APOD: Perseid Meteors over Slovakia (2019 Aug 12)

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APOD: Perseid Meteors over Slovakia (2019 Aug 12)

Post by APOD Robot » Mon Aug 12, 2019 4:07 am

Image Perseid Meteors over Slovakia

Explanation: Tonight is a good night to see meteors. Comet dust will rain down on planet Earth, streaking through dark skies during the peak of the annual Perseid Meteor Shower. The featured composite image was taken during last year's Perseids from the Poloniny Dark Sky Park in Slovakia. The unusual building in the foreground is a planetarium on the grounds of Kolonica Observatory. Although the comet dust particles travel parallel to each other, the resulting shower meteors clearly seem to radiate from a single point on the sky in the eponymous constellation Perseus. The radiant effect is due to perspective, as the parallel tracks appear to converge at a distance, like train tracks. The Perseid Meteor Shower is expected to peak after midnight tonight, although unfortunately this year the sky will be brightened by a near full Moon.

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orin stepanek
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Re: APOD: Perseid Meteors over Slovakia (2019 Aug 12)

Post by orin stepanek » Mon Aug 12, 2019 11:48 am

Oh wow! And the one's exploded! 8-) :shock:
Orin

Smile today; tomorrow's another day!

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Re: APOD: Perseid Meteors over Slovakia (2019 Aug 12)

Post by Tszabeau » Mon Aug 12, 2019 1:11 pm

I imagine that some meteorites come in at oblique angles which make them “skip” off the atmosphere back into space as re-entering spacecraft are said to potentially do. Does anyone know if they leave a recognizable signature when that occurs... like a flash maybe? Might whole swarms skip off and back into space and then follow the earth in orbit around the sun??

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Re: APOD: Perseid Meteors over Slovakia (2019 Aug 12)

Post by Chris Peterson » Mon Aug 12, 2019 2:07 pm

Tszabeau wrote:
Mon Aug 12, 2019 1:11 pm
I imagine that some meteorites come in at oblique angles which make them “skip” off the atmosphere back into space as re-entering spacecraft are said to potentially do. Does anyone know if they leave a recognizable signature when that occurs... like a flash maybe? Might whole swarms skip off and back into space and then follow the earth in orbit around the sun??
Grazing meteors (not meteorites) happen when the radiant is very close to the horizon. They are characterized by generally long paths and fairly symmetric light curves. But it isn't usually possible to say for certain what you have from a single image. Meteor paths are determined by having them on two or more cameras set at different locations.

A grazing meteor that survives wouldn't follow Earth, it would be in a similar orbit to the original debris stream (which is a similar orbit to comet Swift-Tuttle).
Chris

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Tszabeau

Re: APOD: Perseid Meteors over Slovakia (2019 Aug 12)

Post by Tszabeau » Mon Aug 12, 2019 4:07 pm

Chris Peterson wrote:
Mon Aug 12, 2019 2:07 pm
Grazing meteors (not meteorites) happen when the radiant is very close to the horizon. They are characterized by generally long paths and fairly symmetric light curves. But it isn't usually possible to say for certain what you have from a single image. Meteor paths are determined by having them on two or more cameras set at different locations.

A grazing meteor that survives wouldn't follow Earth, it would be in a similar orbit to the original debris stream (which is a similar orbit to comet Swift-Tuttle).
Interesting. So a grazing meteor remains a meteor but a plunging meteor becomes a meteorite? I thought it was only the ones that reached the ground that were called meteorites. Is it possible that they become meteorites for a split-second and then resume being a meteor?
I assumed that, surely, the grazing meteors would have their courses altered significantly due to lose of momentum and change in trajectory like a ricocheting bullet.

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Re: APOD: Perseid Meteors over Slovakia (2019 Aug 12)

Post by neufer » Mon Aug 12, 2019 5:04 pm

Tszabeau wrote:
Mon Aug 12, 2019 4:07 pm
Chris Peterson wrote:
Mon Aug 12, 2019 2:07 pm

A grazing meteor that survives wouldn't follow Earth, it would be in a similar orbit
to the original debris stream (which is a similar orbit to comet Swift-Tuttle).
I assumed that, surely, the grazing meteors would have their courses altered significantly
due to lose of momentum and change in trajectory like a ricocheting bullet.
https://en.wikipedia.org/wiki/Earth-grazing_fireball wrote:
<<As an Earth-grazer passes through the atmosphere its mass and velocity are changed, so that its orbit, as it re-enters space, will be different from its orbit as it encountered Earth's atmosphere.>>
If the ~58 km/s Perseid Earth-grazer avoids breaking apart or burning up
I would assume that it probably will not be significantly slowed down.

The out going Perseid will have its angle gravitationally deflected towards the Earth
by only about 2º = ([Escape velocity = 11.186 km/s]/[58 km/s])2 radians.

However, any skipping off the Earth's atmosphere could easily cancel even this out.
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Chris Peterson
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Re: APOD: Perseid Meteors over Slovakia (2019 Aug 12)

Post by Chris Peterson » Mon Aug 12, 2019 5:05 pm

Tszabeau wrote:
Mon Aug 12, 2019 4:07 pm
Chris Peterson wrote:
Mon Aug 12, 2019 2:07 pm
Grazing meteors (not meteorites) happen when the radiant is very close to the horizon. They are characterized by generally long paths and fairly symmetric light curves. But it isn't usually possible to say for certain what you have from a single image. Meteor paths are determined by having them on two or more cameras set at different locations.

A grazing meteor that survives wouldn't follow Earth, it would be in a similar orbit to the original debris stream (which is a similar orbit to comet Swift-Tuttle).
Interesting. So a grazing meteor remains a meteor but a plunging meteor becomes a meteorite? I thought it was only the ones that reached the ground that were called meteorites. Is it possible that they become meteorites for a split-second and then resume being a meteor?
I assumed that, surely, the grazing meteors would have their courses altered significantly due to lose of momentum and change in trajectory like a ricocheting bullet.
Under current usage, a meteorite is any material that survives ablation. Meteorites do reach the ground, but it's correct to refer to them as such when they're still falling, but no longer ablating.

Meteor showers do not drop meteorites. Cometary material is too small and too fragile to survive to the ground. (There is one known exception, a Geminid fireball that almost certainly produced a meteorite, but the Geminids are unusual in having an asteroidal parent.) Except for the rare grazing meteor, all Perseid meteors burn up while still at a high altitude.

A grazing encounter with Earth certainly changes the orbit of a meteoroid. But the new orbit will probably be fairly similar to the original orbit. It won't be shifted into an orbit similar to Earth's.
Chris

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