Subrahmanyan Chandrasekhar October 20, 2009
Posted by jcconwell in Astronomers, Astronomy, white dwarf.Tags: Chandrasekhar, white dwarf
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One Hundred years ago, yesterday, October 19, 1910, Subrahmanyan Chandrasekhar was born.
Arguably the greatest astrophysicist of the twentieth century, his name is in every astronomy book. From the upper mass limit of a white dwarf, Chandrasekhar’s limit, to the orbiting Chandra X-ray telescope, he left his mark on the very concepts and vocabulary that physicists and astronomers use today.
Chandrasekhar was the nephew of Sir Chandrasekhara Venkata Raman, who won the Nobel Prize for Physics in 1930. Chandrasekhar was educated at the University of Madras, and at Trinity College, Cambridge. From 1933 to 1936 he held a position at Trinity.
By the early 1930s, scientists had concluded that, after converting all of their hydrogen to helium, stars lose energy and contract under the influence of their own gravity. These stars, known as white dwarf stars, contract to about the size of the Earth, and the electrons and nuclei of their constituent atoms are compressed to a state of extremely high density. Using the new theory of Quantum Mechanics, Chandrasekhar determined what is known as the Chandrasekhar limit—that a star having a mass more than 1.44 times that of the Sun does not form a white dwarf but instead continues to collapse. Later it was found that more massive stars cores collapse blows off its gaseous envelope in a Type II supernova explosion, leaving a neutron star. An even more massive star continues to collapse leaving a black hole. Type Ia supernova use the same mechanism in a different way.If a binary star system has a white dwarf stealing matter from its companion, and it exceeds Chandrasekhar limit, the white dwarf will collapse and detonate. For this contibuttion he was awarded the 1983 Nobel Prize in Physics
These calculations contributed to the eventual understanding of supernovas, neutron stars, and black holes, and the production of the elements in the periodic table.
Good bye Walter…. July 18, 2009
Posted by jcconwell in Astronomers, Astronomy, Space Craft.Tags: Apollo 11, Walter Cronkite
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Legendary CBS news anchor Walter Cronkite, died June 17, 2009. Even though he hasn’t sat in the anchor chair for more than a quarter of a century, the impact on both journalism and the space program is felt even today.
Both objective and passionate, Walter Cronkite, personified the best in reporting, but especially science reporting. In my opinion he was as reponsible for making more scientist of my generation, than any person. And “That’s the way it is”
Women who broke the barriers….. July 15, 2009
Posted by dhsscienceteacher in Astronomers, Astronomy.Tags: Astronomy, Hypatia
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Mellisa Ray has her blog at http://dhsscienceteacher.wordpress.com/ and is my long suffering Graduate assistant this summer.
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Einstein, Newton, Kepler…. these are astronomers whom every high school student knows. However, I remember wondering in high school, “Where are the women scientists?” Whether it be in the grade school or the university level, I believe every science teacher should know of more scientists than Einstein, Newton and Kepler. Perhaps the astronomers I will discuss are more obscure than Newton, but discussing them might inspire a young girl to choose a different career path. Although this list is short; these are a few of my favorite great women.
- Hypatia
- Annie Jump Cannon
- Cecilia Payne-Gaposchkin
- Jocelyn Bell Burnell
Hypatia of Alexandra was born between 350 and 370 AD. A woman in a land of very few options, she rose to be considered the first notable woman in mathematics. Her father was her teacher while living in Roman Egypt. It is thought she wrote on astronomy, mathematics, and philosophy. She may have invented the plane astrolabe, the graduated brass hydrometer, and the hydroscope. The plane astrolabe would be used to estimate time given a known star’s altitude. A hydrometer would be used to find density, and the hydroscope would be used to see under water. She was a very unusual woman during her time often acting like a man in a time when men and women held very separate roles. It is believed she angered an influential bishop at the time who convinced others to dislike her. In the year 415 AD, she was killed by a Christian mob. Although it is unknown for sure, it has been said she was flayed and burned. Very little is know about her since much of her work was destroyed in a fire.
Annie Jump Cannon was born in 1863. She was a Wellesley graduate for her undergraduate and graduate studies. She worked for Professor Whiting learning spectroscopy at Wellesley. After graduation, she was hired by Harvard to work as a “computer” along with a number of othe women making very little money. She found the spectral sequence of different stars eventually helping come up with OBAFGKM. She published nice volume of Henry Draper Catalog and the Henry Draper Extension. She was appointed professor at Harvard two years before her retirement. Cannon classified close to 300,000 stars in her lifetime. She also classified five nova and approximately 300 long-period variable stars.
Cecilia Payne-Gaposchkin was born in 1900. She completed her studies at Cambridge but was not awarded a degree because women did not receive degrees at the time. She eventually traveled to Harvard to work with Harlow Shipley. By 1923, she was ready to present her thesis to Radcliffe College. Her dissertation is considered one of the best ever in astronomy. In her thesis, she calculated a temperature scale to go with the classification system. Due to her theory of what stars are composed of, she discussed the Sun being made almost completely of hydrogen. Although she was correct, she did not make a definite conclusion as many believed at the time that the Sun was made of the same main elements as our planet. She stayed at Harvard for career only briefly thinking of leaving because of her lack of title. Eventually she was named chair of the department.
Jocelyn Bell Burnell was born in 1943. While at Cambridge, she helped her advisor, Antony Hewish, to create a telescope for their research needs. It was an extremely large radio telescope. She analyzed long pages of lines to try to find differences. She did find a difference in the lines, leading to the discovery of pulsars while she was working on her Ph.D. at Cambridge University in 1967. She received her Ph.D. in radio astronomy in 1968. Eventually, Martin Ryle and Hewish provided the theoretical information about pulsars and received the Nobel Prize for it; however, Burnell was left out of the award. After graduating, she continued her love of astronomy by seaching the night sky throughout her career while working at a number of universities in the United Kingdom.
Websites:
http://www.wellesley.edu/Astronomy/Annie/
http://www.sdsc.edu/ScienceWomen/cannon.html
http://www.distinguishedwomen.com/biographies/cannon.
http://womenshistory.about.com/od/hypati1/a/hypatia.htm
http://en.wikipedia.org/wiki/Hypatia_of_Alexandria ,
http://starchild.gsfc.nasa.gov/docs/StarChild/whos_who_level2/bell.html
http://www.scientificamerican.com/slideshow.cfm?id=10-nobel-snubs&thumbs=horizontal&photo_id=D2B78179-CAD3-E707-DB0C8A010B583A87
http://cwp.library.ucla.edu/Phase2/Payne-Gaposchkin,_Cecilia_Helena@861234567.html
http://www.harvardsquarelibrary.org/unitarians/payne2.html
16th-century skeleton identified as astronomer Copernicus November 22, 2008
Posted by jcconwell in Astronomers, Astronomy.Tags: Archeoastronomy, Copernicus
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The long-lost skeleton of Nicolaus Copernicus – the 16th-century astronomer who transformed our understanding of the solar system – has been found, Polish researchers have confirmed.
Full story at http://www.guardian.co.uk/science/2008/nov/21/astronomy-archaeology





