This is a Classical Astronomy Alert, a special edition of the Classical
Astronomy Update, an email newsletter especiallyfor Christian homeschool families (though everyone is welcome!)
Please feel free to share this with any interested friends.
When it is evening, ye say, It will be fair weather: for the sky is red. And
in the morning, It will be foul weather to day: for the sky is red and
lowering. O ye hypocrites, ye can discern the face of the sky; but
can ye not discern the signs of the times? - Matthew 16:2b-3
IN THIS UPDATE
Comet NEOWISE
Hello Friends,
As you may have heard, the internet is blowing up this week about Comet NEOWISE, the best comet to visit the inner solar system since Comet Hale-Bopp in 1997. We already had a couple comets fizzle in 2020, Comet SWANN and Comet ATLAS. But three's the charm!
Now I already wrote a newsletter just this month and did not intend to write another for several months. But cometary visitors are very rare and unpredictable, and this is a rare opportunity to help all of you take advantage and see this comet. It's a nice, sunny summer day today, and instead of being outside doing something, I'm staying cooped up inside to write this newsletter! That's because YOU are special
and you rate! So please make it worth my while and use this information to make an effort to see Comet NEOWISE. You may never have another chance to see another comet in your lifetime!
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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Comet NEOWISE
Dumb name, right? We've all heard of the famous Comet Halley, named after Edmund Halley, a colleague of Isaac Netwon. Comets are always named after their discoverers. Which is why Comet Hale-Bopp from 1997 was named after the two independent co-discoverers, Alan Hale and Tom Bopp. Such naming is historic and traditional. However, nowadays, comets are increasingly discovered by satellites and space
probes, far away from the Earth. Such is the case with NEOWISE, which is a mission of the NASA satellite WISE (Wide-field Infrared Survery Explorer) for studying Near-Earth Objects (NEOs), hence the name. The current comet is one of twenty discovered by this satellite.
Satellites have an advantage over humans in detecting remote objects like comets. Unlike humans who eat and sleep and can only view the sky at night, such satellites are above the Earth and can scan the sky 24/7/365. Also, their instruments are much more sensitive than the human eye, with or without a telescope. I find myself wondering these days whether a human will ever discover a comet ever
again.
Comets are often called "dirty snowballs." They are believed to be mostly made of ices (including water ice, CO2, methane, etc.) and particulate matter -- dust, sand and gravel. Comets have highly elongated orbits so that they mostly reside in the cold reaches of space beyond the planets, and only rarely swinging toward the Sun, usually passing close within the orbit of Mercury.
While passing close to the Sun, the ices melt, creating the bright, visible tail that streams away in the direction opposite from the Sun. The less-visible particulate matter also streams away from the comet's head. These particles remain in orbit around the Sun in the same path as the comet. Whenever the Earth passes through one of these streams, the comet debris burns up in the Earth's atmosphere, appearing
as a meteor shower. All of the meteor showers we see are made of cometary particles that cross the Earth's orbit.
Comet NEOWISE is fairly large, but it is VERY FAINT. If you were around for Comet Hale-Bopp, that comet was very bright, an easy sight with the unaided eye even from the light polluted cities. Not so this time. But Comet NEOWISE appears to be much larger in the sky than Hale-Bopp, at least compared to my recollections.
You'll probably not see very much if you're looking for the comet from the city. Even from my preferred location along Lake Erie, viewing over the dark sky of the Great Lakes, the comet looks like a "chalk smudge" like you make with your finger in chalk dust on a blackboard. But you'll likely have a nice enough view if you can observe from a dark rural location, far from the city lights, especially from the desert or
an area with very low humidity.
And wherever you observe, this comet will look AMAZING through binoculars. I made this image after my first observation. It's just what one would expect to see in a comet.
Comets follow all different sorts of orbits, coming toward the Sun from just about any direction, and being inclined to the plane of the solar system at just about any angle. Astronomers speculate that there is a region outside the solar system called the "Oort Cloud" where comets originate. According to the standard narrative, every so often one of these objects are somehow dislodged and go careening toward the
Sun. Some comets burn up in the Sun, many break up along the way, and very few pass close enough to Earth to put on a show. Comet NEOWISE came up from the south and is now north of the plane of the ecliptic, the plane of Earth's orbit. NEOWISE made its closest approach to the Sun -- perihelion -- on July 3. It will make its closest approach to the Earth -- perigee -- on July 23 when it will be a "mere" 64 million miles away. Someone on
Facebook make a joke about "peak 2020" with the comet colliding with the Earth! But at that distance the odds are greater of the planet Mercury colliding with the Earth! (Like I always say, there's a lot of space out in space, and that's why they call it space!)
As seen from space around the neighborhood of Earth, we observe the solar system "edge on." All the planets are visible on or near the the plane of the ecliptic, which is the plane of the Earth's orbit. The constellations of the zodiac also lie along this plane, which is why the Sun,Moon and planets appear to move through these constellations. But the orbit of Comet NEOWISE carries it far to the north
of the plane of the ecliptic so that we'll see the comet passing above the zodiac constellations, and aligning with stars in the far north, particularly the Big Dipper. (For detailed explanations of the ecliptic and the zodiac constellations, check out our Signs & Seasons astronomy curriculum.)
For these reasons, Comet NEOWISE favors observers at locations in the northern hemisphere. This image shows the progression of the comet over the next month. It has been visible in the morning and recently appeared in the evening sky, low in the northwest after sunset. But it is rising higher in the evening sky with each night and appearing to shift toward the south. It will eventually pass over the
constellations Leo and then Virgo. In mid-August, the comet will pass between the bright stars Arcturus and Spica and should be easier to locate. It will also be better placed for observing from the southern hemisphere. However, by that time, the comet will be far away from Earth and the Sun and will appear smaller and likely even fainter than it is now.
Over the next week, the comet will pass below the Big Dipper, and will pass through the stars of Ursa Major, the Big Bear, of which the Dipper is just a prominent portion. This alignment makes finding the comet very easy. And if you're not familiar with the other stars in the Big Bear, the comet gives you a great opportunity to learn the entire constellation.
Over the next week, the comet will pass very close to the "feet" or the "paws" of the Big Bear. Each of these paws are represented by a pair of close stars. You might be able to notice two strings of faint stars that form the "legs." The "head" of the Bear is a real challenge as those stars are very faint. On the night of Saturday, July 18, the comet passes right by the "front paws" of the Big
Bear. The comet will be found in the general vicinity of the paws for this coming week. The comet will then pass by the "back paws" of the Bear on Thursday, July 23, the night of perigee.
This week will be "prime time" for observing Comet NEOWISE! So grab your binoculars and make an effort to see it! And be sure to share this newsletter with all your friends!
If you don't have binoculars, borrow them from a friend. Even a modest pair will work fine. I've always used these cheap 50mm Bushnell binocs that I bought in 1990 for 40 bucks. They have served me fine all these years. You can buy quality binocs at any camera store. And then you can use them for other activities such as birdwatching and general nature observation.
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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