Comet Elenin – the final prospect
Author: Leonid Elenin
September 3rd, 2011 |
Translation by Autumnson Blog
As many readers already know, Comet Elenin has begun the irreversible process of breaking up. We spoke earlier about the probablility of such an outcome, but I considered it less than 50%. On the graph above you can see a selection of ten comets that approach the Sun closer than 0.5 a.u. The red line shows the boundary, to the left of which, derived from J. Bortle’s formula, is the safe zone, but to the right is the zone of disintegration. The yellow color shows Comet Elenin, with absolute magnitude obtained by visual observations, and the blue is from JPL-NASA data. As we see, Bortle’s formula, all-in-all, doesn’t work too badly. Although there is a bright exception – the green triangle belongs to the unique comet 96P/Machholtz, about which I will speak next time.
正如很多讀者已經知道，彗星Elenin已開始不可逆轉的解體過程。早些時候我們談過這結果的可能性，但我認為機會不到50％。在上邊的圖你可看到一套十顆彗星在朝向太陽近至少於0.5 AU。紅線顯示邊界，從它向左，出自 J. Bortle的公式，是安全區域；但向右邊是解體區域，黃色顯示彗星Elenin，與得自視覺觀察的絕對星等，及藍色是來自美國宇航局噴氣推進實驗室的數據。正如我們所見到，Bortle的公式，所有於一切，表現並不太差。雖然有一個光亮的例外 - 綠色三角形屬於獨特的彗星96P/Machholtz，關於此我將在下一次講及。
Now it is absolutely clear that the comet’s drop in brightness, first noted by Michael Mattiazzo on Aug. 20th, was not coincidental – the decay process had already begun, and over the course of the next several days the comet changed greatly. Its pseudo-nucleus became diffuse and extended, and later vanished completely. On images from Sept. 1st in the comet’s coma there was no condensation visible, and that meant the comet had already broken up into fairly small pieces, with a maximum size of not more than a hundred meters.
現在是絕對清楚彗星的亮度在下降，首先由邁克爾 Mattiazzo 在8月20日注意到，那不是巧合 - 衰變的過程已經開始了，和在跟著數天的過程彗星發生很大變化。它的偽核變得四散和伸展，及之後完全消失。從來自 9月1日的圖像在彗星的彗昏沒有見到凝結，而那意味著這顆彗星已經碎裂成頗小塊，最大的尺寸不超過一百米。
Such a breakup of small comets passing near the Sun is not rare, and in that is nothing surprising. I note that this is a breakup, not an explosion. All the pieces continue to move on the comet’s trajectory. The large fragments are likely to continue to disintegrate into smaller ones. It is possible that in October when the comet moves into the morning sky, we will no longer be able to see what once was Comet Elenin. It is possible that something will be visible to large earth-based telescopes. The breakup of a long-period comet fairly close to the Earth (on a Solar System scale) is a rather rare event. During such a breakup we can see the interior of the comet to better understand its construction and composition.
這種小彗星經過太陽附近的破裂並不罕見，而那是不足為奇的。我注意到這是一個分裂，而不是一次爆炸。所有裂塊繼續朝著彗星的軌跡移動，大碎片有可能繼續瓦解成小塊的。它有可能在10月時，彗星進入清晨的天空，我們將不再分得清什麼曾經是彗星Elenin，有可能某些東西將是地球上的大型望遠鏡可見到。一顆長週期頗接近地球（以太陽系尺度）的彗星解體，是一相當罕見的事件。在這樣的解體，我們可看到彗星的內部，以便更好地了解它的構造和組成。
Overall, the most scientifically interesting thing is the breakup scenario, but unfortunately right now the comet is not visible to the largest telescopes or even the Hubble Space Telescope because of its close angular distance from the Sun (small elongation). On the other hand, amateur astronomers, awaiting this comet which might have been visible to the unaided eye, will now not see it, at least visually in their telescopes and binoculars.
We will wait for Sept. 23rd when the comet is due to appear in the field of view of the SOHO space coronagraph. Any result will tell us what we can expect at the beginning of October when the comet once again should appear in the pre-dawn sky. We will wait. The end of this story is near…
我們將等待9月23日當彗星到期出現在SOHO太空日冕的視野，任何的結果都將會告訴我們在十月開始時我們可預期什麼，那時彗星應該會再一次出現在黎明前的天空。我們將拭目以待，這故事的完結近了...
http://spaceobs.org/en/2011/09/03/comet-elenin-the-final-prospect/
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