Comets, as everyone knows, are unpredictable. The two comets headlining the news this week certainly live up to this reputation. Most star-grazers, comets that approach too close to the sun, just crumble away. But C/2015 D1 SOHO, first seen by NASA’s Solar and Heliospheric Observatory (SOHO) as it rushed past the sun at a distance of only 2.6 billion miles, has survived. Minus its head. It now looks like a feather of cosmic dust. And Comet Lovejoy, no longer visible to the unaided eye, made an unexpected appearance in a photograph taken by the Dark Energy Survey.
C/2015 D1 SOHO was discovered on February 18, just a day before it passed perihelion, by Worachate Boonplod. The Thai amateur astronomer has discovered over 35 comets by scanning SOHO images. On February 27, C/2015 D1 SOHO was photographed again, now running through Pisces and Pegasus, looking like a long glittering smudge of dust glowing in reflected sunlight.
As the night sky begins to darken again after the full moon, amateur astronomers have a chance of seeing it through telescopes. The chart shows its position through the end of March. If you do find it, amateur astronomer and writer Bob King would love to hear from you.
Lovejoy, the comet with the blue head and green tail, was unexpectedly caught on film by the Dark Energy Camera, which is the world’s most powerful digital camera. The unplanned picture of the comet shows the stars and galaxies that were the camera’s object through the haze of the comet’s tail. The camera is attached to a telescope at the Cerro Tololo Inter-American Observatory in the Andes Mountains of Chile.
Dark energy is the name given to whatever is making the universe accelerate. While the Theory of Relativity would predict that the universe is slowing down, the extreme brightness of distant supernovae, seen for the first time in the 1990s, suggest otherwise. The Dark Energy Survey maps the southern sky in detail to find answers to this puzzle.