Solar Probe Plus: We're Going to Dive 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).

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:

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.

Originally published on Discovery News.

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How Fast Is Earth Moving? — **A new time-lapse videos combines 3,000 images from the DSCOVR satellite's EPIC camera to show a year of Earth's rotation, as seen from a million miles away.**
**Credit: NASA Goddard via YouTube**

As an Earthling, it's easy to believe that we're standing still. After all, we don't feel any movement in our surroundings. But when you look at the sky, you can see evidence that we are moving.

Some of the earliest astronomers proposed that we live in a geocentric universe, which means that Earth is at the center of everything. They said the sun rotated around us, which caused sunrises and sunsets — same for the movements of the moon and the planets. But there were certain things that didn't work with this vision. Sometimes, a planet would back up in the sky before resuming its forward motion.

We know now that this motion — which is called retrograde motion — happens when Earth is "catching up" with another planet in its orbit. For example, Mars orbits farther from the sun than Earth. At one point in the respective orbits of Earth and Mars, we catch up to the Red Planet and pass it by. As we pass by it, the planet moves backward in the sky. Then it moves forward again after we have passed.

Another piece of evidence for the sun-centered solar system comes from looking at parallax, or apparent change in the position of the stars with respect to each other. For a simple example of parallax, hold up your index finger in front of your face at arm's length. Look at it with your left eye only, closing your right eye. Then close your right eye, and look at the finger with your left. The finger's apparent position changes. That's because your left and right eyes are looking at the finger with slightly different angles.

The same thing happens on Earth when we look at stars. It takes about 365 days for us to orbit the sun. If we look at a close-up star in the summer, and look at it again in the winter, its apparent position in the sky changes because we are at different points in our orbit. We see the star from different vantage points. With a bit of simple calculation, using parallax we can also figure out the distance to that star.

How Fast Are You Moving Through The Universe?

https://youtu.be/F77MBqpkul8

The Universe: OUR PLACE IN THE MILKY WAY Blu-Ray (Full Documentary Films) 1080p

https://youtu.be/6xsDLHOfCOQ

How fast are we spinning?

Earth's spin is constant, but the speed depends on what latitude you are located at. Here's an example. The circumference (distance around the largest part of the Earth) is roughly 24,898 miles (40,070 kilometers),according to NASA. (This area is also called the equator.) If you estimate that a day is 24 hours long, you divide the circumference by the length of the day. This produces a speed at the equator of about 1,037 mph (1,670 km/h).

You won't be moving quite as fast at other latitudes, however. If we move halfway up the globe to 45 degrees in latitude (either north or south), you calculate the speed by using the cosine (a trigonometric function) of the latitude. A good scientific calculator should have a cosine function available if you don't know how to calculate it. The cosine of 45 is 0.707, so the spin speed at 45 degrees is roughly 0.707 x 1037 = 733 mph (1,180 km/h). That speed decreases more as you go farther north or south. By the time you get to the North or South Poles, your spin is very slow indeed — it takes an entire day to spin in place.

Space agencies love to take advantage of Earth's spin. If they're sending humans to the International Space Station, for example, the preferred location to do so is close to the equator. That's why space shuttle missions used to launch from Florida. By doing so and launching in the same direction as Earth's spin, rockets get a speed boost to help them fly into space.

How fast does Earth orbit the sun?

Earth's spin, of course, is not the only motion we have in space. Our orbital speed around the sun is about 67,000 mph (107,000 km/h),according to Cornell. You can calculate that with basic geometry.

First, we have to figure out how far Earth travels. Earth takes about 365 days to orbit the sun. The orbit is an ellipse, but to make the math simpler, let's say it's a circle. So, Earth's orbit is the circumference of a circle. The distance from Earth to the sun — called an astronomical unit— is 92,955,807 miles (149,597,870 kilometers), according to the International Astronomers Union. That is the radius (r). The circumference of a circle is equal to 2 x π x r. So in one year, Earth travels about 584 million miles (940 million km).

Since speed is equal to the distance traveled over the time taken, Earth's speed is calculated by dividing 584 million miles (940 million km) by 365.25 days and dividing that result by 24 hours to get miles per hour or km per hour. So, Earth travels about 1.6 million miles (2.6 million km) a day, or 66,627 mph (107,226 km/h).

Sun and galaxy move, too

To blow your mind even more: the sun has an orbit of its own in the Milky Way. The sun is about 25,000 light-years from the center of the galaxy, and the Milky Way is thought to be about 100,000 light-years across. We are thought to be about halfway out from the center, according to Stanford University. The sun and the solar system appear to be moving at 200 kilometers per second, or at an average speed of 515,000 mph (828,000 km/h). Even at this rapid speed, the solar system would take about 230 million years to travel all the way around the Milky Way.

The Milky Way, too, moves in space relative to other galaxies. In about 4 billion years, the Milky Way will collide with its nearest neighbor, theAndromeda Galaxy. The two are rushing toward each other at about 70 miles per second (112 km per second).

Everything in the universe is, therefore, in motion.

What would happen if Earth stopped spinning?

There is no chance that you'll be flung off to space right now, because the Earth's gravity is so strong compared to its spinning motion. (This latter motion is called centripetal acceleration.) At its strongest point, which is at the equator, centripetal acceleration only counteracts Earth's gravity by about 0.3 percent. In other words, you don't even notice it, although you will weigh slightly less at the equator than at the poles.

NASA says the probability for Earth stopping its spin is "practically zero" for the next few billion years, so you can feel safe in knowing you'll stay in place. Theoretically, however, if the Earth did stop moving suddenly, there would be an awful effect. The atmosphere would still be moving at the original speed of the Earth's rotation. This means that everything would be swept off of land, including people, buildings and even trees, topsoil and rocks, NASA added.

What if the process was more gradual? This is the more likely scenario over billions of years, NASA said, because the sun and the moon are tugging on Earth's spin. That would give plenty of time for humans, animals and plants to get used to the change. By the laws of physics, the slowest the Earth could slow its spin would be 1 rotation every 365 days. That situation is called "sun synchronous" and would force one side of our planet to always face the sun, and the other side to permanently face away. By comparison: Earth's moon is already in an Earth-synchronous rotation where one side of the moon always faces us, and the other side opposite to us.

But back to the no-spin scenario for a second: There would be some other weird effects if the Earth stopped spinning completely, NASA said. For one, the magnetic field would presumably disappear because it is thought to be generated in part by a spin. We'd lose our colorful auroras, and the Van Allen radiation belts surrounding Earth would probably disappear, too. Then Earth would be naked against the fury of the sun. Every time it sent a coronal mass ejection (charged particles) toward Earth, it would hit the surface and bathe everything in radiation. "This is a significant biohazard," NASA said.

Another weird effect: most spots on Earth would have daylight for half a year, and nighttime for the other half. During the day, the surface temperature would change depending on what latitude you're at. The equator would be even hotter than it is now, because the sun's light rays shine directly on it; the poles would not have as pronounced an effect because the rays are slanted. Because there are no more sunrises and sunsets, the sun would just move up and down in the sky during the year according to the Earth's orbit and tilt.

"This long-term temperature gradient would alter the atmospheric wind circulation pattern so that the air would move from the equator to the poles rather than in wind systems parallel to the equator like they are now," NASA added.

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