Supernova Search project it states "The High-Z Supernova Search Team was an international cosmology collaboration which used Type Ia supernovae to chart the expansion of the universe. The team was formed in 1994...The original project was awarded four nights of telescope time on the CTIO Victor M. Blanco Telescope on the nights of February 25, 1995, and March 6, 24, and 29, 1995". As supernova 1994D was therefore discovered before the project began I am confused about when the image was taken. Did the supernova still show its presence being seen as a star-like object long after the event? Thanks for any help.


Check out this page. Here it says that the supernova was discovered on March 7, 1994. It doesn't say when the picture itself was taken, but we can be sure that it was taken not too long afterwards. Although colors are hard to judge in pictures like this, I believe it is possible to say that the supernova was still bluish when the picture was taken. Supernovas type Ia are typically bluish when they are first discovered, but then they turn increasingly yellow and then reddish. Because the supernova is still bluish here, I believe that the picture was taken rather soon after the supernova was discovered. Maybe in April 1994? Possibly even in late March?

Any supernova will steadily fade, since it marks the destruction of a star. A star that goes type Ia supernova is totally consumed and destroyed by the explosion, and only a shockwave shell will remain. But this shell isn't necessarily very bright. Check out this page, which shows pictures of the shell left behind by Tycho Brahe's supernova back in 1572. Yes, that is a long time ago, but I find it interesting to see how the shell is completely invisible at optical wavelengths, yet clearly visible in X-rays.

So there is no "star" left in NGC 4526 for us to see. There might be a shell, but it is going to be very faint. According to the Wikipedia page I referred to, nothing is known about the remnant of Supernova 1994D.

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Re: APOD: Supernova 1994D and the Unexpected... (2015 May 31

Postby DavidLeodis » Tue Jun 02, 2015 7:31 pm

Thanks Ann for your helpful reply :).

The difference between the X-ray and optical images of Tycho Brahe's supernova's shell is amazing.

As to the image used as the APOD that shows Supernova 1994D I assume now that other than it showing a Type 1a supernova it has no connection with the High-Z Supernova Search project as that supernova happened too early for that project.


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