August 21, 2014

Why should NASA study the Sun?

As children, we are told never to look directly at the Sun, especially through the lens of a camera, telescope or magnifying glass. Even if a person used the special filters that would allow them to gaze at the Sun, they would not be able to see all of the wavelengths of light emanating from the Sun. To fully understand our star, scientists must use spacecraft that can observe this invisible light before it is absorbed by the atmosphere.

“Certain wavelengths either do not make it through Earth’s atmosphere or cannot be seen by our eyes, so we cannot use normal optical telescopes to look at the spectrum,” Dean Pesnell, the project scientist for the Solar Dynamics Observatory (SDO) at NASA’s Goddard Space Flight Center, told NASA's Max Gleber.

There are several spacecraft which can observe these ultraviolet wavelengths. SDO, in particular, has four telescopes designed to capture images of the Sun in the ultraviolet spectrum. A specially coated mirror within the telescope filters and amplifies the ultraviolet light's otherwise poor reflection. In a process similar to how a cell phone camera captures visible light, the camera aboard SDO records the incoming photons as pixels and converts them into electrical signals.

“It’s exactly the same process, whether it’s ultraviolet light, infrared light, visible light, or radio,” said Joseph Gurman, project scientist for both the Solar and Heliospheric Observatory and the Solar Terrestrial Relations Observatory at Goddard. “In this case we’re trying to understand how the sun changes and how those changes affect life here on Earth.”

Molecular radiation damage, such as sunburns that lead to skin cancer, is caused by ultraviolet light. Ultraviolet radiation, and the solar storms that accompany it, can disrupt spacecraft navigation and communications. “These are very damaging, energetic photons, and we want to understand what chain of events produces these photons,” Pesnell said.

Most of this radiation is absorbed by the Earth's atmosphere before it can reach the ground, making life on our planet possible. The absorption makes studying the ultraviolet spectrum impossible from the ground, however, so spacecraft such as SDO are necessary to understand and study the lightwaves.

“Ultraviolet light from the sun can show us the origins of solar storms that can lead to power outages, cell phone disruptions, and delays in shipping packages due to the rerouting of planes from over the pole,” Gurman said.

The researchers hope to use this new understanding of the sun's atmosphere to predict the powerful solar events, such as coronal mass ejections (CMEs) and solar flares, that can affect life here on Earth. For example, NOAA's Space Weather Prediction Center could use the predictions to alert power companies of impending events to avoid power outages.

“You really want to know what’s happening on the sun as soon as you can,” said Jack Ireland, a solar visualization specialist at Goddard. “We can then use computer models to estimate how solar events will affect Earth’s space environment.”



Image credit: NASA