Joel Kontinen
Short-term comets are an enigma for the conventional 4.6 billion year age of the Solar System. As they pass near the Sun, they lose much of their material. They will eventually break up completely. And it would probably be a big mistake to think that long-term comets could last for millions of years, either.
Seven years ago, I wrote a blog post in which I called comets the Ugly Ducklings of a Young Solar System.
Last year, the comet ISON became, in the words of a recent Nature news article, “a scientific celebrity”:
“As ISON sailed into the inner Solar System, expectations grew quickly among astronomers and amateur skywatchers. Many hoped that it might survive its close passage to become a dramatic sight in the night sky — and continued fodder for scientific study. Instead, the comet disintegrated spectacularly in November, just hours before it was set to sweep past the Sun.”
The problem with these Ugly Ducklings is that they are no Methuselahs, but tend to die sooner than we would expect.
Nature news put a billions-of-years spin on the news of ISON’s break-up. In doing so, the article invoked the mythical Oort Cloud:
“It hailed directly from the Oort cloud, the icy reservoir of comets beyond the orbit of Pluto. It spent most of its life in this cloud until perhaps a few million years ago, when the gravity of a passing star nudged it into a new orbit.”
An accompanying text underlined the belief in billions of years:
“After billions of years hanging out in the distant Oort Cloud, ISON plunged into the inner Solar System last year.”
And in case someone missed the message, the article quoted astrophysicist Karl Battam, who said: “Born 4.5 Billion BC, Fragmented Nov 28, 2013”.
Sic transit gloria mundi. But, then, even when it comes to long-term comets, these Ugly Ducklings are evidence for a much younger age of the Solar System.
Source:
Witze, Alexandra. 2014. Astronomy: Death of a comet. Nature news.(19 February).
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