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Transcript
CEPHEID VARIABLES AND THE FAULKES TELESCOPE Dr ‘Dill’ Faulkes is a British millionaire who believes that a scientific education is of such importance to school children that he donates considerable sums of money to develop projects that benefit students in all manner of scientific and mathematical areas. One of these projects is the Faulkes Telescope – a pair of robotic, researchgrade, 2-metre aperture telescopes located in Hawaii and New South Wales. Swinburne University has been assigned the task of managing the educational programs for Australian schools. The Australian telescope is due for completion in early 2004. How far away are the stars? This question has long been the focus of astronomical research. Early civilisations built pyramids to climb so that they could be closer to the stars to make better observations! Up until the early 20th century, the Milky Way was thought to be the whole universe! The main problem is that light sources appear dimmer as you move away from them. The relationship is well known (an inverse square law), however, to determine the distance, you need to know the intrinsic brightness of the object. As this was not known, it was impossible to accurately measure the distance to the star. Not until Edwin Hubble discovered cepheid variable stars in M31 (the Andromeda Galaxy) did astronomers start to get an idea of cosmic distances. How was this achieved? For stars relatively close to the Earth, stellar parallax was used. However, this method was not viable for large distances. Cepheid variables A cepheid variable star varies in brightness. Around 1908, while examining photographic plates of the Large Magellanic Cloud, the American astronomer Henrietta Leavitt found that there was a relationship between the brightness of the stars and the period of the luminosity cycle: the brighter the star, the longer the period. Using parallax methods, astronomers then worked out how to link the period of the cepheid to the absolute luminosity of the star. Type Ia supernovae Most stars form in pairs. The formation process usually results in pairs of stars that are at slightly different stages of their lifecycles. This may lead to a situation where a white dwarf star orbits a red giant. The white dwarf draws material from the outer layers of the red giant onto its surface. This material heats up until fusion starts and the entire white dwarf is consumed in a runaway thermonuclear reaction. Astronomers believe that the intrinsic brightness of this process is nearly constant. This allows the distance to the supernova to be calculated. Supernovae are relatively rare but important events for astronomers. The chance to observe the process is eagerly sought after. However, research telescopes cannot afford the time to search for such random events. Fortunately, there are thousands of amateur astronomers who search for just such events and notify the astronomical community (a process greatly assisted by the advent of email) who then turn their large telescopes all around the world towards the event. (Picture: Space Telescope Science Institute and NASA) Supernova 1994D The Faulkes Telescope To obtain the required measurements of cepheid variables or to detect a distant Supernova, a quality telescope is required. A larger telescope will allow more distant events to be detected. Along with the telescope, a method of recording the data is required. In the past this was done with photographic plates. Today, however, CCD cameras are being used because they digitise the data. This allows easy analysis and storage of the images on computers. The Faulkes Telescope is a telescope built purely for students to use. It allows students to access a large (2-metre aperture) telescope via the Internet. Appropriate image – analysis software is provided to allow you to go hunting for your own supernova or measure your own cepheid variables. The Centre for Astrophysics and Supercomputing is keen for students to use this new facility and share in the new discoveries that new technology allows. Charles Sturt University has a similar program with a smaller robotic telescope. The Faulkes Telescope under construction. Note the size of the worker! (Picture: Telescope Technologies Limited)