NASA’s Solar Dynamics Observatory captured this image of Earth and the Moon transiting the Sun together on 13 September 2015. The edge of Earth, visible near the top of the frame, appears fuzzy because Earth’s atmosphere blocks different amounts of light at different altitudes. On the left, the Moon’s edge is perfectly crisp, because it has no atmosphere. This image was taken in extreme ultraviolet wavelengths of 171 angstroms. Though this light is invisible to our eyes, it is typically colourised in gold. Image credits: NASA/SDO.On 13 September 2015, as NASA’s Solar Dynamics Observatory, or SDO, kept up its constant watch on the Sun, its view was photobombed not once, but twice. Just as the Moon came into SDO’s field of view on a path to cross the Sun, Earth entered the picture, blocking SDO’s view completely. When SDO’s view of the Sun emerged from Earth’s shadow, the Moon was just completing its journey across the Sun’s face.This animation shows the relative movement of Earth and the Moon as they both crossed SDO’s field of view on 13 September 2015. Just as the Moon came into SDO’s field of view on a path to cross the Sun, Earth entered the picture, blocking SDO’s view completely. When SDO’s orbit finally emerged from behind Earth, the Moon was just completing its journey across the Sun’s face. Image credits: NASA/SDO.Though SDO sees dozens of Earth eclipses and several lunar transits each year, this is the first time ever that the two have coincided. This alignment of the Sun, Moon and Earth also resulted in a partial solar eclipse on 13 September, visible only from parts of Africa and Antarctica.
SDO’s orbit usually gives us unobstructed views of the Sun, but Earth’s revolution around the Sun means that SDO’s orbit passes behind Earth twice each year, for two to three weeks at a time. During these phases, Earth blocks SDO’s view of the Sun for anywhere from a few minutes to over an hour once each day.
You may notice that Earth’s outline looks fuzzy, while the Moon’s is crystal-clear. This is because — while the planet itself completely blocks the Sun’s light — Earth’s atmosphere is an incomplete barrier, blocking different amounts of light at different altitudes. On the other hand, the Moon has no atmosphere, so during the transit we can clearly see the crisp edges of the Moon’s horizon.
Observers in Western Europe with a clear sky around local midnight cannot fail to notice the conspicuous ‘star’ that is Jupiter low in the south. But look a span-and-a-half of an outstretched hand at arm’s length to Jupiter’s left and you’ll find another giant of the solar system – Saturn. The ringed planet is closest to Earth for 2019 on 9 July, so here is our quick observing guide.
As dusk fades to dark on the evening of Tuesday 15 November, observers in the British Isles and Western Europe can see the rising 16-day-old Moon less than 2 degrees away from Aldebaran in the constellation of Taurus. While an occultation of the star occurs around 17h UT for observers in Japan, central Asia and the Middle East, skywatchers in the UK will have to settle for a near miss.
Dark matter is an invisible, mysterious substance that makes up about 27 percent of all matter and energy in the universe. A new NASA study publishing this week proposes that when a stream of dark matter particles goes through a planet, the planet’s gravity bends and focuses the particles into an ultra-dense filament, or “hair,” of dark matter. In theory, there should be many such hairs sprouting from Earth.
