The Ghostly Glow of Gegenschein


Northern Spring Sky Panorama

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.

Orion over the Old Barn

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 

 

A Panorama of the Spring and Winter Sky


Winter and Spring Sky Panorama

I present a sweeping panorama of the winter and spring stars on a February night. 

The lead image is a panorama I shot last Saturday, February 27 that takes in about 200° of sky from northeast to west, and nearly to the zenith. It encompasses most of the northern spring and winter stars and constellations.

I’ve added the labels to help you pick out the celestial highlights. The winter sky, containing Orion as the central constellation, is at right setting into the west. This area of sky contains a rich collection of bright stars and identifiable constellations.

The left side of the sky contains the spring constellations, now coming into view in the east. Note how that area of sky is sparsely populated by bright stars. You can see the Big Dipper, Regulus in Leo, and Arcturus rising at lower left.

The reason for the difference is the Milky Way – you can see it at right arcing up from the southern horizon passing by Orion and through Gemini, Taurus and Auriga. In that direction we are looking into the outlying spirals arms of our galaxy, toward rich areas of star formation.

To the east, at left, we are looking at right angles out of the plane of our spiral galaxy, toward the galactic North Pole, here just left of Leo. In that direction there are very few bright stars between us and the starless depths of intergalactic space. The spring sky is rather blank compared to the rich winter sky.

But you can see Jupiter, the brightest object in view here, and now prominent in the evening sky.

Note one other subtle glow just above Jupiter. That diffuse glow is the Gegenschein, caused by sunlight reflecting off interplanetary dust opposite the Sun in our solar system and in the plane of the ecliptic.

Jupiter is just east (left) of the Gegenschein here, as Jupiter was then just over a week before its date of opposition, March 8. By then the Gegenschein will have moved to superimpose right over Jupiter, as both then lie opposite the Sun.

Winter and Spring Sky Panorama

I shot this scene from home on February 27, 2016, using the new iOptron iPano motorized “gigapan” unit, which I programmed to move and shoot 36 exposures with the Canon 5D MkII and 35mm lens, arranged in 4 rows high with 9 panels wide in each row from east to west. The result is a huge mosaic, 24,000 by 10,000 pixels.

Each exposure was 25 seconds at f/2 and at ISO 3200. The camera was not tracking the sky. I stitched the 36 segments with PTGui using its Spherical Fisheye projection. The image has black margins but I think the circular format is more suggestive of the spherical dome of the sky above and around you. But that’s me, a longtime planetarium show producer.

Next time I will shoot the zenith cap images as well!

— Alan, February 29, 2016 / © 2016 Alan Dyer / www.amazingsky.com

 

Zodiacal Light – Dawn’s Early Light


Zodiacal Light in Dawn Sky (Oct 2013)

The ghostly glow of comet dust brightens an October dawn.

This is the zodiacal light, as it appeared two mornings ago in the pre-dawn sky from my backyard in southern Alberta. This tapering glow angled up from the horizon is best spotted in the eastern sky on clear and moonless autumn mornings, like this one.

What you are seeing is sunlight reflected off dust left by passing comets in the inner solar system. So while this glow looks like it might originate in our atmosphere it really comes from dust out in interplanetary space.

This subtle glow, often called the “false dawn,” appears in the hour or so before the true dawn begins to brighten the sky too much (its purple light is just starting to light the horizon here).

Also visible here: Sirius at far right, Jupiter above centre, the Beehive star cluster below Jupiter, and Leo rising embedded in the zodiacal light, with Mars just above Regulus, Leo’s brightest star. The planets lie along the zodiacal light because the dust that causes it also lies in the same plane as the orbits of the planets, the ecliptic plane.

I shot this with a 14mm lens for a stack of four 2-minute tracked exposures, but with the horizon coming from just one of the exposures to minimize blurring from the moving camera slowly following the sky.

– Alan, October 10, 2013 / © 2013 Alan Dyer

 

Moon and Mars in the Morning


Moon, Mars & Regulus (Oct 1, 2013)

The waning Moon shines below Mars and beside the star Regulus in the dawn twilight.

This was the scene before sunrise this morning with the waning crescent Moon near Mars (above the Moon) and the star Regulus (left of the Moon) in Leo. Mars is getting the attention this week as Comet ISON flies near the planet and also appears near Mars in our earthly sky.

However, the comet is still very faint and needs a large telescope to see from Earth. It will be interesting to see if any of the Mars probes are able to image it, as ISON is still fainter than predicted and might be beyond their reach to detect. But if they do, they could help determine just how big ISON is and that in turn will tell us if it might survive its November 28 passage round the Sun to become a fine dawn object in December.

– Alan, October 1, 2013 / © 2013 Alan Dyer

 

Mars Down the Road


Here’s Mars, now at its closest and brightest in two years. Look for it due east in the early evening, as a rising reddish star in Leo.

On March 7, the Full Moon sits next to Mars, making for a fine sight as the pair rise together at sunset.

I took this shot March 4, with the Moon just off the frame at the top. Here, the eastbound county road seems to head off across the Prairies to Mars. It’s got a long way to go. Even at its closest right now, Mars is still 100 million kilometres away.

— Alan, March 6, 2012 / © 2012 Alan Dyer