We Are About to Get the Closest Images of the Sun Ever Captured

Next month, scientists are set to release the closest images of the sun ever captured. On Monday, the European Space Agency (ESA) and NASA's Solar Orbiter spacecraft reached its first close approach—or perihelion—to our star, coming within 48 million miles of its surface.

ESA will now test the Orbiter's ten science instruments and begin taking images of the sun using the six onboard telescopes. These will be released in mid-July after processing.

"We have never taken pictures of the sun from a closer distance than this," Solar Orbiter Project Scientist Daniel Müller said in a statement. "There have been higher resolution close-ups, for example, taken by the four-meter Daniel K. Inouye Solar Telescope in Hawaii earlier this year. But from Earth, with the atmosphere between the telescope and the sun, you can only see a small part of the solar spectrum that you can see from space."

NASA's Parker Solar Probe travels closer to the sun than the ESA's Orbiter. In October 2018, for example, the probe became the closest-ever artificial object to the sun. However, this spacecraft is not equipped with telescopes that can image the sun directly.

"Our ultraviolet imaging telescopes have the same spatial resolution as those of NASA's Solar Dynamic Observatory (SDO), which takes high-resolution images of the sun from an orbit close to Earth. Because we are currently at half the distance to the sun, our images have twice SDO's resolution during this perihelion," Müller said.

ESA, Solar Orbiter
Artist's illustration of ESA's Solar Orbiter. ESA/Medialab

ESA launched the Solar Orbiter in February of this year, and the spacecraft is now entering the initial "cruise phase" of its mission, which is scheduled to end in November 2021.

During this two-year phase, the spacecraft will perform two gravity-assist fly-bys of Venus, and one of Earth that will put the spacecraft in a 180-day-long orbit around the sun, from which the orbiter will begin its main scientific mission

In the course of this orbit, the spacecraft will make a close approach to our star every six months, coming as close as 27 million miles—which is closer than the orbit of Mercury. The first of these close approaches will take place in early 2022, although the orbiter will "only" come within a distance of 30 million miles.

As the main science phase progresses, the Orbiter will perform further gravity-assist maneuvers around Venus that will move the spacecraft out of the solar system's plane in which the planets orbit. This will enable the spacecraft to see the polar region of the sun clearly for the first time ever, helping to shed new light on the star's magnetic field.

"Solar Orbiter will provide the first views of the sun's uncharted polar regions, giving unprecedented insight into how our parent star works," Müller told Newsweek. "It will also investigate how intense radiation and energetic particles being blasted out from the sun and carried by the solar wind through the solar system impact our home planet, to better understand and predict periods of stormy space weather."

"Solar storms have the potential to knock out power grids, disrupt air traffic and telecommunications, and endanger space-walking astronauts. In more general terms, Solar Orbiter will help us understand how our star creates and controls the heliosphere, the giant bubble of plasma that surrounds the whole solar system and influences the planets within it. Fundamentally, understanding the interrelation between the sun and the heliosphere is key to understanding how our solar system works."

During the initial cruise phase of the mission, ESA operators will test the spacecraft's instruments and start collecting data, to ensure that the Orbiter is ready for its main scientific mission. The closest-ever images will be part of this testing process.

"For the first time, we will be able to put together the images from all our telescopes and see how they take complementary data of the various parts of the sun including the surface, the outer atmosphere, or corona, and the wider heliosphere around it," Müller said.

Because the spacecraft is so far away from Earth—around 83 million miles—the close approach image data will take around a week to download using the ESA's 35-meter deep-space antenna in Malargüe, Argentina.

"We have a nine-hour download window every day but we are already very far from Earth, so the data rate is much lower than it was in the early weeks of the mission when we were still very close to Earth," Müller said.

"In the later phases of the mission, it will occasionally take up to several months to download all the data because Solar Orbiter really is a deep space mission. Unlike near-Earth missions, we can store a lot of data on-board and downlink it when we are closer to home again and the data connection is much better."

Solar Orbiter must operate for years in one of the most hostile regions of the Solar System. At closest approach, the spacecraft will experience 13 times the intensity of terrestrial sunlight and temperatures of up to 970 degrees Fahrenheit.

"To protect the spacecraft from the sun's heat, Solar Orbiter has been designed around its heat shield: a sandwich of high-temperature multilayer insulation," Müller said. "The outer part of the heat shield is made of carbon fiber, covered in 20 layers of titanium sheets that have been surface-treated with the SolarBlack thermo-optical coating, which has been chosen because it maintains its thermo-optical properties also after years of exposure to intense radiation. Openings allow sensors to peep through, some behind protective glass or beryllium."

"Solar Orbiter's protective shield 'takes the heat' to ensure that the temperature of the spacecraft body, including its sensitive science instruments, always stays below 50 C—as cool as a hot summer day on Earth."

In January this year, scientists captured the most detailed images of the sun ever taken using the Daniel K. Inouye Solar Telescope in Hawaii. These photos revealed tiny features in the star's magnetic field that have never been observed before.

This article was updated to include additional comments from Daniel Müller.