说明: 火星看起来始终如一吗？不，当地球与火星绕著太阳运行时，由地球上看火星的视直径会不断地改变。上图是2007年至2008年间，在荷兰的恩斯赫德(Enschede)以相同的放大率所拍摄到的30幅火星影像。当地球与火星位於太阳两侧时，火星看起来便小得多。相反地，当地球与火星接近时，火星的影像较大且明亮。近年来火星视角最大的日子发生在2003年八月的冲。由於火星与太阳的距离比地球与太阳的距离远，因此地球上的人们不会看到火星有盈亏的现象。上面的影像中也可以看到火星的北极冰帽，亮暗不同的土壤，云层，以及早期影像中的沙暴。下次的冲，也就是地球与火星再度接近时，将发生在2010年。
转自成大
APOD20080714
Changes in Angular Mars
Credit & Copyright: Richard Bosman
Explanation: Does Mars always appear the same? No. As both Earth and Mars orbit the Sun, the apparent angular size of Mars changes as viewed from the Earth. Pictured above from Enschede, Holland, Mars was captured in 2007 and 2008 with 30 separate images, all taken with the same magnification. When Earth and Mars are on opposite sides of the Sun, Mars appears relatively small. Conversely, when Earth and Mars are near each other, Mars looms large and bright. The largest Mars has appeared in recent history was the opposition of August 2003. Since Mars is always more distant from the Earth from the Sun, Mars never shows a crescent phase to Earthlings. Visible also in the above images are the north polar cap of Mars, dark and light soil, clouds, and, in the early images, a global dust storm. The next opposition, when Earth again passes near to Mars, will occur in early 2010.
[ 本帖最后由 Eldghost 于 2008-7-14 22:44 编辑 ] |
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