Hubble image shows a glowing spiral galaxy turned on its side

The galaxy NGC 3432, as imaged by the Hubble Space Telescope. The image shows a spiral galaxy seen edge-on from our perspective on Earth. ESA/Hubble & NASA, A. Filippenko, R. Jansen

This sparkling image shows the galaxy NGC 3432, captured by the Hubble Space Telescope. Although it appears to be a flat line from this angle, the galaxy is actually spiral-shaped and we are observing it edge-on. The galaxy is located 45 million light-years away from Earth in the constellation of Leo Minor (the Lesser Lion).

Due to the angle from which the galaxy is imaged, you cannot see its spiral arms or its bright core. But you can see dark patches of cosmic dust which block light from reaching us and bright shining pink spots where new stars are being born. Because spiral galaxies are common, Hubble has imaged many of them from all sorts of angles over the years, so astronomers are able to tell that NGC 3432 is a spiral galaxy even though they cannot see it head-on.

In 2000, the NGC 3432 galaxy was the source of an intriguing mystery. A massive burst of light called SN 2000CH was spotted as part of the Lick Observatory Supernova Search survey, also known as LOSS, which was performed with the Katzman Automatic Imaging Telescope located in San Jose, California. At first, the astronomers thought that the burst of light they saw was a supernova within our galaxy. But then they realized that the event was much further away than they had thought, and had actually occurred in the NGC 3432 galaxy. They still thought that the event was caused by a supernova.

However, 13 years later in 2013, the burst of light appeared again in the same location. That showed that it was not in fact caused by a supernova, as those events happen just once when a star dies and its core collapses. The source of the burst was reclassified as a Luminous Blue Variable (LBV), a type of massive star which displays dramatic variations in brightness over time. More outbursts of light were discovered stemming from the LBV in 2014, 2017, 2018, and again in February this year. The star could eventually explode in a supernova, but astronomers have no way to predict when this may happen.

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