A Blue Whirlpool In The River: Tranquil Galaxy Home To Violent Events

% of readers think this story is Fact. Add your two cents.

Credit: ESO

The galaxy NGC 1187 [1] is seen almost face-on, which gives us 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, we 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 centre, 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.

 

This zoom video sequence starts with a wide view of the large but faint constellation of Eridanus (The River), not far from the more familiar form of Orion (The Hunter). As we zoom in we see a small patch of light that proves to be an attractive spiral galaxy named NGC 1187. 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 

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 [2]. 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.

 

This wide-field view is centred on the spiral galaxy NGC 1187 in the constellation of Eridanus (The River). It is a colour composite made from exposures from the Digitized Sky Survey 2 (DSS2). The distorted companion galaxy ESO 480-G020 can be seen to the upper-right of NGC 1187, close to a star. The bright star at the bottom of the picture is Tau3 Eridani.

Credit: ESO/Digitized Sky Survey 2. Acknowledgment: Davide De Martin.

In October 1982, the first supernova seen in NGC 1187 — SN 1982R [3] 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 [4]. 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.
]
This picture taken with ESO’s Very Large Telescope shows the galaxy NGC 1187. This impressive spiral lies about 60 million light-years away in the constellation of Eridanus (The River). NGC 1187 has hosted two supernova explosions during the last thirty years, the latest one in 2007. This supernova is still faintly visible in this picture and is marked with a circle.

Credit: ESO

These data were acquired using the FORS1 instrument attached to the ESO’s Very Large Telescope at the Paranal Observatory in Chile.

This chart shows the 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

This galaxy was discovered in England by William Herschel in 1784.

One class of supernova explosions occur at the end of a massive star’s lifetime — stars more massive than eight solar masses — when its nuclear fuel is exhausted and the star is not longer able to counteract gravitational collapse, producing a violent explosion. Alternatively, a supernova explosion can also occur in a binary star system, in which a carbon-oxygen white dwarf is pulling matter from a higher-mass companion star. If enough matter is transferred, the star will begin to collapse, producing the supernova explosion.

 

This pan video takes a close look at a new image taken with ESO’s Very Large Telescope showing the galaxy NGC 1187. This impressive spiral lies about 60 million light-years away in the constellation of Eridanus (The River). NGC 1187 has hosted two supernova explosions during the last thirty years, the latest one in 2007.

Credit: ESO. Music: Disasterpeace

The International Astronomical Union is responsible for naming supernovae after they are discovered. The name is formed by the year of discovery, followed by a one or two letter designation. The first 26 supernovae of the year get an upper case letter from A to Z. Subsequent supernovae are designated with two lower-case letters.

Further information about SN 2007Y is available in a paper by Stritzinger et al.

Richard Hook
ESO