Leap Day. Monday is the extra day we add to the end of February every four years to correct our calendar.
Earth actually takes 365.2422 days to complete one trip around the sun, and as a result our calendar falls behind by about a quarter day each year. So we tag on a full day every fourth year, making it 366 days. This helps keep our calendar in sync with Earth’s movements and seasons.
But that creates another issue. Leap years are about 11 minutes longer than Earth’s real orbital period. To fix this, we skip the extra day in years that are divisible by 100 but not divisible by 400. So there were no leap years in 1700, 1800, and 1900, and we won’t have one in 2100, 2200, or 2300.
Zodiacal Light. With the moon relegated to the early morning hours, evening skywatchers will have ideal conditions to spot the elusive zodiacal light this week.
The ethereal effect is caused by sunlight reflecting off dust particles scattered between the planets. Ancient Romans thought this ghostly glow came from far-off campfires below the horizon, while the ancient Greeks speculated that it must be caused by distant volcanic explosions.
The phenomenon is best seen by observers across the mid-northern latitudes. Over the next two weeks, look for a pyramid-shaped glow—fainter than the Milky Way—rising above the western horizon after sunset.
Lunar Triad. Before dawn on Tuesday, March 1, look toward the southeast skies for the last quarter moon wedged between the two bright planets, Mars and Saturn.
The Red Planet will be to the right and will appear to shine with a distinct orange hue visible to the naked-eye. Yellow-colored Saturn, whose rings are easily discerned with even the smallest of backyard telescopes, will be to the lower left. Look beneath this triad to see Antares, the brightest star in the constellation Scorpius.
By Wednesday morning, the moon will have sunk closer to the horizon and parked itself to the upper left of Saturn. The pair will be separated by only three degrees—equal to about the width of your three middle fingers held at arm's length.
Blooming Flower. With dark, moonless evening skies this week, it’s a perfect time to hunt down a spectacular deep-sky treasure known to backyard stargazers around the world: the Great Orion Nebula.
This grand star factory—also called Messier 42—is 14,00 light years from Earth and is nestled within the bright constellation Orion. It will be visible in the southern sky in the early evening this week. To start your hunt, look for for a line of three bright stars—this is the belt of Orion. At right angle, below the belt is the sword, made up of another, fainter line of three stars. From there, any backyard telescope will reveal the Great Orion Nebula, a fan-shaped glowing cloud of fluorescent gas and dust some 40 light years across.
The nebula’s shine comes from four massive baby stars, each no more than one million years old (our sun is nearly 5 billion years old).
Recent observations with the Hubble Space Telescope show that Orion is home to hundreds of other unseen stars—some of them probably only a few thousand years old—that are just starting to form planetary systems much like our own.