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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.

November Skywatch

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Cass

This month starts with us relaxing our clocks back into a more natural rhythm with the Earth’s diurnal cycle, as we conclude Daily Saving Time the first Sunday of November and fall back one hour to Standard Time. This means our evenings get darker sooner, and the stars come out earlier for sky-watchers. It also means clock noon and solar noon once again roughly coincide. With evening arriving earlier, this month we’ll continue our series of looking more closely at sky objects that can be seen through sidewalk telescopes even from the streets and backyards of Kankakee.

The bright planets are still mostly grouped in the pre-dawn sky, but evening begins with the constellation Cassiopeia high in the northern sky. This recognizable, easy-to-find constellation hosts a pair of impressive multiple-star systems. Nearby are some lovely clusters and the famous Andromeda Galaxy (often unfortunately washed out by the light pollution in the skies above town).

Cassiopeia is shaped by turns as a 3, a W, an E, or an M depending on its orientation in the northern skies. In the early evening skies of November, it looks like an angular number 3, its bottom pointed down toward the northeast, with five bright stars marking the ends and each angle of its zig-zag shape.

To find our first double star, η (eta) Cassiopeiae, look for a fairly bright star halfway down the second “zag” of the zig-zag number three. This star is one of the most famous binary stars of the night sky. Though it looks like a single star, through a telescope it’s revealed as two stars—a bright yellowish star with a dimmer, reddish companion nearby. Measures of the relative positions of these stars over decades have revealed that this system is actually gravitationally bound, with an orbital period of about five hundred years. The system itself is about 20 light years away, but the two component stars are separated from each other by a distance of only 70 times the distance between the Earth and the Sun,

Once you’ve tried your hand at finding and viewing η Cassiopeiae, the next target in Cassiopeia is ι (iota) Cassiopeiae, a moderately bright star just below the constellation’s southernmost “zag.” Drawing a line through the southernmost two stars of Cassiopeia’s zig-zag, extending again about as far as the distance between the stars, will get you there. Through a telescope, ι Cassiopeiae will look like a smaller version of η Cassiopeiae. In fact though, it’s not a double but a triple system, with the brighter component actually itself a very close double star. Under high magnification and clear viewing, you may be able to just barely spot a small blue companion close to the yellow primary star. This entire triple system is about 160 light years from Earth.

If we go east from the bottom of Cassiopeia, toward the constellation Perseus, we’ll run into the Double Cluster (NGC 869 and 884). Visible with the naked eye in dark skies, these have to be “felt out” in brighter city skies. Once spotted though, they’re still an impressive sight. They are best viewed at lowest magnification in the telescope (or even with a pair of binoculars) and are examples of open or galactic clusters, composed of hundreds of young (six to twelve million years old) stars seven thousand to eight thousand light years away. In the telescope eyepiece they fill the view with dozens of bright, crowded stars.

Now, leaving the best for last (and omitting the fabulous Andromeda Galaxy which is nearby but washed out in city skies), we move to Almach, also known as γ (gamma) Andromedae, to the southeast of Cassiopeia, marking one of the feet of the constellation Andromeda. Almach is one of the most impressive double stars in the sky. Its component stars are a bit closer together than those of η Cassiopeiae but they have a brilliant, sharp color contrast between the yellow/gold primary and the dimmer blue companion star. Like ι Cassiopeiae though, one of the components of Almach (the dimmer blue star) is itself a close double as well, though I have not been able to separate these components in my backyard telescope. It doesn’t stop there though: one of those stars is in addition an even closer binary star with a period of only three days, making the whole system actually a quadruple star system.

I occasionally hear that the early evenings of autumn make people feel winter is finally here and sometimes even lead to seasonal doldrums. I maintain though that darker, earlier evenings are a fantastic opportunity to get out and learn about the dynamic, tangled lives of those bright stars above us. Hopefully these objects give you a place to start!

This column appeared first in the Kankakee Daily Journal.

October Skywatch

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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.

On blood moons and tetrads

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lunar eclipse
“Lunar eclipse April 15 2014 California Alfredo Garcia Jr1” by Tomruen – [1]. Licensed under CC BY-SA 3.0 via Commons – https://commons.wikimedia.org/wiki/File:Lunar_eclipse_April_15_2014_California_Alfredo_Garcia_Jr1.jpg#/media/File:Lunar_eclipse_April_15_2014_California_Alfredo_Garcia_Jr1.jpg

There is a lunar eclipse coming the end of this month, and depending on who you ask it is significant for different reasons. In fact, there has been a lot of hype about this particular eclipse (or rather, series of eclipses) in some Christian circles with the term “blood moon tetrad” often being used in conjunction with prophetic claims. I’m certainly not a specialist in Biblical prophecy, interpretation, or the history of Israel, but I can unpack some of the sensationalized terminology here and help sort out the science behind the hype.

Let’s start with the term “blood moon.” The popular press has recently started using this term to refer to a lunar eclipse. Lunar eclipses happen quite frequently, usually twice a year, when the full Moon passes into the Earth’s shadow. This causes the Moon to fade in brightness over the period of a couple hours and often take on a deep red hue due to the Earth’s atmosphere and the way it scatters light.

Consider how the sky looks during a sunset: even though the Sun is hidden beneath the horizon, the atmosphere bends the red portions of sunlight toward us. From the Moon, during a lunar eclipse, the Sun is hidden behind the Earth. The glow of a ring of sunsets casts that red light onto the Moon’s surface, making it appear duly reddish or “blood red.” This effect can be heightened if the Moon is near the horizon, depending on atmospheric conditions.

So what about “tetrad”? There are different types of lunar eclipses. If the Moon only moves partly into the Earth’s shadow, it’s called a partial lunar eclipse. The eclipse of this month is the last in a series of four total eclipses, in which the Moon passes through the darkest portion of the Earth’s shadow. A series of four total lunar eclipses without any partial eclipses between is known as a tetrad. This current tetrad includes the total lunar eclipse of last April as well as the eclipses of April and October of last year.

How rare are such series of eclipses? Glancing through my copy of NASA’s huge “Five Millennium Canon of Lunar Eclipses,” which included information on all lunar eclipses from 2000 BC to 3000 AD, I see that over the past thirty years there was a tetrad in 2003/2004 and 1985/1986 (as well as several lunar “triads”). According to the website EarthSky.org, there will be eight tetrads in the twenty-first century, while the years 1701 to 1899 had none at all. There were five in the twentieth century.

So what does this all have to do with Biblical prophecy? According to some sources, this particular tetrad is unique because it lines up with specific Jewish holidays. Last year, the first lunar eclipse of the series fell during Passover, as did the eclipse of April of this year. Last year the October lunar eclipse was during Sukkot, or the Feast of Tabernacles, which again corresponds with this month’s eclipse.

The important thing to remember though is that the Jewish calendar (unlike ours) is a lunar calendar; its months correspond with the actual phases of the Moon. Both Passover and Sukkot begin on the fifteenth day of the Jewish month, which usually corresponds with the full Moon. And because lunar eclipses only happen when the Moon is full, it’s not strange there would be occasional line-ups between these holidays and a series of lunar eclipses. How occasional? Again, according to EarthSky.org, this has happened eight times since the birth of Christ.

And here’s where the prophet interpreters come in, offering links between the years in which a tetrad of lunar eclipses corresponded with these holidays and important events in the history of Israel. But that’s the problem: history is a complex, messy business, and the human mind is hard-wired to find patterns everywhere, even where they don’t exist. Plus, these “significant events” are subjective: how widely do you want to interpret what events are actually important? The tetrad of 1493-1494 is linked to the expulsion of the Jews from Spain, for instance, but the order for the expulsion wasn’t signed in these years and the persecution lasted for decades. Making 1493-1494 especially significant is arbitrary. And other events that would seem to be significant are ignored: there was no lunar tetrad, for instance, during the Holocaust. Finally, I should add that this whole claim of prophetic significance is offered by individuals outside the Jewish community with little insight or regard into what that community would actually consider culturally or historically important in their own past.

In my mind, searching for codes in the night sky is much less useful than simply appreciating the grandeur of astronomy for what it is. And this month, regardless of prophetic forecasts, we have the chance to witness one of nature’s most impressive spectacles. The “blood moon tetrad” will conclude with the total lunar eclipse beginning the evening of Sunday, September 27th. (If you’re still looking for cosmic coincidents, here’s another one: my birthday is September 27th.)

The full moon rises in the east at sunset that evening. By 9:15 the Moon has begun to enter the darkest portion of the Moon’s shadow, marking the most vivid phase of the eclipse. It will be at its darkest at about 9:45, and the moon will begin to emerge from deep shadow at about 10:20. The Moon will not be completely out of the Earth’s shadow, however, until after midnight. As far as visibility, this will be an easy lunar eclipse to observe—taking place when the Moon is high in the early part of the evening. (Last year I had to make students get up before dawn to spot the eclipse.) So definitely take the opportunity to wonder and ogle, but try not to prognosticate.

This column first appeared in the Kankakee Daily Journal, August 28th, 2015.