Astronomy Picture of the Day—20190225

Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.

2019Feburary 25

Ultimaand Thule

ImageCredit: NASA, Johns Hopkins University APL, Southwest Research Institute

Explanation:On January 1 New Horizons encountered the Kuiper Belt object nicknamed UltimaThule. Some 6.5 billion kilometers from the Sun, Ultima Thule is the mostdistant world ever explored by a spacecraft from Earth. This historic image,the highest resolution image released so far, was made at a range of about28,000 kilometers only 30 minutes before the New Horizons closest approach.Likely the result of a gentle collision shortly after the birth of the SolarSystem, Ultima Thule is revealed to be a contact binary, two connectedsphere-like shapes held in contact by mutual gravity. Dubbed separately by thescience team Ultima and Thule, the larger lobe Ultima is about 19 kilometers indiameter. Smaller Thule is 14 kilometers across.

"天涯海角”

解释：1月1日，新视野号遭遇昵称为“天涯海角”的柯伊伯带天体。距太阳约65亿公里，“天涯海角”是来自地球的飞船曾经探索过的最遥远的世界。这幅历史性的影像，是迄今释放的最高分辨率的影像，是在新视野号最接近“天涯海角”之前仅30分钟时在约28000公里距离上拍摄到的。可能是太阳系诞生之后不久的轻柔碰撞的结果，“天涯海角”被揭示为密近双星，通过共同引力联结在一起的两个相互联系的球形，分别被科学团队命名为“天涯”和“海角”。较大的球瓣“天涯”的直径约为19公里。较小的“海角”为14公里范围。