Weekend Sky Report

Comet 46P, also known as Comet Wirtanen after the man who discovered it in 1948—American astronomer Carl Wirtanen, will come close enough to Earth to be visible to the naked eye under dark skies. Those of us in the city and suburbs though will probably still need a telescope or binoculars.

Comet Wirtanen is part of the Jupiter family of comets, which means the farthest it travels from the sun is about Jupiter’s orbit… around 800 million miles. And it makes that journey around the sun and back about every five and a half years. This makes it what’s called a short period comet. Short in that it takes less than 200 years to make an orbit of the sun. Halley’s Comet is a short period comet, coming around every 76 years or so. Some comets take thousands, even millions of years to complete an orbit. Because of its frequency, Comet Wirtanen was the original target for the European Space Agency’s Rosetta Mission, but the spacecraft took too long to build, so they missed the launch window.

While this comet may orbit the sun more frequently than others, it very rarely comes close enough to see with the naked eye. Comet Wirtanen will be brightest on Sunday night, but it will be visible all weekend in the evening sky. Again, you might need the help of binoculars or a telescope unless you have dark skies.

You’ll find the comet between the Pleiades and Aldebaran, the orange eye of Taurus The Bull. Friday night it’ll be to the right of the two clusters. Saturday and Sunday night it’ll be right below the Pleiades. It’ll look like a dim greenish blue star with a halo around it.

If you see it, you’ll be looking at a comet that hasn’t swung this close to Earth in over 300 years.

Look low on the eastern sky around 8:30 tonight and you’ll see it. It’s unmistakable.

Orion.

The three stars that make up Orion’s belt is the giveaway. But there’s a lot more to appreciate. Like Rigel… Orion’s bright blue left foot. Rigel is an enormous, hot star that’s actually part of a system of 3 to 5 stars, but we can only see the biggest, brightest one—Rigel A. Rigel is 20 times more massive than the sun, 80 times bigger, and tens of THOUSANDS of times brighter. It’s also young… only around 9 million years old.

But the biggest star in Orion is his bright orange right shoulder, one of the largest stars we know of. Betelgeuse. Betelgeuse is so big that if we were to swap it with our sun, its surface would reach beyond the orbit of Mars.

Now you don’t need a telescope to appreciate the brightest stars of Orion, but I’d get it out anyway… because the Orion Nebula has hooked so many people on astronomy. You can see it with almost any telescope. And we’ve learned a lot from it. The Orion Nebula is a stellar nursery. New stars form there from collapsing clouds of gas and dust. And almost everything we know about stellar nurseries came from studying the Orion Nebula. If you make a triangle with the center of the belt, Rigel, the left foot, and Saiph, the right knee of Orion, the nebula is right in the middle. You can’t miss it.

So tonight, bundle up, embrace the cold weather… and spend some time with Orion The Hunter.

This weekend’s target is a classic cold weather cluster right next door to its famous half-sisters.

Right in the center of Taurus the Bull is the bright orange giant Aldebaran. Aldebaran is close… just over 60 light years away. And because of that, it’s easy to miss what’s behind it… about 90 light years behind it, to be exact. But even then, at over 150 light years away, the Hyades is one of the closest open star clusters. Compare that to the Pleiades at well over 400 light years away.

In Greek mythology, the Hyades are daughters of Atlas. As are the Pleiades… and following the death of their brother Hyas, their grief transformed them into stars. And their weeping for the loss of their brother… makes the rain.

When it’s not raining, you can see the Hyades by finding their sisters, the Pleiades in the eastern sky this evening. When you find the Pleiades, which is a cluster of bright blue stars you can easily see with the naked eye, look beneath it to find the bright, orange Aldebaran. Then grab your binoculars or any telescope and look straight at it… you’ll notice several bright white and yellowish stars just below and to the right of Aldebaran. ..and there you have it. The Hyades. Now, along with Aldebaran, the four brightest stars of the Hyades make up the head of Taurus the Bull. And since the Hyades is one of the closest and most studied open star clusters in the sky, we’ve known for a while why those four stars are so much brighter than the rest of the cluster. They’ve exhausted their core hydrogen and are evolving into giants. One of the final stages before their demise… in a few million years.

Let’s celebrate what we hope will be another successful landing... on the Red Planet.

It’s hard to believe it’s been six years since Curiosity successfully landed on Mars. Since then we’ve learned a lot from the rover… including the incredible discovery of complex organic molecules… hints that perhaps life once existed there… or maybe it still does. Curiosity is still operational and still gathering important data. But Mars is about to get another earthly companion.

On Monday, if all goes well, NASA’s InSight lander will touch down near the Martian equator and begin its two year mission to gather geological data. Unlike Curiosity, Sojourner, or Opportunity, this lander won’t have wheels. It’ll stay put… and for the first time ever, geologists will be able to record earthquakes… or rather… MARSquakes and send back the data to give scientists a sense of what the interior of the planet is like. We’re already pretty sure that, unlike on Earth, plate tectonics isn’t responsible for the geological activity… something else is at work. But we do know that it has volcanoes. In fact, it has the largest volcano in the solar system… Olympus Mons at 14 miles high. Compare that to Mount Everest at a paltry 5 and-a-half.

To celebrate the upcoming InSight landing, have a look at Mars this weekend. After all, it’s about the only thing we can see in the night sky, thanks to the nearly full moon that washes out everything else. Under clear skies, you should easily be able to see Mars in the southern sky. The later it is, the lower and further west it will be. It sets just after midnight. Mars looks like a bright orange star that doesn’t twinkle.

Godspeed, Insight.

I’m Matt Pelsor. Happy Skywatching.

On Friday night, the Moon and Mars are right next to each other. And Neptune is nearby as well, but we can’t see it without a LOT of help.

On Saturday night, the mostly invisible Neptune is between the Moon and Mars to the south, and on Sunday, the gibbous moon drifts from the southeast.

Humans have observed the moon for as long as we’ve been able to look up. We’ve looked for meaning in the moon. In fact, the word “lunatic” comes from the belief dating back to the time of Aristotle, that the moon causes insanity in certain people. A belief still held by some today, but one that’s been disproven.

If you’re able, take a few minutes to observe the moon this weekend. A moon with a shadow is so much more fun to look at than a full moon in my opinion. The shadow helps accentuate textured features on the surface like craters and mountains. Grab a telescope, any telescope, and get a good look. If you don’t have a telescope, even an average pair of binoculars will show you a lot.

On Friday night, the shadow will cross the lowland craters at the moon’s south pole, including the prominent Tycho crater. That’s the big one with obvious rays of impact ejecta coming off of it.. Saturday night will also be a good night to view the south pole, but the lone Copernicus crater toward the middle of the moon will be particularly eye-catching. Sunday night the smaller but equally isolated Kepler crater will be just outside the shadow’s edge.

Now, if you’re a fan of the full moon you won’t have to wait long. We’ll be treated to a full moon on none other… than Thanksgiving night.

I’m Matt Pelsor… Happy Skywatching.

I’m Matt Pelsor… and this is your Weekend Sky Report.

Observations of the bright, open cluster known as The Pleiades have been recorded since the 17th century BC, and likely even before that. It was scientifically and spiritually significant to many ancient cultures across the globe, and continues to educate and inspire observers today.

The Pleiades is a collection of B-type stars, which are bright, hot, and blue in color. And the stars of the Pleiades are close too—around 450 light years away, which contributes to its brightness. And while you don’t need a telescope or even binoculars to appreciate the Pleiades, it certainly helps.

The Pleiades is also known as the Seven Sisters, after the seven daughters of Atlas and Pleione in Greek Mythology. Observers with good eyesight under dark skies will count seven stars in the cluster. It wasn’t until Galileo looked at the Pleiades through his telescope that dozens of other stars were discovered. Since then, further scientific observations and subsequent calculations have estimated over a thousand stars in the cluster.

To see the Pleiades for yourself, look to the eastern sky in the evening—the later it is, the higher it will be. To the naked eye under suburban skies, it could be confused as a small cloud. Under darker skies, it’ll look more like a star cluster. Once you find it, grab your binoculars or a telescope. Once you look at the Pleiades with a little help, you’ll quickly realize why this star cluster has captured the human imagination for thousands of years.

A year-round target dominates the evening sky in the fall.

I’m Matt Pelsor, and this is your Weekend Sky Report.

We all know about… the dippers. Ursa Major and Ursa Minor—the big and little dippers. We know about them because they’re out every night. But there’s another bright northern-hemisphere constellation you should know about… Swirling around the northern sky year-round are the five bright stars that make up… Cassiopeia.

Cassiopeia is popular with amateur astronomers because it’s large, bright, and the main reference point for several deep-sky objects. Things like Double Cluster, the Andromeda Galaxy, Messiers 52 and 103, both open star clusters, and the Owl Cluster, also known as the E.T. Cluster. Yes, THAT E.T. It’s called that because apparently it looks like the movie character. I don’t really see it, but I do enjoy finding it when I can.

Anyway, this weekend, you can find Cassiopeia high to the northeast after sundown. If you were to draw lines between its five bright stars, it would look kind of like a wonky lowercase “W” on its side.

Interestingly enough, if we were to take a quick trip to nearby star system Alpha Centauri, our own sun would appear in Cassiopeia. It would turn the “W” into a bit of a squiggle, and would be appear to be by far the brightest star in the constellation.

Cassiopeia has inspired novels, movies, TV shows, even songs. If we get a clear night this weekend, maybe look up for a little inspiration of your own.

I’m Matt Pelsor. Happy Skywatching.

Right now, one of the farthest planets is as bright as it can be.

I’m Matt Pelsor… and this is your Weekend Sky Report.

This past Wednesday, Uranus was at opposition… meaning the Earth was directly between it and the sun. When a planet is at opposition, it’s at its brightest for the year. Now, even at its brightest, Uranus is still fairly dim. So dim, it wasn’t discovered until the late 18th century when astronomer William Herschel saw what he first thought was a comet, but further observation proved it was indeed a planet beyond Saturn.

This weekend, you can find Uranus in the Eastern sky between the constellations Aries and Pisces with Aries to the left, and Pisces to the right. To find Uranus, trace a line between the second-brightest star in Aries, Beta Arietis (uh-RYE-uh-tiss), and the bottom or cord star in Pisces, Alpha Piscium. From the center of that imaginary line, scan to the right with your telescope. When you see a blue disc, you’ve found it.

And I would recommend going out early before the moon comes up… the moon was Full on Wednesday, so it’s still pretty big and bright enough to make finding Uranus difficult. The moon rises at 8:30 on Friday night, 9:20 on Saturday, and 10:15 on Sunday.

Uranus is a very different planet in a lot of ways. You may remember it being categorized as a gas giant. But since the 1990s when it was discovered that the composition of Uranus and Neptune was in fact VERY different from that of Jupiter and Saturn, the terminology changed. Rather than the hydrogen and helium found in gas giants, ice giants are composed primarily of methane, ammonia, and yes… good old H2O.

I’m Matt Pelsor. Happy skywatching.

Tonight, check out a celestial object that Kurt Vonnegut wrote about…

I’m Matt Pelsor, and this is your Weekend Sky Report.

The PBS list of the 100 greatest books of our time or, The Great American Read, includes a title by Indianapolis native Kurt Vonnegut. His 1959 novel, The Sirens of Titan, opens with a quote from his character Ransom K. Fern who says “Every passing hour brings the Solar System forty-three thousand miles closer to Globular Cluster M13 in Hercules—and still there are some misfits who insist there is no such thing as progress.”

A great opening… for a great book. Read it sometime. But let’s talk about Messier 13.

The Great Globular Cluster in Hercules, or M13 was discovered by astronomer Edmund Halley in 1714, and found its way into Charles Messier’s catalog of comet-like objects fifty years later. Under the right conditions… a moonless night, and very dark, clear skies, you can see the cluster with the naked eye. Most of us though will need a telescope.

To find the cluster, look high to the west after dark. The later it is, the lower and farther north it will be. There you’ll find the constellation Hercules, which can be identified by the oddly-shaped quadrilateral below the very bright star Vega.  Once you find the four stars that make up Hercules’ torso, find the one furthest to the right. Then, with your telescope, scan slowly toward the star at the bottom of the quadrilateral until you see what looks like a dim, fuzzy star. That’s M13, the Great Globular Cluster in Hercules.

When you find it, you’ll be looking over 25,000 years into the past at a cluster of 300,000 stars.

I’m Matt Pelsor. Happy Skywatching.