How to Catch the Transits of Mercury and the 'Demon Star' This Month

Allexxandar/iStock via Getty Images
Allexxandar/iStock via Getty Images

This month's sky-gazing event calendar is all about transits. In astronomy, a transit occurs when one celestial body appears to pass directly in front of another in the night sky, causing the light from one body to diminish in some cases. As Geek reports, there are two main transits to look out for in November: that of Mercury moving across the sun and the dimming and brightening of the "demon star" Algol.

What is a Mercury transit?

Mercury is currently in retrograde (though you shouldn't blame that for any chaos in your personal life). As the innermost planet travels "backwards" across the sky this month, it will make a rare detour past the face of the sun on November 11. Mercury's transit across the sun is something that only happens roughly 13 times every 100 years. Such an event won't be seen again in the U.S. until 2049.

This time around, it will take Mercury about five and a half hours—starting just after sunrise on the East Coast—to make the full journey from one end of the bright yellow disc to the other.

What is a "demon star" transit?

The transit of Algol, also known as the demon star, is a much more common event, but it's no less spectacular. Algol is really two stars in the constellation Perseus that are constantly orbiting each other. Every 2.86736 days, the smaller star of the pair passes in front of the larger star, making it appear slightly dimmer for 10 hours at a time. In the first half of the month, most of these transits occur after sunset on the East Coast, which is the best time to observe the transition. The next is set for November 9 at 3:17 a.m. EST, with the one after that taking place on November 12, six minutes after midnight.

Algol gets its monstrous nickname from a classic villain of Greek mythology. The star is supposed to resemble the winking, snake-haired head of the gorgon Medusa, who was slain by Perseus. Algol is a name derived from an Arabic word meaning "the demon's head."

How to see Mercury's and Algol's transits

To see both of these events, you'll need some special equipment. Looking directly at the sun is never a good idea, and NASA recommends using a telescope with a certified sun filter to watch Mercury's transit safely on November 11. A solar projection box or sun funnel would also allow you to observe the planet's passage without damaging your eyes.

There's no harm in looking straight at the twin stars that make up Algol, but you'll have trouble seeing them "blink" with your naked eye. For that event, a regular telescope or binoculars would do.

[h/t Geek]

The Moon Will Make Mars Disappear Next Week

Take a break from stargazing to watch the moon swallow Mars on February 18.
Take a break from stargazing to watch the moon swallow Mars on February 18.
Pitris/iStock via Getty Images

On Tuesday, February 18, the moon will float right in front of Mars, completely obscuring it from view.

The moon covers Mars relatively often—according to Sky & Telescope, it will happen five times this year alone—but we don’t always get to see it from Earth. Next week, however, residents of North America can look up to see what’s called a lunar occultation in action. The moon's orbit will bring it between Earth and Mars, allowing the moon to "swallow" the Red Planet over the course of 14 seconds. Mars will stay hidden for just under 90 minutes, and then reemerge from behind the moon.

Depending on where you live, you might have to set your alarm quite a bit earlier than you usually do in order to catch the show. In general, people in eastern parts of the country will see Mars disappear a little later; in Phoenix, for example, it’ll happen at 4:37:27 a.m., Chicagoans can watch it at 6:07:10 a.m., and New Yorkers might even already be awake when the moon swallows Mars at 7:36:37 a.m.

If you can’t help but hit the snooze button, you can skip the disappearing act (also called immersion) and wait for Mars to reappear on the other side of the moon (called emersion). Emersion times vary based on location, too, but they’re around an hour and a half later than immersion times on average. You can check the specific times for hundreds of cities across the country here [PDF].

Since it takes only 14 seconds for Mars to fully vanish (or reemerge), punctuality is a necessity—and so is optical aid. Mars won’t be bright enough for you to see it with your naked eye, so Sky & Telescope recommends looking skyward through binoculars or a telescope.

Thinking of holding an early-morning viewing party on Tuesday? Here are 10 riveting facts about Mars that you can use to impress your guests.

[h/t Sky & Telescope]

A Snow Moon Will Light Up February Skies

makasana, iStock via Getty Images
makasana, iStock via Getty Images

February is the snowiest month of the year in many parts of the U.S., but on February 9, consider braving the weather outside to look up at the sky. That Sunday morning, the only full snow moon of the year will be visible. Here's what you need to know about the celestial event.

What is a snow moon?

If you keep track of the phases of the moon, you may already know that the full moon of each month has its own special name. Following January's wolf moon lunar eclipse is a snow moon in February. The name snow moon is said to have originated with Native American tribes, and it refers to the heavy snowfall that hits many parts of North America in February.

According to The Old Farmer's Almanac, different tribes had different names for February's full moon. The Wishram people named it the shoulder to shoulder around the fire moon and the Cherokee people called it the bone moon because animal bones were sometimes their only source of nutrition in the dead of winter. Snow moon is the name that's most commonly used by almanacs today.

When to See the Snow Moon

The moon will enter its next full phase the morning of Sunday, February 9. The snow moon will be at its fullest at 2:34 a.m. EST, but if you're not willing to stay up that late, it's still worth looking up. The previous evening—Saturday, February 8—the moon will be 99 percent illuminated on the East Coast. Check your local weather forecast and find a spot with clear skies to get the best view of the wintertime spectacle.

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