Astronomy Essentials

Sun’s entry into zodiac constellations, 2021

Antique etching of sky with stars and an old man in Greek garb carrying a long snake.
Ophiuchus the Serpent Bearer isn’t an astrological sign, but it is one of the constellations of the zodiac. In other words, many people are born when the sun appears in front of this constellation. In 2020, the sun crossed into Ophiuchus on November 29. Image via

You might know that the real sun in the real sky does not appear in front of a constellation of the zodiac within the same range of dates you’ll see listed in astrological horoscopes. That’s because astrology and astronomy are different systems. Astrologers typically indicate the sun’s position with signs while astronomers use constellations. We were asked for:

… a list of the constellations that fall on the ecliptic with the exact degrees.

And we’ve located this information in Guy Ottewell’s Astronomical Calendar 2021. Below, you’ll find the dates for the sun’s entry into each zodiacal constellation during the year 2021, plus the sun’s ecliptic longitude – its position east of the March equinox point on the ecliptic – for each given date.

We are using the boundaries for the zodiacal constellations established by the International Astronomical Union in the 1930s.

Moon lovers! Get this year’s EarthSky lunar calendar here. Order now – going fast!

Sun-centered celestial globe with latitude and longitude lines.
The sun resides at a longitude of 0 degrees on the ecliptic at the March equinox. The sun is at 90 degrees ecliptic longitude at the June solstice, 180 degrees ecliptic longitude at the September equinox and 270 degrees ecliptic longitude on the December solstice. Image via Wikipedia.

Date of sun’s entry into each zodiacal constellation (and corresponding ecliptic longitude):

Dec 18, 2020: Sun enters constellation Sagittarius (266.62 degrees)

Jan 19, 2021: Sun enters constellation Capricornus (299.74 degrees)

Feb 16, 2021: Sun enters constellation Aquarius (327.92 degrees)

Mar 11, 2021: Sun enters constellation Pisces (351.60 degrees)

Apr 18, 2021: Sun enters constellation Aries (29.12 degrees)

May 14, 2021: Sun enters constellation Taurus (53.50 degrees)

Jun 21, 2021: Sun enters constellation Gemini (90.46 degrees)

Jul 20, 2021: Sun enters constellation Cancer (118.29 degrees)

Aug 10, 2021: Sun enters constellation Leo (138.21 degrees)

Sep 16, 2021: Sun enters constellation Virgo (174.19 degrees)

Oct 31, 2021: Sun enters constellation Libra (217.83 degrees)

Nov 23, 2021: Sun enters constellation Scorpius (241.17 degrees)

Nov 30, 2021: Sun enters constellation Ophiuchus (248.07 degrees)

Dec 18, 2021: Sun enters constellation Sagittarius (266.63 degrees)

Source: Timetable of astronomical events by Guy Ottewell

Visit Heavens-Above to know which constellation of the zodiac presently backdrops the sun.

Celestial sphere with grid, celestial equator, and ecliptic, and Earth in the center.
Earth-centered ecliptic coordinates as seen from outside the celestial sphere. Ecliptic longitude (red) is measured along the ecliptic from the vernal equinox at 0 degrees longitude. Ecliptic latitude (yellow) is measured perpendicular to the ecliptic. Image via Wikimedia Commons.

Constellations of the zodiac:

Taurus? Here’s your constellation
Gemini? Here’s your constellation
Cancer? Here’s your constellation
Leo? Here’s your constellation
Virgo? Here’s your constellation
Libra? Here’s your constellation
Scorpius? Here’s your constellation
Sagittarius? Here’s your constellation
Capricornus? Here’s your constellation
Aquarius? Here’s your constellation
Pisces? Here’s your constellation
Aries? Here’s your constellation
Birthday late November to early December? Here’s your constellation

Chart with astrological signs on left and constellations on right by month.
Dates of sun’s entry into astrological signs versus astronomical constellations are the same in 2021 as in 2016. Chart and more explanation at Guy’s Ottewell’s blog. Used with permission.

Bottom line: Sun-entry dates to zodiac constellations in 2021, using boundaries for constellations set by the International Astronomical Union in the 1930s.

Click here to learn dates the sun enters each sign of the zodiac.

What is the zodiac?

December 28, 2020
Astronomy Essentials

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Bruce McClure

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