Closest planetary conjunction on March 3

Watch for this to occur with Venus, Mercury just after sunset

Mercury makes its best evening appearance of the year in March. This is primarily due to the ecliptic (the apparent path of the sun, moon and planets across the sky) tilts at a steeper angle to the horizon at this time of the year, enabling Mercury to briefly appear higher in the sky than normal.

Mercury is in close proximity with its inner-solar system neighbour, Venus, this month. The two planets appear close together in the western sky just after sunset. On March 1, Venus (mag. -3.9) appears about 5 degrees above the western horizon about 1/2 hour after sunset, with a much dimmer (mag. -1.3) Mercury to its lower right. On March 3, they are side by side, with Mercury 1.1 degrees to the right. This is the closest planetary conjunction of 2018.

During the first three weeks of March, the two planets (moving through the constellation of Pegasus - the Winged Horse) fit within the same binocular field of view. Both will climb higher in the evening sky away from the glare of the setting sun during the first two weeks of the month, with Mercury climbing higher faster.

By March 15, when Mercury reaches its greatest elongation from the sun (and its highest elevation in the dusk sky), it is well by Venus, sitting about 12 degrees (a little more than a hand’s width at arm’s length) above the western horizon about 30 minutes after sunset. After this date, Mercury begins to, once again, sink lower in the evening sky. On March 18, the crescent moon sits 4 degrees to the left of Venus, with a much dimmer (mag. -0.4) Mercury the same distance to the upper right of Venus about 10 degrees above the horizon 30 mins. after sunset.

Jupiter, now in the constellation of Libra - the Scales, rises over the eastern horizon shortly before midnight. Shining at mag. -2.2 in early March, Jupiter is only a bit brighter (mag. -2.4) by month’s end. It is best viewed about 1 - 2 hrs. before dawn, when it sits at its highest point in the southern pre-dawn sky. During that period of time, Jupiter’s light shines through less of Earth’s atmosphere, providing less distortion and a crisper view. On March 7, look for the waning gibbous moon just to the upper left of Jupiter.

Mars rises in the SE a couple of hours after Jupiter. The Red Planet is beginning its journey towards its best apparition in the last 15 years, which will take place in July of this year. It begins the month shining at mag. +0.8 in the constellation of Ophiuchus - the Serpent Bearer, but moves into Sagittarius - the Sea Goat by March 12. Saturn (mag. +0.5) rises about 70 minutes after Mars as March opens, but only about one minute after by the end of the month.

On the morning of March 10, the waning, gibbous moon sits above and between Saturn (on the left) and Mars (on the right), with all three sitting just above the “teapot” asterism in the constellation of Sagittarius in the SSE sky. Mars (mag. +0.2) sits just below a dimmer Saturn (mag. +0.5) in the southern dawn sky on April 2. This is the second closest planetary conjunction of the year, after the Venus-Mercury conjunction of March 3 (see previous).

Don’t forget to watch for the Zodiacal Light (see last month’s article) in the western sky just after sunset. It’s best between March 3-18, when the moon is out of the sky.

The vernal equinox, the official commencement of spring here in the northern hemisphere, occurs on March 20 at 1:15 p.m. ADST this year.

There is another blue moon (our second of the year) this month, when the second full moon of the month occurs on Mar. 31. The first occurs on March 1.

Don’t forget, turn your clocks ahead one hour on March 11 at 2 a.m., when we begin Daylight Saving Time.

** Note: Since the regularly scheduled date of my article is not until the first Wednesday of each month, which may, upon occasion, not be until after the seventh of the month, I will attempt to include any significant astronomical events for that

first week of the month in the previous month’s article.

Until next month, clear skies and good viewing. Glenn K. Roberts lives in Stratford, P.E.I., and has been an avid amateur astronomer since he was a small child. His column appears in The Guardian on the first Wednesday of each month. He welcomes comments from readers, and anyone who would like to do so is encouraged to email him at glennkroberts@gmail.com.