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A spiral and a star
This NASA/ESA Hubble Space Telescope Picture of the Week features a sparkling spiral galaxy paired with a prominent star, both in the constellation Virgo. While the galaxy and the star appear to be close to one another, even overlapping, they’re actually a great distance apart. The star, which is marked with four long diffraction spikes, is in our own galaxy. It’s just 7109 light-years away from Earth. The galaxy, which is named NGC 4900, lies about 45 million light-years from Earth.
This image combines data from two of Hubble’s instruments: the Advanced Camera for Surveys, which was installed in 2002 and is still in operation today, and the older Wide Field and Planetary Camera 2, which was in use from 1993 to 2009. The data used here were taken more than 20 years apart for two different observing programmes — a real testament to Hubble’s long scientific lifetime!
Both programmes aimed to understand the demise of massive stars. In one, researchers studied the sites of past supernovae, aiming to estimate the masses of the stars that exploded and investigate how supernovae interact with their surroundings. NGC 4900 was selected for study because it hosted a supernova named SN 1999br.
In the other programme, researchers laid the groundwork for studying future supernovae by collecting images of more than 150 nearby galaxies. After a supernova is detected in one of these galaxies, researchers can examine these images, searching for a star at the location of the supernova. Identifying a supernova progenitor star in pre-explosion images gives valuable information about how, when and why supernovae occur.
[Image Description: A spiral galaxy seen face-on. Broken spiral arms made of blue patches of stars and thin strands of dark dust swirl around the galaxy’s centre, forming a broad, circular disc. An extended circular halo surrounds the disc. The centre is a brightly-glowing, stubby bar-shaped area in a pale yellow colour. A bright star in our own galaxy, with long cross-shaped diffraction spikes, is visible atop the distant galaxy.]
