The Galactic Times Newsletter #9 - September 16 - 30, 2021

Hurricane Larry and Sunspots--Are They Correlated?

(Photos--RAMMB/CIRA/CSU, SOHO/NASA)

In This Issue: 

  • This Just In — Predicting a Supernova in Advance; 3D Printing of Interstellar Clouds

  • Sky Planning Calendar — Moon-Gazing, Observing—Plan-et with phases and seasons and Kepler’s Second Law, Border Crossings

  • Astronomy in Everyday Life — Hurricanes, Sunspots and Climate Change, Oh My!

  • The Classroom Astronomer Newsletter Highlights


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Last half of August, first half of September has been a slow news period, and a stormy one, with Hurricane Ida passing nearby (and a twister even nearer), and Tropical Storm Nicholas on top of us right now. School and other events are beginning so things should pick up again as the weather cools down. Hope you all are safe.

Yours truly will be on a non-astronomical book presentation trip during the period of September 22-27th around Mobile, AL. The TGT Issue for October 1st may be delayed a few days. Fortunately, for observational happenings, such as Moon-Gazing, nothing is going on….New Moon on the 6th, Mercury and Mars in solar conjunction on the 8th! Nothing to see here folks! We’ll add in any news to the shortened column space <grin>.

Dr. Larry Krumenaker.


This Just In—

Predicting a Supernova 16 Years From Now

Scientists at the Hubble Telescope, a.k.a. Space Telescope Science Institute, are known for making hyperbolic statements (probably justifiably) about their photos, but not usually for predictions. But they’ve made one now, for a future supernova. Unlike, say, periodic comets or eclipses, supernovae are not known for clockwork precision, but there is one that these scientists want to stake a claim to for a date. This exploding star, dubbed Supernova Requiem, is predicted for 2037 (hedging plus or minus a couple of years…), though only Hubble and maybe some other telescopes will view it.

How can they be so sure? Because they’ve seen it before.

Lead researcher Steve Rodney of the University of South Carolina in Columbia notes that this will be “the fourth-known view of the same supernova, magnified, brightened, and split into separate images by a massive foreground cluster of galaxies acting like a cosmic zoom lens. Three images of the supernova were first found from archival data taken in 2016 by NASA's Hubble Space Telescope.” Multiple images are produced when a foreground galaxy cluster's gravity distorts and magnifies light from any supernova far behind it, a process called gravitational lensing. The third image captured by Hubble, from the cluster, MACS J0138.0-2155, took about 4 billion years to reach Earth. The light from Supernova Requiem needed an estimated 10 billion years for its journey, based on the distance of its host galaxy.

The team's prediction of the supernova's return appearance is based on computer models of the cluster, which describe the various paths the supernova light is taking through the maze of clumpy dark matter in the galactic grouping. Dark matter is an invisible material that comprises the bulk of the universe's matter and is the scaffolding upon which galaxies and galaxy clusters are built.

"Whenever some light passes near a very massive object, like a galaxy or galaxy cluster, the warping of space-time that Einstein's theory of general relativity tells us is present for any mass, delays the travel of light around that mass," Rodney said. He compares the supernova's various light paths to several trains that leave a station at the same time, all traveling at the same speed and bound for the same location. Each train, however, takes a different route, and the distance for each route is not the same. Because the trains travel over different track lengths across different terrain, they do not arrive at their destination at the same time.

In addition, the lensed supernova image predicted to appear in 2037 lags behind the other images of the same supernova because its light travels directly through the middle of the cluster, where the densest amount of dark matter resides. The immense mass of the cluster bends the light, producing the longer time delay. "This is the last one to arrive because it's like the train that has to go deep down into a valley and climb back out again. That's the slowest kind of trip for light," Rodney explained.

* 3D Printing of Molecular Interstellar Clouds

(Orion B Molecular Cloud, photo from ESA)

Among the least understood, and hardest to visualize, structures in the universe are the molecular clouds that float between the stars, and that ultimately form into the nebulae and stars in the galaxy. They are cold, dark, and amorphous, and are detected mostly through radio telescopes, and visualized mostly through arduous plotting in two-dimensions. Researchers at the University of California-Santa Cruz, the Center for Astrophysics in New York City, and Harvard University managed to take data and convert it into 3-dimensional lattices and turn that into visual representations with a 3D plastic printer.

What they find are strong representations of the dynamics in three dimensions of shock features, self-gravitational activities, and magnetic field structures. It also shows how the clouds have sheet structures that are complex and which do not show up well in 2D representations. Lastly, they show that filaments actually bend and whirl and loop over much longer distances than presumed before and yet remain coherent throughout the cloud.

(Imari, Forbes and Weaver, The Astrophysical Journal Letters, 918:L3 (9pp), 2021 September 1 https://doi.org/10.3847/2041-8213/ac194e)

Sky Planning Calendar

Moon-Gazing

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.

September 16 Tonight through tomorrow, the Moon passes 4 degrees south of Saturn.

September 17 Ditto the above, through the 18th, only for Jupiter!

September 20 The Full Moon, notably known as the Harvest Moon, though sometimes this may be wrongly attributed to later Full Moons rather than the one nearest to the Fall Equinox in the Northern Hemisphere. Closer to the North Pole it might well be that it is the last good Full Moon to light up the skies and harvest crops, though October is still often a good bet to beat the frosts.

September 26 The Moon is at apogee, its farthest point in its orbit from Earth. You’ll find it between the two easy star clusters in Taurus, the V-shaped Hyades that make up the outline of the Bull’s Face and the tiny dipper-shaped Pleiades. At apogee, the Moon appears its smallest apparent size, though the difference between largest and smallest is barely noticeable to the human eye. Still, the size change is photograph-able, as long as you use the same lenses and equipment and magnify the same amount at apogee and perigee. The next perigee [when we have SuperMoons (gack!)] will be October 8, if you want to prepare.

September 28 Last Quarter Moon.

Don’t let this phase you….

Notice it took 8 days (actually a fraction over exactly 8) to get here from the Full Moon? But the First Quarter (see TGT #8) was on September 13th, so it took 7 days to get to the Full Moon. The ‘quarters’, though geometrically one-fourth of the way around the sky, are not exactly one-quarter of the orbital time, are they? Because the Last Quarter is very nearly at apogee, and First Quarter was at perigee, the closest point to Earth in the Moon’s orbit, it is clear that, right now anyway, the Moon moved through that ‘first quarter to Full’ quarter orbit faster than the ‘Full to last quarter’ quarter-orbit.

This is evidence that Kepler’s Second Law is in force. Kepler’s Second Law says--in a general way--that objects in orbit move faster when they closer to what they orbit than when they are farther. The usual analogy is that a skater’s fists move faster when s/he draws in his/her arms; they are still attached, of course, so something has to compensate for the closeness--angular momentum must be conserved. So it is with orbiting bodies. They move in their orbits faster when closer in, slower when farther out.

But the Moon’s perigee and apogee moments do not stay with the same phases all the time. They slide through the phases, not only through the year, but over the years as well because the Moon’s elliptical orbit itself revolves. Sometimes the perigee points towards the Sun, sometimes away, sometimes to one of the sides. January’s perigee was the 9th, June’s the 23rd, this month it is back to the 11th, almost back to the start of the perigee cycle. But as it does so, the Earth carries that orbit around with it over the year and the New/Full/Quarter phases all adjust and slide through the calendar. January’s Full Moon was the 28th. September’s is the 20th. The Moon’s orbital motion, two days shy of its phase period, almost but not quite keeps time with that revolving perigee. So the time period between phases is not exactly one-fourth of a month all the time. Sometimes it is a bit longer…during the apogee part of the cycle.

If you have a calendar on the wall with the phases marked on the dates of each month, look for when the time periods are 8 days, and you’ll get a good idea when apogee is, and when you WON’T have Super Moons…..

Border Crossings

The Sun crossed the border of Leo and Virgo on the 15th-16th. The traditional signs had the Sun in Virgo already. The Sun will remain in Virgo for a whopping 45 days, the largest it hangs out in a zodiac constellation! The horoscopes fail to acknowledge that longevity; they claim the Sun exits the Virgin into Libra the Scales a mere week later, on the 23rd. So only for a week do astronomy and astrology align…..tsk, tsk…..

Observing---Plan-et….                                    

This is a short planetary month, so to speak. It is nothing but stars in the morning sky and mostly three planets in the evening….

As the Sun sets and what few crickets are left chirping, Mercury barely hangs out for Northern Hemisphereans, essentially disappearing from view (setting 45 minutes or less from Sunset) by the 22nd. Southern Hemisphereans have a better view…but only for perhaps a few days longer. Try using binoculars. Your signpost is approximately as bright blue-white Spica, hanging out around 1.5-2.0 degrees from Mercury all the rest of the month.

Next up is brilliant but still rather low Venus. It is threading the chains that hold the scales of justice in Libra, passing its Alpha star. Although nearly as far as it can get from the Sun, it is south of the Equator--the Celestial Equator--which makes it hug the horizon rather than hang high above the ground. But it is slowly easing its way higher, remaining in the dark, post-evening twilight sky for now 20 minutes before setting. That will increase to about an hour by early December, when it does a rapid hail-and-farewell swan dive to a solar conjunction but with the bonus of a large, beautiful crescent to observe!

Earth --always visible below your feet--reaches its September Equinox at 2:21pm Alabama, er, US Central Daylight Time on the 22nd. It always surprises people that, still, we actually do not have 12 hours of daylight and 12 of night on that day, especially at this latitude. That actually happens a few days later, roughly the 25-26th (they are both off by a minute). It’s that old Kepler Second Law thing in effect where, yeah, it may be the tilt of the Earth that causes the Sun’s position to reach the POINTS of solstices and equinoxes, but the SPEEDS of solar motions in the skies that are a function of both rotation of the Earth AND its REVOLUTION around the Sun and it takes a little time for the two to coordinate to get day-night equality.

(Don’t let this phase you either…)

Count the days between the equinoxes and solstices (you may need a calendar for last year or next year for this). You’ll see that not all seasons are equal. If you learned the lesson of the Moon calendar above, you’ll know that we’re closer to the Sun at perihelion (the solar orbital equivalent to perigee) and we’d be moving faster. Perihelion is NOT exactly timed to a solstice or equinox anymore than a lunar phase is tied to a perigee, but you’ll definitely see that one season has decidedly more days than the others, and one has definitely fewer days. Since the points in the sky when the solstices and equinoxes ARE exactly 90 degrees apart, it means during one of these periods the Earth has to be moving faster, because we are closer, and in the other we’re slower and farther. Surely you can figure out where we are in our orbit in this time period, right?

Mars is still on vacation.

Jupiter is already up by the time it gets dark and is up most of the night. At month’s end, it sets around 3:15 AM. It is still retrograding, moving westward instead of eastward, the illusion that is caused by the Earth passing the planet in our orbit around the Sun.

Saturn, higher and to the right of Jupiter, still displays well its rings and moons, in the south-southeast sky, still retrograding. But it sets earlier; at month’s end it is gone by ~1:45 AM.


Are you almost late? Check…with the Hermograph Wearable Sundial T-Shirt! Works as a clock or a compass.


Astronomy in Everyday Life

Are the Additional Hurricanes Related to Sunspots and Climate Change?

It is a perennial question that comes up in classes. Are we getting more and more hurricanes? Is this due to “climate change”? Or is it just a normal blip? Maybe it is related to something else, like sunspots? Don’t they change the Sun’s radiation to the Earth?

<sigh>

So let’s take a look at the recent past and do a little quick statistical analysis. Googling up the past five years of information (and adding what is possible for an incomplete 2021), here are the total number of tropical systems worldwide, the annualized sunspot numbers, and the annual global temperature change compared to the 20th century average:

To make things easier in graphing I multiplied the temperatures (which are in Fahrenheit, not Celsius, by the way) by ten; they aren’t really that high! So the changes are actually 1.78 degrees above average, 1.64 degrees, etc.

Many of TGT’s readers will be also surprised at the number of tropical systems, because most readers are America-based. We are rather used to peering into the Atlantic, where the number of systems have been phenomenally high in 2020 and 2021 so far (14 named systems, a few only-numbered tropical depressions, and at least three more as I write this as possible systems bubbling away in the Atlantic Ocean, one heading again in my direction). Yet 2020 is actually the lowest number in the past five years worldwide, covering the northern and central Pacific, Indian, southern Pacific and both Atlantic basins, too. And, for sunspots, we’re not only at a minimum, but it is just last year and this year barely on the rise in the new sunspot cycle.

Here is a graph of the above data:

If anything, there is an anti-correlation with tropical systems and sunspots! But the temperature anomaly shows no correlation with anything. You have a correlation if both lines increase together, or decrease together, or an anti-correlation if they go in opposite directions.

But let’s remember several limitations here. First, correlation does not mean causation. My most favorite teaching example is a graph of city crime rates and number of churches. They are almost always directly correlated; you have high numbers of churches in cities with high crime rates. If you believe in causation, then either crime causes churches to come into existence, or churches cause crime! But all too often it is really a third factor that causes both--in this case, different numbers of populations. There is no evidence on that in such a graph. So there is no clear way to say that there is a mechanism that causes the number of sunspots to diminish the number of worldwide tropical systems. Since tropical systems require heat, and the global temperature changes don’t correlate, how can that be?

The second limitation is that we are only looking at five years of data. Like money, with data and statistics, more is always better, and sunspots are a periodic function in time. They rise and fall over an 11-year average. This graph doesn’t show that. How does that play into this is not evident in just five years, and at a minimum no less. Nor do we have enough years to see how the temperatures changed compared to tropical systems counted. It is just too small a sample. You may get a ballpark figure if you measure something and take an average with three measures, but you get a much better average, and a better idea of accuracy of that average, with a dozen measures. Five years is not enough.


The Classroom Astronomer Newsletter Issue 9 Highlights

This premium newsletter is a subscribers-only publication, though a free Lite version is available.

  • Connections to the Sky - Dr. Andrew Fraknoi’s List of Free Astro Labs

  • Astronomical Teachniques - 
    Using the Calendar to Demonstrate Two Examples of Kepler’s Second Law;
    What Color is the Sun? Or Any Other Star?

  • The RAP Sheet – Research Abstracts for Practitioners - 
    Estimating Star Distances with a Light Bulb;
    COVID-19 Precautions for Public Astronomy Education Sessions


Coming Soon!

Learning Astronomy Under The Northern Stars – A 365-Night Per Year Textbook

Use the stars that are ALWAYS visible to understand basic astronomy, stellar evolution, galactic structure, with the naked eye and common binoculars.  EBook and print book coming.  Detail description and advance orders link coming soon (sorry for the delay!).


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Thanks for reading. Until the next newsletter, stay safe.

Dr. Larry Krumenaker

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