Season’s greetings from Comet Lovejoy and the rest of the gang

ESO optician Guillaume Blanchard captured this wide-angle photo of Comet Lovejoy just two days ago on December 22. Comet Lovejoy has been the talk of the astronomy community over the past few weeks. It was first discovered on 27 November by the Australian amateur astronomer Terry Lovejoy . Click for a LARGE version. Credit: G. Blanchard / ESO

There are so many excellent photos out there of Comet Lovejoy, but this one, taken at the European Southern Observatory’s Paranal Observatory in Chile stands out not only for the comet but for everything else it shows including the Milky Way’s two brightest companion galaxies, a famous dark nebula and the zodiacal light.

If you follow the Milky Way up to the right, the first dark patch you bump into is the Coal Sack, a prominent cloud of interstellar dust thick enough to block the more distant background stars. To the eye, it looks like a missing piece of the Milky Way. If stars were embedded in the nebula, their light would reflect off the dust and cause it to glow. Then we’d see it a bright, reflection nebula. Nearly touching the Coal Sack on the upper right is the compact, four-starred constellation Crux, better known as the Southern Cross.

The Coal Sack (left), is located 600 light years away within the Milky Way. The Southern Cross is outlined at right. Credit:ESO/S.Brunier

Now take a look to the lower right of the Milky Way between the two observatory  buildings. Those two fuzzy blobs are satellite galaxies of the Milky Way called the Large and Small Magellanic Clouds and only observable from southern latitudes. The Large Cloud is 160,000 light years away; the Small is 200,000.

To the left of the comet is a faint, finger-like glow called the zodiacal light. This is another cloud of dust but one created by generations of comets. Heated by the sun, a comet’s dirty, dusty ice vaporizes and is driven back to form a tail. Material from the tail is spread along the comet’s orbit and diffuses into a stream of dust over time.

With thousands of comets coming and going over the eons, dust has built up in the plane of the solar system. Illuminated by sunlight, we see it as a cone or finger of soft light at early dawn or dusk. The name ‘zodiacal’ tells us the dust is concentrated along the zodiac, a belt of sky that includes famous 12 constellations, which, you guessed it, is centered on the plane of the solar system.

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