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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.
IN THIS UPDATE:
- Anouncements
- Order Signs & Seasons from Amazon.com
- Video -- Milky Way Rising
- "Mars Spectacular" Email = HOAX!!!
- Dance of the Planets
- Report of Venus Occultation Observation
- Approaching Saturn's Equinox
- Astronomy Topics
Let the stars of the twilight thereof be dark; let it look for light, but
have none; neither let it see the dawning of the day. - Job 3:9
Welcome to the Classical Astronomy Update!
Hello Friends,
Hope you've all been in a good season of life lately. Things have been difficult around our house the last several months. I was quite ill with mono for about a month and then was buried with work from my day job work for a long time afterwards. There were additional problems including ongoing health issues with my mom. Your prayers for our family would be appreciated.
On the bright side, I've been going to the local pool in 2009 and swimming a half mile a few times a week. It feels great, like being 25 again! I think some things that people attribute to "getting old" are the result of just being out of shape for years at a time. For those of you who are also middle aged, I'd encourage you to find a way to make time for walking, swimming, bike riding or anything else to get your blood moving!
Announcements
Order Signs & Seasons from Amazon.com!
If you like to order books from Amazon.com, you'll be glad to know that Amazon Merchants are offering our Signs & Seasons curriculum! Check it out at this link. Thefamilybookspot and PuritanWorks are approved resellers of Signs & Seasons, and thefamilybookspot offers the curriculum in a set with the companion workbook.
Be sure to read the wonderful Amazon reviews of Signs & Seasons from Perla Adams, Wesley Callihan, and C.T. Widger.
Video -- Milky Way Rising
Here is a remarkable video -- a time-lapse, time-exposure movie showing the galactic center of the Milky Way in Sagittarius rising into the sky. This was filmed at the Texas Star Party in April, and you can see people milling around on the ground under red lighting. Too bad the human eye can't actually see this much detail. A much dimmer version of the Milky Way can be seen with the unaided eye on any clear night from a suitable dark sky location.
"Mars Spectacular" Email = HOAX!!!
If you've been reading the Update for a couple years, you know that it has become an annual tradition to circulate this "Mars Spectacular" email, claiming that Mars will appear as large as a Full Moon this August. The twist this year is to package this bogus story in a 5 meg powerpoint slideshow.
Don't believe it, it's a total hoax. More importantly, please don't send me three hundred copies of this email asking "Is this true?" If it were, you'd hear it here first! This email follows the basic rule, "don't believe things you only hear via email."
Dance of the Planets
Report of Venus Occultation Observation
We didn't have a chance to write an Update during April, but there was an uncommon morning occultation of the Moon with Venus on April 22, where the Moon passed in front of the bright morning star. This event was visible from the western USA. We received this colorful report from Carol Widger, an amateur astronomer from the west coast. Many thanks to Carol:
Venus occultation 4/22/09
I've seen Saturn near the moon before, and conjunctions and near misses. and watched star occultations by the dozen. But this morning's Lunar Venus meeting must have been the single most beautiful event I've seen for a long while. I hurried my 4:30 AM routine a bit this morning, and found a spot down the second floor apartment walkway with a view between some trees to the east by 505a. This morning was like summer, that calm, bell clear weather , light and warm. Robins and mocking birds traded sleepy gossip in the trees to the south. The clockwork accuracy of the heavens never ceases to amaze me.
The moon swung low, just grazing the hills to the east, dusky and rounded through the morning atmosphere. The raggeddy southern edge cleared the treetops,. and some snowy reflection seemed to dust the north arm of the crescent in the earthshine. Like a diamond on shining ring, Venus hung just edging the moon in the 7 o'clock position. With the Swift 60mm F8.5 scope and the Faworski 10mm Ortho, one could not have asked for a better view or a more beautiful part of the day. No time to run down and get Don (I'm forever trying to hook him on stargazing ) so a solo watch as Venus slid behind the moon. It was time to throw together a lunch and walk to work. Fortunately , most of the mile was to the east, then south. I kept watch with the binoculars on the way for Venus to pop back into view, but that did not happen till after I'd opened up the station at 6, gotten the coffee and settled down to the paperwork... A fragment of a second's glance away, then back again, and there she was.
The early morning commuter has little interest in astronomy, or for that matter anything but coffee and traffic. But no one could deny the beauty of the smiling Luna and her distant friend this morning.
Clear skies and renewed wonder!
Carol
The Moon Passes Saturn - May 31
As the days grow longer, the evening constellations continue their movement toward the sunset over the passing weeks and months. Following its seasonal motion, the constellation Leo is now in the western sky after evening twilight, and will soon disappear into the dusk as the days turn to summer.
Since the ringed planet Saturn is currently inhabiting the stars of Leo, Saturn has also moved into the western part of the sky in the evening. The First Quarter Moon will swing wide below Saturn over the evenings of Saturday, May 30 and Sunday, May 31. Though the Moon will not be very close to the ringed planet, this is an opportunity to observe the Moon's motion from night to night.
Astronomy Topics
Twilight
Twilight is that brief part of each day in between day and night, when the Sun's rays light up the sky, but the Sun itself is below the horizon. Dawn twilight is in the morning before sunrise, when the Sun's glow chases away the night, when the early sky is tinged by Homer's eos daktylos, "rosy-fingered dawn." Dusk twilight is on the other side of the day, when the ruddy glow of the sunset persists after the Sun itself has sunk below the horizon.
Twilight is my favorite time of day. Twilight is a rare, precious part of each day, a brief period of perhaps 45 minutes separating the Sun's rays of daylight and the full shadow of night. Twilight is the most changeable part of the day. Daytime offers a consistent blue sky as the Sun races from east to west. Nighttime is uniformly dark, only distinguished by the rotation of the stars across the sky. But during twilight, the sky quickly transitions from the brightness of day to the full darkness of night in less than an hour.
Twilight offers a range of colors -- brilliant hues of red, yellow, pink and orange that rapidly change to deepening shades of blue. After sunset, the first stage of twilight is civil twilight, when the sky is very bright and the clouds are painted beautiful shades of color. During civil twilight, the entire sky is lit up with the Sun's light, and the land retains a dim daylight quality, though the Sun's rays are not visible and shadows cannot be seen. In the evening, civil twilight is the first stage of twilight after the sunset, and in the morning, the last stage before the sunrise.
In the evening after sunset, the next stage is nautical twilight, when the brightest stars begin to appear. At this time, the streetlights begin to come on for most city dwellers. The sky has lost most of it's orange color, except perhaps for a fading patch to mark the place of Sun. The sky has become a deep turquoise blue, brighter toward the Sun's direction. Nautical twilight is so-named because it is during this stage that sailors can first find the "navigator's stars" used for finding direction at night.
The final stage of twilight after sunset is astronomical twilight. At this stage, the sky grows ever darker, and the stars begin to come out in great numbers. A dwindling patch of twilight remains along the horizon to mark the Sun's position. A keen eye will notice that this patch is not in the same place as the sunset, and indicates that the Sun has moved below the horizon since going down. Twilight ends when the last patch of sunglow has vanished from the horizon, and full astronomical night commences.
Seasonal and Global Variations in Twilight
The length of twilight varies over the span of the year, and also with latitude around the earth. In the springtime and autumn, near the equinoxes, twilight is shortest. As seen from the ground, the Sun appears to follow a very direct path below the horizon after the sunset, and so the Sun and its rays quickly dip out of sight during the spring and fall. As a result, night falls quickly near the equinoxes.
During the summer, the period of twilight is longest. The Sun appears to take a slanting path toward the horizon. The Sun follows a shallow path below the horizon, and a patch of astronomical twilight can be seen far from the place of the sunset, in some places longer than an hour after Sun's disappearance, depending on location.
During the winter, the twilight is longer than at the equinoxes, but not as long as during the summer. These changes in twilight result from the varying angle of the Earth's axis to the Sun as the Earth follows its orbit around the Sun over the course of the year. For more information, check out this astronomy cartoon from the SkyWise Archive:
The length of twilight can vary considerably depending on latitude over the Earth. Twilight is shortest at the Equator and longest at the North and South Poles. On the Equator, the entire sky appears to lie on its side. The Sun sets perpendicularly to the horizon, and drops quickly out of sight after sunset. Therefore, the period of twilight is very short. Vacationers and newcomers to the tropics such as new missionaries are often amazed at how quickly night falls in these warm latitudes.
In the temperate latitudes, where most of the world's population resides, the Sun approaches the horizon at an angle. Thus, the Sun takes a longer, slanted path as it dips below the horizon, and twilight takes a longer time to fall. As one moves north or south toward the poles, the length of twilight increases.
At latitudes above 48 degrees, the "white nights" can be observed during the longest days of summer. The evening twilight merges with the morning twilight so that some trace of daylight can be seen at midnight! The white nights can be observed from the northern border of the continental USA, most of Canada, and places in northern Europe and Asia such as Great Britain and Russia.
In the polar regions, continuous daylight and nighttime persist for long periods of time. However, around the equinoxes, the maximum global interval of twilight can be observed at the North and South Poles. Each year, following the long polar summer, the Sun begins to set at the North Pole on the autumnal equinox, September 23, and finally sets two days later, on September 25.
The Sun goes through the stages of twilight over a span of several weeks, passing from civil twilight to nautical twilight and astronomical twilight. Finally, on about November 15, the Sun has reached far enough below the horizon that twilight ends and full night commences! Full darkness only lasts a couple months during the long polar night, and twilight commences once again around the end of January, and brightens steadily until the vernal equinox on March 21. For more information, check out this astronomy cartoon from the SkyWise Archive:
As the days warm up in your area, plan some outdoor activities during the evening twilight! Make it a point to observe the stars as they appear one by one. Be sure to bring plenty of bug spray!
Coming in future Classical Astronomy Updates:
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In 2009, we will celebrate the Quadricentennials of Galileo and Kepler.
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In July, 2009 we will commemorate the 40th anniversary of the Apollo 11 moon landing.
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The Earth will cross the ring plane of Saturn on September 4, 2009, and event that only occurs every 15 years.
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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