Starship Asterisk*

Meteors Over Quebec

Explanation: Meteors streaked through the sky above many of Earth's cities last week, but nobody was hurt, and no damage has been reported. The assault from space appeared to originate from someplace in the constellation of Perseus, and included millions of small projectiles hurtling toward Earth at over 200,000 kilometers per hour. Pictured above, people gathered at ASTROLab du Mont-Megantic in southern Quebec, Canada gazed helplessly toward the sky last Thursday night as they themselves were unable to stop the meteor onslaught. Fortunately, Earth's defense, consisting of a planet-wise blanket of air over 100-kilometers thick, obliterated the attacking projectiles by using friction generated by their own speed to heat them into disintegration. The large triangle in the foreground, although impressive in appearance, was not part of the Earth's meteor defense system. The space attack was expected as part of the annual Perseids meteor shower as the Earth passed through sand-sized debris left over from the sun-orbiting Comet Swift-Tuttle.

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Hahahaha best "Explanation" ever!

I'm not a professional astronomer nor a physicist, but I've learned that the meteors burn when they enter the atmosphere not because of the friction produced by the air, but because of the Ram pressure they produce when they travel inside our protective layer...

Here's my source... hope it helps
http://www.space.com/scienceastronomy/t ... 903-4.html

Do those meteors speak French or English?

http://www.youtube.com/watch?v=jr-EiUSUnhw

I think you mean "planet-wide" and not "planet-wise".

Concerning the Perseids, I read somewhere that meteors glow not because of friction but because of the compression of air in front of them as they hit the atmosphere. True or false?

Brian B.

From the picture and description I expected Gil Gerard and [yum] Erin Grey to be standing outside in their Spandex suits getting reading to climb into their Starfighters to help blow up the asteroids.

Great Writing!! Keep it up.

I love how this was written <3

BrianBoru wrote:Concerning the Perseids, I read somewhere that meteors glow not because of friction but because of the compression of air in front of them as they hit the atmosphere. True or false?

It has to do with the size of the meteoroid, and the height in the atmosphere. For bodies larger than about a centimeter, the primary mechanism is compression of air in front of it. When the body gets smaller than that, its size in comparison to the distance between individual gas molecules is such that ram pressure becomes insignificant. In that case, the mechanism is direct collisions with gas molecules- still not exactly friction, although there is a similarity, and this is often referred to as gas friction.

Spikejp wrote:I'm not a professional astronomer nor a physicist, but I've learned that the meteors burn when they enter the atmosphere not because of the friction produced by the air, but because of the Ram pressure they produce when they travel inside our protective layer...

That's half true. Ram pressure is only significant when a meteoroid is large- a centimeter or more. For smaller bodies (such as most Perseids) the distance between the gas molecules in the upper atmosphere is so large that there is little compression in front of the meteoroid. In this case, the heating mechanism is more complicated, involving direct collisions. This is sometimes referred to as "friction", but it really isn't, and that is a word best avoided in any description of meteor dynamics.

In my zeal to write up this image, I strangely didn't notice in the accompanying email that the image was captured during LAST YEAR'S Perseids. Oops. Thanks (again) to Owlice for pointing this out. So I have now corrected this, as usual trying to change as few words as possible, and also fixed "planet-wide." I apologize for the oversights. - RJN

I enjoyed viewing today APOD of Meteors over Quebec. There is a growing number of composite images like this, also in TWAN group and we only use them when there is a strong educational purpose and with specified information about their multi-exposure digitally composite nature and how long it took to collect all these meteors. Otherwise many people who see these images think the shower was so strong to capture all these meteors in a single short exposure. Without that information (which is missing in today APOD) there is no difference between a normal Perseid shower of ZHR ~100 with photos like this http://antwrp.gsfc.nasa.gov/apod/ap021105.html
taken at meteor storms with ZHRs of several thousands.

There is a fairly high level of photoshop in making these composite landscape shots, as you need to stack meteors from different shots while the landscape and the sky do not align. So cut and paste and erasing the rest is necessary. It just too much Photoshop for my personal taste. While in deep sky photography such deep processing is very common, in landscape shots where you generally try to show what was viewed by naked-eye its a bit uncommon to me. However they are absolutely not fake images as those meteors have actually crossed that part of the sky, but they were not all captured in short span of time as they seems to be with a foreground of fixed people.

We usually use such composite on TWAN collection when the radiant is visible and can have more educational depth or when they are all-sky views like this http://www.twanight.org/newTWAN/photos.asp?ID=3002285 and have good local information on density of the appeared meteors across the sky and ratio of brighter meteor to fainter ones.

Babak Tafreshi
Director
The World at Night
http://www.twanight.org

Has anyone ever calculated the amount of mass the earth gains from meteors in a year?

aerwalt wrote:Has anyone ever calculated the amount of mass the earth gains from meteors in a year?

It is hard to calculate. Estimates based on radar studies put it at a few million kilograms per year. A few studies have put it as much as ten times higher, but I think the general opinion leans towards the smaller number.

(These meteor questions are probably best asked in the general questions about astronomy section. AFAIK Dr Bonnell isn't a meteoriticist.)

Nice work Mr.Remi Boucher.