martes, 28 de junio de 2011


What did NOT happen

A newly discovered house-sized asteroid missed the Earth by less than 17,700 km (11,000 miles) yesteray, Monday June 27, 2011. That’s about 23 times closer than the Moon. The size and location of the asteroid, named 2011 MD, allowed observers in certain locations to take a look at the space rock, even with small telescopes. It’s closest approach was at 13:26 UTC on June 27.

A few hours before the asteroid's nearest approach, it appeared close to the sun, so observations were possible for only a brief period. Backyard astronomers were able to observe it with telescopes from Australia, southern Africa, and the Americas.
The asteroid was discovered on June 22, 2011, by the Lincoln Near-Earth Asteroid Research (LINEAR) pair of robotic telescopes in New Mexico, and according to rough estimates, the asteroid's length is between 10 and 45 meters (30 and 150 ft).
Emily Baldwin of Astronomy Now said that there was no threat of collision, and should the asteroid enter Earth's atmosphere, it would "mostly burn up in a brilliant fireball, possibly scattering a few meteorites", causing no likely harm to life or property on the ground.

miércoles, 15 de junio de 2011

Lunar eclipse

June 15th, 2011.

The lunar eclipse took place tonight, a central eclipse, with the Moon passing through the center of the Earth's shadow, which made the Moon appear very dark during the umbral (total) phase. Moreover, with the umbral phase lasting 100 minutes, this eclipse is among the longest eclipses that we will be seeing this century! By comparison, the longest lunar eclipse of this century happening on 27th July 2018 will be central and 103 minutes long.

The penumbral phase of the eclipse started at 7:25 PM and partial eclipse started at 8:23 PM. The Moon  lost its bright white color and slowly turned into a reddish/orangish color. Total eclipse began at 12:22 AM. The whole Moon was very dark and appeared a coppery red color for the 1 hour 40 minutes that the total phase lasted. Mid eclipse was reached at 10:13 PM and the eclipse will end at 1:01 AM.

Fortunately, where I live there were clear skies for the whole night. Unlike for solar eclipses, you were able to view it directly with the naked eye. If you are a photographer, send me your pictures and I will upload them here!

There is another lunar eclipse taking place at the end of the year on 10 December 2011. That eclipse starts at 4:34 PM and reaches mid eclipse at 4:32 PM, which doesn't make for as good viewing as the one this month.

Basic space-time explanation

It's hard to understand correctly the concept of space-time. Think of a very large ball. Even though you look at the ball in three space dimensions, the outer surface of the ball has the geometry of a sphere in two dimensions, because there are only two independent directions of motion along the surface. If you were very small and lived on the surface of the ball you might think you weren't on a ball at all, but on a big flat two-dimensional plane. But if you were to carefully measure distances on the sphere, you would discover that you were not living on a flat surface but on the curved surface of a large sphere.
    The idea of the curvature of the surface of the ball can apply to the whole Universe at once. That was the great breakthrough in Einstein's theory of general relativity. Space and time are unified into a single geometric entity called spacetime, and the spacetime has a geometry, spacetime can be curved just like the surface of a large ball is curved.
    When you look at or feel the surface of a large ball as a whole thing, you are experiencing the whole space of a sphere at once. The way mathematicians prefer to define the surface of that sphere is to describe the entire sphere, not just a part of it. One of the tricky aspects of describing a spacetime geometry is that we need to describe the whole of space and the whole of time. That means everywhere and forever at once. Spacetime geometry is the geometry of all space and all time together as one mathematical entity.
I'm preparing an entry about worm holes. I hope it'll be finished by tomorrow.

lunes, 13 de junio de 2011

Black Hole Basic Understanding

Realest black hole picture I could find on the internet

Since the Hubble Space Telescope was launched in 1990, there have been many observations of what are believed to be black holes, including the photograph below of a suspected black hole in the heart of the galaxy NGC 6251. But the subject of black holes began in theoretical physics, long before there were any observations by astronomers.

    The advent of Einstein's General Theory of Relativity gave physicists a mathematical language for describing the gravitational force in a manner consistent with the constant speed of light. Most of what we believe we know about black holes has come from abstract theoretical models in general relativity.
    But in order to observe black holes in Nature we need to know how those abstract theoretical models translate to a Universe filled with other stuff.

In the abstract theoretical model of black holes, a black hole is studied as if it were the only thing in the Universe. Using that approximation, the math of general relativity becomes doable, and we can make predictions about black hole behavior that are useful in understanding the black holes we see. In addition, we learn a lot of things about black holes mathematically that we may never get a chance to witness directly through observation.
    In general relativity, the paths of light can be calculated for many different distributions of matter and energy using equations call the geodesic equations. The geodesic equations give us the paths that would be followed by freely-falling test particles. For example, a baseball after being hit by Sammy Sosa and before being caught by an eager fan would be a freely falling particle, travelling on a geodesic path through spacetime.
    Light travels on geodesics paths through spacetime. When those geodesic paths cross the event horizon of a black hole, they never come back out. Interestingly, in a Universe where the energy density is never negative, this behavior of light leads mathematically to two very crucial properties of black holes:
  • The surface area of the event horizon of a black hole can only increase, never decrease. This also means that although two black holes can join to make a bigger black hole, one black hole can never split in two.
  • The pull of gravity at the event horizon is constant; it has the same value everywhere on the event horizon.
Note that according to the first property, it is impossible for black holes to decay and go away, because a black hole cannot get smaller or split into smaller black holes. This is going to be changed when we add quantum mechanics to the theory. We'll look through that in my next post.

domingo, 12 de junio de 2011

IC1805 - Heart Nebulae

A new mosaic from NASA’s newest infrared observatory captures the Heart and Soul nebulae, so named because of their resemblance to hearts — both the Hallmark-card and the blood-pumping variety.

“One is a Valentine’s Day heart, and the other is a surgical heart that you have in your body,” said Ned Wright of the University of California, Los Angeles, who presented the image May 24 at a meeting of the American Astronomical Society.

Since its launch Dec. 14, 2009, the Wide-Field Infrared Survey Explorer has been circling the Earth in a polar orbit and snapping images every 11 seconds. As of Sunday, it has captured 953,880 frames and mapped about 75 percent of the sky, Wright said.

The new image is stitched together from 1,147 individual frames. The exposure took a total of 3½ hours spread over 11 days in February to complete. The nebulae are located in the constellation Cassiopeia, about 6,000 light-years away from Earth.

The image is color-coded to make sense to human eyes, which are blind in the infrared. Blue and cyan represent the shortest wavelengths WISE is sensitive to — 3.4 and 4.6 micrometers — and highlight places where stars are being born. Green light shows small grains of dust that have been heated by starlight and glow at the 12-micrometer band. The longest wavelength, 22 micrometers, is shown in red, capturing larger dust grains.

The bright spot at the top right of the image is an active star-forming region called W3, which Wright studied with a 4-pixel balloon-borne telescope for his Ph.D. thesis in the 1970s. Wright marveled at the difference between the sketched-out contour map he made then and the glowing portrait captured by WISE.

“It’s been an amazing progress in IR astronomy, with cameras growing by a factor of a million in power in just a few decades,” he said.


V404 Cygni has something of an identity crisis. The "V" in its name indicates that it is a variable star, so it gets brighter and fainter. It's also known as a nova, because at least three times in the 20th century it produced a bright outburst of energy. Finally, it's known as a soft X-ray transient because it periodically emits short bursts of X-rays.
Together, these identities tell astronomers that V404 Cygni is a binary system that consists of a black hole and a "normal" companion star, and that the black hole is stealing hot gas from the companion. The flow of gas between stars isn't even, though, so the system produces occasional "flickers." And when enough gas builds up in a disk around the black hole, there is a much larger outburst that can cause the system to shine hundreds of times brighter than normal.
V404 Cygni's black hole is one of the most solid cases of a stellar-mass black hole in the galaxy. Several careful studies of how the two stars orbit each other show that the "dark" member of the system is probably around 12 times as massive as the Sun. Only a black hole could be that small and heavy.
The companion star is about two-thirds as massive as the Sun. Its surface is cooler, so it shines yellow-orange.
The two stars orbit each other once every 6.5 days, which indicates that they are quite close together. At that range, the black hole's powerful gravity causes the companion to bulge toward it, so the star is egg-shaped. Gas flows from the "point" of the egg toward the black hole.
Most of the time, this flow is fairly thin but steady, although it's clumpy enough that the entire system can appear to flicker a little, which is one reason why it's designated as a variable star.
Gas slowly creates a disk around the black hole, known as an accretion disk. The gas in this disk produces energy, too, adding to the total brightness of the system. However, the disk isn't as bright as a disk around a neutron star. That's because in a neutron-star system, the gas remains visible as it spirals onto the surface of the star. It heats up as it gets closer to the neutron star's surface, so it shines brighter. In a black hole system, though, the gas is swallowed as it crosses the black hole's event horizon, so the system can't shine as brightly.

The process of transferring gas from one star to the other isn't completely smooth, though. There can be "lumps" in the stream, or in the disk around the black hole. These lumps create flares of X-rays that are easily detected by X-ray satellites in space -- hence the label "soft X-ray transient" ("soft" refers to the frequency of the X-rays). The X-rays also light up the gas between the two stars, making the system shine even brighter.
The gas continues to build up around the black hole until it reaches a critical density. The gas then quickly heats up, making the accretion disk shine brighter. Gas in the inner portion of the disk suddenly plunges into the black hole; in the moment before it crosses the event horizon, it shines brightest of all. This "big gulp" produces an outburst of energy not just in X-rays, but in all wavelengths. The system can shine hundreds or thousands of times brighter than normal -- hence the label "nova."
V404 Cygni first jumped to prominence during a nova eruption in 1938. It produced eruption in 1989, which was discovered by an orbiting X-ray satellite and confirmed by telescopes on the ground. The system grew about 200 times brighter in visible wavelengths, and much more than that in X-rays. The system is likely building toward another eruption, although so far, astronomers don't know when to expect it.

lunes, 6 de junio de 2011


I'm going to start this blog talking about my favorite quasar, OJ287. Quoting from
It's hard to think of a black hole that's a hundred million times as massive as the Sun as little. But in a distant quasar known as OJ 287, that may be the case. According to a team of astronomers that studied the system, the black hole appears to orbit another black hole that's the most massive yet discovered -- 18 billion times the mass of the Sun.A quasar is a small object that can outshine an entire galaxy of normal stars. It's probably powered by a disk of superhot gas spiraling around a supermassive black hole.Astronomers have been watching OJ 287 for more than a century. It's about three and a half billion light-years away, and it looks like a faint, fuzzy galaxy. But twice every 12 years, it flares up. Each outburst lasts a few days.Although many astronomers are skeptical, an international team says the flareups and other evidence suggest that the system consists of two giant black holes. The smaller one orbits its bigger cousin once every 12 years. Its orbit is stretched out, and it's tilted. So twice during each orbit, it passes through the hot gas surrounding the bigger black hole, causing the flareups.The team tested this model last year. It predicted that a flareup would occur on September 13th -- and it came right on cue, bolstering the model of how OJ 287 works. The same team of astronomers will be looking for more evidence when the next outburst is due -- in about eight years."

As you can see, OJ287 is a very interesting quasar. The black hole is about six times as massive as the previous record holder and in fact weighs as much as a small galaxy. It lurks 3.5 billion light years away, and forms the heart of a quasar called OJ287. A quasar is an extremely bright object in which matter spiralling into a giant black hole emits copious amounts of radiation.But rather than hosting just a single colossal black hole, the quasar appears to harbour two - a setup that has allowed astronomers to accurately 'weigh' the larger one.The smaller black hole, which weighs about 100 million Suns, orbits the larger one on an oval-shaped path every 12 years. It comes close enough to punch through the disc of matter surrounding the larger black hole twice each orbit, causing a pair of outbursts that make OJ287 suddenly brighten. General relativity predicts that the smaller hole's orbit itself should rotate, or precess, over time, so that the point at which it comes nearest its neighbour moves around in space - an effect seen in Mercury's orbit around the Sun, albeit on a smaller scale.