A Bright Nova in Cassiopeia
Image Credit & Copyright: Chuck Ayoub
Explanation: What’s that new spot of light in Cassiopeia? A nova. Although novas occur frequently throughout the universe, this nova, known as Nova Cas 2021 or V1405 Cas, became so unusually bright in the skies of Earth last month that it was visible to the unaided eye. Nova Cas 2021 first brightened in mid-March but then, unexpectedly, became even brighter in mid-May and remained quite bright for about a week. The nova then faded back to early-May levels, but now is slightly brightening again and remains visible through binoculars. Identified by the arrow, the nova occurred toward the constellation of Cassiopeia, not far from the Bubble Nebula. A nova is typically caused by a thermonuclear explosion on the surface of a white dwarf star that is accreting matter from a binary-star companion — although details of this outburst are currently unknown. Novas don’t destroy the underlying star, and are sometimes seen to recur. The featured image was created from 14 hours of imaging from Detroit, Michigan, USA. Both professional and amateur astronomers will likely continue to monitor Nova Cas 2021 and hypothesize about details of its cause.
Tomorrow’s picture: Jupiter happy
说明: 仙后座内的那个新光斑是什么？一例新星。虽然宇宙各处经常出现新星，但这例名为仙后新星2021（或称V1405 Cas），上个月在地球的天空中，不寻常的增亮到肉眼可见的程度。仙后新星2021维持在相当明亮的状态将近1星期，然后暗去，不过目前又小幅复亮，成为用双筒望远镜即可见的天体。影像中以箭头标示的这例新星，出现在仙后座方向，离气泡星云不远之处。新星的成因，通常是双星系统内的白矮星，吸积来自伴星的物质，最后其表面发生热核爆炸，不过这类爆发的详细过程目前仍不明。新星爆发并不会摧毁其下方的恒星，而且有些是复发新星。这幅摄于美国密西根州底特律的主题影像，曝光的时间则长达14小时。不管专业或业余天文学家，将会持续监测仙后新星2021，同时并揣测其详细的成因为何。 （Nova Cas 2021 仙后新星2021）
明日的图片: Jupiter happy