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01/06/2020 – Ephemeris – The Earth was closest to the Sun in its orbit yesterday

January 6, 2020 Comments off

Ephemeris for Monday, January 6th. Today the Sun will be up for 8 hours and 57 minutes, setting at 5:17, and it will rise tomorrow at 8:19. The Moon, half way from first quarter to full, will set at 5:02 tomorrow morning.

Yesterday’s perihelion, or closest point of the Earth to the Sun of roughly 91.4 million miles (147 million km) is only 1.7% closer to the Sun than average. It doesn’t do much to make our winters warmer, but it does make winter the shortest season. That’s because the Earth travels faster when near the Sun than when it’s farther away. Winter lasts only 89 ½ days. The Earth’s aphelion, when it’s farthest from the Sun will be on the 4th of July, in summer, making that the longest season at 93 ½ days. Of course being this far north it feels like winter is longer than summer, but astronomically it’s the other way around. Being a leap year, with February having 29 days, spring will arrive a calendar day early on the 19th of March.

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

Addendum

Earth's orbit

The Earth’s orbit, somewhat exaggerated, showing perihelion and the seasons. Credit “Starts with a Bang” blog by Ethan Siegel.

Seasons for 2020

The Seasons for 2020 from data in Astronomical Tables of the Sun, Moon, and Planets Third Edition by Jean Meeus. Date and times are in TD, Dynamical Time. Subtract about 1 minutes to convert to Universal Time (UT).  Also subtract 5 hours for Eastern Standard Time and 4 hours for Eastern Daylight Time.

For and explanation of the Cross-Quarter Days column, check out my Ground Hog Day post last year:  https://bobmoler.wordpress.com/2019/02/02/02-02-2019-ephemeris-extra-groundhog-day-and-other-seasonal-days/

 

12/20/2019 – Ephemeris – Winter arrives late tomorrow night

December 20, 2019 Comments off

Ephemeris for Friday, December 20th. Today the Sun will be up for 8 hours and 48 minutes, setting at 5:04, and it will rise tomorrow at 8:16. The Moon, 1 day past last quarter, will rise at 2:55 tomorrow morning.

Tomorrow will be the first day of winter, barely, since the moment of solstice will arrive at 11:19 p.m. If you’re south of the equator this is the first day of summer. The Earth reaches 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. The Sun for us is up only 8 hours, 48 minutes, 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. Spring and summer would eventually return!

The 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.

December solstice

The Earth and its axis on the first day of winter, the winter solstice. From my Sun and the Earth talk slides.

Solstice shadows

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

09/23/2019 – Ephemeris – Fall has fallen upon us

September 23, 2019 Comments off

Ephemeris for Monday, September 23rd. Today the Sun will be up for 12 hours and 7 minutes, setting at 7:38, and it will rise tomorrow at 7:32. The Moon, 2 days past last quarter, will rise at 2:01 tomorrow morning.

Fall has, well… fallen upon us and in a few weeks so will the leaves. At 3:49 (7:49 UT) this morning the Sun crossed overhead at the Earth’s equator heading south. At that same time the Sun theoretically set at the north pole and rose at the south pole. The day is called the autumnal equinox and the daylight hours today is 12 hours and 7 minutes instead of 12 hours exactly. That’s due to our atmosphere and our definition of sunrise and sunset. The reason for the cooler weather for us north of the equator now and the cold weather this winter is that the length of daylight is shortening, and the Sun rides lower in the sky, spreading its heat over a larger area, thus diluting its intensity.

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

Addendum

Sun's path through the sky on the equinox

The Sun’s path through the sky on the equinox day from Traverse City, MI. Created using my LookingUp program.

Sunrise on the autumnal equinox

That is not a pumpkin on the head of the motorcyclist. That’s the Sun rising as I’m traveling east on South Airport Road south of Traverse City Mi. on the autumnal equinox. This is the east-west section of the road. The Sun is rising over the hills some 6 miles to the east. Credit: Bob Moler.

Categories: Ephemeris Program, Equinox, Seasons Tags:

06/21/2019 – Ephemeris – Summer starts today!

June 21, 2019 Comments off

Ephemeris for Friday, June 21st. Today the Sun will be up for 15 hours and 34 minutes, setting at 9:32, and it will rise tomorrow at 5:57. The Moon, half way from full to last quarter, will rise at 12:44 tomorrow morning.

At 11:54 (15:54 UT) this morning the Sun will reach its greatest angle north of the celestial equator or 23 ½ degrees. The date and the point in the sky where the Sun is at that instant is called the summer solstice, or summer Sun standstill. It means the point at which the Sun seems poised farthest north before heading southward. This would be most noticeable if you were monitoring the height of the Sun at noon or the Sun’s rising or setting point day by day as the ancients did. Besides being the day with the longest sunlight we, in the northern hemisphere, are also receiving more intense heat from the sun than any other day of the year. Still hotter weather is in store as the northern hemisphere continues to warm up.

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

Addendum

Summer Solstice Sun's Path

The Sun’s apparent path in the sky for the summer solstice. The cyan circle is the horizon and the Sun is plotted every 15 minutes throughout the day. Created using my LookingUp program. This is a slide from his school program on the cause of the seasons.

Earth at summer solstice

Earth from the DSCOVR satellite at the June solstice 2015. Of course we’re under a cloud. Credit NOAA

03/18/2019 – Ephemeris – Spring, the full moon and Easter

March 18, 2019 Comments off

Ephemeris for Monday, March 18th. Today the Sun will be up for 12 hours and 2 minutes, setting at 7:52, and it will rise tomorrow at 7:48. The Moon, 2 days before full, will set at 7:21 tomorrow morning.

Spring is two days away. In checking my astronomical calendars I noticed an odd thing related to the date of Easter for western churches. If I said that the date of Easter was the first Sunday after the first full Moon after the vernal equinox. I’d be wrong. Even if I replaced vernal equinox with first day of spring, I would still be wrong by ecclesiastical standards. The ecclesiastical vernal equinox is March 21st, no matter what. Plus the full moon date is a tabulated value and not necessarily the astronomical full moon date. This year the astronomical first full moon of spring falls less than 4 hours after the astronomical vernal equinox on March 20th. Therefore Easter will be late this year on April 21st, 4 days earlier than its latest possible date.

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

03/05/2019 – Ephemeris – The Big Dipper rising in the east

March 5, 2019 Comments off

Ephemeris for Fat Tuesday, March 5th. Today the Sun will be up for 11 hours and 21 minutes, setting at 6:35, and it will rise tomorrow at 7:11. The Moon, 1 day before new, will rise at 7:33 tomorrow morning.

While Orion and the stars of winter are still holding forth in the south the Big Dipper is sneaking up in the northeast. Indeed at 8 p.m. the front stars of the dipper’s bowl are half way up the sky, at the same altitude of Polaris the North Star. To the Anishinaabe native peoples of this region the Big Dipper wasn’t part of a bear, it was the hind end of the Fisher, Ojiig in their language. The Fisher, a magical animal of their legends, a weasel-like animal brought warm seasons to the Earth, and serves as a weather indicator. As he climbs the sky in the east he is signaling spring and the maple sugaring season. The Big Dipper is also a pointer to some of the important stars and constellations of spring.

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

Addendum

Ojiig rising

The Big Dipper, as Ojiig the Fisher of the Anishinaabe people rising higher in the northeast at 8 p.m. March 5, 2019. Created using Stellarium.

The Anishinaabe constellation drawing of the Fisher is from Ojibwe Sky Star Map Constellation Guide by Annette S. Lee, William Wilson, Jeffrey Tibbets and Carl Gawboy available locally and online. They are part of the latest editions of Stellarium, a free planetarium program. Links to it are on the right. Other information and links are available within the Sky Lore tab.

My story of the Fisher is here: https://bobmoler.wordpress.com/2012/10/11/the-story-of-the-fisher-star/

02/02/2019 – Ephemeris Extra – Groundhog Day and other seasonal days

February 2, 2019 Comments off

Note:  I wrote this article as part of the Grand Traverse Astronomical Society’s Stellar Sentinel for February 2019.

Groundhog day coming this month got me to thinking about the seasons and those special seasonal days, like solstices, equinoxes and cross-quarter days. February 2nd is a cross-quarter day, supposedly when winter is half over. Below is a table I created of the seasons for one year starting with last December’s winter solstice.

I took the date and times from Astronomical Tables of the Sun, Moon and Planets, Third edition by Jean Meeus. TD is Dynamical Time, used to calculate the positions of bodies in the solar system, is about 68 seconds fast compared to Universal Time (UT), which is tied to the Earth’s rotation. The difference is slowly changing at less than a second a year and doesn’t enter into the calculations. The Julian Date is a consecutive date starting on January 1, 4713 BC at noon UT. It’s used by astronomers to calculate date differences. like the length column in the table above without worrying how many days months have or how many leap years are in the interval. If you want to convert a calendar date to a Julian date or a Julian date to calendar date go to the Naval Observatory web page here: https://aa.usno.navy.mil/data/docs/JulianDate.php.

Note that the seasons are of different lengths. This is because the Earth’s orbit is slightly elliptical. It reached perihelion, its closest to the Sun, this year on January 3rd, and it will reach aphelion, its farthest, on July 4th. The Earth or any planet moves fastest when near perihelion. And with perihelion 14 days into winter, makes winter the shortest season. Autumn is the second shortest season 90 days compared to winter’s 89 days. Summer at nearly 94 day’s length is 4.7 days longer than winter. However we’re too far north to really notice it. Spring is second with nearly a 93 day length.

The rest of this article is based quite a bit on the web page: Common Holidays in Relation to Equinoxes, Solstices & Cross-Quarter Days – https://www.naic.edu/~gibson/cal/. It’s a cool list. Naic.edu is the website of the Arecibo Observatory in Puerto Rico. Apparently it was someone’s (Gibson’s) personal post.

The equinoxes and solstices are quarter days, for the four seasonal quarters of the year. The table above has Mid-Season and Date for the half way point in the season. The Cross-Quarter Days column are the dates which are more or less celebrated down throughout history.

The first celebrated cross-quarter day is February 2nd, Groundhog Day Which the famous weather prognosticating rodent in Punxsutawney, PA forecasts the length of winter based on if he sees his shadow. Supposedly, if he sees his shadow winter will last for six more weeks, if he doesn’t then spring is just around the corner. Actually from February second to the vernal equinox is six and a half weeks. If we had a winter like last year with a snowy April, winter lasted until the second cross-quarter day. The actual first cross-quarter day this year is February 4th. February 2nd, 40 days after Christmas, is also celebrated as Candlemas Day, when candles are blessed for the year, and the Feasts of the Purification of the Virgin Mary and The Presentation of the Child Jesus by the Catholic and some other Christian Churches.

The first quarter day is the vernal equinox, which occurs in our time zone on March 20th. The Ides of March, the 15th is pretty close to the vernal equinox and was the start of the year for a time with the Romans. It was the date in 44 BC that Julius Caesar was assassinated. March, named after the god Mars was also for a long time the first month of the year. They, for a time had 10 months, and consigned the winter months to ?. Later they added two months in front of March, which is why our 9th through 12th months are named September (7), October (8), November (9) and December (10).

The second cross-quarter day to be celebrated is May 1st, May Day. The actual 2nd cross-quarter day this year is May 6th.

The second quarter day, the summer solstice is on June 21st. It’s near midsummer day, the 24th, the feast of St. John the Baptist. It’s a big deal in Europe. If you had a midsummer’s night dream it would be on the night of June 23-24. Of course if that date was really midsummer, summer would have to start in early May.

The third cross-quarter day is August 1st, Lughnasadh. This is Celtic. It was the wedding day of Lugh, their sun god with the goddess of the Earth. This causes the crops to ripen in time to harvest in the fall. The actual date this year is August 7th.

The third quarter day is the autumnal equinox. This year it’s on September 23rd.

The fourth cross-quarter day is celebrated on October 31st, Halloween. It is the day before All Saints Day, and Day of the Dead in Mexico. The actual cross-quarter day this year is November 7th.

The fourth quarter day is the winter solstice, December 21st. This is in the midst of festivals ancient and modern around the time the Sun starts heading north again. Festivals of light, like Saturnalia, Yule, Christmas, and Hanukkah

There you have the days of our seasons.

Categories: Ephemeris Extra, Seasons