Astronomy Porfolio

-Zoe Rayner

Biography for each chapter, highlighting an astronomer

Paragraph on Dark Matter

The idea of dark matter came with the observation that galaxies were moving so fast that the gravity formed by the observable matter shouldn't hold the galaxy together. The gravity was not proportionate to the amount of mass seen by any astronomical tools and this led to the theory that there was invisible matter within the galaxies.

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Georges LeMaître was a Belgian Roman Catholic priest, physicist, and astronomer. He used Einstein's discovery in the Theory of Relativity to discover that the universe was expanding in what we call today, the Big Bang Theory. LeMaître stated that the universe came from a “primeval atom” and in his lectures he vaguely referenced this primeval atom as having instability in its radioactive decay which cause the explosion of the Big Bang. His work was met initially with skepticism- many astronomers had only just begun to realise the universe wasn't static- but in 1934 he received the Francqui Prize for his work. His work was modified and expanded on by George Gamow to give us the theory that we have today.

Jill Tarter

Jill Tarter is a retired astronomer who worked as director of the Center for the Search for Extraterrestrial Intelligence (SETI) Research. SETI is developing radio telescopes and equipment to search and listen for alien life. SETI had a project called “Active SETI”, that transmits messages into space to see if there is any response from the universe. Tarter thinks that this won't have any bad effects for the Earth, as Tarter thinks an advanced civilization that can travel to Earth will not be violent. She has cited human social advancement and our transition from violence to a society that can work peacefully with other groups as evidence that visiting life forms would be friendly. Tarter’s work on alien life forms made her the subject of Carl Sagan’s book Contact which was adapted into a movie starring Jodie Foster. Today, Tarter is working on fundraising for SETI because the program relies on private funding.


Nicolaus Copernicus was a Polish astronomer and church canon who developed the heliocentric planetary system. This system stated that the Sun was the center of the solar system. Previously, the Earth was thought to be the center of the solar system, with it being stationary whilst the sun and moon rotate around it; this was described in Ptolemy’s model of the solar system, but Copernicus noticed that the complicated math in Ptolemy’s model had issues and so Copernicus tried to fix these issues with his model. Copernicus’s book ‘De Revolutionibus Orbium Coelestium’ (‘On The Revolution of the Celestial Spheres’) stated his theory that the Sun was the stationary object and everything in the solar system rotated around it. Copernicus waited 13 years to publish his book and theory because of his ties with the church- during the 15th and 16th century, the church had lots of power and influence over the science of the times- and he died the same year he published.


Henrietta Swan Leavitt was born in 1868 in Massachusetts. Once graduating from the ‘Society for the Collegiate Institution of Women’, Leavitt travelled in America and Europe, where she lost her hearing. Leavitt’s interest in astronomy led to her volunteering at Harvard College Observatory, where she was a research assistant and was eventually taken on as staff. She worked in the photographic photometry department, looking at images of stars to find their magnitude. Her work and interest in stars led to her discovering the ‘Period-Luminosity relationship’ which states that cepheid variable stars have greater luminosity- the brighter stars have longer periods of light flashes, which mean they have greater luminosity. This was used by other astronomers to find the distance between other stars and was used by Edwin Hubble. Henrietta Leavitt didn’t receive as much attention for her work when it was first released because the prejudices of the day against women in fields of scientific work.


Galileo Galilei was an Italian mathematician, born in 1564, who developed the “first” telescope. In 1609, Galileo looked at some simple telescopes made by some Dutch eye glasses maker, and began developing his own. He sold this to Venetian merchants, before looking at developing a telescope to look at the night sky. Galileo found through his telescope that the moon wasn't flat, but contained craters and mountains, and that Jupiter has moons that don't revolve around the Earth. This and other evidence which was published in “The Starry Messenger” gave proof to Copernicus’ heliocentric model. This model was labeled as heretical by the church and Galileo was arrested for his support of it (remember that countries in this time didn't seperate the church from its leaders). By the end of his life, however, the church had to admit the truth in Copernicus’ theory and Galileo’s evidence.


Edwin Hubble was born in 1889, and studied astronomy at the University of Chicago. After adjusting, he was asked to help with constructing the Hooker telescope at California Mount. Wilson observatory. Using the Hooker telescope, Hubble took pictures of other galaxies, and by comparing the luminosities of their Cepheid variable stars, was able to prove that their were galaxies outside of the Milky Way. Hubble estimated the distance from the “Andromeda Nebula” to the Milky Way, and because of the high distance found that Andromeda was a galaxy, not a nebula (it was later renamed the “Andromeda Galaxy”). Hubble also worked with Milton Humason and together theorized that red shifting in a galaxies increased as the distance between the galaxies increased- the further away a galaxy is, the faster it's moving. These discoveries have helped with evidence of the Big Bang theory, and his discovery of other galaxies outside the Milky Way helped astronomers of the time realize the size of the universe to help further their work