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It’s Cassini’s Final Month.

Cassini is completing its 13-year tour of Saturn with dives between the planet and its rings. Credit: NASA/JPL

Yes, it’s true. As of today, August 15, NASA’s Cassini spacecraft has less than 31 days—one full month—left in operation and, sadly, its existence. On September 15, 2017, Cassini will end its mission with a controlled dive into Saturn’s atmosphere…a journey that it will not long survive. But up until the very end Cassini, which has been exploring the majestic ringed planet and its family of moons since it arrived in the summer of 2004, will be making scientific observations and sending the data back to us here on Earth—at least as long as it possibly can. That data, in fact, will still be en route across the 900 million miles of space between us and Saturn for almost an hour after the spacecraft will have succumbed to the forces of atmospheric entry.

When Cassini’s final signal is received on Earth it will be a ghost message, sent from a ship that no longer exists.

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Answers to 8 Questions About the August 2017 Solar Eclipse

It’s August and one of the most highly-anticipated astronomical events of the 21st century is nearly upon us: the August 21 solar eclipse, which will be visible as a total eclipse literally across the entire United States…but that doesn’t mean everywhere in the United States. Totality will pass across the U.S. in a narrow band about 60 miles wide starting along the northern coast of Oregon at 10:18 a.m. local time (PDT) and ending along the coast of South Carolina at 2:48 p.m. EDT. But that’s just totality—the full eclipse event will actually begin much earlier than that and end later, and its visibility won’t be limited to only that path. And while it’ll be happening overhead in the daytime sky you’ll need the right equipment to view it safely, whether you’re in totality or not.

Wait, you say, what’s the difference between totality and…not totality? And how is it caused? And why is this a big deal at all? If you’re wondering those things (and perhaps others) then this post is just for you. Below are answers to some common—and certainly not dumb—questions about the solar eclipse, brought to you by yours truly (with a little help from NASA and other eclipse specialists.)

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NASA Gets WISE to Long-Period Comets

Infrared data from WISE was used to identify the clouds of vaporized material around comets’ nuclei and then estimate their sizes. (NASA/JPL-Caltech)

Comets are the icy remnants left over from the formation of the Solar System. They circle the Sun in highly elliptical orbits that can range in length from several years to several million years, depending on their origin, and while they are usually quiet and dark when they get close enough to the Sun they are briefly heated enough to melt—technically sublimate—some of their frozen material, forming a cloud of gas and dust and a long tail sometimes big and bright enough to be visible from Earth.

But for the majority of their travels most comets are dark and difficult to spot, especially those originating from the Oort Cloud, an enormous spherical zone of icy debris surrounding our Solar System 186 billion miles away. Now, using infrared data from NASA’s WISE spacecraft, researchers have concluded that there are many more so-called “long period” comets visiting from the Oort Cloud than previously suspected—at least seven times more—and that they’re larger than we thought, too…many over half a mile across.

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Have No Fear, Phobos is Here!

Mars and Phobos imaged by Hubble on may 12, 2016. Credits: NASA, ESA, and Z. Levay (STScI), Acknowledgment: J. Bell (ASU) and M. Wolff (Space Science Institute).

On May 12, 2016, the Hubble Space Telescope captured a series of images of Mars and in them the planet’s moon Phobos can be seen appearing from behind the western limb. This was just 10 days before opposition which, in 2016, was the closest Mars had been to Earth since 2005, lending particularly good opportunity for picking out its largest—yet still quite small—moon.

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This Day in Space History: One Small Step

Note: This is an updated article from 2012.

Panorama of the Eagle lunar module by Ed Hengeveld from JSC scans.

“That’s one small step for a man… one giant leap for mankind.”

I’m not sure what else need be said about the significance of what happened on this day in 1969, 48 years ago… it was a shining moment in human history, and will be — should be — remembered forever as an example of what people can achieve when challenged, driven, and inspired.

More giant leaps have been made since then, and undoubtedly more will be made in the future, but this was the first and to this date still very much the biggest.
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