Astro Advent 2020 - Days 13-24

Astro Advent 2020 - Days 13-24
Earth-grazing Meteor Procession by Frederic Church, 19th century American landscape painter.

Meteors, colorful moons, an alien landscape and more – they're in the 2020 astro countdown to Christmas on the Bellaonline Astronomy Forum. Here are some notes about the final twelve days plus a Christmas bonus. 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.

13 The star trails in long-exposure photos aren't made by stars moving, but by the Earth rotating. In the northern hemisphere they're concentric circles (or arcs) centered on Polaris, the North Star. Robert Oliver chose a monumental setting for his star trails, the Giant's Causeway in Northern Ireland. It consists of thousands of interlocking basalt columns, most of them hexagonal. An ancient massive volcanic eruption created it.

14 In the Catskill Mountains of New York in 1860, Frederic Church painted the breathtaking string of fireball meteors shown in the header image. A meteor procession is a very rare sight. It happens when a meteor breaks up as it enters the atmosphere, creating multiple meteors in nearly identical paths.

15 What color is the Moon? Marcella Giulia Pace has photographed the Moon in numerous colors, including shades of blue, pink, orange and even a pale green. The colors we see are effects in our atmosphere such as air pollution and volcanic eruptions. In space, you'd see that the Moon is pretty much shades of grey.

16 The Pleiades, a star cluster in the constellation Taurus, is commonly known as the Seven Sisters. They're named for the daughters of the titan Atlas and oceanid Pleione of Greek mythology. The cluster actually has hundreds of stars, but only a handful are visible to the unaided eye. Some people can see all seven sisters, but others see only six.

17 Somak Raychaudhury's solar eclipse photo, taken in Pune, India, is an unusual one. Look at the ground in the bamboo grove. The small gaps between the bamboo leaves act like pinholes to let sunlight through. Each little gap projects an image of the eclipsing Sun. The eclipse was an annular one where the Moon doesn't completely hide the Sun's disk. If Pune had been on the path of totality, the images would have been a multitude of bright rings.

18 Kelvin Hennessey photographed the Byron Bay Lighthouse at Cape Byron in northern New South Wales, Australia. Is it photoshopped? No it's not photoshopped, yet this isn't what you'd see at the lighthouse. Hennessy was some distance away and used a long lens to get this startling effect.

19 Sci fi fans have a special treat in Marcin Zajac's photo. The Milky Way dominates a fabulous sky over a landscape that looks like an alien planet. However, the strange rock formations are known as hoodoos and they're in the Ah-Shi-Sle-Pah Wilderness in New Mexico.

20 Northern Lights are eerie, but are one of nature's most exquisite sights. They're created when atomic particles from the Sun are funnelled into our atmosphere at the poles. Particles of the upper atmosphere glow like a fluorescent lamp when the solar particles collide with them. Andreas Ettl captured the Northern Lights and the lights of the Norwegian fishing village of Hamnøy.

21 At the winter solstice in the northern hemisphere, the North Pole is tilted its farthest away from the Sun, making it the shortest day. An ancient tomb in Ireland is aligned with the solstice Sun and shines down a long tunnel on this day – if, of course, the Sun is actually shining.

22 Atop the Cerro Paranal mountain are the four telescopes that make up the VLT Survey Telescope – each one has a mirror that's over eight meters wide. High in the Andes, in the clear dark sky, you can see the road which is the only access to the observatory. In Yuri Beletsky's picture it “resembles a river of light flowing through the dry otherwordly landscape.”

23 The Sun rises in the east, but only at the equinoxes does it rise due east. Zaid M. Al-Abbadi took photos to show the sunrise direction for each month of 2019. At the northern winter solstice the sun rises in the southeast.

24 For Christmas Eve, there was a splendid selection of heavenly images from the Chandra X-ray telescope site. The images are composites, using data from Chandra and other telescopes.

25 A Christmas day bonus was an image that included the Cone Nebula which is shaped like a stylized Christmas tree. The stars around it are called the Christmas Tree Cluster.

Note: Here is the advent calendar forum thread.

You Should Also Read:
Astro Advent 2020 - Days 1-12
Why Planets Have Seasons
Meteor or Meteorite and Other Posers

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