2016 June Solstice Signals Summer Start But Also Begins Summer End

Summary: The 2016 June solstice, at 22:34 Coordinated Universal Time, Monday, June 20, signals summer start but also begins summer end.

graphic of Earth’s orbit, with orbital tilts toward and away from sun as solstice signals: Thomas G. Andrews/NOAA Paleoclimatology Program, Public Domain, via NOAA Paleoclimatology

The 2016 June solstice, which takes place at 22:34 Coordinated Universal Time (6:34 p.m. Eastern Daylight Time), Monday, June 20, signals summer start but also begins summer end in the Northern Hemisphere.

The June solstice is known as the Northern solstice and also as the Northern Hemisphere’s summer solstice. The June solstice opens the Northern Hemisphere’s astronomical summer. The Northern Hemisphere’s greatest number of hours of sunlight occurs on the June solstice.

With opposite seasons south of the equator, the Southern Hemisphere now experiences winter and knows the June solstice as the southern winter solstice. The June solstice opens the Southern Hemisphere’s astronomical summer. The Southern Hemisphere’s greatest number of hours of darkness occurs on the June solstice.

At the June solstice, the subsolar point, at which the sun appears directly overhead, is on the Tropic of Cancer. At 23.43711 degrees north latitude, the Tropic of Cancer marks the most northerly latitude for an overhead sun.

The tilt of the Earth’s rotational axis in June accounts for the placement of the subsolar point on the Tropic of Cancer. Earth’s rotational axis is tilted at 23.43711 degrees to its perpendicular orbital axis. Earth’s tilted axis leans away from or toward the sun. In June, the North Pole’s end of the imaginary axis tilts toward the sun and receives sunlight perpendicular to the Earth’s surface at the Tropic of Cancer.

At the time of the June solstice, the sun reaches its most northerly point in Earth’s skies. The June solstice marks the sun’s northernmost rising in the east and setting in the west.

After marking its northernmost overhead-point over Earth on the June solstice, the sun then begins its apparent movement toward its southernmost overhead-point. The reversal of direction signals the Earth’s nearness to aphelion, the farthest center-to-center distance between Earth and sun. On Monday, July 4, 2016, two weeks after the 2016 June solstice, Earth reaches 2016’s aphelion (Ancient Greek: ἀπό, apó, “from” + ἥλιος, hḗlios, “sun”).

Astronomers express center-to-center distances between Earth and sun in astronomical units (AU). Set by the International Astronomical Union (IAU) in 2012, an AU equals 149,597,870,700 meters, which equates to 149,597870.70 kilometers. Time And Date website’s conversion of AU to miles places 2016’s aphelion at a center-to-center distance of 94,512,904 miles.

The December solstice marks the sun’s most southerly position in Earth’s skies. The December solstice marks the sun’s southernmost rising in the east and setting in the west.

At the December solstice, the South Pole’s end of the imaginary rotational axis leans toward the sun. Now the subsolar point is on the Tropic of Capricorn. As the Tropic of Cancer’s Southern Hemisphere counterpart, the Tropic of Capricorn lies at 23.43711 degrees south latitude.

On Wednesday, Jan. 4, 2017, at 14:18 UTC (9:18 a.m. Eastern Standard Time), two weeks after the December solstice, Earth reaches the opposite orbital extreme of perihelion, or closest center-to-center distance between Earth and sun. Reaching perihelion then marks the continuation of Earth’s orbital journey toward the reverse, or opposite, extreme of aphelion.

Dates of occurrence for the June solstice range from June 20 to June 22. In the 21st century, June 21 is the commonest date of occurrence. June 21 claims 54 solstices, according to Coordinated Universal Time as the world’s official time standard. June 20 welcomes 46 solstices. Time And Date website notes that June 22 last coincided with a solstice in 1975. The next June 22 solstice occurs in 2203.

The takeaway for the 2016 June solstice as signal of summer start and of summer end in the Northern Hemisphere is that the northern summer’s end is in its beginning. Upon reaching maximum tilt toward the sun with the June solstice, the Northern Hemisphere begins losing hours of sunlight as Earth’s orbit journeys toward the opposite solstice in December.

As Hamm says in Samuel Beckett’s one-act absurdist play, Endgame: “The end is in the beginning and yet you go on.”

June 21, 2010 solstice as imaged by Spinning Enhanced Visible and Infrared Imager (SEVIRI) on EUMETSAT’s Meteosat-9: EUMETSAT, Public Domain, via NASA Earth Observatory

Acknowledgment

My special thanks to talented artists and photographers/concerned organizations who make their fine images available on the internet.

Image credits:

graphic of Earth’s orbit, with orbital tilts toward and away from sun as solstice signals: Thomas G. Andrews/NOAA Paleoclimatology Program, Public Domain, via NOAA Paleoclimatology @ http://www.ncdc.noaa.gov/paleo/slides/slideset/11/11_183_slide.html

June 21, 2010 solstice as imaged by Spinning Enhanced Visible and Infrared Imager (SEVIRI) on EUMETSAT’s Meteosat-9: EUMETSAT, Public Domain, via NASA Earth Observatory @ http://earthobservatory.nasa.gov/IOTD/view.php?id=52248

For further information:

“11 Things About the June Solstice.” Time And Date > Sun & Moon.
Available @ https://www.timeanddate.com/astronomy/facts-about-june-solstice.html

Byrd, Deborah. “Earth Farthest From Sun on July 4.” EarthSky > Tonight. July 4, 2016.
Available @ http://earthsky.org/tonight/earth-farthest-from-sun-for-year-in-early-july

Byrd, Deborah. “Things to Notice at the June Solstice.” EarthSky > Tonight. June 20, 2016.
Available @ http://earthsky.org/tonight/solstice-brings-northernmost-sunset

Dickinson, David. “Earth at Aphelion 2016.” Universe Today. July 4, 2016.
Available @ http://www.universetoday.com/129513/earth-at-aphelion/#

Erickson, Kristen. “What Causes the Seasons?” EarthSky > Astronomy Essentials > Science Wire > Space. May 3, 2016.
Available @ http://spaceplace.nasa.gov/seasons/en/

Espenak, Fred. “Earth at Perihelion and Aphelion: 2001 to 2100 Greenwich Mean Time.” Astro Pixels > Ephemeris.
Available @ http://www.astropixels.com/ephemeris/perap2001.html

Espenak, Fred. “Solstices and Equinoxes: 2001 to 2100 Greenwich Mean Time.” Astro Pixels > Ephemeris.
Available @ http://www.astropixels.com/ephemeris/soleq2001.html

“June Solstice: Longest and Shortest Day of the Year.” Time And Date > Sun & Moon.
Available @ https://www.timeanddate.com/calendar/june-solstice.html

Kaler, James B. (Jim). “Measuring the Sky: A Quick Guide to the Celestial Sphere.” University of Illinois Astronomy > Skylights.
Available @ http://stars.astro.illinois.edu/celsph.html

King, Bob. “Solstice Brings Late Nights, Bright Sights.” Sky & Telescope > Observing. June 15, 2016.
Available @ http://www.skyandtelescope.com/observing/june-solstice-means-late-nights-bright-lights/

MacRobert, Alan. “This Week’s Sky at a Glance, June 17 - 25.” Sky & Telescope > Observing > Sky at a Glance. Friday, June 17, 2016.
Available @ http://www.skyandtelescope.com/observing/sky-at-a-glance/this-weeks-sky-at-a-glance-june-17-25/

Marriner, Derdriu. “Two Weeks After 2016 December Solstice Earth Reaches 2017 Perihelion.” Earth and Space News. Wednesday, Dec. 28, 2016.
Available @ https://earth-and-space-news.blogspot.com/2016/12/two-weeks-after-2016-december-solstice.html

McClure, Bruce. “Earliest Sunrises Before Summer Solstice.” EarthSky > Tonight. June 12, 2016.
Available @ http://earthsky.org/tonight/earliest-sunrises-before-june-solstice-jupiter-venus

McClure, Bruce. “Latest Dusk for Northerly Latitudes.” EarthSky > Tonight. June 24, 2016.
Available @ http://earthsky.org/tonight/latest-dusk-at-40-degrees-n-latitude

McClure, Bruce. “Slowest Sunsets Around Solstices.” EarthSky > Tonight. June 21, 2016.
Available @ http://earthsky.org/tonight/longest-sunsets-around-solstices

McClure, Bruce. “Solstice Eve Moon Still Near Saturn.” EarthSky > Tonight. June 19, 2016.
Available @ http://earthsky.org/tonight/solstice-full-moon-on-june-20

Meeus, Jean. Astronomical Algorithms. Second edition. Richmond VA: Willmann-Bell, Inc., 2005.

“Perihelion, Aphelion and the Solstices.” Time And Date > Sun & Moon.
Available @ http://www.timeanddate.com/astronomy/perihelion-aphelion-solstice.html

Rosenberg, Matt. “GMT vs. UTC.” About.com > About Education > Geography > Physical Geography > Time and Time Zones.
Available @ http://geography.about.com/od/timeandtimezones/a/gmtutc.htm

“Seasons: Meteorological and Astronomical.” Time And Date > Calendar.
Available @ http://www.timeanddate.com/calendar/aboutseasons.html

“Seeing Equinoxes and Solstices From Space.” NASA Earth Observatory > Image of the Day. Sept. 23, 2011.
Available @ http://earthobservatory.nasa.gov/IOTD/view.php?id=52248