December 13 2021 nasa news12/25/2023 Forward scattering by the atmosphere of Venus causes the greatest brightness to occur at a higher angle between the Sun, Venus, and the Earth (called phase angle). Astronomers use the term "greatest brilliance" to distinguish this idealized reflection from the actual greatest brightness. If the atmosphere of Venus reflected light evenly in all directions (called Lambertian reflectance), its greatest brightness would be on Dec. Venus has been brightening as it moves closer to Earth, even though it is also presenting more of a crescent. 7, 2021, the planet Venus is predicted to reach its greatest brightness for this apparition. It is also possible that a larger body in a similar orbit broke apart due to thermal stress or other reasons, producing these two asteroids and the Geminids’ stream. It is possible that two asteroids collided with one another, producing 2005 UD, 3200 Phaethon, and the massive amounts of debris that cause the Geminids each year. There is another asteroid, 2005 UD, that appears to be in a related orbit. There are other possible explanations (and thanks to Bill Cooke at NASA MSFC for providing me with this information a few years ago). One possibility is that this asteroid may have shot out gas and dust in the past when it was close to the Sun. The problem is that it is hard to explain why there is so much dust since we don't see dust coming off this asteroid now. The dust that causes the Geminids appears to come from the asteroid 3200 Phaethon, which has an eccentric 1.4 year-long orbit that takes it out as far as the main asteroid belt and much closer to the Sun than Mercury. The Geminids appear to be one of only two annual meteor showers associated with asteroids rather than comets. The Geminids are relatively slow-moving meteors, entering the Earth's atmosphere at about 35 kilometers per second (78,000 miles per hour). This meteor shower is called the Geminids because the meteors appear to radiate out from the constellation Gemini.
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