Tag Archives: observing

January Skywatch

1 Reply

This month so far the sky has not been especially friendly for star-gazing. Besides lots of clouds, the big problem with observing in winter is a simple one: it’s cold! In the summer it’s easy to linger at the telescope, waiting for unexpected objects to pass into view or searching for new, hard-to-find targets. In the winter, targets that can be found quickly—before the fingers start to numb—and easily are better.

Fortunately, many of the celestial targets in the January sky are indeed bright and easy to spot quickly. Last month I started with an introduction to the constellation Orion. This month we’ll zoom into some of its telescopic wonders that can be caught on the frigid, (hopefully) clear nights of January.

As I’ve mentioned in this column in the past, I’m partial to observing double and multiple stars with my backyard telescope. These objects are bright enough to find in the light-polluted skies of town, and they’re endlessly varied. The most spectacular object to view in Orion is of course the Great Nebula (which we’ll examine in a moment), but Orion also hosts several lesser-known but lovely and easy multi-star targets.

We’ll start with the easiest target. Mintaka is the westernmost star in Orion’s belt. Through a modest telescope (I usually use a Dobsonian reflecting telescope with a 6-inch aperture) at low magnification (48x), it’s clearly revealed as a wide double star. It doesn’t have the impressive color contrast of a famous pair like Albireo, but with a separation of about 50 arcseconds, it’s easily revealed as a double even in a pair of binoculars.

Things get more impressive swinging the telescope just slightly eastward to the star sigma Orionis, the moderately-bright star visible just beneath Alnitak, the easternmost star in Orion’s Belt. Sigma is actually a triple-star system, with a few other surprises in the field of view. The components of the star are much tighter (closer together) than Mintaka, so I use a higher magnification (60x). The differing colors of this triple star are easily apparent and to my eyes seemed reddish, blueish, and whitish (though part of the fun of observing multiple-star systems is that each observer seems to note different tints). Even more impressive: in the same field of view, just to the west, is another, dimmer triple star system, Struve 761!

Orion_constellation_map

If your fingers are freezing, don’t despair: the next sights are well worth the chill. Move the telescope to the cluster of stars marking Orion’s sword. For now, pass up the Great Nebula (also known as M42) for the star at the southernmost tip of Orion’s sword. This is iota Orionis. Iota is a close pair (separation of 11”, I viewed it at 70x magnification): a bright star with a dim companion. In the same field of view though, is the wider, even pair of Struve 747. But that’s not all: a fainter third double star, Struve 745, can also be spotted in this view.

Finally, the most famous multiple-star system in Orion is buried at the heart of Orion’s most famous sight: the Great Nebula. Just north of iota, you can’t fail to spot it on clear nights. The four stars of the Trapezium are surrounded by the cloudy glow of the Nebula, which extends across the entire field of view in greenish, hazy ribbons. The larger your scope (and the darker your sky) the more detail you’ll see, but even with a 6-inch from my front yard in town, it’s a sight to brave the cold for.

We still have not exhausted Orion’s treasures though. Part of the appeal of searching after double stars is to tackle more challenging pairs: pairs that are either very close to each other or have a significant contrast in brightness. If you’re up for a challenge, try the star lambda Orionis, marking Orion’s head. This is an even double star with a separation of only 4 arcseconds (remember that Mintaka’s components were 50 arcseconds apart). With my 6-inch, I can easily split it on a clear night with a magnification of 70x. Compare this with Rigel, the brilliant star of Orion’s foot. Rigel has a dim companion at a distance of 10 arcseconds, but the brightness of Rigel makes it very hard to spot this pale blue companion star. On my most recent attempt, it took a magnification of 133x to spot it for sure.

I hope I’ve convinced you that Orion is a treasury of sights that make it worth braving the cold this month. Perhaps though you don’t have a telescope to take a look yourself and you’re wondering about the type of instrument to purchase to get started, or maybe you got a telescope this Christmas and you want to know more about how to put it to use. Next month I’ll spend some time going over telescope basics and providing my own thoughts on steps toward easy backyard observing.

This column first appeared in the Kankakee Daily Journal.

October Skywatch

Leave a reply

Sorry this is a bit late folks, but here’s my local astronomy column for this month:

This month, the skies favor the early riser. As Saturn slips toward the western horizon in our evening skies, Jupiter, Venus, and Mars take center stage throughout October in the skies before dawn. If you are someone who prefers to rise early, you are in luck. If you’re someone who tends to sleep in, set your alarm and treat yourself to a view of these bright objects at least a few times this month to see the steps in the eastern sky. I’ll give you a breakdown of the performance so you know what particular dates to watch for.

First though, a quick re-cap of the biggest celestial event of last month: the total lunar eclipse, which brought the current tetrad of total eclipses to a conclusion. Last year I had to bribe my astronomy students to rise before dawn to see the eclipse, but this time it was easily visible in the early evening sky. We shut off the lights on our side of campus, set up telescopes around the perimeter of the planetarium, and then waited for the sky—which had been cloudy all day—to clear. It did just in time, and we were able to view the duration of the eclipse in clear, dark skies from the heart of Bourbonnais. It was a sight, I trust, that few students will soon forget. (Several took pictures of the eclipse and have been posting them to social media under the hashtag #OlivetAstro.)

BloodmoonTimeLapse
Time-lapse of the lunar eclipse taken by ONU student Nick Rasmussen.

Now that the Moon is past full, it’s slipped from the evening skies and does not rise until after midnight. Its display isn’t over though, as it moves to the morning sky to join the planets before daybreak as a slender crescent. And that’s the first movement of this act you should catch these October mornings: set your alarm and rise before dawn on either Thursday, the 8th, or Friday, the 9th (or both). If the sky is clear, you’ll see three bright planets strung out in a line pointing down toward the eastern horizon.

The highest and brightest of these is Venus, which rises at about 3 AM and is high in the eastern sky before sunrise. Mars trails it to the east, and below them both is bright Jupiter. On the morning of the 8th, a thin crescent Moon rides just above Venus. By the next morning the Moon has dropped to join Mars and Jupiter as an even thinner crescent lower in the east. The slanted line of the three planets in the morning sky is a powerful illustration of the disk of our solar system, viewed from our tilted angle on the planet Earth.

Moving forward through the month, Venus falls eastward against the background stars each month, while Jupiter and Mars rise farther into the west. Jupiter passes by Mars on the morning of Saturday, the 17th, for the closest conjunction of this planetary arrangement. The bright giant planet passes within half a degree of the ruddy red planet. That’s about the diameter of a full Moon. At that distance, both planets could be visible in the same field of view through a telescope eyepiece.

It’s that ruddy red planet on which NASA scientists last month found the best evidence yet of running water on its surface. They studied the composition of dark tracts on Martian hillsides that change with the seasons and concluded these formed by briny water seeping out and staining the Martian surface.

Finally, as Venus continues its eastward motion against the background stars, it passes by Jupiter on the morning of Sunday, the 25th. Though the two planets are within a degree of each other (twice the diameter of a full Moon), this may be the most conspicuous conjunction of the month, as Jupiter and Venus are the two brightest planets in the sky. On the morning of the 25th and the following morning, they’ll form a brilliant pair with Mars trailing below them to the east.

Of course, their apparent closeness is only an illusion in our sky, the same way the light from a nearby lighthouse might appear close to a ship passing along the horizon. It’s only a matter of perspective. In reality, millions of miles of empty space separate those bright lights in the night.

This column first appeared in the Kankakee Daily Journal.

Double and Multiple Stars and How to Observe Them

Leave a reply

Double and Multiple Stars: And How to Observe ThemDouble and Multiple Stars: And How to Observe Them by James Mullaney

My rating: 4 of 5 stars

“The amateur astronomer has access at all times to the original objects of his study; the masterworks of the heavens belong to him as much as to the great observatories of the world. And there is no priviledge like that of being allowed to stand in the presence of the original.”
-Robert Burnham, Jr. (my emphasis)

One of my goals this summer has been to spend more time with the fleet of telescopes I have access to through my university. I teach about the night sky and I research scientists who spent their lives studying the night sky, but I find I’ve had very few opportunities myself to get to know the sky outside the simulated confines of the planetarium dome.

Double stars are an ideal target for starting out. Unlike nebula, galaxies, and other deep sky targets, double stars are bright and fairly easy to spot. They’re like tiny gems hidden up there in the sky. The sky is a map, and sometimes it’s hard to learn. It’s often difficult to tell whether the star you have in your sights is actually the star on your charts that you think you might be looking at. Yet if your resources tells you it’s supposed to be a tight, nearly equal double with a separation of six arcseconds, and if you see it staring back at you like a pair of distant celestial headlights, then you know you’ve found it. They’re targets that are immediately rewarding, bright enough to spot on moonlit nights or in light polluted skies, and varied enough to be interesting.

Take separation, for instance. My six-inch reflecting telescope hasn’t had any troubles on the evenings I’ve been observing splitting pairs down to a separation of about four arcseconds. Izar in Bootes, with a separation of just under three arcseconds, shows a hint of the bluish companion star elongated from the edge of the brighter orangish primary. Depending on the viewing conditions each night, my scope should theoretically be able to distinguish even closer pairs, but the challenge of realizing this is part of what makes these targets rewarding.

Then there’s color contrast. You view an image from the Hubble Space Telescope, and it seems like space is vibrant with color. Yet actually viewing a nebulae or galaxy with the eye in a telescope eyepiece reveals perhaps a hint of greenish glow at best. With double stars though, the color contrast in star pairs is often quite dramatic. Different people observe different colors, which are artifacts of both intrinsic color differences in the stars and contrast between them.

Finally there’s simply the conceptualization of what you’re actually looking at. Most very close doubles are binary stars, which means systems of two (or more) stars rotating around a common center of mass. These are the objects John Herschel and others were studying in the early 1800s in order to directly calculate stellar masses. (They’re still the only method we have for directly measuring the mass of stars.) These star pairs, I argue in my dissertation, were instrumental in changing the way people thought of the stars: seeing them as vast physical systems. They continue to inform our popular stellar conceptions; recall the iconic scene of the double sunset on Tatooine in Star Wars.

Fortunate for the enthusiast like me there are a host of guides and resources regarding showcase double stars to observe. The Cambridge Double Star Atlas is a great place to start, and banking on the usefulness of that resource I purchased this observing guide by one of the authors of that atlas: Double and Multiple Stars and How to Observe Them. This slim guide is an ideal introduction to the topic, exploring in an overview the practical aspects of observing these objects but also going into some detail on the real scientific contributions an amateur could pursue. Mullaney’s enthusiasm for the topic is contagious, from the introductory physical descriptions of double stars as astrophysical objects (reminescent of the language popularizers were using to describe them in the 19th century) to his own advice on keeping observing journals.

Though the prose is good, I had two big complaints with the work. The first is the quality of printing. It was clear as soon as I cracked the cover that this was a print-on-demand title by Springer, with the pages consisting of scans of a PDF or other electronic image. The text is not crisp or clear, and on many pages there is grey stippling in what should be the white space between letters and lines. It’s not bad enough to make the text illegible, but it is annoying. The second is that Mullaney says the work is really two resources in one: a background or overview on double stars and observing them, along with an observing guide of locations and descriptions for one hundred showcase double stars. Yet– though I haven’t compared it star to star– this list seems to duplicate the list provided in the Cambridge Double Star Atlas. So if you’re looking for a lot of new double stars to admire, you might be disappointed.

“What we need is a big telescope in every village and hamlet and some bloke there with that fire in his eyes who can show something of the glory the world sails in.”
-Graham Loftus (my emphasis)