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Mandatory Fields
Conference Poster
Navtej Singh, Ray Butler
"Colour composite images of M15 globular star cluster in our Milky Way galaxy", SFI Research Summit 2010
Optional Fields
Entry to the SFI Research Images Competition at the SFI Research Summit 2010, Athlone, Ireland
Globular star clusters, often simply called "globulars", are dense collections of up to several million stars, held together by their gravity. In our Galaxy, the globulars are very old, consisting of some of the first stars to have formed. It has been suggested that many globulars may have a medium-sized black hole lurking at their centres. This would be very significant, because it is believed that medium-sized black holes were the "seeds" around which galaxies grew, but no-one has ever conclusively found one. This is because a black hole is so dense that not even light can escape its gravitational pull - it cannot be directly seen. However, it would exert a huge gravitational force on passing stars. Therefore, one way to confirm the presence of a black hole is to detect stars moving at unusually high speeds in the centre of a globular. This means taking images a few years apart, and measuring the almost imperceptible movement of each star. But even with high resolution telescopes like the Hubble Space Telescope (HST) and other ground based telescopes, it is difficult to resolve all the stars in the dense cluster centre with conventional image processing techniques. So we are developing an innovative image processing technique to recover the resolution lost to abnormalities in telescope optics, and thus we aim to measure the movements more accurately. \\The colour composite image is of globular M15 in our Milky Way galaxy, one of the candidates for our black hole search. These images were taken using the Hubble Space Telescope and its superb Advanced Camera for Surveys / Wide Field Camera. For comparison, an image is shown both before and after our processing. Stars are much better resolved in the cluster centre in the processed image, and the sharpness no longer varies from the centre of the image to its edge, which is a problem with the original image data. Also seen in the image is Pease 1 - a planetary nebula expelled from a dying star in M15. It is on the lower left side of the cluster centre and bluish in color.
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