A Super-Supernova? Can You Say Hypernova?

I recently saw a show on the Discover Channel about a cosmic phenomenon I had not heard of before called a hypernova. I was just flipping through the channels, but when I came across this show I had to keep watching. You think a supernova is pretty powerful, it’s nothing compared to a hypernova.

A possible hypernova in the making, Eta Carinae is amazingly, almost impossibly bright, shining 4 million times brighter than our sun. It is also wildly unstable, prone to huge flares, outbursts and dizzying swings in brightness that make it look as if it’s on the verge of self-destruction. Although it’s 7,500 light years away, it could still pose a threat to Earth should it explode. We humans will most likely be okay, the threat would most likely be to satellites and the upper atmosphere.

Hypernova are formed only by incredibly heavy and fast burning stars. When a star that’s at least 40 times more massive than our sun exhausts its nuclear fuel, it will collapse into a black hole, ejecting twin plasma jets at almost the speed of light – going hypernova. A hypernova is the most energetic event in the universe, converting chunks of matter the size of our sun into electromagnetic radiation almost instantly. A typical star may live for ten billion years or more, but one that will become a hypernova will collapse in around one million. To burn this quickly they need a huge amount of fuel. The stars find this in what are called stellar nurseries; huge clouds of gas that combine to form new stars.

A typical supernova is very energetic; it can shine as bright as its host galaxy for weeks or even months. Hypernova on the other hand are extremely rare, occurring only five times every million years in our galaxy, and a great deal more powerful, up to 100 times more powerful than a supernova. A hypernova could be called a super-supernova that at its peak will outshine the entire galaxy. It was recently discovered that hypernovae are the source of previously mysterious gamma-ray bursts.

A great article on this can be found over at Science Daily. http://www.sciencedaily.com/releases/2003/04/030407075127.htm

A First! - NASA Telescope Sees Black Hole Munch On a Star - From Beginning to End

News Release From GALEX - The Galaxy Evolution Explorer
A giant black hole has been caught red-handed dipping into a cosmic cookie jar of stars by NASA's Galaxy Evolution Explorer. This is the first time astronomers have seen the whole process of a black hole eating a star, from its first to nearly final bites.

"This type of event is very rare, so we are lucky to study the entire process from beginning to end," said Dr. Suvi Gezari of the California Institute of Technology, Pasadena, Calif. Gezari is lead author of a new paper appearing in the Dec. 10 issue of Astrophysical Journal Letters.

For perhaps thousands of years, the black hole rested quietly deep inside an unnamed elliptical galaxy. But then a star ventured a little too close to the sleeping black hole and was torn to shreds by the force of its gravity. Part of the shredded star swirled around the black hole, then began to plunge into it, triggering a bright ultraviolet flare that the Galaxy Evolution Explorer was able to detect.

This artist's concept shows a supermassive black hole at the center of a remote galaxy digesting the remnants of a star. NASA's Galaxy Evolution Explorer had a "ringside" seat for this feeding frenzy, using its ultraviolet eyes to study the process from beginning to end.

The artist's concept chronicles the star being ripped apart and swallowed by the cosmic beast over time. First, the intact sun-like star (left) ventures too close to the black hole, and its own self-gravity is overwhelmed by the black hole's gravity. The star then stretches apart (middle yellow blob) and eventually breaks into stellar crumbs, some of which swirl into the black hole (cloudy ring at right). This doomed material heats up and radiates light, including ultraviolet light, before disappearing forever into the black hole. The Galaxy Evolution Explorer was able to watch this process unfold by observing changes in ultraviolet light. The area around the black hole appears warped because the gravity of the black hole acts like a lens, twisting and distorting light.

Read the complete release text here.

Image credit: NASA/JPL-Caltech/Tim Pyle (SSC)
Text credit: Whitney Clavin (JPL)

Hybrid Gamma Rays – Scientists Discover New Type Of Gamma Ray Bursts

Recently scientists made a discovery that has forced them to re-think their theories on gamma ray bursts – the most powerful explosions in the cosmos.

Gamma ray bursts signal the birth of black holes. Scientists thought they had figured the nature of gamma ray bursts a year ago, and had classified the bursts into two categories: long or short. The long bursts are those that last more than two seconds. It is believed that they are ejected by massive stars at the furthest edge of the universe as they collapse to form black holes. Short bursts persist for less than two seconds, with some only lasting a few milliseconds. The cause is thought to be the merger of two neutron stars – or a neutron star and a black hole – to form a new or bigger black hole. This newly discovered hybrid gamma ray burst has properties of both known classes but also possesses features that remain unexplained.

X-ray image of the gamma-ray burst GRB 060614 taken by the XRT instrument on Swift. The burst glowed in X-ray light for more than a week following the gamma-ray burst. This so-called "afterglow" gave an accurate position of the burst on the sky and enabled the deep optical observations made by ground-based observatories and the Hubble Space Telescope. Credit: NASA/Swift Team

This hybrid burst came from the constellation Indus, which is 1.6 billion light years away. The evidence suggests that the black hole birth happened in a very different way than from other known bursts. The hybrid lasted for 102 seconds, making it a long burst, but long bursts are normally associated with a supernova (star explosion). This one, labeled GRB 060614 had no associated supernova. It is in fact, in a galaxy with very few stars that could produce either a supernova or a long burst.

This information is based on a press release form NASA, for more information follow this link to the press release.

Galactic Cannibalism: Our Milky Way Galaxy Has The Munchies

This beautiful, eerie silhouette of dark dust clouds against the glowing nucleus of the elliptical galaxy NGC 1316 may represent the aftermath of a 100 million year old cosmic collision between the elliptical and a smaller companion galaxy.

It appears our Milky Way galaxy has a large appetite, galactic cannibalism is the term given to the process by which a large galaxy, through tidal gravitational interactions with a companion galaxy, merges with that companion, resulting in a larger galaxy. A technical way of saying the big fish eats the little fish.

The current thinking on the formation of galaxies implies that dwarf galaxies were the first to form in the universe. Many of these first dwarf galaxies either went on to clump together to form larger galaxies, or were eventually gobbled up by larger galaxies that continued to grow in this fashion.

Solid observational proof of galactic cannibalism was just on the horizon in 1994 when a new dwarf galaxy, Sagittarius, was discovered very close to the Milky Way and located on the diametrically opposite side of the galactic center from the sun.

It had been suspected for some time that the Milky Way had grown to it’s current size by devouring smaller galaxies, with the discovery of Sagittarius some observational evidence supporting this notion had been found. Now it would be possible to directly view the destruction of a dwarf galaxy as it is being engulfed by the Milky Way galaxy. All that was needed to be done was to find stars that had originally formed part of the dwarf galaxy, but would now be strewn along its entire orbit around the Milky Way. This would constitute two streams encircling the Milky Way. The only problem with this is that the streams would be extremely diffuse and may therefore be completely indistinguishable.

In 1998, investigators from the University of Michigan found the remains of one of the streams that extended to the southwest. These remnants are the furthest from the center of a progenitor galaxy ever detected and confirm that the Sagittarius galaxy has formed an arc that completely surrounds our galaxy, just as predicted by theoretical models. This discovery proves not only that Sagittarius is in an advanced stage of destruction but also - more importantly that the process we call cannibalism has played and continues to play an important role in the formation of the Milky Way.

BLACK HOLES THREE: The Ever Changing Mystery – Black Hole Pioneer Stephen Hawking Admits Mistake

Since the 1970’s when Stephen Hawking pioneered black hole theory, he has maintained that when an object falls into a black hole, no information can escape, it is lost forever. Hawking's view at that time and up to recently (2004) follows Einstein’s general theory of relativity.

Relativity predicts that at certain locations in space, matter collapses into an infinitely small and dense point, called a singularity. The force of gravity at this point is so great that nothing, not even light can escape, the reason for the name ‘black hole’.

Because the singularity is so small (infinitely small), it cannot have any structure, therefore it cannot hold information. Any data about particles entering a black hole will be lost forever.

Unfortunately quantum physics does not agree with this prediction of general relativity. Quantum theory says that any process can be run in reverse, therefore starting conditions can in theory be inferred from the end products alone. The implication is obvious – a black hole must somehow store information about the objects that fell into it – even if we can never access that information.

In 2004 Hawking changed his position, he now believes that information is stored and can escape a black hole. This reversal of position is the result of Hawking’s attempt to combine quantum theory with general relativity, in a powerful theory of quantum gravity. He used a mathematical technique called the “Euclidean path integral”. This is a very complex technique that lumps all the possible histories of a system into one equation. This mathematical technique was first used by Richard Feynman (one of my favorite physicists) and is generally applied to subatomic particles. Hawking has been steadily working for years on applying it to black holes. "The view seems to be forming in his mind that there isn't a black hole in the absolute sense, there's just a region where things take a very long time to escape," says Hawking's Cambridge University colleague Gary Gibbons. This implies that black holes do not actually narrow to a singularity at all.

This means that an object entering a black hole is not completely destroyed. Instead, the black hole is altered as it absorbs the object. Even though it would almost certainly be impossible to access and information about the object, the data is still there – inside the black hole.

One may ask how information can possibly ever escape a black hole. To answer that we need to look at one of Hawking’s greatest discoveries – black holes slowly evaporate into space by losing particles at the edge of the event horizon, this is called Hawking radiation. Eventually the black hole will shrink to the size of a tiny kernel, at which point a growing torrent of radiation starts to leak out, possibly carrying the lost information with it.

It is unlikely that this change in position will be embraced by the scientific community, Preskill says that Hawking’s new position on quantum gravity rests on shaky mathematical foundations, “I am skeptical about whether he has found a fully satisfactory resolution to the problem,” he says. Only time will tell.

This about face by Hawking means he loses a long-standing bet with John Preskill, a theoretical physicist at the California Institute of Technology. In the bet Hawking maintained that anything gobbled up by a black hole was forever hidden from the outside universe. Preskill bet that the information carried by an object was not destroyed when it falls into a black hole; the information could actually be recovered. "Stephen has changed his position, and I am expecting him to concede the bet," Preskill says. His prize is to be an encyclopedia, "from which information can be recovered at will". After Hawking admitted he had been wrong, his original offer of a cricket encyclopedia was turned down in favor of “Total Baseball: The Ultimate Baseball Encyclopedia”. Preskill told the assembled media he had always hoped there would be witnesses when Hawking conceded, but “this really exceeds my expectations.”

BLACK HOLES TWO: Laws of Physics Need Not Apply Inside

In the previous post I covered black holes in general, the origin of the idea and a brief explanation of what they are. Now let’s take a look at some of the unusual rules that operate inside the event horizon.

So we have crossed the event horizon and now neither we nor any light can escape back to the outside, the singularity that lies at the center of the black hole is now in our future and there is no way to avoid crashing into it. As you can see the horizon has some very unusual geometrical properties. If you were an observer sitting far away from the black hole, the event horizon would seem to be a very nice, static and unmoving spherical surface (originally called “frozen stars” for this property, since no light escapes). As you got closer and closer you would find that it has a very high velocity. Actually you would see that it’s moving outward at the speed of light! This is why it would be so easy to fall into a black hole, but impossible to ever get back out. Since the event horizon is moving outward at the speed of light, you would have to be able to travel faster than the speed of light to escape, which is a violation of Einstein’s relativity.

On the one hand, the horizon is sitting still, while on the other it’s actually moving outward at the speed of light. Sounds contradictory, but its true, let’s look at the unusual rules that apply inside an event horizon. Once on the inside, space-time is distorted to such a high degree that the coordinates describing radial distance and time switch roles. What that means is the coordinate that normally describes how far you are from the center (“r” radial distance) now becomes a time coordinate, and the coordinate that normally describes time (“t” time) becomes a space-like coordinate. One result of this is you cannot stop yourself from moving to smaller and smaller values of “r”, just as in normal life you cannot avoid moving toward the future. Eventually you will hit the singularity where “r” = 0. Trying to avoid the singularity is like trying to avoid tomorrow. Just how strong is the gravitational pull inside a black hole? The further in you go, the stronger the pull is. It’s so strong that if your feet were closer to the center than your head, the difference in pull between your head and your feet (tidal forces) would literally pull you apart in a horrendous fashion known as spaghettification.

Now lets see how all of this looks to an outside observer who is watching someone else enter a black hole. There are two space travelers, one is stationed very far away from the black hole, and the other is you poised just outside of the event horizon. As you start to move toward the event horizon, the other astronaut sees you move more and more slowly. No matter how long the observer waits he or she will never see you reach the event horizon and it would appear to him/her that it takes an infinite amount of time for you to enter the black hole. The reason for this is simple, the closer you get to the event horizon, the longer it takes for the light you are emitting to climb back out and escape. Actually, the light you emit just as you cross the event horizon will hover right there at the horizon forever and ever never reaching the observer. From the observers point of view you will have frozen in space.

Keeping with the fact that massive objects distort the space-time around them, time near the event horizon really does move more slowly. If you were able to get very close to the event horizon, but managed to keep from being pulled in, you would find when you returned to talk to the observing space traveler that he or she has aged much more than you have. Time has passed more slowly for you than it did for the rest of the universe.