Above: Thor’s Helmet, NGC2359 Emissions nebula. Astrophotography by Mario Motta, MD. All Rights Reserved Below: The constellation Canis Major contains Sirius, the brightest star. The constellation suggests the outline of a dog, sometimes fancied to be the dog accompanying Orion (the Hunter).
Sparkling, blue-white Sirius the Dog Star, the brightest star in the night sky, rises in the east-southeast 20 minutes after sunset this evening and will rise simultaneously with sunset by month’s end. As twilight deepens, Sirius – from the ancient Greek Seirios for “scorcher” or “glowing” – appears above the skyline leading one of winter’s most alluring constellations, Canus Major, or The Big Dog, into the sky. The Dog Star’s brilliance, -1.46 magnitude, is partly due to its being one of our solar system’s closest neighbors among the stars, at 8.6 light years distant. By contrast, the cosmic phenomenon, Thor’s Helmet, pictured above, is about 12,000 light years from Earth. Sirius is eminently visible even in the city sky. Look from nightfall in the southeast until after midnight in the southwest.
I was intrigued when dark sky advocate and amateur astronomer, Dr. Mario Motta, introduced me to Thor’s Helmet, an emission nebula that, when viewed with a telescope from Earth, is located in, or close to, the boundaries of The Big Dog.
Look to the center of Dr. Motta’s photograph to find what appears to be the uncanny presence of a battle helmet. The figure is widely known as Thor’s Helmet. In Norse mythology, Thor is protector of humankind and god of the sky, associated with thunder and lightning. According to NASA, the nebula “Thor’s Helmet spans about 30 light-years across. In fact, the helmet is more like an interstellar bubble, blown as a fast wind—from the bright star near the center of the bubble’s blue-hued region—sweeps through a surrounding molecular cloud.”
Find Sirius whenever you look up to the sky in the coming months and, in your mind’s eye, look far beyond the brilliant star to the cosmic phenomenon brought to us by Dr. Motta.
2021 January 28: An hour after sunset in late January, Sirius appears low in the southeast. Diagram by Dr. Jeffrey L. Hunt. Courtesy of WhentheCurvesLineUp.com
January’s Full Wolf (or Hunger) Moon rises at 4:55pm on Thursday the 28th as the Sun sets on the opposite horizon at 5:02pm. Twilight gathers half an hour later.