Constellation Eridanus And NGC 1187: A Blue Whirlpool In The River

NGC 1187, a spiral galaxy about 60 million light-years away in the constellation of Eridanus (The River), may look tranquil but it's home to some violent events. NGC 1187 has hosted two supernova explosions during the last thirty years, the latest one in 2007.NGC 1187 was discovered in England by William Herschel in 1784 and can be seen almost face-on, which gives astronomers a good view of its spiral structure. About half a dozen prominent spiral arms can be seen, each containing large amounts of gas and dust. The bluish features in the spiral arms indicate the presence of young stars born out of clouds of interstellar gas.

NGC 1187 was discovered in England by William Herschel in 1784 and can be seen almost face-on, which gives astronomers a good view of its spiral structure. About half a dozen prominent spiral arms can be seen, each containing large amounts of gas and dust. The bluish features in the spiral arms indicate the presence of young stars born out of clouds of interstellar gas.

Looking towards the central regions, you can see the bulge of the galaxy glowing yellow. This part of the galaxy is mostly made up of old stars, gas and dust. In the case of NGC 1187, rather than a round bulge, there is a subtle central bar structure. Such bar features are thought to act as mechanisms that channel gas from the spiral arms to the center, enhancing star formation there. Around the outside of the galaxy many much fainter and more distant galaxies can also be seen. Some even shine right through the disc of NGC 1187 itself. Their mostly reddish hues contrast with the pale blue star clusters of the much closer object.

NGC 1187 in the constellation of Eridanus. Credit: ESO

NGC 1187 looks tranquil and unchanging, but it has hosted two supernovae explosions since 1982. A supernova is a violent stellar explosion, resulting from the death of either a massive star or a white dwarf in a binary system. Supernovae are amongst the most energetic events in the Universe and are so bright that they often briefly outshine an entire galaxy before fading from view over several weeks or months. During this short period a supernova can radiate as much energy as the Sun is expected to emit over its entire life span.

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Wide view of the large but faint constellation of Eridanus, not far from the more familiar form of Orion (The Hunter). The detailed final view shows a new VLT image of this object. Credit: ESO/A. Fujii/Digitized Sky Survey 2. Acknowledgment: Davide De Martin. Music: Disasterpeace

In October 1982, the first supernova seen in NGC 1187 — SN 1982R was discovered at ESO’s La Silla Observatory and more recently, in 2007, the amateur astronomer Berto Monard in South Africa spotted another supernova in this galaxy; SN 2007Y. A team of astronomers subsequently performed a detailed study and monitored SN 2007Y for about a year using many different telescopes. This new image of NGC 1187 was created from observations taken as part of this study and the supernova can be seen, long after the time of maximum brightness, near the bottom of the image.

Location of NGC 1187 in the constellation of Eridanus (The River). This map shows most of the stars visible to the unaided eye under good conditions, and NGC 1187 itself is highlighted with a red circle on the image. This galaxy appears as a faint smudge through medium-sized amateur telescopes under good conditions. Credit: ESO, IAU and Sky&Telescope