APOD: A Perseid Below (2021 Aug 08)

Comments and questions about the APOD on the main view screen.
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APOD: A Perseid Below (2021 Aug 08)

Post by APOD Robot » Sun Aug 08, 2021 4:06 am

Image A Perseid Below

Explanation: Earthlings typically watch meteor showers by looking up. But this remarkable view, captured on August 13, 2011 by astronaut Ron Garan, caught a Perseid meteor by looking down. From Garan's perspective onboard the International Space Station orbiting at an altitude of about 380 kilometers, the Perseid meteors streak below, swept up dust left from comet Swift-Tuttle heated to incandescence. The glowing comet dust grains are traveling at about 60 kilometers per second through the denser atmosphere around 100 kilometers above Earth's surface. In this case, the foreshortened meteor flash is right of frame center, below the curving limb of the Earth and a layer of greenish airglow, just below bright star Arcturus. Want to look up at a meteor shower? You're in luck, as the 2021 Perseids meteor shower peaks this week. This year, even relatively faint meteors should be visible through clear skies from a dark location as the bright Moon will mostly absent.

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Re: APOD: A Perseid Below (2021 Aug 08)

Post by VictorBorun » Sun Aug 08, 2021 4:43 am

My guess: exposure=0.3 second, velocity=60 km/s, track=20 km

Avent

Re: APOD: A Perseid Below (2021 Aug 08)

Post by Avent » Sun Aug 08, 2021 5:59 am

Why does this website make me think about continuity of government.

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Re: APOD: A Perseid Below (2021 Aug 08)

Post by Steve Randall » Sun Aug 08, 2021 7:51 am

If a similar grain of dust hit the ISS, what would the consequence be? Has the ISS ever been punctured/damaged by a meteor?

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Stuffed Whipple shields

Post by neufer » Sun Aug 08, 2021 1:01 pm

Steve Randall wrote:
Sun Aug 08, 2021 7:51 am

If a similar grain of dust hit the ISS, what would the consequence be? Has the ISS ever been punctured/damaged by a meteor?
https://en.wikipedia.org/wiki/International_Space_Station#Orbital_debris_threats wrote:
Click to play embedded YouTube video.
<<Ballistic panels, also called micrometeorite shielding, are incorporated into the [ISS] to protect pressurised sections and critical systems. The type and thickness of these panels depend on their predicted exposure to damage. The station's shields and structure have different designs on the ROS and the USOS. On the USOS, Whipple Shields are used. The US segment modules consist of an inner layer made from 1.5–5.0 cm-thick aluminium, a 10 cm-thick intermediate layers of Kevlar and Nextel, and an outer layer of stainless steel, which causes objects to shatter into a cloud before hitting the hull, thereby spreading the energy of impact. On the ROS, a carbon fibre reinforced polymer honeycomb screen is spaced from the hull, an aluminium honeycomb screen is spaced from that, with a screen-vacuum thermal insulation covering, and glass cloth over the top.

The Whipple shield or Whipple bumper, invented by Fred Whipple, is a type of hypervelocity impact shield used to protect crewed and uncrewed spacecraft from collisions with micrometeoroids and orbital debris whose velocities generally range between 3 and 18 kilometres per second. In contrast to monolithic shielding of early spacecraft, Whipple shields consist of a relatively thin outer bumper spaced some distance from the main spacecraft wall. The bumper is not expected to stop the incoming particle or even remove much of its energy, but to break up and disperse it, dividing the original particle energy among many fragments that fan out between bumper and wall. The original particle energy is spread more thinly over a larger wall area, which is more likely to withstand it. A direct analogy is that a lighter bullet resistant vest is needed to stop a load of birdshot than a single rifle bullet with the same total mass and kinetic energy. Although a Whipple shield lowers total spacecraft mass compared to a solid shield, lower mass being always desirable in spaceflight, the extra enclosed volume may require a larger payload fairing.

There are several variations on the simple Whipple shield. Multi-shock shields, like the one used on the Stardust spacecraft, use multiple bumpers spaced apart to increase the shield's ability to protect the spacecraft. Whipple shields that have a filling in between the rigid layers of the shield are called stuffed Whipple shields. The filling in these shields is usually a high-strength material like Kevlar or Nextel aluminium oxide fiber. The type of shield, the material, thickness and distance between layers are varied to produce a shield with minimal mass that will also minimize the probability of penetration. There are over 100 shield configurations on the International Space Station alone, with higher-risk areas having better shielding.>>
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Re: APOD: A Perseid Below (2021 Aug 08)

Post by Sa Ji Tario » Sun Aug 08, 2021 2:28 pm

VictorBorun wrote:
Sun Aug 08, 2021 4:43 am
My guess: exposure=0.3 second, velocity=60 km/s, track=20 km
Victor, the distance would be 18 km

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Re: APOD: A Perseid Below (2021 Aug 08)

Post by johnnydeep » Sun Aug 08, 2021 2:58 pm

Not sure where this is on the surface of the Earth, but are those orange spot clusters to the right of the meteor lightning or city lights?
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Re: APOD: A Perseid Below (2021 Aug 08)

Post by orin stepanek » Sun Aug 08, 2021 4:56 pm

perseid_iss_4256.jpg
Nice shot of the meteor. 8-)
astonished-funny-dog-with-big-eyes-picture-id480540092.jpg
Doggie ready for Perseid meteor show! :mrgreen:
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Re: APOD: A Perseid Below (2021 Aug 08)

Post by neufer » Sun Aug 08, 2021 8:26 pm

johnnydeep wrote:
Sun Aug 08, 2021 2:58 pm

Not sure where this is on the surface of the Earth,
but are those orange spot clusters to the right of the meteor lightning or city lights?
Also not sure where this is on the surface of the Earth they could also be forest fires: Or the gas/oil fields that contribute to them:
Art Neuendorffer

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Re: APOD: A Perseid Below (2021 Aug 08)

Post by bill ritchie » Sun Aug 08, 2021 10:04 pm

Fascinating photo. Around 60 degrees North at around a local time of 2300, looking North West, gives the correct Sun / star / Perseus aspects for 13th August 2011 (or any other year!). That doesn't help much with longitude.

But whilst orienting the stars, I noticed the double red object about 4.5 meteor tail lengths away and almost in line with the tail. There's no double red star there and it is certainly not Mars. Is it another orbiting object, perhaps about to rendezvous?

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Re: APOD: A Perseid Below (2021 Aug 08)

Post by Chris Peterson » Sun Aug 08, 2021 11:20 pm

bill ritchie wrote:
Sun Aug 08, 2021 10:04 pm
Fascinating photo. Around 60 degrees North at around a local time of 2300, looking North West, gives the correct Sun / star / Perseus aspects for 13th August 2011 (or any other year!). That doesn't help much with longitude.

But whilst orienting the stars, I noticed the double red object about 4.5 meteor tail lengths away and almost in line with the tail. There's no double red star there and it is certainly not Mars. Is it another orbiting object, perhaps about to rendezvous?
I think it's probably just a hot pixel. An artifact (somewhat distorted by JPEG compression).
Chris

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johnnydeep
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Re: APOD: A Perseid Below (2021 Aug 08)

Post by johnnydeep » Mon Aug 09, 2021 3:01 pm

neufer wrote:
Sun Aug 08, 2021 8:26 pm
johnnydeep wrote:
Sun Aug 08, 2021 2:58 pm

Not sure where this is on the surface of the Earth,
but are those orange spot clusters to the right of the meteor lightning or city lights?
Also not sure where this is on the surface of the Earth they could also be forest fires: Or the gas/oil fields that contribute to them:
Yeah, now that you've mention it, fire is probably the more likely source given the orange color.
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Re: APOD: A Perseid Below (2021 Aug 08)

Post by drjhammond » Wed Aug 11, 2021 12:08 am

I see the constellation Corona Borealis and the meteor track doesn't seem to align in a way that it "radiated" from Perseus when I compare it with a star chart. Why is the photographer or anyone sure this is a Perseid?