APOD: Perseid Night at Yosemite (2016 Aug 18)

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APOD: Perseid Night at Yosemite (2016 Aug 18)

Post by APOD Robot » Thu Aug 18, 2016 4:11 am

Image Perseid Night at Yosemite

Explanation: The 2016 Perseid meteor shower performed well on the night of August 11/12. The sky on that memorable evening was recorded from a perch overlooking Yosemite Valley, planet Earth, in this scene composed of 25 separate images selected from an all-night set of sequential exposures. Each image contains a single meteor and was placed in alignment using the background stars. The digital manipulation accounts for the Earth's rotation throughout the night and allows the explosion of colorful trails to be viewed in perspective toward the shower's radiant in the constellation Perseus. The fading alpenglow gently lights the west face of El Capitan just after sunset. Just before sunrise, a faint band zodiacal light, or the false dawn, shines upward from the east, left of Half Dome at the valley's far horizon. Car lights illuminate the valley road. Of course, the image is filled with other celestial sights from that Perseid night, including the Milky Way and the Pleiades star cluster.

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Re: APOD: Perseid Night at Yosemite (2016 Aug 18)

Post by Ann » Thu Aug 18, 2016 4:20 am

This picture explains why these meteors are called the Perseids. Just to the upper left of center in the sky is the loose grouping of stars called the Alpha Persei moving group. That's pretty much where the meteors seem to originate.

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Re: APOD: Perseid Night at Yosemite (2016 Aug 18)

Post by Boomer12k » Thu Aug 18, 2016 5:29 am

Cool...

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Re: APOD: Perseid Night at Yosemite (2016 Aug 18)

Post by Boomer12k » Thu Aug 18, 2016 5:33 am

Ann wrote:This picture explains why these meteors are called the Perseids. Just to the upper left of center in the sky is the loose grouping of stars called the Alpha Persei moving group. That's pretty much where the meteors seem to originate.

Ann
And yet, it is an illusion as we know the meteors are well within our own Solar System, and do not originate from Perseus at all, but our own comets and stuff,.... maybe we should reclassify them...LOL...

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Re: APOD: Perseid Night at Yosemite (2016 Aug 18)

Post by Moggie » Thu Aug 18, 2016 12:04 pm

Here is an idea, if you setup two cameras a few miles apart and both did this type of photo, could they be combined with a stereo viewer to see the trails hanging in front of the stars?

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Re: APOD: Perseid Night at Yosemite (2016 Aug 18)

Post by Chris Peterson » Thu Aug 18, 2016 1:24 pm

Boomer12k wrote:
Ann wrote:This picture explains why these meteors are called the Perseids. Just to the upper left of center in the sky is the loose grouping of stars called the Alpha Persei moving group. That's pretty much where the meteors seem to originate.
And yet, it is an illusion as we know the meteors are well within our own Solar System, and do not originate from Perseus at all, but our own comets and stuff,.... maybe we should reclassify them...LOL...
Actually, Perseus originates from our own Solar System. Constellations are historically defined by 2D asterisms, and in modern usage by 2D boundaries on the sky. In the 3D context of the Universe, they don't exist. So actually, saying the meteors have a radiant in a constellation makes perfect sense from a purely local standpoint. It is not an illusion that the meteors appear to originate from a single point on the sky (unless you want to classify the vanishing point of parallel lines as an "illusion").
Chris

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Re: APOD: Perseid Night at Yosemite (2016 Aug 18)

Post by heehaw » Thu Aug 18, 2016 1:43 pm

Moggie wrote:Here is an idea, if you setup two cameras a few miles apart and both did this type of photo, could they be combined with a stereo viewer to see the trails hanging in front of the stars?
Hey, I think that is a terrific idea, Moggie! I'd love to see it implemented!

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Re: APOD: Perseid Night at Yosemite (2016 Aug 18)

Post by Ann » Thu Aug 18, 2016 2:13 pm

Chris Peterson wrote: Actually, Perseus originates from our own Solar System. Constellations are historically defined by 2D asterisms, and in modern usage by 2D boundaries on the sky. In the 3D context of the Universe, they don't exist. So actually, saying the meteors have a radiant in a constellation makes perfect sense from a purely local standpoint. It is not an illusion that the meteors appear to originate from a single point on the sky (unless you want to classify the vanishing point of parallel lines as an "illusion").
Most certainly constellation Perseus is a human-made creation, but the Alpha Perseus Cluster is not.
Wikipedia wrote:
The Alpha Persei Cluster, also known as Melotte 20 or Collinder 39, is an open cluster in the constellation of Perseus. To the naked eye, the cluster consists of several blue spectral type B type stars. The most luminous member is the ~2nd magnitude white-yellow supergiant Mirfak, also known as Alpha Persei. Bright members also include Delta, Epsilon, Psi, 29, 30, 34 and 48 Persei. The Hipparcos satellite and infrared color-magnitude diagram fitting have been used to establish a distance to the cluster of ~172 pc.[2][3] The distance established via the independent analyses agree, thereby making the cluster an important rung on the cosmic distance ladder. The age of this cluster is about 50-70 million years.[1][4]


So although for example Beta Persei, Algol, has nothing whatsoever to do with the Alpha Perseus Cluster, the cluster in itself is a physical grouping in its own right. Boomer is correct to point out that while it looks as if the radiant point of the Perseids is very near the Alpha Persei Cluster, in reality the cluster and the Perseids have nothing to do with one another.

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Re: APOD: Perseid Night at Yosemite (2016 Aug 18)

Post by Chris Peterson » Thu Aug 18, 2016 2:51 pm

Ann wrote:
Chris Peterson wrote: Actually, Perseus originates from our own Solar System. Constellations are historically defined by 2D asterisms, and in modern usage by 2D boundaries on the sky. In the 3D context of the Universe, they don't exist. So actually, saying the meteors have a radiant in a constellation makes perfect sense from a purely local standpoint. It is not an illusion that the meteors appear to originate from a single point on the sky (unless you want to classify the vanishing point of parallel lines as an "illusion").
Most certainly constellation Perseus is a human-made creation, but the Alpha Perseus Cluster is not.
Agreed. But the Perseids are not named for the Alpha Perseus cluster.
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Re: APOD: Perseid Night at Yosemite (2016 Aug 18)

Post by Fred the Cat » Thu Aug 18, 2016 3:32 pm

To visually orient ourselves as to why we see meteor showers emanate from a point and time in the sky takes some doing.
swift_tuttle_orbit_v2.jpg

How we know which years will be better than others is even more perplexing. 8-)
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Re: APOD: Perseid Night at Yosemite (2016 Aug 18)

Post by Steve Dutch » Thu Aug 18, 2016 4:08 pm

Allow me to suggest that a photo is A - ONE - SINGLE - photo and that composites don't count. Stuff like this is on a par with movie special effects and is as realistic as "Independence Day." So can I submit my photo of a UFO landing near my house? It'll be a composite.

Also, this infuriates me because it merely misleads the public. Meteor showers aren't "showers." The photographer had to stay up all night to take those pictures. Imagine a fireworks display. Someone tosses a sparkler. "Whee!" Count to 50 slowly. Toss another sparkler. "Whee." What's the harm? So someone gets up at 3 AM, goes outside, sees a few shooting stars, goes back to bed, disappointed. Then he reads about global warming or some other problem and says "Scientists don't know what they're talking about. And I know from personal experience. They told me I'd see something, I went out in the middle of the night, and it wasn't there."

Meteor showers and comets are the two most irresponsibly hyped celestial phenomena. And it needs to stop.

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Re: APOD: Perseid Night at Yosemite (2016 Aug 18)

Post by Chris Peterson » Thu Aug 18, 2016 4:11 pm

Fred the Cat wrote:To visually orient ourselves as to why we see meteor showers emanate from a point and time in the sky takes some doing.
It doesn't need to be. Just think of a snowstorm. It doesn't matter which way the wind is blowing, or the direction the car is traveling. When you look out the window, all the snow is coming from a single point somewhere in front of you.
How we know which years will be better than others is even more perplexing. 8-)
It's actually quite simple in principle. We know when comets release material (near the Sun). And we know the orbit of each bit of released material, subject to an assortment of known forces. So it's really nothing more than a big, messy math problem to propagate the current orbit of a comet backwards through multiple perihelions, and then to propagate the position of millions of ejected particles back forward to the time of a current shower. If the Earth intersects a dense streamer of debris, it points to a strong shower. There are still some unknowns- particularly around the amount of material actually ejected. But most of the analysis is pretty deterministic. All you need is a fast computer- and that includes modern home PCs.
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Re: APOD: Perseid Night at Yosemite (2016 Aug 18)

Post by Chris Peterson » Thu Aug 18, 2016 4:19 pm

Steve Dutch wrote:Allow me to suggest that a photo is A - ONE - SINGLE - photo and that composites don't count.
So we can't talk about deep sky astronomical images as photos? Hubble images?

Allow me to suggest that a "photo" is a visual image that captures some concept we're trying to get across.
Meteor showers and comets are the two most irresponsibly hyped celestial phenomena. And it needs to stop.
This year's Perseid shower was very impressive, and performed almost exactly as predicted. You could go outside and watch for a half hour, and see dozens of meteors with a very obvious common radiant. Most meteor showers in recent years perform as predicted.

Comets are problematic. The models that predict comet brightness depend on variables that we frequently don't have values for. So there are wide ranges to the predictions. For obvious reasons, comets with any significant potential of being bright or otherwise interesting are called out by scientists, because it's important to have lots of observations as they get closer to the Sun. Sometimes the popular press does a poor job of explaining that the predictions are broad, and just give the most extreme possibility. Not sure what you can do about that- it's the way the press works. Scientists who release the information are doing just what they should be.
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Re: APOD: Perseid Night at Yosemite (2016 Aug 18)

Post by Fred the Cat » Thu Aug 18, 2016 5:10 pm

The Stardust mission was to collect dust samples from the coma of comet Wild 2. The ISS "Meteor" camera looks as if it is designed to analyze "the physical and chemical properties of the meteoroid dust". As the Earth enters an area with a "higher than usual" amount of comet dust one might think the same concept could be employed from ISS as on Stardust.

There must be some reason why it hasn't been tried (obviously the concentration would not be high). They do have good seats for the show. :ssmile:
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Re: APOD: Perseid Night at Yosemite (2016 Aug 18)

Post by geckzilla » Thu Aug 18, 2016 7:15 pm

Steve Dutch wrote:Also, this infuriates me because it merely misleads the public.
You make some good points, but I think the public is far more distrustful of scientists because of irresponsible dietary reporting than anything. Stupid in vitro studies on mice with preliminary results that get reported like they're final, definitive answers; eg coffee causes cancer! coffee doesn't cause cancer! coffee makes you live longer! coffee cuts years off your life!

It's these sorts of things that are clearly contradictory that happen within living memory and are essentially meaningless that make scientists look like complete and utter idiots. Who wouldn't think so?
Just call me "geck" because "zilla" is like a last name.

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Re: APOD: Perseid Night at Yosemite (2016 Aug 18)

Post by Chris Peterson » Thu Aug 18, 2016 10:02 pm

Fred the Cat wrote:The Stardust mission was to collect dust samples from the coma of comet Wild 2. The ISS "Meteor" camera looks as if it is designed to analyze "the physical and chemical properties of the meteoroid dust". As the Earth enters an area with a "higher than usual" amount of comet dust one might think the same concept could be employed from ISS as on Stardust.
I don't understand what you're suggesting. Collecting interplanetary dust particles on the ISS? That's been done. But the densityof material during meteor showers is orders of magnitude less than you find flying through the coma of a comet.
There must be some reason why it hasn't been tried (obviously the concentration would not be high). They do have good seats for the show.
Not such a good seat. The meteor camera is a fun little project, but unlikely to yield much information compared with ground cameras, which have a very good seat themselves, are inexpensive, and number in the tens of thousands.
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Re: APOD: Perseid Night at Yosemite (2016 Aug 18)

Post by Ann » Thu Aug 18, 2016 10:34 pm

Fred the Cat wrote:To visually orient ourselves as to why we see meteor showers emanate from a point and time in the sky takes some doing.

swift_tuttle_orbit_v2.jpg


How we know which years will be better than others is even more perplexing. 8-)
Thanks for the illustration, Fred! Maybe most others here had already visualized something similar, but for myself, being thick-headed when it comes to anything mathematical, it was a great help.

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Re: APOD: Perseid Night at Yosemite (2016 Aug 18)

Post by Fred the Cat » Fri Aug 19, 2016 3:55 pm

Chris Peterson wrote: I don't understand what you're suggesting. Collecting interplanetary dust particles on the ISS? That's been done. But the density of material during meteor showers is orders of magnitude less than you find flying through the coma of a comet.
I suspected that some ISS experiment may have collected interplanetary dust particles so that answers my question. If it could also be collected during a time when the Earth's orbit was passing through an area of the debris field of a specific comet, though sparse, I was just being curious if it might differ from comet to comet. Thanks!
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