Starship Asterisk*

by **Anthony Barreiro** » Mon Nov 26, 2012 11:33 pm

I'm catching up on apod's after a few days holiday from screens and keyboards. This image and the longer video are truly beautiful. Thank you Stephane.

by **BillBixby** » Sun Nov 25, 2012 1:30 am

Neufer, thank you for the movie link. The best of their era... Edmond G. Robinson, Bacall and Bogart, (Burt Lancaster was of another era), AND James (Jimmy) Cagney. They don't make'm like they us'ta. (Oh, the shame). Another shame, Jimmy's sailing yacht, the Swift of Ipswich, needs funds for refitting. A class 3 or four tallship. Wish I would win one of the Lotteries. Then I could be seasick across the seven seas. This many days after the original posting, I figure I can get away with the off-topic comment.

http://en.wikipedia.org/wiki/Swift_of_Ipswich
http://tollway.com/swift/info.htm

Thanks again,
Bill

by **neufer** » Fri Nov 23, 2012 5:16 pm

jch wrote:
SteedJoy@gmail.com wrote:
Great! But the shooting star seems not come out from Leo ...
I would agree, radiant of this meteor is maybe somewhere in Hydra.

Hydra...foiled again

by **jch** » Fri Nov 23, 2012 4:42 pm

SteedJoy@gmail.com wrote:Great! But the shooting star seems not come out from Leo ...

I would agree, radiant of this meteor is maybe somewhere in Hydra.
Josef

by **Chris Peterson** » Fri Nov 23, 2012 8:42 am

Ron wrote:Can recall a meteorite shower back about 30 years that was strikingly vividly green.
At the time, this was said to be because they contained (considerable) nickel ??

Doubtful. Meteor showers are generally created by fragile debris (low metal) which does not make it very deep into the atmosphere. It's much more likely that the color was caused by atmospheric ionization (as with the Leonids).

Is there any mechanism to determine if these Leonids are sand grains, pea sized or football sized grazing the atmosphere ?
Seems to me if they are all tarred with the same brush, size wise, we are totally missing this detail.... ??

Their brightness is closely related to their mass. Photometric measurements allow for reasonable size estimates.

by **Ron** » Fri Nov 23, 2012 6:39 am

Can recall a meteorite shower back about 30 years that was strikingly vividly green.
At the time, this was said to be because they contained (considerable) nickel ??

Is there any mechanism to determine if these Leonids are sand grains, pea sized or football sized grazing the atmosphere ?
Seems to me if they are all tarred with the same brush, size wise, we are totally missing this detail.... ??

by **neufer** » Fri Nov 23, 2012 4:18 am

Beyond wrote:
Back about 30 years ago, i had bought some 'colorful' fireplace logs that gave off colors when they burned. I remember that it said the green color was from copper or copper oxide. The colors were nice, while they lasted, which wasn't too long.

Perhaps the Leonids are lost pieces of the Captain's log from the Enterprise.

by **Beyond** » Fri Nov 23, 2012 3:15 am

Back about 30 years ago, i had bought some 'colorful' fireplace logs that gave off colors when they burned. I remember that it said the green color was from copper or copper oxide. The colors were nice, while they lasted, which wasn't too long.

by **neufer** » Fri Nov 23, 2012 2:57 am

BDanielMayfield wrote:
Thanks Ann and Chris for your well reasoned answers. I now realize that meteor colors are due to ionized atmospheric gasses. Therefore the colors we can record is for basically the same reason that the auroras are so often green; ionized oxygen. Perhaps today’s apod is of a meteoroid that stayed inside the ozone layer for most of it’s path?

But also, thanks Nuefer for your quick witted ability to make the most of misconceptions. Your “Coppers” post was so cool I sort of wish it were true…

Yes. Only Wikipedia seems to suggest that the green could be from copper (rather than magnesium say).

In the upper air there is little disintegration of the meteor and the green is from ionized oxygen similar to aurora.

In the lower air (as seen in the far upper right of the APOD) the meteor finally burns up
giving off mostly silicate red & iron yellow (and then, lastly, possibly bright magnesium - blue/green).

The color change is more apparent in:

. http://www.dl-digital.com/astrophoto/leonid.htm
. http://www.robertreeves.com/leonid3.jpg
. http://apod.nasa.gov/apod/ap020811.html

(I still stick with my butte analysis, however.)

by **Chris Peterson** » Thu Nov 22, 2012 6:02 pm

BDanielMayfield wrote:Thanks Ann and Chris for your well reasoned answers. I now realize that meteor colors are due to ionized atmospheric gasses. Therefore the colors we can record is for basically the same reason that the auroras are so often green; ionized oxygen. Perhaps today’s apod is of a meteoroid that stayed inside the ozone layer for most of it’s path?

To be clear, meteors do produce colors that are related to their constituent materials. These are readily observed spectroscopically. It's just that in most cases, these relatively dim and narrowband emissions are only responsible for a small part (if any) of the color we actually observe visually (or which show up in typical camera images).

by **BDanielMayfield** » Thu Nov 22, 2012 5:51 pm

Thanks Ann and Chris for your well reasoned answers. I now realize that meteor colors are due to ionized atmospheric gasses. Therefore the colors we can record is for basically the same reason that the auroras are so often green; ionized oxygen. Perhaps today’s apod is of a meteoroid that stayed inside the ozone layer for most of it’s path?

But also, thanks Nuefer for your quick witted ability to make the most of misconceptions. Your “Coppers” post was so cool I sort of wish it were true…

Bruce

by **Chris Peterson** » Thu Nov 22, 2012 4:58 pm

Ann wrote:The meteor trail in today's APOD is very green, with no trace of blue or cyan whatsoever. We may note that the stars in the picture are mostly bluish-white, and that nothing else in the picture is green. This suggests to me that the green color is real.

However, there really are Leonids and other meteorites that are truly blue-green, particularly the very bright ones. This bright fireball photographed by Arne Danielsen is a typical example.

Keep in mind that most color meteor images are made with cameras designed for terrestrial photography. Just as when such cameras are used for astronomical imaging, their color fidelity tends to be very poor. Color cameras are not designed to accurately replicate the color of sources that consist of narrow band emissions. In addition, the apparent hue- both visually and photographically- changes with the intensity of the source. Two identical cameras set to different ISO values will show the same meteor with a different apparent color.

There is every reason to believe that the same meteor, captured by three different cameras, will produce trails that are blue, cyan, and green. And that's even before the imager introduces any processing.

by **Ann** » Thu Nov 22, 2012 4:42 pm

BDanielMayfield wrote: Also, evidently my slight color blindness might be at work here. I perceive these meteor streaks as being very green. Are other’s seeing them as bluish-green?

Bruce

: Click to view full size image

The meteor trail in today's APOD is very green, with no trace of blue or cyan whatsoever. We may note that the stars in the picture are mostly bluish-white, and that nothing else in the picture is green. This suggests to me that the green color is real.

However, there really are Leonids and other meteorites that are truly blue-green, particularly the very bright ones. This bright fireball photographed by Arne Danielsen is a typical example.

Ann

by **BDanielMayfield** » Thu Nov 22, 2012 4:18 pm

Thanks Nuefer, that’s fascinating. I hadn’t thought of chemically induced coloration. So then I guess it can it be inferred that comet Tempel-Tuttle was chock full o’ coppers?

I’ve seen greenish and multicolored flames when burning driftwood that has soaked up sea salt. This rapid oxidation (aka fire!) would then be happening as comet grains streak though the atmosphere. Great Balls O’ Fire ya’ll, dem dar shootin’ stars really are on fire!

Also, evidently my slight color blindness might be at work here. I perceive these meteor streaks as being very green. Are other’s seeing them as bluish-green?

Bruce

P.S. Ah, I see that I have been Nuefered… The above was composed prior to my reading Chris Peterson’s comments…

by **Chris Peterson** » Thu Nov 22, 2012 3:37 pm

Ron wrote:How do we know these are grain of sand size, and not golf ball size or watermelon size. ?

There is a well established relationship between the intensity profile of a meteor and the mass of the meteoroid. In addition, Leonids and other meteor showers are well characterized by radar.

The meteoroid that produced the fireball in today's image was certainly not the size of a grain of sand, however! While a typical Leonid meteor is one or two millimeters across, a fireball like this is probably a centimeter or larger- a marble, not a piece of sand.

On another track, do these ever dive straight down into the atmosphere, rather than streak across the sky. Does that produce a different type of track - or photo ?

All of the meteoroids are moving parallel to one another, in a zone larger than the diameter of the Earth. The angle of an individual meteor in the atmosphere is determined by where it strikes- if it is in the center of Earth's path through the field, the path will be directly down toward the ground; if it nearly misses the planet completely, it will be an Earth-grazer like that in the image, moving parallel to the ground. When you are observing a meteor shower, meteors close to the radiant are moving towards you, and typically are short. As you see meteors farther from the radiant, they are traveling more obliquely with respect to the observer, and tend to have longer paths. If you view when the radiant is overhead, meteors near the radiant are heading almost straight towards the ground, while meteors near the horizons are almost parallel to the ground.

by **Chris Peterson** » Thu Nov 22, 2012 3:24 pm

BDanielMayfield wrote:Back to my question: Why is the color of today’s leonid mostly green? I know that the color is a function of the meteor’s temperature, but in today’s example the green extends for an enormous length, whereas in the apod of 2 day’s ago the green sections were often shorter, with red tinted white from about the center forward. What do these color variations tell us about the meteors that made them?

Visual and photographic color tell very little about what makes up a meteoroid. For the most part, the color we see is produced by ionized atmospheric gas. The green color comes from ionized oxygen, and is most apparent when the temperature of the meteor is low enough that the green isn't lost in the white blackbody output. Here we have an Earth grazer which never reaches very deep into the air, and is therefore able to survive a long time and not quickly burn up- thus the long green trail.

by **neufer** » Thu Nov 22, 2012 3:16 pm

BDanielMayfield wrote:
Why is the color of today’s leonid mostly green? I know that the color is a function of the meteor’s temperature, but in today’s example the green extends for an enormous length, whereas in the apod of 2 day’s ago the green sections were often shorter, with red tinted white from about the center forward. What do these color variations tell us about the meteors that made them?

http://en.wikipedia.org/wiki/The_Thin_Blue_Line_%28emblem%29 wrote:
<<The Thin Blue Line is a symbol in use in the United States by law enforcement officers and others. The purpose of the symbol is a topic of debate. The conceptual "Thin Blue Line" is derived from the historical Thin Red Line. The Blue line stands for the Law Enforcement Officers. Proponents of the symbol assert that the identifier is intended to show support for police.>>

Click to play embedded YouTube video.

http://en.wikipedia.org/wiki/Meteoroid wrote:
<<The visible light produced by a meteor may take on various hues, depending on the chemical composition of the meteoroid, and the speed of its movement through the atmosphere. As layers of the meteoroid abrade and ionize, the color of the light emitted may change according to the layering of minerals. Possible colors (and elements producing them) include:

[list] orange/yellow (sodium)
yellow (iron)
blue/green (copper)
purple (potassium)
red (silicate)[/list]

by **neufer** » Thu Nov 22, 2012 2:59 pm

Ron wrote:
How do we know these are grain of sand size, and not golf ball size or watermelon size. ?

Something that leaves a streak that long is going to burn up a lot more surface than something that only leaves a short trail.??

We know exactly how fast it is moving (i.e., Tempel-Tuttle's orbit crossing Earth's orbit gives: v = 72 km/s).

We know exactly how much light energy it's emitting: E_l.

Assuming that most of the kinetic energy is turned into light:

½ m v² = (1 + ε) E_l
Solve for "m".

http://en.wikipedia.org/wiki/Leonids wrote:
<<The Leonids is a prolific meteor shower associated with the comet Tempel-Tuttle. The Leonids get their name from the location of their radiant in the constellation Leo: the meteors appear to radiate from that point in the sky. Their proper Greek name should be Leontids (Λεοντίδαι, Leontídai), but the word was initially constructed as a Greek/Latin hybrid and it is being used since. They peak in November. Earth moves through the meteoroid stream of particles left from the passages of a comet. The stream comprises solid particles, known as meteoroids, ejected by the comet as its frozen gases evaporate under the heat of the Sun when it is close enough – typically closer than Jupiter's orbit. The Leonids are a fast moving stream which encounter the path of Earth and impact at 72 km/s. An annual Leonid shower may deposit 12 or 13 tons of particles across the entire planet.

Larger Leonids which are about 10 mm across have a mass of half a gram and are known for generating bright (apparent magnitude -1.5) meteors. [A golf ball has a diameter not less than 42 mm and weighs no more than 46 grams].>>

by **BDanielMayfield** » Thu Nov 22, 2012 2:28 pm

This is an awesome capture from an equally awesome video sequence! Today’s apod reminded me of something I wondered about from the “Leonids Over Monument Valley” apod of 2 days ago.

(For the record, just to be totally clear to everyone, I did NOT think that that apod was a fake. But the setting did remind me of the old John Wayne classic western “Stagecoach” which could have included an Indian named Two Birds and a stowaway. Plus, Nuefer’s grav lensing buttes post needed to be rebutted.)

Back to my question: Why is the color of today’s leonid mostly green? I know that the color is a function of the meteor’s temperature, but in today’s example the green extends for an enormous length, whereas in the apod of 2 days ago the green sections were often shorter, with red tinted white from about the center forward. What do these color variations tell us about the meteors that made them?

Bruce

by **orin stepanek** » Thu Nov 22, 2012 2:17 pm

I found Orion in this view; but it is almost lost in the concentration of stars!

by **SteedJoy@gmail.com** » Thu Nov 22, 2012 7:29 am

Great! But the shooting star seems not come out from Leo ...

by **Ron** » Thu Nov 22, 2012 6:49 am

Great photo !

How do we know these are grain of sand size, and not golf ball size or watermelon size. ?
Something that leaves a streak that long is going to burn up a lot more surface than something that only leaves a short trail.??

On another track, do these ever dive straight down into the atmosphere, rather than streak across the sky. Does that produce a different type of track - or photo ?
Just wondering....

by **APOD Robot** » Thu Nov 22, 2012 5:10 am

Night of the Long Leonid

Explanation: A cosmic grain of sand left the long and colorful trail across this all-sky view. Its grazing impact with planet Earth's atmosphere began at 71 kilometers per second. With the Milky Way stretching from horizon to horizon, the scene was captured on the night of November 17 from the astronomically popular high plateau at Champ du Feu in Alsace, France. Of course, the earthgrazer meteor belongs to this month's Leonid meteor shower, produced as our fair planet annually sweeps through dust from the tail of periodic Comet Tempel-Tuttle. The shower's radiant point in the constellation Leo is very close to the eastern horizon, near the start of the trail at the lower left. Bright planet Jupiter is also easy to spot, immersed in a faint band of Zodiacal light just below and right of center. The image is part of a dramatic time-lapse video (vimeo here) that began only 7 minutes before the long leonid crossed the sky.

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The thin blue/green line

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