ASTB03 – Assignment 6 – The Hubble Space Telescope

The Hubble Space Telescope provides a gateway for human-kind to discover and explore the depths of the universe in greater detail than ever before. It was launched into orbit on the space shuttle “Discovery”, on April 24, 1990.[1] While the telescope has only been in  orbit for 25 years, the first idea of a space telescope happened almost 100 years ago, when German scientist Hermann Oberth, who suggested sending a telescope into space on a rocket in 1923.[2] Just after World War II, in 1946, Lyman Spitzer who was a physicist and researcher at Yale, wrote a paper titled, “Astronomical Advantages of an Extra-Terrestrial Observatory”, where he argued the advantages of a space telescope over the ground-based observatories that were in operation at the time.[1][2] In his paper, he wrote that the Earth’s atmosphere blurs and distorts the light that comes from other stars and that even the most precise telescopes on Earth could not avoid this, but a telescope in space would not have to deal with this, and it would also be able to detect x-ray’s emitted from stars and other objects that would usually be blocked by the Earth’s atmosphere.[1] Spitzer headed a National Academy of Science Ad Hoc Committee on the Large Space Telescope, and in 1966, they began performing studies on the use of a space-based telescope.[1] In 1969, they published the paper, “Scientific Uses of the Large Space Telescope”,[1] and because of this, the National Academy of Science approved the telescope and soon after, NASA would as well.[1][2] In 1974, it was suggested that the telescope be equipped with interchangeable instruments that could study wavelengths that ranged from ultraviolet to visible and infrared light.[2] They also suggested a space shuttle could be used to get the telescope into orbit and could be used to repair the telescope in space or return it to Earth for repairs.[2]

The telescope now needed federal funding, which would be difficult to get, because the costs were estimated to be in the $400-$500 million range.[1] The funding was originally denied in 1975.[1] However, in the same year, the European Space Agency began working with NASA on the project.[1][2] A change needed to be made in the proposal to bring the cost down and acquire funding. This change came in the mirror, which was reduced from 3m to 2.4 m, which in turn helped lower the cost to about $200 million.[1] In 1977, Congress would approve funding for the telescope.[1][2] The design of the telescope started soon after, while Perkin-Elmer Corporation were chosen to build the mirror and optical assembly, and Lockheed Missiles and Space Company were chosen to build the spacecraft and its support systems.[1] The Europeans built the solar array that would power the telescope while in orbit.[1] NASA has originally planned to launch the telescope in 1983, which is the same year it was named after Edwin Hubble[1], but there were many delays which led to the optical assembly not being put together until 1984, and the space shuttle not being completely assembled until 1985.[1] After being completed in Dec 1985, there was a planned launch for October 1986, until, early that year when the space shuttle “Challenger” exploded just after launch, causing shuttles to be grounded until 1988.[1] Finally, in April 1990, Hubble was launched and it included the Wide Field/Planetary Camera (WF/PC), Goddard High Resolution Spectrograph (GHRS), Faint Object Camera (FOC), Faint Object Spectrograph (FOS), and High Speed Photometer (HSP).[1]

Soon after the Hubble telescope began operation, scientists noticed that the images were slightly blurred.[1] After investigating the problem, it was shown that the mirror had something called “spherical aberration”, which was caused by the edges of the mirror being ground just a little bit too flat.[1][2] This made the light that bounced off the edges focus in a slightly different spot that the light that bounced off the center, and although it was only approximately 1/50th of the thickness of a sheet of paper, it was enough to cause the images to become blurry.[1][2] Scientists came up with a solution called the Corrective Optics Space Telescope Axial Replacement (COSTAR).[1][2] This was basically a set of small mirrors that could intercept the light and correct for an errors.[2] COSTAR would be installed on the service mission in December 1993 along with the Wide Field/Planetary Camera which was replaced with the Wide Field/Planetary Camera 2.[1][2] Soon after, the telescope became fully functional and was able to return much clearer images.[1]

The Hubble Space Telescope is nearing the end of its life, where it is expected to retire sometime within the current decade.[1][2] However, the James Webb Space Telescope (JWST), is currently being worked on, and will be launched into orbit sometime within the current decade.[2] It will orbit at about 1.5 million km from the Earth and will be capable of studying objects from the earliest times of the universe.[2]

The Hubble Telescope takes about 97 minutes to complete one orbit around the Earth, which means that it is travelling around 8km/sec.[2] It is the type of telescope called a Cassegrain reflector, where light bounces of a main mirror, then bounces off a secondary mirror which focuses the light through a hole in the center of the main mirror, allowing it to reach the instruments on the telescope.[2] It weighs about 24500lbs, and when it changes angles, it spins in the opposite direction since it does not have thrusters.[3] It can generate up to 10 Terabytes of data a year.[3]

The Hubble Space Telescope was instrumental in determining a more accurate age of the universe. It was able to find white dwarf stars that could be aged at approximately 12-13 billion years old.[4] These stars are difficult to find because of how faint they are.[4] Earlier observations made be the Hubble Telescope showed that stars may have begun forming about 1 billion years after the big bang, and this data allows scientists and astronomers to make a much more accurate estimate for the age of the universe.[4] I feel this is a pretty significant moment because it allows us to make more accurate predictions of the formation of galaxies and stars, as well as seeing how the universe has changed and how long it has taken to make those changes.

Another significant moment was the detection of a supernova, 10 billion light-years away.[5] This supports the idea of dark energy, or dark matter causing the universe to accelerate in its expansion.[5] The light from the supernova appears bright, meaning that the universe was slower at the time of that supernova, but more recent supernovas appear dimmer, meaning that the universe had begun accelerating.[5] This is significant because it supports the idea of dark matter and helps explain why the universe does not collapse under the force of gravity.[5] I chose this moment because the evidence of dark matter helps answer many questions we have about how the universe interacts with itself.

A third significant moment occurred in 2008 when the Hubble Telescope took pictures of the extrasolar planet Fomalhaut b.[6] This is important because it was the first time a picture of an extrasolar planet was taken by the telescope in the visible light.[6] Usually this is done by detecting the planet’s atmosphere moving in front of its star.[6] The discoveries of these extrasolar planets then led to discovering an organic molecule in the atmosphere of these planets named, HD 189733b.[7] Unlike Fomalhaut b, this planet was found because it passed in front of its parent star.[7] I feel these discoveries are important because they help reveal different characteristics that these extrasolar planets need in order to sustain life as we know it today, and if life on other planets in the universe is possible.

The Hubble Space telescope has played a major part in what we know in modern astronomy today and has revealed many secrets of the universe that would have been impossible to learn without it. For this reason, the development of the Hubble Space Telescope can be considered one of the greatest moments in astronomy and in the history of the human race.

Links Used:

[1] http://history.nasa.gov/hubble/

[2] http://hubblesite.org/the_telescope/hubble_essentials/

[3] http://www.nasa.gov/mission_pages/hubble/story/

[4] http://hubblesite.org/newscenter/archive/releases/2002/10/

[5] http://science.nasa.gov/science-news/science-at-nasa/2001/ast03apr_1/

[6] http://www.space.com/15892-hubble-space-telescope.html

[7] http://www.nasa.gov/mission_pages/hubble/science/hst_img_20080319.html

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