The Sun, 21 August 2017
While observers in North America will enjoy views of a total solar eclipse later today as the Moon slips between Earth and the Sun, it's business as usual for our PROBA2 and SOHO satellites.
PROBA2 is expected to capture a series of partial eclipses, while SOHO will provide context images of the Sun and its extended atmosphere, or corona. The corona can only be seen from Earth with the naked eye during an eclipse when the Moon blocks out the bright light from the Sun, but SOHO can observe it all the time using special filters and 'occulting masks'.
An example can be seen here, which is a composite of two SOHO images and a PROBA2 image taken earlier this morning, and composed using JHelioviewer. The central image shows an extreme-ultraviolet image of the solar disc taken by PROBA2 at 05:39 UTC, while the corona and extended atmospheric features are seen by SOHO in the red image from 2–6 solar radii, and beyond in blue (SOHO can see up to about 32 solar radii) at 00:48 and 00:54 UTC, respectively. The black circular region corresponds to an occulting mask to cut out direct sunlight that would otherwise obscure the details close to the Sun – similar to the effect of the Moon in a total solar eclipse.
Near-realtime images of the Sun from SOHO are always available here, and in the days leading up to today's total eclipse these frequent images give scientists an idea of how the corona will look during their observations. This enables them to plan specific observations of any special regions of interest, and in the context of the state of the Sun's activity.
A team of dedicated astronomers from ESA will be studying the eclipse from the path of totality in the USA, hoping for clear skies to capture this celestial spectacular.
In addition, astronauts aboard the International Space Station, including ESA's Paolo Nespoli, should also be able to see some aspects of the eclipse, such as a partial eclipse and the shadow of the Moon on the surface of our planet.
Follow ESA's ground-based activities via http://cesar.esa.int and join the conversation on Twitter with #eclipse2017 and #solareclipse. We'll keep you posted on our activities – from ground and space – via @esascience.
Remember: never look directly at the Sun, even when partially eclipsed, without proper eye protection such as special solar eclipse glasses, or you risk permanent eye damage.