W50 is now a giant manatee nebula

Posted by Thomas Anderson

The National Science Foundation's (NSF) Karl G. Jansky Very Large Array (VLA) has captured a new view of a 20,000-year old supernova remnant - offering additional clues to the history of the giant cloud which bears a distinct resemblance to the Florida Manatee.

Indeed, W50 is one of the largest supernova remnants ever viewed by the VLA. At nearly 700 light years across, it covers two degrees on the sky, or the span of four full Moons.

According to astronomers, the enormous W50 cloud likely formed when a giant star, approximately 18,000 light years away in the constellation of Aquila, exploded as a supernova around twenty thousand years ago, sending its outer gases flying outward in an expanding bubble.

The remaining gravitationally-crushed relic of the giant star, most likely a black hole, feeds on gas from a very close companion star. The cannibalized gas pools in a disk around the black hole. The disk and black hole's network of powerful magnetic field lines acts like an enormous railroad system to snag charged particles out of the disk - channeling them outward in powerful jets traveling at nearly the speed of light.

This system of a black hole and its feeder star shines brightly in both radio waves and X-rays and is known collectively as the SS433 microquasar.

Over time, the microquasar's jets have forced their way through the expanding gases of the W50 bubble, eventually punching bulges outward on either side. The jets also wobble, much like an unstable spinning top, blazing vivid corkscrew patterns across the inflating bulges.

Optically bright astronomical objects, those visible to the eye and optical telescopes, often are nicknamed for their earthly likenesses, such as the Whirlpool Galaxy and Owl Nebula. Invisible W50 comes by its less catchy name by being the 50th radio source listed in the Westerhout Catalog, assembled in 1958 by Dutch astronomer, Gart Westerhout.

When the VLA's giant W50 image reached the NRAO Director's office, Heidi Winter, the Director's Executive Assistant, immediately saw the likeness to a manatee, the endangered marine mammals known as "sea cows" that congregate in warm waters in the southeastern United States.

Florida Manatees are gentle giants that average around 10 feet long, weigh over 1,000 pounds, and spend up to eight hours a day grazing on sea plants. They occupy the remainder of their day resting, often on their backs with their flippers crossed over their large bellies, in a pose closely resembling W50.

Dangerous encounters with boat propellers injure many of these curious herbivores, giving them deep, curved scars similar in appearance to the arcs made by the powerful jets on the large W50 remnant.

As per Winter's suggestion, the National Radio Astronomy Observatory has now adopted the very apt new nickname for W50: The Manatee Nebula.