Weekend Sky Report

Stars form in huge clouds of gas and dust that some astronomers call “Stellar Nurseries.” The gas accretes or collects together, and as that body gains mass, its own gravity then causes it to collapse in on itself. Once there’s enough matter there, nuclear fusion begins, and a star is born. And much of what we know about star formation, we learned by studying the nearby Orion Nebula.

The Orion Nebula is just over 1300 light years from our solar system, and it’s believed to be an enormous 24 light years across. Because it’s so big, and… relatively close, it’s easily visible to the naked eye, even under bright, suburban skies.

You can find it this evening in the southern sky. Just look for the three stars that make up Orion’s Belt, and look below it for what looks like a smaller collection of stars. In the middle… is the Orion Nebula. Grab some binoculars or any size telescope for a better look.

Now, to you, it’ll just look like a fuzzy cloud around a few stars. But most photos you’ll find of the Orion Nebula are full of brilliant colors and detail. That’s the result of long exposures, or specialized equipment observing wavelengths we can’t actually see. But because astronomers are able to use those tools, we’ve learned so much about how stars are formed.

So if you see it this weekend, you’ll see a spot in the sky where countless stars… came to life.

Mars is bright and easy to spot in the western sky until the beginning of summer. But for the next few days, you can use Mars to spot the 7th planet… the ice giant Uranus.

Now, disclaimer… you may need access to a halfway decent telescope to see it. A very small or toy telescope probably won’t cut it for this one. It might if the moon weren’t also out in the evening, but it is… and it’s big and bright, so it’s washing out a lot of the dimmer targets.

But if you have a telescope, here’s what you do. Find Mars. It’s that bright orange dot in the western sky in the evening. The later it is, the lower it’ll be. Once you find Mars, scan straight down very slowly until you see a pale turquoise-colored dot. And there it is.

Even though Uranus wasn’t discovered to be a planet until the late 18th Century, it was almost certainly observed before then… Ancient greek astronomers may have mistaken it as a star, as did 17th Century English astronomer John Flamsteeed. But in 1781, William Herschel observed it and initially recorded it as a comet. But upon further observation, determined it to be a planet beyond Saturn.

Uranus is on its side compared to other planets. And it was long hypothesized that this was the result of a giant collision. It wasn’t until recently that this was looked at more closely. Research done at England’s Durham University suggests that somewhere between 3 and 4 billion years ago … an object larger than Earth hit Uranus, effectively knocking it over.

So tonight, find Mars… then scan down to see a planet that’s more than a billion and a half miles away.

Look high to the east in the evening and you’ll see two bright stars, one on top of the other. The top one is more blueish, and the bottom more yellow. That’s Castor and Pollux, respectively. The two stars that make up the heads of Gemini.

Castor and Pollux are of course the mythical twin brothers from the Greek legend, but let’s talk about the stars themselves.

First, Pollux. At just over 33 light years away, it’s the closest giant-stage star to our sun. A giant star is one that has depleted all of the hydrogen at its core and puffed up to many times its original size. Pollux also has a planet. One of the first exoplanets ever discovered… at more than twice the mass of Jupiter, it causes Pollux to wobble. The planet was first suspected in the early 90s when the wobble was first analyzed, and it was finally confirmed in 2006.

Now let’s look at Castor. What looks to the naked like a single star is actually a multiple star system of SIX stars in three binary pairs. Now, you can’t see all six from your backyard… but you can split the two brightest pairs with a small telescope. Just point your telescope right at the star and focus it until one star begins to look like two. And there you have it. Castor A and Castor B.

Splitting binary stars is a common hobby among amateur astronomers, and Castor is a great place to start. Again, look for Gemini high to the east in the evening. The later it is, the higher it will be. By 11 o’clock, it’ll be straight up.

Look to the west under clear skies, and you’ll notice a bright orange star. Except it’s not a star… you can tell because it doesn’t really twinkle like the other stars you can see. That’s a planet. The planet Mars.

We’ve known Mars was special since the dawn of civilization. And likely even before that. Recorded observations of Mars date back to the time of Mesopotamia. They called it Nergal, after their god of war, plague, death, and disease. Of course, we know Mars is the Roman god of war and destruction. We know this common association is probably due to its red color from the large amount of iron oxide in its soil. And iron oxide is the same reason our blood is red. So naturally our ancient ancestors saw a wandering point of blood-red light in the night sky as a bad omen. But since we’ve learned what it was, why it was red, and could see it up close with a telescope, our old fears have resolved to curiosity and creativity. Numerous science fiction and horror stories have taken place on or about Mars. And of course science has advanced quite a bit thanks to our intense curiosity about the red planet. Dozens of craft have visited Mars, and it currently has eight active spacecraft studying it as we speak. Six orbiters, and two landers, Curiosity, and InSight. Of course numerous plans are in place for crewed missions to Mars. Some say humans will be there within 10 years.

But right now, it’s up there for our own contemplation in the western evening sky through the rest of winter and most of spring.

Around 9pm (Friday, January 25, 2019), look low to the southeast to find bright white, twinkling Sirius. Above it, you’ll see that iconic winter constellation Orion the Hunter. The orange star at his shoulder is the red supergiant Betelgeuse. Draw a line between Sirius and Betelgeuse, then look to the left, or east to find Procyon (PRO-see-on), another bright white star, and there you have it. A nearly perfect equilateral triangle of bright evening stars.

Each star in the winter triangle is interesting, but let’s focus on Sirius. It’s twice the mass of our sun, but it’s much younger… where our sun is over 4.5 billion years old, Sirius isn’t even a quarter billion years old. Sirius is also 25 times brighter than our sun. All of those factors put together help to explain why it’s the brightest star in the night sky. Its mass helps to explain its age… more massive stars burn hotter, but don’t live as long. That, and the fact that it’s only 8.5 light years away.

And if you look at Sirius long enough, you’ll notice a lot of twinkling… that’s less about the star itself, and more about the Earth’s atmosphere. Yes, the brighter the star, the more apparent the twinkling…but the twinkling only happens because it gets refracted through the atmosphere, and the atmosphere is variable… it’s thicker in some places and thinner in others. So when you shine a bright, distant light through a variable atmosphere, it twinkles.

So tonight, brave the cold, find bright, twinkling Sirius, and from that, the winter triangle.

Before we could really track the movement of the moon in relation to the sun, a lunar eclipse, and the blood red color associated with it were seen as a threatening display from the heavens. Ancient Mesopotamians thought it meant the moon was being attacked by demons. Some Chinese cultures believed that the moon’s blood red color meant famine and disease were coming. The Incans would throw spears and stones at the moon during an eclipse.

Ancient Greeks, however, correctly accepted the Earth’s shadow during a lunar eclipse as evidence that the Earth was round.

But what about the color? Why does the moon appear red?

The answer is in the Earth’s atmosphere. If the Earth didn’t have an atmosphere, the moon would just disappear during an eclipse. And there’d be no one here to enjoy it. During a lunar eclipse, the Earth is between the sun and the moon. And while the Earth completely blocks the sun, some of the light gets refracted through the atmosphere, but only the longer wavelengths make it through. And since red is the longest wavelength of visible light, that’s what we see. And it’s the same reason certain sunsets can have a beautiful red hue.

You may have heard that this weekend is also a supermoon—meaning the moon is as close as it can be to the Earth—what’s called perigee. But the difference between the full moon at perigee and the opposite, apogee, is like the difference between a Susan B. Anthony Dollar, and a quarter. Barely noticeable.

The total lunar eclipse will begin happening Sunday, January 20, 2019. You’ll start to see the moon change around 10:30 p.m. At midnight, the moon will be a deep red.

At this time of year, this evening’s target is high in the Eastern sky.

Auriga, Latin for Charioteer, is a constellation made up of just six main stars arranged in a sort of circle. It’s said to depict the legendary Athenian king Erichthonius (air-ee-THOHN-yos) holding a small goat on his left shoulder, and the reins of the chariot in his right hand.

The brightest star in Auriga, Capella, is the third brightest star in the northern celestial hemisphere behind Vega and Arcturus. Capella is latin for… little goat. And although Capella appears to be a single bright star, it’s actually an unusual system of four stars in two binary pairs.

To find Auriga, look high to the East before 10pm. Later than that it will be either straight up or high to the west. That bright star is Capella. The other five stars along with it form an imperfect hexagon. Now, if you have a decent telescope, you can look closer and find three open clusters. Messier 36, 37, and 38. The brightest and most interesting is Messier 37, which can be found between the star opposite Capella, Elnath, and Theta Aurigae (aw-RYE-gay).  Trace a line between those two stars, go to the center, and scan just outside of the constellation. It’ll appear as a fairly dense, but pretty dim open cluster of hundreds of stars.

Auriga has been known since the dawn of civilization. Mesopotamians called it GAM. To them, it, coincidentally, represented… a herd of… goats. And just so you know, ancient Sumerian, the language of the Mesopotamians… is in no way related to latin. Just something to ponder as you look up… this evening.

You’ll need a telescope to see this weekend’s festively-named target.

If you’re like me, your Christmas tree is still up. Not because I keep it up until the Feast of The Epiphany, which is this Sunday. I wish my reason was as respectable as that… No, I’m just a little work-shy… indolent… lazy.

OR I could say that I won’t take it down until I find the Christmas Tree Cluster. A small, distant star cluster between the constellations Gemini, and Orion.

The Christmas Tree Cluster is the more luminous part of a larger area designated as NGC 2264. This area also includes the Cone Nebula, Snowflake Cluster, and the Fox Fur Nebula. But most home telescopes will only be able to see the Christmas Tree Cluster.

At 2300 light years away, the cluster resembles an upside-down Christmas tree with the brightest star representing the base of the tree. The other stars form a loose cone shape that makes it look like Christmas tree lights.

To find it, look to the East after 8pm. If you have a good view of the Eastern horizon, you’ll notice the bright star Procyon in Canis Minor. Trace a line between bright white Procyon and bright orange Betelgeuse, the right shoulder of Orion. Find the center of that line and scan upward with your telescope until you see a small cluster of brilliant blueish stars. That’s it. The Christmas Tree Cluster.

When you find it, you’ll be looking at not only the cluster itself, but also the nebula where it formed. If you have a big enough telescope and are under clear, dark, rural skies, you’ll see some of that surrounding nebulosity.

And then… get back inside and take your Christmas Tree down. I’ll be right there with you.

It’s big, it’s bright, and it could go supernova in our lifetime.

Betelgeuse, the right shoulder of Orion the Hunter, which is prominent in the eastern sky this evening, is a truly remarkable star. For one thing, it’s one of the largest stars we’ve ever discovered. If you were to replace the sun with Betelgeuse, it would engulf all four inner planets from Mercury to Mars, and, by some estimates, even Jupiter. It’s enormous.

Now, in the celestial world, typically the bigger the star, the shorter the lifespan. Our sun is about 4 and-a-half billion years old. Betelgeuse is only estimated to be 8-and-a-half million years old. And yes, it may go supernova in our lifetime… or it could take up to a million years… we simply don’t know.

What we DO know is that WHEN Betelgeuse goes supernova, it will easily be visible in the daytime, maybe even outshining the full moon.

One thing that sparked a lot of talk about Betelgeuse going supernova was an observation made in 2009 that showed its size had contracted by 15%, prompting rumors that the star was collapsing and may go soon. Amateur theories went wild, even doomsday predictions, but while the Betelgeuse supernova will be huge, even on the celestial scale, it’s still too far away to cause any ill effects on Earth. At almost 650 light years away, it’ll just be a REALLY bright star for a few short months. And then… one of the brightest stars in the night sky… will be gone forever. But it won’t be a time for mourning, because if we DO get to see it, we’ll be witnessing one of the most significant and spectacular celestial events in human history.

So I’ve seen some memes on social media that say that this year will be the first Christmas full moon since 1977, and that we won’t have another one for another 19 years. Well yes…that was true… three years ago in 2015. Those same memes are popping back up this year. Perhaps you’ve seen them. No, I have no idea why. Maybe because the idea of a full moon coinciding with Christmas day seems like fun… To me though, the great thing is, we get a full moon every month. And this month, no… it’s not on Christmas. But it is this weekend. And this weekend is the winter solstice.

Friday night it will be close but not technically a full moon, though almost no one will be able to tell.

Saturday night is the official Full Moon. And the great thing this month is that the full moon is an all-night moon… rising in the early evening and staying out almost all night, shedding a little light on the longest nights of the year.

Now if you’ve never looked at the moon through a telescope, do it this weekend. Personally, I like to look at a moon with a shadow, like a gibbous, crescent, or quarter moon because the shadow accentuates textures like craters and mountains, but there is something striking about a big, bright, full moon filling up the eyepiece. And almost any telescope will do. Even binoculars will show details you can’t see with the naked eye.

Oh, and just because the moon won’t be full on Christmas doesn’t mean it won’t be worth a look then either. Again, shadows are fun.