Monday, May 30, 2011

APOD 4.8

Picture from May 24, 2011

There are three arches visible in this picture. Two of which are those of the Double Arch in Arches National Park in Utah. The third is the majestic arch of the milky way, far off in the distance. The arches of the Double Arch are made of sandstone, which consists of many tiny grains of quartz and feldspar cemented together. In a way, the third arch of the galactic plane is similarly comprised in that it's appearance is the result of millions of individual stars and countless particles of gas and dust. It is this similarity which is illustrated here that makes this photo so interesting for me.

Friday, May 20, 2011

APOD 4.7

Picture from May 13, 2011

This stunning photo is of the object known as the Trifid Nebula. The nebula, also known as M20, is about 40 light years across and located in the constellation of Sagittarius, which contains many star forming regions due to being in the direction of the galactic center. The Trifid actually portrays three types of nebulae: red emission nebulae, blue reflection nebulae, and dark absorption nebulae. The emission nebula is seen in the center, with the dark nebula interspersed within it and the reflection nebula around it. As you may have guessed, this three part structure is where the Trifid gets its name.

Tuesday, May 17, 2011

Biography of Subrahmanyan Chandrasekhar

Biography of Subrahmanyan Chandrasekhar

    Subrahmanyan Chandrasekhar was an Indian-born American astronomer of the 20th century. The majority of his work focused on the structures and life cycles of stars. His most prominent studies were conducted on the subject of radiation emitted from stars, particularly white dwarf stars. He was the first to discover that higher mass white dwarfs have smaller radii, and made many contributions to astrophysics regarding stars, including the establishment of the Chandrasekhar limit.
    Chandrasekhar was born on October 19, 1910, in Lahore, India (which today is part of Pakistan) as the first son of what would eventually be a family of 12. Chandra received his first education from his parents starting at age 5. His mother taught him Tamil and his father taught him English and arithmetic. Quite early on, Chandra already had his sights set on being a scientist of some description, and to that end he began to study physics and calculus on his own. By 1918, the family had moved south to Madras where he was taught by tutors until 1921, when he enrolled in Hindu High School in Triplicane. Quickly becoming the head of the class, Chandra finished high school by age 15, at which time he began attending in Presidency College in Madras. Despite his father’s wishes that he pursue physics, Chandra’s studies were mainly focused on mathematics.
    After Chandra graduated with an M.A. in 1930, he set off for Trinity College, Cambridge, courtesy of a special government scholarship. During the long journey from India to Cambridge, Chandra began working out his own theory on stellar evolution. Inspired by his idea, Chandra turned to astrophysics studies once he arrived at Cambridge. In 1932, he was inducted into the Royal Astronomical Society. It was at one of the meetings of the RAS that Chandra stated his ideas about the stellar life cycle, specifically that not all stars that deplete their hydrogen reserves can end their lives as stable white dwarfs. If the mass of an evolving star exceeds a certain limit, he proposed, the star may instead go supernova, and become an even denser neutron star. This mass limit, which was eventually calculated to be 1.4 solar masses, would be known as the Chandrasekhar limit, and would become the discovery that made Chandra a name for himself. Unfortunately, the theory wouldn’t actually be widely accepted for another 20 years.
    Chandra then spent time at Harvard University from 1935-1936, was offered a research position at the Yerkes Observatory in Williams Bay, Wisconsin, and would eventually move to the United States as a permanent resident. During World War II, he was employed at Aberdeen Proving Ground in Maryland doing research in ballistics and shock waves. In 1942, he was promoted to associate professor of astrophysics at the University of Chicago, and around 1944, shifted his research from stellar dynamics to radiative transfer. Chandra became an official U.S. citizen in 1953, and despite receiving numerous offers from all over the world, he never left the University of Chicago until 1980, when he voluntarily retired. Throughout his career, he received numerous awards and accolades, including the National Medal of Science of the United States, the Lincoln Academy Award of Illinois, and the Nobel Prize in Physics. Chandrasekhar died on August 21, 1995, at the age of 84.

Sunday, May 15, 2011

Chandrasekhar Bibliography Sources

"Subrahmanyan Chandrasekhar." Encyclopedia of World Biography. 2nd ed. Vol. 3. Detroit: Gale, 2004. 426-429. Gale Virtual Reference Library. Web. 15 May 2011.

"Subrahmanyan Chandrasekhar." Science and Its Times. Ed. Neil Schlager and Josh Lauer. Vol. 6: 1900 to 1949. Detroit: Gale, 2000. 502. Gale Virtual Reference Library. Web. 15 May 2011.

Friday, May 6, 2011

APOD 4.6

Picture from May 3, 2011

This is the globular cluster known as M15 in the constellation of Pegasus. A globular cluster is a large grouping of stars held together by only their own gravity. This particular cluster is about 35,000 light years away, consists of more than 100,000 stars and, like most globular clusters, dates back billions of years to the early days of the Milky Way galaxy. M15 is noted for being easily visible with binoculars and has one of the densest known star concentrations near its center, which recent evidence suggests actually contains a black hole.