Here are a few stories I didn’t get to tell in 2018. There is a lot to read here so feel free to skip over the parts that don’t interest you.
“Earthrise”
This Christmas Eve we mark the 50th anniversary of one of the most famous photographs ever taken. “Earthrise” is an image of our planet seen from lunar orbit on Dec. 24, 1968. It was not the first image of Earth from the Moon (Lunar Orbiter 1 took that photo in August 1966), but it’s the one that has become part of our collective memory.
The photograph was circulated around the world and helped to inspire the modern environmental movement that had started to coalesce after the publication of “Silent Spring.” This now-familiar view of our world was entirely novel at the time; it is still remarkable today to see our “Spaceship Earth” carrying humanity and all of its works through the heavens. In commemoration here are some interesting resources.
NASA’s official “Earthrise” page:
https://www.nasa.gov/centers/marshall/history/this-week-in-nasa-history-apollo-8-captures-earthrise-dec-24-1968.html
For the 45th anniversary of “Earthrise”, NASA created a simulation of the what the Apollo 8 crew was seeing when the photo was taken:
https://youtu.be/LHbFIieK-uo
This page has additional information about “Earthrise”:
https://petapixel.com/2018/12/20/how-nasas-iconic-earthrise-photo-was-shot/
Finally, PBS will air a special episode of NOVA about Apollo 8 and “Earthrise” on Dec. 26. Please check your local listings for details:
https://www.pbs.org/wgbh/nova/video/apollos-daring-mission/
Venus in the Morning Sky
I have received several emails this season asking about the very bright object in the eastern pre-dawn sky, and most of your guesses are correct, it is our sister planet Venus! Why is it so very bright just now? Well first of all Venus is pretty close to Earth compared to most of the other planets, so that is one reason.
The other reason is that the atmosphere of Venus is very dense and reflects most of the sun’s rays. We call the absolute brightness of an object its albedo, and Venus has an albedo of 0.7, meaning that it reflects about 70% of the sunlight that hits its atmosphere. This albedo is higher than any of the other major planets.
The Venusian atmosphere is so reflective because its clouds are primarily composed of sulfuric acid and other highly reflective compounds. Now you might say, our own Moon has no atmosphere and it’s much brighter than Venus! And this is correct; however, the Moon is brighter because it is much closer to Earth than Venus, so despite its much lower albedo (about 0.1), the Moon is always brighter than any other object in the night sky.
Anyway, please enjoy Venus as the “morning star”. throughout the week. If you thought Venus was something else like an airplane or a UFO, you are not alone. Venus is frequently misidentified, sometimes even by experienced aerial observers (including yours truly!).
Voyager 2
Voyager 2 has officially entered interstellar space as of Nov. 5. The spacecraft was launched 41 years ago and was the first (and so far only) probe to visit the ice giants Uranus and Neptune. Voyager 2 will now travel through the interstellar medium, collecting data as long as its nuclear power source lasts. Eventually, Voyager 2 will pass somewhat near the red dwarf star Ross 248 which is about 10 light-years from Earth. The spacecraft is traveling at a speed of over 38,000 mph and will take about 40,000 years to reach Ross 248, so that gives you some idea of the distance between the stars!
New Horizons
You may want to check in with the New Horizons spacecraft over the New Year’s holiday, it is scheduled to fly by the trans-Neptunian object nicknamed Ultima Thule early in the morning on Jan. 1. You may recall that New Horizons encountered the dwarf planet Pluto back in July 2015. At over 1 billion miles beyond Pluto, Ultima Thule will be the most distant object ever visited by a spacecraft.
What does “Ultima Thule” mean anyway? That sounds like an odd name, but in fact, it has been used since antiquity to refer to someplace very far away, beyond any familiar locations. The term Thule was first used by Pytheas, the famous explorer of the ancient world who was the first known person to travel north of the Arctic Circle.
Happy Holidays and see you in 2019!
Looking-Glass Tea 
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