美国航空航天局 recently released the spectacular bright image of the firework 星系 NGC 6946 taken earlier by 哈勃 空间 望远镜 (1)
A 星系 是一个系统 星星, remnants of stars, interstellar gas, dust, and dark matter that are bound together by gravitational force. According to an estimate, there are about 200 billion galaxies in the observable 宇宙 (2). The solar system along with the sun is part of the 星系 called Milky Way which is our home 星系.
NGC 6946 (NGC 代表新总目录,这是标记天文物体的常用方法)是距离 7.72 Mpc {1 Mpc 或 Megaparsecs 等于一百万秒差距的星系之一; 在天文学中,首选的距离单位是秒差距 (pc)。 1 秒差距是 1 个天文单位对着 1 秒弧的角度的距离,即 1/3600 度; 在仙王座中,1 pc 等于 3.26 光年}或 25.2 万光年。
星系, NGC 6946 的恒星形成率非常高,因此被归类为 爆 星系. 这种类型的星系的特点是恒星形成率高,大约为 10 – 100 M☉/年远高于正常星系,例如在我们的家乡银河系中,恒星形成率约为1-5 M☉/年 (3) (M☉ 是太阳质量,天文学中的标准质量单位,1 M☉ 大约等于 2×1030 公斤。)。
On our time scale, 星星 appear to be unchanging but on the time scale of billions of years, 星星 undergo a life course, they are born, age and finally die. The life of a star begins in a nebula (cloud of dust, hydrogen, helium and other ionized gases) when the gravitational collapse of a giant cloud give rise to a protostar. This continues to grow further with accretion of gas and dust until it reaches its final mass. The final mass of the star determines its life time (lesser the mass, higher the life span) as well as what happens to the star during its life.
所有类型 星星 derive their energy from nuclear fusion. The nuclear fuel burning in the core creates strong outward pressure due to the high core temperature.This balances out the inward gravitational force. The balance is disturbed when the fuel in the core runs out. Temperature drops, outward pressure diminishes. As a result, the gravitational force of the inward squeeze becomes dominant forcing the core to contract and collapse. What a star finally ends up as after collapse depends on the mass of the star.
In the case of supermassive stars, When the core collapses in a short span of time, it creates enormous shock waves. The powerful and luminous explosion is called supernova. This transient astronomical event occurs during the last evolutionary stage of a supermassive star. The 星系 NGC 6946 is called the 烟花银河 因为仅在上个世纪它就经历了 10 次观测到的超新星。 相比之下,银河系平均每个世纪只有一到两个超新星。 因此,预计在 NGC 6946 星系中存在大量超新星遗迹。 在 NGC 6946 中确定的超新星残余候选者总数约为 225 (4,5)。对于质量超过太阳 10 倍的恒星,残余物将是 黑洞, 中密度最大的物体 宇宙.
The high star-formation rate (starburst), the high rate of supernova events (fireworks) features, spiral structure and it being positioned face-on with us sets this 星系 apart giving rise to its spectacular appearance in the images taken by the 哈勃 望远镜。
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来源
- NASA 2021。哈勃看到令人眼花缭乱的“烟花星系”。 08 年 2021 月 XNUMX 日发布。可在线获取: https://www.nasa.gov/image-feature/goddard/2021/hubble-views-a-dazzling-fireworks-galaxy/ 10 年 2021 月 XNUMX 日访问。
- 美国宇航局 2015 年。哈勃揭示可观测宇宙包含的星系比以前认为的多 10 倍。 可在线获取 https://www.nasa.gov/feature/goddard/2016/hubble-reveals-observable-universe-contains-10-times-more-galaxies-than-previously-thought 10 年 2021 月 XNUMX 日访问。
- Muxlow TWB。,2020 年。星爆星系。 第 8 届欧洲 VLBI 网络研讨会,波兰,26 年 29 月 2020 日至 XNUMX 日。 https://arxiv.org/ftp/astro-ph/papers/0611/0611951.pdf 10 年 2021 月 XNUMX 日访问。
- Long KS、Blair WP 等人,2020 年。在 [Fe ii] 6946 μm 中用 HST* 观测到的 NGC 1.644 的超新星遗迹群。 天体物理学杂志,第 899 卷,第 1 期。DOI: https://doi.org/10.3847/1538-4357/aba2e9
- Radica MC、Welch DL 和 Rousseau-Nepton L.,2020 年。使用 SITELLE 在 NGC 6946 中寻找超新星光回波。 皇家天文学会月刊,第 497 卷,第 3 期,2020 年 3297 月,第 3305-XNUMX 页,DOI: https://doi.org/10.1093/mnras/staa2006
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