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Moon in Cancer on evening of June 8

Tonight – June 8, 2016 – the waxing crescent moon beams in front of the constellation Cancer, the faintest constellation of the zodiac. We draw in the stick figure of Cancer for you on the star chart above. In the sky, you might not pick out any stars in the moon’s vicinity, unless your sky is very dark. But Cancer’s stars will be there, behind the moon’s glare, all the same.

Zodiacal constellations like Cancer distinguish themselves from other constellations in that the sun, moon and planets travel within their borders over the centuries and millennia.

The sun travels in front of the constellation Cancer from about July 21 to August 10 annually. That may seem to be at odds with the horoscope page in the newspaper, which probably gives the sun’s passage through Cancer for around June 21 to July 21.

Why the discrepancy? It’s because a zodiac sign is different from a zodiac constellation, though people often confuse the two.

Here’s the definition of a zodiac sign. By definition, the sun is always at the first point of the sign Cancer on the June solstice, irrespective of which group of stars backdrops the sun at this time. Look at the globe to note the Tropic of Cancer, which marks the northernmost extent of the sun’s travels on the June solstice.

Worldwide map showing the Tropic of Cancer

View larger. The red line shows the tropic of Cancer, where the noontime  sun is at zenith (straight overhead) on the day of the June solstice.

View larger. The red line shows the Tropic of Cancer, where the noontime sun is at zenith (straight overhead) on the day of the June solstice.

Here’s the definition of a zodiac constellation. Any constellation can be thought of as a section of the starry sky, seen and wondered about for millennia by stargazers. In our time, constellations have official borders, which were agreed upon by the International Astronomical Union in the 1930s.

Over two thousand years ago, the sun actually shone in front of the constellation Cancer on the June solstice. Today, the June solstice sun shines in front of the constellation Taurus. Therefore, the first point of the sign Cancer presently resides in the constellation Taurus.

Because the Earth’s axis continually changes its tilt relative to the backdrop stars, the June solstice sun swings westward through all the constellations of the zodiac in a period of about 26,000 years. All the while, the June solstice sun always marks the first point of the sign Cancer.

Dates of sun’s entry into each constellation of the zodiac

Dates of sun’s entry into zodiac signs

Bottom line: If your sky is extremely dark, you might be able to see for yourself that the waxing crescent moon is in front of Cancer the Crab on June 8, 2016.

Bruce McClure

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