Solar Probe - Blog Posts

Spilling the Sun’s Secrets

You might think you know the Sun: It looks quiet and unchanging. But the Sun has secrets that scientists have been trying to figure out for decades.  

One of our new missions — Parker Solar Probe — is aiming to spill the Sun’s secrets and shed new light on our neighbor in the sky.

Even though it’s 93 million miles away, the Sun is our nearest and best laboratory for understanding the inner workings of stars everywhere. We’ve been spying on the Sun with a fleet of satellites for decades, but we’ve never gotten a close-up of our nearest star.

This summer, Parker Solar Probe is launching into an orbit that will take it far closer to the Sun than any instrument has ever gone. It will fly close enough to touch the Sun, sweeping through the outer atmosphere — the corona — 4 million miles above the surface.

This unique viewpoint will do a lot more than provide gossip on the Sun. Scientists will take measurements to help us understand the Sun’s secrets — including those that can affect Earth.

Parker Solar Probe is equipped with four suites of instruments that will take detailed measurements from within the Sun's corona, all protected by a special heat shield to keep them safe and cool in the Sun's ferocious heat.

The corona itself is home to one of the Sun’s biggest secrets: The corona's mysteriously high temperatures. The corona, a region of the Sun’s outer atmosphere, is hundreds of times hotter than the surface below. That's counterintuitive, like if you got warmer the farther you walked from a campfire, but scientists don’t yet know why that's the case.

Some think the excess heat is delivered by electromagnetic waves called Alfvén waves moving outwards from the Sun’s surface. Others think it might be due to nanoflares — bomb-like explosions that occur on the Sun’s surface, similar to the flares we can see with telescopes from Earth, but smaller and much more frequent. Either way, Parker Solar Probe's measurements direct from this region itself should help us pin down what's really going on.

We also want to find out what exactly accelerates the solar wind — the Sun's constant outpouring of material that rushes out at a million miles per hour and fills the Solar System far past the orbit of Pluto. The solar wind can cause space weather when it reaches Earth — triggering things like the aurora, satellite problems, and even, in rare cases, power outages.

We know where the solar wind comes from, and that it gains its speed somewhere in the corona, but the exact mechanism of that acceleration is a mystery. By sampling particles directly at the scene of the crime, scientists hope Parker Solar Probe can help crack this case.

Parker Solar Probe should also help us uncover the secrets of some of the fastest particles from the Sun. Solar energetic particles can reach speeds of more than 50% the speed of light, and they can interfere with satellites with little warning because of how fast they move. We don't know how they get so fast — but it's another mystery that should be solved with Parker Solar Probe on the case.  

Parker Solar Probe launches summer 2018 on a seven-year mission to touch the Sun. Keep up with the latest on the Sun at @NASASun on Twitter, and follow along with Parker Solar Probe's last steps to launch at nasa.gov/solarprobe.

Make sure to follow us on Tumblr for your regular dose of space: http://nasa.tumblr.com.

Why Won’t Our Parker Solar Probe Melt?

This summer, our Parker Solar Probe will launch to travel closer to the Sun than any mission before it, right into the Sun’s outer atmosphere, the corona.

The environment in the corona is unimaginably hot: The spacecraft will travel through material with temperatures greater than 3 million degrees Fahrenheit. 

So…why won’t it melt? 

The Difference Between Heat and Temperature

Parker Solar Probe was designed from the ground up to keep its instruments safe and cool, but the nature of the corona itself also helps. The key lies in the difference between heat and temperature.

Temperature measures how fast particles are moving, while heat is the total amount of energy that they transfer. The corona is an incredibly thin and tenuous part of the Sun, and there are very few particles there to transfer energy – so while the particles are moving fast (high temperature), they don't actually transfer much energy to the spacecraft (low heat).

It's like the difference between putting your hand in a hot oven versus putting it in a pot of boiling water (don’t try this at home!). In the air of the oven, your hand doesn't get nearly as hot as it would in the much denser water of the boiling pot. 

So even though Parker Solar Probe travels through a region with temperatures of several million degrees, the surface of its heat shield will reach only about 2,500 F.

The Heat Shield

Of course, thousands of degrees Fahrenheit is still way too hot for scientific instruments. (For comparison, lava from volcano eruptions can be anywhere between 1,300 to 2,200 F.) 

To withstand that heat, Parker Solar Probe is outfitted with a cutting-edge heat shield, called the Thermal Protection System. This heat shield is made of a carbon composite foam sandwiched between two carbon plates. The Sun-facing side is covered with a specially-developed white ceramic coating, applied as a plasma spray, to reflect as much heat as possible.

The heat shield is so good at its job that even though the Sun-facing side of the shield will be at 2,500 F, the instruments in its shadow will remain at a balmy 85 F.

Parker Solar Probe Keeps its Cool

Several other designs on the spacecraft help Parker Solar Probe beat the heat. 

Parker Solar Probe is not only studying the Sun – it's also powered by it. But even though most of the surface area of its solar arrays can be retracted behind the heat shield, even that small exposed segment would quickly make them overheat while at the Sun.  

To keep things cool, Parker Solar Probe circulates a single gallon of water through its solar arrays. The water absorbs heat as it passes behind the arrays, then radiates that heat out into space as it flows into the spacecraft's radiator. 

It's also important for Parker Solar Probe to be able to think on its feet, since it takes about eight minutes for information to travel between Earth and the Sun. If we had to control the spacecraft from Earth, by the time we knew something went wrong, it would be too late to fix it. 

So Parker Solar Probe is smart: Along the edges of the heat shield's shadow are seven sensors. If any of these sensors detect sunlight, they alert the central computer and the spacecraft can correct its position to keep the sensors – and the rest of the instruments – safely protected behind the heat shield.

Over the course of its seven-year mission, Parker Solar Probe will make 24 orbits of our star. On each close approach to the Sun, it will sample the solar wind, study the Sun’s corona, and provide unprecedentedly close up observations from around our star – and armed with its slew of innovative technologies, we know it will keep its cool the whole time. 

Parker Solar Probe launches summer 2018 on its mission to study the Sun. Keep up with the latest on the mission at nasa.gov/solarprobe or follow us on Twitter and Facebook.

Make sure to follow us on Tumblr for your regular dose of space: http://nasa.tumblr.com

Our Sun is More than Meets the Eye

The Sun may look unchanging to us here on Earth, but that’s not the whole story.

In visible light – the light our eyes can see – the Sun looks like an almost featureless orange disk, peppered with the occasional sunspot. (Important note: Never look at the Sun directly, and always use a proper filter for solar viewing – or tune in to our near-real time satellite feeds!)

But in other kinds of light, it’s a different picture. The Sun emits light across the electromagnetic spectrum, including the relatively narrow range of light we can see, as well as wavelengths that are invisible to our eyes. Different wavelengths convey information about different components of the Sun’s surface and atmosphere, so watching the Sun in multiple types of light helps us paint a fuller picture.

Watching the Sun in these wavelengths reveals how active it truly is. This image, captured in a wavelength of extreme ultraviolet light at 131 Angstroms, shows a solar flare. Solar flares are intense bursts of light radiation caused by magnetic events on the Sun, and often associated with sunspots. The light radiation from solar flares can disturb part of Earth’s atmosphere where radio signals travel, causing short-lived problems with communications systems and GPS.

Looking at the Sun in extreme ultraviolet light also reveals structures like coronal loops (magnetic loops traced out by charged particles spinning along magnetic field lines)…

…solar prominence eruptions…

…and coronal holes (magnetically open areas on the Sun from which solar wind rushes out into space).

Though extreme ultraviolet light shows the Sun's true colors, specialized instruments let us see some of the Sun's most significant activity in visible light.

A coronagraph is a camera that uses a solid disk to block out the Sun’s bright face, revealing the much fainter corona, a dynamic part of the Sun’s atmosphere. Coronagraphs also reveal coronal mass ejections, or CMEs, which are explosions of billions of tons of solar material into space. Because this material is magnetized, it can interact with Earth’s magnetic field and trigger space weather effects like the aurora, satellite problems, and even – in extreme cases – power outages.

The Sun is also prone to bursts of energetic particles. These particles are blocked by Earth’s magnetic field and atmosphere, but they could pose a threat to astronauts traveling in deep space, and they can interfere with our satellites. This clip shows an eruption of energetic particles impacting a Sun-observing satellite, creating the 'snow' in the image.

We keep watch on the Sun 24/7 with a fleet of satellites to monitor and better understand this activity. And this summer, we’re going one step closer with the launch of Parker Solar Probe, a mission to touch the Sun. Parker Solar Probe will get far closer to the Sun than any other spacecraft has ever gone – into the corona, within 4 million miles of the surface – and will send back unprecedented direct measurements from the regions thought to drive much of the Sun’s activity. More information about the fundamental processes there can help round out and improve models to predict the space weather that the Sun sends our way.

Keep up with the latest on the Sun at @NASASun on Twitter, and follow along with Parker Solar Probe’s last steps to launch at nasa.gov/solarprobe.

Make sure to follow us on Tumblr for your regular dose of space: http://nasa.tumblr.com.