Yesterday was the winter solstice, meaning the sun concluded its six-month southward course and seemed to “stand still” before beginning its journey north. Of course, this being a heliocentric neighborhood, the tilt, orbit, and rotation of Earth are what really move the sun through the sky. But don’t let that stop you from appreciating colorful crayon diagrams of the ancient “two-sphere” model of the heavens with Dr. Free-Ride on Adventure in Ethics and Science. If that’s not a useful enough approximation, you can get a modern understanding of solstices and seasonal dynamics from Anne Jefferson on Highly Allochthonous. Also on Highly Allochthonous, Chris Rowan reveals a snapshot of Saturn’s mysterious moon Titan, whose northern hemisphere is just emerging from a fifteen year winter. With middling gravity, apparent lakes and plenty of atmosphere, Titan presents a compelling prospect for extraterrestrial life, although it only receives a fraction of the sunlight we enjoy here on Earth. Finally, visit Ethan Siegel on Starts With A Bang! for a satellite view of the recent snowfall that blanketed the northeastern United States.
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Continue reading “Round and Round”
On Aardvarchaeology, Martin Rundkvist tells us that the Geminid meteor shower is peaking tonight, so if you’ve got any wishes on the back burner, now’s your chance to make them. Of course these shooting “stars” are really bits of extinct comet 3200 Phaethon’s “sandy exhaust trail” burning up in the atmosphere—if you prefer some main sequence hydrogen-fusing affairs, head over to Greg Laden’s Blog to learn about Alcor and Mizar. This binary star system in the constellation Ursa Major has been known since antiquity, but—surprise!—Mizar is actually four stars, and Alcor is now known to be two, meaning that there are a total of six stars linked together in an “orgy of gravitational interaction.” If that’s still not big enough for you, revisit the galactic potpourri of Hubble’s Ultra Deep Field on Starts With A Bang!, where Ethan Siegel explains the optical implications of imaging from infrared wavelengths. And in another post, Siegel recommends we get our hands dirty at Galaxy Zoo, a website where anyone can help astronomers classify galactic collisions by matching up real images from a telescope to computer simulations.
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Continue reading “Star Light, Star Bright…”