A blue whirlpool in the River

The seemingly tranquil galaxy NGC 1187 in Eridanus has hosted two violent events in the past 30 years.
By | Published: August 1, 2012 | Last updated on May 18, 2023
VLT image of the spiral galaxy NGC 1187. Credit: ESO
A new image taken with the European Southern Observatory’s (ESO) Very Large Telescope (VLT) shows the galaxy NGC 1187. This impressive spiral lies about 60 million light-years away in the constellation Eridanus the River. NGC 1187 has hosted two supernova explosions during the past 30 years, the latest one in 2007. This picture of the galaxy is the most detailed ever taken.

The galaxy NGC 1187 is seen almost face-on, which gives us a good view of its spiral structure. You can see about half a dozen prominent spiral arms, 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 toward 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 center, enhancing star formation there.

Around the outside of the galaxy, many fainter and more distant galaxies can also be seen. Some even shine right through the disk of NGC 1187 itself. Their mostly reddish hues contrast with the pale blue star clusters of the much closer object.

NGC 1187 looks tranquil and unchanging, but it has hosted two supernova 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 among 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.

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.