TGT #16 - The Fog Lifts from Our Solar Neighborhood; + 7 more [Jan. 16, 2022]
This Just In: The Dust Around the Sun, Near and Out to 500 Light Years, Star News in the Current Night Sky, What the Milky Way Eats; Finding Uranus--and a Venus-Mars Experiment; Not So Oblique....
Cover Photo - The Local Bubble, From Outside (top), and from Earth
In This Issue:
Cover Photo — The Local Bubble, from Outside and from Earth
This Just In — Stories in the Current Night Sky:
Two Stars Tearing Each Other Apart?
The Demon Star May Have a Family
The Fog Lifts from Our Solar Neighborhood
Halos Are Not a Single Ring, but Many Fragments
Sky Planning Calendar —
* Moon-Gazing - From Full to Almost New, Near Mars and Mercury
* Observing—Plan-et — Are Venus and Mars ‘On the Level?’; Easy Finding of Uranus
* Border Crossings — You are Forecasted to be Lucky if Your Birthday is the 19th
Astronomy in Everyday Life — Merry Obliquity Not <sigh>
The Classroom Astronomer Inbox Magazine Issue 16 Highlights
Welcome to the first 2022 Issue of The Galactic Times Inbox Magazine, #16!
The Galactic Times took a Holiday Hiatus. The next issue will be February 1st.
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This Just In—
* Stories in the Current Night Sky:
Two Stars Tearing Each Other Apart?
You’ll need a telescope just to find this, but no telescope can see this deadly tango. The star Z Canis Majoris, one of the first variable stars ever found in the constellation of the Great Dog, Orion’s larger Hunting Dog, is faint, just slightly brighter than tenth magnitude. It is not only a pre-main sequence star—one still somewhere between fidgety new-born and young and stable—it’s TWO such stars in a tight pair dancing around each other. One is 13 times the mass of our Sun, the other only three solar masses. Both are gorging on their nuclear fuels prodigiously. And both are yanking on each other like toddlers in a hair-pulling fight.
The two components are an average of 100 Astronomical Units apart (1AU = the Earth-Sun distance). Both are swaddled in disks of gas and/or dust falling in on them, or at least one of them, plus being stars so young—order of a few 100,000’s of years—their primordial nebula is still around them and in-falling on them both. Most of the time the star hovers between 10th and 11th magnitude but it has flared as high as 8.4, a good small telescope or binocular-visible star, in bursts of 4, or multiples of 4, years apart.
Recently, astronomers using Chile’s Atacama Millimeter Telescope and the New Mexico Very Large Array radio telescopes have noted some other variations of an irregular nature that can only be explained by some object flying by in or through those enveloping clouds. The gravitational pull of the intruder warps and stretches the materials, either causing a brightening of one of the stars with additional infall on its surface, or causing the in-falling material to brighten or, conversely, darken by eclipsing the star’s disk briefly. These have long been predicted by passing stars in computer simulations, but never seen before in reality. Given Z CMa is still immersed in its cocoon, it is likely there are still many primordial clumps of dust still around of some size that didn’t get absorbed into the star, nor formed into planets in stable orbits yet, but big enough to send large tsunami waves of planetary system dust scurrying around these two massive stars.
2. The Demon Star May Have a Family
Down below, in the Sky Planning Calendar, there is a discussion of observing the variable star Algol. The name is a corruption of the Arabic name for The Ghoul, meaning this star’s variability has been known for hundreds, perhaps thousands, of years. The cause of it, however, has been known for only a few hundred years; there is a companion star too close and too faint to be otherwise separately seen except as it partially eclipses (and gets later eclipsed by) the primary star.
There is a known third star that slightly changes the orbital timing of the two main stars, and thus the timings of the primary and secondary eclipses. Could there be more stars? Finnish astronomer Lauri Jetsu writes in the Astrophysical Journal that there could be two to four more. His study uses statistical methods to squeeze out periodicities over many years of observations, finding tiny changes over long baselines that could be caused by other companions’ gravitational pulls adding or subtracting theirs to the third star’s, changing the eclipse timings even more subtly over the years. From that, he proposes the additional stars. In fact, he claims that the eclipses are about a half hour off from what they might have been seen by ancient Egyptians. It might be also that the small bright central star is being eaten up by the dim larger star that eclipses it, which changes the orbital balance point, much like the change of weight on a see-saw changes the fulcrum position between two children. The bright kid is throwing food packets to the dim one.
There might be just a change in diet between the two main Demon Stars, or a host of little demons traveling through space. Jetsu hopes some interferometry, which can see much finer detail than regular telescopes, might resolve the issue in the future.
* The Fog Lifts From Our Solar Neighborhood
Two studies, near and far, revealed a lot about our solar neighborhood, and announced in a virtual press conference from the otherwise cancelled virtual American Astronomical Society #239 Meeting. Catherine Zucker of the space Telescope Science Institute and Harvard/Smithsonian Institute for Astrophysics took the “far” view, showing we are located inside a Local Bubble that is rimmed along its equator with star formation areas, while Seth Redfield of Wesleyan University examined the dusty nearby trail of the Earth’s motion over the past mere one million years.
On the first piece, the Sun finds itself in the middle of the somewhat cylindrical bubble a thousand light years wide caused by a supernova 14 million years ago. The Sun moved into the Local Bubble; our star wasn’t there when the supernova blew up. [See the Cover Photo—the top image is the view from outside the Bubble with the Sun in its center, the bottom image is the view from Earth.] Most of the new stars are forming in groups in our summer sky—Ophiuchus, Scorpius, Corona Australis and elsewhere—and just one large clump in the winter sky, Taurus. Whether the cloud of debris swept up by the supernova rammed into us or we rammed into us, or a combination of the two, isn’t clear but about 5 million years ago, supernova iron deposits from the debris cloud were made on Earth when we two collided. Though there are other stars in the Local Bubble, it is now clear that all the young stars nearby, within a 1000 light years, are all caused by the collision of the supernova debris cloud with the local interstellar dust.
This also implies that there must be numerous bubbles filling the Milky Way, and we just happen to catch ourselves inside this one.
Meanwhile, within the past 1 million years of that 5 million is Redfield’s study. He has used the Sun’s protective heliosphere, that boundary between the Sun’s magnetic field controlled area of influence and the interstellar fields, the solar wind border to the interstellar medium. Apparently, the heliosphere’s interactions with the clouds as we pass through them leaves tell-tale evidence in the temperature and motions of the clouds behind us. By looking in the ultraviolet spectra of the stars immediately behind us — in our rear view mirror, he says — we can see and measure which local clouds we’ve pass through, catch their temperatures and motions and compositions.
We entered a Local Interstellar Cloud about 60,000 years ago, and have been skimming its edge ever since. We are about to leave it and enter (or skim) a cloud called simply “G”. Much earlier we’ve been through or skimmed clouds labeled the Auriga and Blue clouds. Apparently our path is much like the US Southwest…dusty and patchy, blowin’ in the (interstellar and solar) winds.
* Halos Are Not a Single Ring, but Many Fragments
Our Milky Way looks so neat and placid, but in fact it is a voracious cannibal. There are at least two things we can learn from this story. One is, in fact, how the Milky Way came to be. And it did so with a varied diet. It eats galaxies and globular clusters whenever it can. In fact, that’s how it grows. In a whimsically titled talk “Twelve for Dinner,” Dr. Ting Li of the University of Toronto discussed how she and her collaboration, called S5, studies the leftover debris trails of the swallowed star groups.
There are 60-70 star streams known, but only 12 have been well studied. As a small satellite galaxy, or a dwarf galaxy—the most common ones in the universe—gets caught in our Milky Way’s gravitational well, it gets stretched out when it collides with us. These collisions, unlike those of cars, are not crash, bang, boom destructive; the small galaxy truly just gets bent out of shape, energy gets transferred to us, and the stars ultimately, within a few orbits get absorbed into the Milky Way. MMM, mmm, delicious. Looking for lines of stars with similar motions and compositions in the massive databanks like Gaia finds these streams. [I point Readers to a podcast on the original Galactic Times podcast website, click onto Episode 4, where Dr. Li and colleagues talk about their work on tracing out the Phoenix Stream, one of our most popular podcasts that year.] By working things backwards one finds out about whether the lunch was a galactic galaxy or just an unlucky snack of a globular cluster.
In fact, as an aside to this story, astronomers from the Canada, Europe and Russia, centered at the Gemini observatory, found a stream now labeled C-19, that is so metal-deficient that it had to have formed before any stars had supernovaed and formed elements beyond the hydrogen and helium they had started with. The stream, stretching from 20,000 light-years from the Galactic Center to 90,000 l.y., has but 5% the metallicity of the Sun, far below even the usual low-metal content of the earliest in existence globular clusters today.
A second thing Dr. Li’s group wants to use these streams for is to find the invisible. Dark matter. The streams trace out the vine-like clumps that dark matter is believed to form around our galaxy. As she puts it, it is like using strings of Christmas lights to figure out where the dark branches of the tree are. The more they can figure out where the streams are and to which ancient relic of a galaxy or cluster the various streams belonged to, the more they can find those ‘tree branches.’
Sky Planning Calendar
Moon passages by a star, planet or deep sky object are a good way to find a planet or other object if you’ve never located it before.
January 17 Full Moon. Find it near the eastern twin star Pollux this morning.
January 20 Find the waning moon near Regulus, in the dawn.
January 25 Last Quarter
January 29 The Moon is very low in the bright morning twilight sky, and slightly higher than it, and to the Moon’s left by two degrees (four moon diameters), you’ll find Mars.
January 30 Moon is at perigee, its nearest point in its orbit to us, for the second time this moonth, er, month. Being such a thin crescent moon, we can call this a Super Skinny Super Almost-New-Moon! Take a glimpse to the Moon’s left, about 6-8 diameters, and very slightly higher but still close to the horizon (you’ll need a very clear ESE to SE horizon view) and you’ll Mercury starting a morning apparition.
Let’s review the solar system from innermost to outer planets first.
Mercury can still be glimpsed in the evening if you have clear and low horizons near the sunset point, but only until the 20th, when it sets earlier than 40 minutes after the sunset, and the skies then are always just too bright. On the other hand, from the 27th onward, you can watch Mercury rise in the dawn 40 minutes or more before sunrise. There are technically some days overlap that telescopists could find the little world both in the evening and morning skies because its solar conjunction happens with Mercury passing far away from the Sun’s bright disk, but unless you’ve got a superbly set guided scope, it is far too risky to try this. You don’t want an accidentally glimpse of magnified sunlight to fry your retina, so … please don’t….
Venus has left the evening stage after the first few days of January but then rocketed into the morning stage! It rises before twilight starts by January 22nd and is dark skies for about 40 minutes by month’s end. Interestingly, viewed against the stars, Venus has been retrograding, moving westward, but that stops on the 29th. That doesn’t mean the morning show is over or that Venus has maxed out its distance (elongation from the Sun)! Au contraire! It just means that it will continue to ‘elongate’ because the Sun will move eastward among the stars faster than Venus does, because Venus will be heading more away from Earth than passed the Earth.
An interesting observational exercise, one you might try with people of different latitudes can be done during the time of January 24-31. During one of those days, Venus will be at the same altitude from the horizon as Mars (both level to the horizon together). But that will vary with latitude, and as Venus moves away from the Sun, the day with vary, too! If students were to watch every morning before coming to school, and from different parts of the Earth, a latitude effect could be noted!
Mars rises about 30 minutes before morning twilight begins….and it stays that way, even diminishing slightly during the spring, until it finally gets over its lazy streak and starts to edge away from the Sun in May. It is no brighter than the stars of the Big Dipper.
Jupiter has the evening essentially to itself, for a while shining brightly in the southwest, setting roughly 7:30 to 8:00 local time. Use the time you have; Jupiter leaves the sky in a month.
Saturn is an evening twilight denizen, setting before twilight ends and no earlier than 45 minutes after sunset during our issue dates, well, up until the 26th. After that, the twilight is just too bright and Saturn too low to catch it. It will be a dawn denizen starting very late February-early March.
Uranus. Not something we normally worry about, though technically a naked eye world at magnitude +5.7 (+6.0 is the traditional limit though most of us don’t have neither the eyes nor the dark skies to see that!). But here’s a good binocular opportunity. On the 18th, and effectively for much of the rest of the month or more, Uranus will be 0.4-degrees, slightly less than a moon diameter south (below) the even fainter (+6.0) star 29 Arietis. So you use the chart below, find the two nearly identical stars, and over time, watch one of them move! <gasp> and you’ve got the first discovered planet off your bucket list.
One star thing. Perhaps the best eclipsing binary for beginners, with the deepest and most predictable eclipses, Algol, has two eclipses in ‘prime time,’ i.e. evenings. I won’t say what hours because what is best here is to go out and make regular (every 15 or 30 minute comparisons between the three standard stars on the map below and see which Algol matches and which/how much it is in-between. The minima occur on the nights of the 19th and 25th. a good graph exercise, even if it is a brute force graph—-Y axis is (highest starting point) brighter than star 2.1, equals 2.1, between 2.1 and 2.9, equals 2.9, between 2.9 and 3.4, equals 3.4, fainter than 3.4). Time is along the bottom X axis.
Border Crossings - You are Forecasted to be Lucky if Your Birthday is the 19th!
So close to a match…not. Traditional horoscope….Sun in Capricornus on 19th, enters Aquarius the 20th. Reality? In Sagittarius on the 18th and enters Capricornus on the 19th. A sorta one day overlap?
Astronomy in Everyday Life
* Merry Not Obliquity <sigh>
This came to an alumna of this university, which as astronomy department no less. Clearly the PR department didn’t clear the Season’s Greetings with them, the number of science mistakes in this staggers the mind. How many can YOU find?
The Classroom Astronomer Newsletter Issue 16 Highlights
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Welcome to Issue 16, the First Issue of 2022!
Cover Story - Locating the James Webb Telescope at L2
Sky Lessons - “Spring Semester”
Astronomical Teachniques -
Mind Your Beeswax!
Color Image and Video Collections
The RAP Sheet – Research Abstracts for Practitioners -
- Investigative study on preprint journal club as an effective method of teaching latest knowledge in astronomy
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