NGC 5495旁边的那颗恒星很奇怪
Hubble Spies a Spectacular Spiral Galaxy
Hubble Space Telescope image of the spiral galaxy NGC 5495. Credit: ESA/Hubble & NASA, J. Greene
This spectacular image, by the NASA/ESA Hubble Space Telescope’s Wide Field Camera 3, reveals the stately sweeping spiral arms of the spiral galaxy NGC 5495. NGC 5495, which is located roughly 300 million light-years from Earth in the constellation Hydra, is a Seyfert galaxy, a type of galaxy with a remarkably bright central region. These very luminous cores — known to astronomers as active galactic nuclei — are dominated by the electromagnetic radiation emitted by dust and gas falling into a supermassive black hole.
Astronomers studying supermassive black holes lurking in the hearts of other galaxies captured a series of observations, including this image. Investigating the central regions of galaxies can be especially challenging: as well as the light created by matter falling into supermassive black holes, areas of star formation, and the light from existing stars all contribute to the brightness of galactic cores. Thanks to Hubble’s crystal-clear vision, astronomers were able to disentangle the various sources of light at the core of NGC 5495. This allowed them to weigh its supermassive black hole precisely.
Besides for NGC 5495, two stellar interlopers are visible in this image. One is just outside the center of NGC 5495, and the other is very prominent alongside the galaxy. While they share the same location on the sky, these objects are much closer to Earth than NGC 5495: they are stars from our own Milky Way. The bright stars are surrounded by criss-cross diffraction spikes. These are optical artifacts created by the internal structure of Hubble interacting with starlight.
