Starship Asterisk*

Halo from Atacama

Explanation: Influenced by the strong Pacific El Nino, cloudy skies have more often come to Chile's high Atacama Desert this season, despite its reputation as an astronomer's paradise. Located in one of the driest, darkest places on planet Earth, domes of the region's twin 6.5 meter Magellan telescopes of Carnegie Las Campanas Observatory were closed on May 13. Still, a first quarter Moon and bright stars shine through in this panoramic night skyscape, the lunar disk surrounded by a beautiful, bright halo. The angular radius of the halo is 22 degrees. Not determined by the brightness or phase of the Moon itself, the angle is set by the hexagonal geometry of atmospheric ice crystals that reflect and refract the moonlight. On that night, the brilliant star just inside the halo's radius was really planet Jupiter. Flanking the halo to the far left is brightest star Sirius, with Arcturus to the right.

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Like the Swedish meteorologist Nils Holmqvist has said, the sky is prettiest when there are some clouds in it.

Even though it's not the best thing for astronomy.

Nice APOD!

Ann

Let's not overlook the contrail - or, as some incubi would have it, chemtrail - tracing its graceful arch below moon and stars.

Always makes one a bit mournful to see domes shuttered in the night. It is good that the photographer, likely a frustrated observer, was still able to be out looking at the sky and to have shared this luminous image with us.

Thank you.

Actually, the bright star far left of the halo is Canopus. Sirius is lower in the sky and just next to the left hand side Magellan telescope dome.

Even the cloudy Chilean skies are better than most, apparently.

Tunç Tezel

Wow, that correction was made by The Flash, probably. Thanks!

Tunç Tezel

When I saw the teaser yesterday I could have sworn we were going to get an old commercial.
Or a primer on shampooing in space.

canopia wrote:Actually, the bright star far left of the halo is Canopus. Sirius is lower in the sky and just next to the left hand side Magellan telescope dome.

Even the cloudy Chilean skies are better than most, apparently.

Tunç Tezel

Interesting. The bright star at far left struck me as being quite blue. And that might indeed apply to Canopus, because even though Canopus in an F-type star (F0Ib) it is strikingly blue for its spectral class, only about +0.16 (although measurements vary). That is bluer than A7V-type star Altair, about +0.22.

Ann

Couldn't Jupiter sometimes appear to display a separate, dimmer halo? Maybe that would be too dim to visualize when the moon appears in close proximity to Jupiter. Has a Jovian halo ever been photographed under darker conditions when the moon isn't visible?

cytophile wrote:Couldn't Jupiter sometimes appear to display a separate, dimmer halo? Maybe that would be too dim to visualize when the moon appears in close proximity to Jupiter. Has a Jovian halo ever been photographed under darker conditions when the moon isn't visible?

Jupiter, along with every star in the sky, will have a halo when the conditions are right for halos. But they are far too dim to see, even under the darkest sky. Venus or Jupiter might produce a bright enough halo to capture photographically with a long exposure (like an hour). Not sure about that, not sure if anyone has tried.