APOD: 2021 September 18

Astronomy Picture Of The Day Explore the cosmos Every day, a new image or photograph of the fascinating universe is presented along with a short explanation by an astronomer. 2021 September 18

Explanation: This Hubble Space Telescope image shows bright, spiky stars in the foreground towards the northern constellation Perseus. It is also well within the Milky Way galaxy. UGC 2885 is a massive spiral galaxy located about 232 million light years away. It is clearly visible beyond. It is 800,000 light years across, compared to the Milky Way's diameter at 100,000 light-years. However, it contains around 1 trillion stars. This is 10 times more stars than the Milky Way. UGC 2885 was part of an investigation into how galaxies grow to enormous sizes. It also formed part of An Interesting Voyage, which included Vera Rubin's pioneering study on the rotation of spiral galaxies. Her research was the first to show convincingly the dominating role of dark matter within our universe.