在遥远系外行星上发现的水气

2019 September 17

Water Vapor Discovered on Distant Exoplanet
Illustration Credit: ESA, NASA, Hubble; Artist: M. Kornmesser

Explanation: Where else might life exist? One of humanity’s great outstanding questions, locating planets where extrasolar life might survive took a step forward recently with the discovery of a significant amount of water vapor in the atmosphere of distant exoplanet K2-18b. The planet and it parent star, K2-18, lie about 124 light years away toward the constellation of the Lion (Leo). The exoplanet is significantly larger and more massive than our Earth, but orbits in the habitable zone of its home star. K2-18, although more red than our Sun, shines in K2-18b’s sky with a brightness similar to the Sun in Earth’s sky. The discovery was made in data from three space telescopes: Hubble, Spitzer, and Kepler, by noting the absorption of water-vapor colors when the planet moved in front of the star. The featured illustration imagines exoplanet K2-18b on the right, its parent red dwarf star K2-18 on the left, and an unconfirmed sister planet between them.

在遥远系外行星上发现的水气
影像来源: ESA, NASA, Hubble; Artist: M. Kornmesser

说明：生命还可能存在于何处？这是人类重大且未解的难题之一，近来随着在遥远系外行星K2-18b的大气层中发现了大量水气，确定太阳系外生命可能生存的行星位置又向前迈进了一步。这颗系外行星和它的母星K2-18位于狮子座方向、距离我们约124光年远。它的体积明显比我们地球大，且质量也更大，但它的轨道位于其主星的宜居带上。尽管K2-18比我们的太阳更红，但它在K2-18b天空中的亮度与地球天空中太阳的亮度相近。这一发现是由哈勃、斯皮策和开普勒三架太空望远镜的数据得出的，它们记录了当行星移动到恒星前方时，水气颜色的吸收情况。这幅精彩的插图呈现了位于右侧的系外行星K2-18b，位于左侧的母星红矮星K2-18，以及它们之间一颗未经确认的姐妹行星。