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[TomT]

see attached file to download 18 min audio.

show agenda by JerryW:
On 10/24/2020 2:39 PM, Jerry wrote:
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> Monday, October 26
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>    Asteroid 471 Papagena, currently located in the constellation Cetus the Whale, reached opposition at 11 PM PDT last night. At that time, the tiny world is about 40° high above the southwestern horizon, glowing at magnitude 9.5.
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>    If you’re looking to spot Papagena, the nearest stellar signpost is Mira (Omicron [ο] Ceti), which sits 5° north-northwest of the asteroid. Mira is a famous star in its own right — this “wonderful” luminary is a variable star whose magnitude swings between 2 and 10 over the course of nearly 11 months. Its most recent peak in brightness was earlier this month. Careful, consistent observers can chart its changes by revisiting the star every one to two weeks and comparing its brightness with the stars around it. Binoculars or a telescope will do the trick, depending on your options and your location (i.e., the amount of light pollution).
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> Tuesday, October 27
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>    It’s another early morning for observers, but well worth it to catch the Moon passing 4° south of Neptune at 11 PM PDT (Monday). The pair are in the constellation Aquarius, with two magnitude 4 stars — Psi1 (ψ1) and Phi (φ) Aquarii — between them. Neptune, at magnitude 7.8, requires some decent optical aid to see, especially with the gibbous Moon so close. Its 2"-wide, bluish disk will likely appear as a “flatter” star in your field of view.
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>    The distant ice giant is currently nearly 30 astronomical units, or AU, from Earth. (One AU is the average Earth-Sun distance.) Despite its diminutive appearance through your optics, Neptune is actually 17 times more massive than Earth and nearly 4 times as wide; however, it is only 0.3 times as dense as our planet, owing to its icy, gassy composition when compared to our rocky home.
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> Wednesday, October 28
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>    Like the Force, Saturn’s two-faced moon Iapetus has a light side and a dark side. Currently, that brighter side is turned toward Earth, making the tiny, icy moon a little easier to locate as it orbits the ringed planet.
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>    Tonight, magnitude 0.6 Saturn sits about 5.5° east of magnitude –2.2 Jupiter; both are in the southwest among the stars of Sagittarius. Zoom in on Saturn with a telescope to pick out several of its moons — the largest and brightest, Titan, is just under 2' southwest of the planet. Tenth-magnitude Tethys and Dione float east of the planet, with Dione the farther of the two. Rhea, also magnitude 10, is about 30" due south of the eastern edge of the rings. Enceladus, a challenging magnitude 12, lies just 6" northwest of Tethys.
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>    Look due west of Saturn to find Iapetus, glowing near magnitude 10 and about three times farther from the planet’s disk than Titan. As its dark side rotates back into view next month, the moon will dim; the difference in brightness between its two hemispheres is a little more than a magnitude.
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>    For a less-challenging set of satellites, swing over to Jupiter, where all four Galilean moons are on display. Only Callisto is currently east of the planet; on the western side, Ganymede, Io, and Europa line up (from closest to farthest). The orientation of the moons shows just how perpendicular Jupiter’s poles are to its orbital plane — the giant planet is tilted by a mere 3°, much less than Earth’s 23.5°.
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> Thursday, October 29
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>    The Moon passes 3° south of Mars at 9 AM PDT. By the time the pair has cleared the horizon around sunset, they’re just over 4° apart. You’ll find them in the east, rising as the sky grows darker, with Mars just to the upper right of the Moon. The Red Planet, still a bright beacon two weeks after opposition, glows at magnitude –2.2 and appears 20" across.
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>    By two hours after sunset, the face of Taurus the Bull is peeking above the horizon, with his bright red eye, Aldebaran, popping up shortly after. Look directly above the v of the Bull’s nose to find the Pleiades (M45) sparkling in the shape of a tiny dipper. Although this open cluster is often confused with the Little Dipper, its spoon shape is much smaller and more compact than the asterism, located in the north. The Pleiades is a young cluster containing several thousand stars and about 800 solar masses of material. With the naked eye, you may see as many as 12 of the cluster’s stars; binoculars and telescopes will bring out many more. If you’re an astroimager, turning your camera on the cluster is likely to reveal the nebulosity, or glowing gas, strung between the brightest stars.
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> Friday, October 30
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>    The Moon reaches apogee, the farthest point from Earth in its orbit, at 11:45 AM PDT. It will then sit 252,522 miles (406,395 kilometers) from our planet. Our satellite is 99 percent lit and will delight Halloween revelers tomorrow as a Full Moon to light the spooky holiday.
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>    The nearly Full Moon does, however, make the sky brighter and washes out dimmer stars and deep-sky objects. Tonight is a great night to search out some famous asterisms, though: the Square of Pegasus, the Big and Little Dippers, the Teapot in Sagittarius, and the w shape of Cassiopeia. Also still visible is the Summer Triangle, made up of the three bright stars Deneb, Altair, and Vega. High overhead during summer nights, the Triangle is now lower in the west around 8 P.M. local time. Over the next few months, its stars will set completely by sunset and the Triangle will disappear as the winter constellations come out in full force.
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> IapetusSides.jpeg
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> Dark and light
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> Saturn’s moon Iapetus is markedly brighter on one side than the other. This week, the lighter side is facing Earth.
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> Wolf-Rayet are Us!
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>    Astronomers know that our solar system formed about 5 billion years ago from material left over from previous generations of stars. However, beyond that, it gets a little murky.
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>    The prevailing theory is that a nearby supernova explosion compressed a dense cloud of gas and dust until it collapsed in on itself due to its own gravity. As the cloud condensed, it grew hotter and spun faster. Eventually, the center of the cloud grew so hot it began fusing hydrogen into helium and became the star we lovingly call the Sun.
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>    But according to a study published December 22 in the Astrophysical Journal, the solar system instead may have formed inside the dense shell of an enormous bubble within a giant star. The study not only provides a fantastical scenario for our solar system’s formation, but also addresses a long-standing mystery concerning our solar system’s chemical makeup.
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>    The new theory for how the solar system formed starts with an extremely massive star known as a Wolf-Rayet star. Of all the stars in the universe, these stars burn the hottest. Because they are so hot, they also have exceptionally strong stellar winds.
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>    As a Wolf-Rayet star sheds its outer layers – a normal end-of-life process for a giant star – its strong stellar winds plow through its loosely held cloak of material, forming densely shelled bubbles. According to the study, the solar system could have formed inside of one of these bubbles.
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>    Since such a huge amount gas and dust is trapped inside, “the shell of such a bubble is a good place to produce stars,” said Nicolas Dauphas, co-author of the study and professor of geophysical sciences at the University of Chicago, in a press release. The researchers estimate that this stellar-womb process is so effective that it could account for the formation of 1 to 16 percent of all Sun-like stars.
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>    Although the unconventional theory may seem a bit superfluous, the researchers proposed it because it also addresses a long-standing mystery of the early solar system: Why did it have so much aluminium-26 and so little iron-60 when compared to the rest of the galaxy?
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>    Previous studies of meteorite samples have shown that the early solar system was ripe with the isotope aluminium-26, while other studies have shown it was deficient in the isotope iron-60. However, since supernovae explosions produce both of these isotopes, “it begs the question of why one was injected into the solar system and the other was not,” said Vikram Dwarkadas, co-author of the study and professor of astronomy and astrophysics at the University of Chicago.
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>    This is what brought the researchers to Wolf-Rayet stars, which produce lots of aluminium-26, but zero iron-60.
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> Star Spagettified by a Black Hole
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>    “The idea of a black hole ‘sucking in’ a nearby star sounds like science fiction. But this is exactly what happens in a tidal disruption event,” says Matt Nicholl, a lecturer and Royal Astronomical Society research fellow at the University of Birmingham, UK, and the lead author of the new study. But these tidal disruption events, where a star experiences what’s known as spaghettification as it’s sucked in by a black hole, are rare and not always easy to study. The team of researchers pointed ESO’s Very Large Telescope (VLT) and ESO’s New Technology Telescope (NTT) at a new flash of light that occurred last year close to a supermassive black hole, to investigate in detail what happens when a star is devoured by such a monster.
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>    Astronomers know what should happen in theory. “When an unlucky star wanders too close to a supermassive black hole in the centre of a galaxy, the extreme gravitational pull of the black hole shreds the star into thin streams of material,” explains study author Thomas Wevers, an ESO Fellow in Santiago, Chile, who was at the Institute of Astronomy, University of Cambridge, UK, when he conducted the work. As some of the thin strands of stellar material fall into the black hole during this spaghettification process, a bright flare of energy is released, which astronomers can detect.
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>    Although powerful and bright, up to now astronomers have had trouble investigating this burst of light, which is often obscured by a curtain of dust and debris. Only now have astronomers been able to shed light on the origin of this curtain.
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> “We found that, when a black hole devours a star, it can launch a powerful blast of material outwards that obstructs our view,” explains Samantha Oates, also at the University of Birmingham. This happens because the energy released as the black hole eats up stellar material propels the star’s debris outwards.
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>    The discovery was possible because the tidal disruption event the team studied, AT2019qiz, was found just a short time after the star was ripped apart. “Because we caught it early, we could actually see the curtain of dust and debris being drawn up as the black hole launched a powerful outflow of material with velocities up to 10 000 km/s,” says Kate Alexander, NASA Einstein Fellow at Northwestern University in the US. “This unique ‘peek behind the curtain' provided the first opportunity to pinpoint the origin of the obscuring material and follow in real time how it engulfs the black hole.”
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>    The team carried out observations of AT2019qiz, located in a spiral galaxy in the constellation of Eridanus, over a 6-month period as the flare grew in luminosity and then faded away. “Several sky surveys discovered emission from the new tidal disruption event very quickly after the star was ripped apart,” says Wevers. “We immediately pointed a suite of ground-based and space telescopes in that direction to see how the light was produced.”
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> The Big News of last week...A Fly-by-Grabbing
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>    WASHINGTON — NASA’s OSIRIS-REx spacecraft collected so much material from the surface of the asteroid Bennu that the lid of its sampling head is jammed open, causing material to leak out and changing the agency’s plans for the mission.
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> At a media briefing called by NASA on short notice Oct. 23, three days after the spacecraft touched down on the asteroid, officials said that images taken of the head of the sampling device, called the Touch-And-Go Sample Acquisition Mechanism (TAGSAM), showed material leaking out of the container from a gap in a Mylar diaphragm that is supposed to seal the bottom of the head.
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>    “I am highly confident that TAGSAM was success, that it collected abundant mass: definitely evidence of hundreds of grams of material, and possibly more,” said Dante Lauretta, principal investigator for OSIRIS-REx at the University of Arizona. “My big concern now is that the particles are escaping because we were almost a victim of our own success.”
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>    Those images show a cloud of particles outside of the TAGSAM, floating away from it at about one centimeter per second. He estimated that the material visible for those images had a mass of 5 to 10 grams. He added it is not likely a “steady state” mass loss since the head was moving around when those pictures were taken, helping particles escape through the gap in the diaphragm. Star tracker cameras on the spacecraft, which also detected the particles, saw much less after the head was “parked” on the side of the spacecraft.
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>    The concern that more material might leak out of the sample head, though, has prompted NASA to change plans for the mission. Lauretta said that a maneuver planned for the weekend, where the spacecraft would be slowly spun up to measure the change in its moment of inertia and thus the mass of the sample material, has been canceled. Instead, planning is underway to stow the samples in a canister inside the spacecraft, where they will be sealed for return to Earth.
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> Sent from my iPad