After reading the article that addresses some good points and info about comets I pass this along. My observation. Allen's Astrophysical Quantities, Fourth Edition, 2000 indicates the Oort cloud could contain 10^11 to 10^13 comets with distances some 10^3 to 10^5 au or more from the Sun for the Oort cloud comets, p. 321. Page 322 shows 1009 comets documented in 1998. The updated space.com report figure is 3743 comets documented now. The space.com report says, "Comets are icy bodies of frozen gases, rocks and dust left over from the formation of the solar system about 4.6 billion years ago." This is not a fact but a model dependent interpretation using the Oort cloud to reconcile comet short lifetimes in the solar system with the radiometric ages of meteorites used since Clair Patterson work in mid-1950s. An example. A model comet using Jean Meeus algorithms with a = 200 au, e = 0.996, mass ~ 6 x 10^16 g, the comet period about 2828.6 years. Perihelion ~ 0.8 au, aphelion ~ 399.2 au. In one-billion-year time span, the comet could complete more than 353,000 perihelion passages. So, the space.com report mixes *facts* with *theoretical model* interpretation in places like the postulated 4.6-billion-year history for comets observed today and the Oort cloud. The article stated about the number of comets, “Though billions more are thought to be orbiting the sun beyond Neptune in the Kuiper Belt and the distant Oort cloud far beyond Pluto.” References to the Oort cloud that could contain as many as 10^13 comets today present a model interpretation, not a fact. In 1998 1,009 comets documented according to Allen's Astrophysical Quantities, Fourth Edition. Today space.com reports 3743 comets documented. These are facts based upon recorded observations.
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