Still the BOAT: Fermi Telescope reveals new feature in rare gamma-ray burst

Chance that first detected emission line is a noise fluctuation is one in half a billion.

See full article...

 

[Decoherent]

The newly detected spectral emission line was likely caused by the collision of matter and anti-matter [...]

Is this...normal? Where would it have acquired antimatter?

 

[SlyWalker]

Is this...normal? Where would it have acquired antimatter?

Some StarDestroyer(TM) death rays use antimatter these days, it's said to be more efficient and thus environment-friendly.

EDIT: the video shows that gamma-rays created during the star demolition can combine to create electron-positron pairs. These pairs may collide again and produce the visible signal.

 

[radulov]

Is this...normal? Where would it have acquired antimatter?

Yes. A few ways I an no expert in this field but:
https://en.wikipedia.org/wiki/Pair_production

 

[Thegs]

Is this...normal? Where would it have acquired antimatter?

One of the great mysteries of our models and understanding of the universe is that at the start, there should have been equal amounts of matter and anti-matter. We don't know why matter "won out" or where all the anti-matter that remained after annihilating with matter went. Speaking as to our models, there's an equal amount of anti-matter out there somewhere as there is matter in our entire observable universe. This might be a lead in figuring out where all that anti-matter is hiding.

Read more at CERN: The matter-antimatter asymmetry problem

 

[Troglodytes troglodytes indigenus]

"...about 12 MeV, compared to 2 or 3 MeB for visible light, per the authors."

Give over, visible light is in the recion of 2 or 3 eV.

 

[daveishereagain]

I love this stuff. Each discovery produces more questions that lead to more discoveries that lead to more questions and so on. We're just getting started trying to figure this place out. It's all a wonderful journey.

 

[rain shadow]

I suspect "2 or 3 MeB" is a typo.

 

[mcswell]

From the article: "The newly detected spectral emission line was likely caused by the collision of matter and anti-matter..." Can someone explain why this creates a line? I know about spectral lines that happen when electrons drop from one energy level in an atom to another, and I thought I'd heard somewhere about high energy spectral lines caused by nuclear changes. How does the collision between matter and anti-matter cause a line? Is it because the energy level represented by the line is the E=mc^^2 of the mass of the two particles? (red or blue shifted, I suppose, by the velocity of the particles relative to Earth, and maybe by the gravitational field of the collapsing star).

 

[fenncruz]

I suspect "2 or 3 MeB" is a typo.

It's a new unit "mega electron banana"

 

[fenncruz]

From the article: "The newly detected spectral emission line was likely caused by the collision of matter and anti-matter..." Can someone explain why this creates a line? I know about spectral lines that happen when electrons drop from one energy level in an atom to another, and I thought I'd heard somewhere about high energy spectral lines caused by nuclear changes. How does the collision between matter and anti-matter cause a line? Is it because the energy level represented by the line is the E=mc^^2 of the mass of the two particles? (red or blue shifted, I suppose, by the velocity of the particles relative to Earth, and maybe by the gravitational field of the collapsing star).

The collision of a particle and it's anti particle gives you a line at the sum of the rest masses of each particle (as their particle/anti particle then it's twice the mass of one of the particles).

 

[PhaseShifter]

How does the collision between matter and anti-matter cause a line? Is it because the energy level represented by the line is the E=mc^^2 of the mass of the two particles? (red or blue shifted, I suppose, by the velocity of the particles relative to Earth, and maybe by the gravitational field of the collapsing star).

This is pretty much it.

An alternative way of thinking about particle-antiparticle pairs is that they are excited states of a vacuum, and annihilation is just the vacuum going back to its ground state.

 

[Arstotzka]

The spectral emission lasted for about 40 seconds and reached a peak energy of about 12 MeV, compared to 2 or 3 MeB for visible light, per the authors.

As an American I need this in units I can understand. Like “Olympic swimming pools”, or since this is energy related, maybe in “microwave burritos reheated per minute”.

 

[Thegs]

From the article: "The newly detected spectral emission line was likely caused by the collision of matter and anti-matter..." Can someone explain why this creates a line? I know about spectral lines that happen when electrons drop from one energy level in an atom to another, and I thought I'd heard somewhere about high energy spectral lines caused by nuclear changes. How does the collision between matter and anti-matter cause a line? Is it because the energy level represented by the line is the E=mc^^2 of the mass of the two particles? (red or blue shifted, I suppose, by the velocity of the particles relative to Earth, and maybe by the gravitational field of the collapsing star).

It's a terminology thing. When you pass light that does not contain a continuous spectrum through a spectroscope it shows up as lines correlating to the wavelengths of the individual levels of energy of light that are passing through the spectroscope. Since a spectroscope passes light through a single slit before passing it through a prism, these are called the spectral emission lines (as opposed to what you are thinking of, the spectral absorption lines that occur when light that contains a continuous spectrum strikes or passes through a material that absorbs only certain wavelengths).

Spoiler: Image of a spectroscope, a continuous wavelength source passed through a spectroscope, and a discrete wavelength source passed through a spectroscope

Timwether, CC BY-SA 3.0 ( https://creativecommons.org/licenses/by-sa/3.0 ), via Wikimedia Commons

 

[skraft]

The newly detected spectral emission line was likely caused by the collision of matter and anti-matter

From Star Trek TOS, “The Changeling”:

NOMAD : This primitive matter-antimatter propulsion system is the main drive?
SCOTT: Aye.
NOMAD : Inefficiency exists in the antimatter input valve. I will effect repair.
(The indicator board goes crazy.)
SCOTT: How are you doing that?
NOMAD : The energy release controls are also most inefficient. I shall effect repair.
ENGINEER: Warp eight, Mister Scott, and increasing.
SCOTT: Throw your dampers.
ENGINEER: Warp nine.
SCOTT: Cut your circuits, all of them.
ENGINEER: Warp 10, Mister Scott.
SCOTT: Impossible. It can't go that fast.
ENGINEER: It just won't stop, Mister Scott. Warp eleven!
KIRK: Nomad, stop what you're doing. Scotty?
NOMAD : Is there a problem, Creator? I have increased engine efficiency fifty seven percent..

Alternate ending: KABOOM!!!

 

[oldArsReader]

…” it was an emission spectra “ …
“spectra” is plural, “spectrum” singular (and I have the data to back up that datum)

 

[dwrd]

As an American I need this in units I can understand. Like “Olympic swimming pools”, or since this is energy related, maybe in “microwave burritos reheated per minute”.

If my math is correct*, that works out to around 12.70314159 mega-burritos reheated/min, or nearly 1.21 jiggawats.


*no math was performed in the writing of this comment

 

[Rombobjörn]

"...about 12 MeV, compared to 2 or 3 MeB for visible light, per the authors."

Give over, visible light is in the recion of 2 or 3 eV.

Then an electron bel (eB) must be about one µeV.

 

[theotherjim]

Ars Technica: come for the science, stay for the smart-assery.

 

[YetAnotherAnonymousAppellation]

As an American I need this in units I can understand. Like “Olympic swimming pools”, or since this is energy related, maybe in “microwave burritos reheated per minute”.

Excellent point, but you are forgetting that the electronvolt is a tiny unit. So tiny that even millions of them are still tiny. Regardless, I'll take a whack at it,

I estimate that the "standard 1000 W nuker" can heat about 2 burritos per minute (burpem) so that is an energy absorbed of 60 kJ.

12 MeV is ~2x10^-12 J or 2 pJ.

That makes the conversion result ~320 femtoburpems.

Putting that in more comfortable units, that's about 6 million years to heat 1 burrito.

But all is not lost as this is the energy per X-ray photon and I'm sure that a burrito positioned in space would absorb a very large number of photons. I'd hazard a guess that the energy absorbed would be re-radiated as infrared without substantially changing the temperature of the burrito.

I hope you're not hungry.

 

[Arstotzka]

I hope you're not hungry.

I had a taco, so I’m good for now. But seriously, it is actually helpful for this context. You hear about planets being thousands of times bigger than Earth, stars that are a million times bigger, and other supermassive phenomena— and this, the biggest blast of radiation from deep space, wouldn’t pop a kernel of popcorn.

It is pretty neat to think about the mind-boggling extremes of scale at play.

 

[baloroth]

The collision of a particle and it's anti particle gives you a line at the sum of the rest masses of each particle (as their particle/anti particle then it's twice the mass of one of the particles).

Almost, the line is only at the rest mass if the electron-positron pair are, well, at rest. When that happens, the line is at 511 kev. This line was blue shifted to around 10 MeV, because they're produced inside the GRB by interacting gama rays, so they're either produced traveling extremely fast, or are accelerated to high speeds by the burst.

 

[RZetopan]

"...about 12 MeV, compared to 2 or 3 MeB for visible light, per the authors."

Give over, visible light is in the [region] of 2 or 3 eV.

And what is an "MeB"? A Mega electron Bolt?

 

[rhgedaly]

Obviously, B = Bolt(s) of lightning. Though I would also give partial credit for Burst(s) of lightning.

 

[DCStone]

I had a taco, so I’m good for now. But seriously, it is actually helpful for this context. You hear about planets being thousands of times bigger than Earth, stars that are a million times bigger, and other supermassive phenomena— and this, the biggest blast of radiation from deep space, wouldn’t pop a kernel of popcorn.

It is pretty neat to think about the mind-boggling extremes of scale at play.

Just remember that, as pointed out above, the eV value mentioned is per photon. The photon flux at the point of origin was almost certainly large enough to fry an observer to a crisp in a fractional fraction of a second - otherwise, we wouldn't have seen it this far away. You still wouldn't get your popcorn, but only because it was popper and vaporized at the same time.

 

[JPL-ACE]

Is this...normal? Where would it have acquired antimatter?

In these powerful events there is so much energy many things are created (and annihilated).

 

[Cool Physics]

"...about 12 MeV, compared to 2 or 3 MeB for visible light, per the authors."

Give over, visible light is in the recion of 2 or 3 eV.

Perhaps should be uMeV?? Dang, how do you get a mu?

 

[Deranged]

It's a terminology thing. When you pass light that does not contain a continuous spectrum through a spectroscope it shows up as lines correlating to the wavelengths of the individual levels of energy of light that are passing through the spectroscope. Since a spectroscope passes light through a single slit before passing it through a prism, these are called the spectral emission lines (as opposed to what you are thinking of, the spectral absorption lines that occur when light that contains a continuous spectrum strikes or passes through a material that absorbs only certain wavelengths).

Spoiler: Image of a spectroscope, a continuous wavelength source passed through a spectroscope, and a discrete wavelength source passed through a spectroscope

View attachment 86290

Timwether, CC BY-SA 3.0 ( https://creativecommons.org/licenses/by-sa/3.0 ), via Wikimedia Commons

Ok, but why is this the first time an “emission line” has been observed? The way you describe it, I understand it to always be some type of emission line with any type of electromagnetic type of event, or?

 

[DCStone]

Ok, but why is this the first time an “emission line” has been observed? The way you describe it, I understand it to always be some type of emission line with any type of electromagnetic type of event, or?

ICBW but my understanding is that it is the first time that such an emission line has been observed for this specific type of event, for reasons mentioned in the article.

 

[Arstotzka]

Just remember that, as pointed out above, the eV value mentioned is per photon. The photon flux at the point of origin was almost certainly large enough to fry an observer to a crisp in a fractional fraction of a second - otherwise, we wouldn't have seen it this far away. You still wouldn't get your popcorn, but only because it was popper and vaporized at the same time.

I hate it when people burn popcorn in the universe. The whole place stinks up.

 

[Mahler1911]

MeB = Microwave Burrito

 

[Albino_Boo]

Ok, but why is this the first time an “emission line” has been observed? The way you describe it, I understand it to always be some type of emission line with any type of electromagnetic type of event, or?

This is the 1st time that a spectrum has been detected that's actually strong enough not to be statistical noise. In pervious cases it has been there could be a spectrum but could be just noise.

 

[Deranged]

This is the 1st time that a spectrum has been detected that's actually strong enough not to be statistical noise. In pervious cases it has been there could be a spectrum but could be just noise.

Right, but what can one observe from a GRB when there’s no spectrum? Isn’t ALL electromagnetic radiation on a o part of the spectrum (not saying they’re autistic here )? It sounds like emission line refers to a specific part of the electromagnetic spectrum but the article doesn’t specify which part or what about that that makes it special.

 

[dr_lha]

Right, but what can one observe from a GRB when there’s no spectrum? Isn’t ALL electromagnetic radiation on a o part of the spectrum (not saying they’re autistic here )? It sounds like emission line refers to a specific part of the electromagnetic spectrum but the article doesn’t specify which part or what about that that makes it special.

This is the first time that an emission line has been seen in a Gamma-Ray Burst Spectrum in this energy range. Usually Gamma-ray spectra of GRBs are featureless, i.e. just looking like a curve, where a spectrum with lines looks like a curve with spikes overlaid. The line is indicative of an abundance of emission at a specific energy value being created. In optical spectra this would be due to changes in excitation levels in atoms or molecules, but at Gamma-ray energies can only be due to particles being annihilated in matter/anti-matter collisions (see for example the 511 keV annihilation line of electrons/positrons) due to the amount of energy involved and the discreet nature of the energy of the line. Lines in X-ray have been reported before, but none are firm or widely believed. My only concern with this paper is the lack of authors from the Fermi/GBM team on it. Full disclosure: I know a bunch of the authors and was a co-author on a previous paper on the BOAT (which they don't cite ).

 

[Chuckstar]

Right, but what can one observe from a GRB when there’s no spectrum? Isn’t ALL electromagnetic radiation on a o part of the spectrum (not saying they’re autistic here )? It sounds like emission line refers to a specific part of the electromagnetic spectrum but the article doesn’t specify which part or what about that that makes it special.

Forgive me if I’m over-explaining, but I thought this might help:

Most radiation in the universe is from thermal emissions — black body radiation, or an approximation thereto since most objects are not perfect black bodies. Thermal emission frequencies are emitted smoothly along a curve, defined by the temperature of the object.

When we take the spectrum of stars, for instance, what we mostly see is their black body radiation, with absorption lines mixed in, where specific atoms (in the star or intervening space) or molecules (in intervening space) have absorbed specific frequencies. Absorption lines are dimmer parts of the spectrum.

For some astronomical emissions, we’re not only seeing thermal emissions and absorption lines, but also emissions from other specific interactions. These other emissions take the form of an emission lines — places where the spectrum is a little brighter. Because these are narrowly-operating quantum processes, they emit at specific wavelengths, unlike thermal radiation which emits over a broad range of wavelengths.

For instance in galaxy spectra we see emission lines of hydrogen fluorescing in various ways. Molecular hydrogen fluoresces in far UV, for instance, so there will be a spike in that wavelength for galaxies with a lot of molecular hydrogen. Ionized hydrogen fluoresces in visible red. (I could have those details off a little, but you get the gist.). While fluorescence is a common source of non-thermal emissions, there are other sources, such as the matter/anti-matter annihilation which caused the BOAT’s emission line.

So when we’ve seen GRBs in the past, we just get a big blob that looks like very high temperature thermal radiation. This is the first time we’ve seen a spectrum that has a peak big enough to stand out as almost certainly an emission line. Note that there is still an underlying thermal emission spectrum. Just that there’s this spike that sticks up with greater brightness at the given wavelength.

 

[Deranged]

This is the first time that an emission line has been seen in a Gamma-Ray Burst Spectrum in this energy range. Usually Gamma-ray spectra of GRBs are featureless, i.e. just looking like a curve, where a spectrum with lines looks like a curve with spikes overlaid. The line is indicative of an abundance of emission at a specific energy value being created. In optical spectra this would be due to changes in excitation levels in atoms or molecules, but at Gamma-ray energies can only be due to particles being annihilated in matter/anti-matter collisions (see for example the 511 keV annihilation line of electrons/positrons) due to the amount of energy involved and the discreet nature of the energy of the line. Lines in X-ray have been reported before, but none are firm or widely believed. My only concern with this paper is the lack of authors from the Fermi/GBM team on it. Full disclosure: I know a bunch of the authors and was a co-author on a previous paper on the BOAT (which they don't cite ).

What an amazing and informative answer! You should have been quoted in this article since it explains a lot which wasn’t mentioned. Thank you so much

 

[Deranged]

Forgive me if I’m over-explaining, but I thought this might help:

Most radiation in the universe is from thermal emissions — black body radiation, or an approximation thereto since most objects are not perfect black bodies. Thermal emission frequencies are emitted smoothly along a curve, defined by the temperature of the object.

When we take the spectrum of stars, for instance, what we mostly see is their black body radiation, with absorption lines mixed in, where specific atoms (in the star or intervening space) or molecules (in intervening space) have absorbed specific frequencies. Absorption lines are dimmer parts of the spectrum.

For some astronomical emissions, we’re not only seeing thermal emissions and absorption lines, but also emissions from other specific interactions. These other emissions take the form of an emission lines — places where the spectrum is a little brighter. Because these are narrowly-operating quantum processes, they emit at specific wavelengths, unlike thermal radiation which emits over a broad range of wavelengths.

For instance in galaxy spectra we see emission lines of hydrogen fluorescing in various ways. Molecular hydrogen fluoresces in far UV, for instance, so there will be a spike in that wavelength for galaxies with a lot of molecular hydrogen. Ionized hydrogen fluoresces in visible red. (I could have those details off a little, but you get the gist.). While fluorescence is a common source of non-thermal emissions, there are other sources, such as the matter/anti-matter annihilation which caused the BOAT’s emission line.

So when we’ve seen GRBs in the past, we just get a big blob that looks like very high temperature thermal radiation. This is the first time we’ve seen a spectrum that has a peak big enough to stand out as almost certainly an emission line. Note that there is still an underlying thermal emission spectrum. Just that there’s this spike that sticks up with greater brightness at the given wavelength.

Also a great answer and definitely not over explaining! It might be me that doesn’t know the first thing about physics but I do think that this explanation is useful for more people than just me

 

[Keysh]

So when we’ve seen GRBs in the past, we just get a big blob that looks like very high temperature thermal radiation. This is the first time we’ve seen a spectrum that has a peak big enough to stand out as almost certainly an emission line. Note that there is still an underlying thermal emission spectrum. Just that there’s this spike that sticks up with greater brightness at the given wavelength.

You can also get broad, smooth spectra from non-thermal mechanisms such as synchrotron radiation, and that’s probably at least partly what’s producing the gamma rays in a gamma-ray burst. (The overall gamma-ray spectrum of a GRB is non-thermal.)

 

[Chuckstar]

You can also get broad, smooth spectra from non-thermal mechanisms such as synchrotron radiation, and that’s probably at least partly what’s producing the gamma rays in a gamma-ray burst. (The overall gamma-ray spectrum of a GRB is non-thermal.)

Thanks for the correction.

 

[DCStone]

Right, but what can one observe from a GRB when there’s no spectrum? Isn’t ALL electromagnetic radiation on a o part of the spectrum (not saying they’re autistic here )? It sounds like emission line refers to a specific part of the electromagnetic spectrum but the article doesn’t specify which part or what about that that makes it special.

For comparison, this is the X-Ray emission spectrum for an x-ray tube using a tungsten target - note the prominent lines superimposed on the continuous curve:




Note: I think the units on the x-axis got borked by whoever made the chart and it should be keV. The legend refers to the voltage used to accelerate electrons into the tungsten target to generate the x-rays. You can read more on the wikipedia entry. The mechanism for the gamma ray burst is going to be different, as noted in the article and comments.