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On 9/25/2020 11:34 PM, Jerry wrote:
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> Monday, September 28
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>    Saturn will halt its westward motion, coming to an apparent stop against the background stars at 8 P.M. PDT tonight. It will now begin moving eastward again — although not as quickly as Jupiter. The largest planet in the solar system switched directions September 12 and is tracking east much faster than Saturn. Jupiter will ultimately catch up with the ringed planet December 21 for an extraordinary close conjunction that will bring Saturn (apparently) as close as Jupiter’s own moons.
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>    Our own Moon has pulled away from Sagittarius, where the giant planets now sit, so consider spending some time in this constellation tonight. The tiny dwarf planet Pluto, currently around magnitude 14, lies roughly between Saturn and Jupiter, about 3° west-southwest of Saturn and just under 4° east-southeast of Jupiter. You’ll need at least a small scope and clear skies to see it.
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>    Other celestial delights in Sagittarius to turn your telescope on include numerous star clusters. Open star clusters in this constellation include M18, M21, M23, and M25; globulars include M22, M28, M54, M55, and M75.
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> Tuesday, September 29
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>    The Moon passes 4° south of Neptune at 7 P.M. PDT tonight. You can find the pair in Aquarius the Water-bearer in the southeast at that time, although you’ll need large binoculars or a small scope to catch Neptune’s nearly magnitude 8 glow, especially in the glare of our satellite.
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>    For a planet that’s much easier to spot, look east to find magnitude –2.5 Mars about 16° above the horizon. Currently appearing about 22" across, Mars is headed for a brilliant opposition next month you won’t want to miss.
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>    Between Mars and Neptune on the sky is main-belt asteroid 68 Leto, which reaches opposition 8 P.M. PDT. It’s roughly magnitude 10 — best seen with a telescope. Discovered in 1861, Leto is 76 miles (123 kilometers) across. It’s currently traveling through the constellation Cetus the Whale.
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>    You can find yet another planet, Uranus, by looking 15° east-northeast of Mars, closer to the horizon. The nearer of our solar system’s two ice giants is magnitude 5.7 and should show up in binoculars, though beware the Moon’s nearby glow.
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> Wednesday, September 30
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>    Jupiter’s moons are having a busy week: Callisto’s shadow will begin creeping onto the planet’s disk around 6:04 P.M. PDT tonight. The shadow is so large that it takes roughly 10 minutes to fully slip onto the northeastern limb. Keep your eye on the gas giant overnight and you’ll also see tiny Io reappear from eclipse about 9:03 P.M. October 1. It should spring into view roughly 22" from the Jupiter’s eastern limb.
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>    With a nearly Full Moon tonight, many deep-sky objects are off limits. But it’s a great time to take in one of the summer sky’s most appealing double-star sights: Albireo (Beta [β] Cygni), the head of Cygnus the Swan. Still high overhead tonight, this pair of stars offers contrasting colors of gold and blue. Also known as the UCLA star. The magnitude 3.1 and 5.1 pair has a separation of 34", making the two stars easy to resolve in binoculars. Use a small scope (even 2 inches will do) to really bring out their vivid colors.
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> Thursday, October 1
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>    Mercury reaches greatest eastern elongation (26° from the Sun) at 9 P.M. PDT today. You can spot the solar system’s smallest planet this evening, but you’ll need to be quick — it’s only 3° high in the west-southwest 30 minutes after sunset, but glowing at bright magnitude 0. The planet sets 20 minutes later. By then, some of the brightest stars should be popping out of the twilight: Arcturus, Vega, Deneb, Altair, and near the southern horizon, Fomalhaut. Jupiter and Saturn should appear about the same time.
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>    Full Moon occurs at 2:05 P.M. PDT. Our satellite will rise in the east just moments after sunset and remain visible in the sky all night. It’s the first of two Full Moons this month — the second, called a Blue Moon when two Full phases take place in the same month, will occur October 31.
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> Friday, October 2
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>    Venus and the bright star Regulus in Leo are a mere 0.5° apart an hour before sunrise this morning. The pair rises together in the east around 1:00 A.M. local time, so you’ll have at least three hours to catch the sight. Earth’s sister planet glows a bright magnitude –4.1, which is about 145 times brighter than nearby Regulus. Venus’ disk currently spans about 15"; with magnification, you’ll see it’s a 72-percent-lit crescent. The planet will pass 0.09° south of Regulus at 5 P.M. PDT tonight, and they’ll be 41" apart by next morning.
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>    The Moon passes 0.7° south of Mars at 8 P.M. PDT. At that time, the Red Planet will be on view high in the southeast. Both should be readily visible, thanks to Mars’ brilliance. The dim stars of Pisces around them, however, will likely be washed out by the Moon’s bright light.
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> ISS Dodges Space Junk.
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>    On Tuesday night, the International Space Station (ISS) had to swerve out of the way of a piece of incoming space junk.
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>    It’s the third time this year alone that the ISS has had to pull an evasive maneuver, according to SpaceNews. The junk sailed past without incident, but now NASA Administrator Jim Bridenstine is calling for more funding to help the agency better track and manage the growing sea of dangerous garbage orbiting our planet.
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>    Harvard-Smithsonian Center for Astrophysics astronomer Jonathan McDowell later suggested that it was a piece of an upper stage of a Japanese rocket that launched in 2018 before being left in upper orbit.
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>    The debris object that ISS avoided is now available on SpaceTrack as 2018-084CQ, 46477, from the breakup of Japan's H-2A F40 rocket stage. At 2221:07 UTC it passed within a few km of ISS at a relative velocity of 14 6 km/s, 422 km over the Pitcairn Is  in the S Pacific
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>    The ISS crew used the thrusters of a docked spacecraft to push the station out of the way. The NASA crew hid in a Soyuz spacecraft as a safety capsule, according to SpaceNews, out of what NASA described as an “abundance of caution.”
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> Would you survive having witnessed formation of the Barringer Crater in Arizona?   
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>    If the Barringer Meteor Crater impact event in Arizona occurred in a modern city, it would completely destroy it. As the question implies, distance from the point of impact is directly related to one’s survival. The key to determining a safe distance lies in the energy of the impact event. Estimates of that energy exist, but the range of uncertainty can have significant consequences. If the energy was sufficiently small, one could have had a spectacular view of the impact event from Anderson Mesa, a long volcanic ridge about 15 miles (24 kilometers) west of the crater. However, for some of the larger energy estimates, that location may have been uncomfortably close, if not deadly. I have often thought that a very nice — and safe — vantage point would have been Mount Elden, a towering volcanic dome in Flagstaff nearly 40 miles (60km) northwest of the crater.
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>    The impact produced a shock wave and air blast that radiated across the landscape. If the impact energy was 20 megatons, it was immediately lethal for human-sized animals within 4 miles (6km) of the impact. A sharp change in pressure caused by the shock wave produced severe lung damage within 6 to 7 miles (10 to 12 km) of the impact. Winds were also catastrophic, with speeds in excess of 900 mph (1,500 km/h) within the inner 4-mile-diameter zone and still more than 60 mph (100 km/h) at radial distances of 12 miles (20km). Those winds would have picked up debris and hurled it across the landscape like a shotgun blast. Mammoths, mastodons, and giant ground sloths were among the unfortunate victims of the impact event. Let’s hope we are able to mitigate future events of that size and larger so that we never have an opportunity to witness them from any distance.
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> David Kring
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> Lunar and Planetary Institute, Houston
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> Astronomy Magazine April 27, 2015
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> Life on Venus?
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>    On September 14, 2020, a new planet was added to the list of potentially habitable worlds in the solar system: Venus.
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>    Phosphine, a toxic gas made up of one phosphorus and three hydrogen atoms (PH3), commonly produced by organic life forms but otherwise difficult to make on rocky planets, was discovered in the middle layer of the Venus atmosphere. This raises the tantalizing possibility that something is alive on our planetary neighbor. With this discovery, Venus joins the exalted ranks of Mars and the icy moons Enceladus and Europa among planetary bodies where life may once have existed, or perhaps might even still do so today.
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>    It’s critical to point out that this detection does not mean that astronomers have found alien life in the clouds of Venus. Far from it, in fact.
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>    Although the discovery team identified phosphine at Venus with two different telescopes, helping to confirm the initial detection, phosphine gas can result from several processes that are unrelated to life, such as lightning, meteor impacts or even volcanic activity.
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>    However, the quantity of phosphine detected in the Venusian clouds seems to be far greater than those processes are capable of generating, allowing the team to rule out numerous inorganic possibilities. But our understanding of the chemistry of Venus’ atmosphere is sorely lacking: Only a handful of missions have plunged through the inhospitable, carbon dioxide-dominated atmosphere to take samples among the global layer of sulfuric acid clouds.
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>    There are two possibilities: Either there is some sort of life in the Venus clouds, generating phosphine, or there is unexplained and unexpected chemistry taking place there. How do we find out which it is? We go there and see.