Voyage to the Sun

About 150 million kilometers (93 million miles) from Earth is a blazing ball of superhot gases. It’s the sun—the star at the center of our solar system. Because the sun is so bright and hot, it’s challenging to study it up close. But NASA’s Parker Solar Probe was designed to do just that—by getting closer to the sun than any spacecraft has before.

In 2018, NASA launched the Parker probe into orbit around the sun. Since then, the spacecraft has circled closer and closer to the star. Starting in 2021, the probe’s flybys have taken it through the star’s corona—the outermost layer of its atmosphere. That’s made the spacecraft the first human-made object to ever touch the sun! On December 24, 2024, the probe will make its closest pass yet, flying at a distance just 6.9 million km (4.3 million mi) from the center of the sun.

Scientists hope the probe will help them understand more about the energy the sun gives off and how it affects us on Earth. “We see the sun every day, yet there is still so much to learn about it,” says Nour Rawafi, an astrophysicist at Johns Hopkins Applied Physics Lab in Maryland and the lead scientist for the Parker mission.

A blazing ball of superhot gases is about 150 million kilometers (93 million miles) from Earth. It’s the sun, the star at the center of our solar system. It’s hard to study the sun up close, because it’s so bright and hot. But NASA’s Parker Solar Probe is doing just that. It was designed to get closer to the sun than any spacecraft has before.

In 2018, NASA launched the Parker probe into orbit around the sun. The spacecraft has been circling closer and closer to the star. Starting in 2021, the probe has flown through the star’s corona. That’s the outermost layer of its atmosphere. That made the spacecraft the first human-made object to touch the sun! On December 24, 2024, the probe will make its closest pass yet. It will fly just 6.9 million km (4.3 million mi) from the sun’s center.

Scientists hope the probe will help them understand more about the sun’s energy and its effects on Earth. “We see the sun every day, yet there is still so much to learn about it,” says Nour Rawafi. He’s an astrophysicist at Johns Hopkins Applied Physics Lab in Maryland. He’s also the lead scientist for the Parker mission.

At the sun’s core, or center, pressure is so extreme that hydrogen (H) atoms are squeezed together to form heavier atoms of helium (He). This process, called nuclear fusion, releases a large amount of energy, heating the sun’s core to a scorching 15 million°C (27 million°F)!

The sun gets cooler toward its surface—though it’s still extremely hot. But then, strangely, temperatures shoot up again within the sun’s corona. It’s like walking away from a fire but feeling the temperature get hotter instead of cooler farther from the flames.

This phenomenon has long baffled scientists. Eugene Parker, for whom the Parker probe is named, theorized that small explosions in the sun’s atmosphere, called nanoflares, may be responsible for the corona’s hotter temperatures. The Parker spacecraft could help solve this longtime mystery.

Pressure is extreme at the sun’s core, or center. Hydrogen (H) atoms are squeezed together to form heavier atoms of helium (He). This process is called nuclear fusion, and it releases a large amount of energy. It heats the sun’s core to a blazing 15 million°C (27 million°F)!

The sun gets cooler toward its surface, but it’s still extremely hot. Then temperatures shoot up again within the sun’s corona. That seems strange. It’s like walking away from a fire, but the temperature gets hotter instead of cooler farther from the flames.

This unusual feature has long puzzled scientists. A physicist named Eugene Parker thought that nanoflares may cause the corona’s hotter temperatures. These are small explosions in the sun’s atmosphere. The Parker probe is named after him, and it could help solve this mystery.

The Parker probe’s instruments were built to sample solar particles, examine activity on the sun, and measure the star’s magnetic field. This field causes the sun’s surface to constantly swirl, sending out flares of light and explosions of energy into space. Scientists believe studying this powerful field is the key to understanding solar storms.

To operate, the spacecraft’s equipment had to be able to withstand the intense temperatures near the sun. So Rawafi’s team designed a heat shield to protect the probe. The 2.4 meter (8 foot)-wide barrier is made of a lightweight carbon (C) foam between panels of a carbon-based material. The front of the shield can tolerate temperatures of about 1,000°C (1,800°F). But behind the shield, the probe remains a comfortable 29°C (85°F).

So far, the shield has done its job. The spacecraft has been successfully gathering data and sending it back to Earth. But its biggest test will come later this month when the probe makes its closest approach to the sun—seven times closer to the star than any previous spacecraft.

The Parker probe’s instruments were built for several purposes. They can sample solar particles, examine activity on the sun, and measure the star’s magnetic field. This field causes the sun’s surface to constantly swirl. As a result, flares of light and explosions of energy shoot out into space. Scientists hope to learn more about this powerful field. They believe it’s the key to understanding solar storms.

To work, the spacecraft’s equipment has to withstand the intense temperatures near the sun. So Rawafi’s team designed a heat shield to protect the probe. The barrier is 2.4 meters (8 feet) wide. It’s made of a lightweight carbon (C) foam between panels of a carbon-based material. The front of the shield can handle temperatures of about 1,000°C (1,800°F). But behind the shield, the probe stays at 29°C (85°F).

So far, the shield has done its job. The spacecraft is successfully gathering data and sending it back to Earth. But its biggest test will come later this month. Then the probe will make its closest approach to the sun. It will fly seven times closer than any spacecraft before it.

During its closest flyby, the probe will be moving at 693,000 kph (430,000 mph). That’s fast enough to travel from California to Washington, D.C., in about 20 seconds! No human-made object has ever reached such intense speeds before.

Each time the probe approaches the sun, the solar wind disrupts communications with scientists for several days. So during its closest pass, “we’ll have to wait for the spacecraft to emerge from the other side of the star before we know how it does,” says Rawafi. The data collected on this and the spacecraft’s previous trips past the sun will be analyzed by scientists for years to come.

Information gathered by the Parker probe has already changed our understanding of the sun and its impact on our planet. The mission could also provide insight into the inner workings of the trillions of other stars scattered throughout space. “The sun is the closest star to us,” says Rawafi. “We can study it in more detail than any other star in the universe. This mission is an experience of a lifetime.”

During its closest pass, the probe will move at 693,000 kph (430,000 mph). That’s fast enough to travel from California to Washington, D.C., in about 20 seconds! No human-made object has ever reached such intense speeds.

When the probe approaches the sun, the solar wind disrupts communications with scientists. Each time, this lasts for several days. So during its closest pass, “we’ll have to wait for the spacecraft to emerge from the other side of the star before we know how it does,” says Rawafi. Scientists will examine the data from this and the spacecraft’s earlier trips past the sun. The research will take years.

The Parker probe has already gathered much information. This has changed our understanding of the sun and its effects on our planet. Trillions of other stars are scattered throughout space. The mission could also provide insight into their inner workings. “The sun is the closest star to us,” says Rawafi. “We can study it in more detail than any other star in the universe. This mission is an experience of a lifetime.”