2025年4月7日
NGC 4414: A Flocculent Spiral Galaxy
Image Credit: ESA/Hubble & NASA, O. Graur, S. W. Jha, A. Filippenko
Explanation: How much mass do flocculent spirals hide? The featured image of flocculent spiral galaxy NGC 4414 was taken with the Hubble Space Telescope to help answer this question. Flocculent spirals — galaxies without well-defined spiral arms — are a quite common form of galaxy, and NGC 4414 is one of the closest. Stars and gas near the visible edge of spiral galaxies orbit the center so fast that the gravity from a large amount of unseen dark matter must be present to hold them together. Understanding the matter and dark matter distribution of NGC 4414 helps humanity calibrate the rest of the galaxy and, by deduction, flocculent spirals in general. Further, calibrating the distance to NGC 4414 helps humanity calibrate the cosmological distance scale of the entire visible universe.
Tomorrow’s picture: Moon sisters
NGC 4414: 絮状的螺旋星系
影像提供: ESA/Hubble & NASA, O. Graur, S. W. Jha, A. Filippenko
说明: 絮状螺旋星系到底藏了多少质量？这幅由哈勃太空望远镜所拍摄的絮状螺旋星系NGC 4414之真色主题影像，就是想为回答这个问题提供助力。絮状螺旋星是一种没有鲜明螺旋臂的螺旋星系，这种形态的星系其实蛮常见的，其中的NGC 4414是离我们最近的一个。位于螺旋星系可见边缘的恒星和云气，通常会以非常高的速度绕中心旋转，而星系得有大量不可见的暗物质，才能产生足够的引力来维系这种运动。厘清NGC 4414之内的物质与暗物质之分布，有助于人类校准此星系的其他成分，并可推及其他絮状螺旋星系。更进一步来说，测定NGC 4414的距离，有助于人类校准整个可见宇宙的距离尺标。
明日的图片: Moon sisters
