Sunday, May 16, 2010

Why are Distant Galaxies Moving Away Faster?

Question: Why are more distant galaxies moving away faster?
Answer: As you know, the Universe is expandingafter the Big Bang. That means that every part of the Universe was once crammed into a tiny spot smaller than a grain of sand. Then it began expanding, and here we are, 13.7 billion years later with a growing Universe.
The expansive force of dark energy is actually accelerating the expansion even faster. But we won't bring that in to make things even more complex.
As we look out into the Universe, we see galaxies moving away from us faster and faster. The more distant a galaxy is, the more quickly it's moving away.
To understand why this is happening, go and get a balloon (or blow one up in your mind). Once you've got it blown up a little, draw a bunch of dots on the surface of the balloon; some close and others much further away. Then blow up the balloon more and watch how the dots expand away from each other.
From the perspective of any one dot on the surface of the balloon, the nearby dots aren't expanding away too quickly, maybe just a few centimeters. But the dots on the other side of the balloon are quite far away. It took the same amount of time for all the dots to change their positions, so the more distant dots appeared to be moving faster.
That's how it works with the Universe. Because space itself is expanding, the more further a galaxy is, the faster it seems to be receding.

Ouestion and Answer --
Question: What is on the other side of a black hole?
Answer: There is no other side.
Science fiction has populated the idea that a black hole serves a portal to another world. If you could pass through, where does a black hole go? Perhaps you'll come to some other dimension, or re-emerge from some other part of the Universe?
No, a black hole only leads to death, for you, your spaceship, and another else that's unlucky enough to fall in.
Imagine you fell into a star like our Sun, there would be no question what would happen to you. The intense heat, gravity and pressure would kill you. If you compress more than 5x themass of the Sun into a tight little area, you get a black hole. But the gravity, heat and pressure are all still there, just much more intense.
If you actually fell into a black hole, the tidal forces pulling at you are so extreme that the force on your feet is dramatically stronger than the force at your head. You would be stretched out and torn into pieces, and then those pieces would be torn into pieces. You would eventually be pulled into a stream of atoms, winding their way down to the surface of the black hole. For this process, scientists have a technical term: spaghettification.
Let's say you could survive this journey. Where does the black hole lead? No where. All of the mass of the star that came before the black hole is still there, pulling at you with all its gravity. This intense gravity would tear every molecule apart, and all the atoms. Protons and electrons would be crushed together to create neutrons, and then these would be crushed together even further into some kind of exotic form of superdense matter.
It's even possible that the heart of a black hole is single point of infinitely small size, containing the mass of many stars. This black hole is not a portal to anywhere, it's just a final destination.
Here's an article I did about how to maximize your time while falling into a black hole.

Saturday, May 15, 2010

Hubble, Renewed, Reinvigorated, Raring to Go

The stakes for the fifth, and final, Hubble servicing mission couldn't have been higher; not only were two new instruments to be installed (a relatively straight-forward task), not only was much of key infrastructure to be replaced (batteries, fine-guidance sensors, thermal blankets), but intricate repairs had to be performed on the two most complicated instruments (ACS and STIS), something not in the design, something difficult enough in a well-appointed lab on Earth much less done by astronauts in bulky space suits. The servicing mission was postponed, as it became clear that the work to be done was more extensive; but in May 2009 STS-125, involving five full days of space walks and 11 days in space, met all the objectives.
And a little under four months later, after extensive testing and calibration, the Hubble was back in the astronomy business.
This image is the Hubble Ultra-Deep Field (HUDF), as seen by WFC3 in the infrared (now that Hubble Zoo is live, you will have a chance to analyze fields like this yourself!)
MACS J0025.4-1222(right) is not as well known as the Bullet Cluster, but perhaps it should be. One of the really big, open questions in astronomy today is the nature of dark matter; observations of the Bullet Cluster point to dark matter being a form of matter that does not interact with normal (baryonic) matter, except gravitationally. But perhaps the Bullet Clusteris just an anomaly, or perhaps we don't really understand what's going on? In astronomy, as in all science, independent verification is key, and what better way to provide that, for dark matter, than to observe another interacting cluster? "Revealing the Properties of Dark Matter in the Merging Cluster MACS J0025.4-1222" is the paper to read, and Hubble's ACS provided many of the key observations.
A direct image of an exoplanet, and an estimate of its orbit; the coronagraph on ACS blocked out most of the light of Fomalhaut so its planet – Fomalhaut b – could be seen.

WFPC2 was removed during SM4 (and replaced by WFC3); this was Hubble's workhorse camera for some 16 years, the camera which just kept on working. It is fitting then that one of its last images is of Arp 194, dubbed 'the fountain of youth'.
Happy Birthday Hubble!                                                         SOURSCE :

Incredible! Cassini as Houdini Cuts Titan in Half

there's nothing up the sleeves of the Cassini imaging team in this image; it is real! Is themoon Titan being cut in half by Saturn's rings? What is actually happening here is that the middle part of the rings are made dark as Saturn casts its shadow across them. Cassini was just in the right place at the right time, making it appear as though Titan is being sliced in half! The night side of the planet is to the left, out of the frame of the image. Illuminated Titan can be seen above, below and through gaps in the rings. Click the image for a larger version.
As an added benefit in this shot, Mimas (396 kilometers, 246 miles across) is near the bottom of the image, and Atlas (30 kilometers, 19 miles across) can barely be detected near the thin F ring just above the center right of the image. Lit terrain seen here is the area between the leading hemisphere and Saturn-facing side of Titan (5,150 kilometers, 3,200 miles across). This view looks toward the northern, sunlit side of the rings from just above the ringplane.
Below are a few more magical images from Cassini:
Here the moon Enceladus appears strung along a wispy ring of Saturn, likely the G ring. Look close and Enceladus' plumes are visible, too.

Two of Saturn's small moons appear to be sitting on Satun's thin F ring in this image.
From the CICLOPS website:
Pandora (81 kilometers, 50 miles across) is on the left, and Epimetheus (113 kilometers, 70 miles across) is on the right. This view looks toward the northern, sunlit side of the rings from just above the ringplane. Both moons are closer to Cassini than the rings are. Pandora is slightly closer to Cassini than Epimetheus here.
The image was taken in visible light with the Cassini spacecraft narrow-angle camera on Nov. 23, 2009. The view was acquired at a distance of approximately 1.3 million kilometers (808,000 miles) from Pandora and Epimetheus. Image scale is 8 kilometers (5 miles) per pixel.
For more great images from Cassini (which I contend is actually an artist and not a magician!) go to the CICLOPS website and NASA's Cassini website.                                                                                           Soursce :

Supermassive black holes are thought to lie at the center of most large galaxies. But off in a distant remote galaxy, astronomers have possibly found a giant black hole that appears to be in the process of being expelled from the galaxy at high speed. This newly-discovered object was found by Marianne Heida, a student at Utrecht University in the Netherlands, and confirmed by an international team of astronomers who say the black hole was likely kicked out of its galaxy as a result of the merger of two smaller black holes.

Heida discovered the bizarre object, called CXO J122518.6+144545 during her final undergraduate project while doing research at the SRON Netherlands Institute for SpaceResearch. To make the discovery she had to compare hundreds of thousands of X-ray sources, picked up by chance, with the positions of millions of galaxies. X-rays are also able to penetrate the dust and gas that surround black holes, with the bright source appearing as a starlike point. This object was very bright; however, it wasn't at the center of a galaxy.
Super-massive black holes easily weigh more than 1 billion times the mass of the sun. So how could such a heavy object be hurled away from the galaxy at such high speeds? Astronomers say the expulsion can take place under special conditions when two black holes merge. The merger process creates a new black hole, and supercomputer models suggest that the larger black hole that results is shot out away at high speed, depending on the direction and speed in which the two black holes rotate before their collision.
And, the team of astronomers say, there could be more of these "recoiling" black holes out there. "We have found even more of this strange class of X-ray sources," said Heida. "However, for these objects we first of all need accurate measurements from NASA's Chandra satellite to pinpoint them more precisely."
If this object is not a recoiling black hole, other possibilities are that it could possibly be either a very blue type IIn supernova or a ULX (ultra-luminous X-ray source) with a very bright optical counterpart.
Finding more of these expelled black holes will provide a better understanding of the characteristics of black holes before they merge. In the future, astronomers hope to even observe this process with the planned LISA satellite, which will be able to measure the gravity waves that the two merging black holes emit. Further research will provide more insight into how supermassive black holes are created.

Friday, May 14, 2010

Now that we've hunted down Orionand been bull ridin' with Taurus, it's time for us to discover a pair of celestial brothers – theGemini twins. Gemini is one of the members of thezodiac which means the imaginary paththe SunMoon andplanets follow across the sky passes through thestars of this constellation. But what happens when you don't have these solar systems objects to point the way to the pair? Then look over the top of Orion's left shoulder and you'll see two bright stars that live about a thumb's length apart from each other – Castor and Pollux. For many of us, Gemini be almost directly overhead at sky dark.

The slightly fainter star to the northwest is named Castor, and his almost identical brother star angled away to the southeast is Pollux. If you live where skies are dark, give your eyes plenty of time to adjust and you will begin to see the fainter stars that make up the stick figures of their bodies. Their "feet" will always point towards Orion. Once you understand the positions of the stars, it isn't hard to see how ancient civilizations connected these two stars as twins! The ancient Romans saw the brothers Romulus and Remus, the two heroes that founded Rome. The Greek astronomers saw the twins Castor and Pollux, sons of the god Zeus. Oddly enough, both cultures believed the brothers were raised by the half-man, half-bull centaur calledChiron. Perhaps because of the nearby constellation of Taurus? It was Chiron who sent them to help Jason and the Argonauts in their quest to find the golden fleece. Legend has it that the twins rescued Jason's ship from a killer storm and thus earned their place in the sky. Other stories say the twins were born of different fathers, making one mortal and one immortal. Pollux, who would live forever, was an excellent boxer. Castor, who would age normally, was an excellent horseman. When both were called upon to fight in the Trojan war, Castor was killed. Pollux love for his brother was so strong that he could not bear to be parted from him, so he begged Zeus to place them both in the sky as stars. The Arabs also saw this pair of stars as twins, while the Chinese referred to them as Yin and Yang!

interested ? 

So you think you know your universe? We've got our own top 10 list on the most interesting facts about the Universe.

1. It was hot when it was young

The most widely accepted cosmological model is that of the Big Bang. This was proven since the discovery of the cosmic microwave background radiation or CMBR. Although, strictly speaking, no one knows exactly what 'banged', we know from extrapolation that the Universe was infinitely hot at birth, cooling down as it expanded.
In fact, even only within minutes of expansion, scientists predict its temperature to have been about a billion Kelvin. Moving backward to 1 second, it is said to have been at 10 billion Kelvin. For comparison, today's universe is found to have an average temperature of only 2.725 Kelvin.

2. It will be cold when it grows old

Observations made especially on galaxies farthest from us show that the Universe is expanding at an accelerated rate. This, and data that show that the Universe is cooling allows us to believe that the most probable ending for our universe is that of a Big Freeze.
That is, it will be devoid of any usable heat (energy). It is due to this prediction that the Big Freeze is also known as the Heat Death.Accurate measurements made by the Wilkinson Microwave Anisotropy Probe (WMAP) on the current geometry and density of the Universefavor such an ending.

3. The Universe spans a diameter of over 150 billion light years

Current estimates as with regards to the size of the Universe pegs it at a width of 150 billion light years. Although it may seem peculiarly inconsistent with the age of the Universe, which you'll read about next, this value is easily understood once you consider the fact that theUniverse is expanding at an accelerated rate.

4. The Universe is 13.7 billion years old

If you think that is amazing, perhaps equally remarkable is the fact that we know this to better than 1% precision. Credit goes to the WMAP team for gathering all the information needed to come up with this number. The information is based on measurements made on the CMBR.
Older methods which have contributed to confirming this value include measurements of the abundances of certain radioactive nuclei. Observations made on globular clusters, which contain the oldest stars, have also pointed to values close to this.

5. The Earth is not flat – but the Universe is

Based on Einstein's Theory of General Relativity, there are three possible shapes that the Universe may take: open, closed, and flat. Once again, measurements by WMAP on the CMBR have revealed a monumental confirmation – the Universe is flat.
Combining this geometry and the idea of an invisible entity known as dark energy coincides with the widely accepted ultimate fate of our universe, which as stated earlier, is a Big Freeze.

6. Large Scale Structures of the Universe

Considering only the largest structures, the Universe is made up of filaments, voids,superclusters, and galaxy groups and clusters. By combining galaxy groups and clusters, we come up with superclusters. Some superclusters in turn form part of walls, which are also parts of filaments.
The vast empty spaces are known as voids. That the Universe is clumped together in certain parts and empty in others is consistent with measurements of the CMBR that show slight variations in temperature during its earliest stages of development.

7. A huge chunk of it is made up of things we can't see

Different wavelengths in the electromagnetic spectrum such as those of radio waves,infrared, x-rays, and visible light have allowed us to peer into the cosmos and 'see' huge portions of it. Unfortunately, an even larger portion cannot be seen by any of these frequencies.
And yet, certain phenomena such as gravitational lensing, temperature distributions, orbital velocities and rotational speeds of galaxies, and all others that are evidence of a missing mass justify their probable existence. Specifically, these observations show that dark matter exists. Another invisible entity known as dark energy, is believed to be the reason why galaxies are speeding away at an accelerated rate.

8. There is no such thing as the Universe's center

Nope. The earth is not the center of the Universe. It's not even the center of the galaxy. And no again, our galaxy is not the entire universe, neither is it the center. Don't hold your breath but the Universe has no center. Every galaxy is expanding away from one another.

9. Its members are in a hurry to be as far away from each other as possible

The members that we are talking about are the galaxies. As mentioned earlier, they are rushing away from each other at increasing rates. In fact, prior to the findings of most recently gathered data, it was believed that the Universe might end in a Big Rip. That is, everything, down to the atoms, would be ripped apart.
This idea stemmed from this observed accelerated rate of expansion. Scientists who supported this radically catastrophic ending believed that this kind of expansion would go on forever, and thus would force everything to be ripped apart.

10. To gain a deeper understanding of it, we need to study structures smaller than the atom

Ever since cosmologists started to trace events backward in time based on the Big Bang model, their views, which focused only on the very large, got smaller and smaller. They knew, that by extrapolating backward, they would be led into a universe that was very hot, very dense, very tiny, and governed by extremely high energies.
These conditions were definitely within the realm of particle physics, or the study of the very small. Hence, the most recent studies of both cosmology and particle physics saw an inevitable marriage between the two.
There you have it. Feel free to come up with a longer list of your own.