This diagram shows the Aphelions (green points) and Perihelions (orange points) for our Solar System's inner planets. Seen here from the Northern Ecliptic Pole, the planets move couter-clockwise. The blue portion of the orbits are north of the Ecliptic Plane; the pink portion of the orbits are south of the Ecliptic Plane. (Image Sources: Wikipedia.org, By / Original: User:Danial79 / Vectorization: Mrmw - Own work based on: Inner Planet Orbits.jpg:, CC0, https://commons.wikimedia.org/w/index.php?curid=92300694)
By Glenn A. Walsh
Reporting for SpaceWatchtower
The week of American Independence Day is often one of the hottest weeks of the year, with many people taking the holiday as an opportunity for a vacation. However, it is not hot because of a close distance between the Earth and the Sun.
Although the Summer months in the Northern Hemisphere are known for the year's warmest weather, the Earth is actually at the point in its orbit farthest from the Sun (astronomically known as the point of Aphelion) around July 5. This Thursday afternoon, just two days after American Independence Day on July 4 and a couple weeks after the Summer Solstice on June 21, will mark Aphelion for 2023, the location in Earth's annual orbit around the Sun where our planet is farthest from the Sun for the entire year!
This year, Earth Aphelion will occur on Thursday Afternoon, 2023 July 6 at 4:06 p.m. Eastern Daylight Saving Time (EDT) / 20:06 Coordinated Universal Time [UTC – International time used by scientists; previously referred to as Greenwich Mean Time (GMT) or Greenwich Civil Time (GCT)]. At that moment, Earth will be the farthest from the Sun for the whole year: 94,506,364.705 statute miles / 152,093,251 kilometers.
For A.D. 2023, the season of Summer began at Earth's Northern Hemisphere's Summer Solstice (and the season of Winter began at the Southern Hemisphere's Winter Solstice) at the moment of the June Solstice: Wednesday Morning, 2023 June 21 at 10:58 a.m. EDT / 14:58 UTC. Summer will continue until the Autumnal Equinox when Autumn / Fall commences in the Northern Hemisphere (and Spring begins in the Southern Hemisphere) on Saturday Morning, 2023 September 23 at 2:50 a.m. EDT / 6:50 UTC.
The Earth's closest approach to the Sun (Perihelion) each year is around January 2, shortly after the Winter Solstice on or near December 21. Approximately a half-year's time between Earth Perihelion and Earth Aphelion, the difference in distance between the Sun and Earth varies by about 3.2 million statute miles / 5.1499008 million kilometers.
This year, Earth Perihelion occurred on 2023 January 4 at 11:17 a.m. Eastern Standard Time (EST) / 16:17 UTC. At that time, the Earth was 91,403,034 statute miles / 147,098,924 kilometers from the Sun. Earth Perihelion next year will occur on 2024 January 2 at 7:38 p.m. EST / January 3 at 0:38 UTC; distance from Earth to Sun: 91,404, 095 statute miles / 147,100,631.8 kilometers.
In general, the distance from the Earth to the Sun is not the major factor determining the heat of Summer or the cold of Winter. This is true, despite the fact that Earth receives about 7 per-cent more solar radiation from the Sun during the time of Earth Perihelion in January, than at the time of Earth Aphelion in July.
Solar radiation, and hence the heat from the Sun, depends on the length of daylight and the angle of the Sun above the horizon. The tilt of the planet's axis, about 23.44 degrees toward the Sun, determines the additional and more direct solar radiation received by a planet's Northern or Southern Hemisphere, and hence, the warmer season of the respective hemisphere.
While the Sun does have motions (the Sun rotates on its own axis about once every 27 Earth days; our Solar System revolves around the center of the Milky Way Galaxy once every 225 million-to-250 million Earth years), it is actually the motion of the Earth tilted on its axis, away from the plane of the ecliptic (Earth's orbital plane around the Sun), while revolving around the Sun, that causes the Earth's seasons.
The Earth's Perihelion in January, and Aphelion in July, are due to the elliptical nature of the Earth's orbit around the Sun. Perihelion and Aphelion would not occur if the Earth's orbit was a true circle.
The dates of Earth Perihelion and Earth Aphelion are not fixed. Due to the Earth's Precession of the Equinoxes, these days shift forward approximately one day every 58 years. About 800 years ago, the Earth Perihelion was on the date of the Winter Solstice, around December 21; Earth Perihelion will be on the Vernal Equinox, the beginning of Spring around March 20, about 4,300 years from now. Earth's Axial Precession (often described as a "wobble" in the Earth's orientation, like a spinning top or a gyroscope) gradually changes the orientation of the Earth's Rotational Axis, which completes one rotational cycle once every 25,772 years.
Because Earth is farther from the Sun during our Spring and Summer seasons, people in Earth's Northern Hemisphere actually benefit from a few extra days of warmth (on average), than the number of days in the Autumn and Winter seasons of the year. When Earth is closer to the Sun, the Earth travels faster in its elliptical orbit around the Sun (during the Autumn and Winter months); and, when Earth is farther than average from the Sun (during the Spring and Summer seasons) the Earth travels a little more slowly --- again, this refers to the Northern Hemisphere. Hence, the Spring and Summer seasons, in the Northern Hemisphere, have a few more days than the Autumn and Winter seasons.
In fact, Jay Pasachoff, Field Memorial Professor of Astronomy at Williams College in Williamstown, Massachusetts and author of widely-used, college astronomy text-books, has precisely calculated the duration of each season, in the Northern Hemisphere:
Summer: 93 days, 15 hours
Spring: 92 days, 19 hours
Autumn / Fall: 89 days, 20 hours
Winter: 89 days, 0 hours
No matter whether in the Northern Hemisphere or the Southern Hemisphere, the days of Summer always have the most hours and minutes of daylight (the length of time between Sunrise and Sunset) each year, while the days of Winter always have the least number of hours and minutes of daylight for the year. The exact number of hours and minutes of daylight, for a particular location, depends on the locale's geographic Latitude on the Earth. Astronomers, amateur ("ham") radio operators, and long-distance radio enthusiasts (“radio DXers”), all of whom mostly depend on non-daylight hours to ply their craft, often prefer the days of Winter.
Interestingly, the climate of a locale in the Southern Hemisphere is, on average, slightly milder than a location at the same latitude in the Northern Hemisphere, because the Southern Hemisphere has significantly more ocean water and much less land. Water warms-up and cools-down more slowly than does land. The only exception is the Antarctic Continent, which is colder than the Northern Hemisphere's Arctic region, possibly because most of the Arctic region is covered with water (although, often frozen water on the surface, but liquid water beneath the ice) while Antarctica is mostly a land mass.
When considering the tides of Earth's oceans, High Tides and Low Tides are affected by both the gravity of the Sun and the gravity of the Moon. This is particularly true at or near the times of the Full Moon and New Moon primary Moon phases, when the gravitational pull of the Sun and the Moon are combined. However, being much closer to the Earth, the Moon's gravitation is much more influential than that of the Sun.
This is even more true this month, since the Sun is farthest from the Earth on July 6. Also, this month's Full Moon occurs on July 3 at 7:39 a.m. EDT / 11:39 UTC, and the Moon is closest to the Earth (Lunar Perigee) for the month on July 4 at 6:00 p.m. EDT / 22:00 UTC at a distance of 223,786.2 statute miles / 360,149 kilometers. Due to the closeness of this Full Moon (known as the Buck Moon, Hay Moon, Thunder Moon, and because July is the month astronauts first set foot on the Moon some refer to it as the Apollo Moon) to the Earth this month, some people refer to this Full Moon as a so-called "Super-Moon", the first of four consecutive "Super-Moons" in 2023. So, during the first week of July, the Moon will appear a little brighter, and the ocean tides will be a little stronger than normal.
The bright Star Spica (Alpha Virginis) is now visible in the morning sky (weather-permitting). The brightest star in the Constellation Virgo the Virgin and the 16th brightest star in Earth's night sky (Apparent Visual Magnitude: + 0.97), Spica may have helped develop one of civilization's early calendars. A calendar of ancient Armenia used the year's first sighting of Spica in the dawn sky, a few days before the Summer Solstice, to mark the beginning of the New Year for this particular calendar. The development of this calendar somewhat coincided with the beginning of agriculture in Armenia.
Interestingly, Spica is about 247 Light-Years away from Earth , which means that the light we see coming from Spica began its trip from the star 247 years ago. And, 247 years ago was when Amerca's Declaration of Independence was ratified by the Second Continental Congress in 1776!
Like clock-work, a well-known asterism (pattern of stars in the sky, not officially recognized as a constellation) of three stars shaped as a triangle is visible nearly overhead around local midnight during the Summer months (weather-permitting). And logically, as Star Trek's Mr. Spock might say, this asterism is known as the Summer Triangle!
Three of the brightest stars in the Summer sky constitute the Summer Triangle ---
Vega (Alpha Lyrae - brightest star in the Constellation Lyra the Harp); brightest of the three stars and closest to the zenith (highest point in the sky);
Altair (Alpha Aquilae - denotes the eagle eye and brightest star in the Constellation Aquila the Eagle); second brightest star of the trio;
Deneb (Alpha Cygni - denotes the tail star, is the brightest star in the Constellation Cygnus the Swan, and is the “head” star of the asterism known as the Northern Cross).
The term Summer Triangle was popularized in the 1950s by American author H.A. Rey and British astronomer Patrick Moore, although constellation guidebooks mention this triangle of stars as far back as 1913. And, during World War II, military navigators referred to this asterism as the “Navigator's Triangle.”
Regardless of city light pollution, the three bright stars of the Summer Triangle should be visible to nearly everyone in Earth's Northern Hemisphere (weather-permitting). So, just look overhead late-evening or early-morning throughout the Summer for these annual visitors to our Summer sky!
Internet Links to Additional Information ---
Apehilion & Perihelion:
Link 1 >>> https://www.timeanddate.com/astronomy/perihelion-aphelion-solstice.html
Link 2 >>> https://en.wikipedia.org/wiki/Apsis#Perihelion_and_aphelion
Axial Tilt: >>> https://en.wikipedia.org/wiki/Axial_tilt
Related Blog-Posts ---
"Summer Begins Mid-Day Wednesday at Solstice." Mon., 2023 June 19.
"Winter Begins at Solstice Wed.; Ursid Meteors Peak Thur." Mon., 2022 Dec. 19.
Source: Glenn A. Walsh Reporting for SpaceWatchtower, a project of Friends of the Zeiss
Monday, 2023 July 3.
Like This Post? Please Share!
More Astronomy & Science News - SpaceWatchtower Twitter Feed:
Link >>> https://twitter.com/spacewatchtower
Astronomy & Science Links: Link >>> http://buhlplanetarium.tripod.com/#sciencelinks
Want to receive SpaceWatchtower blog posts in your in-box ?
Send request to < spacewatchtower@planetarium.cc >.
gaw
Glenn A. Walsh, Informal Science Educator & Communicator (For more than 50 years! - Since Monday Morning, 1972 June 12):
Link >>> http://buhlplanetarium2.tripod.com/weblog/spacewatchtower/gaw/
Electronic Mail: < gawalsh@planetarium.cc >
Project Director, Friends of the Zeiss: Link >>> http://buhlplanetarium.tripod.com/fotz/
SpaceWatchtower Editor / Author: Link >>> http://spacewatchtower.blogspot.com/
Formerly Astronomical Observatory Coordinator & Planetarium Lecturer, original Buhl Planetarium & Institute of Popular Science (a.k.a. Buhl Science Center), America's fifth major planetarium and Pittsburgh's science & technology museum from 1939 to 1991.
Formerly Trustee, Andrew Carnegie Free Library and Music Hall, Pittsburgh suburb of Carnegie, Pennsylvania, the fourth of only five libraries where both construction and endowment funded by famous industrialist & philanthropist Andrew Carnegie.
Author of History Web Sites on the Internet --
* Buhl Planetarium, Pittsburgh: Link >>> http://www.planetarium.cc Buhl Observatory: Link >>> http://spacewatchtower.blogspot.com/2016/11/75th-anniversary-americas-5th-public.html
* Adler Planetarium, Chicago: Link >>> http://adlerplanetarium.tripod.com
* Astronomer, Educator, Optician John A. Brashear: Link >>> http://johnbrashear.tripod.com
* Andrew Carnegie & Carnegie Libraries: Link >>> http://www.andrewcarnegie.cc
* Other Walsh-Authored Blog & Web-Sites: Link >>> https://buhlplanetarium.tripod.com/gawweb.html
This is very informative article. I am glad that you have added some of the necessary information here. I will share this article with my friends. Now its time to avail Kabou taxi cab services in Southfield Mi for more information.
ReplyDelete