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Early April Astrominute

Here is the text of the latest Hatter Planetarium – WZBT astrominute. In addition to the radio station, you may also listen here.

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Here is your Gettysburg astrominute for the first half of April, 2016. On the first of the month, the sun rises at 6:52 AM and does not set until after 7:30, eastern daylight time. In the first few days of the month, the moon will be a waning crescent in the predawn sky. A couple days after the New Moon on April 7, it will emerge into the evening sky as a growing crescent. It reaches first quarter on April 14th. The planet Jupiter is dominating the night sky right now. Already high in the east as darkness falls, it culminates about 60 degrees up in the south at 11:30 PM. Toward the middle of the month, sky-watchers have the chance to see Mercury, when it will have its best evening appearance of the year. Go out on clear evenings starting April 8.
Mercury and moon, April 8, 8:00 PM

At 8:00 PM Mercury will be just north of west and about 12 degrees above the horizon. On that evening, it happens that an extremely thin crescent moon will be just to the left of Mercury. Though the planet is relatively bright, so is the glow of the sunset, so binoculars may help. A flat and obstruction-free horizon is a must as well. Of course the sky gets darker as the minutes pass, but Mercury gets lower, setting about 8:45. At its highest on April 18, the planet will be 17 degrees above the horizon at 8:00 PM. Good luck! The astrominute is a production of Gettysburg College’s Hatter Planetarium and WZBT. Text and images are available on the Gettysburg Skies blog.

April 9, 8:00 PM

April 18, 8:00 PM

 

Special Leap Day Astrominute

Sorry, I haven’t posted on of these in while. Hope you’ve been hearing them on WZBT. This one’s all about Leap Day – there may be more to it than you think.

MP3 here: http://public.gettysburg.edu/~iclarke/hatter/podcasts/astrominute022516.mp3

Text below:

Here is a special Gettysburg Astrominute for Leap Day. There it sits, at the bottom of your calendar: February 29. The story of our leap day goes back to the days of Julius Caesar, who had a problem to solve. The poor Romans, with their 355-day calendar, had to periodically add days (to February, usually) to keep their agricultural festivals occurring in the right season. In 46 BC the Julian reforms regularized the practice to one day every four years. If you think that’s the system we used today, you’d be wrong. A seasonal year is actually about 11 minutes less than 365.25 days, and by the 1500s, this error had added up to ten days. Reforms under Pope Gregory XIII added in the missing ten days and introduced a couple of tweaks that result in 97 leap days every 400 years – enough that a calendar year and a seasonal year are now practically the same. The tweaks were to skip leap years in century years, except those divisible by 400. Thus, 1900 was not a leap year, but 2000

was. The new system was adopted right away in Catholic countries, but not so fast elsewhere. Great Britain and its colonies held out until 1752. Folks living then, our founding fathers included, got to decide which birth date to use, old style or new. Russia did not adopt the reforms until after the 1917 revolution, meaning that, as far as most of the world was concerned, the October revolution happened in November. The astrominute is produced by Gettysburg College’s Hatter Planetarium and WZBT.

Show Sunday at 4:00 PM

Coming up at the Hatter Planetarium . . .
THE SKY THIS MONTH
Sunday 2/28 at 4:00 PM. The show will feature

  • Leap day and related arcane lore of the calendar
  • the opposition of Jupiter
  • the vernal equinox
  • and FINALLY. . . exciting news about our planetarium!

The planetarium is located in Masters Hall, room 115. The show lasts about 50 minutes and all are welome.

Spring 2016 Hatter Planetarium Schedule

UPDATE: Show Sunday 1/24 is cancelled! We are going to stay out of the way while Facilities gets the campus ready for Monday. Stay safe!

It’s that time of year. The spring semester is underway and once again we look forward to presenting a monthly sky show in the Hatter Planetarium. Here are two notes about the schedule. First, we’ll be doing just one show a month. This seems to fit our audience size the beast, and additionally we have a project in the works that we hope to be able to share with you soon. Second, all shows are on a Sunday at 4:00 PM, except for the one on Sunday, May 1, which is now scheduled for 5:00 PM. This is because your humble planetarium director will be giving a final exam until 4:30, and he really does not want to miss that last show of the year!

We hope to see you for our first show of the semester, this Sunday, January 24, at 4:00 PM. We hope the potential weekend snow is off the sidewalks and parking lots by then. We will be talking about winter stars in the evening sky, planets in the morning sky, and looking ahead to the astronomical highlights of 2016.

You can also see the schedule as a PDF and a Google calendar.

The Sky this Month

February Skies

●    Sunday, January 24,  4:00 PM
March Skies
●    Sunday, February 28, 4:00 PM
April Skies
●    Sunday, April 3, 4:00 PM
Summer Skies
●    Sunday, May 1, 5:00 PM*
*Note change: +1 hour due to final exam schedule.

The Great Christmas Full Moon of 2015!

Here is my take on this year’s December 25 full moon. It’s expanded from a paragraph that will be appearing in my “What’s Up” Gettysburg Times column this month and includes some material from our December planetarium show. –Ian Clarke
One calendrical oddity that may get some press this holiday season is the full moon on Christmas Day, something that you will hear has not occurred since 1977 and will not again until 2034. If nothing else, it’s a great occasion to dig a little deeper into the moon cycle. 
The lunar cycle has been a bit troubling to human calendar makers, because at first blush it seems it might fit into the solar year. 12 lunar months make up about 354 days. Unfortunately, if you want to keep track of the seasons of the solar year, an 11-day annual error is a pretty big problem. Our Gregorian calendar is therefore a solar one, with a nod to the lunar cycle in the form of weeks and months. These approximate the moon’s quarter and full phase cycle, but not in any way that would actually allow you to keep track of them. The actual phase cycle from one full moon to next is 29.53 days. An average month in our calendar is just under 30.44 days, so a given moon phase slips backward about nine-tenths of a day per month when averaged out over our uneven months.
If you are satisfied with the moon appearing roughly full on Christmas (or any other specific date), you don’t need to wait too long. Any full moon within two or three days will do. The moon was near full on December 25 in 2007 (full the 24th) and 2012 (28th) and will be again in 2018 (22nd) and 2023 (27th). 
If on the other hand, you are looking for the moment of full moon to fall exactly on a given date, you must learn about the metonic cycle. As we saw, 12 lunar cycles don’t fit evenly into one solar year, but if you wait long enough, you can find a pattern. 235 lunar phase cycles is almost exactly 19 years (6,939.688 days vs.6,939.602 days). Pretty neat! It’s called a metonic period. Does that mean a full moon will recur on a given date every 19 years? Almost. Because the match is not exact and because of our leap years, some 19 year intervals are skipped. We have not had a full moon on December 25 in 38 years, so we must have skipped 1996. Then the moon was full on December 24 at 20:41 Universal Time. It missed by a little over three hours. We won’t miss any metonic cycles in the 21st century, so see you, or your heirs, again on December 25, 2034, 2053, 2072, and 2091.
Here is a final complication. Astronomically speaking, the moon is counted as full only for an instant – in this case, December 25 at 11:11 Universal Time. That is 6:11 AM EST, so to see this Christmas full moon in eastern North America, you’ll need to be up before sunrise. And in Europe it will be the middle of the day, and the moon, though full, won’t even be up. Thinking along those lines, we earthlings did not exactly miss the 1996 Christmas full moon either. When the moon was full on December 24 at 20:41 UT, it was already December 25, local time, in Australia and much of the rest of the Eastern Hemisphere.

Astrominute for Late November

Below is a text version of the new Gettysburg Astrominute, with some iillustrations. You can listen to the astrominute here and several times a week on WZBT, Gettysburg’s address for the best new music!  

Here is your Gettysburg astrominute for late November 2015. The sun rises on Nov 15 at 6:53 AM and sets at 4:53 PM. On the 30th it rises at 7:10 and sets at 4:45. The moon phase will be growing during most of  the two week period – starting as a waxing crescent, reaching first quarter on the 19th and full on the 25th. The Leonid meteor shower will be peaking on Nov 17 to 18. Go out from midnight to dawn on either morning and you may see up to 10-15 meteors per hour. And while you’re up early, check out the bright planets in the east before sunrise. Jupiter is now the highest, with Mars, and then Venus below it. Venus is the brightest; next Jupiter and then Mars. Let’s not neglect the evening sky. The bright star Capella and the Pleaides (or 7 sisters) star cluster are both rising in the east around dark. Aldebaran, the eye of Taurus the Bull, follows about an hour later. Then the familiar constellation Orion the Hunter will be entirely up by 9 PM.  The astrominute is produced by Gettysburg College’s Hatter Planetarium and WZBT 91.1 FM. For a text version of the astrominute, with illustrations, visit the Gettysburg Skies blog.

5:30 AM on November 20

9:30 PM on Nov 20

Late October Astrominute

Julia Giannini reads the latest Astrominute

Below is a text version of the new Gettysburg Astrominute, with some iillustrations. You can listen to the astrominute here and several times a week on WZBT, Gettysburg’s address for the best new music! 
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Here is your Gettysburg astrominute for late October 2015. The sun is now setting before 6:30 PM Daylight Time, but be ready for that to jump back an hour when we switch to Standard Time on November 1. The moon is prominent right now–first as a waxing crescent in the western evening sky but reaching first quarter on Oct 20 and Full on the 27th. There are no bright planets in the evening right now, but to compensate there’s a great show going on in the predawn sky, where you can see Venus, Jupiter, Mars, and even Mercury. Get outside around 6:30 AM to a place with a flat eastern horizon. Venus will be by far the brightest thing you see in the east. In the middle of the month, it is also the highest, but that will change. Below Venus and a bit left are Jupiter and Mars, with Jupiter the brighter of those two. You might also see Mercury just a few degrees above the eastern horizon. By the last week of the month, Mercury will drop from sight, but watch as Jupiter and Mars close the gap with Venus. On the 25th and 26th, Venus and Jupiter will be as close as the width of a finger at arm’s length. Then in the first days of November it will be Venus and Mars in conjunction, with Jupiter a few degrees above them. We hope you can get up early and enjoy the sight! The astrominute is a production of Gettysburg College and WZBT. 
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Here are some helpful illustrations for our location, created with Stellarium. The first shows the view, looking east, on Oct 17 at 6:30 AM. Grid lines are 10 degrees (about a fist-width) apart.

 In the view below, on the morning of the 25th, Mars and Jupiter have moved higher while Venus is holding fairly steady. Jupiter catches up to Venus while Mars is just below.

In the final scene, November 3 at 5:30 AM (note the switch back to standard time) Mars catches up to Venus while Jupiter is above. Both planets will be plainly visible, but at magnitude -4.3 compared to Mars’s 1.7, Venus will be much brighter. How much brighter? Each magnitude is 2.5 brighter than the next higher one, so about 250 times brighter!

2.5^(1.7 – -4.3) = 244.14


Early October Astrominute


Below is a text version of the new Gettysburg Astrominute, with some iillustrations. You can listen to the astrominute here and several times a week on WZBT.
Here is your Gettysburg astrominute for the first half of October, 2015. On October 8 (the middle of our astrominute period) the sun will rise at 7:12 and set at 6:41, eastern daylight time. The moon will not be in the evening sky – it reaches Last Quarter on October 4 and New on the 13th. As it gets dark, the Summer Triangle is overhead, dominating the sky. Meanwhile, look for the Great Square of Pegasus in the east. [Check out www.skymaps.com for a downloadable monthy map.]
The best show right now, however, is in the morning sky. Venus stands brilliantly in the east before sunrise, and below it the planet Jupiter is coming into view. Though fainter, Mars and the star Regulus are both nearby. Better yet, the waning crescent moon will be passing through on the 8th through the 10th. Look for the crescent moon, 17% illuminated, near Venus on the 8th.

10/8, 5:45 AM. 10 deg. = fist at arm’s length.

As it gets closer to the sun each morning, it will be near Jupiter and 11% illuminated on the 9th, and below Jupiter and only 6% illuminated on the 10th. That is still 70 hours before new moon on the 13th, so quite visible if you go out before 6AM. If you’re an early riser, you might also notice that Jupiter and Venus are drawing close together. They will be very close indeed at the end of the month. More on that next time. The astrominute is a production of Gettysburg College’s Hatter Planetarium and WZBT. For a text of the astrominute, with illustrations, visit the Gettysburg Skies Blog.

Images created with Stellarium.

10/9

10/10.

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