Weekend Sky Report

If you’re lucky, you’re spending your days… and nights in the AC. But if you have a good view of the southern sky, step outside for a few minutes and find the two largest planets in the solar system.

Jupiter and Saturn will be low to the southeast around 11:30. The later it is, the higher they’ll be. They’re right next to each other too, so if you find one, you can find the other.

Let’s start with the easiest one--Jupiter. It’s hard to miss since it’s the brightest object in the night sky behind the moon. Once you find Jupiter, grab a telescope. Almost any telescope should show you its Galilean moons, Io, Callisto, Ganymede, and Europa. They’ll look like three or four points of light in an almost straight line around the planet. Larger telescopes can resolve even the cloud belts of Jupiter. And if you’re lucky enough, even the Great Red Spot. Your best chance at seeing that will be late Saturday evening just before midnight when the Great Red Spot is dead-center, facing the Earth.

Scanning down and left, or east with the naked eye, you’ll notice a bright yellowish point of light that doesn’t twinkle. That’s Saturn. Most telescopes—even small ones, will show the rings. Larger amateur telescopes can resolve as many as seven moons around Saturn, as well as the Cassini Division—the split between its two most visible rings.

Observing the rings of Saturn from your own backyard can be a transformative experience. Seeing details of an object more than a billion kilometers away is enough to hook almost anyone on astronomy.

So step into the nighttime heat to see two of the best summer targets. And don’t forget the bug spray.

The stars Vega, Deneb, and Altair form what’s called the summer triangle, which sweeps overhead all night during the warmer months of the northern hemisphere.

Of the three, you’ve probably at least heard of Vega… one of the brightest stars in the night sky. It’s about 2.5 times the size of the sun, twice as massive, and about 40 times brighter. That may sound like it has quite a leg up on the sun, but if you take into account the enormous range in characteristics of stars out there, they’re fairly similar.

Altair is even MORE like the sun. Just under twice the size and mass, and 10 times brighter. Closer than Vega too at less than 17 light years away.

But the REAL star of the summer triangle, if you’ll pardon my unintended pun… is Deneb.

Deneb is an incredible star. It’s a blue-white supergiant. If you were to replace the sun with Deneb, its surface would extend to about Earth’s orbit—we’d be toast. It’s one of the largest known white stars. And, get this, it’s almost 200,000 times brighter. But enormous, energetic stars like this don’t live long. Deneb is only about 10 million years old.

Despite all of that, Deneb is the dimmest of the three stars in the summer triangle. Why? You can probably figure it out. It’s SO far away. About 2600 light years.

The Summer Triangle will be in the eastern sky after sundown. Vega and Deneb form the short side of the triangle with Altair at the point, closest to the horizon.

Ophiuchus was one of the original 48 constellations listed by the second century Greek astronomer Ptolemy. At this time of year, it’s on its side, rising in the east and sweeping across the southern sky. Of course, the sun sets so late this time of year, Ophiuchus is fairly high in the sky by the time it’s dark.

A good time to see it is around 10:30. Look to the east for its brightest star, Rasalhague (RASS-ul-hayg). But don’t confuse it with Vega--the REALLY bright star to the east. Rasalhague is across the sky to the right of Vega. The second brightest star in Ophiuchus is Sabik (SAY-bik). You can find it lower to the southeast.

You can use those two stars to find two deep sky objects. First, find Sabik. Again, it’s a bright white star to the southeast. Above Sabik is Zeta Ophiuchi, the third brightest star in the constellation. If you were to draw a line between Zeta Ophiuchi and the bright star Rasalhague, the line would fall between globular clusters Messier 10 and Messier 12. To see them, you’ll need a telescope. Most cheaper telescopes should at least give you an idea.

Globular clusters are tightly-packed clusters of thousands of stars that form above the galactic plane. That’s how they’re able to clump together so closely--there’s less gravitational influence from the outside. But, they take billions of years to form. The two globulars inside Ophiuchus are over 11 billion years old. Just a couple billion years younger than the universe itself.

There are many deep sky objects around Ophiuchus, but M10 and M12 are the brightest. Given a decent telescope and extra time, you’ll find more.

The Strawberry Moon was officially full this afternoon when it was on the other side of the planet, but it’ll still look pretty “sweet” all weekend.

It’s called the Strawberry Moon because June is the month when strawberries are ripe for the picking in much of the US. It’s also why we usually see so many strawberry festivals this time of year, but we’ll have to wait until next year for those to come back.

The Strawberry Moon will rise to the southeast on Friday night just before 10pm. When the full moon is low on the horizon, it can sometimes assume a color like yellow or even orange, depending on atmospheric conditions. It can even look bigger. As the moon rises higher and higher, it often loses that color and appears brighter, though smaller. It may seem like the moon is shrinking, but it’s actually an optical illusion. The moon is no bigger when it’s low than when it’s directly overhead. When the moon is closer to the horizon, we have foreground objects to compare it to, so it can seem much bigger. And let’s be honest, it does make for better photos.

Of course, you can celebrate the strawberry moon from your own home with binoculars or a telescope. The full moon is a striking sight through the eyepiece, but many of the moon’s best details are washed out when it’s fully illuminated. But one feature you’ll notice if you look closely at tonight’s full moon is the Tycho crater. It’s the big, deep crater to the south with what looks like spikes coming off of it. That’s ejecta from the impact that created it over 100 million years ago. Apollo 17 astronauts collected some of it for analysis, which is part of how we can estimate its age.

So take some time to appreciate the Strawberry Moon this weekend. With or without shortcake.

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.

The Virgo Cluster is a cluster of galaxies that appear between the constellations Virgo and Coma Berenices. It actually consists of over a thousand galaxies, but most of them are far too dim for even the biggest amateur telescopes. Some of them, however, can be seen with a modest backyard telescope if you have dark enough skies.

Now, most of the time I only recommend objects you can see with binoculars or toy telescopes--things most people have. But galaxies require a little more aperture. You’ll need at least a four inch reflector to see these targets, but of course, the bigger the better.

The brightest galaxies in the Virgo Cluster are the Messier objects. There are sixteen of them--named for 18th century French astronomer Charles Messier’s catalog of what he thought were stationary comet-like objects, but we now know they’re things like galaxies, globular clusters, open clusters, and nebulae. The four brightest are M49, M60, M87, also known as Virgo A, and M86, the brightest galaxy in Markarian’s Chain, which is a curved line of eight galaxies named after 20th century Armenian astronomer Benjamin Markarian, who discovered that all of the galaxies in the chain are moving in the same direction.

If you see even one of these galaxies, you’ll be looking at light that’s taken over 50 million years to arrive.

Obviously, you don’t need to know constellations to tell what season you’re in, but there are big astronomical markers. In the colder months. The Winter Triangle sweeps across the sky to the south... a nearly perfect equilateral triangle of some of the brightest evening stars--including the brightest star in the sky, Sirius.

But right now, Sirius is extremely low to the southwest after sunset, and Betelgeuse, also part of the Winter Triangle isn’t too far above it. Only Procyon, part of the constellation Canis Minor--the smaller of Orion the Hunter’s two dogs, stays prominent after dark, and by midnight, even it is below the horizon.

Now for the summer tease... To the northeast, the fifth brightest star in the night sky is on its way up. Vega is part of the constellation Lyra, and it’s the first star to rise in the so-called Summer triangle which also consists of the stars Deneb and Altair.

Vega has been dubbed “arguably the next most important star in the sky after the Sun. It was the first star to be photographed, other than the sun. It was the first star to have its spectrum recorded, which we now know can reveal all kinds of information like a star’s temperature, mass, and chemical composition. Vega is also often used to calibrate instruments that measure stellar brightness.

So if we’re lucky enough to have clear skies this weekend, spend some time appreciating the fact that winter is long gone, and summer is right around the corner.

We’re halfway through Spring. A perfect time to look for what some call the “Great Diamond.”

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

Sweeping high across the southern sky in the spring are the constellations Leo, Virgo, and Bootes (boh-OH-teez). But if you don’t know those constellations, that’s okay. We’re looking for something bigger.

The Great Diamond is made up of four bright stars, Arcturus in Bootes, Spica in Virgo, Denebola in Leo, and the star Cor Caroli from the small constellation Canes Venatici (CANE-eez vin-AT-uh-sigh). The Great Diamond actually takes up more of the sky than even the Big Dipper. And you can use the Big Dipper to find it.

There’s an old mnemonic device to help you find the two brightest stars, Arcturus and Spica. Using the handle of the Big Dipper, follow the arc of the handle to Arcturus, and then spike across the sky on that same trajectory to the bright star Spica. Arc to Arcturus, and spike to Spica. Then look up and to the right of those two stars to form an almost equilateral triangle with Denebola in the constellation Leo. It’s the second brightest star in Leo behind Regulus. Then, complete the Great Diamond with Cor Caroli above those three--it’s the highest star in the Great Diamond, and if you’re observing around 11:30, it’s practically straight up.

And if you have a telescope, get it out and look at Cor Caroli. Careful observers will notice two stars--it’s a binary.

And if you have a big telescope, you probably already know about the Virgo Cluster, which sits right near the middle of the Great Diamond and consists of over a thousand known galaxies--most of which are too faint for amateur telescopes, but some are bright enough for backyard viewers with lots of aperture.

I’m Matt Pelsor… Happy Skywatching.

When the moon is out, it’s hard to see dimmer stars and deep sky objects. But there’s still plenty to appreciate about our natural satellite.

For one thing, it’s the easiest object to observe. Even a cheap pair of binoculars or a toy telescope will give you a good look at the moon’s details. And since there’s still a terminator, or shadow, crossing the moon; you can see something different every night. The terminator can accentuate textured features like craters and mountains, whereas the more sunlit areas of the moon can get washed out, making those details harder to see.

On Friday night (May 1, 2020), the terminator reveals one of the moon’s largest craters--Clavius (CLAY-vee-us). Named for the 16th-century German astronomer Christopher Clavius, who modified the original Gregorian Calendar. A change that is still considered accurate and in-use today. You’ll find it near the moon’s south pole. Friday night is also a good night for the Copernicus crater, which sits all alone at the edge of the Ocean of Storms. Look for it near the center of your view, right on the shadow.

Saturday night (May 2, 2020), the terminator reaches the edge of the large Sea of Rains in the northern Hemisphere, which is bordered by high mountain ranges and features the large Plato crater at its northern edge.

On Sunday night (May 3, 2020), the terminator falls on the small, but deep crater named Kepler near the equator, and the large Gassendi (GAS-end-ee) crater to the south, named for the 17th century French astronomer Pierre Gassendi, who estimated the moon’s diameter, and was the first known person to observe the transit of a planet across the sun.

So take a moment to appreciate our moon this weekend, and all the astronomers who helped us understand it.

Messier 3 is a remarkable globular cluster. It’s over 33,000 light years away, but it’s bright enough to see with a small telescope, which means it’s dense. Around half a million stars exist there. It’s considered by some to be the most beautiful of its kind. But what is a globular cluster?

Globular comes from the Latin globulus, meaning “small sphere.” Small they are not… this one is an estimated 90 light years across. But compared to open clusters, they do seem smaller. Globulars are like open clusters in that they’re a group of nearby stars bound together by gravity, but they form above the galactic plane, or at the outer edge of the galaxy where their collective gravity can hold it together tightly away from the influence of passing bodies, whereas open clusters form further in where the gravity from other stars can disrupt its shape. For this reason, it takes a long time for globular clusters to form.

To find Messier 3, first find bright orange Arcturus. It’ll be in the eastern sky before midnight. One way to find Arcturus is to follow the curve of the handle of the big dipper… arc to Arcturus. Once you’ve found Arcturus, look for a dimmer white star called Cor Caroli (kor CARE-uh-lie). If you’re observing in the evening, it’s above and to the left of Arcturus, next to the handle of the big dipper. Trace a line between Arcturus and Cor Caroli. Point your telescope to the middle of that line and scan slightly downward toward Arcturus until you see what looks like a dim, fuzzy star. That’s Messier 3.

When you find it, you’ll be looking at a globular cluster that’s an estimated 8 billion years old. More than half the age of the universe itself.