Exo Planets, Sun Eruptions and Black Holes

Credit space.com                                       Exoplanets

The first truly Earth-like alien planet is likely to be spotted next year, an epic discovery that would cause humanity to reassess its place in the universe.
While astronomers have found a number of exoplanets over the last few years that share one or two key traits with our own world — such as size or inferred surface temperature — they have yet to bag a bona fide "alien Earth." But that should change in 2013, scientists say.
"I'm very positive that the first Earth twin will be discovered next year," said Abel Mendez, who runs the Planetary Habitability Laboratory at the University of Puerto Rico at Arecibo.

Eruption on the Sun on New Year's Eve


  

Black Holes

Black holes are some of the strangest and most fascinating objects found in outer space. They are objects of extreme density, with such strong gravitational attraction that even light cannot escape from their grasp if it comes near enough.

How they form

Black holes have been called "frozen stars" because they can form from stars that have died out. A star "dies" if it runs out of fuel for nuclear fusion in its core. Without material to fuse, which creates energy and radiation that push outward, a star will collapse in on itself under the force of gravity.

Artist's concept of the huge black hole at the heart of the galaxy M87, the most massive known black hole to date. Gas swirls around the black hole in an accretion disk. The bright blue jet shooting from the region of the black hole is created by gas that never made it into the hole itself but was instead funneled into an energetic jet.

If the star is massive enough, this inward pull will condense the mass so strongly that even atoms cannot hold their structure, with protons and electrons disintegrating and all the matter collapsing into a tiny ball. If anything comes within a certain range of a black hole, called its event horizon, it cannot escape the black hole's gravitational pull.

Since even light it is no exception, black holes are invisible. However, astronomers can detect the presence of black holes by detecting the radiation that is emitted when matter is pulled in. Sometimes, the areas around black holes release strong jets of high-energy light that can be spotted from across the universe.

According to some theories, Black holes have three main layers: the "outer event horizon" or outer layer, the "inner event horizon" or the middle layer, and the center of the black hole called the "singularity," where the mass is concentrated.

 

The singularity is the name given to the single point in space-time where the mass of a black hole is concentrated. Yet scientists don't truly understand the workings of black holes because our best physics theories break down when trying to describe them.

Black holes involve such large masses, yet tiny spaces, that they invoke two incompatible theories: general relativity and quantum mechanics. The theories describe black holes as having infinite density, though scientists think a more complicated picture will be revealed as new physics is discovered.

 Discovery

Black holes were first predicted in 1916 by Albert Einstein's general theory of relativity.

The first object to be considered a black hole is Cygnus X-1. In 1971, this binary star was observed to emit light that varies in luminosity by the thousandths of a second. This showed that its width spans merely a few kilometers and, therefore, is a compact object. At that time, however, the term "black hole" was not yet used. It was only around 1973 that the term was coined by John Wheeler, an American astronomer.

Since then, many objects have been identified that appear to be black holes. Giant "supermassive" black holes are thought to reside in the centers of most galaxies, including our own Milky Way. Objects have been observed orbiting some extremely massive, invisible object at the center of our galaxy, though astronomers still lack the ability to see this region in enough detail to determine for sure that there lurks a black hole.

Types of black holes

Scientists classify black holes based on their mass, origin, and behavior. Below are the most common types:

• Stellar-mass black holes: These are created when massive stars reach the ends of their lives and run out of fuel, exploding in powerful blasts called supernovas. The left-over material from the explosion collapses into itself and becomes a black hole. A typical stellar-mass black hole contains the mass of about 10 suns.
• Intermediate-mass black holes: These have masses that are comparable to hundreds to millions of suns but their origins are unknown.
• Supermassive black holes: These black holes are likely to be found in the centers of many galaxies. They are thought to form by the mergers of smaller black holes that collide. As more matter falls into them, they can continue to grow over time. Supermassive black holes usually contain the mass of millions or even billions of suns.