Tag Archives: Swift Telescope

Multiwavelength X-ray / infrared image of SN 1572 or Tycho's Nova, the remnant of a Type Ia supernova (NASA/CXC/JPL-Caltech/Calar Alto O. Krause et al.)

Astronomers paint a clearer picture of how supernovae are born

Supernovae are one of the most energetic and brightest events in the cosmos, often so powerful they outshine whole galaxies. They’re considered  to play a major role in our understanding of the Universe, which is why scientists have invested so much time and effort into studying them. A recent study of X-ray and ultraviolet observations from NASA’s Swift satellite has helped astronomers understand better how Type Ia supernovae come to be.

Multiwavelength X-ray / infrared image of SN 1572 or Tycho's Nova, the remnant of a Type Ia supernova (NASA/CXC/JPL-Caltech/Calar Alto O. Krause et al.)

Multiwavelength X-ray / infrared image of SN 1572 or Tycho's Nova, the remnant of a Type Ia supernova (NASA/CXC/JPL-Caltech/Calar Alto O. Krause et al.)

A Type Ia supernova forms when a white dwarf, the remnant of a star that has completed its normal life cycle and has ceased nuclear fusion,  reaches a critical mass and detonates. This certain supernova family has been found to be extremely useful to astronomers’ studies, who have used their intense brightness as beacons or candle lights to determine vast distances in space. Also, studies of Type Ia supernovae led to the discovery of dark energy, which garnered the 2011 Nobel Prize in Physics.

Despite the fact astronomers have known for decades how Type Ia supernovae form, the exact mechanisms that lead to their formation are currently yet obscured.

“For all their importance, it’s a bit embarrassing for astronomers that we don’t know fundamental facts about the environs of these supernovae,” says Stefan Immler, an astrophysicist at NASA’s Goddard Space Flight Center.

“Now, thanks to unprecedented X-ray and ultraviolet data from Swift, we have a clearer picture of what’s required to blow up these stars.”

What sets off a supernova

The main model of formation for a Type Ia supernova involves a close binary star system. There are two dominant theories regarding this. The first and most popular theory currently suggests a white dwarf orbits a normal star and pulls a stream of matter from it, feeding from it until it reaches the necessary mass and explodes into a supernova. A second possible mechanism for triggering a Type Ia supernova is the merger of two white dwarfs, which collide like vast hypermassive billiard balls leading to a cataclysmic blast.

NASA’s Swift satellite, which orbits the Earth and is primarily used to sniff out gamma-ray bursts emitted from far away black holes, is also used from time to time to study supernovae. Its latest find came after it was directed towards the closest Type Ia supernova, called SN 2011fe, offering scientists data that suggest the white dwarf from which it sprang was a particularly picky eater.

“It’s hard to understand how a white dwarf could eat itself to death while showing such good table manners,” said Alicia Soderberg of the Harvard-Smithsonian Center for Astrophysics (CfA).

Namely, the astronomers couldn’t find any signs or traces left behind from a possible star explosion, the supernova exploded perfectly clean. Additional studies using NASA’s Swift satellite, which examined a large number of more distant Type Ia supernovae, appear to rule out giant stars as companions for the white-dwarf progenitors. When X-ray data was studied, scientists couldn’t find any X-ray point source, indicating that supergiant stars, and even sun-like stars in a later red giant phase, likely aren’t present in the host binaries. Swift’s X-ray Telescope (XRT) has studied more than 200 supernovae to date, of which about 30 percent are Type Ia.

Also, Swift’s Ultraviolet/Optical Telescope (UVOT) looked at 12 Type Ia supernova events within 10 days since their explosion. If the supernova would’ve been triggered by the interaction with larger, brighter stars, then its shock wave should have produced an enhanced ultraviolet light. Nothing of the kind was detected, which combined with other studies findings and X-ray evidence suggests Type Ia supernovae likely originate from a more exotic scenario, possibly the explosive merger of two white dwarfs.

“This is an exciting time in Type Ia supernova research since it brings us closer to solving one of the longest-standing mysteries in the life cycles of stars,” said Raffaella Margutti of the CfA, lead author of the second paper.

The researchers’ findings are set for publishing in April in the journals The Astrophysical Journal Letters and The Astrophysical Journal.

Artist impression of a star getting ripped by a supermassive black hole. (c) Mark A. Garlick, University of Warwick

Intense Gamma Ray blast indeed traced back to supermassive black hole

Artist impression of a star getting ripped by a supermassive black hole. (c) Mark A. Garlick, University of Warwick

Artist impression of a star getting ripped by a supermassive black hole. (c) Mark A. Garlick, University of Warwick

We previously reported about an incredible gamma ray burst triggered by a black hole, so powerful that nothing like this was observed before, or even dimmed possible. A recently published paper in the journal Science sheds more light on the subject.

A typical gamma ray burst commonly occurs when massive stars explode due to collisions with other stars or simple from dying stars – these blasts of radiation usually last around 30 seconds, maybe a few minutes. This super Gamma Ray blast, first observed on 28th of March by the Swift telescope, went on it for days with high levels of radiation, and to this day it still hasn’t stop emitting. Actually, during its first couple of days of activity, the burst registered some wavelengths not visible to the naked eye as bright as a hundred billion suns, scientists report.

“This is probably the first time mankind has seen a phenomenon like this,” says astronomer Josh Bloom of the University of California- Berkeley, lead author of one of two studies on the outburst.

The study brings yet more evidence backing up the theory which say that the center of most big galaxies there’s a supermassive black hole, most of the time quite and dormant.

Swift and other satellites narrowed the origin of the March blast to the center of a galaxy about 22.4 billion trillion miles away or 3.8 billion light-years away, where a titanic black whole, weighing as much as 10 million times more than the sun, gobbled up a star and consumed its whole energy.

In addition, common gamma ray bursts are normally observed at the margin of a galaxy. Sw 1644+57, as the burst was dubbed, however was found in an unusual location – at the core of a galaxy.

“That’s the prime reason we started suspecting early on that a supermassive black hole was involved, because we know [galactic cores are] where these beasts reside.”

What’s remarkable is the game of chance which lead to the observation of this stunning phenomena. As the star was ripped apart by the black hole’s gravity, it was actually trained into a loop around the hole with the speed of light which caused a beam of radiation to spill out of latter’s center core. It took almost 4 billion years and precisely the perfect kind of geometry for the beam to hit Earth and astrophysicists to observe it.

“Seeing a star get ripped apart by a black hole from almost 4 billion light-years away, that’s a remarkable thing,” says astronomer Dave Goldberg, co-author of A User’s Guide to the Universe: Surviving the Perils of Black Holes, Time Paradoxes, and Quantum Uncertainty, who was not part of the studies. “We want to study black holes because they are tremendous natural laboratories for what happens to matter at very high energies.”

Dormant supermassive black holes are still a mystery for scientists, who still can’t unravel its spontaneous nature.

“What’s amazing,” Bloom said, “is that we have here an otherwise quiescent, starving black hole that has decided to go on a sudden feeding frenzy for a short period of time.”

Our galaxy, the Milky Way, seems to have a dormant supermassive black hole at its center as well, and if a Gamma Ray like the one presented earlier were to happen and point towards Earth, it would’ve wreak havoc. Chances something like this would ever happen, scientists assure, are astronomical.

Mysterious cosmic blast triggered by black hole

On the 28th of March the Swift telescope observed a peculiar gamma-ray blast in a distant corner of the visible universe, some 3.8 billion light years away, bewildered astronomers around the world. The powerful blast is theoretically caused, scientists say, by a black hole located in the center of the distant galaxy whose gravity tore apart a massive star which strayed too near. This happens all the time, however, the peculiar phenomena is linked to gamma-ray blast duration.

Typically, a gamma-ray burst last 30 seconds in average, but the one in question has been at it for 11 days now, still glaring. Also, as opposed to the the typical case, this fascinating cosmic blast seems to pulsate light, fading and then sparkling in repetitive intervals.

“It’s either a phenomenon we’ve never seen before or a familiar event that we’ve never viewed in this way before,” says Andrew Fruchter of the Space Telescope Science Institute in Baltimore.

“Tidal disruption of a star by a black hole seems very plausible,” says Andrew MacFadyen of New York University. The blast’s duration “is much longer than anything we’d naturally expect from [explosive] collapse of a single star,” which is the traditional model for producing a gamma-ray burst, he says.