Astro Advent 2018 - Days 13-24

Astro Advent 2018 - Days 13-24
Aurorae, moon visitors, stars, planets, and more are in the astro countdown to Christmas. Here are the days from mid-Advent to Christmas Eve.

Only a few of the days have picture links, but you can follow the entire advent calendar thread on the Forum.

13 Beautiful dramatic scene in Kvaløya, near Tromsø, Norway when a Geminid fireball streaks through an auroral sky. Bjørnar G. Hansen's photo was taken during the Geminid peak on December 13, 2009.

14 December 14, 2013. China's Chang'e-3 mission landed on the Moon in the Sinus Iridum region. It was the first unmanned soft landing on the Moon since the Soviet Luna 24 sample return vehicle in 1976. The Chinese mission consisted of a lander and the rover Yutu (Jade Rabbit). Yutu was the pet of the Moon goddess Chang'e.

15 Skyscape taken off the Skeleton Coast of Namibia. The Moon, low in the sky as it's setting, is reddened, while brilliant Venus looks like a full Moon. It's so bright that its light is even reflected in the water. And one more treat: above and to the right of Venus is Jupiter. [Photo: Vikas Chander]

16 Comet 46P/Wirtanen – nicknamed the “Green Christmas Comet” – made its closest approach to Earth on December 16. It's a small short-period comet that visits every 5.4 years, but this was its closest visit for decades. It was the original target for the Rosetta mission.

17 NASA's Kepler Space Observatory revolutionized our view of exoplanets. When it became crippled, a daring innovation gave it a new mission. It all ended in October when Kepler ran out of fuel. One discovery was the Kepler-22 system. The star is similar to our Sun and there are planets in his habitable zone.

18 "Two worlds, one Sun” The worlds are Earth and Mars. On Earth, our atmosphere scatters the blue of the Sun's light more than the red. So the sky directly overhead is blue, but when sunlight travels the long path along the horizon, it's mostly the red light that's left. Mars has very little atmosphere, but what it has is dusty. At sunset on Mars, sunlight is traveling through more fine dust particles. These particles scatter the red light more than the blue.

19 In the the tomb of Rameses VI (1151-1143 BCE) in the Valley of the Kings in Egypt, the ceiling depicts Nut, the sky goddess. Her elongated body is shown at night and in daytime, as she regulates the light and the dark. By day, we see the solar disk as red. The solar god sails in his barge along Nut's body until evening. Then Nut swallows the Sun, taking it safely through the hours of night. At dawn it appears anew as a winged scarab.

20 From me to you, here are Hubble greetings from the Veil Nebula. Located in the constellation Cygnus the Swan, it's 110 light-years across, and a supernova remnant. That's what remains of a massive star that ran out of fuel and exploded – the blast wave is still expanding. [The Hubble site has a selection of winter greetings.

21 In the northern hemisphere, the summer solstice sunrise is to the northeast. Sunrises then move gradually southwards, so that autumn equinox sunrise is due east, and after that they move gradually to the southeast. The most southerly sunrise occurs at the winter solstice. In the composite photo by astrophotographer Anthony Ayiomamitis, you can see sunrise in a Greek village at three different times of year.

22 Two special events put on a show together on July 27th this year, with a total lunar eclipse and Mars at opposition. (1) The lunar eclipse is the longest one of the 21st century. Totality lasted 1 hr 43 min, four minutes shorter than the theoretical limit of a lunar eclipse. (2) Mars was at opposition – that's when it's at its closest to Earth. [Photo: lunar eclipse, Mars, and the Mole Antonelliana in Turin, Italy – photographed by Stefano De Rosa]

23 Katherine Coleman Goble Johnson celebrated her 100th birthday this year on August 26th. An African-American mathematician who worked for NASA and its predecessor for 35 years, she made calculations for US manned spaceflights. Starting with Alan Shepard's suborbital flight, Johnson worked through to the beginning of the Space Shuttle program before her retirement. In 2015 President Obama awarded her the Presidential Medal of Freedom.

24 Fifty years ago, on Christmas Eve 1968, three men broadcast their seasonal good wishes to planet Earth from the Moon. Frank Borman, Jim Lovell, and Bill Anders were farther from home than any human being before them. Unexpectedly, they saw Earth rising above the Moon, and the photo they took remains one of the most memorable images of the Space Age.

On the 50th anniversary of Apollo 8, Bill Anders reflects

The Earth we saw rising over the battered grey lunar surface was small and delicate, a magnificent spot of color in the vast blackness of space. Borders that once rendered division vanished. All of humanity appeared joined together on this glorious-but-fragile sphere.

The most significant revelation of Apollo 8's journey extends far beyond our scientific-and-technological achievements, beyond our "records" and "firsts."

We set out to explore the moon and instead discovered the Earth.

You Should Also Read:
Geminids - a December Spectacle
Christmas in the Skies
Astro Advent - Days 1-12

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