The Ghostly Glow of Gegenschein
It takes a dark spring night to see it well, but now lurking near Jupiter is a ghostly sky glow called Gegenschein.
This diffuse glow lies directly opposite the Sun. It is caused by sunlight reflecting off interplanetary dust particles in the outer solar system. They reflect light more effectively at the anti-Sun point where each dust particle is fully lit by the Sun.
Like the Sun, the Gegenschein moves around the sky along the ecliptic, moving about a degree from west to east from night to night. March and April provide good nights for seeing the Gegenschein as it then lies in an area of sky far from the Milky Way.
Even so, it is very subtle to the unaided eye. Look south at about 1 a.m. local daylight time.
However, this year, in early April the Gegenschein will be more difficult as it will then lie right on top of Jupiter, as that planet reaches its point opposite the Sun on April 7. Jupiter will then be superimposed on the Gegenschein.
The main image at top is a 7-image vertical panorama of the spring sky, from Corvus and Virgo above the horizon, up past Leo, into Ursa Major and the Big Dipper overhead. Spica lies below bright Jupiter, Arcturus in Böotes is at left, while Regulus in Leo is at right. The grouping of stars near centre is the Coma Berenices star cluster.
Earlier in the night, I shot the sky’s other main glow – the Milky Way, as the winter portion of the Milky Way around Orion set into the southwest.
But over in the west, at the right edge of the frame, is the Zodiacal Light, caused by the same dust particles that create the Gegenschein, but that are located in the inner solar system between us and the Sun.
The Zodiacal Light is better depicted in images in my previous post from Dinosaur Park.
We bid adieu to the winter Milky Way now. As it departs we are left with an evening sky without the Milky Way visible at all. As seen from northern latitudes it lies along the horizon.
But later in spring, late at night, we’ll see the summer Milky Way rising, beginning its seasons of prominence until late autumn.
— Alan, March 19, 2017 / © 2017 Alan Dyer / AmazingSky.com