While most people eagerly await the total solar eclipse in April, scientists are already planning to observe the next, except that it will be artificial.
Sun Shadow Play
For the last 14 years, the European Space Agency (ESA) has been planning and designing the Proba-3 mission. By September this year, it will finally be launched by the Polar Satellite Launch Vehicle (PSLV) launcher from India.
Proba-3 is the world's first precision formation flying mission, which will be demonstrated in a large-scale science experiment. It is designed to detect tiny, faint features in the extremely dim outer atmosphere of the Sun called the corona.
The mission will send two small satellites together in an orbit around the Earth to make this possible. The pair of probes, coronagraph, and occulter, will separate once in space but fly in tandem. The two satellites will mimic a natural solar eclipse, like the moon's passing in front of the sun. They will line up 472 feet (144 meters) apart so the occulter blocks out the sun's glaring disk for the coronagraph. This will be achieved autonomously without depending on guidance from the ground.
The two probes will take 19.5 hours to circle the Earth once, after which they will maintain their formation for 6 hours in each orbit to reduce fuel costs. This configuration will bring the corona into view, a feature so faints that it is only visible during a natural solar eclipse.
As seen by the observers on Earth, solar eclipses are not very common and do not last very long. According to astrophysicist Russell Howard from the John Hopkins University Applied Physics Lab, having images for hours compared to the normal five-to-ten-minute duration will make such a huge difference.
Coronagraphs typically include an occulter, so they can actually block out the bright disk of the sun themselves. However, they also experience data-damaging diffraction, resulting from light spilling around their edges. This phenomenon sometimes overshines very faint signals.
The best way to reduce data-damaging diffraction is to increase the distance between the coronagraph and the occulter. According to Proba-3's project manager, Damien Galano, this is exactly what the mission will do.
READ ALSO: Total Solar Eclipses Shed Light on the Temperature of Solar Winds and Sun's Corona
Why Study the Corona?
Corona refers to the upper portion of the Sun's atmosphere, extending thousands of kilometers above the visible surface. We normally cannot see the corona since the surface of the Sun is too bright to allow a glimpse of the much fainter solar atmosphere.
This region is also the part where the solar wind originates. Corona is just an extension of the sun's atmosphere, which engulfs all of the planets in the solar system.
Scientists discovered that the corona is much hotter than the sun's surface. Because of the high temperatures in this atmospheric layer, the particles move at a very high speed enough to escape the sun's gravity, traveling through space as the solar wind. If solar flares come from the corona, large amounts of energy can interact with our atmosphere and cause disruptions to power grids and satellite communications.
RELATED ARTICLE: ESA's Solar Orbiter Captures Tiny Magnetic Phenomenon on Sun's Outer Atmosphere That Makes It So Hot
Check out more news and information on Corona in Science Times.