2025年1月31日
The Variable Nebula NGC 2261
Image Credit & Copyright: Tommy Lease (Denver Astronomical Society)
Explanation: The interstellar cloud of dust and gas captured in this sharp telescopic snapshot is seen to change its appearance noticeably over periods as short as a few weeks. Discovered over 200 years ago and cataloged as NGC 2261, bright star R Monocerotis lies at the tip of the fan-shaped nebula. About one light-year across and 2500 light-years away, NGC 2261 was studied early last century by astronomer Edwin Hubble and the mysterious cosmic cloud is now more famous as Hubble’s Variable Nebula. So what makes Hubble’s nebula vary? NGC 2261 is composed of a dusty reflection nebula fanning out from the star R Monocerotis. The leading variability explanation holds that dense knots of obscuring dust pass close to R Mon and cast moving shadows across the dust clouds in the rest of Hubble’s Variable Nebula.
Tomorrow’s picture: light-weekend
变光星云NGC 2261
影像提供与版权: Tommy Lease (Denver Astronomical Society)
说明: 这幅清晰望远镜影像所呈现的星际尘埃与气体云，其外观在数星期之间就会有明显的变化。发现于200多年前、编录号为NGC 2261的这个扇形星云，扇头镶着亮星麒麟R（R Mon）。NGC 2261的宽度约有1光年，距离我们约2,500光年远，在上世纪初，因天文学家哈勃曾对它进行研究，故这团谜样的宇宙云有哈勃变光星云（Hubble’s Variable Nebula）之称。那么，为何哈勃星云会变光呢？NGC 2261是个尘埃反射星云，扇形的顶端为麒麟R。最可信的变光假说认为，麒麟R附近在移动的致密不透光尘埃结，把影子投射在尘埃云上，造成我们见到的变光现象。
明日的图片: light-weekend
