Fred Barrett | Mar 08, 2017
Did you know that the Earth is not a perfect sphere? There’s a special area of study in mathematics that involves measurements of Earth. It is called ‘geodesty’. It got its start in the 17th century when improvements in the field of astronomy made astronomical measurements more accurate. A need for precise mathematical descriptions became necessary. Earth can be described as a flattened sphere or more mathematically, as an oblate spheroid. This is a sphere that is wider at its horizontal axis than it is at the vertical axis. Due to the Earth’s rotational velocity (1674.4 Km/h), our planet is flattened at the poles and bulges at the equator. Our planet’s diameter between the poles is about 12,713 Km and at the equator roughly 12,756 Km, a difference of 43 Km. Other planets in the Solar system exhibit similar differences that depend on planet size and speed of rotation. Jupiter and Saturn, gas giants, are excellent examples. Our Sun and the stars in the sky are measurably broad in the beam as well.
I described Venus last month as being an ‘evening’ and a ‘morning’ star. This month we have a visual example of that transition from evening to morning. In early March, Venus is bright in the west from sunset to about 8:30 pm when it disappears below the horizon. As the month progresses Venus’s orbit carries it closer to Earth and the size of its disk increases but its crescent, that part of Venus lit by the Sun, decreases. A good set of binoculars should allow you to actually see it as a crescent not as the star like point of light that your eyes observe. March 25th marks inferior conjunction where it sits between the Sun and Earth and is at its closest. No light will be reflected our way. Venus will be past conjunction by the end of the month and will become visible as a ‘morning’ star just before dawn. Its crescent will now be on the opposite side of its disk and will grow larger as it retreats away from us.
Jupiter rises late in the evening (around 9 pm) in early March and is a marvelous sight throughout the night. It will be in opposition in early April and will appear huge and beautiful. Saturn and Venus share the sky with Jupiter in the early morning by the end of the month. Mars is visible in the west all through March in the early evening.
Watch for the pyramid shape of the zodiacal light in the west at twilight. It will fade by late March. Sunlight reflecting off of debris and dust along the ecliptic in the inner Solar system creates this phenomenon. It’s quite something to see.
There’s a comet out there! It’s called Comet 41P/Tuttle-Giacobini-Krusak. It should be best towards the end of March. Use binoculars for the best view. If you are at a dark site, it might even be visible by naked eye. This comet comes around every 5.4 years and its visibility varies greatly each time. Its name gives credit to 3 astronomers. American Horace Tuttle discovered it in 1858. Frenchman Michel Giacobini rediscovered it in 1907 and Slovakian Lubox Krusak found it in 1951. It was only noticed 3 times over the course of a century! But have heart! This time it has an especially close path by Earth. Hopefully it might even sputter more gas and debris to improve its visibility. It will be flying just under the bowl of the Big Dipper (Ursa Major) near the end of March. On March 27th, it will be just below the fairly bright star Dubhe in the Big Dipper.
Highlights for March.
March 10th: Regulus is just north of the Moon about 6 pm.
March 12th: Full Moon. So many names this month:
Full Worm Moon. The warming ground marks the appearance of worms. Not likely to crawl around here for a while!
Full Crow Moon. I have noticed that the crows are getting a tad restless. Maybe being -20 degrees C tonight will shut them up!
Full Crust Moon. Our tropical late February and sudden return of Winter has made life a bit crusty.
Full Sap Moon. Definitely an early run this year. Hope weather returns to normal.
March 18th: The Moon is at apogee, farthest from the Earth in its orbit - 402,300 Km.
March 20th: Saturn passes 3 degrees south of the Moon around 6 am. Last quarter Moon around Noon. The Vernal Equinox occurs at 6:29 am.
March 25th: Venus is at inferior conjunction.
March 27th: New Moon.
March 30th: Moon at perigee, closest to Earth – 361,741 Km
Watch for that comet!
Keep looking up!
“The Beginners Observing Guide” by Leo Enright is an invaluable companion for adventures in the night sky. It contains star charts and is packed with information. It can be purchased at the Sharbot Lake pharmacy or it can be ordered from the Royal Astronomical Society of Canada at www.rasc.ca/publications. A subscription to our very own excellent Canadian astronomy magazine “SkyNews”, with its centerfold sky chart, can be ordered at the RASC site as well.
Clear Skies! Fred