APOD: MAGIC Star Trails (2011 Oct 14)

[APOD Robot]

MAGIC Star Trails

Explanation: Colorful star trails arc across the night in this surreal timelapse skyscape from the Roque de los Muchachos Observatory on the Canary island of La Palma. A reflection of the Earth's daily rotation on its axis, the star trails are also reflected in one of a pair of 17 meter diameter, multi-mirrored MAGIC telescopes. The MAGIC (Major Atmospheric Gamma Imaging Cherenkov) telescope itself is intended to detect gamma rays - photons with over 100 billion times the energy of visible light. As the high energy gamma rays impact the upper atmosphere they produce air showers of high-energy particles. A fast camera monitoring the multi-mirrored surface records in detail brief flashes of optical light, called Cherenkov light, created by the air shower particles Astronomers can then ultimately relate the optical flashes to cosmic sources of extreme gamma-rays.

<< Previous APOD

Discuss Any APOD

Next APOD >>

[/b]

[zerro1]

That is pretty intense!!

[Beyond]

NICE reflection off the antenna!! Saves it from being just another---y-a-w-n---bunch of circular star trails.

[Case]

The star trails show a broken pattern in the mirrors, not just interrupted, but the trails wander off a bit left and right. Does that mean the mirror segments are not properly aligned in this picture? Or is the current alignment 'close enough' for its purpose?

Would this scope be operating looking at the horizon, or is looking up the normal angle?

[Guest]

cool photo but wouldn't it be easier just to point a camera at the sky? I mean why bother filming a mirror in the first place?

[alter-ego]

The star trails show a broken pattern in the mirrors, not just interrupted, but the trails wander off a bit left and right. Does that mean the mirror segments are not properly aligned in this picture? Or is the current alignment 'close enough' for its purpose?
Would this scope be operating looking at the horizon, or is looking up the normal angle?

- The mirror elements are aligned, and do form a parabolic surface, but the elements are not in the same plane. The staggered placement explains the broked pattern in the star trails. The telescope is designed for light collection, and not for imaging in the classical telescope sense. Each element just needs to send photons to a multi-element detector for signal amplitude, and, I'm speculating, maybe providing some limited spatial imaging capability(?) along with having different performance characteristics (e.g spectral information).


- Viewing off-axis reflections (at a large angle) from a even a perfect parabolic mirror will of course look distorted, explaining the star-trail wander.
- The telescope will point at what it's looking at. The "camera" field of view~1.6°.

Almost 7 years to the day: http://apod.nasa.gov/apod/ap041015.html

[deathfleer]

photon with 100000000000 more intense than the light, but travelling at speed of light. how is it possible?

[Ann]

photon with 100000000000 more intense than the light, but travelling at speed of light. how is it possible?

Each photon has an energy that corresponds to a certain wavelength. The more energetic the photon, the shorter is the wavelength. In visible light, red light photons have an energy corresponding to about 700 nm, but blue-violet photons, which are more energetic, have shorter wavelengths corresponding to about 400 nm.

I have no idea how short the wavelengths of gamma ray photons are, but they must be very short indeed.

But they don't travel faster than light, all the same.

Ann

[NoelC]

That's a WAY COOL shot!

I've seen star trails in this telescope on La Palma before... In this video by Alex Cherney starting at about 00:56.

http://player.vimeo.com/video/26709319



-Noel

[starstruck]

That's quite a scary thought for a dull, wet Friday morning in October; photons with a hundred billion times the energy of light! Thank goodness for the atmosphere surrounding us, guess we'd all be fried to a crisp pretty darn quick otherwise!

Okay, 'stupid question time', from someone who is not an astro-scientist . . is it possible to actually see with our own eyes these optical flashes of Cherenkov radiation? I ask this because, on quite a few occasions over the years, when I have been out giving myself a crick in the neck staring up at a clear night sky on a moonless night, I have observed almost imperceptible flashes across the sky that seem to have no point of origin. I have always assumed I must be seeing very high or far-distant lightning flashes, but this has always puzzled me because I have noticed this phenomenon at times when the weather has seemed quiet and there have been no clouds or storm systems anywhere in the vicinity. Has anyone else ever noticed the same thing?

Maybe I should just have gone to the opticians for a check-up!

[NoelC]

I've seen what you're talking about. I also assumed it was distant lightning.

I believe the flashes measured by this telescope are quite tiny, though. A single photon, however energetic, crashing into the atmosphere and causing a cascade of thousands of particles isn't going to make a very bright flash. Note that they've built telescopes with 17 meters of light gathering capability and equipped with photomultipliers just to observe them.

-Noel

[nstahl]

Another great APOD. Thanks again everyone involved.

[orin stepanek]

Nice picture; but I often wondered what benefit is there in looking for gamma rays? I guess I could see it if we could use a gamma ray technology for an energy source of something. Also; wouldn't it be better for those magic telescopes to be housed for protection of the elements? Seems like they would have to be cleaned pretty often.

[biddie67]

What an interesting APOD! If I were just graduating from high school again, I'd love to be able to study in this field and work in places like this.

To NoelC and starstruck :: I envy your excellent eyesight - I'm going to try to be more observant in the future. Would the chances of seeing one of these flashes be correlated to increased aurora activity?

[copepod]

The most interesting part of the picture for me was how the star trails curve differently in the left half of the picture compared to the right edge. At first I thought this was distortion due to the camera lens, but realized this must be the trails of stars north and south of the equator (with stars above the equator cutting a straight line path behind the mirror telescope). I'd never considered that difference before, but a quick google search of "star trails fisheye equator" brought up just what I wanted to see: http://www.astrosurf.com/sguisard/Pagim ... _pole.html

[Chris Peterson]

photon with 100000000000 more intense than the light, but travelling at speed of light. how is it possible?

"Intensity" is determined by the photon flux. The more photons per unit time, the greater the intensity. Gamma rays are isolated events, and therefore they are low intensity. However, these extraterrestrial gamma rays have extremely short wavelengths compared with visible light (femtometers or less, compared with nearly a micrometer), so they have MUCH higher energies. A single gamma ray photon can carry the energy equivalent of a baseball thrown by a professional pitcher (although most are much less than this).

All photons travel at the same speed, c (or less in a medium), regardless of their energy (wavelength).

[Chris Peterson]

Okay, 'stupid question time', from someone who is not an astro-scientist . . is it possible to actually see with our own eyes these optical flashes of Cherenkov radiation? I ask this because, on quite a few occasions over the years, when I have been out giving myself a crick in the neck staring up at a clear night sky on a moonless night, I have observed almost imperceptible flashes across the sky that seem to have no point of origin.

No, the Cherenkov radiation produced by gamma rays in the atmosphere is too dim to see with the eyes. Flashes like you describe are normally a physiological phenomenon (called photopsia), which can be caused by various mechanical stresses on the retina, or by statistical noise in the retina, nerves, or brain. It is also possible, although rare, for a cosmic ray to penetrate the eye and produce a shower of visible photons which will be seen as a flash, or to directly strike the visual cortex, which can also produce a flash. But most of the time you're probably just seeing a spurious nerve signal unrelated to anything outside your body. (And yes, if you see such flashes with any frequency, you should see an ophthalmologist, as it can be a symptom of some serious eye or brain problems.)

Depending on your location and the time of year, it is also possible that distant lightning will create unlocalized flashes above your perception threshold. As a rule, I'd say that's the most likely explanation for flashes with no apparent origin, and the previously mentioned photopsia is the most likely explanation for flashes that appear to come from some point.

[Chris Peterson]

Nice picture; but I often wondered what benefit is there in looking for gamma rays?

Extraterrestrial gamma rays provide a window into the fundamental physics of stellar processes, black holes, and many other interesting astronomical things. So there is a tremendous scientific benefit to studying them- both for developing new theory, and testing existing theory.

[Chris Peterson]

The telescope is designed for light collection, and not for imaging in the classical telescope sense. Each element just needs to send photons to a multi-element detector for signal amplitude, and, I'm speculating, maybe providing some limited spatial imaging capability(?) along with having different performance characteristics (e.g spectral information).

I believe these are true imaging telescopes, not simple energy collectors. The cameras have 3.6° fields of view, and 576 pixels, which have individual imaging scales of 0.1 to 0.2 degrees, depending on their location in the sensor array.

[Beyond]

photon with 100000000000 more intense than the light, but travelling at speed of light. how is it possible?

Each photon has an energy that corresponds to a certain wavelength. The more energetic the photon, the shorter is the wavelength. In visible light, red light photons have an energy corresponding to about 700 nm, but blue-violet photons, which are more energetic, have shorter wavelengths corresponding to about 400 nm.

I have no idea how short the wavelengths of gamma ray photons are, but they must be very short indeed.

But they don't travel faster than light, all the same.

Ann

For anyone who is familar with Star Trekand who on the planet isn't?? Now you know why Photon torpedos are so powerful in the realm of scifi movies. You could say that they are a Real Blast In this case, it's a good thing that man can't do what he thinks/dreams of!!

[NoelC]

Can't do what he thinks of... Yet.

When Star Trek was new, flat panels with information displays all over the place were sci fi. Automatic doors were even special.

-Noel

[Beyond]

I was speaking of Photon Torpedos. Although i suppose that Lasers are close to Phasers, and lasers are now being used to blow up enemy mines. Gee, with all these sci fi thingies coming into being, where the heck is the food replicators, to cut down on the food bill

[BMAONE23]

Actually, Star Trek has driven the invention of many devices we use today
Here is one of them


(From WIKI)

[NoelC]

Yeah, except the smartphone has an embedded computer and far more features, though Captain Kirk didn't see dropped calls. He did have to sign a 5 year contract, though.

I always got a kick out of how they could call up and get someone in 1 second or less. "Kirk to Enterprise". Immediately he hears back "Scott here", with no annoying delay. No one manning the radio on the other end ever happened to be in the bathroom.

-Noel

[owlice]

What, there was no radio in the bathroom?!??