In 1990, the field of astronomy was forever changed with the launch of the Hubble Space Telescope. While it was not the first space observatory, its unprecedented resolution and versatility allowed for the deepest and most detailed images of the Universe ever taken. The latest image to be released by the mission features the spiral galaxy NGC 691, which was captured in amazing detail by Hubble’s Wide Field Camera 3 (WFC3).
This galaxy is located about 120 million light-years from Earth in the constellation Aries and is the foremost member of a group of gravitationally-bound galaxies (known as the NGC 691 galaxy group). The first recorded observations of this galaxy were made by German-British astronomer William Herschel on November 13th, 1786. Subsequent observations have determined it has a three-ring structure and measures about 120,000 light-years in diameter.
As with other celestial objects, Hubble observed NGC 691 using a range of filters that allow certain wavelengths of light (from ultraviolet and visible light to infrared) to reach the WFC3. The resulting filtered images are then colored in by specialists who select colors that best represent the different wavelengths observed. Whereas ultraviolet is generally colored in violet and infrared in red, visible light from stars, gas, and dust is shown in white-blue.
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These processed images are then combined to create a full-color image that provides insight into the nature and appearance of celestial objects. In the case of NGC 691, the resulting image shows the beautiful ring structure of the galaxy, the rippled nature of individual rings, and the intensely bright Active Galactic Nucleus (AGN) – a strong indication of a supermassive black hole (SMBH) at its core.
Decades later, Hubble is still providing the world with some of the most breathtaking views of the Universe! A number of more advanced observatories will be heading to space very soon, all of which are expected to make some very profound discoveries. Yet none of them can rival the game-changing nature of Hubble, which came along at exactly the right time and established the foundation upon which all future missions will stand.
Further Reading: NASA