Posts Tagged ‘supernova’

Gamma-Ray Burst from WR 104?

Thursday, May 30th, 2013

Wow, a gamma-ray burst from a star 8,000 light years away could trash our atmosphere in seconds. It could happen today — or 500,000 years from now. That’s worse than the cable guy’s estimate.

I’m not changing my plans.

However, there are a bunch of astronomers who are working on the estimate in Australia and Hawaii. Bruce Dorminey’s piece in Forbes the other day puts all the details together:

Although WR 104, a Wolf-Rayet star some 8000 light years distant, has thus far remained largely quiescent, it is ripe to undergo a core-collapse supernova of the sort that could generate a seconds-long burst of gamma-rays that, in turn, might potentially wipe out a quarter of earth’s protective atmospheric ozone.

“We could see it go supernova anywhere from tomorrow to 500,000 years from now,” said Grant Hill, an astronomer at the W.M. Keck Observatory in Hawaii. “For all intents and purposes, the gamma-ray burst and optical photons from the supernova would arrive simultaneously.”

Later in the article, physicist Adrian Melott used the term “extinction event” — HULK NO LIKE THAT.

Big Bang Monday: Supernova Remnants

Monday, February 6th, 2012

After a very nice Super Bowl yesterday, those of us who spent the time watching eating and drinking massive quantities of stuff we shouldn’t, may be dealing with remnants on another kind of bowl.

How appropriate that today’s Image of the Day from NASA is “Remnant of A Supernova” (G350.1+0.3)…

Vital clues about the devastating ends to the lives of massive stars can be found by studying the aftermath of their explosions. In its more than twelve years of science operations, NASA’s Chandra X-ray Observatory has studied many of these supernova remnants sprinkled across the galaxy.

The latest example of this important investigation is Chandra’s new image of the supernova remnant known as G350.1+0.3. This stellar debris field is located some 14,700 light years from the Earth toward the center of the Milky Way.

Evidence from Chandra and from ESA’s XMM-Newton telescope suggest that a compact object within G350.1+0.3 may be the dense core of the star that exploded. The position of this likely neutron star, seen by the arrow pointing to “neutron star” in the inset image, is well away from the center of the X-ray emission. If the supernova explosion occurred near the center of the X-ray emission then the neutron star must have received a powerful kick in the supernova explosion.

Data suggest this supernova remnant, as it appears in the image, is 600 and 1,200 years old. If the estimated location of the explosion is correct, this means the neutron star has been moving at a speed of at least 3 million miles per hour since the explosion.

Another intriguing aspect of G350.1+0.3 is its unusual shape. Many supernova remnants are nearly circular, but G350.1+0.3 is strikingly asymmetrical as seen in the Chandra data in this image (gold). Infrared data from NASA’s Spitzer Space Telescope (light blue) also trace the morphology found by Chandra. Astronomers think that this bizarre shape is due to stellar debris field expanding into a nearby cloud of cold molecular gas.

The age of 600-1,200 years puts the explosion that created G350.1+0.3 in the same time frame as other famous supernovas that formed the Crab and SN 1006 supernova remnants. However, it is unlikely that anyone on Earth would have seen the explosion because of the obscuring gas and dust that lies along our line of sight to the remnant.

These results appeared in the April 10, 2011 issue of The Astrophysical Journal.

Image Credits: X-ray: NASA/CXC/SAO/I. Lovchinsky et al; IR: NASA/JPL-Caltech

The description references the “Crab Nebula” — get your prints here.

Colliding White Dwarfs

Thursday, April 7th, 2011

From the Monthly Notices of the Royal Astronomical Society, we read about two white dwarf stars that will combine to form a helium-burning star — in roughly 37,000,000 years. Get a load of this abstract

We identify SDSS J010657.39-100003.3 (hereafter J0106-1000) as the shortest period detached binary white dwarf (WD) system currently known. We targeted J0106-1000 as part of our radial velocity program to search for companions around known extremely low-mass (ELM, ~ 0.2 Msol) WDs using the 6.5m MMT. We detect peak-to-peak radial velocity variations of 740 km/s with an orbital period of 39.1 min. The mass function and optical photometry rule out a main-sequence star companion. Follow-up high-speed photometric observations obtained at the McDonald 2.1m telescope reveal ellipsoidal variations from the distorted primary but no eclipses. This is the first example of a tidally distorted WD. Modeling the lightcurve, we constrain the inclination angle of the system to be 67 +- 13 deg. J0106-1000 contains a pair of WDs (0.17 Msol primary + 0.43 Msol invisible secondary) at a separation of 0.32 Rsol. The two WDs will merge in 37 Myr and most likely form a core He-burning single subdwarf star. J0106-1000 is the shortest timescale merger system currently known. The gravitational wave strain from J0106-1000 is at the detection limit of the Laser Interferometer Space Antenna (LISA). However, accurate ephemeris and orbital period measurements may enable LISA to detect J0106-1000 above the Galactic background noise.

For a translation, let’s turn to the Smithsonian’s Christine Pulliam

Out of the 100 billion stars in the Milky Way, only a handful of merging white dwarf systems are known to exist. Most were found by Kilic and his colleagues. The latest discovery will be the first of the group to merge and be reborn.

The newly identified binary star (designated SDSS J010657.39 – 100003.3) is located about 7,800 light-years away in the constellation Cetus. It consists of two white dwarfs, a visible star and an unseen companion whose presence is betrayed by the visible star’s motion around it. The visible white dwarf weighs about 17 percent as much as the Sun, while the second white dwarf weighs 43 per cent as much. Astronomers believe that both are made of helium.

The two white dwarfs orbit each other at a distance of 140,000 miles – less than the distance from the Earth to the Moon. They whirl around at speeds of 270 miles per second (1 million miles per hour), completing one orbit in only 39 minutes.

The fate of these stars is already sealed. Because they wheel around so close to each other, the white dwarfs stir the space-time continuum, creating expanding ripples known as gravitational waves. Those waves carry away orbital energy, causing the stars to spiral closer and closer together. In about 37 million years, they will collide and merge.

When some white dwarfs collide, they explode as a supernova. However, to explode the two combined have to weigh 40 percent more than our Sun. This white dwarf pair isn’t heavy enough to go supernova. Instead, they will experience a second life. The merged remnant will begin fusing helium and shine like a normal star once more.

This binary white dwarf was discovered as part of a survey program being conducted with the MMT Observatory on Mount Hopkins, Ariz. The survey has uncovered a dozen previously unknown white dwarf pairs. Half of those are merging and might explode as supernovae in the astronomically near future.

Yeah, there’s a video…