Astronomy Picture of the Day

Explanation: In the old days, just over a year ago, astronomers had little idea of the true distance to gamma-ray bursts. Did these enigmatic explosions occur in our outer Galaxy, or in the outer Universe? Last May, a first telling distance measure was made - GRB 970508 showed an absorption line with a redshift of about 0.8 - indicating that this gamma-ray burst (GRB) was an enormous distance away. Skeptics, however, are not always convinced by an unrepeated measurement. Since then, though, other tantalizing coincidences have occurred: GRB 971214 occurred unusually near a galaxy with the enormous redshift of 3.4, and GRB 980425 occurred unusually near a peculiar low-redshift supernova. Skeptics were intrigued. Now, the potentially definitive implications of the above-pictured optical transient might impress even the cautious. GRB 980703's optical transient shows a well-measured redshift from both an absorption line and an emission line: 0.97. The above negative highlights the uncommon transient source with the label "OT", while letters designate common comparison stars.

在過往的年代（其實就近在一年多之前），天文學家對伽馬射線暴的真實距離幾乎一無所知。 這些神秘的爆炸是發生在我們星系的外圍，還是在宇宙的邊緣呢？ 去年5月，首次進行首次解謎的距離測量，GRB 970508有一條紅移約為0.8的吸收線，結果顯示這個伽馬射線暴（GRB）的距離極遠。 然而，懷疑論者並不會為單一例的測量結果買單。 不過，從那時起，其他讓人心安的事件也出現了： GRB 971214發生在紅移為3.4的龐大星系附近，而GRB 980425則出現在奇特的低紅移超新星附近。 懷疑論者也對此非常關注。 而在目前，圖示的這例光學瞬變事件之潛在定錘意涵，可能連生性謹慎者也會印象深烙。 GRB 980703的光學瞬態有各一道可精確定出紅移的吸收線和發射線，其紅移為0.97。 在上面這張負片裡，以"OT"標示這個不尋常的瞬變源，而其他字母則標記常見的對比星。