The Hubble Space Telescope captured this amazing image of NGC 1566, a member of the Dorado galaxy group called the Spanish Dancer galaxy. Distinguishing members within such groups presents a complex challenge for astronomers. Credit: ESA/Hubble & NASA, D. Calzetti and LEGUS team, R. Chandar
captured by hubble space telescopethis vivid and dynamic-looking image depicts spiral galaxy NGC 1566, sometimes informally known as the “Spanish Dancer Galaxy.”
Like the subject of another recent Hubble photo of the week, NGC 1566 is a weakly barred or intermediate spiral galaxy, meaning it has neither a clearly present nor an apparently absent bar structure at its center. To do. This galaxy’s nickname comes from the bright, dramatic swirling lines of its spiral arms, which may recall the shapes and colors of the moving figures of dancers. NGC 1566 is located approximately 60 million light-years from Earth in the constellation of Dorado and is also a member of the Dorado Galaxy Group.
Understanding Galaxy Group
A galaxy group is a collection of galaxies bound by gravity. Groups differ from galaxy clusters in size and mass. Galaxy clusters may contain hundreds of galaxies, while groups may contain dozens of galaxies. That being said, there is no exact line between the definitions of a galaxy group and a galaxy cluster. Some astronomers have suggested that the definition be made clearer, with some suggesting that galaxy clusters with less than 80 trillion solar masses should qualify as galaxy groups.
Challenges in identifying Galaxy group members
The Dorado group’s membership has fluctuated over the past few decades, with various scientific papers altering the list of member galaxies. As an example of why it is so difficult for astronomers to pin down members of groups like the Dorado group, we can imagine a photo of an adult and a large oak tree.
We know the approximate size of a person and a tree, so if we see a photo where a person appears to be approximately the same size as the tree, we can infer that the person is actually in that position. . It was much closer to the camera than the tree, giving the false impression that the trees were the same size.
When figuring out the members of a galaxy group, astronomers don’t necessarily have knowledge of the size of individual galaxies, so they have to wonder if the galaxies are actually relatively close to each other in space, or if they are actually We have to find out if some of the galaxies are closer together. Or even further away. Although this has become easier with more sophisticated observation techniques, it can still be a challenge.
