A million miles from planet Earth, last weekend the STEREO B spacecraft found itself in the shadow of the Moon. So, looking toward the Sun, extreme ultraviolet cameras onboard STEREO B were able to record a stunning movie of a lunar transit (aka solar eclipse), as the Moon tracked across the solar disk. Each frame of the movie is a false-color composite of images made through four different filters that highlight temperature regimes and structures in the upper solar atmosphere. In this frame, large bright active regions, seen as dark sunspots in visible light, flank the Moon's silhouetted disk. The Moon appears small, less than 1/4th the size seen from Earth, because the spacecraft-Moon separation is over four times the Earth-Moon distance. Tonight, the Moon will find itself in planet Earth's shadow in a total lunar eclipse.

From the Bad Astronomy blog, www.badastronomy.com, which just named this as one of the best astronomical images of the year: "Studying the Sun seems like a pretty good idea; as the major source of light and heat for our planet, it’s a good thing that we try to understand it. And the Sun is a star, with all that implies: it’s huge in size, and frightening in its energy production.

To better understand it and the complicated nature of its surface activity, NASA launched a pair of satellites that can take pictures of the Sun simultaneously from different angles, providing a 3D view of our nearest star. They’re called the Solar Terrestrial Relations Observatory, or (haha) STEREO.

One satellite orbits the Sun ahead of the Earth, and the other behind. They stay in the same orbital plane as the Earth does in its travels around the Sun, and that means that sometimes you get interesting geometric situations which arise. The STEREO team realized that there would be a time when the Moon would pass in front of the Sun as seen by one of the spacecraft. Solar eclipses are rare on Earth, but from STEREO’s vantage it would be even more unusual.

From the Earth, the Sun is about 400 times farther away than the Moon, and is also about 400 times the Moon’s physical size. These two characteristics cancel out, meaning the Sun and Moon are about the same apparent size in the sky, so every solar eclipse has the Moon slipping in front of the Sun, with the dark disk of the Moon just barely (if even) covering the bright disk of the Sun.

That is, every solar eclipse as seen from the Earth.

But STEREO was receding from the Earth and Moon. To it, the Moon appeared much smaller than we see it, stuck as we are on the surface of our planet. The Sun, however, was still at about the same distance, and therefore looked the same size as we see it. This means that, to STEREO, the Moon appeared far smaller than the Sun.

Not long after launch, the situation arose that the Moon would pass directly in front of the Sun as seen from one of the spacecraft. STEREO turned its eye that way, and recorded what may be the most remarkable footage of a solar eclipse ever taken".

*promote

Video cannot be promoted by therealblankman because therealblankman promoted a post less than 7 days ago.

Isn't this a solar eclipse?