APOD: Perseid Below (2011 Aug 17)

[biddie67]

In every picture of the moon, the craters are always the dominant feature - I just hadn't ever made the connection that any meteors from the various annual meteor showers could impact the moon - how fascinating!!!!!

Astronaut Garan's great photograph makes me think that some enterprising individual in the future could arrange for meteor shower viewing trips (~or~ maybe even trips to view eclipses) to a new-age orbiting resort-like space station .

[flash]

Perseid Below
Out of the frame, the Sun is on the horizon...
Seen above the meteor near the horizon...

I'm not sure above which altitude it ceases to make sense to use the term "horizon" but instead to use the term "limb", but 380 kilometers seems sufficient. The "horizon" at that altitude is no longer "horizontal" a straight line... it is below, and is circular!

[Matt Ventimiglia]

Can anyone tell me what the thin pale green line above the horizon is in this picture? It looks like a wispy layer of slightly luminous clouds in the upper atmosphere. I've seen this in many images taken from orbit but not sure what causes this phenomenon. Thanks for any info you can share.

Matt Ventimiglia
Museum Guide Griffith at Observatory
Los Angeles

[owlice]

Airglow.

below the curving limb of the Earth and a layer of greenish airglow

[alter-ego]

Can anyone tell me what the thin pale green line above the horizon is in this picture? It looks like a wispy layer of slightly luminous clouds in the upper atmosphere. I've seen this in many images taken from orbit but not sure what causes this phenomenon. Thanks for any info you can share.

Airglow.

below the curving limb of the Earth and a layer of greenish airglow

Also see:
http://asterisk.apod.com/viewtopic.php? ... 25#p153571
and Airglow (Wiki)

This is particularly cool. I haven't seen it before, and it is dated Mar 2009, so here it is (again?):

Click to play embedded YouTube video.

Uploaded by benwl on Mar 2, 2009

Taken from ISS of northern hemisphere night pass showing aurora (red 630nm and green 557nm emissions), atmospheric airglow (scale height of the atmosphere is about 100km in the movie), cities at night, star motion, and lightening. One image taken every 15 seconds and played back at 5 frames per image.

The light emission is caused by trapped electrons and protons from Earth's magnetosphere impacting the upper atmosphere. At 100km altitude, the atmosphere is composed mostly of molecular nitrogen (N-N), molecular oxygen (O-O), and atomic oxygen (O). A life of a hapless electron (or proton) starts at the suns surface, is swept away by the solar wind, happens to get caught in the Earths magnetic dipole, bounces endlessly from North magnetic pole to South magnetic pole for months or years, and then on this evening has enough energy to overcome the retarding magnetic mirroring effect of the dipole field and impact a neutral gas particle in the upper atmosphere, which emits a photon of light that is then detected by Dr. Pettit's camera on the ISS orbiting at ~200km altitude. What a journey!