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.
Be watchful and strengthen the things which remain....
- Revelation 3:2(a)
When you gonna wake up, when you gonna wake up
When you gonna wake up, strengthen the things that remain ?
- Bob Dylan
IN THIS UPDATE
Independence Day Penumbral Eclipse
Jupiter and Saturn Align in 2020
Hello Friends,
As you can see, the Classical Astronomy Update is back for yet another edition after all these years. I've been creating this newsletter in some form since 1996, and specifically for homeschoolers since 2002. I've been wondering for some time whether it should continue. Nowadays most people use the internet over their phone. I get many complaints lately that this newsletter is too long to read on a
phone. People today want smaller, tweet-sized bites of info. Perhaps the American attention span has grown so short that maybe an email newsletter has outlived its usefulness. Still pondering the destiny of these increasingly infrequent missives, but thanks to everyone who has stuck around this long.
This newsletter is for astronomy information, not for my opinion or for editorializing. But many things have quickly transpired following recent events in the USA and around the world. At this rate, I wonder what changes another year might bring.
They say history is written by the winners. But we see on the daily news that certain elements are hard at work to destroy our history and replace it with a rewritten narrative. Here on the 244th anniversary of American independence, I would encourage you all to prayerfully consider how conscientious American citizens should respond, and how we might "strengthen the things that remain." We all need to decide for
ourselves, whether through action or inaction, who will be the winners that will write the future history that will be learned by our great-grandchildren.
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.
*****
Independence Day Penumbral Eclipse
Many of you remember the "Blood Moon" fiasco of 2014 and 2015, which was extensively discussed in this newsletter. That pop eschatology entailed a "tetrad" of four consecutive total lunar eclipses. That was a rare instance since such tetrads are infrequent. The last total lunar eclipse visible from North America happened in January, 2019, and there will not be another seen here until May, 2021. However, there
are always at least two lunar eclipses of some type each year. The good news is, there are four lunar eclipses in 2020. The bad news is, they are all penumbral.
During a total lunar eclipse, the entire Moon passes through the umbra or full shadow of the Earth. As seen from within the umbra, the view of the Sun is completely blocked by the body of the Earth, so that the Moon is plunged into darkness. The same thing happens during a partial lunar eclipse, but only a portion of the Moon passes through Earth's umbra, appearing as a darkening along a portion of the lunar
limb. The darkening during total and partial lunar eclipses is very apparent and these events can be quite dramatic.
On the other hand, a penumbral eclipse occurs when the Moon passes through the penumbra or partial shadow of the Earth. The view from within the penumbra is of a partial solar eclipse. So there is still sunlight shining on the Moon while it passes through the Earth's penumbra. Total and partial lunar eclipses have a penumbral phase when a dimming of the bright lunar surface is visible while the Moon
passes through the penumbra and approaches the umbra.
During a penumbral eclipse, you never see the dark edge of the Earth's umbra on the surface of the Moon. You can only notice a dimming along the edge of the bright glare of the Full Moon. Instead of shining like a uniformly bright circle, as with a normal Full Moon, you can notice an asymmetry in the lunar brightness as a portion of the Moon's limb skims through the penumbra. It's not an impressive sight but it
is noticeable, especially if one is a regular observer of the Moon.
The upcoming penumbral eclipse will begin in the late night hours of Saturday, July 4, especially for those in the eastern time zone. Look after midnight when the penumbrally eclipsed Moon is at its highest above the horizon. This event will occur at a more favorable evening hour for those in the Pacific time zone, where maximum eclipse occurs at 9:30 PM, not long after dusk twilight. However, the Moon will be
low in the sky and the penumbral dimming may not be as apparent as seen back east.
(Please note that the dimming depicted in the image below is exaggerated. The actual penumbral dimming will only be seen as a reduction in the uniform brightness along the north limb of the Moon.)
Jupiter and Saturn Align in 2020
As reported in this newsletter over the last couple years, Jupiter and Saturn have been drawing close to each other in the sky. Both of these gas giant planets are in the outer solar system, and they thus move much slower than Earth and the other "terrestrial planets" of the inner solar system. Jupiter requires 12 years to complete a single orbit around the Sun, while Saturn takes 29.5 years to revolve one time around
the solar body.
As a result, Jupiter is plodding along at a slow rate in its orbit, but Saturn is plodding even slower. As seen from the Earth, it takes several years for these planets to drawing together and approach the same line of sight. And then Jupiter and Saturn will briefly align after which Jupiter will pass Saturn and then slowly draw away over the span of several years.
In recent months, Jupiter and Saturn have been visible in the morning sky before sunrise. But the steady seasonal progression of the constellations is finally bringing these planets back into view in the evening sky. Jupiter and Saturn will become evening objects after opposition in which they are at positions in the sky opposite the Sun (hence the name), rising in the evening after sunset.
During opposition, the Sun, Earth and planet essentially lie along a straight line. The opposition of Jupiter occurs first, on Tuesday, July 14, 2020. The opposition of Saturn happens six days later, on Monday July 20, 2020.
Jupiter is easy to see in the night sky, being a brightly blazing blowtorch, by far the brightest "star" that can currently be seen in the evening after sunset. Jupiter is the fourth brightest object in the sky, after the Sun, Moon and Venus, which is currently "The Morning Star" seen before sunrise. So you'll have no trouble finding Jupiter rising in the southeast in the hours after the Sun goes down. Saturn
is easy to see in comparison, being a fairly distinct "star" to the east (i.e., the left) of Jupiter (as seen from North America).
Unless one is accustomed to finding Jupiter, many novice skywatchers have trouble believing that that brilliant bright "star" is actually the famous planet that they've seen in NASA photos. So if you're still not sure whether you're spotting Jupiter, you'll have confirmation this weekend.
On the evening of Saturday, July 5, the penumbrally eclipsed Full Moon is seen lying along a line with Jupiter and Saturn. And then the next evening, Sunday, July 5, the waning gibbous Moon clusters up with Jupiter and Saturn in a lunar-planetary conjunction. This will be an interesting sight in the sky. Be sure to take a look. You can also follow the Moon in following nights as it draws away to the east
from this planetary pair.
Even a small telescope is sufficient to reveal the famous Moons of Jupiter and Rings of Saturn. If you don't have a telescope, you might find a local astronomy club or planetarium delivering an outdoor telescope program where you can see these celestial sights using someone else's telescope. (However, such programs may be cancelled under the current circumstances. If so, you'll have amply opportunity next year
and into the future.)
Jupiter and Saturn will remain a combo in the evening sky for the remainder of 2020. As the summer months progress, these bodies will rise higher and higher in the evening sky, being at their highest in the fall. After that, this pair will advance toward the sunset, disappearing into the twilight glare toward years' end. The Moon will pass these planets each month in a series of lunar conjunctions. We
intend to share info on these events on Facebook and Instagram and @JayRyanAstro
on Twitter.
The entire time, Jupiter will draw closer to Saturn, as these bodies approach alignment in their planetary conjunction. The actual date of their conjunction is December 21, 2020, the winter solstice. By this time, Jupiter and Saturn will be quite low in the evening sky. It might be hard to see them above the trees. A better opportunity will happen a few days earlier, as the waxing crescent Moon passes this pair
on December 16 and 17. We currently plan to have another newsletter by that time discussing this event in detail.
At their closest conjunction, Jupiter and Saturn will be 0.1 degrees apart, a mere 1/5 of a lunar diameter. This is extremely close in celestial terms. It should be easy to see both of these planets together in the field of a telescope eyepiece. I am looking forward to seeing the excellent photos that will likely be shared on social media.
Such an alignment of Jupiter and Saturn only occurs every 20 years. So use this opportunity to become acquainted with these celestial objects in the seasons ahead.
Oh, and also, don't believe every silly story you hear! The last time this happened in 2000, there were apocalyptic theories that the combined gravity of Jupiter and Saturn was going to pull the Earth off its axis! There was a sensationalistic book that sold millions of copies warning of massive shifts in the polar ice caps with earthquakes and tsunamis and the usual "doom and gloom." This was to follow the
calamity of the Y2K in which our computer infrastructure failed from a fatal glitch, resulting in mass devastation. Obviously none of that happened back in 2000, nor did it happen in 1980 or 1960 or before when similar alignments of Jupiter and Saturn occurred. So please be advised of such hoaxsters and don't fill my inbox with emails asking "is this true?" :)
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
|
|
|
|
