Two Weeks After 2016 December Solstice Earth Reaches 2017 Perihelion

Summary: On Wednesday, Jan. 4, 2017, two weeks after the 2016 December solstice, Earth reaches 2017 perihelion, Earth’s closest orbital point from the sun.

In the 21st century, Earth reaches annual perihelion, or maximum closeness, around Jan. 2 to 5; New Year Cartoons/Astronomy Humor by Sara Zimmerman, cartoonist and creator of webcomics Unearthed Comics: Unearthed Comics @Unearthed Comics, via Facebook Jan. 2, 2015

At 14:18 Coordinated Universal Time (9:18 a.m. Eastern Standard Time), Wednesday, Jan. 4, 2017, two weeks after the 2016 December solstice, Earth reaches 2017 perihelion, the closest center-to-center orbital point with the sun.

The 2016 December solstice took place Wednesday, Dec. 21, at 10:44 UTC (5:44 a.m. EST). The December solstice marks Earth’s axial tilt, at the North Pole, away from the sun and astronomically opens northern winter and southern summer.

In the table of 21st century perihelion and aphelion calculations on his Astro Pixels website, retired NASA astrophysicist Fred Espenak lists Earth’s 2017 perihelic distance at 0.9833094 AU (147,100,993 kilometers). Stavanger, southwestern Norway-based website Time And Date’s conversion of AU to miles gives a 2017 perihelic distance of 91,404,322 miles.

Astronomers calculate distances between Earth and sun in astronomical units (AU). An astronomical unit represents the mean distance between Earth and sun. In 2012, the International Astronomical Union set the value of 1 AU at 149,597,870,700 meters (149,597,870.70 kilometers; roughly 92,955,807 miles).

Earth’s orbit does not trace a perfect circle, in which all points are equidistant from the sun in the center. Eccentricity, or deviation, in Earth’s orbit around the sun drive variations in annual points of closest distance, or perihelion, and farthest distance, or aphelion. Perihelic distances vary annually. The moon exerts an important influence on Earth’s orbit around the sun.

An eccentricity of zero denotes a perfectly circular orbit. Numbers higher than zero indicate somewhat elliptical orbits. Espenak gives a mean eccentricity of 0.0167 for Earth’s orbit.

Espenak gives a mean perihelic value of 0.9832899 AU (147,098,074 kilometers) for annual variations in Earth’s closest center-to-center distances from the sun. January 2017’s perihelion exceeds the mean perihelic value by 2,919 kilometers.

January 2017’s perihelion bests the previous year’s closeness by 822 kilometers. On Jan. 2, 2016, perihelion logged 0.9833039 AU (147,100,171 kilometers) at 22:49 UTC (5:49 p.m. EST). Time And Date’s conversion expresses 2016 perihelion as 91,403,812 miles. January 2016’s perihelion exceeded the mean perihelic value of 0.9832899 AU (147,098,074 kilometers) by 2,097 kilometers.

January 2017’s perihelion also will best 2018’s perihelion by 3,764 kilometers. On Wednesday, Jan. 3, 2018, perihelion at 05:35 UTC (12:35 a.m. EST) measures 0.9832843 AU (147,097,229 kilometers). Time And Date converts 2018 perihelion to 91,401,983 miles. January 2018’s perihelion is 845 kilometers less than the mean perihelic value of 0.9832899 AU (147,098,074 kilometers).

The 21st century’s first perihelion happened Jan. 4, 2001, at 8:52 UTC (3:52 a.m. EST). The distance of 0.9832860 AU (roughly 147,097,492 kilometers) was 582 kilometers less than the mean perihelic value of 0.9832899 AU (147,098,074 kilometers).

The 21st century’s last perihelion is timed for 13:54 UTC (8:54 a.m. EST), Jan. 3, 2100. The distance of 0.9833398 AU (roughly 147,105,534 kilometers) will exceed the mean perihelic value of 0.9832899 AU (147,098,074 kilometers) by 7,460 kilometers.

Fred Espenak identifies the extremes in perihelion for the 21st century. Minimum and maximum perihelions will be separated by 78 years. The range between the minimum and maximum extremes will be 0.0001431 AU (21,403 kilometers).

Minimum perihelion of 0.9832436 AU (roughly 147,091,139 kilometers) will occur Jan. 5, 2020, at 7:48 UTC (2:48 a.m. EST). January 2020’s perihelion will be 6,935 kilometers less than the mean perihelic value of 0.9832899 AU (147,098,074 kilometers).

Maximum perihelion of 0.9833866 AU (roughly 147,112,542 kilometers) will occur Jan. 5, 2098, at 02:34 UTC (Saturday, Jan. 4, 9:34 p.m. EST). January 2098’s perihelion will exceed the mean perihelic value of 0.9832899 AU (147,098,074 kilometers) by 14,468 kilometers.

The takeaway for Earth’s reach of 2017 perihelion two weeks after the 2016 December solstice is that Earth’s eccentric orbit produces annual extremes of maximum closeness to and remoteness from the sun.

seasonal variations; solstices signal maximum polar tipping away from or toward the sun: NASA, Public Domain, via NASA Solar System Exploration

Acknowledgment

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

Image credits:

In the 21st century, Earth reaches annual perihelion, or maximum closeness, around Jan. 2 to 5; New Year Cartoons/Astronomy Humor by Sara Zimmerman, cartoonist and creator of webcomics Unearthed Comics: Unearthed Comics @Unearthed Comics, via Facebook Jan. 2, 2015, @ https://www.facebook.com/UnearthedComics/photos/a.434869023243345/825025070894403/

Earth’s remoteness (aphelion) and proximity (perihelion) in orbiting the sun: Alexander Novati, Public Domain, via NASA Jet Propulsion Laboratory SciJinks @ http://scijinks.jpl.nasa.gov/solstice/

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