2018 Planetary Motions

2018 PLANETARY MOTIONS (all dates formulated with UTC time)

MERCURY: (highest point 27 degrees) (88 day orbit)

January 01: Greatest Western Elongation (22d W) (Seen in the EAST as a Morning star)

January 25: Aphelion (0.467 AU)

February 17: Superior Conjunction (Opposite the Sun from Earth & beginning apparition)

March 10: Perihelion (0.30 AU)

March 15: Greatest Eastern Elongation (18d E) (Seen in the WEST as an Evening star)

March 22: Stationary

April 01: Inferior Conjunction

April 14: Stationary

April 23: Aphelion (0.467 AU)

April 29: Greatest Western Elongation (27d W)

June 06: Superior Conjunction

June 06: Perihelion (0.30 AU)

July 12: Greatest Eastern Elongation (26d E)

July 20: Aphelion (0.467 AU)

July 25: Stationary

August 09: Inferior Conjunction

August 18: Stationary

August 26: Greatest Western Elongation (18d W)

September 02: Perihelion (0.30 AU)

September 21: Superior Conjunction

October 16: Aphelion (0.467 AU)

November 06: Greatest Eastern Elongation (23d E)

November 17: Stationary

November 27: Inferior Conjunction

November 29: Perihelion (0.30 AU)

December 06: Stationary

December 15: Greatest Western Elongation (21d W)






VENUS: (highest point 47 degrees) (225 day orbit)

January 09: Superior Conjunction

January 23: Aphelion (0.728 AU)

May 15: Perihelion (0.718 AU)

August 17: Greatest Eastern Elongation (45 deg. W)

September 5: Aphelion (0.728 AU)

September 21: Greatest Brilliancy (apparent magnitude -4.6)

October 05: Stationary

October 26: Inferior Conjunction

November 14: Stationary

December 02: Greatest Brilliancy (apparent magnitude -4.7)

December 26: Perihelion (0.718 AU)






EARTH: (Random Data): (365 day orbit)

January 1: Closest Perigee (356,565 km)

January 03: Perihelion: Closest that the Earth gets to the Sun in its orbit (0.98 AU)

January 15: Furthest Apogee (406,459 km)

March 11: Spring Forward; Standard Time (ST) becomes Daylight Time (DT) (Daylight Savings begins on Sunday at 02:00)

March 20: Vernal (spring) Equinox (equal day/night)

March 20: Astronomical spring begins (Mar 20- June 20)

April 8: Closest Apogee (404,144 km)

June 20: Astronomical summer begins (June 20- Sept 21)

June 21: Summer Solstice; longest day & highest “Solar Noon” (Northern Hemisphere).

July 06: Aphelion: Earth’s furthest point from the Sun in its orbit (1.017 AU)

September 22: Autumnal (fall) Equinox (equal day/night)

September 22: Astronomical fall begins (September 22 – December 20)

October 31: Furthest Perigee (370,200 km)

November 04: Fall Back. Daylight Time (DT) returns to Standard Time (ST) (Daylight Savings ends at Sunday at 02:00)

December 21: Astronomical winter begins (Dec 21 – Mar 19)

December 21: Winter Solstice; shortest day & lowest “Solar Noon” (Northern Hemisphere)


MARS: (687 day orbit)

March 24: Western Quadrature (270 degrees)

June 28: Stationary

July 27: Opposition (180 degrees)

August 28: Stationary

September 16: Perihelion (1.38 AU)

December 03: Eastern Quadrature (90 degrees)






VESTA (4 Vesta): (1,325 day or 3.63 year orbit)

June 19: Opposition (1.14 AU)





CERES (1 Ceres): (1,680 day or 4.6 year orbit)

February 07: Conjunction (1.6 AU)




JUPITER: (12 year orbit)

February 10: Western Quadrature (270 degrees)

March 09: Stationary

May 09: Opposition (180 degrees)

July 11: Stationary

August 06: Eastern Quadrature (90 degrees)

November 26: Conjunction (0 degrees)






SATURN: (29 year orbit)

March 29: Western Quadrature (270 degrees)

April 17: Aphelion

April 18: Stationary

June 27: Opposition (180 degrees)

September 06: Stationary

September 25: Eastern Quadrature (90 degrees)






URANUS: (84 year orbit)

January 02: Stationary

January 14: Eastern Quadrature (90 degrees)

April 18: Conjunction (0 degrees)

July 25: Western Quadrature (270 degrees)

August 07: Stationary

October 24: Opposition (180 degrees)






NEPTUNE: (165 year orbit)

March 04: Conjunction (0 degrees)

June 07: Western Quadrature (270 degrees)

June 19: Stationary

September 07: Opposition (180 degrees)

November 25: Stationary

December 05: Eastern Quadrature (90 degrees)






PLUTO: (248 year orbit)

January 12: Conjunction (0 degrees) (34.47 AU from Earth)

July 11: Opposition (180 degrees) (32.58 AU from Earth)





Perihelion: An objects closest approach to the Sun in its orbit.

Aphelion: An objects furthest point from the Sun in its orbit.

Perigee: An objects closest point to Earth in its orbit (Moon).

Apogee: An objects furthest point from Earth in its orbit (Moon).

Inferior Planet: Planets inside Earth’s orbit (Mercury & Venus).

Superior Planet: Planets outside Earth’s orbit (Mars, Jupiter, Saturn, Uranus & Neptune).

Terrestrial Planets: The four (4) rocky planets of the inner solar system (Mercury, Venus, Earth & Mars).

Jovian Planets: The four (4) gas giant planets of the outer solar system (Jupiter, Saturn, Uranus & Neptune).

Ice Giants: The extremely cold gas giants of the outer solar system (Uranus & Neptune).

Superior Conjunction: When an inferior (inner) planet is opposite the Sun from Earth (elongation of 0 degrees).

Inferior Conjunction: When an inferior (inner) planet is directly between the Sun & Earth (similar idea as the new moon) (elongation of 0 degrees).

Conjunction: When a superior (outer) planet is opposite the Sun from Earth (elongation of 0 degrees).

Opposition: When a superior (outer) planet is opposite the Earth from the Sun’s vantage point so on Earth we see it as a full disk. This is similar to when the Moon is full, its fully illuminated (elongation of 180 degrees).

Apparition: When a planet comes out from behind the Sun = superior conjunction (inner planets) or conjunction (outer planets) and begins to grow in apparent size as it heads toward inferior conjunction (inner planets) and opposition (outer planets).

Greatest Eastern Elongation: When an inferior planet comes out of superior conjunction it’s seen in the western sky after sunset. Its highest point is its greatest eastern elongation.

Greatest Western Elongation: When a planet comes out of inferior conjunction it’s seen in the eastern sky before sunrise. Its highest point on the sky is its greatest western elongation.

Eastern Quadrature: When superior (outer) planets are at an elongation of 90 degrees east of the Sun as viewed from Earth.

Western Quadrature: When superior (outer) planets are at an elongation of 90 degrees west of the Sun as viewed from Earth.

Stationary: When retrograde motion of an outer planet begins and ends & when an inferior planet reaches greatest Western or Eastern elongation. Its apparent motion on the sky becomes “stationary” momentarily.

Retrograde: When a superior (outer) planet appears to be moving backward on the night sky. This happens when Earth catches up to an outer planet and passes it on the inside.

Prograde: After the Earth has completed its pass of the superior (outer) planet its motion reassumes its normal direction of travel which for all planets is called prograde or direct motion.

Waxing: When the Moon or planet’s disk is growing in illumination from new up to full phase.

Waning: When the Moon or planet’s disk is decreasing in illumination from full to new.

Crescent: When the disk of the Moon or planet is less than 50% illuminated.

Gibbous: When the disk of the Moon or planet is more than 50% illuminated.

Solstice: (Summer & Winter) When Earth’s tilt is at its maximum twice annually creating the longest night in the winter and longest day in the summer.

Equinox: (Spring & Fall) When the Earth’s tilt is positioned twice annually to deliver equal day & night.

Cross Quarter: Markers mid-way between each of the Equinoxes & Solstices. All combined; the Equinoxes, Solstices and Cross Quarters create 8 markers throughout the year.

Celestial Phenomena: (Quadratures, oppositions, conjunctions etc.): http://eco.mtk.nao.ac.jp/cgi-bin/koyomi/cande/phenomena_en.cgi

British Astronomical Association (Computing section): http://britastro.org/computing/charts_asteroid.html

Major Solar System events in 2016: http://www.astropixels.com/ephemeris/astrocal/astrocal2016gmt.html

Planetary Aspects: http://cseligman.com/text/sky/aspects.htm

NMSU Planetary aspects page: http://astronomy.nmsu.edu/nicole/teaching/ASTR505/lectures/lecture08/slide09.html

Naked Eye Planets: http://www.nakedeyeplanets.com/

In-The-Sky: http://in-the-sky.org/newsindex.php?feed=outerplanets

TimeAndDate sunset/sunrise: http://www.timeanddate.com/worldclock/sunrise.html

USN sunrise/sunset: http://aa.usno.navy.mil/data/docs/RS_OneYear.php