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Look Up! A "Ring of Fire" Eclipse Blazes the Southern Hemisphere

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An annular solar eclipse on May 20, 2012 as seen from Chaco Culture National Historical Park in Nageezi, Arizona. Image credit: Stan Honda/AFP/Getty Images

If you're in the Southern Hemisphere, look up tomorrow morning, February 26, and brace yourself. You are going to see the Sun, big and bright as usual—that is, until it turns into a ball of black surrounded by a ring of fire. It’s the sort of sight that begs for two question marks: What is going on up there?? The answer is an annular eclipse. Like its more famous cousin, the total solar eclipse, an annular eclipse involves the moon crossing in front of the Sun. When we’re talking about eclipses, however, not all moons are created equal.

For an eclipse to be “total,” the Sun must be completely obscured by the Moon, leaving only the Sun’s corona shimmering around a black disc. When this happens, the darkest part of the moon’s shadow—the umbra—is cast across the Earth. When viewing this from the zone of totality, where alignment is perfect, day will turn to night (and look around: animals will behave accordingly).

Because the Moon’s orbit is not a perfect circle, it sometimes appears smaller in the sky than at other times. If this “smaller” moon crosses in front of the Sun, you get an annular eclipse. A tremendous black disc will still appear within the Sun but will not obscure our star completely. Rather than witnessing the spectacular view of the Sun’s corona, you’ll see the spectacular view of a fiery sky circle. Day will not turn to night when this happens. Earth at that moment will be in the Moon’s antumbra—that is, a weaker shadow beyond the tip of the umbra.

A swath of South America and Africa—mainly in the southern parts of the continents—will experience this particular eclipse. It will begin on February 26, 2017 at 7:10 a.m. ET, and reach its maximum at 9:58 a.m. NASA Goddard Space Flight Center has a map of the eclipse’s path here. Don’t live in the Southern Hemisphere? Don’t feel left out! On August 24, 2017, a small path across the United States—Oregon to South Carolina—will experience a total solar eclipse.

LOOK UP—BUT ONLY WITH SAFE EYEWEAR

Another view of the annular eclipse on May 20, 2012 as captured by the joint JAXA/NASA Hinode mission. Image credit: JAXA/NASA/Hinode via Flickr // CC BY 2.0

 
It’s interesting to consider that every day, a giant ball of fire hangs in the sky and we can never really get a good look at it without going blind. If you’re interested in seeing the eclipse tomorrow in person, you’re going to have to go toe-to-toe with a spherical celestial fusion reactor. Your eyes are no match for this, which means you will need special glasses.

DO NOT WEAR REGULAR SUNGLASSES. Stare at the Sun wearing nothing but Ray-Bans and the only good news will be that you can wear them indoors forever thereafter, because you will be blind. The tinted windows in your car, the x-ray film your friend at the hospital swears will work—none of these things will protect you from a lifetime of charred and lifeless retinas. There are no half measures where the Sun is concerned.

There are four things you can wear to look at an eclipse: welder’s goggles with a 14+ rating; special eclipse glasses; a “pinhole projector”; and a specially filtered telescope. Welding goggles can be found at industrial equipment stores, but be sure to get the correct shade—not just any goggles will do, and there is a good chance you are wrong. Eclipse glasses are available at specialty shops, though you'll need to beware of fakes. If you’re a teacher, you can make the eclipse a class event by allowing your students to make pinhole projectors themselves. It requires nothing more than a cardboard box, paper, and aluminum foil.

If all of this sounds like a bit much, or if it’s a cloudy day where you are, you have options! Our friends at Slooh will be covering it, broadcasting footage of the eclipse with commentary from astronomers and solar scientists. Coverage begins on February 26 at 7:00 a.m. ET.

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Warby Parker
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Space
Warby Parker Is Giving Away Free Eclipse Glasses in August
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Warby Parker

When this year’s rare “all-American” total solar eclipse comes around on August 21, you’ll want to be prepared. Whether you’re chasing the eclipse to Kentucky or viewing it from your backyard, you’ll need a way to watch it safely. That means an eclipse filter over your telescope, or specially designed eclipse glasses.

For the latter, you can just show up at your nearest Warby Parker, and their eye experts will hand over a pair of eclipse glasses. The stores are giving out the free eye protectors throughout August. The company’s Nashville store is also having an eclipse party to view the celestial event on the day-of.

Get your glasses early, because you don’t want to miss out on this eclipse, which will cross the continental U.S. from Oregon to South Carolina. There are only so many total solar eclipses you’ll get to see in your lifetime, after all.

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NASA // Public Domain
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Space
On This Day in 1962, NASA Launched and Destroyed Mariner 1
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NASA // Public Domain

On July 22, 1962, NASA launched the Mariner 1 probe, which was intended to fly by Venus and collect data on its temperature and atmosphere. It was intended to be the first interplanetary craft—the first time humans had sent a space probe to another world. Unfortunately, NASA aborted the mission 293 seconds after launch, destroying the probe in the Atlantic. What happened?

First off, a bit of history. Mariner 1 was based on the pre-existing Block 1 craft used in the Ranger program, which was aimed at gathering data on our moon. Those early Ranger probes didn't do so well—both Ranger 1 and Ranger 2 suffered early failures in orbit. Mariner 1 was a modified version of the Ranger design, intended for a much longer mission to another planet. It lacked a camera, but had various radiometers, a cosmic dust detector, and a plasma spectrometer—it would be capable of gathering data about Venus, but not pictures per se.

The two previous Ranger missions had used basically the same launch system, so it was reasonably well-tested. The Ranger probes had made it into orbit, but had been unable to stabilize themselves after that.

Mariner 1 launched on the evening of July 22, 1963. Its Atlas-Agena rocket was aided by two radar systems, designed to track data on velocity (the "Rate System") and distance/angle (the "Track System") and send it to ground-based computers. By combining that data, the computers at Cape Canaveral helped the rocket maintain a trajectory that, when separated, would lead Mariner 1 to Venus.

Part of the problem involved in handling two separate radars was that there was a slight delay—43 milliseconds—between the two radars' data reports. That wasn't a problem by itself. The Cape computer simply had to correct for that difference. But in that correction process, a problem was hiding—a problem that hadn't appeared in either of the previous Ranger launches.

To correct the timing of the data from the Rate System—the radar responsible for measuring velocity of the rocket—the ground computer ran data through a formula. Unfortunately, when that formula had been input into the computer, a crucial element called an overbar was omitted. The overbar indicated that several values in the formula belonged together; leaving it out meant that a slightly different calculation would be made. But that wasn't a problem by itself.

The fate of Mariner 1 was sealed when the Rate System hardware failed on launch. This should not have been a fatal blow, as the Track System was still working, and Ground Control should have been able to compensate. But because that overbar was missing, calculations on the incoming radar data went wonky. The computer incorrectly began compensating for normal movement of the spacecraft, using slightly incorrect math. The craft was moving as normal, but the formula for analyzing that data had a typo—so it began telling Mariner 1 to adjust its trajectory. It was fixing a problem that didn't exist, all because a few symbols in a formula weren't grouped together properly.

Mariner 1's rocket did as it was told, altering its trajectory based on faulty computer instructions. Looking on in horror, the Range Safety Officer at the Cape saw that the Atlas rocket was now headed for a crash-landing, potentially either in shipping lanes or inhabited areas of Earth. It was 293 seconds after launch, and the rocket was about to separate from the probe.

With just 6 seconds remaining before the Mariner 1 probe was scheduled to separate (and ground control would be lost), that officer made the right call—he sent the destruct command, ditching Mariner I in an unpopulated area of the Atlantic.

The incident was one of many early space launch failures, but what made it so notable was the frenzy of reporting about it, mostly centered on what writer Arthur C. Clarke called "the most expensive hyphen in history." The New York Times incorrectly reported that the overbar was a "hyphen" (a reasonable mistake, given that they are both printed horizontal lines) but correctly reported that this programming error, when coupled with the hardware failure of the Rate System, caused the failure. The bug was identified and fixed rapidly, though the failed launch cost $18,500,000 in 1962 dollars—north of $150 million today.

Fortunately for NASA, Mariner 2 was waiting in the wings. An identical craft, it launched just five weeks later on August 27, 1962. And, without the bug and the radar hardware failure, it worked as planned, reaching Venus and becoming the first interplanetary spacecraft in history. It returned valuable data about the temperature and atmosphere of Venus, as well as recording solar wind and interplanetary dust data along the way. There would be 10 Mariner missions in all [PDF], with Mariner 1, 3, and 8 suffering losses during launch.

For further reading, consult this Ars Technica discussion, which includes valuable quotes from Paul E. Ceruzzi's book Beyond The Limits—Flight Enters the Computer Age.

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