Archive

Archive for the ‘Seasons’ Category

03/20/2020 – Ephemeris – The first full day of spring

March 20, 2020 Comments off

Ephemeris for Friday, March 20th. Today the Sun will be up for 12 hours and 11 minutes, setting at 7:55, and it will rise tomorrow at 7:43. The Moon, half way from last quarter to new, will rise at 7:00 tomorrow morning.

Spring snuck up on us at 11:50 p.m. last night, so this is the first full day of spring. That point in time and the point in the sky where the Sun crossed the celestial equator the imaginary line in the sky above the Earth’s equator heading northward is called the vernal equinox. Vernal means spring and equinox means equal night, meaning that day and night are equal. Since western civilization has spread south of the equator where seasons are reversed, our northern hemisphere spring equinox is the southern hemisphere’s autumnal equinox, so to be fair to both hemispheres we generally say March or September equinox instead. However the point in the sky the Sun crossed last night will always be known as the vernal equinox.

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

Addendum

Sun at the vernal equinox

The Sun at the vernal equinox point on the celestial sphere at 11;50 p.m. EDT last night (March 19, 2020). The diagonal yellow line in the ecliptic, the Sun’s path in the sky. The vertical lines marked in hours at the top are lines of right ascension, the analog of earthly longitude. The horizontal lines are lines of declination, the same as latitude on the Earth. I referenced this point in yesterday’s program. Created using Cartes du Ciel *Sky Charts).

Sun's path through the sky on the equinox

The Sun’s path through the sky on the equinox day from Traverse City, MI. Note that the Sun rises due east and sets due west. Created using my LookingUp program.

03/16/2020 – Ephemeris – The Fisher signals maple sugaring season

March 16, 2020 Comments off

Ephemeris for Monday, March 16th. Today the Sun will be up for 11 hours and 58 minutes, setting at 7:50, and it will rise tomorrow at 7:50. The Moon, at last quarter today, will rise at 4:21 tomorrow morning.

As the weather warms up with days above freezing and nights below freezing its time to tap maple trees for their sweet sap. The Anishinaabe native people of this area had a legend that a magical animal called the Fisher, who brought summer to the Earth, signals this season by rising high in the northeast. The Fisher or Ojiig is seen in the stars where the official constellation of Ursa Major, the great bear and the popular asterism the Big Dipper is. The Fisher’s claim to immortality is that he and some of his animal friends were able to break through the dome of the sky to release the warm air from above to heat the Earth. For his trouble he was killed, but the Great Spirit placed him in the sky where we see him today.

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

Addendum

The Fisher rising

Finding the Big Dipper and the Fisher around 9 p.m. Click on the image to enlarge. Created using Stellarium and GIMP.

 

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.