The more astronomers study the heavens, the more they realize: our solar system is weird."There are a few things that make the solar system kind of strange." Lauren Weiss, an astrophysicist at the University of Montreal. "One of which is we have a giant planet. Only about 10 percent of sunlike stars have a giant planet. And there are probably even fewer that have two giant planets."In addition to giant Jupiter and lesser giant Saturn, we have tiny Mercury—just a bit bigger than Earth's moon.So if we're weird, what does a typical solar system look like? Weiss and her team trained their telescopes on 355 star systems known to host a handful of small exoplanets. And they found that most of the planets within individual star systems tended to be similar in size.
"So if I'm a planet, and I'm, say, two times the size of Earth, my neighbor, the next planet over, is also likely to be two times the size of Earth, give or takea little bit."And they were strung out at similar distances from each other too...like peas in a pod, she says. Compared to that orderly array, our system looks more like, "Uh let's see, if I stick with food...I don't know...like a whole Thanksgiving dinner or something?"The results are in The Astronomical Journal.As for hunting for habitable worlds: "If we're trying to find an Earth-sized planet in the habitable zone"—not too close to the star but not too far away either—"and we find an Earth-sized planet closer in, it might be worthwhile to continue searching for planets around that star."Because there might just be a few more peas in the pod.
天文學家對宇宙的研究越多就越意識到：我們的太陽系非常奇怪。「有幾件事讓太陽系變得有些奇怪。」蒙特婁大學的天體物理學家勞倫·韋斯說道。「其一，太陽系有一顆巨行星。在類似太陽的恆星中，只有約10%擁有巨行星。」擁有兩顆巨行星的恆星可能更少。除了巨大的木星和較小一些的土星之外，太陽系還有小型行星水星——其體積只比月亮稍大一些。因此，如果我們的太陽系很奇怪，那典型的太陽系是什麼樣的呢？韋斯和團隊用望遠鏡觀察了355個星系，這些是已知擁有少量小型系外行星的星系。他們發現，獨立星系中大多數行星的體積大小往往很相似。「所以，如果我是一顆行星，體積是地球的兩倍，那我旁邊行星的體積很可能也是地球的兩倍，誤差只有一點兒。」她說，這些行星排成一排，彼此之間的距離也相似，就像豆莢中的豌豆一樣。與那種有序排列相比，我們的太陽系看起來更像是……「嗯，讓我想想，如果用食物來形容……我不知道……可能就像完整的感恩節晚餐之類的吧？」這項研究結果發表在《天文學期刊》上。至於尋找宜居世界：「如果我們試圖在宜居地帶尋找地球大小的行星」，既不會離恆星太近也不會離得太遠，「然後我們發現了與地球大小接近的行星，那可能繼續搜尋其周圍的行星是值得的。」因為「豆莢」中可能有更多的「豌豆」。