Keep Looking Up

The Biggest And The Brightest.

Source: SkyView App. I made this on my way to work.

It’s been rainy and overcast for several days now, but over the weekend the clouds finally broke up, the sun came out, and in the mornings Venus has been bright in the southeast. This morning I noticed something almost as bright underneath it: Jupiter. Jupiter is the fourth brightest object in the night sky, after the Sun, Moon, and Venus, which always makes me wonder, why did ancient astronomers call it Jupiter? How did they know it was the biggest planet in the solar system? Venus is brighter, and closer, which makes it appear closer. Jupiter is so large some astronomers think it’s really a failed star–which kind of makes sense since it’s really a big ball of mostly hydrogen and helium, with no solid surface, which seriously undermines the plot of Clifford D. Simak’s Desertion, although it does make sense that the climax of Arthur C. Clarke’s 2010 revolves around Jupiter becoming a second sun in our solar system even though in his novel 2001, unlike the movie, the ill-fated Discovery One heads to Saturn, but that’s another story.
Jupiter spins around the Sun taking almost twelve years at a time to make a full orbit. Ancient Chinese astronomers associated it with prosperity, and Babylonians associated it with their god Marduk who gradually rose to become top of the pantheon.
And it’s got that big swirling red spot, a hurricane so large Earth could fit into it three times, that was definitely first seen in 1831, but may have first been spotted in 1664 and there have been signs it might be clearing up but somehow it just keeps going. Then there are Jupiter’s moons–at least seventy-nine. The four largest, Europa, Ganymede, Io, and Callisto, were first seen by Galileo, who started the tradition of naming them after Jupiter’s lovers, and luckily for astronomers the Roman god, and his Greek counterpart, got around a lot, and more than five hundred years later we’re still learning new things about them. Europa’s ice may hide life, and just last month astronomers got pictures of a volcano erupting on Io, which is the most active moon in the solar system.
Anyway, after a lot of digging I could only figure that it was just dumb luck that the biggest planet in the solar system just happens to be named Jupiter. And in an interesting astronomical coincidence about twelve hours later, hanging in the same part of the sky, was Sirius, the brightest star in the night sky.

Source: SkyView app. I made this one in the backyard in the dark so you can’t see anything except stars, or maybe pixels.

Getting There.

Source: Safely Endangered

Last year I wrote a post about the length of years throughout the solar system, comparing all the planets and Pluto to an Earth year. To recap: it takes Pluto 248 years to orbit the sun, 165 years for Neptune, 84 years for Uranus, a little over 29 years for Saturn, 12 years for Jupiter, 687 days for Mars, 225 days for Venus, and 88 days for Mercury. This year I thought I’d do something a little different, inspired by Voyager 2, which, on December 10, 2018, left the solar system and became the second human-made object to enter interstellar space, following Voyager 1 which crossed over in 2012.
Voyager 2 is currently moving along at more than 34,000 miles per hour, and it took a little more than forty-one years to travel eighteen and a half billion miles. Radio signals from the craft, still being sent, take about sixteen and a half hours to reach Earth. That got me thinking about speed, specifically the speed of light. Voyager 2 isn’t anywhere close to the speed of light, which is 186,000 miles per second, and technically can’t reach that speed since mr = m0 / sqrt (1 – v2 / c2 ), but that’s another story.
Light from the sun, on the other hand, can travel at the speed of light and to put things in perspective here’s how long it takes to reach different markers through the solar system:
It takes light from the sun three minutes to reach Mercury.
It takes light from the sun six minutes to reach Venus.
It takes light from the sun eight minutes to reach Earth.
It takes light from the sun about twelve minutes and forty seconds to reach Mars.
It takes light from the sun about forty-three minutes to reach Jupiter.
It takes light from the sun more than seventy-nine minutes to reach Saturn.
Does sunlight ever reach Uranus? Yes, it does, but it takes sunlight more than two and a half hours–almost 160 minutes–to get to Uranus.
It takes light from the sun more than four hours to reach Neptune.
It takes light from the sun five and a half hours to reach Pluto–just under how long it would take to fly from New York to Los Angeles, minus the time you have to spend in security, which takes about two and a half hours if they have to examine Uranus.
And it takes that same sunlight four and a half years to reach Alpha Centauri, our nearest stellar neighbor. At its current rate Voyager 2 will get there in about eighty-six thousand, two hundred years, minus the time it’ll have to spend going through security.

Alpha and Beta Centauri. Source: Wikipedia

Will we eve get there? Maybe, but the future is very hard to predict.

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