國家地理:送給外星人的地圖(7)

Scott's new map is a GPS for the ages. It navigates to Earth using pulsars both inside and outside the Milky Way, with a twist.

斯考特的新地圖是能恒久使用的GPS。它運用銀河系以內(nèi)及以外的脈沖星導航至地球。

Instead of the more ordinary pulsars Dad selected, the new map employs millisecond pulsars that spin faster, last longer, and have also-dead orbital companions. These binary pulsars afford a second set of identifiers: the orbital period of the system, which does not change over billions of years. And, crucially, millisecond pulsars age much more slowly than the ones in Dad's map, meaning that it takes thousands of times longer for their spins to become unrecognizable.

與其使用我父親挑選的那些較普通的脈沖星，這幅新地圖運用的是毫秒脈沖星，它們自轉得更快，能存在更久，而且有已經(jīng)死亡的伴星和它們一起在軌道上運行。脈沖星雙星提供了第二組辨識特征：這種系統(tǒng)的軌道周期在數(shù)十億年內(nèi)都不會改變。而且關鍵在于，毫秒脈沖星的衰老速度遠比我父親地圖上的那些脈沖星慢，這意味著在它們的自轉失去辨識度以前，歷時會比過去的脈沖星多數(shù)千倍。

In addition, Scott included another layer of signposts: pulsars in globular clusters orbiting the Milky Way. Ancient clumps of stars that predate the Milky Way, globular clusters are gorgeous and mysterious, and they are veritable millisecond pulsar factories.

此外，斯考特還查了另一層路標：繞行銀河系的球狀星團里的脈沖星。球狀星團是比銀河系更古老的恒星團，既美麗又神秘，而且簡直是制造毫秒脈沖星的工廠。

By including signposts in these hard-to-miss stellar globs outside the galaxy, Scott's map allows Earth to be discoverable for billions of years, even after the Milky Way's stars have trekked around the galactic core multiple times, shuffling their positions and obliterating constellations.

一旦有位于明顯可見的銀河系外球狀星團里的路標，無論銀河系的恒星繞著銀河系核心運行多少圈，改變了它們的位置并導致星座消失，斯考特的地圖仍能讓地球在未來數(shù)十億年內(nèi)被找到。

And Dad, for the record, thinks that's spectacular.

另外在此寫下以資記錄：我父親認為這想法太棒了。