It’s been nearly 20 years since astronomers first identified a planet outside our solar system. More than 500 exoplanets have been discovered since then, yet it’s not clear if even one of them might be ___1___. Now, astronomer Eric Agol at the University of Washington says we’ve been looking in the wrong places. If we want to find planets that could support life, he says we should look at stars that are dying. He ___2___ that suggestion in the Astrophysical Journal Letters. [Eric Agol, "Transit Surveys For Earths In The Habitable Zones Of White Dwarfs"]
White dwarves are the remnants of stars like our sun that start to cool. But they’re still warm enough to ___3___…if that planet is close enough. Say, 10 to 100 times closer than Mercury gets to the sun. And that proximity is what makes white dwarves so ___4___. To astronomers, anyhow. Because a planet that close to its star would ___5___ the dwarf’s light as it passes. The dimming could be detected by even a puny one-meter telescope.
Agol suggests we survey the 20,000 white dwarves closest to Earth. Finding a planet would give us a good place to look for life. Or maybe someday live.
【视听版科学小组荣誉出品】
habitable floats keep a planet at a nice cozy temperature attractive dim
人类首次发现太阳系外行星距今已有二十余载。这二十多年来，人类已陆续发现了500多个太阳系外行星，但这些行星是否适合居住仍不得而知。华盛顿大学的天文学家艾瑞克•艾戈则表示：我们找错地方了，如果真想找到适合人类居住的星球，就该把目光转移到即将寿终正寝的行星上去。他在《天体物理杂志通讯》上发表了这一观点。 白矮星和太阳一样，同是已经开始冷却的恒星遗迹，不过仍能帮周围的行星维持舒适的温度——只要离得够近的话……比水星离太阳近个10到100倍就差不多了。正是距离产生诱惑，天文学家对白矮星“关爱有加”。因为有距离较近的行星围绕白矮星运转时，白矮星上就会有行星的阴影，这个阴影即使是一米望远镜也能观察得到。 艾戈建议观察离地球最近的20000颗白矮星，只要能在它们周围找到行星，就可能在行星上找到生命迹象，也就可能让它成为下一个“地球”。