Scientia potentia est: Solar Probe Plus

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Saturday, January 14, 2017

Total Solar Eclipse 2017: When, Where and How to See It (Safely)

Map showing the path of totality for the Aug. 21, 2017 total solar eclipse. Credit: Fred Espenak/NASA GSFC

On Aug. 21, 2017, American skywatchers will be treated to a rare and spectacular celestial show — the first total solar eclipse visible from the continental United States in nearly four decades.

Next year's "Great American Total Solar Eclipse" will darken skies all the way from Oregon to South Carolina, along a stretch of land about 70 miles (113 kilometers) wide. People who descend upon this "path of totality" for the big event are in for an unforgettable experience, said eclipse expert Jay Pasachoff, an astronomer at Williams College in Massachusetts.

"It's a tremendous opportunity," Pasachoff told Space.com. "It's a chance to see the universe change around you.

A total solar eclipse last darkened soil on the U.S. mainland on Feb. 26, 1979. But August 2017 will mark the first time in 99 years that such an event is "readily available to people from coast to coast," Pasachoff said.

Total Solar Eclipse 2017 Photo: Eclipse2017.org

A rare event

The fact that total solar eclipses occur at all is a quirk of cosmic geometry. The moon orbits an average of 239,000 miles (384,600 kilometers) from Earth — just the right distance to seem the same size in the sky as the much-larger sun

But most solar eclipses are of the partial variety, in which the moon appears to take a bite out of the sun's disk. Indeed, two to five solar eclipses occur every year on average; total eclipses happen just once every 18 months or so. (Eclipses are relatively rare because the moon's orbit is inclined about 5 degrees relative to that of Earth. If the two bodies orbited in exactly the same plane, a solar eclipse would occur every month, during the moon's "new" phase.)

How Solar Eclipses Work: When the moon covers up the sun, skywatchers delight in the opportunity to see a rare spectacle. See how solar eclipses occur in this Space.com infographic. Credit: Karl Tate, SPACE.com Contributor

Furthermore, the narrow path of totality is often inaccessible to skywatchers — most of Earth is covered by water, after all — so a total solar eclipse that occurs over populated areas is quite special. Indeed, the August 2017 event will be the first one whose totality path lies completely within the United States since 1776, experts have said.

That path goes from the Oregon coast through Idaho, Wyoming, Nebraska, Kansas, Missouri, Illinois, Kentucky, Tennessee, Georgia, North Carolina and South Carolina. While just 12 million people or so live within the narrow band, perhaps 220 million reside within a day's drive of it, according to Space.com skywatching columnist Joe Rao. [Incredible Solar Eclipse View Shot During Alaska Airlines Flight (Video)]

Pasachoff advises folks to make that drive when the time comes.

"Though the rest of the continental U.S. will have at least a 55 percent partial eclipse, it won’t ever get dark there, and eye-protection filters would have to be used at all times even to know that the eclipse is happening. The dramatic effects occur only for those in the path of totality," Pasachoff said in a statement.

"If you are in that path of totality, you are seeing the main event, but if you are off to the side — even where the sun is 99 percent covered by the moon — it is like going up to the ticket booth of a baseball or football stadium but not going inside," he added.

Pasachoff himself plans to be there. He has observed 63 solar eclipses to date, and not just for fun: The events provide a rare opportunity to study the sun's wispy outer atmosphere, which is called the corona. (The sun's overwhelming brightness usually drowns out the faint corona.)

Temperatures in the corona top 1.8 million degrees Fahrenheit (1 million degrees Celsius), making the region much hotter than the solar surface, which is just 11,000 degrees F (6,000 degrees C) or so. How the corona gets so hot has puzzled scientists for decades, and Pasachoff and his colleagues aim to gather some useful data during the Great American Eclipse.

"How energy is injected into the corona is one of the things we'll be investigating," Pasachoff told Space.com.

Be safe!

If you do plan to observe the August 2017 eclipse, remember: NEVER look directly at the sun without proper eye protection, except when the solar disk is completely occluded (during the brief period of totality); serious and permanent eye damage can result.

"Proper eye protection" includes specially made solar filters, eclipse glasses or No. 14 welder's glass. You can also observe the eclipse indirectly, by making a pinhole camera or watching shadows cast by trees. (The gaps between leaves act as natural pinholes.)

You should never look directly at the sun, but there are ways to safely observe an eclipse. See how to safely observe a solar eclipse with this Space.com infographic. Credit: Karl Tate, SPACE.com Contributor

To learn more about how to safely observe the sun, check out this Space.com infographic.

Safely See the Sun – Build a Shoebox Pinhole Camera

Finally, if you miss out on the August 2017 event, don't despair — you'll get another chance seven years later. In 2024, a total solar eclipse will darken the skies above Mexico and Texas, up through the Midwest and northeastern U.S

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The above post is reprinted from materials provided by Space. Note: Materials may be edited for content and length.

Saturday, July 23, 2016

Finally Solar Probe Plus (2018) will begin the Journey Into The Sun

Credit: NASA/Johns Hopkins University Applied Physics Laboratory

After 60 years of dreaming of a close-up solar mission, it's quickly approaching time for NASA to realize that goal. Last week, the agency announced that the Solar Probe Plus mission has moved into "advanced development" ahead of a launch in 2018. It's being built by the Johns Hopkins University Applied Physics Laboratory (JHUAPL).

RELATED: Magnetic 'Braids' May Cook the Sun

Solar Probe Plus has an exciting few years ahead of it following the launch, including no less than seven (!) Venus flybys and a daring plunge into the corona, or the outer atmosphere of the sun. Here are some of the science details for you to brush up on:

Key elements of the solar probe plus mission of NASA

1. Staring down the Sun

Where does the sun's energy flow? How is the outer atmosphere heated? These are some of the main questions that NASA's Solar Probe Plus will answer. The microphone drp will happen when the probe gets the chance to fly through the solar corona, something scientists have wanted to do for 60 years but couldn't until the technology caught up. "Solar Probe Plus is a true mission of exploration; for example, the spacecraft will go close enough to the Sun to watch the solar wind speed from subsonic to supersonic, and it will fly ghrough the birthplace of the highest-energy solar particles," JHUAPL wrote on the mission website. "Still, as with any great mission of discovery, Solar Probe Plus is likely to generate more questions than it answers."

2. Seven lucky Venus flybys

It's very common for spacecraft to use gravity assists to reduce their fuel requirements (which saves on launch weight and therefore money). But the tradeoff for Solar Probe Plus will be time as it flies seven times by the planet Venus between 2018 and 2024. It's only after the seventh flyby that Solar Probe Plus will be close enough to the sun to do all of the science that researchers desire. That said, the spacecraft will not be idle during this time. You can bet it will be looking at the star from afar, and that when it flies by Venus at least some science instruments will be turned on to look at the planet. It's like a bonus Venus mission.

3. Braving the sun's fury

Solar Probe Plus will need to withstand a lot of heat when it gets up close to the sun. It's closest approach is expected at 3.7 million miles (5.9 million kilometers), about seven times closer than Mercury ever gets to the sun. This also handily beats the record set by the Helios 2 spacecraft, which really just grazed the inside of Mercury's orbit. It passed about 27 million miles (44 million kilometers) from the sun in Apirl 1976. From both close up and afar, it will look at the solar wind (the stream of particles from the sun). energy transfer through the sun , and something called "dusty plasma" — superheated gas with suspended particles in it — near the sun.

4. Magnetic Madness

The sun has a lot of mysteries surrounding its magnetic field. The main one is why the sun reverses olarity every 11 years in a cycle which sees it go from a weakling with pracically no sunspots, to a monster spewing solar flares, and back to a weakling again before switching polariteis once more.

A bit part of the Solar Probe Plus mission is to probe the magnetic field and other parts of the sun to make better prediction sabout when the next flare will head towrads Earth. Big-enough solar flares can cause damage to satellites and even power lines. This image from the Solar Dynamics Observatory shows just how complicated the magnetic field is. "The complex overlay of lines can teach scientists about the wyas the sun's magnetism changes in response to the constant movemetn on and inside the sun," NASA wrote in March. "Note how the magnetic fields are densest near the bright spots visible on the sun — which are magnetically strong active regions — and many of the field lines link one active region to another."

5. Building for the long haul

If you're going to get close to the sun for long periods of time, you have to make sure your spacecraft can take the heat. Solar Probe Plus will carry a huge shield that is eight fee in diameter and 4.5 inches thick, made up of carbon-carbon carbon foam. Its solar arrays, JHUAPL said, will move around to make sure that the panels maintain the proper heat and power, retracting and extending as required.

Some "heat-resistant technologies," JHUAPL added, came from NASA's MESSENGER spacecraft, a Mercury probe that flew by the planet three times before settling into an orbital mission that ran between 2011 and 2015. For example, the solar shield on Solar Probe Plus is similar toe designs of MESSENGER's sunshade.