Mach 1000 shock wave lights supernova remnant

Nov 25, 2013
This is a photograph of the Tycho supernova remnant taken by the Chandra X-ray Observatory. Low-energy X-rays (red) in the image show expanding debris from the supernova explosion and high energy X-rays (blue) show the blast wave, a shell of extremely energetic electrons. Credit: X-ray: NASA/CXC/Rutgers/K. Eriksen et al.; Optical (starry background): DSS

When a star explodes as a supernova, it shines brightly for a few weeks or months before fading away. Yet the material blasted outward from the explosion still glows hundreds or thousands of years later, forming a picturesque supernova remnant. What powers such long-lived brilliance?

In the case of Tycho's supernova remnant, astronomers have discovered that a reverse shock wave racing inward at Mach 1000 (1000 times the speed of sound) is heating the remnant and causing it to emit X-ray light.

"We wouldn't be able to study ancient without a reverse shock to light them up," says Hiroya Yamaguchi, who conducted this research at the Harvard-Smithsonian Center for Astrophysics (CfA).

Tycho's supernova was witnessed by astronomer Tycho Brahe in 1572. The appearance of this "new star" stunned those who thought the heavens were constant and unchanging. At its brightest, the supernova rivaled Venus before fading from sight a year later.

Modern astronomers know that the event Tycho and others observed was a Type Ia supernova, caused by the explosion of a . The explosion spewed elements like silicon and iron into space at speeds of more than 11 million miles per hour (5,000 km/s).

When that ejecta rammed into surrounding interstellar gas, it created a shock wave - the equivalent of a cosmic "sonic boom." That shock wave continues to move outward today at about Mach 300. The interaction also created a violent "backwash" - a reverse shock wave that speeds inward at Mach 1000.

"It's like the wave of brake lights that marches up a line of traffic after a fender-bender on a busy highway," explains CfA co-author Randall Smith.

The reverse shock wave heats gases inside the supernova remnant and causes them to fluoresce. The process is similar to what lights household fluorescent bulbs, except that the supernova remnant glows in X-rays rather than visible light. The reverse shock wave is what allows us to see supernova remnants and study them, hundreds of years after the supernova occurred.

"Thanks to the reverse shock, Tycho's supernova keeps on giving," says Smith.

The team studied the X-ray spectrum of Tycho's supernova remnant with the Suzaku spacecraft. They found that electrons crossing the reverse shock wave are rapidly heated by a still-uncertain process. Their observations represent the first clear evidence for such efficient, "collisionless" electron heating at the reverse shock of Tycho's supernova remnant.

The team plans to look for evidence of similar reverse in other young remnants.

Explore further: Image: 3C 397: An unusual galactic supernova remnant

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User comments : 27

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cantdrive85
1 / 5 (14) Nov 25, 2013
The process is similar to what lights household fluorescent bulbs, except that the supernova remnant glows in X-rays rather than visible light.

The process is similar, an electric current excites the "gas", just as a gas discharge or fluorescent light. No "shock wave" can make plasma glow in this manner.
tscati
1.2 / 5 (9) Nov 26, 2013
I'm not sure if their use of 'Mach 300' and 'Mach 1000' makes a lot of sense in this context. Mach 1 is the speed of sound in the surrounding medium. The gas cloud around a supernova is pretty thin stuff but is also pretty 'hot', so I have no idea what the 'speed of sound' would be under those conditions, so Mach 1000 is a meaningless phrase without knowing what Mach 1 is. And if they mean '760,000 mph' rather than 'Mach 1000' then they should say so.

Sloppy. I expect better from the Smithsonian.
IMP-9
3 / 5 (1) Nov 26, 2013
No "shock wave" can make plasma glow in this manner.


And why is this so?
cantdrive85
1 / 5 (13) Nov 26, 2013
why is this so?

No amount of localized kinetic heating is going to give the observed collective effects. These are decidedly electric plasma processes that lights up this plasma. Rarified interstellar gas does not glow from applying heat, only electrical effects can induce a glow.
Zephir_fan
Nov 26, 2013
This comment has been removed by a moderator.
cantdrive85
1 / 5 (13) Nov 26, 2013
To be "hot" enough to glow, it is a plasma. There are three well understood modes of plasma, arc, glow, and dark mode. There are well defined parameters that describes these phenomena. Unfortunately ignorance prevails in astrophysicists understanding of plasma.
Zephir_fan
Nov 26, 2013
This comment has been removed by a moderator.
IMP-9
5 / 5 (4) Nov 26, 2013
Rarified interstellar gas does not glow from applying heat, only electrical effects can induce a glow.


Why wouldn't pumping in energy cause ions to be put into higher energy levels? What you claim is wrong, thermal bremsstrahlung is a well understood process in plasmas which is observed in many many situations. It is a thermal effect caused by heating.
no fate
1 / 5 (8) Nov 26, 2013
"collisionless" electron heating at the reverse shock of Tycho's supernova remnant.

If it is collisionless...what is transmitting the "shockwave"?
Q-Star
5 / 5 (2) Nov 26, 2013
"collisionless" electron heating at the reverse shock of Tycho's supernova remnant.

If it is collisionless...what is transmitting the "shockwave"?


The electron heating is collisionless, they are heating not due to colliding with other particles, they are heating due to oscillating with and in the wave,,,, but the shock wave is the result of the SNR colliding with the ISM.
no fate
1 / 5 (8) Nov 26, 2013
"collisionless" electron heating at the reverse shock of Tycho's supernova remnant.

If it is collisionless...what is transmitting the "shockwave"?


The electron heating is collisionless, they are heating not due to colliding with other particles, they are heating due to oscillating with and in the wave,,,, but the shock wave is the result of the SNR colliding with the ISM.


More specifically, what MEDIUM is transmitting the shockwave in which the electrons are oscillating? Are we going to have a discussion on how a "shockwave" is transmitted without particles colliding now?
Q-Star
5 / 5 (1) Nov 26, 2013
More specifically, what MEDIUM is transmitting the shockwave in which the electrons are oscillating?


The ocillating (ya know waving) magnetic fields of the plasma that the electrons are in.

Are we going to have a discussion on how a "shockwave" is transmitted without particles colliding now?


Only if ya would like to. I'm on the "without collisions between the particles" side. Are saying that there must be collisions to transfer heat?
Q-Star
5 / 5 (1) Nov 26, 2013
Are we going to have a discussion on how a "shockwave" is transmitted without particles colliding now?


On second thought, let's not. Google up collisionless electron heating, there ya will find a wealth of information to bring ya to speed.
no fate
1 / 5 (7) Nov 26, 2013
Im up to speed thanks. Its nice to see you are for a change too. Cause ya aint on the defnition of a shockwave. It is defined as an increase in pressure...ironically, which isnt collisionless. IR photons transfer energy...not pressure. That was my dispute with the terminology. Magnetic compression is entirely different and will cause electrons to release photons of varying energies depending on the strength of the field. It isnt photonic heating as the electrons are too hot already...but im sure you were just about to correct that.
yyz
5 / 5 (4) Nov 26, 2013
A preprint of "New Evidence for Efficient Collisionless Heating of Electrons at the Reverse Shock of a Young Supernova Remnant" is available here: http://arxiv.org/abs/1310.8355
Q-Star
5 / 5 (1) Nov 26, 2013
A preprint of "New Evidence for Efficient Collisionless Heating of Electrons at the Reverse Shock of a Young Supernova Remnant" is available here: http://arxiv.org/abs/1310.8355


Thanks, it's a good paper. New evidence, not so new physics.
RealScience
not rated yet Nov 26, 2013
@tscati - the article says that the outwards flow is at 11,000,000 MPH, and also says that it is Mach 300. Therefore what they are using as Mach 1 is 11,000,000 / 300 MPH = ~36,000 MPH.

That is ~50x the speed of sound in our atmosphere, so they are clearly talking about the speed of sound in thin-but-hot gas that surrounds Tycho's supernova remnant.
no fate
1 / 5 (7) Nov 27, 2013
Opening of the paper:

"Although collisionless shocks are ubiquitous in astrophysics, certain key aspects of them are not well understood. In particular, the process known as collisionless electron heating, whereby electrons are rapidly energized at the shock front, is one of the main open issues in shock physics."

The paper goes on to surmize the "evidence" for the "shock" by stating the energies of ions in their various states and how the calculations were performed. Measured very well. This is the only statement made as to the nature of the "shock" itself:

"Therefore, collisionless processes involving
collective interactions between particles and electromagnetic
fields must be responsible for the shock"

That is what I said above dumbed down to the PHD level I guess. All the math showing calculations that were performed to explain the temperatures of the particle interactions with each other and the "shock" front, but that is the best they have about the "shock"
itself.
no fate
1 / 5 (7) Nov 27, 2013
Which makes it the best you have as well Qstar. Using that paper offered up by another poster as your understanding of "shock physics" fits perfectly their summation of their understanding....again:

"Therefore, collisionless processes involving
collective interactions between particles and electromagnetic
fields must be responsible for the shock"

"Khan....I'm laughing at the superior intellect"

(just like last week)
Q-Star
not rated yet Nov 27, 2013
Which makes it the best you have as well Qstar. Using that paper offered up by another poster as your understanding of "shock physics" fits perfectly their summation of their understanding....again:

"Therefore, collisionless processes involving
collective interactions between particles and electromagnetic
fields must be responsible for the shock"

"Khan....I'm laughing at the superior intellect"

(just like last week)


Hey, I didn't write the paper, or have any input on the naming or development of the terminology or jargon in this area, why would ya take your umbrage out on me? This isn't exactly a new area, but the words used to describe it are what they are, there's nothing I can do about that. Ya seem to wish to take offense at the slightest misperception of a person's comment. Why don't ya go rewrite the textbooks that ya are so offended with, I only read them, not created them.
no fate
1 / 5 (7) Nov 27, 2013
I have no "umbrage". What I do is speak down to you the same way you do to me, I just wait for you to do it first because I know you will and then do it back more effectively. You posted after mine in a civil enough manner as though you knew about the mechanics involved here, implied with your second post as though I didn't ( the oscillating, ya know waving)then subsequently displayed your true understanding by delaring that there was "not so new physics" here. This was true of the paper as it is only describing what we are seeing. The actual physics part comes in with the mechanics of the collisionless interactions of which "certain key aspects are not well understood"...by the mainstream. This makes it a "new area", or we can call it poorly understood old area...either way.

I'm not offended by books, just people who think they know more than others because they have read those books. As far as word choice, dictionary meanings will suffice, do PHD's use dictionaries?

shockwave
cantdrive85
1 / 5 (14) Nov 27, 2013
There are no "shockwaves" in plasma, there are sheaths and double layers though. DL's and the collisionless electrons are well known plasma processes. Such a notion explains why Q nor mainstream astros don't understand what's going on here, these are plasma processes which they are completely ignorant.
IMP-9
5 / 5 (6) Nov 27, 2013
There are no "shockwaves" in plasma


You've gone off the deep end now, but I know you won't take that from me. Took me all of 30 seconds to find a paper by Alfven (the later years) where he referred to shock waves. Funny given that you claim they don't exist.

http://adsabs.har...64....3A

There are also many thousands of IEEE plasma physics papers on shocks. I think you should ovoid claims that plasma don't do this and that as going by this time and last you don't know very much about it.
triplehelix
1 / 5 (8) Nov 28, 2013
"When a star explodes as a supernova, it shines brightly for a few weeks or months before fading away. Yet the material blasted outward from the explosion still glows hundreds or thousands of years later, forming a picturesque supernova remnant. What powers such long-lived brilliance? "

Really?

Look at any terrestrial explosion, while slightly different, still applies the same physics almost.

If you see a grenade or bomb go off, you see the flames lick up and it's the last thing you see. The centre explosion is just a quick flash, and then the outside flames take longer to dissapear.

You're propelling the fuel outwards, with massive energies. So guess where you're going to see light/heat through the telescope. The outward moving jets.

This is kind of...obvious...
IMP-9
5 / 5 (1) Nov 28, 2013
You're propelling the fuel outwards, with massive energies.


What fuel though? The explosion has happened, this is a shock not an explosion.
triplehelix
1 / 5 (7) Nov 28, 2013
You're propelling the fuel outwards, with massive energies.


What fuel though? The explosion has happened, this is a shock not an explosion.



?? Really? The material blasted from the sun. A sun goes supernova. It basically spits out it's leftover fuel, and flings it everywhere. The energy is moving outwards, from the centre of the sun. The centre, similar to a grenade is going to flash, this is what lasts a few weeks/months, but will burn up the fuel quickly, because most of the matter from that sun will have been jetted too far to be used.

The super energetic particles that have just been spat at 3-5% the speed of light will continue to glow due to such energies, which have dispersed from the centre originating part of the supernova.

IMP-9
5 / 5 (2) Nov 29, 2013
The material blasted from the sun.


The conditions to sustain fusion no longer exist. The shock is many, many times less dense than the core of the star. While this material may have fueled the star it will not fuel the shock because it can no longer fuse. In such a tenuous gas the gamma rays would be very detectable.
triplehelix
1 / 5 (7) Nov 29, 2013
I never said fusion.

Fact is light is seen, so it stands to reason something is making that light. The star throws out particles, and shockwave energies are obviously exciting these particles enough to give out visible light.

I just genuinely don't see the mystery here....
IMP-9
5 / 5 (3) Nov 29, 2013
I never said fusion.


So what is the fuel then, back to my original question? There is energy sources is most certainly the shock itself. That's what's causing the light.