Weekend Sky Report

In 1861, Comet Thatcher appeared in the night sky, as it does about every 400 years. When it passed through, it left behind tiny pieces in its orbit as the comet was cooked on its way around the sun. Every April, the Earth passes through this orbit, and as the pieces get pulled in by the earth’s gravity, they burn up and give us a show we call… the Lyrid Meteor Shower.

The Lyrids are active all weekend, so you may see some tonight under dark skies, but the big peak comes early this coming Wednesday morning. This year we’re expecting 10 to 15 meteors per hour. For a meteor shower, this one’s in the middle. The Perseids in August and the Geminids in December have more frequent meteors, and there are many other showers throughout the year that have fewer.

If you ask me, all of them are worth a look… but some are better than others.

If you do check them out, you’ll need to know where to look. Luckily, this shower emanates near one of the brightest stars in the night sky. Vega is part of the constellation Lyra the lyre, from which the lyrids take their name. Vega rises in the northeast around 10pm. Early Wednesday morning when the lyrids are peaking, you’ll find Vega HIGH in the eastern sky.

To target the exact spot in the sky where you’ll see the most meteors, find Vega and hold a clenched fist out at arms length. With Vega to the left of your fist, look at the spot in the sky to the right of your fist.

If you watch this coming week, you’ll be seeing a meteor shower that observers in ancient China recorded over 2600 years ago.

In greek mythology, twins Castor and Pollux were the sons of Leda, a Spartan queen. They were fathered by different men though… Castor’s father was Tyndareus, Leda’s husband, king of Sparta. Pollux is the result of Zeus seducing Leda. So Pollux is immortal, while Castor is not. When Castor died, his brother begged Zeus to make him immortal. So he did by placing them together among the stars, creating the constellation we call… Gemini.

In the constellation, the heads of Castor and Pollux are named as such. And in reality, Castor and Pollux are of course light-years away from each other. The brighter Pollux is the closest giant-stage star to the sun, and orbiting it is one of the first known exoplanets. An enormous planet more than twice the mass of Jupiter which causes the star to wobble, which is how it was discovered in 2006. And Castor isn’t one star, but a remarkable SIX stars appearing as one.

To find Gemini, look to the west and find the familiar Orion. You’ll know it by its iconic “Belt” of three bright stars in a row. Then, simply look above Orion for two bright stars next to each other. The brighter one on the left is Pollux… it has a slightly orange hue to it. The dimmer one on the right is Castor. The rest of the constellation is dimmer and forms two stick figures below the two main stars.

Gemini will visible in the Western sky in the evening through early June.

As Venus continues its rise in the evening sky through the end of this month, it will travel through many constellations. Tonight, Friday, April 3rd, it will be in the middle of the Pleiades star cluster. The brightest of all the open star clusters. Of course, Venus will outshine the Pleiades by far, so the best way to see the planet AND the star cluster together is to use binoculars or a telescope. After dark, look high to the west. You’ll see a bright point of light that almost looks bright enough to be an airplane, but it doesn’t appear to move. That’s Venus. Look at it under dark skies, and you may see the Pleiades behind it, but use binoculars or a telescope for a better view.

If you do use a telescope, you may notice that Venus appears crescent-shaped. Because it’s between the Sun and the Earth, we can only see the hemisphere that’s illuminated by the sun. As we move further into April, and on into May, the part of Venus we can see will continue to get smaller until late May when it disappears in the glare of the later evening sun.

Of course, the star cluster it’s joining tonight is plenty to appreciate as well. Six or seven stars visible to the naked eye becomes over a hundred when viewed through a telescope. The stars of the Pleiades are hot, which we can tell by their bluish hue. They’re very young too--just about 100 million years old. A mere moment in the cosmic timeline.

So tonight, look west for the brightest planet in the sky as it moves through the most famous star cluster of all time.

If we’re lucky enough to get clear skies in the early morning--before 7am Eastern, look to the south and you’ll see three bright points of light. From left-to-right, it’s Saturn, Mars, and Jupiter. Saturn of course is easily the most spectacular when viewed through a telescope. Any telescope will show you the planet’s rings. If you have a small telescope, you may have to give your eyes a moment to adjust. But if you don’t have a telescope, look at Jupiter with a pair of binoculars to see the four Galilean moons Ganymede, Callisto, Io, and Europa. You’ll see them flanking the giant planet on either side. They’ll look like little stars all lined up. They’re called the Galilean Moons because Galileo discovered them when he first looked at Jupiter through what would now be considered a pretty rudimentary telescope. That explains why most modern binoculars will show you the same thing.

If you miss it this weekend, that’s okay. But if skies are clear on Tuesday morning (March 31, 2020), you won’t want to miss the show. That’s when Saturn and Mars will be right next to each other--what’s often called a conjunction, but more technically this event is called an ‘appulse.’ An appulse is a looser term for two celestial objects that appear near each other in the sky. The term usually applies to objects that appear to move across the sky like the moon and planets. Whereas stars don’t move much at all during a human lifetime. A conjunction means the two objects share the same east-west coordinates--what astronomers call the “right ascension.”

Anyway, it’s easy to get into the weeds with those terms. Just know that on Tuesday (March 31, 2020) morning, Saturn will be right on top of Mars, with Jupiter a little further to the right in the early morning southern sky.

It’s a great time of year for open clusters. There’s a lot to choose from in the evening sky. The Pleiades, the Hyades, Coma, Alpha Persei… but one of the more overlooked star clusters, especially under bright urban skies, is Messier 44, or the Beehive Cluster. Now, it’s dimmer and harder to find than those other clusters, so suburban observers will need to get creative. Here’s how I find it.

The Beehive Cluster is right smack in the middle of Cancer the Crab, which is actually a very dim constellation. To find it, make a big triangle between Regulus, the bright blueish heart of Leo, Procyon, the dimmer star of the winter triangle, and either of the two heads of Gemini—Castor or Pollux. Now if you don’t know where these stars are at all, you might have some trouble. Here’s where to look. Early in the evening, between 7:00 and 8:00, they’ll be to the east with Regulus being almost due east. Procyon will be to the southeast, and the heads of Gemini are high above those two. This large acute triangle with Regulus at the sharpest point will sweep across the southern sky. It’ll be highest in the sky and due south just before 11pm. Once you form that triangle of Regulus, Procyon, and either head of Gemini, Cancer the Crab is right in the center. So scan with your telescope until you see a loose cluster of dozens of stars. That’s M44, the Beehive Cluster.

When you find it, you’ll be looking at one of the first objects ever studied with a telescope… by Galileo himself.

All right—I’m no trickster, so I’d make a lousy leprechaun. No… there are no green stars. But there are a few that can appear green.

Blue stars that are really close to red stars can appear to us as a greenish blue. One good example is Antares B, the binary companion to the red giant Antares A, the heart of Scorpius.

If you wake up EARLY on St. Patrick’s Day, or any day in the next month or so, you can’t miss bright orange Antares A low in the southern sky. To see Antares B, you’ll need a decent-sized telescope. Point it right at Antares, and look for a much dimmer, greenish blue companion. That’s Antares B. Now again, the only reason it appears green is because a giant bright red star is right next door. It’s an optical trick. But as long as you’re outside with a big telescope, there are a couple other nearby objects you’ll want to see.

First, let’s address the VERY bright objects to the southeast. Those are all planets. The brightest are Mars and Jupiter, but that dimmer yellow one is that jewel of the solar system—Saturn. Of course, if you have a telescope good enough to see Antares B, you probably already know how good the planets look through it.

Not to mention there’s a waning moon out in the morning with the terminator, or shadow accentuating all those great surface features like craters and mountains.

So if you’re up for some early morning observation, there’s plenty to see in the southern sky.

Leo sweeps across the southern sky all night this time of year. In the evening, it’s to the east. To find it, look for the Big Dipper. It’ll be straight up and down with the cup at the top. Connect the two stars at the top that make up the end of the cup, and from that straight line, extend the line to the right toward the east, and when you hit the bright star Regulus, you’ve arrived. Regulus is the so-called “heart” of Leo the Lion, so once you find it, backtrack to identify the rest of the constellation. Leo depicts a lion laying down with its head up, so if Regulus is its heart, it marks the bottom of the constellation. To find its mane, look above it for a series of stars that form a backwards question mark with Regulus at the dot.

If you haven’t figured it out yet, Regulus is the star of the show if you’ll pardon the 100% intended pun. It’s bright enough to see under urban skies, and it spins so fast that it’s not a perfect sphere. It’s more like an egg or pumpkin. It spins more than 150 times faster than the sun. The sun takes 27 days to make one rotation. Regulus does it in just 16 hours. And keep in mind, Regulus is around three times bigger than the sun, and almost 4 times as massive. In fact, if it spun just 10 percent faster, it would fly apart. Why does it spin so fast? Well, we really don’t know… yet.

Every good hunter needs support. Orion and his two dogs have reigned the evening sky in the winter since before human civilization. One of the earliest representations of Orion appeared in cave art dated more than 32,000 years ago.

Orion’s easy to spot—just look for the three stars that make up his belt. But the dogs are easy to find too. First you need to find the Winter Triangle. It’s a large, almost perfect equilateral triangle of bright stars that are prominent in Winter’s evening sky. It’s made up of Sirius, the brightest star in the night sky, Procyon, another bright star, and one that used to be a lot brighter… Orion’s right shoulder, Betelgeuse.

Since around Christmastime last year, Betelgeuse dimmed dramatically, leading some to believe it may go supernova, though that’s not likely. Recent observations show the more likely culprit is an ejecting of its outermost gas layers, which is obscuring its brighter core.

Those other two stars in the winter triangle make up the brightest stars in the two dog constellations—Procyon in Canis Minor, the lesser dog; and Sirius in Canis Major, the greater dog. Sirius is also known as the dog star for that reason. Ever heard the term “dog days of summer?” 6 months from now, when Sirius is in the opposite part of the sky, it rises just before the sun—leading the ancient Greeks to believe that its brightness helped the sun warm the Earth. Sirius outshines the other stars in Canis Major by a longshot, but a star chart will help you find them. Canis minor only consists of two main stars—Procyon and Gomeisa, which is much dimmer, but still visible to the naked eye.

If you’re lucky enough to have clear skies in the morning, grab a coat, step outside, and look to the southeast. You’ll see a bright orange point of light just above the horizon. Mars.

Now, don’t be fooled by the star Antares, whose name actually means ‘rival to Ares’. Ares being the Greek god of war. Mars was of course the Roman god of war, so Antares can also mean ‘rival to mars,” which is exactly what it is right now. Antares is close to Mars in both color and brightness, but Antares is higher and further south in the morning sky. Another way to tell the difference is to look for twinkling. Because the light we see from Mars comes from the sun’s reflection, and a few other reasons, Mars doesn’t twinkle. Antares is a red supergiant less than 600 light years away, so it’s bright, but because it’s a single point of light in the night sky, it’s more susceptible to atmospheric interference, which is why it and other stars appear to twinkle.

Now, about this rare event… on Tuesday morning, February 18th, just after 7am Eastern, Mars will disappear behind the moon. An event known as a lunar occultation. You can see this up close with a telescope, but clear skies are a must, and that’s not looking very promising right now. But if the forecast changes and Tuesday morning ends up looking a little nicer, do yourself a favor and take advantage. You’ll be able to watch in real time as the crescent moon slips in front of the red planet.

During the winter, Sirius is very prominent in the evening sky. It’s part of what’s called the Winter Triangle, a near-perfect equilateral triangle of bright stars that moves east-to-west across the southern sky at night. If we’re lucky, and the sky clears just enough to see all three stars of the winter triangle to the southeast, we’ll be most likely to see its brightest corner, the one closest to the horizon, Sirius.

Now, like so many of the stars in the sky, Sirius is not alone… It’s a binary system consisting of the very bright, main sequence stage star we can see with the naked eye, Sirius A, and a much smaller companion white dwarf stage star, Sirius B. Now, you won’t be able to differentiate the two unless you have a really big telescope under exceptionally dark, clear skies. In fact, Sirius B wasn’t discovered until the mid 19th Century. And, while Sirius A, the one we can see, is bright and shiny, Sirius B is pretty interesting too… It’s a white dwarf, so it’s really just the core remnant of a star. But it’s really massive for a white dwarf… imagine a star about the size of Earth… that’s actually slightly more massive than the sun. That’s Sirius B.

Sirius B used to be a lot bigger. Where the bright Sirius A is about twice as massive as our sun, Sirius B used to be 5 times as massive. But again, that was a long time ago. Since then, it has swelled to a red giant, and shed its outer layers into space, leaving one of the more massive white dwarfs we know of.