APOD: Aurora Over Greenland (2011 Aug 23)

APOD Robot · Post by **APOD Robot** » Tue Aug 23, 2011 4:06 am

Aurora Over Greenland

Explanation: This aurora arched from horizon to horizon. During the current Shelios expedition to observe and learn about the northern lights, the sky last weekend did not disappoint. After sunset and some careful photographic planning, the above image was taken from the expedition's Qaleraliq campsite in southern Greenland. Visible straight through the center of the aurora, found with a careful eye, is the Big Dipper and the surrounding constellation of the Big Bear (Ursa Major). The brightest orb on the far right is the Moon, while Jupiter can be seen even further to the right. The Shelios expedition is scheduled to last until the end of August and include live broadcasts of ongoing auroras.

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Beyond · Post by **Beyond** » Tue Aug 23, 2011 5:52 am

Well... I found that i don't have a 'careful' eye, as i couldn't pick out the Big Dipper in the center of the Aurora. But that's ok, because green-green is green they say, on the top side of the world. Da-da-da, da-da--da-da, green-green is green they say, where the Aurora's are greener still.

Ann · Post by **Ann** » Tue Aug 23, 2011 6:32 am

Nice green aurora. It's a shade of green which isn't yet yellow-green, but is clearly approaching yellow-green. This is what I think of as the color of 560 nm, bearing in mind that 580 nm is brilliantly yellow. Okay, so maybe this aurora is 555 nm, then!

Anyway, it's a suitably colored aurora over a landmass called Greenland. The dominant color of Greenland is white from snow and ice (even though the ice appears to be melting here - a victim of climate change?), but there are plenty of aurorae to be seen from there!

As for the Big Dipper, it can be seen sitting inside the topmost part of the green arc of the aurora. Please note the Alpha Persei cluster away from the aurora at top right. This cluster is very obvious. And to the left of the bright Moon you can see the moonlight-polluted Pleaides!

Ann

Green Bean · Post by **Green Bean** » Tue Aug 23, 2011 7:08 am

.

I have a slight preference for the 510 to 515 nm part of the spectrum.

.

canopia · Post by **canopia** » Tue Aug 23, 2011 10:55 am

The green of Aurora is too much saturated, guessing the wavelength of the light accordingly may not deliver a correct result. The saturation seems to be resulting from picture processing, not from the recording of the images.

Ann wrote:Nice green aurora. It's a shade of green which isn't yet yellow-green, but is clearly approaching yellow-green. This is what I think of as the color of 560 nm, bearing in mind that 580 nm is brilliantly yellow. Okay, so maybe this aurora is 555 nm, then!

Anyway, it is a suitable colored aurora over a landmass called Greenland. The dominant color of Greenland is white from snow and ice (even though the ice appears to be melting here - a victim of climate change?), but there are plenty of aurorae to be seen from there!

As for the Big Dipper, it can be seen sitting inside the topmost part of the green arc of the aurora. Please note the Alpha Persei cluster away from the aurora at top right. This cluster is very obvious. And to the left of the bright Moon you can see the moonlight-polluted Pleaides!

Ann

orin stepanek · Post by **orin stepanek** » Tue Aug 23, 2011 11:46 am

It's a beautiful picture!

The big dipper is visible; but if I didn't know it was there I probably wouldn't have found it.

kaigun · Post by **kaigun** » Tue Aug 23, 2011 2:37 pm

The ice is melting because it's the middle of August. It happens every year. Speaking of which, this seems like a strange time of the year to do research on the auroras. I guess the location is more hospitable in the summer but at the high latitudes there is still a lot of daylight.

wasinger · Post by **wasinger** » Tue Aug 23, 2011 2:38 pm

It looks like Prestone antifeeze!

Emily Windsor-Cragg · Post by **Emily Windsor-Cragg** » Tue Aug 23, 2011 4:19 pm

What's this HUNK of photoshop job in the middle of the photo? Makes is unacceptable as an Album addition.

That while, textured bird-shaped thingie is not part of the photo; somebody was trying to hide something under it.

What a shame.

BMAONE23 · Post by **BMAONE23** » Tue Aug 23, 2011 4:57 pm

In addition to the Big Dipper in the middle of the Aurora, There is also the Pleiades with the large "V" shape of Taurus below, near the moon

Ann · Post by **Ann** » Tue Aug 23, 2011 5:14 pm

As for the color of the aurora, check out what this page says about it:

Atomic oxygen is responsible for the two main colors of green (wavelength of 557.7 nm) and red (630.0 nm).

Check out this page, too. Here you can see a number of coffee mugs whose color is defined in nanometers!

If you are unlucky, you may get the captions in Swedish, but you should have no trouble figuring out what wavelength goes with which coffee mug. I have to admit that the 540 nm coffee mug does look more like today's aurora than the 560 nm coffee mug. Oh well.

Personally I find the 460 nm coffee mug and the 480 nm coffe mug the best-looking ones, although I may have found a 475 nm coffee mug absolutely, absolutely perfect.

Oh, well. What's a royal BLUE? After all, I suppose it would be frightfully dull, and-and-and boring, and-and completely... Completely wonderful.

Ann

canopia · Post by **canopia** » Tue Aug 23, 2011 5:26 pm

That big white thing was actually there. By guess is, that relative darkness outlying that chunk of ice is because of "Unsharp Mask" filter applied in Adobe Photoshop. Less image processing would have delivered a better result.

Emily Windsor-Cragg wrote:What's this HUNK of photoshop job in the middle of the photo? Makes is unacceptable as an Album addition.

That while, textured bird-shaped thingie is not part of the photo; somebody was trying to hide something under it.

What a shame.

Beyond · Post by **Beyond** » Tue Aug 23, 2011 7:18 pm

Ann, i got the swedish version. Those are really neat coffee cup pictures

, I've never seen those kind of interactive pictures before. If the cups were filled with steaming hot coffee, i wonder if it would cause any noticeable change in the colors?

Malcolm · Post by **Malcolm** » Tue Aug 23, 2011 10:15 pm

M34 in Perseus, top middle right, is visible just above and to the right of Algol.
Not quite so prominent is M13 in Hercules top far left.
And, it may be my imagination, but there is a faint dot where M3 should be to the left of Canes Ventici, low middle left, just a wee bit above the right hand slope of the hill on the left.
Other constellations clearly visible are Corona Borealis just above the the aurora to the left of the lefthand hill with Bootes embedded in the glow above the lefthand hill. Auriga is above the righthand end of the aurora. Triangulum is above and a bit to the right of the moon with Aries below half way to Jupiter. To the right of Aries the far right clear area is occupied by Pisces.

What a superb panorama it is !

Malcolm.

saturn2 · Post by **saturn2** » Tue Aug 23, 2011 11:51 pm

This image of auroras is very beautiful.
The auroras are the product of sun eyection.
The sun radiation and Earth atmosphere made the auroras.

NoelC · Post by **NoelC** » Wed Aug 24, 2011 12:32 am

I guess I am free-associating... I saw the melting ice in the image and my thoughts went like this...

"Now they debate whether global warming is real - will one day they debate whether there was liquid water on Earth?"

It is a COOL image, regardless! Well done.

-Noel

neufer · Post by **neufer** » Wed Aug 24, 2011 1:52 am

kaigun wrote:
The ice is melting because it's the middle of August. It happens every year. Speaking of which, this seems like a strange time of the year to do research on the auroras. I guess the location is more hospitable in the summer but at the high latitudes there is still a lot of daylight.

http://en.wikipedia.org/wiki/Aurora_%28astronomy%29 wrote:
<<Geomagnetic storms that ignite auroras actually happen more often during the months around the equinoxes. The auroras that resulted from the "great geomagnetic storm" on both 28 August and 2 September 1859 are thought the most spectacular in recent recorded history.

Within the auroral zone the likelihood of an aurora occurring depends mostly on the slant of interplanetary magnetic field (IMF) lines (the slant is known as B_z), being greater with southward slants. During spring and autumn, the interplanetary magnetic field and that of Earth link up. At the magnetopause, Earth's magnetic field points north. When B_z becomes large and negative (i.e., the IMF tilts south), it can partially cancel Earth's magnetic field at the point of contact. South-pointing B_z's open a door through which energy from the solar wind can reach Earth's inner magnetosphere. The peaking of B_z during this time is a result of geometry. The IMF comes from the Sun and is carried outward with the solar wind. The rotation of the Sun causes the IMF to have a spiral shape. The southward (and northward) excursions of B_z are greatest during April and October, when Earth's magnetic dipole axis is most closely aligned with the Parker spiral.

However, B_z is not the only influence on geomagnetic activity. The Sun's rotation axis is tilted 8 degrees with respect to the plane of Earth's orbit. The solar wind blows more rapidly from the Sun's poles than from its equator, thus the average speed of particles buffeting Earth's magnetosphere waxes and wanes every six months. The solar wind speed is greatest – by about 50 km/s, on average – around 5 September and 5 March when Earth lies at its highest heliographic latitude.

Still, neither B_z nor the solar wind can fully explain the seasonal behavior of geomagnetic storms. Those factors together contribute only about one-third of the observed semiannual variations.>>

Ann · Post by **Ann** » Wed Aug 24, 2011 5:12 am

Malcolm wrote:M34 in Perseus, top middle right, is visible just above and to the right of Algol.
Not quite so prominent is M13 in Hercules top far left.
And, it may be my imagination, but there is a faint dot where M3 should be to the left of Canes Ventici, low middle left, just a wee bit above the right hand slope of the hill on the left.
Other constellations clearly visible are Corona Borealis just above the the aurora to the left of the lefthand hill with Bootes embedded in the glow above the lefthand hill. Auriga is above the righthand end of the aurora. Triangulum is above and a bit to the right of the moon with Aries below half way to Jupiter. To the right of Aries the far right clear area is occupied by Pisces.

What a superb panorama it is !

Malcolm.

Thanks for identifying all this, Malcolm!

M34 is indeed prominent once you find it, and M13 is obvious too. But I couldn't find M3, because I wasn't able to make the starscape and my software look the same in that part of the sky.

Ann

Malcolm · Post by **Malcolm** » Wed Aug 24, 2011 10:18 am

Hi Ann, glad you liked it

.
Yes I too had a bit of a struggle with my software, Stellarium, very good but it insisted on doing clever science stuff

by rotating things round the pole instead of what I wanted round my viewpoint !!
Here is a crop of the maybeM3 region with my overlay :

: Click to view full size image

If anyone is interested in an overlay for the whole panorama, which I am still working on, I can put it up later.

Malcolm.

Ann · Post by **Ann** » Wed Aug 24, 2011 4:25 pm

Thanks, Malcolm! I think you may be right. That could well be M3.

Ann

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