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Download the attached MP3 audio file to listen to the Santa Barbara Astronomical Unit radio program hosted by the Baron Ron Herron on KZSB radio 1290AM

On 1/9/2021 9:42 PM, Jerry wrote:

> Radio Show Of Jan 11, 2021

> This Week
>    Although the universe is vast, galaxies often meet and interact. Such is the case with Bode’s Galaxy (M81) and the Cigar Galaxy (M82), two nearby spirals located about 10° northwest of Dubhe, Ursa Major’s magnitude 1.8 alpha star. The pair is visible in a small scope, whose low power can capture both in a single field of view — they sit roughly 35' apart. Higher power (or larger apertures) will reveal more detail in each, particularly in M81, whose spiral arms become visible under dark skies and greater magnification. The Cigar Galaxy, which gains its name from its long, skinny appearance, is tilted sideways with respect to Earth, meaning its dusty disk is visible edge-on, hiding its spiral arms.
>    After dark, Ursa Major is already climbing higher in the northern sky, with the Big Dipper oriented so the end of its handle touches the horizon. The Great Bear will continue her upward climb as the night progresses, eventually turning onto her back into the early morning as the stars near the North Pole rotate around it.

> Monday, January 11
>    Mercury passes 1.5° south of Jupiter at 3 A.M. PST. The pair is well below the horizon, invisible to observers.
>    Step outside early this morning before sunrise to spot the Moon and Venus sharing the sky in Sagittarius. Our Moon is a delicate crescent just over 3 percent lit, while Venus, less than 4° to its east, is 95 percent lit when viewed through a telescope. The planet is a bright magnitude –4, making it an easy-to-spot morning star.
>    Look about 23° west of Venus and you’ll find not Mars, but its doppelgänger: Antares, the red heart of Scorpius the Scorpion. This star earned its name because its brightness and color so closely match those of the Red Planet. But Mars is visible in the evenings this month; we’ll visit it later this week.
>    The Moon passes 1.5° south of Venus at 12 A.M. PST By tomorrow it will sit east of the planet, and Venus will rise well before our satellite appears in the sky.

> Tuesday, January 12
>    Today marks the end of the Quadrantid meteor shower, which peaked January 3. However, ambitious observers with dark skies may still be able to catch the shower’s last few stragglers. The Quadrantids’ radiant, located in the constellation Boötes, is high in the morning sky just an hour or two before sunrise. At its peak, the shower produced more than 100 meteors per hour, so some additional meteors above the random background level of seven or so per hour are still likely.
>    While you’re up this morning, look again for Venus, now preceding the Moon in the sky. In fact, our young satellite rises shortly before the Sun, by which time Venus is already 10° high. See how long you can follow it in the morning twilight, but avoid using optical aid of any kind after the Sun has risen to prevent accidentally damaging your vision.

> Wednesday, January 13
>    New Moon occurs at 9:00 A.M. PST. Our satellite less than a day old by sunset, but if you have a clear view of the southwestern horizon, it’s worth trying to see it. (Keep in mind, however, that this is a very difficult observation, and unlikely to bear fruit unless conditions are perfect.)
>    By sunset, our Moon is a less-than-1-percent-lit crescent. Search for it 20 to 25 minutes after sunset, when it will be just 1° above the horizon. Mercury, Jupiter, and Saturn are nearby — Mercury is just 6.5° northeast of our satellite, and the innermost planet is now located to the upper right of Jupiter, nearly 3.5° to Mercury’s lower right. Saturn is another 2.5° west of Jupiter, to the gas giant’s lower right. The three form a roughly straight line. Mercury will continue to pull away from the larger planets over the next several days, as the slowly waxing Moon does the same.

> Thursday, January 14
>    The Moon passes 2° south of Mercury at midnight PST; both are below the horizon at that time. Pluto is in conjunction with the Sun at 6. A.M. PST.
>    Also at 6 A.M. PST, Uranus is stationary against the background stars. The penultimate planet in our solar system is located in Aries the Ram, visible after sunset. You can easily pick out its magnitude 5.8 glow with binoculars or a small scope. Its 4"-wide disk will likely appear as a “flat” gray star.
>    Just 3.3° west of the ice giant is a much brighter planet: Mars, also making its way through Aries, shines at magnitude 0.1. Now 9" across, Mars is moving away from Earth along its orbit outside our own. Over the course of January, it will remain in Aries but shrink another 1" and dim a few tenths of a magnitude. Nonetheless, it remains an excellent evening object this month, readily visible in small and
>    If you return to this region of the sky night after night, you’ll see the Red Planet move noticeably northeast each night, passing 1.7° north of Uranus on the 21st. After tonight, Uranus will also begin inching northeast — but because it is much more distant, it appears to move much more slowly across the sky. The ice giant will remain within 4' of its current position all month, even as Mars flies quickly past.

> Friday, January 15
>    The strangely metallic asteroid 16 Psyche is located near Aldebaran, the red giant eye of Taurus the Bull, all month. It’s already well above the horizon at sunset. As soon as darkness falls, pull out your telescope and look 1.5° north of the bright star to find Psyche. Depending on your location, a 4-inch scope may be enough to spot it in a dark sky. Those in the suburbs might want a 6-incher or larger.
>    To positively identify the asteroid, you’ll want to return to this region again and again, noting which point of light has moved. Psyche travels about 6' per day (24 hours), so coming back day after day will show the most motion. The asteroid is currently moving northwest against the background stars. Around the 23rd, it will reverse course, starting to make its way northeast instead.
>    If you’re observing without a telescope, there’s still plenty to enjoy in the sky tonight. Once you’ve located Aldebaran, just slide your gaze about 14° northwest to spot the sparkling Pleiades star cluster. How many of its brightest stars can you count by eye, and can you make out its tiny “little dipper” shape? (Despite its shape, the Pleiades are not the Little Dipper. You’ll find that in the north, stretching outward from our pole star, Polaris.)

> Fun fact:
>    Asteroids can have rings too. Chariklo orbits between Saturn and Uranus and has two icy rings. Discovered by occultation observation.

> Drive by Star Shot
>    Every 50,000 years or so, a nomadic star passes near our solar system. Most brush by without incident. But, every once in a while, one comes so close that it gains a prominent place in Earth’s night sky, as well as knocks distant comets loose from their orbits.
>    The most famous of these stellar interlopers is called Scholz’s Star. This small binary star system was discovered in 2013. Its orbital path indicated that, about 70,000 years ago, it passed through the Oort Cloud, the extended sphere of icy bodies that surrounds the fringes of our solar system. Some astronomers even think Scholz’s Star could have sent some of these objectstumbling into the inner solar system when it passed.
>    However, Scholz’s Star is relatively small and rapidly moving, which should have minimized its effect on the solar system. But in recent years, scientists have been finding that these kinds of encounters happen far more often than once expected. Scholz’s Star wasn’t the first flyby, and it won’t be the last. In fact, we’re on track for a much more dramatic close encounter in the not-too-distant future.
>    “Scholz’s Star probably didn’t have a huge impact, but there should be many more stars that have passed through that are more massive,” astronomer Eric Mamajek of NASA’s Jet Propulsion Laboratory, whose 2015 paper in Astrophysical Journal Letters put Scholz’s Star on the map, tell Astronomy.
>    Around Christmas 2013, Mamajek was visiting a friend and fellow astronomer, Valentin Ivanov, at the offices of the European Southern Observatory in Santiago, Chile. While the two chatted, Ivanov was looking at recent observations of a star cataloged as WISE J072003.20–084651.2.
>    The star caught Mamajek’s interest because it was just about 20 light-years away, but astronomers hadn’t noticed it thanks to its dim nature and tiny apparent movement (or proper motion) across our night sky.
>    To him, those two things were a clue. Since it didn’t appear to be moving much side to side, the star was likely moving toward us or away from us at a breathtaking pace. As the astronomers continued talking, Ivanov measured the star’s radial velocity to learn how quickly it was moving toward or away from our Sun. Soon, they had their answer.
>    “Within five or 10 minutes, we had the initial results that this thing came within a parsec [3.26 light-years] of the Sun,” Mamajek says. “It was screaming through the solar neighborhood.”
>    The two astronomers and their colleagues would eventually show that it passed even closer than that. In fact, it passed closer to our Sun than any other known star. This status prompted them to name the cosmic trespasser after its initial discoverer, an astronomer named Ralf-Dieter Scholz, who’s devoted significant time to finding nearby stars.
>    Mamajek has since moved on from studying Scholz’s Star. But in the meantime, other astronomers have also taken up the work. And, thanks to a European Space Agency satellite called Gaia, which is built to map the precise locations and movements of over a billion stars, we now know about other close encounters.
>    In 2018, a team of researchers led by Coryn Bailer-Jones of the Max Planck Institute for Astronomy in Germany, used Gaia data to plot our Sun’s future meet-ups with other stars. They discovered nearly 700 stars that will pass within 15 light-years of our solar system over just the next 15 million years. However, the vast majority of close encounters have yet to be discovered, the team suggests. But they suspect roughly 20 stars should pass within just a couple light-years of us every million years.
>    However, “space is big,” Mamajek points out. “Statistically, most of those stars would pass the outer edge of our solar system.” That means encounters like the one with Scholz’s Star are common, but only a few are close enough to actually dislodge a significant number of comets,
>    Nonetheless, a few stars should still come surprisingly close. And if a large, slow-moving star did pass through the edge of the Oort Cloud, it could really shake up the solar system.
> starsnextdoor.jpg
> Many nearby stars will pass close to the Oort Cloud, but only one will move through it. In about 1.35 million years, Gliese 710 likely will gravitationally perturb millions of comets, sending a sizable number on a potential collision course with Earth.
> Astronomy: Roen Kelly
>    A massive star steamrolling through the outer solar system is exactly what Gaia data show will happen less than 1.4 million years from now, according to a 2016 study. A star called Gliese 710 will pass within 10,000 astronomical units — 1 AU is equal to the average Earth-Sun distance of 93 million miles. That’s well within the outer edge of the Oort Cloud.
>    At half the mass of the Sun, Gliese 710 is much larger than Scholz’s Star, which is just 15 percent the mass of the Sun. This means Gliese 710’s hulking gravity could potentially wreak havoc on the orbits of icy bodies in the Oort Cloud. And while Scholz’s Star was so tiny it would have been barely visible in the night sky — if at all — Gliese 710 is larger than our current closest neighbor, Proxima Centauri. So when Gliese 710 reaches its closest point to Earth, it will burn as a brilliant orange orb that will outshine every other star in our night sky.
>    This event could be “the strongest disrupting encounter in the future and history of the solar system,” the authors wrote in their paper, published in the journal Astronomy & Astrophysics.
>    Fortunately, the inner solar system is a relatively tiny target, and even if Gliese 710 does send comets flying our way, it would take millions of additional years for these icy bodies to reach us. That should give any surviving future humans plenty of time to take action.

> Was the Sun Half of a Binary?
>    Scientist believe that surrounding the generally flat solar system is a spherical shell comprised of more than a trillion icy objects more than a mile wide. This is the Oort cloud, and it's likely the source of our solar system's long-term comets — objects that take 200 years or more to orbit the Sun. Inside that shell and surrounding the planets is the Kuiper Belt, a flat disk of scattered objects considered the source of shorter-term comets.
>    Long-term comets come at us from all directions and astronomers at first suspected their origins to be random. However, it turns out their likely trajectories lead back to a shared aphelion between 2,000 astronomical units (AU) from the Sun to about 100,000 AU, with their different points of origin revealing the shell shape of the Oort cloud along that common aphelion. (An astronomical unit is the distance from the Sun to the Earth.)
>    No object in the Oort cloud has been directly observed, though Voyager 1 and 2, New Horizons, and Pioneer 10 and 11 are all en route. (The cloud is so far away that all five of the craft will be dead by the time they get there.) To derive a clearer view of the Oort cloud absent actually imagery, scientists utilize computer models based on planetary orbits, solar-system formation simulations, and comet trajectories.
>    It's generally assumed that the Oort cloud is comprised of debris from the formation of the solar system and neighboring systems, stuff from other systems that we somehow captured. However, says paper co-author Amir Siraj of Harvard, "previous models have had difficulty producing the expected ratio between scattered disk objects and outer Oort cloud objects." As an answer to that, he says, "the binary capture model offers significant improvement and refinement, which is seemingly obvious in retrospect: most sun-like stars are born with binary companions."
>    “Binary systems are far more efficient at capturing objects than are single stars," co-author Ari Loeb, also of Harvard, explains. "If the Oort cloud formed as [indirectly] observed, it would imply that the sun did in fact have a companion of similar mass that was lost before the sun left its birth cluster."
>    Working out the source of the objects in the Oort cloud is more than just an interesting astronomical riddle, says Siraj. "Objects in the outer Oort Cloud may have played important roles in Earth's history, such as possibly delivering water to Earth and causing the extinction of the dinosaurs. Understanding their origins is important."
>    The gravitational pull resulting from a binary companion to the Sun may also help explain another intriguing phenomenon: the warping of orbital paths either by something big beyond Pluto — a Planet 9, perhaps — or smaller trans-Neptunian objects closer in, at the outer edges of the Kuiper Belt.
>    “The puzzle is not only regarding the Oort clouds, but also extreme trans-Neptunian objects, like the potential Planet Nine," Loeb says. "It is unclear where they came from, and our new model predicts that there should be more objects with a similar orbital orientation to [a] Planet Nine."
>    The authors are looking forward to the upcoming Vera C. Rubin Observatory (VRO) , a Large Synoptic Survey Telescope expected to capture its first light from the cosmos in 2021. It's expected that the VRO will definitively confirm or dismiss the existence of Planet 9. Siraj says, "If the VRO verifies the existence of Planet Nine, and a captured origin, and also finds a population of similarly captured dwarf planets, then the binary model will be favored over the lone stellar history that has been long-assumed."
>    Lord and Siraj consider it unsurprising that we see no clear sign of the Sun's former companion at this point. Says Loeb, "Passing stars in the birth cluster would have removed the companion from the sun through their gravitational influence. He adds that, "Before the loss of the binary, however, the solar system already would have captured its outer envelope of objects, namely the Oort cloud and the Planet Nine population."