Dark Matter & Large Scale Structures

Dark Matter
Roughly 80 percent of the mass of the universe is made up of material that scientists cannot directly observe. It turns out that roughly 68% of the Universe is dark energy. Dark matter makes up about 27%. The rest - everything on Earth, everything ever observed with all of our instruments, all normal matter - adds up to less than 5% of the Universe. We are much more certain what dark matter is not than we are what it is. First, it is dark, meaning that it is not in the form of stars and planets that we see. Observations show that there is far too little visible matter in the Universe to make up the 27% required by the observations. Second, it is not in the form of dark clouds of normal matter, matter made up of particles called baryons. Third, dark matter is not antimatter, because we do not see the unique gamma rays that are produced when antimatter annihilates with matter. Finally, we can rule out large galaxy-sized black holes on the basis of how many gravitational lenses we see. High concentrations of matter bend light passing near them from objects further away, but we do not see enough lensing events to suggest that such objects to make up the required 25% dark matter contribution. Unlike normal matter, dark matter does not interact with the electromagnetic force. This means it does not absorb, reflect or emit light, making it extremely hard to spot. In fact, researchers have been able to infer the existence of dark matter only from the gravitational effect it seems to have on visible matter. Many theories say the dark matter particles would be light enough to be produced at the LHC. If they were created at the LHC, they would escape through the detectors unnoticed. However, they would carry away energy and momentum, so physicists could infer their existence from the amount of energy and momentum “missing” after a collision. Dark matter candidates arise frequently in theories that suggest physics beyond the Standard Model, such as supersymmetry and extra dimensions. One theory suggests the existence of a “Hidden Valley”, a parallel world made of dark matter having very little in common with matter we know. If one of these theories proved to be true, it could help scientists gain a better understanding of the composition of our universe and, in particular, how galaxies hold together.

Large Scale Structures
The Universe exhibits structure over a wide range of physical scales – from satellites in orbit around a planet through to the galaxy super clusters, galactic sheets, filaments and voids that span significant fractions of the observable Universe. These latter are commonly referred to as the ‘large-scale structure’ of the Universe. In the local Universe, there are two large-scale structures of particular importance: the Great Wall and the Great Attractor. These structures influence the motions of galaxies in the Local Group, and are ultimately responsible for the fate of the Milky Way. In physical cosmology, the term large-scale structure refers to the characterization of observable distributions of matter and light on the largest scales (typically on the order of billions of light-years).
Prior to 1989, it was commonly assumed that galaxy clusters were the largest structures in existence, and that they were distributed more or less uniformly throughout the universe in every direction. However, based on redshift survey data, in 1989 Margaret Geller and John Huchra discovered the "Great Wall," a sheet of galaxies more than 500 million light-years long and 200 million wide, but only 15 million light-years thick.


References:
http://www.sciencedaily.com/articles/l/large-scale_structure_of_the_cosmos.htm
http://astronomy.swin.edu.au/cosmos/L/large-scale+structure
http://science.nasa.gov/astrophysics/focus-areas/what-is-dark-energy/
http://astro.berkeley.edu/~mwhite/darkmatter/dm.html

OWN picture of the Week #8

The photo above is of the Hercules Cluster. While I got it very faded and dull, I was able to edit it to look bright and amazing.

APOD 4.8

Todays APOD is VERY cool. While I cannot attach a photo, I can provide a link.
http://apod.nasa.gov/apod/ap140514.html
This link was supplied by APOD on May 14th and is a live feed from the international space station of the planet earth. It is really interesting to see how fast the earth is spinning from their point of view as they are going thousands of miles per hour, spinning around the earth in a constant free fall. Just beautiful.

Margaret Burbidge Biography

Born in England, Margaret Burbidge educated at the University of London, where she remained until 1951. She has worked at Yerkes Observatory and the California Institute of Technology and has been at the University of California, San Diego since 1962. She has held many administrative positions, including that of director of the Royal Greenwich Observatory and first director of the Center for Astrophysics and Space Sciences at UCSD. In 1957 she, Geoffrey R. Burbidge, William A. Fowler and Fred Hoyle showed how all of the elements except the very lightest are produced by nuclear reactions in stellar interiors. She has also studied spectra of galaxies, determining their rotations, masses, and chemical composition, and she has achieved particular renown for spectroscopic studies of quasars. She has played a major role in developing instrumentation for the Hubble Space Telescope. She was won dozens of awards in her time including the Helen Warner Prize in 1959, the Henry Norris Russel Lectureship in 1984, the National Medal of Science in 1983, the Karl G. Jansky Lecturship in 1977, The Royal Astronomical Study Gold medal in 2005 and even the Albert Einstein World Award of Science in 1988. With nuclear physicist William A. Fowler, astrophysicist Fred Hoyle, and her husband, astronomer Geoffrey Burbidge, she developed a better explanation of how elements are formed by nuclear reactions inside stars. She was born into a very scientific family with her mother and father Marjorie and Stanley Peachey both being chemists and she appoints much of her success to her family. She married her husband Geoffrey in 1948 and had a daughter, Sarah, in 1956. She was the first woman to be appointed director of the Royal Greenwich Observatory. Burbidge served as assistant director (1948–50) and acting director (1950–51) of the Observatory of the University of London. In 1955 her husband, theoretical astrophysicist Geoffrey Burbidge, obtained a Carnegie fellowship for astronomical research at the Mount Wilson Observatory, near Pasadena, California, U.S. Because women were then ineligible for such an appointment, she chose to accept a minor research post at the California Institute of Technology, Pasadena. In 1957 she became Shirley Farr fellow and, later, associate professor at Yerkes Observatory, Williams Bay, Wisconsin. For several years she worked as a chemist instead of an astronomer, as rules forbidding nepotism left her unable to work in her specialty at the universities that employed her husband. She served as research astronomer (1962–64) and thereafter as professor of astronomy at the University of California, San Diego (UCSD), taking a leave of absence to serve as director of the Royal Greenwich Observatory (1972–73). Her Greenwich duties did not come with the traditional honorary title of Astronomer Royal, which instead was given to a male astronomer; Burbidge saw this as another instance of discrimination against women in the astronomical community. In 1972 she refused the Annie J. Cannon Prize from the American Astronomical Society (AAS) because, as it was an award for women only, it represented for her another facet of the same discrimination. Her action led to the formation of a standing AAS committee for the status of women in astronomy. Burbidge later became a naturalized American citizen. As part of her work in quasars, Burbidge, along with Sir Fred Hoyle and Will Fowler, created the B²FH theory. This theory, published in 1957, provided a revolutionary explanation of the origin in stars of all the elements in the periodic table from helium to iron, starting with the lightest element, hydrogen. Her publications include Quasi-Stellar Objects (1967), with Geoffrey Burbidge. Still alive today, Burbidge continues to teach and was inducted into the Women's Museum of California Hall of Fame honoring her career and achievements. She is currently 94 and still has a passionate love for astrophysics that will be remembered for centuries to come.

APOD 4.7

Today's post is from May 10th and is a photo of the inside of the Flame Nebula.

This is only 1400 light years away and is located in the dense part of the Orion nebula. This is actually an xray photo of the nebula and it was taken by the Spitzer Telescope. This nebula will only get denser for several millions more years and this is visually stunning.

Observational Post

This past week has been the same as ever. I won't bore you with the repetition of the same old story. I go out every night and don't see anything different. It is all the same.

Own picture of the Week #7

Above is the Crab Nebula. It isn't super visible but is more so now because I used the program to enhance it