The Sky Tour astronomy podcast for March 2019 takes you on a guided tour of the predawn sky and then helps you find the dazzling stars that make the huge Winter Hexagon — including Sirius, the Dog Star.

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Daylight time around the world
Most of the world's population doesn't switch back and forth to daylight-saving time.
J. Kelly Beatty / Sky & Telescope

This month we’ll "clock" your interest in the switch to Daylight Time, cycle through the Moon's phases, check out three worlds at dawn, and focus on brilliant Sirius, the anchor star of the stunning Winter Hexagon. Read on!

March features two space-time events that have almost nothing to do with the starry sky itself but which definitely affect our enjoyment of it.

First, on March 20th at 5:58 p.m. Eastern Daylight Time, Earth reaches one of the two equinox points in its year-long orbit. But there's more to it than just "the beginning of northern spring, astronomically speaking." Equinox comes from the Latin word aequinoctium, meaning "equal nights." On this date, days and nights everywhere are both 12 hours long. And on the equinox, the Sun rises due east and sets due west no matter where you are.

Second, March is when billions of clocks "spring forward" in a shift to Daylight Savings time. But the date for all that time-shifting varies: It comes on March 10th in the U.S. and Canada but three weeks later, the 31st, across Europe — and four weeks later in parts of Mexico. And because autumn is approaching Down Under, on April 7th Australians will switch back to standard time. If this sounds confusing, well, it is! And for mid-northern skywatchers, daylight time means the sky doesn't get dark until well into the evening hours, especially in midsummer. For more on this whole subject, check out my "Bah, Humbug" blog.

Morning view in early March 2019
Venus, Saturn, and Jupiter (out of view at upper right) dominate the eastern sky before dawn in March 2019. A crescent Moon adds an extra visual treat early in the month.
Sky & Telescope

Daylight time aside, there's plenty to see both before the Sun rises and after it sets. Before dawn, we'll check out the diagonal lineup of Venus, Saturn, and Jupiter that's now dominating the eastern sky. As the illustration at right shows, the waning crescent Moon joins them in the first days of March. (Did you know there's a spacecraft called Juno that's orbiting Jupiter right now?)

Switching to the evening sky, shortly after sunset we find Mars well up in the southwest. And if you're quick to get outside in early March, look for Mercury just above the western horizon about 30 or 45 minutes after the Sun goes down.

But what really grabs your attention is the incredible array of beautifully bright stars awaiting you in the southern half of the sky beginning about an hour after sunset. Listen to this month's Sky Tour astronomy podcast, and you'll get to know each of them by name. Together they form a giant six-sided pattern in the sky called the Winter Hexagon. And our podcast explores the myths and mythology of Sirius, the night sky's brightest star.

To find out where and when to spot all these sky sights, play or download this month's episode.


Image of John Sheff

John Sheff

March 5, 2019 at 4:49 pm

Hi, Kelly,
Is it the case that the day and night are both 12 hours long on the equinox? Atmospheric refraction aside, sunrise and sunset are defined as the instant the TOP limb of the Sun is on the horizon. Since the Sun has a finite diameter, the top of the Sun will reach the horizon before the center at sunrise, and after the center at sunset. Won't this (slightly) prolong the period of daylight vs. nighttime on the equinox?
I've heard reference to the "equilux", which occurs a few days before the spring equinox, and a few days after the fall equinox, as the times when the length of day and night are equal. What do you think?

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Image of Kelly Beatty

Kelly Beatty

March 6, 2019 at 10:16 am

John, you're correct that on the equinox days and nights are almost (but not quite) 12 hours each. we reckon sunrise/sunset times using the uppermost bit of the Sun's limb, and of course there's refraction. so really "sunrise" occurs when the center of the solar disk is still 50 arcminutes (16 arcmin radius + 34 arcmin refraction) below the horizon. hee's a good descriptive page for more info:

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