This is the Classical Astronomy Update, an email newsletter especially
for Christian homeschool families (though everyone is welcome!) Please feel free to share this with any interested friends.
Remember now thy Creator in the days of thy youth, while the evil
days come not, nor the years draw nigh, when thou shalt say,
I have no pleasure in them. -- Ecclesiastes 12:1
IN THIS UPDATE
Jupiter and Saturn Converge
Hello Friends,
2019 has been a mostly boring year in Classical Astronomy. Venus has been lingering in the morning sky for most of the year and Mars has been inconspicuous after its great apparition in 2018. Except for the lunar eclipse back in the winter, the sky has been uneventful this year and there's not been much to write about.
But the sky is getting more interesting in the latter part of the year. Venus passes superior conjunction on August 14, when it will align behind the Sun. After that Venus will reappear in the evening sky where it will be visible through the spring of 2020. The most notable sky happening is the advancing convergence of Jupiter and Saturn, which is the subject of this
newsletter.
In other news, after 14 years of self-employment I recently started a regular "day job." This leaves even less time than ever for Classical Astronomy. But I did order another print run of our Signs & Seasons curriculum, and thereby decided to stay in business for at least another year or two. At this point, there
are over 10,000 copies of S&S in print since 2007. The big-name homeschool science publishers sell that many of each title every year. But I'd like to think that what we lack in quantity, we make up for in quality!
I'm still holding out a ray of hope of creating a color edition of S&S and continuing with the series, even after all these years. I've lately been spending time again on the sequel to S&S, called Measuring the Heavens, which has stalled on and off since 2009. But now that the kids are mostly grown, I'm hoping to find the time for such projects, at least as a "bucket list" endeavor to memorialize a
lifetime of research. I believe that there is potential interest in this astronomy content outside of the homeschool community, especially in homesteading, prepper and nature interest circles.
A new lunar month is beginning and this is a great time to learn the cycle of the Moon's phases. Our Moonfinder storybook was especially created to help little kids (and their parents and grandparents!) to learn how to observe and follow this lunar cycle. And Moonfinder works! Everyone who has read it has come to understand and appreciate this ancient cycle, which is mysteriously forgotten in our modern world.
Order a copy of Moonfinder for that young person in your life. And if you order a copy now, we'll throw in a second copy for FREE. Order any product from our online store and we'll add a free copy of Moonfinder.
For more information about topics from Classical Astronomy discussed in this newsletter, please check out a homeschool astronomy curriculum (but popular with adult readers too!)
Visit our archive of previous editions of the Classical Astronomy Update newsletters, going back to 2007.
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Jupiter and Saturn Converge
Jupiter has been dominating the evening sky all summer. If you've never spotted Jupiter before, you might be surprised by the blazing, brilliant brightness of this object. The planets are among the brightest "stars" in the night sky, and Jupiter is the fourth brightest object visible from the Earth, after the Sun, Moon and Venus. Look for Jupiter above the south in the early evening sky after night falls.
Jupiter is currently passing through the constellation Scorpius, and is to the upper left of the bright star Antares in Scorpius.
Also sharing the evening sky with Jupiter in the current season is the planet Saturn, currently passing through the constellation Sagittarius, the next constellation to the east from Scorpius. Saturn is not as bright as Jupiter, but it's still comparable in brightness to the brightest stars in the sky.
Saturn is an amazing object in even small, amateur telescopes since its famous rings are easy to see. Jupiter itself is also very cool, with the four Galilean moons readily visible in even the smallest scopes. While it's still summer, everyone should visit a local astronomy club, planetarium or observatory to see these objects. These organizations all have public events where families can visit and look through
scopes. Check out this searchable database from Sky & Telescope magazine to find one in your area.
One of the features of the planets is that they all lie along the ecliptic, which is a circle in the sky that roughly corresponds to the plane of the solar system. So each month, the Moon passes by each of the planets. Since Jupiter and Saturn are currently so close together, look for the Moon to pass between these planets over a span of successive evenings. Here's how the scene appeared last month, in July,
2019.
A similar scene repeats this month, when the waxing gibbous Moon passes near Jupiter on the evening of Friday, August 9. On the next day, Saturday, the Moon will appear between Jupiter and Saturn. By Sunday evening, August 11, the Moon will have shifted further to the east, appearing to draw close to Saturn. The Moon's conjunction (or closest alignment) with Saturn will occur many hours later, when it is
daytime over the USA. Observers in the Pacific, including Australia and New Zealand, will see an occultation of Saturn by the Moon, which happens when the Moon's face passes over the planet, blocking the view for a time.
Keep your eyes on the Moon and planets through the next month when you'll see another pair of lunar-planetary conjunctions in September. The First Quarter Moon draws close to Jupiter on the evening of Thursday, September 5, and the gibbous phase is seen on either side of Saturn on the following Saturday and Sunday, September 7 and 8.
If you've been following Jupiter and Saturn over the last several years, you may now notice that these planets were not so close together in recent times. Due to the movements of the planets in their orbits, Jupiter and Saturn are slowly drawing into alignment with each other. This is because of the relative speeds of their orbits.
According to Kepler's Laws of Planetary Motion, planets move faster in their orbits if they are closer to the Sun. Conversely, the further a planet is away from the Sun, the slower it moves.
Jupiter is quite far from the Sun at 5 astronomical units, and a "year" on Jupiter is as long as 12 Earth years. So Jupiter is seen passing through the zodiac at the leisurely rate of one constellation to the east per year. This is why Jupiter was passing through Libra last year and is now in Scorpius in 2019.
Saturn is nearly twice as far from the Sun as Jupiter, 9.5 astronomical units, and thus the Saturn "year" is 29.5 years in length. Saturn therefore requires more than two years to move through a single zodiac constellation.
At this rate, Jupiter "catches up" with Saturn after a span of years. About every 20 years, Jupiter and Saturn line up in a rare planetary conjunction. At this time, Jupiter and Saturn are lined up with each as seen from the Sun.
The conjunction of Jupiter and Saturn will occur on December 21, 2020. But at that time, these planets will line up quite close to the Sun, as seen from the Earth.
Over the next year, Jupiter and Saturn will be steadily moving closer and closer toward convergence. During the summer of 2020, it should be a lot of fun to watch these two planets draw together into alignment. By December, 2020, this planetary pair will be hanging low in the evening sky, soon to disappear into the sunset. On the evening of December 16, 2020, the waxing crescent Moon will align with these
planets, making an amazing sight in the twilight sky on the threshold of winter.
Jupiter and Saturn last aligned on May 21, 2000. After the date of conjunction in 2020, Jupiter will progress to the east and draw further and further away from Saturn throughout the decade of the 20s. After that, the two planets will approach each other through the 30s, reaching conjunction again on November 5, 2040.
Beyond that, Jupiter-Saturn conjunctions will occur on April 10, 2060, March 15, 2080, and September 24, 2100. This is something to discuss with your grandchildren! But for those of us "of a certain age," the 2020 conjunction might be our last chance to see Jupiter and Saturn align! It's not too early to circle that date on your calendar!
Til next time, God bless and clear skies, -
jay The Ryan Family Cleveland, Ohio, USA When I consider thy heavens, the work of thy fingers, the moon and the stars, which thou hast ordained, what is man that thou
art mindful of him? and the son of man, that thou visitest him? - Psalm 8:3-4, a Psalm of David
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