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Mars Visits the Beehive


Last updated 6/13/2023 at 10:59am

Even a small, low-powered telescope should be enough to spot Mars crossing in front of the Beehive cluster low in the west.

At the beginning of June, the planet Mars will make a beautiful pass in front of the Beehive star cluster, and if you've got a small, low-powered telescope, you'll have a front-row seat.

You can see this cluster fairly well on a clear, dark night, far from city lights – especially when it reaches its highest in the early evening sky in April. This week after dark, however, the Beehive appears low in the west, among the faint stars of the zodiacal constellation Cancer.

Because its light must pass through a relatively thick column of atmosphere to reach our eyes this week, it might not be visible to the unaided eye, even from areas without light pollution.

There is another way to find it right now, however. That's by looking for the planet Mars, which now appears rather faintly just above and to the left of the brilliant planet Venus. In fact, on the evening of May 31, Mars will appear just to the west of the Beehive, and this should be a good night to view both with a small telescope. Even with bright moonlight this week, a telescope will show the stars of the cluster.

The show's not over on that night, though. As Mars orbits the sun, we can see its movement against the more distant stars if we're patient. On the evenings of June 1, 2 and 3, it will appear to cross the cluster. Even through binoculars, Mars' tiny orange disk will produce a lovely sight against the dozens of shimmering stars that form the Beehive.This, of course, is an optical illusion caused by the two appearing along the same line of sight. In reality, the Beehive is 577 light-years distant (about 3,394 trillion miles) while Mars is now some 18 million times closer ("only" about 187 million miles from us).

The Beehive cluster (aka the Praesepe) has been known to stargazers since at least the time of the Greek writer Aratos in 260 B.C. In 130 B.C., Hipparchus included it in his star catalog and called it "Little Cloud" or "Cloudy Star." And the second century A.D. astronomer Claudius Ptolemy described it in his famous book "Almagest" as "The Nebulous Mass in the Breast (of Cancer)".

Early sky watchers used this star cluster to forecast the weather. The ancient philosophers Aratos and Pliny both wrote that, when they could see the cluster, the skies would be fair, but when they couldn't, a violent storm must be on its way. Today, we know their technique works fairly well when the Beehive is high overhead because high cirrus clouds which often precede a storm can easily blot this cluster from view while leaving the rest of the sky seemingly unaffected.

Though ancient stargazers used the Beehive to help predict weather, they didn't know its true nature. That understanding didn't come until the early 17th century when astronomers aimed the newly invented telescope in its direction. Today, even inexpensive binoculars show the Beehive as a beautiful family of many faint stars.

This famous cluster is always worth checking out, but with Mars passing in front of it next week it becomes a perfect opportunity!

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