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Eye of the Galaxy: Hubble Reveals Galactic Structure in Intricate Detail

Hubble Space Telescope image of NGC 1097, a barred spiral galaxy that lies about 48 million light-years from Earth in the constellation Fornax. Credit: ESA/Hubble & NASA, D. Sand, K. Sheth

This finely detailed image shows the heart of NGC 1097, a barred spiral galaxy that lies about 48 million light-years from Earth in the constellation Fornax. This picture reveals the intricacy of the web of stars and dust at NGC 1097’s center, with the long tendrils of dust picked out in a dark red hue. The extent to which the galaxy’s structure is revealed is thanks to two instruments on the NASAEstablished in 1958, the National Aeronautics and Space Administration (NASA) is an independent agency of the United States Federal Government that succeeded the National Advisory Committee for Aeronautics (NACA). It is responsible for the civilian space program, as well as aeronautics and aerospace research. It's vision is "To discover and expand knowledge for the benefit of humanity."” data-gt-translate-attributes=”[{“attribute”:”data-cmtooltip”, “format”:”html”}]”>NASA/ESA Hubble Space TelescopeThe Hubble Space Telescope (often referred to as Hubble or HST) is one of NASA's Great Observatories and was launched into low Earth orbit in 1990. It is one of the largest and most versatile space telescopes in use and features a 2.4-meter mirror and four main instruments that observe in the ultraviolet, visible, and near-infrared regions of the electromagnetic spectrum. It was named after astronomer Edwin Hubble.” data-gt-translate-attributes=”[{“attribute”:”data-cmtooltip”, “format”:”html”}]”>Hubble Space Telescope: the Wide Field Camera 3  (WFC3) and the Advanced Camera for Surveys  (ACS).

The idea that a single image can be taken using two different cameras is not very intuitive. However, it makes far more sense after delving into how beautiful astronomical images like this one are composed. A helpful starting point is to consider what color is, exactly. Our eyes can detect light waves at optical wavelengths between roughly 380 and 750 nanometres, using three types of receptors, each of which is sensitive to just a slice of that range. Our brain interprets these specific wavelengths as colors. By contrast, a telescope camera like the WFC3 or ACS is sensitive to a single, broad range of wavelengths to maximize the amount of light collected. Raw images from telescopes are always in greyscale, only showing the amount of the light captured across all those wavelengths.

Colour images from telescopes are indirectly possible, however, with the help of filters. By sliding a filter over the aperture of an instrument like the WFC3 or ACS, only light from a very specific wavelength range is let through — one such filter used in this image is for green light around 555 nanometres. This yields a greyscale image showing only the amount of light with that wavelength. This multicolor image of NGC 1097 is composed of images using seven different filters in total. 

Source: SciTechDaily