Planets of the Solar System: Tilts and Spins Video Credit: NASA, Animation: James O’Donoghue (JAXA)

Explanation: How does your favorite planet spin? Does it spin rapidly around a nearly vertical axis, or horizontally, or backwards? The featured video animates NASA images of all eight planets in our Solar System to show them spinning side-by-side for an easy comparison. In the time-lapse video, a day on Earth — one Earth rotation — takes just a few seconds. Jupiter rotates the fastest, while Venus spins not only the slowest (can you see it?), but backwards. The inner rocky planets, across the top, most certainly underwent dramatic spin-altering collisions during the early days of the Solar System. The reasons why planets spin and tilt as they do remains a topic of research with much insight gained from modern computer modeling and the recent discovery and analysis of hundreds of exoplanets: planets orbiting other stars.

Tomorrow’s picture: stars and sprites

太阳系的行星：倾角和自转 影片提供: NASA, 动画制作: James O’Donoghue (JAXA)

说明: 你最钟爱的行星如何自转？它绕着几乎直立的轴快速自转呢？还是绕水平轴或什至逆向自转？这部主题影片，把美国国家航空航天局（NASA）拍摄的太阳系 8大行星之影像串成动画，让它们并排自转以方便比较。在这部缩时影片里，地球自转一圈所对应的地球日，只有短短的数秒。行星之中，木星的自转最为快速，而金星的自转最缓慢（见到了没？），而且除了自转轴几乎平躺之外，更是顺时钟逆转。影像上排的石质内行星，在太阳系形成的早期，肯定经历了改变它们自转特性的剧烈碰撞。行星为何以现在方式自转和侧倾，仍然是科学研究的题材。而大部分的洞见，来自近代的电脑模拟，以及分析近来发现的、绕行其他恒星数以百计的系外行星。

明日的图片: stars and sprites