Mission 20: Beta Monocerotis, a triple star

Mission Objective: Multiple star

Equipment: Telescope

Required Time: 10 minutes

Related Missions: Ring of Fire

Map to Beta Monocerotis, modified from the Monoceros constellation diagram on Wikipedia.

Hey look, I finally posted a new mission.

I’ve been slowly working away at the Astronomical League’s Double Star Club, and I just discovered this gem last week. It’s not the world’s easiest star to find. As a naked-eye subject, the constellation Monoceros, the Unicorn, is fairly dim and unimpressive. Beta Monocerotis is prominent in the western part of the constellation, just east of Orion and north of Canis Major, making a wide triangle between Sirius and Kappa Orionis (also known as Saiph, which is Arabic for “sword of giant”). I could just make it out with the naked eye from Claremont, hovering in the light dome over Los Angeles.

To fully appreciate this star’s charms, you’re going to want a telescope, but it doesn’t have to be a big one. I made my observation with my 80mm refractor, which has a focal length of 900mm (f/11). Using a 32mm Plossl eyepiece (28x), it was clearly a double star but not cleanly split (seeing was lousy). With the 12mm Plossl (75x) it was clearly split into a nice pair of equally bright gems. I decided to go up to 150x with a 6mm Orion Expanse, my favorite high-power eyepiece. So glad I did–at 150x, the southern member of the “equal pair” turned out to be a double itself, also of equally matched components! It was a nice surprise and a breathtaking sight, the three stars twinkling away at 150x.

I looked at dozens of photos, sketches, and eyepiece simulations of Beta Monocerotis while writing this post, and the image that come closest to capturing what I saw at the eyepiece is this sketch by Jeremy Perez, who kindly gave me permission to include it here. Jeremy is one of the authors of Astronomical Sketching: A Step by Step Introduction, and his website, Belt of Venus, has beautiful and evocative sketches of just about everything in the sky, from the moon and planets to deep sky objects and double stars. It’s definitely worth checking out, both to marvel at his work, and to get ideas for your observing wish list.

A poster on Cloudy Nights had this to say, “I just looked at Beta Mon last night in good seeing. What a neat thing. It reminds me of one of those antique mechanical solar system models.” I couldn’t agree more–it conveys exactly the same sense of mechanical precision and aesthetic appeal as an old-fashioned orrery.

If you’re going to catch Beta Monocerotis, you’ll need to do it soon after dark, because Monoceros is following Orion to the western horizon fairly early these days. Go have fun!

Cosmic triple play: the moon, Jupiter, and Uranus tonight

The not-quite first quarter moon will zip past Jupiter and Uranus tonight (that is, Monday night, Dec. 13). Here’s the view in Stellarium at about 6:00 PM, Pacific time, looking high in the south:

The moon and Jupiter are the easiest naked-eye objects in the skies right now. Grab some binoculars–any binoculars–to see moon craters, the moons of Jupiter, and Uranus, which will appear as a bright star just above and left of Jupiter (or north and east, if you prefer). It’s not the only reasonably bright ‘star’ in the field, so here’s a more printer-friendly map to take along:

Note the nearby stars K and 9 Piscium (so named because they are in the constellation Pisces, the fish). They make a visual double but not a gravitational one, which means that they are accidentally aligned as seen from Earth. K is brighter mostly because it is closer, only 162 light years away compared to 9′s 400-plus.

All of those are easy binocular targets. In a small telescope, the view only gets better: hundreds or thousands of craters and other lunar features are visible, as well as cloud belts on Jupiter, and Uranus may show up as a small blue-green disc instead of a mere point if you crank the magnification.

But it will be worth taking a moment to see even if all you observe with are a couple of Mark 1 eyeballs. Go have fun!

Mission 4: The Big Dipper

Mission Objectives: Constellation, Bright Stars, Multiple Stars

Equipment: Naked eye, Binoculars

Required Time: 3 minutes

Instructions: Get to a place with a clear northern horizon, look to the northwest, and find the Big Dipper. Seriously, it’s just that easy. Here, you can practice with this:

The view to the northwest right after sunset in the southern US, in Stellarium.

Note the little red W and N in the corners of the picture; at this time of year, the Dipper is exactly halfway between those cardinal points. If you can’t find it, make sure that it’s just after dark, see that your view isn’t blocked by clouds, trees, or mountains, and double check that you are, in fact, in the Northern Hemisphere.

The Big Dipper as a guidepost to the northern sky.

If you can find the Dipper, you can find at least two more bright stars and have an edge on identifying their constellations. The path that is most widely known is that the two stars that make up the front end of the “pan” point unfailingly to Polaris, the North Star, around which everything else in the heavens appears to rotate. Also, you can follow the handle of the Dipper and arc to Arcturus, the brightest star in the constellation Bootes.

Like Lyra, Ursa Major has a double star treat for naked eyes and binoculars. The middle star in the handle is in fact two, Mizar and Alcor, the horse and rider. Your eyes don’t have to be particularly sharp to see that the brighter of the two, Mizar, has a dim companion. This is also a dead easy split with binoculars. A telescope working at even low magnifications of 40-50x will reveal that Mizar has another, even fainter companion, called Mizar B. Mizar was probably the first telescopic binary discovered, possibly as early as 1617, less than a decade after Galileo first aimed a telescope at the heavens. As if all of that weren’t enough, Mizar A and B are themselves both binary, although the components are too close to be separated by telescopes and can only be detected through spectroscopy.  So Mizar is a four-star system, another “double double”, all by itself.

The Big Dipper is just the rear end and oddly long tail of the constellation Ursa Major, the Great Bear. Polaris is at the end of the tail of Ursa Minor, the Little Bear. There are lots of stories about how these bears came to have such long tails–see what you can find. Because Ursa Major is so close to the celestial North Pole,  it is visible for most of the year and only dips below the horizon briefly at mid-northern latitudes. If you go far enough north, the Great Bear is visible all the time. The Greek word for bear is ‘arctos’. And so we call those far northern regions, under the eternal reign of the bear, the ‘arctic’.

Mission 3: Waxing Lyrical

Mission Objectives: Constellation, Multiple stars

Equipment: Naked eye, Binoculars

Required Time: 3 minutes

Related Missions: Summer Triangle

Instructions: Ready for another constellation? This one is a piece of cake: nice and compact, all bright stars that show up easily even in the city, two simple shapes, high enough to be seen clearly throughout the Northern Hemisphere, and it even has a couple of nice Easter eggs for binoculars and small scopes. I’m talking about the constellation Lyra, the Lyre.

You remember how to find Vega, I’m sure (if you’ve forgotten, refresh your memory here). This time of year it is the brightest star overhead in the early evening; in fact, it is the fifth brightest star in the sky. It is so bright mainly because it is so close, only 25 light years away, not because it is big, although it is about twice the mass of the sun. Because it is heavier it is burning through its fusion fuel faster, and it will swell into a red giant in perhaps half a billion years. By comparison, the sun is only about halfway through its 10 billion year lifespan.

The constellation Lyra (red lines), and the Double Double (white arrow), from Stellarium.

You already know that Vega is at the apex of the Summer Triangle. Even with the naked eye and under city lights, you should be able to see that Vega is also one point of a much smaller triangle, and that the smaller triangle has a parallelogram hanging off its southeast corner. That’s it, the constellation Lyra. If you can find the triangle and the parallelogram, you’re done.

But wait–there’s more! If you’re very sharp-eyed–or your corrective lens prescription is up-to-date–you may be able to see that the star at the “free” corner of the triangle is not one point of light, but two close together. This is Epsilon Lyrae, the famous “Double Double” star. It’s called the Double Double because both of the two stars that make up the naked-eye binary are themselves binary; so, two pairs of binary stars, circling each other. As if that wasn’t enough, spectrometry shows that the system includes a fifth star that is too dim for even telescopes to see.

If you can’t split Epsilon Lyrae into two components with the naked eye, grab your binoculars–any binoculars. Binoculars will show the wide separation between the two pairs, but to split the four visible stars requires a telescope with good optics. At 96x in my 90mm Maksutov-Cassegrain scope, the two pairs look like a couple of 8s, one standing up and one laying on its side. For a much better view, check out this photo of the four stars by acclaimed astrophotographer Damian Peach.

And as long as you’ve got your binoculars out, you might as well have a look at the third “star” in the triangle, Zeta Lyrae (the one star shared by the triangle and the parallelogram). This one is a simple double, not a Double Double, and the two component stars are much closer together than the double-eights of Epsilon Lyrae. Using my 10×50 binoculars and bracing my arms on the top of my car, I just make out that Zeta Lyrae is indeed two points of light, but I can’t hold the binoculars steady enough freehand. About time for a post on mounting binoculars, methinks.