Astronomy Picture of the Day

Explanation: In 1997, Comet Hale-Bopp became much brighter than any surrounding stars. It could be seen even over bright city lights. Out away from city lights, however, it put on quite a spectacular show. Here Comet Hale-Bopp was photographed last March above Val Parola Pass in the Dolomite mountains surrounding Cortina d'Ampezzo, Italy. Comet Hale-Bopp's blue ion tail was created when fast moving particles from the solar wind strike ions expelled from the comet's nucleus. The white dust tail was composed of larger particles of dust and ice expelled by the nucleus that orbit behind the comet. Observations have shown that Comet Hale-Bopp's nucleus spins about once every 12 hours. Comet Hale-Bopp is still visible to those in the right place with a good telescope.

在1997年，海爾-波普彗星遠比它周圍任何恆星都來得亮，甚至透過明亮的都市燈光都能看見它。 而在遠離都市燈光的干擾時，它更是一幅不折不扣的奇景。 這張攝於義大利．科爾蒂納丹佩佐鎮附近多洛米蒂 山脈的Val Parola隘口之海爾-波普彗星影像，即可為證。 影像中，海爾-波普彗星從彗核排出的離子所組成之泛藍離子尾，受到太陽風的吹拂外指。 彗核釋出的較大顆粒塵埃，則受到太陽光壓的推擠，形成散落在彗星後方軌道上的黃白色塵尾。 觀測證實海爾-波普彗星的彗核，大約每12小時旋轉一圈。 對位在合適地點的觀測者，透過好品質的望遠鏡仍然可以看到海爾-波普彗星。