As told in the latest episode of our long-running Sky Tour astronomy podcast, this month it’ll be challenging to a special kind of lunar eclipse on March 25th — but easy to spot five of the 10 brightest stars in the night sky.

This episode is sponsored by Celestron, manufacturer of high-quality telescopes and an industry leader in developing exciting optical products with revolutionary technologies.

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The month of March always brings two events with celestial consequences. The first is “Daylight Savings Time.” The U.S. and Canada will make that annual adjustmenton March 10th. However, in Europe, the switch isn’t until March 31st. There are all kinds of arguments for and against having daylight time, but for astronomers the upshot is this: Once daylight or summer time kicks in, it won’t get dark after sunset until the clock time is an hour later in the evening.

The other one is the equinox. Maybe you’ve heard this called the vernal or spring equinox, because it signals the beginning of astronomical spring in the Northern Hemisphere. But likewise, it’s the start of autumn in the Southern Hemisphere. This month it occurs on the 19th at 11:06 p.m. Eastern Time. Why so early? In any given year, the March equinox occurs 5 hours 49 minutes later than the previous year’s. But during a leap year, such as 2024, it occurs 18 hours 11 minutes earlier than the previous year, and that’s why this year it falls on March 19th.

The full Moon comes on the 25th, and a lunar eclipse occurs that night. But this one is a geometric oddity. The Moon will glide deeply into Earth’s penumbra, our planet’s weak outer shadow, but not the darker umbra. We see this drop in sunlight as merely a dusky shading on the lunar disk that gets gradually more obvious as the Moon dives deeper into the penumbra. The timing of this eclipse favors observers in the Americas. For those on the East Coast, it occurs in the first hours of March 25th, with mid-eclipse at 3:13 a.m. EDT. On the West Coast, the eclipse begins in late evening on the 24th and climaxes just after midnight.

Planet-wise, Venus and Mars are very low in the east before sunrise. Meanwhile, after sunset, Jupiter is gradually sinking toward evening twilight, but Mercury is gradually rising to the big planet’s lower right. In fact, during late March, Mercury makes its best evening showing of the whole year. To spot this fast-moving little planet, listen to this month’s Sky Tour podcast for my advice on where and when to look for it.

As the twilight fades, turn left, away from the sunset point, until you’re looking south. There in the deepening blue, you’ll find the first true star of the evening: brilliant Sirius. How early in twilight can you pick it up? Anytime during the first days of March, before the switch to daylight time, make note of the horizon point directly below this beacon at 8 p.m. — that’s very nearly due south. Or look in the star’s direction around 9 p.m. after the time switch.

There’s much more going on in the evening sky during March. For example, did you know that this month you can easily spot five of the 10 brightest stars in the night sky — and six if you live south of +35° in latitude? To find them — and many other celestial sights in view this month — stream or download March’s Sky Tour astronomy podcast. It’s a fun and informative way to learn your way round the night sky.

Read the full podcast transcript.


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March 4, 2024 at 10:31 pm

There's an unsung property of lunar eclipses that's especially worth remembering for a penumbral eclipse (which otherwise is mostly a non-event): The Moon is BRIGHTEST in terms of surface brightness (magnitudes per square minute of arc) just as it's entering the penumbra due to the "opposition surge" which makes the Moon much brighter when its angle from the Sun is very close to 180°, meaning just outside the Earth's shadow for us terrestrial observers. The overall or total brightness of the Moon this time around will be less than the maximum possible since this Full Moon is smaller than average in apparent diameter. March 25 is near apogee which makes the Moon small on that date but guarantees a big Moon for excellent solar eclipse geometry at perigee two weeks later on April 8). Nonetheless the "glow" of the Moon's face --that's surface brightness-- is dazzling just as the Moon enters the penumbra. And this is noticeably brighter than "average" Full Moons when the Moon misses the shadow by up to five degrees.

I started looking at this a couple of years ago and thought I might be onto something that had never made it into print, at least in popular articles, but of course the prolific author and computer of all things astronomical, Jean Meeus, wrote about it a quarter century ago in his book "More Mathematical Astronomy Morsels". And yet it's still not widely enough known. The Moon is a brilliant beacon just as it enters the penumbra.

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