Weekend Sky Report

The brightest star in the constellation Perseus is Mirfak, and it’s where you need to look to find this weekend’s target.

The Alpha Persei (PER-see-EYE) Cluster is an open cluster of hot, bluish-white B-type stars. These kinds of stars are so energetic, they don’t live long. So most of the B-type stars we can see in the night sky are, on the cosmic scale, practically newborns.

In fact, by the time most of the stars of the Alpha Persei Cluster first formed, including the bright Mirfak, the dinosaurs were already extinct. Mirfak itself is less than 50-million years old, but it’s already entered old age. It’s a supergiant, having ballooned up to about 60 times the size of our sun. And it’s bright too—five THOUSAND times brighter than the sun.

To find Mirfak, and therefore the Alpha Persei Cluster, look to the northeast. You can find Perseus beneath Cassiopeia in the northeastern sky. The later it is, the higher it will be, but if you miss it this weekend, don’t worry. It will be to the northeast in the evening through early winter.

Under dark skies, you can see the cluster with the naked eye, but if you’re near the city, or if the moon is out, you’ll need some help. A small telescope or even a pair of binoculars should provide enough magnification to notice a loose cluster of bright blue stars around Mirfak. That’s the Alpha Persei star cluster.

The prominence of the constellation Perseus in the evening sky is a sure sign of autumn. It means you’ll be able to observe WITHOUT the help of bug spray… very soon.

Hiding in the constellation Cassiopeia… is a star cluster that goes by many names. Its most official name is NGC 457 for its place in Danish astronomer John Lewis Emil Dreyer’s New General Catalogue, a list of over 7,000 deep sky objects compiled in the late 19th century. But most people know it… as the Owl Cluster.

The Owl Cluster is an open star cluster, which is a group of stars that all formed around the same time in the same place, and are still bound together, though loosely, by their own collective gravity. The stars in the Owl Cluster are fairly young--all around 21 million years old. The ice caps on Antarctica have been around longer than these stars.

As you can probably guess from the name, the Owl Cluster resembles… an owl--when oriented a certain way. And you can see the Owl Cluster with almost any telescope… even cheap toy telescopes. Here’s how to find it. First, find Cassiopeia. Five bright stars that make a kind of funny sideways “W” in the north northeastern evening sky. Find the second star from the bottom, then look just above it with a telescope and slowly scan to the right. When you see a rich cluster of stars and those two unmistakable eyes… you’ve found it.

And when you see it, you’ll be looking at a cluster of stars more than 7,000 light years away… which means the light you’re seeing left those stars about a thousand years before the dawn of civilization.

On Friday night, the moon rises just before 6pm, so by dark it will be high to the south/southeast. If you look at the moon on Friday night, you’ll probably notice a bright point of light above it. That’s Jupiter. Grab a pair of binoculars or a telescope and have a look at the moon to admire some of its features. Look toward the shadow--what’s called the terminator, for details on craters and mountains, and then scan to Jupiter to see its four largest moons--the ones Galileo discovered when he first looked at Jupiter through one of the earliest telescopes. If you have a larger telescope, you may want to observe Jupiter on Saturday night after sundown when the Great Red Spot will be in view. Now these days, the Great Red Spot is more of a pale orange, but you can still make it out through decent telescopes with good magnification.

And by the way, on Saturday night, the moon will have moved East of not only Jupiter, but also Saturn in the night sky. Saturn is that pale yellow point of light just to the left of Jupiter. On Saturday night it will be just above and to the right of the Moon. Saturn’s another great target for smaller telescopes and good binoculars. The rings of Saturn are an incredible sight from your backyard. Looking at the Moon on Saturday though, you’ll notice one of the brightest features on the lunar surface right near the edge of the lunar terminator--the Aristarchus crater. A deep crater in the Northern hemisphere. Just follow the shadow until you see it.

The moon isn’t full yet--that’s not until Tuesday, but it’ll look pretty close on Sunday night. It’ll rise to the southeast around 7:30 on Sunday and be due south around Midnight.

So if we’re lucky enough to have clear or clear-ish skies, enjoy these bright targets.

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.

The Perseid Meteor Shower is great not only because it falls among the warmest nights of the year, so you don’t really have to bundle up to see it. But also because it’s one of the most frequent showers, producing up to 110 meteors per hour at its peak. That’s a meteor almost every thirty seconds.

Now, chances are you’ve seen a bright meteor streak the sky at some point in your life… and you’ll see a few of those this weekend, but most will be fast, and dim, so it’s important to find dark skies if you want to see the most meteors.

Now there’s one thing that can really ruin a meteor shower no matter how far out in the country you go to watch it… the moon. If the moon is out, its brightness will wash out the dimmer, more frequent meteors. Luckily, the moon doesn’t rise until around 3:30am on Saturday morning, and it won’t be up until after 4am Sunday morning.

They’re called the Perseids because they appear to emanate from the constellation Perseus, but you don’t really have to know where that is to know where to look. Here’s a good rule to follow. Just look to the northeast. That’s pretty much all you need to know. The earlier you’re out, the lower to the horizon the meteors will be, but the northeastern sky is the general target.

When you watch the meteors this weekend, you’ll be watching tiny particles—most of them smaller than a grain of sand, as they streak through the atmosphere and burn up… for our viewing pleasure. Dusty remnants of a comet called Swift Tuttle, which comes around about once every 133 years. Oh, as always, don’t forget the bug spray.

The weather doesn’t look great this weekend, but if we’re lucky enough to have clear or clear-ish skies, look the southeast after sundown… so around 9:30.

You’ll see that the moon dominates the evening sky this weekend. It’s a waxing gibbous moon, which means it’s on its way to being a full moon, which happens Monday.

When you look at the moon tonight, you’ll notice a bright point of light nearby. That’s Jupiter.

On Friday night, Jupiter will be below and to the left of the moon. Saturday, the moon sits between Jupiter and Saturn, which will look like a dim yellow star to the left of the moon. Sunday, the moon moves past both planets and closer to the horizon in the evening.

All three of these targets are great for observing with a telescope. Just about any telescope will allow you to point out certain features on the moon… and because there’s still a bit of a shadow covering part of the moon, you might notice really fine details on craters and mountains.

And speaking of moons… scan over to Jupiter with your telescope to see the four Galilean moons that orbit the giant planet.

They’re called Galilean moons because when 17th Century astronomer Galileo Galilei first observed Jupiter with his telescope, he noticed what he first thought were stationary stars. But when some would disappear in front of, or behind the planet, he concluded that they were orbiting Jupiter.

Ganymede, Io, Callisto, and Europa are the largest of Jupiter’s nearly 70 natural satellites. And you can see them this weekend… even with just a toy telescope.

And of course, seeing the rings of Saturn from your backyard is enough to hook anyone on astronomy. (Most telescopes, including that old one of yours will give you a pretty good look at that too.)

There’s a lot in the sky this weekend for anyone with binoculars or a cheap telescope. For one thing, the crescent moon will rise higher in the southwestern sky with each passing day until it reaches its first quarter phase on Sunday evening. A quarter moon--what some call a half moon--is one of the best phases to view through a telescope because the shadow, or lunar terminator, appears to move the fastest across the moon’s surface during this phase. So fast that you can sometimes actually see surface detail like craters and mountains illuminate in real time if you watch long enough.

But the object everyone’s talking about is Comet NEOWISE. To find it, imagine the Big dipper is horizontal with the cup to the right. Then imagine another cup underneath that one to get the spacing right. Scan underneath that imaginary Big Dipper cup slowly with binoculars. When you see a dim, fuzzy, blueish light, you’ve found it.

If you’re up for more after looking at the Moon and Comet NEOWISE, turn to the southeast for two bright planets--Jupiter and Saturn.

Jupiter is the brightest object in the sky behind the moon, so you should have no trouble finding it. Through decent binoculars, you may be able to see Jupiter’s four largest moons. If you have a larger telescope with lots of magnification, you may be able to see Jupiter’s Great Red Spot On Sunday night around 11pm when it will be in the center, facing Earth.

A little to the left, or East in the sky is a pale yellow dot that doesn’t twinkle. That’s Saturn. Most telescopes should reveal the planet’s famous rings.

Suffice to say there’s plenty to see this weekend, but don’t forget the bug spray.

If you have dark skies, you can see Comet Neowise with the naked eye, but urban and most suburban observers will probably need some help spotting it.

The largest planet in our solar system is clearly visible late at night. It rises to the southeast just after sunset, and it’s highest right around 2am, so if you’re up late, go out and look. By the way, most decent binoculars and almost any telescope--even a toy telescope should show you the four Galilean Moons, Ganymede, Io, Callisto, and Europa. They’re the four largest of Jupiter’s 70+ natural satellites, and Ganymede is the most massive moon in the entire solar system. The moons will look like four stars flanking the planet on either side, though you may not see all of them.

Jupiter is very bright right now, but it will technically be at its brightest this coming Tuesday when it’s at opposition, meaning the Earth is directly between Jupiter and the Sun. Now, that said, you probably won’t notice any difference between observing Jupiter tonight versus Tuesday night. But if you do look at Jupiter on Tuesday night, you might see one of its most famous features… the Great Red Spot.

Jupiter spins faster than any other planet. It completes a rotation every 10 hours. Because the Great Red Spot is a single feature on the planet, you have to go out at just the right time to see it. Lucky for us, 11pm eastern time Tuesday night will give us that opportunity. At that time, the Great Red Spot will be dead center. And while it may be called the Great Red Spot, it's more of a pale orange these days, so it’s hard to contrast against the whites and browns of the cloud belts unless you know where to look. And don’t get frustrated if you don’t see it. You need good observing conditions and a decent telescope with lots of magnification to get a good enough view.

But if you see it, you’ll be looking at a hurricane the size of Earth that, for all we know, has been raging for more than 300 years.

If you get a chance to look up at the moon this weekend, you may wonder what you’re looking at. Where did the Apollo missions land? What’s that big crater called?

Looking at the moon with the naked eye, you’ll notice a few big features. The so-called “seas,” the large ‘Ocean of Storms’ to the west, Even the Tycho crater to the south.

But look closer with a telescope—even a pair of binoculars, and the moon REALLY reveals itself.

You’ve heard of the Sea of Tranquility. That’s the dark area to the northeast as you’re facing the moon. If you’re ON the moon, it’s the northwest, but we’re not, so let’s stick with our own perspective. The sea of Tranquility is a sort of figure-8-shaped dark patch surrounded by other circular and oval-shaped dark patches—also known as seas. The sea of serenity to the northwest, the sea of fertility to the southeast, the smaller Sea of Nectar due south, and the sea of Crises to the east. I love the names.

The seas on the moon are actually volcanic plains made of basalt. The Sea of Tranquility is significant because it’s where the Neil Armstrong and Buzz Aldrin landed on the first manned mission to the moon. The Apollo 11 landing site is at the southwest edge of the Sea of Tranquility. Now, you won’t be able to see any evidence of the landing with a personal telescope, but large professional land-based and space-based telescopes can spot the leftover hardware, and you can find those images with a simple internet search.

Scan west to the Ocean of Storms and you’ll see two prominent craters named after 16th century astronomers. Kepler and Copernicus. Both are all by themselves in the Ocean of Storms. The larger Copernicus is east of Kepler.