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Posts Tagged ‘Winter Solstice’

12/22/2020 – Ephemeris – Winter is going to be colder before it starts to warm up in a little over a month

December 22, 2020 Comments off

This is Ephemeris for Tuesday, December 22nd. Today the Sun will be up for 8 hours and 48 minutes, setting at 5:05, and it will rise tomorrow at 8:18. The Moon, 1 day past first quarter, will set at 1:47 tomorrow morning.

Now that winter is here, it’s going to get snowier and colder even though the amount of heat the Northern Hemisphere gets from the Sun bottomed out yesterday. There are two consequences of the Earth’s axial tilt with regard to the Sun on the winter solstice. First, the Sun is only up 8 hours 48 minutes. Second at its highest at local noon the Sun is so low, only 22 degrees above the horizon around here that its heat is spread out over a greater area so is diluted to only 40% of the peak heat we get from the Sun at noon on the summer solstice. And on the summer solstice the Sun stays up almost six and three-quarters of an hour longer. Even though it doesn’t feel like it at our latitude winter is 4 days shorter than summer. You’ll find out why in less than two weeks.

Addendum

Solstices

Comparing the sun’s path at the summer and winter solstices. This is a stereographic representation of the whole sky which distorts the sky and magnifies the size of the sun’s path near the horizon.

Earth's position at the solstices and equinoxes

Earth’s position at the solstices and equinoxes. This is an not to scale oblique look at the Earth’s orbit, which is nearly circular. The Earth is actually farthest from the Sun on July 4th. Click on the image to enlarge. Credit: ESO (European Southern Observatory which explains the captions in German and English.

 

12/18/2020 – Ephemeris – Winter begins Monday morning

December 18, 2020 Comments off

This is Ephemeris for Friday, December 18th. Today the Sun will be up for 8 hours and 48 minutes, setting at 5:03, and it will rise tomorrow at 8:16. The Moon, 3 days before first quarter, will set at 9:29 this evening.

Monday will host two astronomical events. The second will be the extremely close conjunction or appearing together of the planets Jupiter and Saturn, which I’ll talk about then. But first, at 5:02 Monday morning winter will begin with the winter or December solstice. The word solstice means Sun stand still. On or about December 21st, the Sun appears to stop moving southward measured at noon and will begin moving northward again. All this is the result of the Earth’s 23 ½ degree axial tilt and our motion around the Sun. Our area of the globe is now receiving less energy from the Sun to support our temperatures, and they will continue to fall for the next month or so even as the Sun rises higher and stays out longer.

The event times given are for the Traverse City/Interlochen area of Michigan. They may be different for your location.

Addendum

Winter solstice

The sun’s daily path through the sky from horizon to horizon on the first day of winter, the winter solstice. Credit My LookingUp program.

 

12/22/2015 – Ephemeris – Welcome to winter, or summer if you’re down under

December 22, 2015 Comments off

Ephemeris for Tuesday, December 22nd.  The Sun will rise at 8:17.  It’ll be up for 8 hours and 48 minutes, setting at 5:05.   The Moon, 3 days before full, will set at 5:59 tomorrow morning.

Today is the first full day of winter.  For folks south of the equator this is the first full day of summer.  The Earth reached a point in its orbit where its north pole is tipped its furthest away from the Sun, and is in shadow in the middle of it’s six month night.   We do see the Sun, though less than 9 hours of daylight, and to boot the Sun only rises 22 degrees above the horizon giving us the least amount of energy of any day of the year.  Why did the ancients celebrate this time of year?  That’s because the Sun had slowed and stopped its drift southward and was beginning to come back higher in the sky.  They still had to go through the worst of winter, but the Sun was coming back.  Spring and summer would eventually return!

Times are for the Traverse City/Interlochen area of Michigan. They may be different for your location.

Addendum

Solstices

Comparing the sun’s path at the summer and winter solstices. This is a stereographic representation of the whole sky which distorts the sky and magnifies the size of the sun’s path near the horizon.

The above chart shows the diurnal path of the Sun at the winter and summer solstices for Traverse City, MI near 45º north latitude.  Peak Sun altitude at noon at the winter solstice is 22º, while it’s 69º at the summer solstice.

 

 

12/21/2015 – Ephemeris – Except for 12 minutes today is the last day of autumn.

December 21, 2015 Comments off

Ephemeris for Monday, December 21st.  The Sun will rise at 8:16.  It’ll be up for 8 hours and 48 minutes, setting at 5:04.   The Moon, 3 days past first quarter, will set at 4:50 tomorrow morning.

Here we are at the mostly last day of autumn.  The last 12 minutes will be the start of winter.   The winter solstice will occur at 11:48 this evening, here in the Eastern Standard Time Zone.  Next year winter will start 18 hours earlier.  The reason is that next year is a leap year and the addition of an extra day will push all the solstices and equinoxes back by about 18 hours.  Why only 18 hours?  18 hours is three-quarters of a day, and by this time next year we will have used up a quarter of that adjustment already.  The Earth takes approximately 365 and a quarter days to orbit the Sun, so a day is added every 4th year, except century years not divisible by 400.  I’ll discuss more about the implications of the solstice tomorrow.

Times are for the Traverse City/Interlochen area of Michigan. They may be different for your location.

Addendum

The Earth near December solstice

Not quite the solstice, this is the Earth on December 16th, 2015 taken by the EPIC camera on the DISCOVR spacecraft at the Sun-Earth L1 point, some 1.5 million miles (1 million km) from the Earth.  Credit:  NOAA.

 

12/01/2015 – Ephemeris – Previewing December skies

December 1, 2015 Comments off

Ephemeris for Tuesday, December 1st.  The Sun will rise at 7:59.  It’ll be up for 9 hours and 4 minutes, setting at 5:03.   The Moon, 2 days before last quarter, will rise at 11:13 this evening.

December is the month with the shortest daylight hours.  Winter will officially arrive at the winter solstice on the 21st at 11:48 p.m.  There will be little movement in the sunset times: In the Traverse City/Interlochen area this will be from 5:03 tonight, down to 5:02 and then advancing to 5:11 at the end of the month.  There is more movement in the sunrise times which will advance from 7:59 today to 8:20 on the 31st.  There is also little movement of daylight hours.  The noontime sun will hang around 22 to 23 degrees above the southern horizon all month.  We have some great events this month, from an occultation of Venus by the moon on the 7th, to the Geminid meteors on the 14th and Comet Catalina will be seen in binoculars on mornings all this month.

Times are for the Traverse City/Interlochen area of Michigan. They may be different for your location.

Addenda

December 2015 Star Chart

Star Chart for December 2015. Created using my LookingUp program. Click on image to enlarge.

The planets and stars are plotted for the 15th at 9 p.m. EST.  That is chart time.  Note, Traverse City is located 45 minutes behind our time meridian.  To duplicate the star positions on a planisphere you may have to set it to 45 minutes earlier than the current time.

Evening astronomical twilight ends at 6:48 p.m. EST on December 1st, decreasing a minute 9 days later before increasing to 6:57 p.m. EST on the 31st.

Morning astronomical twilight starts at 6:15 a.m. EST on December 1st, and increasing to 6:34 a.m. EST on the 31st.

Add a half hour to the chart time every week before the 15th and subtract and hour for every week after the 15th.

For a list of constellation names to go with the abbreviations click here.

  • Pointer stars at the front of the bowl of the Big Dipper point to Polaris the North Star.
  • The Summer Triangle is still up and is shown in red.
  • GemR is the Geminid meteor shower radiant

Calendar of Planetary Events

Credit:  Sky Events Calendar by Fred Espenak and Sumit Dutta (NASA’s GSFC)

To generate your own calendar go to http://eclipse.gsfc.nasa.gov/SKYCAL/SKYCAL.html

Times are Eastern Daylight Time.  Some additions made to aid clarity.

Date	   Local  Event
           Time EST
Dec 01 Tu         Venus: 43.3° W
    03 Th  2:41am Last Quarter
    04 Fr  1:21am Moon-Jupiter: 2° N
    04 Fr  1:33pm Moon Ascending Node
    05 Sa  9:56am Moon Apogee: 404800 km
    05 Sa  9:40pm Moon-Mars: 0.1° N - Occultation **
    07 Mo 11:55am Moon-Venus: 0.7° S - Occultation *
    11 Fr  5:29am New Moon
    12 Sa  3:15am Moon South Dec.: 18.4° S
    14 Mo 12:48pm Geminid Shower: ZHR = 120
    17 Th  9:32pm Saturn-Antares: 6.2° N
    18 Fr 10:13am Moon Descending Node
    18 Fr 10:14am First Quarter
    21 Mo  3:53am Moon Perigee: 368400 km
    21 Mo 11:48pm Winter Solstice
    22 Tu  9:00pm Ursid Shower: ZHR = 10
    23 We  9:16pm Mars-Spica: 3.5° N
    23 We  2:09pm Moon-Aldebaran: 0.7° S
    25 Fr  2:30am Moon North Dec.: 18.4° N
    25 Fr  6:11am Full Moon
    28 Mo  9:59pm Mercury Elongation: 19.7° E
    29 Tu  3:30pm Moon-Regulus: 2.9° N
    31 Th 12:55pm Moon-Jupiter: 1.6° N
    31 Th  3:19am Moon Ascending Node
Jan 01 Fr         Venus: 37.9° W

* The occultation will be visible in the US, except extreme southwestern Alaska and Hawai’i; and Canada down to Panama. In the Grand Traverse area of Michigan the occultation starts around 12:20 p.m. and ends around 1:27 p.m. This is a daytime event for most of the US.  Note that the actual time depends on your exact location.  I’ll have more information in a non Ephemeris post on Saturday the 5th.  The Occultation map is here.

** On December the 5th there will be an occultation of Mars visible across the Indian Ocean and much of Australia.  That occultation map is here.

Estimating occultation timings for your location

I used Cartes du Ciel the free software that I have a link to on the right.  Make sure that the program is set for topocentric positions under Setup/Solar System.  And you have entered your position under Setup/Observatory.  You can find your location in Google Earth, or your GPS device or smart phone.

You can also use Stellarium.  Just make sure the Moon is normal sized.

In both programs you can lock the Moon or Aldebaran in the center of the screen Pick a time in advance of the occultation and using the set time window walk the star towards the Moon, mark the time.  Then walk the star out from the Moon and record the reappearance time.  That’s it.

This should work with other planetarium programs too.

For better accuracy go to the International Occultation Timing Association (IOTA) website.  Download and install their Occult4 program for Windows computers.  Follow the instructions.  When I ran the program for my location, the location I use for Interlochen/Traverse City (Since I live approximately half-way between the two).  I got results within a half-minute of the IOTA Occult4 program results.  So the approximation method using planetarium programs is valid.

Comet C/2013 US10 (Catalina)

This comet has been hiding for the last two years after its discovery, moving into the far southern hemisphere of the sky. However this month it has emerged into our morning sky. This comet is a one time visitor from the Oort Cloud to the inner solar system and will be ejected into interstellar space. It passed perihelion on November 15th, coming just inside the Earth’s orbit on the other side of the Sun from us. It’s orbit will be headed northward and a bit toward us, so it will keep its brightness steady.

The position marks in the chart have the date and the magnitude. However the comet is currently appearing one magnitude dimmer than shown. So instead of appearing as nearly 5th magnitude, it will really be 6th magnitude. It’s definitely a binocular or telescopic object.

According to the brightness graph the comet began to under perform in brightness back in September, however, according to a new brightness formula the comet may increase in brightness by a magnitude by late February when it will be well placed for viewing all night. To monitor the brightness reports from observers go to http://www.aerith.net/comet/catalog/2013US10/2013US10.html.

Tracks of Comet Catalina and Venus in December 2015

The tracks of Comet C/2013 US10 (Catalina) for December 2015 along with part of Venus’ track. Created using Cartes du Ciel (Sky Charts).

 

12/20/2013 – Ephemeris – Winter begins tomorow

December 20, 2013 Comments off

Ephemeris for Friday, December 20th.  The sun will rise at 8:15.  It’ll be up for 8 hours and 48 minutes, setting at 5:04.   The moon, 3 days past full, will rise at 8:32 this evening.

The thermometer and snowfall tell us that winter ought to be here.  Well it will be at 12:11 p.m. (17:11 UT) tomorrow afternoon.  At that point the sun will be directly over the Tropic of Capricorn at 23 ½ degrees south latitude.  Odd name because 2,000 years ago the sun was in indeed entering Capricornus.  Now it’s entering in Sagittarius, right above the spout of the teapot asterism we know so well in summer.  From then on the sun will be climbing up the sky each noon until June 21st next year when summer will start.  To which I say Go Sun Go!  The sun will barely make it to 22 degrees above the southern horizon at local noon in Interlochen and be out for only 8 hours and 48 minutes.  If it stayed there all year we’d be in a deep freeze colder than Antarctica.

Times are for the Traverse City/Interlochen area of Michigan.  They may be different for your location.

Addendum

Winter solstice

Sun’s view of the Earth at the instant of winter solstice. Created using Celestia.

06/20/2013 – Ephemeris – Summer starts tomorrow

June 20, 2013 1 comment

Ephemeris for Thursday, June 20th.  Today the sun will be up for 15 hours and 33 minutes, setting at 9:31.   The moon, 3 days before full, will set at 4:15 tomorrow morning.  Tomorrow the sun will rise at 5:57.

Summer will arrive overnight at 1:04 a.m. tomorrow morning when the sun will reach its highest point in the northern sky.  If you were watching the sun’s shadow of a flag pole at local noon, when the sun is due south, it would be getting shorter every day since the winter solstice back on December 21st.  From tomorrow until the next winter solstice that shadow will be getting longer.  We are getting the most heat from the sun now due to the length of daylight and the high altitude of the sun most of the day. Because the earth and water takes time to heat up, we are not experiencing our greatest temperatures yet.  That will take a month or a month and a half.  That’s why solstice just starts summer and is not at the peak of it.

Times are for the Traverse City/Interlochen area of Michigan.  They may be different for your location.

Addendum

Solstice shadows

Comparison of shadows between winter and summer solstices. Note the angles are approximate.

12/20/2012 – Ephemeris – Winter starts tomorrow morning.

December 20, 2012 Comments off

Ephemeris for Thursday, December 20th.  The sun will rise at 8:15.  It’ll be up for 8 hours and 48 minutes, setting at 5:04.   The moon, at first quarter today, will set at 1:51 tomorrow morning.

Tomorrow morning at 6:12 a.m. The sun will pass through the point where is appears the farthest south.  We call it the winter solstice, or winter sun stand still.  If you are measuring the shadow of the sun cast by a stick at noon, tomorrow will be the date of the longest noon time shadow.  The ancients, who were not too sure the sun would come back partied big time as the sun stopped the southern progress and began to head back north.  This was and is a big festival time featuring lots of lights, be it candles, torches, the burning of the yule log and Christmas lights.  For those in the southern hemisphere they are celebrating the summer solstice.  In any case our winter is the shortest season.

Times are for the Traverse City/Interlochen area of Michigan.  They may be different for your location.

Addendum

Noon in Michigan at the winter solstice.

Noon in Michigan at the winter solstice. Created using Celestia.

To keep the earth large enough, I’ve had to move in to 10 earth radii, so Michigan at the top is a bit closer to the limb than it is to the sun.  The vantage point is over the Tropic of Capricorn, 23 1/2 degrees south latitude.  The short daylight hours and low sun angle hasn’t caught up to us yet.  The coldest days are expected in January.

11/30/2012 – Ephemeris – Previewing December skies

November 30, 2012 Comments off

Ephemeris for Friday, November 30th.  The sun will rise at 7:58.  It’ll be up for 9 hours and 5 minutes, setting at 5:03.   The moon, 2 days past full, will rise at 6:58 this evening.

Let’s look at the month of December which starts tomorrow.  The hours of daylight will change little except to be darker in the morning and lighter in the evenings.  In the Traverse City/Interlochen area sunset will be from 5:03 today, down to 5:02 and then advancing to 5:12 at the end of the month.  The earliest sunset will be around the 10th.  There is more movement in the sunrise times which will advance from 7:59 this morning to 8:19 on the 31st.Dec 1.    Winter will officially arrive at the winter solstice on the 21st at 6:12 a.m.  The noontime sun will dip from 23 ½ degrees to a bit less than 22 degrees above the southern horizon on that day.  Daylight hours will drop from 9 hours 3 minutes tomorrow to 8:48 on the solstice.

Times are for the Traverse City/Interlochen area of Michigan.  They may be different for your location.

12/22/11 – Ephemeris – Winter is here!

December 22, 2011 Comments off

Thursday, December 22nd.  The sun will rise at 8:16.  It’ll be up for 8 hours and 48 minutes, setting at 5:05.   The moon, 2 days before new, will rise at 7:06 tomorrow morning.

At 12:30 this morning the sun reached its farthest southerly travel and is now slowly beginning to turn northward again.  That point was the winter solstice, or to be more general the December solstice, because in the southern hemisphere of the earth summer has arrived, while we star winter.  December 21st is the usual day of the solstice, and it will be again next year because next year is the leap year and will set the calendar back to match the seasons.  The adding of the extra day every 4 years came under the auspices of Julius Caesar and gave us the Julian calendar.  It slightly over corrected the calendar.  The latest adjustment was the Gregorian reform that will fix the calendar for the next few millennia.

* Times, as always are for the Traverse City/Interlochen area of Michigan.