April Skies: Copernicus and Galileo responsible for setting the record straight

Saskatchewan Skies

James Edgar

The moon is waning to a very thin crescent as April begins, snuggling up to Venus in the early morning eastern sky on the 2nd. Much later that same day, the moon and Mercury have a close encounter, but it will be a very tough observation as the sun rises just about the time Mercury becomes visible in the east and the moon is but a mere sliver in the twilight. The moon is new on the 5th. Mars is five degrees north of our satellite on the 9th; the moon is among the stars of the Beehive Cluster (M44) on the 13th; full moon is on the 19th; Jupiter is less than two degrees south on the 23rd; Saturn and Pluto are both involved in occultations on the opposite side of the globe from North America – close encounters here.

Mercury is in the morning sky throughout April, achieving greatest elongation of 28 degrees on the 11th. Even though this is a great chance to see the speedy planet so far from the sun, celestial geometry favours southern viewers, as Mercury just clears the horizon at daybreak.

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Venus much the same can be said about the bright planet, hugging the horizon right alongside Mercury in the morning twilight. Neptune is between Mercury and Venus for a few days around April 5 to 8, but you’ll likely need a telescope to see the gas planet.

Mars is high in the stars of the Pleiades (the Seven Sisters), gradually working its way over to the stars of Taurus, The Bull. The nearby crescent moon on the 8th and 9th make a nice pairing for astrophotographers.

Jupiter has been moving in proper motion for a few months, but begins retrograding on the 10th, apparently moving westward against the starry background. Remember, it’s us on the Earth who are moving faster to make this counterintuitive motion seem possible. Ancient astronomers had a tough time trying to explain this away, coming up with all sorts of nonsense. Copernicus and Galileo were responsible for setting the record straight.

Saturn remains in the sky alongside the stars of Sagittarius, The Archer. Watch for the moon sliding by on the 25th, an occultation in the South Pacific.

Uranus joins a mighty lineup on the last day of April with, in order westward from the Sun, Mercury, Venus, Neptune, the moon, Saturn and Jupiter. You have to be quick to see it all, though, as it occurs right at sunrise. Probably Uranus can’t be seen at all, as it is so close to the sun.

Neptune is gradually coming out from behind the sun in the morning sky, joining in the lineup mentioned above on the 30th, positioned right above the moon.

James Edgar has had an interest in the night sky all his life. He joined The Royal Astronomical Society of Canada in 2000, was National President for two terms, is now the Editor of the renowned Observer’s Handbook, and Production Manager of the bi-monthly RASC Journal. The IAU named asteroid 1995 XC5 “(22421) Jamesedgar” in his honour.


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