Painting the Sky, polar stratospheric clouds photographed by Thomas Kast

Christmas 2020 is past now, but you can still enjoy the astro advent calendar of daily images posted in the Bella Online Astronomy forum. Here we revisit the first twelve days which included a space probe, atmospheric phenomena, skyscapes and deep-space objects. Although there are only a few picture links in this article, there's a link to the forum thread at the end of this article.

1 Thomas Kast was understandably excited to witness a magical display of polar stratospheric clouds in Finland. They're a rare winter phenomenon of high latitudes, breaking up light into colors rather like oil on water. Kast's photo won the Skyscapes category of the Astronomy Photographer of the Year 2020.

2 TWAN (The World at Night) is an international project to encourage astrophotographs set against a variety of earthly landscapes. Jeff Dai observed the Leonid meteor shower of 2011 in southwestern China. Mars shines like a beacon in the dark sky, and just below it is a meteor streak.

3 The dish antennas of the Very Large Array stand proudly in the New Mexico desert under a skyful of stars. The tracks you can see in the picture allow the antennas to be moved into different configurations. Jeff Hellerman photographed the radio telescope at moonset.

4 The Hubble Space Telescope provided this portrait of nearby spiral galaxy NGC 5643 in the constellation Lupus (the Wolf). Blue in the spiral arms dominates the image. The color is from hot young stars, showing the presence of active star formation. A glowing center is due to hot gas falling into a massive black hole.

5 Comet NEOWISE, which got a lot of attention in 2020, was photographed by Constantine Emmanouilidi. He chose the spectacular setting of the Vikos Gorge in northern Greece. [Click on the image to enlarge.] In addition to the comet, there are lots of stars, including a nice view of the Big Dipper.

6 Peter Ward created the winning entry of the Stars and Nebulae category of the Astronomy Photographer of the Year 2020. He photographed the nebula NGC 3576, then use software to remove the stars before mapping the nebula onto a false color palette. This vivid image of stellar creation and destruction evoked the destructive bushfires that had burned millions of acres in Australia in 2019-2020.

7 Asteroids are interesting for what they can tell us about the origins of the Solar System and their potential danger to Earth. The Japan space agency JAXA sent Hayabusa2 (Peregrine Falcon) to the asteroid Ryugu. Having studied the asteroid and taken samples, the craft brought the samples to Earth early in December 2020.

8 Joe Randall didn't capture a turbulent nebula light years away. The nebulous feature he photographed was storm clouds with summer lightning in Colorado, USA. Lightning's electrical discharge is hotter than the Sun and creates a supersonic shockwave – that's what thunder is.

9 The overall winner of the 2020 David Malin Awards for astrophotography, Mark Polsen, named his photo Tranquility Base, though set on Earth, not the Moon. The citation said that it was a “perfect setting, under a beautiful sky with the moon and Venus peeping through the trees.”

10 One name of M2-9 is Wings of a Butterfly Nebula. It's a planetary nebula, a dying sunlike star that's sloughed off its outer envelope. The resulting nebulae come in many shapes and colors. The Hubble Space Telescope image of ethereal M2-9 shows that it's bipolar.

11 The Geminids are a mid-December meteor shower. Patrick Cullis caught on film a Geminid fireball over the Flatirons in Colorado USA. Geminid meteors are of different colors and also known for producing exceptionally bright meteors called fireballs.

12 Caroline Herschel discovered NGC 253 in 1783 in the constellation Sculptor. It was just a fuzzy blob in her telescope, nothing like the lovely little spiral galaxy Terry Robison photographed. The galaxy is currently undergoing intense star formation.

Note: Here is the advent calendar thread.