Starburst captured: Students photograph exploding star in pinwheel galaxy

ScienceDaily (Oct. 18, 2011) — In the Pinwheel Galaxy some 21 million light years from Earth, a supernova beams brightly, out-shining its cosmic neighbors and causing a stir among starwatchers.

Students in University of Delaware Prof. Judi Provencal's Observational Astronomy class (PHYS 469) photographed the exploding star last week using the telescope at Mt. Cuba Astronomical Observatory in Greenville, Del., which has a lens spanning 24 inches in diameter.

"The supernova, a star that is blowing itself to bits, is the brightest object in the lower center of the image," Provencal notes. "It is the brightest supernova in the last 20 years and might be visible with binoculars."

The bursting star, known as PTF 11kly, will eventually fade over the next year or so and then turn into a neutron star or a black hole. The material ejected when it exploded may form new stars.

According to Provencal, PTF 11kly is a "Type 1a" supernova, which means it's half of a "stellar team" known as a binary star. One of the stars is an "ordinary" star, and the other is a white dwarf, a super-dense star that is the size of Earth, but has the mass of the sun. Because it doesn't have nuclear reactions firing away in its core, the white dwarf does not generate any internal energy. Instead, it's supported against gravity by "electron degeneracy pressure" which occurs when a huge number of electrons are compacted tightly together in a small volume.

The two stars of the binary team orbit very closely together, so close that the "ordinary" star transfers material to the white dwarf. When the white dwarf gains enough material that it reaches a critical mass (about 1.4 times the mass of the sun), electron degeneracy pressure fails and the star will collapse in on itself. This produces a lot of energy, which we see as the supernova, Provencal explains.

"These are the types of supernova that were used to determine that the universe is actually accelerating in its expansion, which has led to the whole field of dark energy," Provencal says.

The Pinwheel Galaxy inhabited by the PTF 11kly supernova was discovered in 1781 by French astronomer Pierre Mechain, who thought it was a nebula, a gas cloud from which new stars are born. Erwin Hubble later would show that it is indeed a full-fledged galaxy.

Mechain's fellow astronomer Charles Messier would include it as an item, today still referred to as "Messier 101," or M101, in his 1781 astronomical catalog.

"Messier's list was supposed to help with comet hunting since it was a list of fuzzy objects that didn't move in the sky. Comet hunting was a big deal back then," notes Provencal.

The Pinwheel Galaxy is a spiral galaxy much like our own Milky Way. It's called a spiral galaxy for the spiral arms or "spokes" that curve away from a center disk of highly concentrated stars. The stars in these spokes are younger and thus hotter and brighter than the stars at the center.

Although the Pinwheel Galaxy is playing host to the brightest, nearest supernova seen from Earth in years, starwatchers should know that our own Milky Way also sports supernovae from time to time -- the most recent one was recorded in 1572, Provencal says.

Recommend this story on Facebook, Twitter,
and Google +1:

Other bookmarking and sharing tools:

Story Source:

The above story is reprinted from materials provided by University of Delaware. The original article was written by Tracey Bryant.

Note: ScienceDaily reserves the right to edit materials for content and length. For further information, please contact the source cited above.

Note: If no author is given, the source is cited instead.

Disclaimer: Views expressed in this article do not necessarily reflect those of ScienceDaily or its staff.

View the original article here

Starburst captured: Students photograph exploding star in pinwheel galaxy

ScienceDaily (Oct. 18, 2011) — In the Pinwheel Galaxy some 21 million light years from Earth, a supernova beams brightly, out-shining its cosmic neighbors and causing a stir among starwatchers.

Students in University of Delaware Prof. Judi Provencal's Observational Astronomy class (PHYS 469) photographed the exploding star last week using the telescope at Mt. Cuba Astronomical Observatory in Greenville, Del., which has a lens spanning 24 inches in diameter.

"The supernova, a star that is blowing itself to bits, is the brightest object in the lower center of the image," Provencal notes. "It is the brightest supernova in the last 20 years and might be visible with binoculars."

The bursting star, known as PTF 11kly, will eventually fade over the next year or so and then turn into a neutron star or a black hole. The material ejected when it exploded may form new stars.

According to Provencal, PTF 11kly is a "Type 1a" supernova, which means it's half of a "stellar team" known as a binary star. One of the stars is an "ordinary" star, and the other is a white dwarf, a super-dense star that is the size of Earth, but has the mass of the sun. Because it doesn't have nuclear reactions firing away in its core, the white dwarf does not generate any internal energy. Instead, it's supported against gravity by "electron degeneracy pressure" which occurs when a huge number of electrons are compacted tightly together in a small volume.

The two stars of the binary team orbit very closely together, so close that the "ordinary" star transfers material to the white dwarf. When the white dwarf gains enough material that it reaches a critical mass (about 1.4 times the mass of the sun), electron degeneracy pressure fails and the star will collapse in on itself. This produces a lot of energy, which we see as the supernova, Provencal explains.

"These are the types of supernova that were used to determine that the universe is actually accelerating in its expansion, which has led to the whole field of dark energy," Provencal says.

The Pinwheel Galaxy inhabited by the PTF 11kly supernova was discovered in 1781 by French astronomer Pierre Mechain, who thought it was a nebula, a gas cloud from which new stars are born. Erwin Hubble later would show that it is indeed a full-fledged galaxy.

Mechain's fellow astronomer Charles Messier would include it as an item, today still referred to as "Messier 101," or M101, in his 1781 astronomical catalog.

"Messier's list was supposed to help with comet hunting since it was a list of fuzzy objects that didn't move in the sky. Comet hunting was a big deal back then," notes Provencal.

The Pinwheel Galaxy is a spiral galaxy much like our own Milky Way. It's called a spiral galaxy for the spiral arms or "spokes" that curve away from a center disk of highly concentrated stars. The stars in these spokes are younger and thus hotter and brighter than the stars at the center.

Although the Pinwheel Galaxy is playing host to the brightest, nearest supernova seen from Earth in years, starwatchers should know that our own Milky Way also sports supernovae from time to time -- the most recent one was recorded in 1572, Provencal says.

Recommend this story on Facebook, Twitter,
and Google +1:

Other bookmarking and sharing tools:

Story Source:

The above story is reprinted from materials provided by University of Delaware. The original article was written by Tracey Bryant.

Note: ScienceDaily reserves the right to edit materials for content and length. For further information, please contact the source cited above.

Note: If no author is given, the source is cited instead.

Disclaimer: Views expressed in this article do not necessarily reflect those of ScienceDaily or its staff.

View the original article here

Rogue waves captured

Re-creating monster swells in a tank helps explain their originWeb edition : Friday, May 20th, 2011 Wave gauges in a water tank spot the peak of a tiny rogue wave.Amin Chabchoub

Freak waves that swallow ships whole have been re-created in a tank of water. Though these tiny terrors are only centimeters high, a devilishly difficult mathematical equation describing their shape may help to explain the origins of massive rogue waves at sea..

Sailors have long swapped stories about walls of water leaping up in the open ocean — even in calm water — without warning or obvious cause. But for centuries, rogue waves were little more than talk; no one had ever measured one with scientific instruments.

Then on New Year’s Eve of 1995, a laser on an oil rig off Norway’s coast recorded one of these rare events: a wave 26 meters from bottom to top, flanked by deep troughs on either side.

This wave and others measured since look like breather waves, says Amin Chabchoub, a mathematician at the Hamburg University of Technology in Germany. A breather wave is an anomaly in a series of waves that sucks in the energy of its neighbors and puffs itself up to a great height.

A tiny rogue wave between two troughs (solid line) looks like a nonlinear mathematical equation solved in the 1980s (dashed line). Amin Chabchoub

The nonlinear interactions that allow for this energy theft were described by mathematician Howell Peregrine in 1983. His solutions of nonlinear Schrödinger equations showed that pulselike waves called Peregrine solitons can pop out of sine waves under certain conditions.  

“For a long time, nobody really thought this mathematics would be applicable to the ocean,” says Al Osborne, a physicist at the University of Turin in Italy. “Not only is it applicable, but we’re now undergoing a paradigm shift in understanding ocean waves.”

To make a Peregrine soliton, Chabchoub wobbled a paddle back and forth at the end of a long water tank. Regularly spaced waves about a centimeter high emerged and rolled across the surface. Then he gave the paddle a precise jerk – introducing an anomaly.

“It’s possible that the wind could generate a similar modulation or perturbation in the open sea,” says Chabchoub, who describes the experiment in a paper in the May 20 Physical Review Letters.

In the 15-meter tub, this spot grew to a height of about 3 centimeters before dying down — hardly enough to make a rubber ducky quack in fear. Flanked by two deep troughs, the rising peak moved half as fast as the background waves. It satisfied both Peregrine’s mathematics and a common statistical view that a rogue wave is something at least two to three times the size of the tallest one-third of the other waves averaged.

In theory, the toy waves in the water tank should scale up to oceanic proportions. But oceans are much messier than water tanks. Normal ocean waves come in a variety of sizes and speeds, and other nonlinear effects may play a role in creating rogue waves.

“You add an almost imperceptible amount of noise, and all sorts of wacky and unexpected things can happen,” says Daniel Solli, a physicist at UCLA who created the first Peregrine soliton in light waves.

Chabchoub and his colleagues are exploring ways to introduce a little more mess into their tank to see what other wacky conditions can give rise to freak waves.  

Found in: Earth and Matter & Energy

View the original article here