Iridium Flare My A$$

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With all the solar flare activity lately, we’ve been treated to some very nice Aurora Borealis. Photographers have been going crazy taking some very nice photos, however in northern Norway this was photographed (see the image in the circle below). On Jan. 20, 2010, Per-Arne Mikalsen was photographing a vast aurora erupting over the northern Norwegian town of Andenes.

Latest information released would indicate that this is your typical Iridium satellite flare.

The structured shape of the phenomenon, plus its distance from any light sources, seems to indicate that this isn’t an equipment problem. There is also no known aurora that could do this naturally. So that leaves the “reflection from space” argument. What do we have in space that could possibly reflect the green light being emitted by the aurora?

“I agree with Pål Brekke [Senior Advisor at the Norwegian Space Centre] that a reflection from a satellite is a candidate,” said Hansen. “It reminds of the so-called ‘Iridium flares’ — reflections of sunlight from the regularly shaped Iridium satellites.”

Satellite flares are well known by astronomers. As a satellite passes overhead, the conditions may be right for the spacecraft’s solar panels or antennae to reflect sunlight down to the ground. The result is a short-lived burst of light, known as a “flare.”

The network of Iridium communication satellites are best known for their flares, since they have three huge door-sized antennae that act as orbital mirrors. Witnessing an Iridium flare is immensely rewarding; the event can be predicted beforehand because these satellites have orbits that can be tracked.

My personal concern about the satellite flare theory is the question about auroral light intensity. Is the light from a large aurora bright enough to bounce off a satellite and appear as an auroral satellite flare as a point? And in turn produce a parachute-shaped, lens flare-like projection in the photo? I couldn’t imagine even an Iridium satellite amplifying auroral light that much (although astonking-huge orbital solar power array of the future might do a better job).

“The intensity of an intense aurora is not far from the intensity of moonlight, which is 1/100,000 of sun’s light, and the solar Iridium flares apparently are several orders of magnitude stronger than this ‘auroral flare,’ so the intensity does not immediately exclude the satellite reflection hypothesis,” said Hansen.

A weak auroral flare seems feasible, but as pointed out by astronomer Daniel Fischer via Twitter, the green flare might not have anything to do with reflected aurora light, it could just be the color of the lens coating. The lens flare was therefore the result of internal reflections inside the camera lens caused by the bright lights in the lower left-hand corner of the frame.

“It has the typical caustic shape and it is opposite several bright point lights,” Fischer observed. “Green color could be caused by lens coatings.”

Although more research will need to be done, it certainly seems plausible that Per-Arne Mikalsen serendipitously took a photograph of a satellite flare (possibly an Iridium satellite). The image below is of a known Iridium flare.

What makes this revelation even more exciting is that we’ve never seen an auroral reflection from a satellite before (if it’s not a lens flare, that is).

“I have, by the way, never seen or heard of a similar phenomenon,” Hansen said.

I don’t think the object photographed in the Aurora is an Iridium flare! Do you?