Tag Archives: Skywatch

April Skywatch

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I’ve promised a column on some telescope basics, and as the evenings start to warm up it’s finally time to deliver. Maybe you’re interested in more stargazing than casual naked-eye observations from your back porch, but you’re unsure of where to begin. Sometimes the options for purchasing a good starter telescope seem quite daunting. Where to begin? What type should I get? Which mounting is best? How do I avoid a cheap dud?

This month, I’ll offer a few pointers on choosing and getting started using a telescope for some basic backyard observations. As I’ve mentioned before, I focus on observing objects that you don’t need to be in perfectly dark skies to see. My own stargazing takes place in the city limits of Kankakee, with streetlights, trees, and the occasional porchlight marring the view. With a little knowledge and patience though, even a city sky can be a treasure trove.

Of course, it all starts with a good telescope. When I was preparing to purchase a new set of telescopes for my astronomy labs at Olivet several years ago, I asked the members of the Kankakee Area Stargazers for advice. I wanted instruments that were high quality but relatively inexpensive, easy to use and train students to use, and resilient enough that I wouldn’t worry about them being easily damaged The scope most recommended was a basic 6-inch Dobsonian reflector from Orion Telescopes. I purchased a small fleet of these instruments for student use and have had no regrets. They are simple, durable, and offer great viewing.

So what exactly is a 6-inch Dobsonian reflecting telescope? We’ll start with “reflecting.” Telescopes come in two basic types: reflectors, which use mirrors to gather light, and refractors, which use lenses. If you walked into Wal-Mart for a cheap telescope, you’d almost certainly be buying a refractor. Though there certainly are many refractors that are very high quality, you’re not going to get one like that at Wal-Mart. For a real quality refracting telescope, you would be spending several times more than you would for a reflecting telescope of similar size. If you’re looking for a serious but affordable starting instrument, stay away from refractors and start with a good reflector.

The next question is regarding aperture or (in simple terms) size. Generally speaking, the larger the diameter of a telescope, the better view you’ll have of objects. But also generally speaking, larger aperture also means larger price. Six inches offers enough light-gathering power to easily showcase Saturn’s rings or the moons Jupiter, hone in on the Moon’s craters, or (in dark skies) reveal distant nebulae and galaxies.

Next, you need to consider how the telescope is mounted. As it turns out, pointing and holding the telescope steady is one of the most important parts of getting good views (and not getting incredibly frustrated). There are lots of different ways to mount a telescope, but the type known as a Dobsonian mounting is the sturdiest and easiest that I’ve worked with. A Dobsonian mount makes it very easy to point the telescope to an object in the sky (especially if you spring for a simple laser-finder) and to keep the object in sight and steady once found. And if you’re observing with students or young kids, having a telescope that is on a steady and solid mounting is crucial.

Once you have your telescope picked out, the second step is to get a handful of eyepieces to use with it. Eyepieces magnify the image of the telescope, with the general rule that for a specific instrument smaller eyepiece focal length yields higher magnification. If you’re looking at large objects like the Moon or star clusters, you’ll want to use an eyepiece with a longer focal length (e.g., 25 mm). Then, when you want to zoom in on lunar features or try to split very tight double stars, you use an eyepiece with a shorter focal length to magnify the view. Most telescopes come with two or three eyepieces, and this is usually plenty for the beginner.

Finally, you need to know how to find the objects in the sky you want to view. I tend to eschew computerized mounts that point the telescope for you or tell you where to point it, because I think part of the fun is becoming familiar with the night sky yourself. But you’ll need some good resources to get you started. A quality star atlas is a must (I use the Cambridge Double Star Atlas), but it’s not much to go on if you’re just beginning. I’ve found James Mullaney’s Celestial Harvest to be an excellent guide to highlights in each constellation, and a tool like Guy Ottewell’s Astronomical Calendar (which unfortunately won’t be published after this year) lets you know what planets and constellations to spot when.

Then comes patience. Wait for clear nights and determine what constellations will be overhead. Do a bit of reading before you head out (or take a red flashlight with you to read at the telescope) and simply try to become familiar with the objects in one or two constellations at a time. Don’t feel like you need to learn the entire sky immediately. This month, for instance, Leo is a great place to start, from the lovely double star Algieba in the Sickle of Leo’s mane, to Jupiter and its moons just below the constellation (always a wonderful sight to start with), to the sweep of galaxies beyond Leo’s tail (though you’ll need to get away from the city lights to really appreciate these).

You’ll be amazed at what passes over your head each evening, generally unappreciated and unobserved, but within reach with a simple, good instrument.

This column first appeared in the Kankakee Daily Journal.

March Skywatch

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I’ve been promising a column for a couple months now that offers a basic introduction to telescope optics and usage. I plan to keep that promise, but exciting news keeps breaking out in the astronomical world. Last month it was the alignment of the planets in the early morning skies and the announcement of the possible existence of a new, ninth planet in the solar system. Now it’s even bigger news, as scientists have reported the first confirmed detection of gravity waves, which not only provide a further confirmation of Einstein’s theory of general relatively but more importantly have opened a completely new avenue for learning about the universe.

Up to this point in our history, everything we’ve known about distant objects in space has come from light, whether telescopes set up in backyards or research observatories on mountaintops or even instruments beyond the surface of the Earth like the Hubble Space Telescope. All of these gather types of light (which includes all portions of the electromagnetic spectrum, from the visible light we see up to high-energy gamma rays and down to low-energy radio waves). Light can tell us a lot about the universe, from the velocity of galaxies to the chemical make-up and temperatures of stars. Until now, all discovery related to the distant universe has been through studying light.

But a century ago Einstein predicted that there may be another means of learning about the universe. According to his theory of general relativity, massive moving objects should give off gravity waves, distortions in space that spread outward at the speed of light like ripples on a pond. These waves would be a completely new way of giving us information about objects in space. It would be as though having only before seen distant objects in space, now we would be able to “hear” them as well.

The problem was that gravity waves would be incredibly, almost unimaginably weak and thus very, very hard to detect. As a gravity wave moves through space, it contracts space slightly along one direction while stretching it in a perpendicular direction. This contraction and stretching is tiny, amounting to something like a thousandth of the thickness of a single proton. To detect such miniscule variations in length, scientists have had to build some of the most sensitive detectors ever.

How do you detect the warping of space caused by gravitational waves? There are several detectors around the world, but the two in the U.S. that detected this first confirmed signal (which passed through the planet—and all of us—last September) were the twin detectors of LIGO, the Laser Interferometer Gravity wave Observatory, located in Washington state and Louisiana. LIGO reflects a beam of light down two 2.5-mile tunnels at right angles to each other and by analyzing the beams can detect a tiny difference in the lengths of the tunnels caused by gravitational waves. This past September they both received a signal, and after months of analysis scientists were confident that it was indeed a gravity wave.

Aerial5
Aerial view of the LIGO Hanford Observatory, courtesy LIGO Image Gallery, http://www.ligo.org/multimedia/gallery/lho.php.

This particular signal appears to have come from two black holes billions of light years away in the process of colliding and merging to form one larger black hole. Scientists are able to predict how such an event would “sound” (that is, what sort of gravity waves it would give off), and the signal detected matches this prediction. Scientists are also able to triangulate using the detection at the two different sights to get an idea of where in the sky the signal came from, though it’s far too distant to observe with visible light.

But that’s exactly the point: with this confirmation, we now have a completely new way of observing the universe. We’re in a similar situation to when Galileo first turned a telescope—at the time a completely new scientific instrument—to the heavens. We have a new tool, and we’re not sure what we’ll discover.

Yet our very first observation has already shown us something exciting: double black holes that eventually collide have long been predicted but never before observed. It turns out the very first thing we’ve “heard” with our new ears on the universe is itself something new.

This column first appeared in the Kankakee Daily Journal.

February Skywatch

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5-planets

It’s been an exciting month for skywatchers! Last month I talked about some of the easy sights for backyard telescopes in the constellation Orion, which is looming large in our evening skies. The first couple weeks of February though, offer an even more impressive naked-eye sight in our morning sky: the possibility of glimpsing all five visible planets arranged in a straight line across much of the sky. The arrangement is best right now and will continue throughout the first week of February.

Standing outside before dawn, look to the east. Venus is bright above the eastern horizon, and if you have a clear view you may catch elusive Mercury even lower toward the Sun’s glow. Saturn is above Venus to the south, with Mars riding high in the southern sky. Jupiter is the bright object beyond Mars, toward the southwest. Altogether, the planets make a lovely arrangement that spreads across nearly the entire southern skies. The best time to look for them is just before sunrise, around 5:30 to 6:30, at which time the Sun’s glare begins to wash them out.

The mornings of this first week also bring an additional sight to the arrangement: a lovely slender crescent moon which passes by Mars on February 1st, is near Saturn by the morning of the 3rd, and moves down toward Venus on the 5th. An arrangement like this, with all the planets neatly in a row along the ecliptic, is fairly rare, so make an effort to rise early and take a look at this vista of the closest worlds of our solar system.

I mentioned last month I’d spend this column talking about telescope basics, but planetary happenings are enough to push that back a bit. Besides the arrangement of visible planets, astronomers grew quite excited this week with news of new evidence that might indicate the existence of an undiscovered ninth planet in our solar system.

When you look up at the pre-dawn sky this week, you can see all the visible planets in our solar system, which are all the planets that were known throughout most of history. It was only in the late 1700s that we began to realize there were other planets in our own backyard, and this most recent announcement may herald that our family of planets is about to expand again, for the first time in over a century.

All of this obviously makes astronomers pretty excited but also cautious, as there have been lots of false claims for Planet X in the past.

Until William Herschel stumbled upon Uranus in his telescope sights in 1781 and subsequent calculations showed that it wasn’t something like a comet, Saturn was considered the outer boundary of our planetary system. As astronomers observed the new planet though, they eventually realized that something was causing it to speed up and slow down in its orbit. The French astronomer Le Verrier correctly deduced that this was caused by an additional planet in our solar system and predicted its location, and Neptune was thus discovered in 1846.

Since then, astronomers on and off have believed they’ve seen evidence in the motions of the outer planets to hint at other planets lurking out there in the darkness. It was while searching for such a world that Illinois native Clyde Tombaugh found Pluto in 1930. However, it was later realized that Pluto was far too small to be causing any gravitational perturbations and in fact the perturbations themselves didn’t actually exist.

But this is where things get interesting, because it turned out that Pluto was actually simply the first in an entire class of tiny, distant solar system bodies called Kuiper Belt objects. Indeed, it was the discovery of more and more of these objects—some farther away and more distant than Pluto—that eventually caused Pluto to be reclassified as a dwarf planet.

Now, two astronomers from Caltech have published a paper arguing that the orbits of a handful of Kuiper Belt objects show evidence for an even larger body, about the size of Neptune, in the far reaches of the solar system. The reasoning is similar to that which led to the discovery of Neptune: it appears as though a large, massive object is affecting the orbits of these objects. Mathematical modeling indicates these observations could be explained by a ninth planet.

Of course this doesn’t mean that it’s there for sure. That’s how science works: observations provide evidence, and scientists offer a theory or hypothesis to explain it. A good hypothesis is one that can be tested. And that’s exactly what’s happening now: telescopes are being trained toward the outer reaches of the solar system to see if this posited body does indeed exist. If it does, it should be large enough to spot in very large telescopes, despite its enormous distance.

And if it is spotted, the total number of planets in the solar system will go back up to the number we learned in grade school.

This column originally appeared in the Kankakee Daily Journal.

January Skywatch

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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.

December Skywatch

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The evening skies of winter bring one of the most familiar groupings of stars, Orion, known as a giant, hero, or hunter in cultures throughout history and visible at some point of the year from every inhabited portion of the globe. Orion carries within it several stunning sights for both the naked eye and telescope observer, and we’ll be focusing on this constellation both this month and next. In this column I’ll start with a naked eye orientation to the bright constellation, and next month we’ll zoom in on some of the features visible through a telescope.

Orion rises in our evening winter skies as a tilted hour-glass figure marked by brilliant stars. At the beginning of the month he’s well over the horizon in the east by 8:30; by the end of December he’s nearly halfway up the sky in the evening. Two stars mark his shoulders, three his belt, and two his knees. Fainter stars trace out his head, sword, and shield or club he holds extended to the west. Each of the bright stars would be remarkable on their own, but together they make the constellation impossible to miss and twinkle fiercely low in the sky on crisp cold evenings.

The two stars marking Orion’s top shoulders are Betelgeuse (reputed to be a corruption of the Arabic for “Armpit of the Giant”) and Bellatrix (of recent Harry Potter fame—ask a fan what other characters appear in the winter sky). Betelgeuse has an unmistakable pale orange hue, which flickers beautifully when it’s low in the east. The stars in Orion present a snapshot of stellar evolution, and Betelgeuse is the old man in the crowd.

Betelgeuse is a dying star, a red supergiant near the end of its life. During this period of a star’s life it balloons to enormous sizes and can go through periods of instability, its tenuous radius heaving in and out like a slowly beating heart. Betelgeuse is thought to range from a radius of 800 million miles down to 480 million miles, which means at its smallest its surface would still extend beyond the orbit of Jupiter if it took our Sun’s place in our own solar system. Its density though is so low it’s less than a ten-thousandth of the density of the air we breathe, literally a “red hot vacuum.” It’s bleeding off this thin outer atmosphere into space, a dying giant lying just over 500 light years from Earth.

It’s fitting Orion is known as a giant in mythology, because the constellation is full of them. The star marking Orion’s knee opposite Betelgeuse, and providing a bright white-blue contrast to Betelgeuse’s pale orange glow, is Rigel. Rigel is one of the most luminous objects in the entire galaxy, outshining our own Sun by a factor of tens of thousands and at a distance from us of about 750 light years. Though it’s a supergiant like Betelgeuse and therefore has left the “middle age” that characterizes stars like our Sun, it’s younger than the pale orange star. And because more massive stars age more quickly, it’s likely younger than our Sun as well. Supergiants like Rigel (thought to be about fifty times the size and mass of our Sun) live short, hot, bright lives.

The stars in Orion’s belt, going from west to east, are Mintaka, Alnilam, and Alnitak. The star marking the remaining (eastern) knee is Saiph (meaning “Sword” though it’s far from the region of the constellation known as the Sword of Orion). All of these stars are giants or supergiants as well. What makes Orion such a rich area in space for the formation of these bright, young stars?


Image by Mike Hankey, http://www.mikesastrophotos.com/nebula/m42-the-great-orion-nebula/

The answer is the huge clouds of nebulosity that spread throughout this entire constellation, dark and invisible. Though hundreds of times emptier than the best vacuum we can produce on Earth, these clouds stretch for hundreds of light years and contain enough mass to form thousands of Sun-sized stars, as well as a fair amount of giants. And that’s exactly what has been happening for millions of years in this portion of the sky. We can see it in action in the visible part of the cloud, known as the Orion Nebula, a fuzzy smear of light in the center of Orion’s Sword, just below his belt.

We’ll zoom in on this nebula with a telescope next month, but a good pair of binoculars also offers quite a view. In the center of the nebula a tight grouping of four very young stars, known as the Trapezium due to their shape, are causing the surrounding nebula to glow. These gems at the center of the nebula are among the youngest stars visible in the sky, a scarce handful of millions of years old. The nebula that surrounds them is one of the most famous sights in the night sky. Though it lacks the intense color and detail you’ll see in processed images from large telescopes, it’s still quite impressive for backyard scopes.

The astronomy Robert Burnham, Jr., quotes the journalist and astronomer C. E. Barns as saying, “For who would acquire a knowledge of the heavens, let him give up his days and nights to the marvels of Orion. Here may be found every conceivable variation of celestial phenomena: stars, giants and dwarfs; variables, multiples; binaries visual and spectroscopic; clusters wide and condensed; mysterious rayless rifts and nebulae in boundless variety, with the supreme wonder . . . at its heart—the Great nebula.” I tend to agree. Now that we’ve introduced the constellation, next month we’ll take a closer look at what Orion reveals to backyard telescopes.

This column first published in the Kankakee Daily Journal.

August offers a look at Lyra

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When I talk to people about observing here in town, they often bemoan the fact that light pollution makes stargazing all but impossible from within the city limits.

Though it is true that observing from an urban setting doesn’t compare to an experience under truly dark skies, it’s certainly not the case that there’s nothing to see from one’s own backyard or even sidewalk.This month I’ll consider some of the sights in the constellation Lyra, which is almost directly overhead throughout August in early evening.

Lyra is a tiny constellation, but it holds a wealth of lovely double stars that are bright enough to be seen without a pilgrimage to the deep, dark countryside.

The constellation Lyra is easy to find on clear nights. Vega, its brightest star and the brightest star of summer, is nearly overhead at sunset. Vega marks one apex of the famous Summer Triangle, an asterism of three bright stars high in the summer skies. Lyra itself though is small formed of a triangle of stars attached to a larger parallelogram. Classically, the constellation was seen as a harp or lyre.

Lyra

My observations are made with a six-inch reflecting telescope from my own yard in Kankakee, but a smaller telescope will reveal these sights as well. You’ll want to use eyepieces that give a relatively low magnification. (I used about 40x. Calculate the magnification of your eyepiece by dividing your telescope’s focal length by the focal length of your eyepiece. A shorter eyepiece focal length gives greater magnification.)

Sometimes you want higher magnification, as when you’re viewing the planets or the Moon and want to see details, but for the following views a lower magnification is better.

Start your tour with Vega, especially if you’re new to stargazing. A single star doesn’t look much different through a telescope, but this will give you a chance to align your finding scope (if your telescope has one) and test your instrument’s focus. It will also give you an idea of the seeing conditions for the night. If you can focus Vega down to a brilliant, sharp point, and if you can see one or two of its dimmer companions in your telescope’s field of view, you should be able to spot the rest of the objects in this list.

Hop down from Vega to Zeta Lyrae, the dim star where the triangle meets the parallelogram. This is one of the many double stars in Lyra. Double stars are great targets for light polluted skies. Unlike nebulae or galaxies, they are fairly bright and thus easy to enjoy even from one’s own backyard. Through even a small telescope, Zeta Lyrae is revealed to be a wide, uneven double, and many observers report seeing a beautiful color contrast between the component stars.

Moving up to the third star of the tiny triangle that makes up the top portion of Lyra, we find Epsilon Lyrae, one of the most popular double star systems in the sky and an example of why some observers (like me) get so excited about double stars. At 40x you may simply see what looks like a wide pair of white stars. But if you increase your magnification (I used 130x), you’ll see that each of these stars is actually itself a pair of stars. The entire system is known as the “Double-Double.” You’ll need a steady eye and good seeing to split them, but you’ll know if you’ve succeeded by noticing the orientation of each tight pair: they’re inclined at ninety-degrees to each other.

Moving back to a lower magnification, each of the stars at the apexes of Lyra’s parallelogram is a treat.

Delta Lyrae is a wide double star in a diffuse cluster of stars. One of the components is a lovely orange in contrast to the surrounding blue stars.

Beta Lyrae also is a group of colorful stars. (The Ring Nebula is nearby, halfway between Beta and Gamma Lyrae. From my front yard, the Ring Nebula at 70x looked like a faint smoke ring, barely visible.)

But my favorite sight of all in Lyra is a bit off the beaten path and not terribly well known. It’s sometimes called the “Double-Double’s double,” but I think it’s actually nicer than the more famous Double-Double. It’s a pair of double stars, like the Double-Double, known as Struve 2470 and 2474. They’re dimmer than the pair that make up Epsilon Lyrae, but because the components are farther apart they’re easier to split. They also have more marked colors, the brighter components appearing yellow in contrast to the dimmer bluish companions. Moreover, by some cosmic coincident the pairs are orientated in the same direction so they indeed look like almost perfect twin double stars in a single telescope eyepiece. This view alone would be proof enough for anyone who says the city skies are too bright to hold telescopic wonders.

doubles
Struve 2470 and 2474, the “Double-Double’s Double,” image from bestdoubles.wordpress.com.

This column first appeared in the Kankakee Daily Journal.