#36: What IS Above Us? - Moon's Coming for Mars! - (& 3 more)
TGT 12/1/22: TGT InDepth Preview #2--What IS Above Us?; Sky Planning--Evening Sky Has All the 'Marbles', Mars Opposition and Occultation!, Geminids a Bit of Washout; AEL--Black Hole Cartoons
Cover Photo - What is Above Us?
In This Issue:
Cover Photo — What Is Above Us?
Welcome to Issue 36! - We’re #6! We’re #6!
Sky Planning Calendar —
* Moon-Gazing - The Evening Sky is Now Complete With Planets, from East to West Horizons
* Observing—Plan-et - Look Out Mars, The Moon’s Coming for You!
* Border Crossings - Ophiuchus Still ReignsAstronomy in Everyday Life — The Black Hole Donut
The Galactic Times — InDepth Inbox Magazine #2 Preview! - What is Above Us? (Cover Story)
The Classroom Astronomer Issues 39 & 40 Highlights
Welcome to The Galactic Times Newsletter-Inbox Magazine #36 !
Just want to toot our own horns….but after a year and a half of publication, on Substack, The Galactic Times ranks as the #6 astronomy newsletter! The Classroom Astronomer is #2!!
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Our newest publication, The Galactic Times — InDepth explores a topic in each issue, as stated, in depth, like a New York Times Sunday Magazine piece, rather than running a story over two or more regular Galactic Times issues. A preview of the opening of December’s issue, on the Gaia mission with the point on answering the question, “what’s really above us?” is in this issue of TGT.
InDepth is a premium publication. It will start as a monthly magazine with an occasional bonus issue as topics warrant. The introductory subscription through Substack will be $18.00 per year. For more information, go to https://www.thegalactictimes.com/indepth and subscribe at https:/tgtindepth.substack.com .
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Publisher — Dr. Larry Krumenaker Email: newsletter@thegalactictimes.com
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.
View or Download this information on our Sky Event Online Calendar on The Galactic Times homepage!
December 1 Neptune is 3-degrees North of the Moon. More easily viewed 12 hours later is Jupiter, also 3-degrees North of the Moon…
December 4 That very same Neptune hasn’t moved much in three days….because it just stopped its retrograde motion today.
December 5 Uranus gets occulted (covered up) by the waxing, growing Moon, but only if you are in Europe, north Africa, the Middle East, Russia or north Japan. The rest of us can find it about 0.7-degrees south of the Moon, if you are interested and have a telescope.
December 7 A BIG NIGHT! It is the Full Moon (it is in opposition to the Sun—180-degrees opposite it in the sky), Mars is in opposition, too, AND for many the Moon will occult Mars! See below!
December 11 The middling bright star Pollux in Gemini is 1.8-degrees North of the Moon, and the Moon is at its farthest distance from Earth this month, its apogee. A Micro-Waning Gibbous Moon! But not Waning enough for the next event….
December 13-14 The Geminids meteor shower peaks, on the midnight between these dates. You can find these bright and fast ‘shooting stars’ all night, the rare major meteor shower that gives a show all night long. Over the past few decades it has intensified from being #2 to the summer Perseids to sometimes way surpassing them by a factor of two! Not likely this year, with that waning Gibbous Moon two Ecliptic constellations to the East, in Leo. But you might see a few fireballs early in the evening before moonrise and some on the next night, though the shower rate will have diminished considerably a day after its peak.
December 16 Last Quarter Moon.
Observing---Plan-et
Mercury and Venus are both achingly, slowly emerging into the December evening twilights. On the 16th the two are just under 6-degrees apart, about a standard binocular’s field of view, but setting no better than 40-ish minutes after sunset, and likely hard to find at 30 minutes when the sky is still very bright and they are very low. Venus does set later than 40 minutes after sunset after the 8th, almost an hour after sunset after the 16th, and Mercury is higher and sets later than Venus even though it is not so bright as its sister. An interesting challenge pair.
This is Mars’ grand entry into the evening sky! First, it is closest to us, the day before this Issue date, November 30th, but at opposition, visible ALL NIGHT, on the 7th. On that date it both reaches peak brightest (magnitude -1.9, brighter than everything visible except the Moon and Jupiter), and the biggest it will get in a telescope (17.1” of arc) and yet for some, for a little while, it will be not visible at all! The Moon will cover it up!
You have to be within the ‘tube’ in the above illustration to see Mars get completely covered. In most of the USA, all of Canada, that’s the evening of the 7th. It is the predawn of the 8th for most of Europe. Given that Mars is a disk and not a point of star-light, anyone along the lower, southern line of the tube will have a slightly different experience—a grazing occultation. To the naked eye Mars will dim but not (necessarily) disappear from view. In a telescope, the Full Moon’s edge will slide over the disk. But the zone of partial occultation is only 20 miles wide! You have to be in that path; to the North, Mars is covered for minutes to an hour, to the south, no coverage at all. That line roughly goes as followed:
From NE Mexico across southern TX near Del Rio, just south of Austin and south of the ArkLaTex region, to northwest of Nashville, TN, very near the heart of Lexington, KY, along the Ohio River region in WV, across central and NE PA, north of the New York suburbs north of NJ, across the triple point junction of NY-CT-MA, on a bead to the triple point junction of MA-ME-NH, then over the waters to Nova Scotia.
The occultation begins ~6:30 PM Pacific time (time varies depending on your geographic location), and begins around 11 PM EST in Maine. If you aren’t interested in scientific observations of it, then get out early enough to watch the approach of the Moon. Then, if you seeing the Moon cover it, see Mars wink slowly out (instead of instantaneously like a point-like star), and emerge some time later the same way. Timing the wink might be an interesting exercise for a class to make.
Jupiter has a neat lunar conjunction on the 1st but otherwise it is the brilliant king of the sky (well, if you ignore the Moon) and a prime telescope object.
Saturn is beginning to become a bit worse for the wear. It sets before 9 PM local time by mid-month and is fading a bit. Get into now because by the end of January, it will be out of the evening sky.
Border Crossings
Remember Ophiuchus? The Sun is still in that constellation for the entire 16 days of this Sky Events Calendar. It enters Sagittarius, two days afterwards….which will match the astrologers (yay, hooray!) for a whole 4 days….(boo hoo….)
Astronomy in Everyday Life
Couldn’t pass this up — artwork from IAU Shaw astronomy education conference participant Chi-Kwan Chun, discussing the Event Horizon black hole photo and how it has gotten into popular culture!
The Galactic Times InDepth Newsletter-Inbox Magazine Preview
What IS Above Us?
The simplest answer to “What is above us?” is, the sky, and next, the stars. But from the earliest years, and the earliest of times, we learn that the sky changes with the hours of the night, and the months of the year. Except for one star, at least for those of us who live in the Northern Hemisphere of planet Earth.
The colloquial wisdom, and the astronomy we often teach, especially at lower grade levels, is that Polaris is the North Star because “it doesn’t move.” It is constant. That’s actually wrong on at least two levels. First, Polaris hasn’t always been the Pole Star; in fact, it wasn’t within even 4-degrees of the North Celestial Pole until around 1000 AD, a millennium ago. Even now, it is not there...and never will be on top of the North Celestial Pole, the NCP. It will get only as close as about 0.4 degrees, just under a Full Moon’s diameter away. This motion is due to Earth’s polar precession, the 25,800 year wobble of our planet’s axis, the pole making a cone over that time, and pointing out a circle among the stars. It pointed to dimmer Thuban in Draco the Dragon in the eras of ancient civilizations in the millenias of BC. Second, Polaris does move, every night, in a circle around the actual Pole, the NCP, a circle about 1.4-degrees in diameter because of Earth’s rotation. Constant in position it is not, except among its fellow fixed stars of Ursa Minor, over the lifetimes of humans anyway.
Let us at least honor and get to know the star for its historic role. Polaris has quite a personality for a constant star. For instance, its brightness hasn’t been constant either. There is historical evidence that Polaris has been brightening over the past 2000 years. Currently it is visual magnitude +2.0, making it around the 50th brightest star, give or take a few places. It certainly isn’t the brightest star in the sky, although that is a common misconception! But in the times of Ptolemy (around 200 BC) and al-Sufi almost a 1000 years later, it was listed as faint as (in modern units) magnitude 3.5. Next, even on shorter time scales, Polaris varies, because it is a kind of pulsating variable star called a Cepheid. So it gets a little brighter and little dimmer on a regular periodic basis, about every 4 days, that period growing longer 4 seconds per year. The magnitude range currently is only 0.02 yet in the past the range may have been as high as 0.1. A constant star? Hardly. Still, it does hold the place of honor as the brightest and nearest of all Cepheid variables
How near? Estimates average about 433 light years (ly) away, with roughly a 10% uncertainty factor, with the Gaia mission placing it about 12 light years farther, but others as much as 100 light years closer. At 433 ly, the light we see tonight left Polaris ~1589, just 46 years after Nicolas Copernicus, creator of the modern heliocentric theory, died and around two decades before the English began to colonize North America and before both Galileo and Kepler did their telescopic and planetary motion work.
The stellar basics—Polaris is about 2000 times more luminous than our Sun. If brought to 10 parsecs away from us, the distance in which we measure all stars’ absolute magnitudes or absolute brightnesses, it would be magnitude –3.6, almost as bright as Venus. It is a spectral type F8 Ib+II, meaning it is a little bit hotter and slightly more towards the white end of yellow stars than our Sun, and a giant star. The mass is about 4-5 solar masses, gravity 100 times stronger, and about 46 times Sun’s radius. Polaris is making its first trip off the Main Sequence, where all stars shine during the longest stage of their lives, expanding and cooling as it ages towards a red-giant phase. Polaris isn’t alone. It has at least one orbiting companion revolving around it every 30 years, and one other star as well, characteristics poorly known. As also an optical double, Polaris’ visual companion, Polaris B, doesn’t share the motion of our bright Pole Star, Polaris A, though it makes the pair a nice telescopic appearance. Speaking of traveling, there has been suggested it belongs to a Pleiades moving star group but that notion appears to have been squashed.
Astronomically, Polaris was named Alpha Ursae Minoris by Bayer, 1 Ursae Minoris in Flamsteed numbering, and a host of other alpha-numerically prosaic designations in multiple star catalogs. In almost every culture and language, this star’s name usually means “important” or “major star” or something similar. Among the Inuits the name is Nuuttuittuq and it means “never moves.” No matter what language you speak, Polaris is one of the stars one needs to learn.
Polaris is convenient, but NOT at the real North Celestial Pole today. What IS at the real North Celestial Pole? Today? In other words, what is above…us? What is at declination +90 degrees, and no minutes or seconds of arc (because there aren’t any such things when you get to +90)? To learn that answer, we have to dive deep into the Gaia database.
. <What is Gaia, and how do we search it, and what do we find?>
But what may be at the North Celestial Pole really isn’t above us. It is just arbitrarily above our spinning Earth which happens to be tilted a certain amount due to, well, nobody is exactly sure why. What should really be the answer to our opening question should what is above the Solar System. All the main bodies of the System, the planets from Mercury through Neptune, all orbit within a relatively small distance from a plane, a likely remnant of the original rotational ‘equator’ of the primordial nebula from which we came. If you define the Earth’s orbit as 0-degrees inclination, all the others but two follow suit closely, within less than 2.5-degrees difference (that one is Saturn). Venus is larger (3.3) and Mercury largest (7.0). You’d have to do a little math to decide if the differences cancel out, like if Mercury rises above the plane towards one direction of the sky but Venus is at its lowest point in the same direction or some other one, to see if the Earth itself is really ‘on the average” but for all practical purposes, it likely doesn’t matter.
It turns out that the north orbital poles of all the eight planets are located in the same general region of the sky, within the constellation of Draco, with only Mercury’s a bit away from the rest of the club. The centroid of the bodies, less Mercury, is centered in a blank area nearest Jupiter’s north ecliptic pole, from an orbit 1.3-degrees tilted from Earth’s. Given the giant planets are furthest and have the most mass, using them to determine the Solar System’s pole is probably most accurate, but ignoring the two inner planets and their tiny orbits and using the ‘North Celestial Pole’ for the whole Solar System is probably pretty close to what astronomers call the North Ecliptic Pole, for Earth, and that will be good enough for us.
Where is that and what is there?
<Finding the NEP with Gaia, both nearest to the pole, AND nearest/brightest objects to US>
But the Solar System is imbedded in the Milky Way Galaxy and is at an incredibly high tilt to the Galactic Disk. The Ecliptic is tipped about 60-degrees from the line we use as the Galactic Equator in the Galactic coordinate system. It was initially defined several ways, nailed down in 1932, and re-nailed to the plane of the galaxy’s neutral hydrogen clouds in 1958. The North Galactic Pole, that part of the Milky Way that is indeed above us, is located at RA 12:49, Dec. +27.4 in 1950 coordinates. In 2000 coordinates, the measures have precessed (that stubborn problem that affects Polaris et al) to 12:51.4, +27.13, a place in the spring constellation of Coma Berenices.
So the final question is….What IS above us, in the galaxy?
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If you want to know that final answer, subscribe to The Galactic Times Indepth Newsletter-Inbox Magazine! Click this box to go the Substack home of InDepth:
Issue 1—November 2022 Space Tourism on Earth - A Visit to a Crater (Article Available as a PDF for free in the online preview).
Issue 2—December 2022 What’s Above Us? An Examination of the Gaia Mission and Exploring the Question, What Stars are REALLY above the Earth and the Solar System?
The Classroom Astronomer Newsletter - Inbox Magazine #39… [Nov. 21, 2022, Free Post]…
Cover Photo - Zodiac Dates
Welcome to Issue 39!
From the IAU Shaw Meeting, and Education To the 13 Ecliptic ConstellationsSky Lessons -
- Ecliptic Constellations Sizes and BordersConnections to the Sky
- Need Some Astronomy PowerPoints?
- Galileoscopes for the Upcoming Eclipses
- Light Echo Video from NASA
- IAU Shaw: Looking for Astronomy Storybooks? Look Carefully…Astronomical Teachniques
- IAU Shaw: Ten Strategies for a Successful Primary Curriculum
… & The Classroom Astronomer # 40 [Nov. 29, 2022, Paid Post] Highlights!
Cover Photo - What Makes the HRD So HaRD?
Welcome to Issue 40!
Deeper Look -
IAU Shaw: Astronomy is Universal—The Gateway Topic
- Constellations are Electrifying
- Math on Earth or in Space (2 items)
- Math On Other Worlds Beyond (2 items)Connections to the Sky
- IAU Shaw: Gravitational Wave Resources
- IAU Shaw: Astro News For Kids
- IAU Shaw: A Full Dome Planetarium CurriculumThe RAP Sheet: Research Abstracts for Practitioners
- Extracting Information from the Hertzsprung-Russell Diagram: An Eye-Tracking Study. (Cover Story)
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