NGC 2419: 星系际的浪流者



NGC 2419: Intergalactic Wanderer
Image Credit:
ESA/Hubble, NASA, S. Larsen et al.

Explanation: Stars of the globular cluster NGC 2419 are packed into this Hubble Space Telescope field of view toward the mostly stealthy constellation Lynx. The two brighter spiky stars near the edge of the frame are within our own galaxy. NGC 2419 itself is remote though, some 300,000 light-years away. In comparison, the Milky Way’s satellite galaxy, the Large Magellanic Cloud, is only about 160,000 light-years distant. Roughly similar to other large globular star clusters like Omega Centauri, NGC 2419 is intrinsically bright, but appears faint because it is so far away. Its extreme distance makes it difficult to study and compare its properties with other globular clusters that roam the halo of our Milky Way galaxy. Sometimes called “the Intergalactic Wanderer”, NGC 2419 really does seem to have come from beyond the Milky Way. Measurements of the cluster’s motion through space suggest it once belonged to the Sagittarius dwarf spheroidal galaxy, another small satellite galaxy being disrupted by repeated encounters with the much larger Milky Way.

Tomorrow’s picture: pixels in space

NGC 2419: 星系际的浪流者
ESA/Hubble, NASA, S. Larsen et al.

说明: 在这幅远眺暗淡天猫座方向的哈勃望远镜影像里,球状星团NGC 2419的成员星挤满整个视野。唯有位在影像边缘的那二颗带芒亮星,是近在我们银河系之内的恒星。NGC 2419相当遥远,离我们将近有300,000光年远。作为比较,银河系的伴星系大麦哲伦星系之距离,大约只有160,000光年。大小约莫和银河系的半人马奥米茄星团等大球状星团相当的NGC 2419,其实很明亮,只因为距离极远所以看起来很昏暗。也因为它很遥远,所以让研究它的特性、并和在银河系银晕里漫游的球状星团作比较,成为一项高难度的工作。NGC 2419有”星系际流浪者”的称号,因为它真的看似来自银河系后方的空间。这个星团在空间运动的量测结果指出,它曾是椭圆球形的人马矮星系之成员,而这个伴星系是在与庞大的银河系近距离反复接近后,被撕碎的数个伴星系之一。

明日的图片: pixels in space