TAMPA, Florida -- You might not expect a manatee, an endangered species at Crystal River National Wildlife Refuge north of
Tampa, Florida to have much in common with a celestial cloud of gas. But the
National Radio Astronomy Observatory offered proof of the physical resemblance at the Florida Manatee Festival on Saturday, January 19. The NRAO also used the occasion to rename the gas cloud the Manatee Nebula.
A new view of a 20,000-year old supernova remnant demonstrates the
upgraded imaging power of the National Science Foundation’s (NSF) Karl
G. Jansky Very Large Array (VLA) and provides more clues to the history
of this giant cloud that resembles a beloved endangered species, the
Florida Manatee.
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 –
the span of four full Moons.
The enormous W50 cloud formed when a giant star, 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 that giant star, most
likely a black hole, feeds on gas from a very close, companion star.
The cannibalized gas collects 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 and
channel 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 micro quasar’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, like an unstable spinning top, and
blaze 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 Eagle, Crab, Pelican, and Owl Nebulae. 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, 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 1000 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.
Thanks to Ms. Winter’s suggestion, the National Radio Astronomy
Observatory has adopted a new nickname for W50: The Manatee Nebula. In
collaboration with the U.S. Fish and Wildlife Service.
SOURCES: National Radio Astronomy Observatory and Florida Fish and Wildlife Commission
Left Image: W50 supernova remnant in radio (green) against the infrared background of stars and dust (red). Credits: NRAO/AUI/NSF, K. Golap, M. Goss; NASA’s Wide Field Survey Explorer (WISE).
Right Image: A Florida Manatee rests underwater in Three Sisters Springs in Crystal River, Florida. Image Credit: Tracy Colson.
