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On 12/12/2020 7:29 PM, Jerry wrote:>
> Radio show of December 14, 2020 possible agenda

Monday, December 14
>    New Moon occurs today at 8:17 A.M. PST — and with it comes the last total solar eclipse of the year, visible from Chile and Argentina.
>    The total path length of this eclipse is 9,239 miles (14,869 km), but only 5 percent of this path falls on land. Fortunately, that 5 percent is where the eclipse’s longest duration of 2 minutes 10 seconds occurs, near Sierra Colorada, Argentina, at 4:13 P.M. UT.
    Total solar eclipses occur when the Moon passes between Earth and the Sun, blocking our star from view and allowing us to see its tenuous outer atmosphere, the corona. But another condition must be met — the Moon must be the right distance away from Earth in its orbit to completely cover the Sun. Because the Moon’s orbit is slightly elliptical, if it is too far from Earth when it passes between us and our star, it doesn’t appear large enough to completely block the Sun. When this happens, we see an annular solar eclipse, during which an outer ring of the Sun’s surface remains visible.
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> Tuesday, December 15
>    The constellation Perseus the Hero is high in the sky several hours after sunset. He’s home to the famous Double Cluster, comprising NGC 869 and NGC 884 (also called H and Chi [χ] Persei). From a dark location — and with no Moon, like tonight — you may be able to spot them with the naked eye. In fact, early observers first cataloged this pair around 130 B.C.
>    Start your search at Perseus’ alpha star, Mirfak, which glows at magnitude 1.8. Look north-northwest of Mirfak to find magnitude 2.9 Gamma (γ) Persei, then north-northwest again to find magnitude 3.8 Eta (η) Persei. The Double Cluster sits about 4° northwest of this star and will likely appear as one or two fuzzy patches to your unaided eye.
>    Binoculars or a telescope will bring out these open clusters’ myriad stars. Each contains several hundred young suns some few million to 10 million years old — extremely young by stellar standards.
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> Wednesday, December 16
    Look southwest after sunset for a triple treat tonight: The thin crescent Moon lies less than 6° southwest of bright Jupiter and Saturn. Our satellite shares the constellation Sagittarius with the solar system’s largest planet, while Saturn stands just over the invisible border in Capricornus. Look first at the Moon to see if you can spot the earthshine effect — sunlight reflecting off Earth and illuminating the portion of the Moon still in shadow.
>    The Moon also provides a perfect tool for comparison. Tonight, the ringed planet (magnitude 0.6) is just 0.5° from Jupiter (magnitude –2) — that’s the width of the Full Moon in the sky. But they’re going to get even closer. On the night of the winter solstice next week, the pair will form a nearly indistinguishable “star” in the sky as they come within 0.1° of each other. In a low-power binocular or telescope field, you’ll be able to see both in a single view. This is a sight you won’t want to miss, so begin planning your observations now.
>    Later tonight, the Moon will pass 3° south of Jupiter at 8 P.M. PST. Our satellite will then pass 3° south of Saturn at midnight EST.
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> Thursday, December 17
>    Bright Vega in Lyra is hard to miss in the evening sky, blazing in the northwest after sunset. Although this magnitude 0 luminary far outshines the other stars in its constellation, there are many more reasons to explore the rest of the Harp.
>    One is Sheliak (Beta [β] Lyrae), a multiple-star system that sits 6° south-southeast of Vega. Through binoculars or a small scope, you can easily resolve a magnitude 3.6 primary and a magnitude 6.7 secondary separated by 45". Furthermore, the brighter star, Beta A, is an eclipsing binary (think Algol in Perseus), swinging between magnitude 3.3 and 4.3 in a little less than 13 days as its companion passes in front of and behind it. At maximum, Beta is closest in brightness to nearby Gamma (γ) Lyrae, about 2° to its east. At minimum, it better matches Zeta (ζ) Lyrae, 4.5° north.
>    Zeta is also a multiple-star system, comprising as many as seven stars. Through binoculars, you can easily separate Zeta A and B — A is the brightest at magnitude 4.3, while B is a dimmer magnitude 5.6 and sits 44" away from its companion.
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> Friday, December 18
>    Zoom in on the Moon today for a look at an interesting crater doublet: Messier and Messier A. You’ll find our satellite low in the south at sunset, but there are a few hours of darkness to observe before it sinks below the horizon around 9 P.M. local time.
>    Look with a telescope toward the Moon’s eastern limb, along its equator. There you’ll find the large crater Langrenus, with its distinctive central peaks. To the northwest of this crater is a small pair of impacts; the westernmost pockmark has a distinctive cometlike trail of debris spreading farther west. These are Messier and Messier A, named for the famous 18th-century comet hunter Charles Messier. The pair’s strange appearance is attributed to a single impact that struck the Moon at a low angle and essentially skipped once along the surface.
>    Bump your magnification up to 100x and you’ll see the Messier doublet is distinctly out of round when compared with its fellow craters. Come back over the next few nights for even better views of its one-way rays, as the changing Sun angle brings them into even better contrast.
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>
> The Big Show is Coming Up
> The gas giant planets, Jupiter snd Saturn will be in conjunction (appear close together in the sky) on December 21, a week from today, but before our next radio show. But the are worth observing and imaging starting now for the next two weeks. The planets and their moons, the four Galilean moons of Jupiter and at least Titan with Saturn, will all fit in the same telescopic field of view of small telescopes and binoculars. The last time such a close conjunction was easily observable was in 1226. If you want to wait for their next very close conjunction, it will be on March 15, 2080, but only briefly visible in the predawn sky.
>    With the pandemic, the SBAU is not able to host any public viewing events. People who want to see the conjunction should find a spot with a clear horizon to the southwest. Sunset will be around 4:53 PM PST, and at that time Jupiter and Saturn will be visible in the southwest at an altitude of 22 degrees above the horizon, about twice the apparent width of a fist held at arm's length. They will set around 7 PM.
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> Exo-Planet 9?
>    A planet in an unlikely orbit around a double star 336 light-years away may offer a clue to a mystery much closer to home: A hypothesized, distant body in our solar system dubbed "Planet Nine."
>    This is the first time that astronomers have been able to measure the motion of a massive Jupiter-like planet that is orbiting very far away from its host stars and visible debris disk. This disk is similar to our Kuiper Belt of small, icy bodies beyond Neptune. In our own solar system, the suspected Planet Nine would also lie far outside of the Kuiper Belt on a similarly strange orbit. Though the search for a Planet Nine continues, this exoplanet discovery is evidence that such oddball orbits are possible.
> "This system draws a potentially unique comparison with our solar system," explained the paper's lead author, Meiji Nguyen of the University of California, Berkeley. "It's very widely separated from its host stars on an eccentric and highly misaligned orbit, just like the prediction for Planet Nine. This begs the question of how these planets formed and evolved to end up in their current configuration."
>    The system where this gas giant resides is only 15 million years old. This suggests that our Planet Nine—if it does exist—could have formed very early on in the evolution of our 4.6-billion-year-old solar system.
>    The 11-Jupiter-mass exoplanet called HD 106906 b was discovered in 2013 with the Magellan Telescopes at the Las Campanas Observatory in the Atacama Desert of Chile. However, astronomers did not know anything about the planet's orbit. This required something only the Hubble Space Telescope could do: Collect very accurate measurements of the vagabond's motion over 14 years with extraordinary precision. The team used data from the Hubble archive that provided evidence for this motion.
>    The exoplanet resides extremely far from its host pair of bright, young stars—more than 730 times the distance of Earth from the Sun, or nearly 6.8 billion miles. This wide separation made it enormously challenging to determine the 15,000-year-long orbit in such a relatively short time span of Hubble observations. The planet is creeping very slowly along its orbit, given the weak gravitational pull of its very distant parent stars.
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>    How did it get there?
>    So how did the exoplanet arrive at such a distant and strangely inclined orbit? The prevailing theory is that it formed much closer to its stars, about three times the distance that Earth is from the Sun. But drag within the system's gas disk caused the planet's orbit to decay, forcing it to migrate inward toward its stellar pair. The gravitational effects from the whirling twin stars then kicked it out onto an eccentric orbit that almost threw it out of the system and into the void of interstellar space. Then a passing star from outside the system stabilized the exoplanet's orbit and prevented it from leaving its home system.
>    Using precise distance and motion measurements from the European Space Agency's Gaia survey satellite, candidate passing stars were identified in 2019 by team members Robert De Rosa of the European Southern Observatory in Santiago, Chile, and Paul Kalas of the University of California.
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>    A target for the Webb Telescope
>    Scientists using NASA's upcoming James Webb Space Telescope plan to get data on HD 106906 b to understand the planet in detail. "One question you could ask is: Does the planet have its own debris system around it? Does it capture material every time it goes close to the host stars? And you'd be able to measure that with the thermal infrared data from Webb," said De Rosa. "Also, in terms of helping to understand the orbit, I think Webb would be useful for helping to confirm our result."
>    Because Webb is sensitive to smaller, Saturn-mass planets, it may be able to detect other exoplanets that have been ejected from this and other inner planetary systems. "With Webb, we can start to look for planets that are both a little bit older and a little bit fainter," explained Nguyen. The unique sensitivity and imaging capabilities of Webb will open up new possibilities for detecting and studying these unconventional planets and systems.
>    The team's findings appear in the December 10, 2020, edition of The Astronomical Journal.
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>
> Hubble Catches Rapid Fading Of A Disappearing Nebula   
>    Hubble has revealed the drastic fading of a nebula, capturing it going through unprecedented changes over a 20-year period. When it comes to objects of the cosmos, we’re more used to thinking of changes in terms of millions, if not billions, of years, not decades.
>    The nebula Hen 3-1357, better known as the Stingray nebula, was already an exciting discovery. Hailed as the youngest known planetary nebula in 1998 when Hubble first peeked inside its central star’s final stages of life, now it’s been caught doing something that even the Hubble team are calling “weird”.
>    Photographed by Hubble in 1996, the nebula’s bright blue tendrils and filaments of gas at its center meant it popped against its dark dramatic background, its wavy edges giving it its stingray moniker. Now archival data shows that by 2016, the nebula had dimmed and its wavy edges had almost disappeared.
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>    “This is very, very dramatic, and very weird,” said Hubble member Martín A. Guerrero in a statement. “What we’re witnessing is a nebula’s evolution in real-time. In a span of years, we see variations in the nebula. We have not seen that before with the clarity we get with this view.”
>    The dimming is down to changes in the light emitted by the glowing hydrogen, nitrogen, and oxygen being emitted by the dying star at its center. According to researchers, the oxygen emission dropped by a factor of nearly 1,000 over the two decades.
>    “Changes in nebulae have been seen before, but what we have here are changes in the fundamental structure of the nebula,” said Bruce Balick, leader of the new research due to be published in The Astrophysical Journal. "In most studies, the nebula usually gets bigger. Here, it’s fundamentally changing its shape and getting fainter, and doing so on an unprecedented time scale. Moreover, to our surprise, it’s not growing any larger. Indeed, the once-bright inner elliptical ring seems to be shrinking as it fades.”
>    The culprit appears to be the Stingray nebula's central star, SAO 244567, which experienced a rapid rise in temperature, from less than 22,000°C (40,000°F) to 60,000°C (108,000°F), according to a 2016 study based on observations of the nebula between 1971 and 2002. After the star expanded, causing the temperature to drop, the star went through a cooling phase, emitting less ionizing radiation. Hubble effectively caught before and after shots.
>    Now that the star is cooling, it's likely returning to its early stage of stellar evolution that it was experiencing before its temperature jump. It's hard to know what's in store for this nebula with it being so young, but the researchers estimate that at its current rate of fading, it may be barely detectable in just two or three decades.
>    Serendipitously, Hubble was in the right place at the right time to capture the rapid changes which, in cosmic terms, occurred in just the blink of an eye.
> By Katy Evans  > 04 DEC 2020, 17:30