This is from a post I originally published in 2010. I’ll keep trotting it out until it’s not cool anymore. (Which I don’t think will ever happen.)
On February 14, 1990, after nearly 13 years of traveling the solar system, the Voyager 1 spacecraft passed the orbit of Pluto and turned its camera around to take a series of photos of the planets. The image above shows those photos, isolated from the original series and are left to right, top to bottom: Venus, Earth, Jupiter, Saturn, Uranus, and Neptune.
From that distance, over 4 billion miles from the Sun, the planets each appear as little more than a bright dot against the vastness of interplanetary space. And Voyager was still a long ways off from reaching the “edge” of our solar system, the bubble of energy emitted by the Sun in which all of the planets, moons, and asteroids reside. In fact, Voyager 1 still has an expected five years to go before it crosses that boundary and truly enters interstellar space.*
“That’s here. That’s home. That’s us. On it everyone you love, everyone you know, everyone you ever heard of, every human being who ever was, lived out their lives. … There is perhaps no better demonstration of the folly of human conceits than this distant image of our tiny world.”
– Carl Sagan
404 years ago tonight, January 7, 1610, the Pisan astronomer Galileo Galilei looked up at a bright Jupiter at opposition through his handmade telescope and saw three little “stars” next to it, which piqued his natural scientific curiosity. He soon realized that these little objects weren’t stars at all but rather moons that orbited the giant planet (and not the Earth). Further observations over the next nights showed that the planet wasn’t moving relative to the little “stars” as it should if they were indeed background stars, and in fact the smaller bodies (of which he soon saw four) were moving along with Jupiter, each in its own little orbit. This revelation helped change our entire view of the solar system, causing no end of trouble for Galileo (as the Church didn’t appreciate a restructuring of their conveniently Earth-centered Universe) but also opening the door for the discovery of many more moons around other planets.
Jupiter is now known to have at least 50 moons, with possibly as many as 67.
As a result of his research and publications regarding the (actual) motions of bodies in the solar system, Galileo was eventually sentenced as a heretic by the Inquisition in Rome and spent the last 9 years of his life under house arrest. Still, his legacy of observation and science over dogma and established belief lives on to this day… in fact, if you go outside on a clear night now you can see a brightly shining Jupiter in the eastern sky, just as Galileo did 404 years ago. Take even a small telescope or pair of binoculars and you will easily see its four largest moons as pinpoints of light beside it. Thanks to Galileo and others like him, we now know what those are, and that there are countless other worlds and moons out there like them, just waiting for discovery.
*E pur si muove – “and yet it moves” is a quote often attributed to Galileo, in that he muttered it as he “recanted” and accepted his punishment by the Roman court. But it is likely purely apocryphal, as there is no mention of it in records from the time.
What a year for space exploration! With 2013 coming to a close I thought I would look back on some of the biggest news in space that I’ve featured here on Lights in the Dark. Rather than a “top ten” list, as is common with these year-end reviews, I’m going to do more of a month-by-month (hence the 12) to help recollect some of the amazing stories and sights that 2013 has brought us. And with some of the big headliners we’ve seen this year it’s easy to lose sight of the smaller (but no less fascinating) discoveries — so I’ll be sure to include some of those too. After all, when it comes to learning about the Universe there’s no “little” news!
Ready? Let’s go!
“Attempt no landings there?” Ok, FINE. We’ll just fly a spacecraft through Europa’s newly-discovered plumes and get a taste of its underground ocean that way!
Because it has them, and so we could.
This was the big news from NASA, ESA, and Hubble researchers today: Jupiter’s ice-covered moon Europa (yes, the one from 2010) has Enceladus-like plumes of water vapor near its south pole. What’s more, these plumes appear to vary depending on the moon’s distance from Jupiter; the giant planet’s gravity is “squeezing” Europa, causing the plumes to shut off when it’s closer and turn on when farther away. Now I’m no scientist, but I’d call that pretty solid evidence for a subsurface ocean… and darn good reason to scramble some exploration missions out to Europa tout de suite!
If this doesn’t tug at your heart’s space strings, I don’t know what will.
What we’re seeing here is a video made from images captured by NASA’s Juno spacecraft as it flew past Earth on October 9, 2013. This is the first time a video has been made of the Moon orbiting our planet from beyond the Earth-Moon system*, and, in effect, it’s what a future human space traveler would see as they return home.
Last Wednesday, Oct. 9, 2013, NASA’s Juno spacecraft made a slingshot pass of Earth in order to get the necessary speed boost to reach Jupiter in 2016. As it came within 347 miles of our planet’s surface, passing closest over the southern Atlantic at 3:21 p.m. EDT, it used its JunoCam (developed by the San Diego-based Malin Space Science Systems) to take images along the way. This is one of them, and it gives us a spacecraft’s-eye-view of the Atlantic and the eastern coast of Argentina.
Acquired in March 2007, this eerie image from Hubble’s Advanced Camera for Surveys’s ultraviolet camera show glowing auroral emissions, always present in Jupiter’s polar regions.
The aurora is hundreds of kilometers wide and about 250 kilometers above the planet. It is caused by electrically charged particles striking atoms in the upper atmosphere from above, the same process involved in Earth’s aurorae (except that Jupiter’s magnetic field is orders of magnitude more powerful than Earth’s!)