Astronomy Picture of the Day

Explanation: If a star in this photograph twinkled slightly, would anyone notice? Would anyone care? Astronomers with the MACHO Collaboration noticed one such twinkle just last week, and many members of the astronomical community now care. The specific type of sparkling of the SMC star in the above cross-hairs clearly indicated a multiple-star microlensing event was in progress. Microlensing is a rare phenomena where gravity itself deflects light so prominently that background sources might appear to have many images and appear many times their normal brightness. Study of the precise details of the latter part of this microlensing event might reveal the mass and distance to the lenses. Were these lenses in the outer reaches of our Galactic halo, this would add evidence to some controversial indications that a good fraction of the normally unseen matter in our Galaxy is composed of lenses only slightly less massive than our Sun.

如果這張照片中的一顆星星稍微閃爍一下，有人會注意到嗎？ 會有人關心嗎？ 上星期，MACHO聯合觀測網的天文學家就注意到了這樣的一例閃爍，現在很多天文界的成員都開始關注。 上圖十字線標定的SMC恆星之特定型態閃爍清楚的顯示，一個多星微透鏡事件正在發生。 微透鏡事件是一種罕見的現象，在這種現象裡，重力本身會使光線發生明顯的偏轉，以至於背景光源可能會出現多重影像，而其視亮度數倍於其正常亮度。 對此微透鏡事件的後半部分之精確細節的研究，可能得以找出透鏡的品質及距離。 如果這些透鏡位於我們銀河系銀暈的邊緣，這將為一些有爭議的跡象提供證據，即我們銀河系中通常不可見的物質中，有相當的一部分是由質量略小於太陽的“透鏡”所組成的。