环绕土星北极的极光

环绕土星北极的极光

Aurora around Saturn’s North Pole
Image Credit: NASA, ESA, Hubble, OPAL Program, J. DePasquale (STScI), L. Lamy (Obs. Paris)

Explanation: Are Saturn’s auroras like Earth’s? To help answer this question, the Hubble Space Telescope and the Cassini spacecraft monitored Saturn’s North Pole simultaneously during Cassini’s final orbits around the gas giant in September 2017. During this time, Saturn‘s tilt caused its North Pole to be clearly visible from Earth. The featured image is a composite of ultraviolet images of auroras and optical images of Saturn’s clouds and rings, all taken by Hubble. Like on Earth, Saturn’s northern auroras can make total or partial rings around the pole. Unlike on Earth, however, Saturn’s auroras are frequently spirals — and more likely to peak in brightness just before midnight and dawn. In contrast to Jupiter’s auroras, Saturn’s auroras appear better related to connecting Saturn’s internal magnetic field to the nearby, variable, solar wind. Saturn’s southern auroras were similarly imaged back in 2004 when the planet’s South Pole was clearly visible to Earth.

Your Sky Surprise: What picture did APOD feature on your birthday? (post 1995)
Tomorrow’s picture: how many sisters?

环绕土星北极的极光
影像提供: NASA, ESA, Hubble, OPAL Program, J. DePasquale (STScI), L. Lamy (Obs. Paris)

说明: 土星的极光和地球上的同类雷同吗？为了回答这个问题，在2017年9月时，哈勃太空望远镜和卡西尼号探测器在绕行土星的最后轨道期间，同时监控土星的北极。因为在那段期间，从地球可以清楚见到侧倾土星的北极。这张主题影像，结合了哈勃太空望远镜拍摄的紫外波段极光影像及土星云层和环系的可见光影像。就像地球的同类，土星的北极光可完全或部分环拱北极。不过与地球极光有别的是：土星的极光经常是螺旋状的，而且较可能在子夜和黎明前达到最大亮度。与木星的极光相较，土星极光和土星内部磁场及附近多变的太阳风之关联性较强。在2004年，从地球清楚可见土星的南极之时，也曾拍摄土星的南极光。

你的天空惊喜: 你生日那天APOD展示了什么照片？（1995年后）
明日的图片: how many sisters?