Jets of ionized gas streak across a cosmic landscape from a newly forming star.
NASA, ESA, and B. Reipurth (Planetary Science Institute); Processing: Gladys Kober (NASA/Catholic University of America)
This new NASA Hubble Space Telescope image captures a jet of gas from a forming star shooting across the dark expanse. The bright pink and green patches running diagonally through the image are HH 80/81, a pair of Herbig-Haro (HH) objects previously observed by Hubble in 1995. The patch to the upper left is part of HH 81, and the bottom streak is part of HH 80.
Herbig-Haro objects are bright, glowing regions that occur when jets of ionized gas ejected by a newly forming star collide with slower, previously ejected outflows of gas from that star. HH 80/81’s outflow stretches over 32 light-years, making it the largest protostellar outflow known.
Protostars are fed by infalling gas from the surrounding environment, some of which can be seen in residual “accretion disks” orbiting the forming star. Ionized material within these disks can interact with the protostars’ strong magnetic fields, which channel some of the particles toward the pole and outward in the form of jets.
As the jets eject material at high speeds, they can produce strong shock waves when the particles collide with previously ejected gas. These shocks heat the clouds of gas and excite the atoms, causing them to glow in what we see as HH objects.
HH 80/81 are the brightest HH objects known to exist. The source powering these luminous objects is the protostar IRAS 18162-2048. It’s roughly 20 times the mass of the Sun, and it’s the most massive protostar in the entire L291 molecular cloud. From Hubble data, astronomers measured the speed of parts of HH 80/81 to be over 1,000 km/s, the fastest recorded outflow in both radio and visual wavelengths from a young stellar object. Unusually, this is the only HH jet found that is driven by a young, very massive star, rather than a type of young, low-mass star.
The sensitivity and resolution of Hubble’s Wide Field Camera 3 was critical to astronomers, allowing them to study fine details, movements, and structural changes of these objects. The HH 80/81 pair lies 5,500 light-years away within the Sagittarius constellation.
来自一颗新生恒星的电离气体喷流划破宇宙景观。
图片来源: NASA, ESA, and B. Reipurth (Planetary Science Institute); 图像处理: Gladys Kober (NASA/Catholic University of America)
这张全新的NASA哈勃太空望远镜图像捕捉到一股由正在形成的恒星喷射而出的气体射流，横贯幽暗的宇宙空间。画面中沿对角线分布的亮粉色与绿色区域是HH80/81，一对赫比格—哈罗天体，哈勃曾于1995年对其进行观测。左上方的亮斑属于HH 81，而下方的条状结构则是HH 80的一部分。
赫比格—哈罗天体是在新生恒星喷射出的电离气体射流与该恒星先前喷出的、速度较慢的气体外流发生碰撞时形成的明亮发光区域。HH 80/81的外流长度超过32光年，是目前已知规模最大的原恒星外流。
原恒星通过从周围环境坠落而来的气体获得供给，其中一部分可在环绕恒星的残余吸积盘中看到。吸积盘内的电离物质会与原恒星强大的磁场相互作用，使部分粒子被引导向两极，并以喷流的形式向外射出。
当喷流以极高速度抛射物质时，粒子与先前喷出的气体发生碰撞，会产生强烈的激波。这些激波加热气体云并激发原子，使其发光，从而形成我们所看到的赫比格—哈罗天体。
HH 80/81是目前已知最明亮的赫比格—哈罗天体，其能量来源是一颗名为IRAS 18162-2048的原恒星。它的质量约为太阳的20倍，是整个L291分子云中质量最大的原恒星。基于哈勃的数据，天文学家测得HH80/81部分区域的速度超过1000千米每秒，这是在射电和可见光波段中记录到的、来自年轻恒星天体的最快外流。不同寻常的是，这是目前唯一由一颗年轻且极其大质量恒星驱动的赫比格—哈罗喷流，而非通常由年轻低质量恒星产生。
哈勃的广角相机3号所具备的灵敏度和分辨率对研究至关重要，使天文学家能够分析这些天体的精细结构、运动以及随时间发生的变化。HH 80/81位于人马座，距离地球约5500光年。
