(Source: astrodidact)
I'm just this guy with a quest for perspective and a very random blog.
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About the blog. About the blogger. Music I enjoy. Ask me anything. Share with me.
March 4, 2013
February 12, 2013
‘Magic’ telescope will explore black holes
Two eyes are better than one, especially when it comes to visualising dark matter and disproving certain tenets of the theory of relativity. So it was with some excitement that scientists announced that a second parabolic telescope will soon be hard at work trying to solve the mystery of black holes.
Magic II, due to be unveiled on the island of La Palma in the Canaries on April 25, has been developed by the University of Padua, Italy. It will feature the largest reflective surface in the world and be able to reach unprecedented distances.
Once operational, the telescope will begin working alongside its predecessor, Magic I. Using both telescopes together, scientists will be able to see high-energy gamma rays that were previously invisible.
The “Magic” (Major Atmospheric Gamma-ray Imaging Cherenkov) experiment will take place on top of an extinct volcano at an altitude of 2,200 meters, free from light pollution and atmospheric dust. Both telescopes have a mirror surface of 234 square metres and a diameter of 17 meters, but the newly built Magic II will improve the resolution and sensitivity of the system.
The data will be analysed by 150 physicists from all over the world, and provide better insight into the processes that generate energy within galaxies and stars, researchers say.
“By the end of the five-year-long project we should have a map of the universe,” says Alessandro De Angelis, who leads the experiment for Italy’s National Institute of Nuclear Physics (INFN). “We’ll put together a picture of black holes that are as far as six billion light years away from our planet. We’ll be able to see what happens when they evolve.”
Mosè Mariotti, of Padua University, said the telescope would be able to disprove the theory that the speed of light in a vacuum is always the same, and would allow scientists to “witness the annihilation of dark matter”.
He acknowledges that for the moment the studies have yielded few results, but says that he remains optimistic. “It’d be surprising not to find anything new from gazing at such a remote and wide region of the universe, around four to eight million light years away.”
We’ll keep our fingers crossed then.
(via someassemblyrequiredd)
February 10, 2013
No Escape: Dive Into a Black Hole
When matter is compressed beyond a certain density, a black hole is created. It is called black because no light can escape from it. Some black holes are the tombstones of what were once massive stars. An enormous black hole is thought to lurk at the center of the Milky Way galaxy.
All the mass of a black hole is concentrated into a point at its center called the singularity. Gravity surrounding the singularity is so strong, you would have to travel faster than light to escape. This creates a spherical zone surrounding the singularity called the event horizon from which nothing can escape.
At about one and a half times the diameter of the event horizon, photons become trapped in circular orbits around the black hole.
All the mass of a black hole is concentrated into a point at its center called the singularity. Gravity surrounding the singularity is so strong, you would have to travel faster than light to escape. This creates a spherical zone surrounding the singularity called the event horizon from which nothing can escape.
In theory, a black hole of any size could exist. A black hole with the mass of our sun would be 3.7 miles (6 km) in diameter. In practice, the death of a star like the sun does not compress the material enough to form a black hole. Stars with about two times the sun’s mass or more form black holes. Astronomers recognize two major types. [The Strangest Black Holes in the Universe]
Stellar-mass black holes have the mass of several sun-sized stars. They form when a dying star explodes in a supernova, then collapses under its own gravity. Matter drawn toward the black hole forms an accretion disc.
Supermassive black holes can have billions of times our sun’s mass. Matter drawn toward a supermassive black hole is compressed, heats up and may be blasted out into jets thousands of light-years long.
Stellar-mass black holes are scattered throughout the galaxy. A supermassive black hole lies at the core of many galaxies, including our own. The Milky Way’s supermassive black hole is called SgrA* (Sagittarius A-star), and it is seen from Earth in the constellation Sagittarius. The supermassive black hole is about 26,000 light-years away, and has a mass of at least 4 million times the mass of our sun.
The powerful gravity of a black hole distorts light, space and time. One effect is gravitational lensing. A black hole between us and a distant galaxy will bend the rays of light, causing our view of the galaxy to be warped. We have yet to photograph a black hole in detail, but simulations suggest that the supermassive black hole at the Milky Way’s center might appear to be a distorted crescent.
Credit: Space.com
(via someassemblyrequiredd)
February 9, 2013
Pulsars
Ever look up at a clear night sky and notice some of the stars blink a bit more than others? They dwindle and fade in and out at different rates, almost making the skies look like sparkling water. What you are looking at most of the time is actual stars that are making their way to the end of their life. The moment prior to their eventual death
But to understand what a Pulsar is you need to Understand what Neutron stars are as well. Neutron stars are one of the possible ends for a star. They result from massive stars which have mass greater than 4 to 8 times that of our Sun. After these stars have finished burning their nuclear fuel, they undergo a supernova explosion. This explosion blows off the outer layers of a star into a beautiful supernova remnant. The central region of the star collapses under gravity. It collapses so much that protons and electrons combine to form neutrons. Hence the name “neutron star”.
Simply put, pulsars are rotating neutron stars. And pulsars appear to pulse because they rotate, Like shown in the figures below & above.
Pulsars are spinning neutron stars that have jets of particles moving almost at the speed of light streaming out above their magnetic poles. These jets produce very powerful beams of light. In addition, since stars variate in energy output, every single pulsar in the night sky is unique and has it’s own “pulsating” beacon. Kind of the same way species here on Earth have variations of the beating heart.
Information Via: NASA
February 7, 2013
Astronomers have discovered a huge formation of 73 quasars representing the largest structure yet observed in the universe.
The quasar group is very distant, and therefore existed when the universe was much younger than it is now. A quasar is a very energetic black-hole-powered galactic nucleus. Quasars first appeared in the very early universe, soon after the Big Bang. The light from a quasar is so intense that it can be visible from across the universe.
A remarkable thing about the new discovery is that the structure is larger than cosmological theory says is possible.
The currently accepted Cosmological Principle, based on the work of Albert Einstein, suggests that the largest structures we should be able to find would be about 370 megaparsecs across (more than 1.2 billion light-years). The newly found quasar group is 1,200 megaparsecs across, a distance that would take four billion years to cross at the speed of light.
The largest structures that we know that are close to Earth are super clusters of galaxies surrounding vast voids in space. The Sloan Great Wall is the largest such structure and is at the top end of the size limit set by the Cosmological Principle.
(via astrodidact)
February 2, 2013
Anatomy of Brown Dwarf’s Atmosphere
This artist’s illustration shows the atmosphere of a brown dwarf called 2MASSJ22282889-431026, which was observed simultaneously by NASA’s Spitzer and Hubble space telescopes. The results were unexpected, revealing offset layers of material as indicated in the diagram. For example, the large, bright patch in the outer layer has shifted to the right in the inner layer. The observations indicate this brown dwarf — a ball of gas that “failed” to become a star — is marked by wind-driven, planet-size clouds.
The observations were made using different wavelength of light: Hubble sees infrared light from deeper in the object, while Spitzer sees longer-wavelength infrared light from the outermost surface. Both telescopes watched the brown dwarf as it rotated every 1.4 hours, changing in brightness as brighter or darker patches turned into the visible hemisphere. At each observed wavelength, the timing of the changes in brightness was offset, or out of phase, indicating the shifting layers of material.
(via thescienceofreality)
January 8, 2013
January 7, 2013
Solar Eruption
[Image Credit: NASA/SDO]
“A solar eruption gracefully rose up from the sun on Dec. 31, 2012, twisting and turning. Magnetic forces drove the flow of plasma, but without sufficient force to overcome the sun’s gravity much of the plasma fell back into the sun.
The length of the eruption extends about 160,000 miles out from the Sun. With Earth about 7,900 miles in diameter, this relatively minor eruption is about 20 times the diameter of our planet.”
[See video and relative size of Earth to eruption on ‘Solar Ballet on the Sun’ feature.]
December 25, 2012
The Nearest Stars To Earth (Infographic)
Of all the stars closer than 15 light-years, only two are spectral type G, similar to our sun: Alpha Centauri A and Tau Ceti. The majority are M-type red dwarf stars.
Only nine of the stars in this area are bright enough to be seen by the naked human eye from Earth. These brightest stars include Alpha Centauri A and B, Sirius A, Epsilon Eridani, Procyon, 61 Cygni A and B, Epsilon Indi A and Tau Ceti.
Barnard’s Star, a red dwarf 5.96 light-years away, has the largest proper motion of any known star. This means that Barnard’s Star moves rapidly against the background of more distant stars, at a rate of 10.3 seconds of arc per Earth year.
Sirius A is the brightest star in Earth’s night sky, due to its intrinsic brightness and its proximity to us. Sirius B, a white dwarf star, is smaller than Earth but has a mass 98 percent that of our sun.
In late 2012, astronomers discovered that Tau Ceti may host five planets including one within the star’s habitable zone. Tau Ceti is the nearest single G-type star like our sun (although the Alpha Centauri triple-star system also hosts a G-type star and is much closer).
The masses of Tau Ceti’s planets range from between two and six times the mass of Earth.
(via astrodidact)
December 11, 2012
When the word first got out that the expansion of the universe was accelerating, many astronomers questioned the results. They felt that the observations must be wrong, or the interpretation must be flawed. The whole concept was so difficult to believe because it requires significant changes in our understanding of the way the universe works.
Say you step outside and throw a baseball up into the air. The gravity of Earth begins immediately to act on the baseball, slowing it down even as it rises into the air. The upward speed of the baseball slows until it stops at its peak, then gravity’s pull causes it to drop down at an ever-increasing speed. What you can’t see is that the baseball also has a tiny gravitational pull that acts upon Earth. Gravity always acts to pull matter together.
Now consider a spaceship. If launched with enough speed, a spaceship will escape Earth’s gravity to the extent that it will not fall back to the planet. However, it hasn’t escaped the pull of Earth entirely. Though it travels away, the spaceship will be continuously slowed — just not to the point where it stops.
COMPETING MODELS
These same concepts apply to the expansion of space. That expansion was launched in the Big Bang, and ever since then, each bit of matter in the universe has been attracted to every other bit by the force of gravity. This should have been slowing down the expansion.
Before the discovery of dark energy, scientists had two models of how the universe’s expansion would work. In one scenario, there would be enough matter in the universe to slow the expansion to the point where, like the baseball, it would come to a halt and start to retract, everything crashing back together in a “Big Crunch.”
In the other scenario, there would be too little matter to stop the expansion and everything would drift on forever, always slowing and slowing but never stopping — like the spaceship. The galaxies would drift apart from each other until they were out of view. The universe would continue growing larger (infinite expansion) as countless generations of stars faded and died out. It would end in a vast, dark, and cold state: a “Big Chill,” if you will.
DOES THE MATTER MATTER
By the early 1990s, astronomers had calculated how much mass was in the universe, and decided on the Big Chill as the most likely end of the universe. But then dark energy showed up in our observations.
According to the Big Chill, the universe should be expanding more slowly today than it did in the past, because gravity has had time to work on slowing the universe down over all these billions of years. But astronomers found that the universe is moving faster today than it was a billion years ago, meaning something must be working to speed it up.
This result seems crazy because gravity always pulls and slows — it never pushes. Yet some force appears to be pushing the universe apart. Astronomers, concluding that we just don’t know what this force is, have attributed it to a mysterious dark energy.
THE BIG RIP
With dark energy, the fate of the universe might go well beyond the Big Chill. In the strangest and most speculative scenario, as the universe expands ever faster, all of gravity’s work will be undone. Clusters of galaxies will disband and separate. Then galaxies themselves will be torn apart. The solar system, stars, planets, and even molecules and atoms could be shredded by the ever-faster expansion. The universe that was born in a violent expansion could end with an even more violent expansion called the Big Rip.
So out of the three scenarios for the fate of the universe — re-collapse to a Big Crunch, expand ever more slowly to a Big Chill, or expand ever faster to a Big Rip — we have managed to narrow the possibilities down somewhat.
Evidence has ruled out the Big Crunch. The Big Chill is probably the least that will happen. Whether or not the universe goes all the way to a Big Rip depends on what dark energy really is, and whether it will stay constant forever or fade away as suddenly as it appears to have arisen. And that we do not yet know.
No matter which scenario is right, the universe still has at least a few tens of billions of years left — which leaves us plenty of time to look for the answers.
Source: hubblesite.org Image credit: NASA/ESA and A. Riess (STScI)
(via astrodidact)
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