Weekend Sky Report

The moon won’t officially be full until early morning Saturday, but by most definitions, tonight will be a full moon. It’s also Friday the 13th. This coincidence hasn’t happened since 2006, and won’t happen again for ANOTHER 13 years.

But aside from arbitrary dates curiously aligning with the lunar cycle, there’s something else at work. Since the Moon has an elliptical orbit, there’s a point every month when the moon is at its closest, perigee… and when it’s at its farthest, apogee. The two points vary by several thousand miles, but the moon’s appearance in our sky doesn’t seem to change much to a casual observer. That said, this weekend’s moon has been dubbed by some as a micromoon because it’s a full moon at apogee. The opposite, a full moon at perigee, has been called a supermoon. But again, the difference between a supermoon and a micromoon is pretty hard to notice. A supermoon appears about 14% larger than a micromoon, and about 30% brighter. And just like the Friday the 13th coincidence, this is a chance aligning of the lunar apogee with the full moon phase--two things that happen every month--just not always at the same time.

The best time to view a full moon is at moonrise, which tonight is just before 9pm. That’s because the moon seems to appear so much larger when viewed against objects in the foreground. We know, however, that the size of the moon in the sky at moonrise or moonset is the exact same as when it’s at its highest--it’s just an optical illusion.

So enjoy the full moon tonight. Pet a black cat, and walk under as many ladders as you like.

If you’ve heard this show and have had difficulty locating some of the targets, you’re not alone. Finding them takes practice. But anyone can find the moon. And before you go back to work on Monday, you might find some inspiration… by viewing Saturn through a telescope.

You see, on Sunday night, Saturn will be right next to the moon. That way you won’t have to triangulate or wait for a certain time of night… you can just look for the moon, then look to the right. That bright yellow point of light that doesn’t twinkle is Saturn. And you can observe Saturn from almost anywhere--even in the city. Almost any telescope will show the planet’s famous rings. Obviously the better the telescope, the better the view, but… even some toy telescopes might at least show you that this is no ordinary star. Through a small telescope, the rings may appear as two bright bulges on either side of a yellow disk. Through a slightly better telescope, the image is unmistakable, and you may even see its largest moon, Titan. Through a good telescope, you can see other, fainter moons, and what’s called the Cassini division--a space between the two most visible rings, named for Giovanni Cassini, the 17th Century Italian astronomer who first discovered it. Also of course the namesake for the famous NASA spacecraft that studied the planet.

Many people aren’t even aware that the rings of Saturn are visible from Earth--much less from our own backyards with simple consumer telescopes. And one good look at Saturn’s rings is enough to hook almost anyone on astronomy.

So on Sunday night… find the moon… then look to the right to find the jewel of the Solar System.

Tonight's target has been known since LONG before the telescope was invented. This of course means it can be seen WITHOUT a telescope, but ONLY under very dark skies. And it wasn't until the early 1800s that, THANKS to the telescope, it was identified as two separate clusters instead of one.

The aptly named Double Cluster is a favorite among budding amateur astronomers. Not only because its brightness makes it easy to find, but also because its beauty keeps observers coming back.

And here in the Northern Hemisphere, Double Cluster never dips below the horizon... so depending on your view, it's out all night!

To find Double Cluster, look for Cassiopeia. You'll find it in the northeastern sky in the evening. The later you're out, the higher it will be... Cassiopeia looks like an elongated, oddly-proportioned "W." Once you find it, look for the two stars closest together in the constellation. If the "W" were on its side, as it will be tonight, it's the second and third stars from the bottom. Trace a line between those two stars, then scan down with binoculars or a telescope... following that same line. When you see a double cluster of stars, guess what... you've found it. Two brilliant clusters of mostly bluish white stars-but there are a few bright yellow and orange stars for variety.

When you find it, you'll be looking at one of the younger star clusters you can easily find in the night sky... at only about 13 million years old. To give you an idea, Kangaroos evolved on Earth about two million years BEFORE these stars formed.

Hiding in the northeastern sky this evening (August 23, 2019) is one of the most distant objects visible to the naked eye.  That is… if you’re under very dark skies, which are hard to find anywhere near the city. But you can see it under most suburban skies with just about any telescope, or even decent binoculars.

The Andromeda Galaxy lies two-and-a-half million light years from our own galaxy, the Milky Way. But it’s so big that it fills a space in our night sky bigger than the full moon. It’s just too dim to see without a little help.

Here’s how to find it. First, find Cassiopeia. You’ll recognize it as five stars that make a wonky sideways “W” in the northeastern evening sky. Then, identify its three brightest stars. They make a nearly right triangle at the top of the constellation. From there, find its brightest star, Shedar. It’s the point at the widest angle. Treat that star like the point of an arrow and follow across the sky to Alpheratz--the brightest star in the constellation Andromeda. Imagine a line connecting those two stars. Then find the center and scan down and to the right with binoculars or a telescope. Once you see what looks like dim cloud of light, you’ve found it.

And when you do, you’ll not only be seeing light that’s taken two-and-a-half million years to get here… You’ll also be looking at the core of a galaxy that’s more than twice the size of our own, measuring in at around a trillion stars.

Rho Cassiopeiae (row casio-pee-eye) is huge. More than 400 times the size of the sun and 40 times as massive. And did I mention it’s bright? Half a million times brighter. Now it’s by no means the MOST luminous star we’ve ever found, but it is one of the brightest yellow stars. Yellow stars, or Class-G stars are fairly common. Our own sun is a Class G. But Rho Cassiopeiae is a yellow hypergiant--a particularly rare and short-lived type of class-G star. They’re thought to be a type of star that evolves from a red supergiant to a hotter blue star. A strange evolution indeed in the celestial world. So even though we’ve known about this particular star for centuries, this huge, bright, yellow stage in its evolution is relatively brief. Strangely massive stars like this have short lives. Rho Cassiopeiae is probably no more than 6 million years old.

To find it, find Caph--the second-brightest star in Cassiopeia. It’s also the highest star in the constellation in our current evening sky--and the one furthest to the right if you were to turn Cassiopeia on its side so it looks like a W. From Caph, scan to the right and up with a telescope or a decent set of binoculars until you see a yellow star. Consult a star chart to make sure you have the right one.

Of the hundreds of billions of stars in the Milky Way, we’ve only found a dozen yellow hypergiants like Rho Cassiopeiae. So if you see it, you’ll be looking at one of the rarest star types we’ve ever discovered.

Here in the northern hemisphere, we’re lucky to have a bright pole star. There is a star that marks the south pole, but it’s so dim that it’s barely visible to the naked eye even under dark skies.

Polaris or, the North Star, is the brightest star in Ursa Minor, the little dipper. Nitpicky observers will note that it’s not perfectly centered with the north pole, but almost everyone would agree it’s close enough.

Polaris is a great navigational star for obvious reasons. Escaped slaves using the Underground Railroad would travel under the darkness of night and use Polaris as their guide north. The folk song “Follow The Drinkin’ Gourd” references the legend of using the big dipper to point to the north star on the way to freedom.

Polaris is actually a system of three stars. The Polaris we can easily see, Polaris Aa is a big star. A yellow supergiant more than five times as massive as our sun, and more than 35 times larger. Its orbital companion, Polaris Ab is about the same size as our sun, and its more distant companion, Polaris B is about 40% larger. 

To find Polaris… just look north! Or, find the big dipper and use the two stars at the end of the cup to draw a straight line up. The bright star that line connects with is Polaris. You can confirm it by then looking for the little dipper. Polaris marks the end of the Little Dipper’s handle.

Polaris hasn’t always been the north star, nor will it keep that designation. The next star in line is Gamma Cephei (SEE-fee-eye), the tip of the constellation Cepheus. But that won’t happen for another 22-hundred years.

So maybe you got a small telescope and got bored with just looking at the moon and planets. Or maybe you’ve had one for a while, but don’t know what to look at? Believe it or not, even small telescopes can resolve a number of larger and brighter deep sky objects. Some of the best are globular clusters. Dense concentrations of thousands of stars bound by their own collective gravity. They’re almost like miniature satellite galaxies that form in the outer regions of their host galaxy. One of the largest, at least as it appears in our sky, is the globular cluster known as Messier 4.

Like most globulars, this one is ancient—even on the celestial scale. It began forming around 12 billion years ago. And like I said, it’s big in our sky. Almost as big as the full moon, but since it’s very dim, you need a telescope to see it.

To find it, look south to find Antares. It’s that bright orange star beneath and to the right of Jupiter, the brightest point of light in the night sky. When you find Antares, scan down and to the right. Once you see a fuzzy ball of light, you’ve found it. And just a reminder, that’s really all it will look like… a fuzzy ball of light. And it’s not as dense as many other globular clusters, so you may pass right by it and not notice it. Relax, move slowly, and don’t expect to be blown away visually. Just know that when you see Messier 4, you’ll be looking at tens of thousands of stars slowly collected over billions of years.

Jupiter is the brightest point of light in the evening sky this weekend. Above it is the constellation Ophiuchus. Greek for “serpent-bearer.”

With today’s light pollution, it is one of the dimmer constellations, which may explain why you may have never heard of it. That, and its challenging name. But Ophiuchus is a great constellation to use when hunting for deep sky objects, or DSOs—what I like to call “dim fuzzies.”

The most popular dim fuzzies are the Messier objects, after 18th century French astronomer Charles Messier. Distant objects like galaxies, globular clusters, nebulae… Messier catalogued all these objects because he was a comet hunter, and whenever he found a dim target, he’d check his charts, realize it was a stationary object, and get frustrated he hadn’t found a new comet. What he didn’t know was that his name would be forever tied to some of the most extraordinary objects in the universe.

Ophiuchus is home to seven messier objects—all globular clusters, which are among the oldest structures in the universe. Spherical gatherings of stars, bound by gravity, and collected over eons. You need a telescope to see one, and a good place to start is M9, near Sabik, one of the brighter stars in Ophiuchus that represents his right knee. It’s the one immediately above Jupiter in the sky. Find Sabik, then scan down and to the left. When you find what looks like a fuzzy, out-of-focus star, you’ve found it. M9 is a dense cluster, so you can see it with a small telescope.

When you see it, you’ll be looking at a cluster of stars that’s been around for 12 billion years.

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 has been in the evening sky since early June. And now Saturn is out early enough to enjoy too. This means two great targets for any size telescope… or the naked eye.

Let’s start with the easiest one. Jupiter is high, bright, and due south at 11pm. 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 Sunday evening just after sundown 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 transformative experience. Seeing details of an object more than a billion kilometers away is enough to hook almost anyone on astronomy.

So stay cool, but brave the nighttime heat to see two of the best summer targets. And don’t forget the bug spray.

There’s a story in Greek mythology about Orion the hunter bragging to the goddess Artemis that he would kill every animal on Earth. Artemis then decided Orion’s ego had to be curbed, so she summoned a scorpion to battle Orion. The battle was so epic that it caught the attention of Zeus. In the end, the scorpion killed Orion. Zeus was so entertained by the fight that he raised the scorpion to the heavens to commend its victory. Then he raised Orion as a cautionary tale to all those who might be a little too braggadocios.

The victor of that fight creeps along the southern sky on summer nights.

Scorpius… is easy to spot… just look for its brightest star, Antares, which some call the heart of Scorpius.

Bright orange Antares is classified as a red supergiant. It’s so big that if you were to place it at the center of our solar system, its surface would reach beyond the orbit of MARS.

And speaking of Mars, Antares’ name essentially means “rival of Mars” Ant-ares, Ares of course being the greek god of war… but the planets are named after Roman gods… the Roman god of war is of course Mars.

And it’s the rival of Mars for good reason… it’s bright like Mars, and it’s ORANGE like Mars.

To find Antares, look south after sundown. That bright orange star is Antares, and the spray of stars above and to the right symbolizes the scorpion’s head and pincers. Curling below and to the left of Antares are the stars that make up the scorpion’s tail.

In the winter, Orion hunts… but in the summer, he retreats from his former rival… Scorpius.