LIGO

LIGO short for Laser Interferometer Gravitational-Wave Observatory is a new type of Observatory that doesn't search the skies using telescopes, but uses a new concept of gravity waves. This is the first of it's kind with two observatories currently running, one in Livingston, Louisiana, and the other in Richland, Washington. They had to build two observatories so that they can be sure when they found something that it wasn't something else so they would compare with the other observatory across the nation to make sure they received the same signal.

This observatory is based on the theory of Gravitational Waves that are emitted from objects when they move or change in mass similar to that of a magnetic field, such that the change creates a wave propagating through space. All objects release such gravitational waves, and these waves warp space-time in the perpendicular direction of it's propagation, stretching and compressing space-time like a sine function. However, these distortions are very very tiny, on magnitudes smaller then the size of a proton, and so are very difficult to detect. That's where LIGO steps in, they set up two very precise lasers that go in perpendicular directions and reflect off a mirror then back to a detector. The premise is so that while in one direction space-time would be stretched, and the other it would be compressed so the two lasers don't hit the detector at the same time like they should and as the wave moves the change in the interference pattern of the lasers should coincide with the gravity wave. Thus they would be able to detect it and learn more about the universe.

LIGO has two 4 km long vacuum tubes for the lasers to travel down, with the expansive distance needed to detect smaller waves, and the distances known have to be precise and insulated against movement such as an earthquake. The picture above shows the one in Louisiana and the building shown is where the lasers are fired from and come back to be detected. In 2008 a project was started to increase the sensitivity of LIGO so that it should be able to detect farther objects, and weaker objects that are closer, they expect this upgrade to be done by 2014. This is a very fascinating observatory and concept, however personally I do see a bit of a problem. While the idea seems sound, I wonder if the waves come in at intervals to where the time it takes the laser to go out it contracts, but then on the way back it has expanded so that both lasers get back at the same time still and thus show no wave. I do not know the math used to do the calculations, but seems this could be a problem if not adjusted for, and I'm not sure if it is a concern or not, but was a question hopefully addressed. Nevertheless this type of observation and detection should open a new depth of information about the universe and what's in it.

Curvature of the Universe

Going back to CMB cosmic microwave background radiation, using this allows us to actually calculate what the curvature of the universe is. The geometry of the universe is related to its density which is originally used to determine the fate of the universe, whether or not it will collapse or expand forever. The term "critical density" is used as the turning point of whether or not the universe collapses or expands, although this is without the use of Dark Energy, which when added can affect whether or not it goes one way or the other. Of course the other use as stated above is the curvature of the universe, whether the universe is flat, open, or closed, as the picture above shows from NASA's article.

If the density of the universe is greater then the critical density, then the universe is closed, and shaped like that on the top, of a sphere where light can circle around the universe and get back to the starting point again if the universe lasts long enough. If the density of the universe is less then the critical density, then the universe is open, and shaped like the one in the middle, going on forever and negatively curved. However findings show that the universe is equal to the critical density, causing it to be flat like the bottom picture, and thus expanding infinitely.

This measurement is taken with WMAP a spacecraft that can measure CMB and they look for fluctuations or "spots" in the CMB. When they find these spots, they can measure the distance between two of them, and based upon the distance with the parameters of the big bang theory, they can calculate what the shape of the universe is. If these spots were to be more than one degree apart then the universe is closed, less then one degree and the universe is open. Now if the spots are about one degree across then the universe is flat, and this is what they were able to calculate to within a 0.5% error. This conclusion gives us what the density of the universe is as well which is equal to it's "critical density" which  helps with calculations such as the expansion rate of the universe and how much dark matter is in the universe all used together in the Lambda-Cold Dark Matter model of the universe.

Universe Expansion Accelerating

So I mentioned I would get back to this topic, and so I have simply put, the universe is expanding at an increasing rate. This discovery gave the nobel prize to Saul Perlmutter and his team of researchers, as well as Adam Reiss and Brian Schmidt and their team of researchers. These two groups were able to detect the rate of expansion of the universe using supernovae. They were able to take type Ia supernovae and due to the redshift of the light detected were able to calculate the velocity of the supernovae going away from us. After getting velocities of various supernovae at various distances they were able to conclude that the ones closer to us, and thus not as far back in time, were moving faster. This discovery is what first gave rise to Dark Energy, as there had to be a source for this increasing universe expansion, and was concluded that some "Dark Energy" in empty space was repelling matter like anti-gravity, and causing the velocity to increase as they got farther apart.

The picture above courtesy of NASA is a good representation of how this works.

Thus Dark Energy was discovered to explain the findings of the acceleration of the universe expansion. These measurements combined with the "standard model" of big bang cosmology, or known as the Lambda-Cold Dark Matter model (ΛCDM), gives the amount of Dark Energy that should be in the universe to cause this expansion acceleration based on the amount of Dark Matter and normal matter in the universe. This number sits at approximately 70% as I previously posted about, the expansion rate acceleration that is currently calculated is much more accurate then they first discovered sitting at 73.8 kilometers per second per megaparsec. It means that for every million parsecs of distance from us, the rate of expansion increases by that amount. This newly found acceleration changes the theory on how the universe would end, which used to be what was termed as a "big crunch" where the universe collapses in on itself. Now it is theorized it will continue to expand, and in some theories it will accelerate until all matter is ripped apart due to the repulsion effect of the Dark Matter causing what's coined as the "Big Rip". However, since almost nothing is known on Dark Matter, it is unsure how things will continue with the universe, for now the universe expansion is accelerating, and we will continue to study and find out the mysteries that remain.

Dark Energy

This is probably one of the most interesting topics right now due to the fact that very little is known about it. Dark Energy is what this mysterious force is called, however it has nothing to do with the similarly named Dark Matter. This was first discovered because of what they found about the expansion of the universe (more on that later) which required an explanation more then normal matter and Dark Matter could provide. Thus they called it Dark Energy, and is believed to make up approximately 70% of the universe. Einstein first theorized it calling it a cosmological constant, but then retracted it believing that it was a mistake, although now it's seen as the most prominent explanation for Dark Energy. It's believed that this energy is the energy due to empty space, and that it acts like anti-gravity repulsing instead of attracting, so with more empty space then there would be more Dark Energy. However, there are other theories of what Dark Energy is, another prominent explanation is that for quintessence. This theory believes that Dark Energy is a quintessence field, like there are EM fields, and the difference with this then the cosmological constant theory is that quintessence varies with time and space. There are still other theories, unfortunately this is all still theory, it has yet to be proven, and no one really knows how or why Dark Energy exists. There is a lot of research underway to figure it out Dark Energy and see what it really is, which should prove interesting to future generations of astrophysicists.

Dark Matter Core Defies Explanation

I gave an explanation of Dark Matter in an earlier post for this article that I have recently read and find interesting. Astronomers were able to observe a clump of dark matter left behind after a collision of galaxy clusters. It was theorized that dark matter in galaxy clusters would stay anchored with the galaxies even after violent collisions, however this new development has destroyed that theory when with what they call a Dark Matter Core was left behind with an abundance of hot gas after two of these galaxy clusters collided, and continued on as a merged galaxy cluster called Abel 520. It was initially observed in 2007 and was shrugged off as unreal due to poor data, however as new data has come in, the data was confirmed that there was a dark matter core left behind. This has forced researchers to question and redefine how they believe dark matter to work.

The image above (pictured the core of the merging galaxy cluster Abel 520 and it's distribution of hot gas, galaxies, and dark matter) and article can be found here

Dark Matter

I'm going to introduce something that is still unknown and is greatly studied today in astrophysics, Dark Matter. What is Dark Matter? Well simply put it's matter that can not be detected by any means, it emits no light or any electromagnetic frequency: gamma rays, x-rays, radio, or microwave. It is undetectable by normal means, however you might ask, how is it then that we know it's there? It is detectable indirectly by the gravitational lensing it produces from galaxies behind it in our line of sight. The gravitational lensing causes the galaxies light to bend around the Dark Matter causing the galaxy to appear elsewhere. As shown on the picture above, the light (white arrow) gets bent around and we perceive it to come from the location of the orange arrows. This allows us to indirectly detect the existence of the Dark Matter and calculations have shown that it makes up approximately 25% of the universe whereas normal matter makes up a measly 5% and the rest is in the form of Dark Energy which I will talk about later. Unfortunately that is about where our knowledge of Dark Matter ends, we don't know what it is made of or how it interacts exactly within the universe. It is a great topic of research and discovery, and hopefully within a few years we will have the answers we seek.

Triple Conjunction

There's something in the news today, I have read that over the weekend a seemingly rare event has occurred. It is called a "triple conjunction" which means that three celestial bodies appear near each other in the sky. The picture above is of a similar event three years ago over ESO's Very Large Telescope, with the same three celestial bodies, Jupiter, Venus, and the moon. This weekend it happened again over Southern California, and it seems that a conjunction itself is not that rare. There are plenty that happen with various planets in our solar system, and there are various kinds such as a great conjunction which involve Jupiter and Saturn that come about every 20 years or so. Some so rare they haven't happened again in 50 years since the last one, which was a great conjunction that involved all five of the naked-eye planets (Mercury, Venus, Mars, Jupiter, and Saturn) plus the sun and moon. This is the article I read, and Wikipedia has some good information about upcoming conjunctions if you would be interested in catching one.