For anyone looking for a hobby that is interesting, challenging, and free (yes, you heard right, FREE!), allow me to introduce you to the world of stargazing.
After the sun goes down, theres a big, wondrous, fascinating universe up there. And contrary to popular opinion, you really dont need a telescope to enjoy it. (More on telescopes later.) With nothing but your bare eyes, you can see stars, constellations, planets, clusters, meteors, the Milky Way, nebulae, our moon, and yes even a galaxy!
In this world of television, computers, the internet, electric lights, indoor air conditioning, and a plethora of electronic entertainment, we creatures of modern technology tend to be rather illiterate when it comes to identifying easily-viewed celestial objects. Many have heard the names of things like constellations and planets all our lives, but would be at a loss to identify them.
When I was in the third grade, I read in my school science book that five of the planets are easily visible to the bare eye! Excitedly, I showed the passage in the book to my teacher, anxiously awaiting details on how to find them. Alas, my poor teacher did not know. It would be many years before I finally learned how myself.
And so, in this article, I will introduce you to the night sky and point out several easily-identifiable objects that you should be able to find. Hopefully, you will be inspired so that tonight, you will step outside and see them for yourself!
Constellations & asterisms
Constellations are your road map to the sky. They are to the sky what continents are to the land; you use them to find your way around. All stargazing starts with constellations.
But first, a few facts about constellations. First of all, know that all constellations are not created equal. Its not a democracy up there. Some constellations are big and bright and beautiful and easy to spot; others are, shall we say, not. So the first thing the stargazer should do is forget about the dumpy ones, and concentrate instead on the good ones. In this article, I will only point the best of the best.
Secondly, know about both constellations and asterisms. Both terms mean a group of stars that appears to draw a pattern. The difference between the words is really one of bureaucratic officialdom. The International Astronomical Union (IAU) is the organization that puts its official stamp of approval on everything in the sky, and the IAU has divided the sky into exactly 88 official constellations. An asterism is simply a star pattern with no official recognition. However, this does not mean that constellations are better than asterisms. In fact, many asterisms are much easier to see and identify. Asterisms may overlap and intersect official constellations in all manner of ways. In this article, I will specify which is which.
So here we go, with a handful of some of my favorite constellations and asterisms, all of them visible from most of the Northern hemisphere at various times of the year:
The big dipper is one everyone should already know. What you may not know is that its really an asterism, part of the constellation Ursa Major, the Great Bear. The dipper resides in the northern part of the sky, and reaches its highest point in the springtime. It is also an important asterism in that we use some of its stars as pointers. The two stars at the end of the bowl can be used to find Polaris, the north star. The handle of the dipper is used to find the bright star Arcturus. Incidentally, forget about the Little Dipper; its not a good constellation at all.
Cassiopeia is also in the far northern sky, reaching its highest peak in the fall. It looks like a big W.
Cygus, the swan, flies through the Milky Way. Shaped somewhat like a cross, it is sometimes refered to as the Northern Cross. It contains the bright star Deneb as the tail.
The summer triangle is an excellent asterism. Its a great big 30-60-90 triangle, for all you math geeks out there (many asterisms resemble geometric shapes). In late summer/early fall, its high up in the sky. The 90-degree angle star - the brightest of the trio - is Vega, part of the constellation Lyra (the lyre, a harp-like instrument). The 60-degree star is Deneb from the constellation Cygnus, and the 30-degree star is Altair from Aquila (the eagle).
Orion is one everyone should know. Its most distinguished feature are the three belt stars, lined up in a row. It contains two important stars: Betelgeuse (pronounced beetle-juice), an orange-colored star in the upper left corner; its name means shoulder; and Rigel, and blueish star in the lower right corner; its name means foot. Orion is in the southern part of the sky, reaching its maximum height in the late winter.
Canis Major means the Big Dog. Its in the southern sky, just to the lower right of Orion in late winter, and really does look like a dog. Canis major contains the star Sirius, sometimes called the dog star, as the dogs neck. Sirius is numero uno, the #1 brightest star in the entire sky, and has a blueish tint.
Auriga, the charioteer. Heres one youve probably never heard of. But its very easy to spot. It looks like a pentagon, high up overhead in late winter. It contains the bright star Capella.
Scorpio. One of the zodiac constellations, and this one is a beaut. It really looks like a scorpion. Its low in the deep southern sky in the summertime. Observers in the northern U.S. or Europe might not be able to see all of it. Its main star is Antares, a reddish star; the name means rival of Mars, because when the planet Mars is nearby, they look quite similar.
Sagittarius. Another great zodiac constellation, but it doesnt look at all like a its intended representation of a centaurian archer. Rather, it looks like a teapot. Evidently, the ancient stargazers had a lot more imagination that us. Look for it in late summer, low in the southern sky. Sagittarius faces the center of our galaxy. The most dense region of the Milky Way is right about the teapots spout; it looks like steam.
Leo. This zodiac constellation really does look like a lion. Look high in the sky in the springtime. It contains the star Regulus, which means Little King, in the lions front paw.
Gemini. Under clear, dark skies, this zodiac constellation will look like two little guys standing here holding hands. But if your viewing conditions are less than ideal (which is just about anyone who lives in a city), the only part you will probably be able to spot are the two bright head stars Castor and Pollux. They are about 4 fingers apart, with your hand held at arms length. Gemini is high overhead in late winter.
Taurus. This zodiac constellation does not look like a bull, and in fact, doesnt have any kind of recognizable shape at all, other than a sort of a figure V at its heart. But it contains the Pleiades, a small but very visible star cluster, sometimes called the Seven sisters. In Japan, the Pleiades is called Subaru. Taurus also contains the reddish-colored bright star Aldebaran. Look for Taurus high in the sky in late winter.
The Great Square is a somewhat dim asterism viewed high in the sky in the fall. Forming an almost perfect square, it is comprised of two stars each from the constellations Pegasus and Andromeda. The Great Square, like the Big Dipper, is useful as a pointer to find other celestial objects such as the bright star Fomalhaut.
The Great Hexagon. I have saved the best for last. This asterism is a challenge to trace, but its worth it, as it contains six of the best stars in the entire sky. It stretches all the way from near the sourthern horizon to nearly straight overhead. Starting at it southern-most point, we have Sirius from Canis Major. Going counter-clockwise, next is Rigel from Orion, then Aldebaran from Taurus, then Capella from Auriga takes us to the northern-most point. Continuing, we have Pollux from Gemini, then Procyon from Canis Minor (the little dog). Canis minor is a celestial version of a one-hit-wonder; it only has one star visible to the unaided eye! Continuing counter-clockwise, we are now back at Sirius. The hexagon is visible in late winter. And if you are suspecting that late winter is the best time of the year for stargazing, you are correct!
Stars
Now with a good roadmap of constellations to navigate by, we turn our attention the main attraction: stars. And as we did with constellations, the focus will primarily be on bright, easily identifiable stars.
Star names. The first thing to know about stars is that they have names. There are several systems out there for naming stars.
The common name of a star is the name that has been referred to throughout the discussion on constellations. Examples are: Sirius, Capella, and Aldebaran. Most star common names have been around for many centuries.
Another star naming system is the Bayer name, after a famous astronomer, also known as the scientific name. The Bayer name consists of two words: The 2nd word is the name of the constellation where the star resides (actually the constellation name with an i suffix). The 1st word of the Bayer name is a letter of the Greek alphabet, starting with alpha for the brightest star, beta for the next-to-brightest, etc. Thus, Alpha Orioni would be the Bayer name for the brightest star in Orion, which has the common name of Betelgeuse.
The final star naming system is a catalog designation. Throughout history, astronomers, in conjunction with publishing companies, have compiled star catalogs. Some of the popular ones are HD (Henry Draper) and SAO (Smithsonian Astronomical Observatory). Thus a star catalog designation might look something like HD 12345.
And while were on the subject of star names, please dont get conned into buying a star. These companies, that are so eager to take your money, have absolutely no official status among astronomers. Only the IAU bestows names on celestial objects, and they dont sell naming rights. Besides, whatever star you buy will be far to dim to be seen without a monster telescope. If you want to name a star, just step outside and pick one. Its free, has exactly the same official validity as any one of these companies, and at least youll be able to see it.
Fixed positions. All stars have a fixed position on a giant, imaginary ball that astronomers call the celestial sphere. The celestial sphere has a north pole and a south pole, directly above the Earths north and south poles respectively, and an equator, directly above the Earths equator. The celestial sphere also has a grid coordinate system analogous to the terrestrial latitude and longitude system. In the sky, the lines running east and west are called lines of Declination, and like latitude on the Earth, are measured in degrees, where the equator is zero and the poles are 90. The lines in the sky running north and south that converge at the poles are called Right Ascension, broken into 24 units called hours, each of which is broken into 60 units call minutes. Thus, any star can be pinpointed by its position coordinates, which do not change.
Brightness & color. All stars have a brightness rating we call magnitude. The magnitude scale used by astronomers is an inverse logarithmic scale. Whoa, thats a mouthful! But its not as bad as it sounds. Inverse scales are all around us; for example, if you were to rate your five best friends, you would give the best one a rank of #1, your second-to-best one a rank of #2, etc; this is a classic inverse scale. And logarithmic scales are commonly used to measure the energy or intensity of something, such as the Richter scale used to measure earthquakes, or the decibel scale used to measure sound volume.
The original magnitude scale, established way back in the B.C. days, rated stars from 1 to 5, where 1 were the brightest and 5 were those barely visible to the unaided eye under dark, clear skies. Then when telescopes began being used by astronomers, they discovered that stars much dimmer than magnitude 5 existed, so they naturally extended the scale to numbers larger than 5. But at the other end of the scale, they began using more precise instruments to measure their brightness, instead of just eyeballing them as did the ancient observers. What astronomers learned were that not all magnitude 1 stars were created equal; some were considerably brighter than others. So they kept the original magnitude scale and simply extended it to the next smaller number, which was zero, and then kept going, into the negative numbers.
So today, Sirius, the brightest star in the heavens, has a magnitude of minus 1.4 (note the use of decimal numbers). The full moons magnitude is measured at minus thirteen! For reference purposes, the star Vega (part of the Summer Triangle) has a magnitude of almost exactly 0, and Spica (of the constellation Virgo) has a mag of almost exactly 1. For a mag of 2, all (but one) of the stars of the Big Dipper have mag 2.
There are exactly 9 stars on the celestial sphere with a magnitude or zero or less (brighter). There are 12 stars where the magnitude rounds to 1. There are about 50 with a rounded mag of 2; 150 with a mag of 3; 600 with mag 4; and about 1500 with mag 5. Thus, the number of stars in each magnitude group roughly triples with each increment.
Finally, stars have color. Most are white, but some have yellow, blue, green, orange or reddish tints.
List of Stars. So now, with a firm grasp of star properties, here is a chart of all the magnitude zero-and-above stars, listing in descending order of brightness. Assuming that you live in the U.S. or Europe, I have excluded stars that are too far south to be seen from your latitude, which is why there are some gaps in the chart.
The chart includes the root of the stars common name, and some notes on how to find it. You should begin memorizing this chart right away!
Rank Name Constellation color name means how to find it
1 Sirius Canis major blue scorcher southern-most star of Great Hexagon
2 Canopus Carina yellow south of Canis Majors front pay
4 Arcturus Botes orange bear keeper follow handle of Big Dipper
5 Vega Lyra blue descending 90 angle of Summer Triangle
6 Capella Auriga yellow cart driver northern-most star of Great Hexagon
7 Rigel Orion blue foot lower right corner of Orion
8 Procyon Canis minor yellow before dog between Sirius and Gemini
11 Betelgeuse Orion red shoulder upper left corner of Orion
12 Altair Aquila white flyer 30 angle of Summer Triangle
13 Aldebaran Taurus orange follower in the V of Taurus
15 Antares Scorpio red Mars rival just below scorpions claws
16 Spica Virgo ` blue ear of grain handle of Big Dipper past Arcturus
17 Pollux Gemini yellow southern head star
18 Fomalhaut Piscis Austrinus blue fish mouth follow 2 western stars of Great Square
19 Deneb Cygnus white tail 60 angle of Summer Triangle
21 Regulus Leo white little king lions 2nd paw from front
Planets
As mentioned earlier, all stars have a fixed, measurable position on the celestial sphere. But the ancient stargazers were puzzled by five star-like points of light in the night sky that broke the mold and seemed to wandered about. So they named them planets, after the Latin word for wanderer.
These five points of light are Mercury, Venus, Mars, Saturn, and Jupiter. Today we know that they, plus the Earth and scores of other objects, orbit around the sun. But your task as a stargazer is to learn how to identify them!
Here is a chart of some planetary statistics, the relevancy to be discussed below:
Planet Orbits sun Max magnitude
Mercury 88 days -1.9
Venus 225 days -4.4
Mars 1.9 years -2.0
Jupiter 12 years -2.7
Saturn 30 years +0.7
The Zodiac. We will first discuss where and when to find the planets. Know first that the solar system is flat, like a pancake. This means that the sun, the moon, the planets, and every object in the solar system, even the moons of the planets, appear to us Earthlings in the same narrow band, or belt. This circular belt has been traced through the heavens, and is called the zodiac.
The zodiac band was divided up by the ancient astronomers into twelve regions, each of these regions represented by a constellation. The word zodiac actually means circle of animals because most of the constellations represent animals. Your task as a stargazer is to learn the zodiac constellations, for that is where you will find the planets.
Here is a list of the zodiac constellations, ordered from east to west, with some viewing notes:
Name main stars best viewed viewing notes good?
Aries winter
Taurus Aldebaran winter Pleiades cluster *
Gemini Castor, Pollux winter 2 bright head stars *
Cancer spring Beehive cluster
Leo Regulus spring resembles a lion *
Virgo Spica spring
Libra summer has a green star
Scorpio Antares summer resembles a scorpion *
Sagittarius summer teapot asterism *
Capricorn fall
Aquarius fall
Pisces fall
Next, you need to know which planet is found in which constellation, and when. Heres a good website with that info:
http://www.astro.wisc.edu/~dolan/Planets/The chart at the above website will show that, for example, in the last quarter of 2006, Jupiter will be found in the constellation Libra.
The bad news is that many of the zodiac constellations arent worth looking at because they are too dim or too hard to trace. In the Zodiac chart above, I have included a Good column and flagged the better ones. If a planet appears in a not-so-good constellation, you will need to interpolate.
Inner versus outer planets. Mercury and Venus are inner planets because they are closer to the sun than is the Earth. Viewing inner planets is different from viewing outer planets in several ways. To begin, inner planets are only viewed either in the west right after dusk, or in the east right before dawn. (Anyone who says they saw Venus at midnight last night does not know what they are talking about.) All charts and guides for viewing inner planets will always say E for evening or M for morning.
Inner planets are best viewed when they are at elongation. This is when the Earth, the sun, and the planet are at their widest angle out of alignment. At elongation, the inner planet is at its highest peak above the horizon. And even then, we Earthly observers are only seeing the planet on edge. Only the rather small portion of the inner planet that is illuminated by the sun is visible. If you were to view one of them in a telescope, it would look like a crescent moon.
Heres a good website for finding when inner planets are at elongation:
http://www.jgiesen.de/skymap/MercuryVenus/The elongation chart at the above website would show that, for example, Venus will be at elongation on the evening of June 9, 2007. Venus is an easy planet to locate. With a solar orbit of 225 days, it moves relatively slowly among the constellations, and so appears on the zodiac finder chart listed on the website given earlier. It will be far enough above the horizon to be seen for many weeks before and after its elongation date.
Mercury, on the other hand, is very elusive. With a solar orbit of only 88 days, it doesnt stay in any zodiac constellation long enough to count, and so it does not appear on any zodiac finder chart. It never rises very high above the horizon, and even when it does, it doesnt stay there long. You have, at most, about a week before or after an elongation to get a view of it. According the website listed above, Mercurys first elongation in 2007 will be on the evening of Feb 7.
Outer planets, in contrast have an opposition. This is when the sun, the Earth, and the planet aligns. Outer planets can typically be seen at any time of the night for many months before or after their opposition date. Here is a good website for obtaining opposition dates:
http://www.astropro.com/homeIE45.htmlThe above website would show, for example, that Jupiter will be at opposition on Jun 5, 2007.
What do planets look like? At first glance, planets dont look significantly different from stars. But notice the magnitudes in the Planetary Statistics chart above. Planets, for the most part, are considerably brighter than most stars!
Note, however, that planetary magnitudes are quite variable. It is greatly influenced by variables such at its distance to the Earth, and in the case of inner planets, by the angle of elongation.
For the ancient astronomers, Mars has caused the most intrigue among all the visible planets. The first reason for this is the color. All the other planets are a dull white; Mars is red. The second reason relates to timing. All the other planets are visible every year, at some point. But with a solar orbit of 1.9 years, it takes about two and a half years for the Earth and Mars to catch up with each other. Thus, Mars only makes an heavenly appearance every other year, or less.
Other Celestial Objects
So weve covered constellations, asterisms, stars, and planets. What else is there? Actually, quite a lot. And no article on stargazing without some discussion of:
The Moon. Our closest celestial neighbor does not get must respect among astronomers. We stargazers like our night skies nice and dark, and the moon is considered a bright nuisance. Thus, you might want to consider the moon phase before selecting a good night to stargaze. Here is a website to get lunar cycle data:
http://stardate.org/nightsky/moon/The Milky Way. On clear, dark nights, you should be able to see this dim, narrow band stretching across the heavens. You are looking edgewise at our galaxy. The word galaxy, in fact, comes from the Latin work for milk.
Like the solar system, our galaxy is flat, like a pancake, so when you look down the edge, you are looking through its densest parts. All published constellation charts will show it.
The center of the Milky Way is toward the constellation Sagittarius.
Comets. Comets are part of the solar system. However, they are the non-conformists; unlike other members, they are rarely found on the solar system plane. That means they could be seen anywhere in the sky, not just in the zodiac. Comets that are bright enough to be seen by the unaided eye, however are very rare, averaging about one a decade or so.
Deep Sky Objects. This broad category includes galaxies, clusters, and nebulae. By definition, a deep sky object is outside of the solar system; thus, comets are not included. Only a small handful of deep sky objects can be seen with the unaided eye, and most of these require exceptionally dark, clear skies.
Here is a list of some of the brightest deep sky objects:
Object Type common name constellation magnitude
M45 cluster Pleiades Taurus 1.2
M44 cluster Beehive Cancer 3.1
M31 galaxy Andromeda Andromeda 3.5
M42 nebulae Orion Nebula Orion 4.0
M6 cluster Butterfly Cluster Scorpio 4.2
The M moniker refers to the Messier deep sky catalog, named after the French astronomer who was actually looking for comets. Deep sky objects, like stars, have lots of catalogs, but the Messier is very popular to this day.
The Pleiades cluster, also known as the Seven Sisters, is very well known and easy to spot.
The Andromeda galaxy is the most distant object in the heavens that can be seen with the unaided eye.
A good technique for viewing deep sky objects is to use what stargazers refer to as averted vision. The basic idea is that the most sensitive part of our eyes is not the center of the retina, but the area just next to it. Therefore, when viewing a very dim object, do not look directly at it, but rather, look just ever-so-slightly to the side of it, and it will appear brighter.
Telescopes
A common misperception is that a telescope is absolutely essential to see the night sky. In fact, many people, thinking that they or their children might be interested in astronomy, rush out and buy a telescope. An astronomy telescope is a wonderful tool, but there are a couple of important facts that a prospective purchaser should know. First, using a telescope requires considerable knowledge, skill, and patience. Secondly, a telescope of high-enough quality to actually see anything in good detail is terribly expensive.
As has been repeatedly pointed out in this article: there is much to see up there that you really dont need special equipment for. But if you find that you thoroughly enjoy stargazing, and would like to see more than your bare eyes can see, then and only then do you become a good candidate to purchase a scope.
An astronomy telescope is essentially a light bucket. While the pupils in our eyes will only open to, at most, about a quarter of an inch in diameter, a telescope lens (or mirror) is much, much larger, allowing it to gather considerable more light. Thus, when it comes to telescopes, diameter size is everything. The bigger, the better. (The worlds largest telescope, located in Hawaii, is over 30 feet in diameter!) However, by the same token, the bigger the scope, the harder it is to haul it around and set it up. A scope so cumbersome to use that you never use it is not much of a buy.
Resources
There are many, many articles, books, magazines, websites, and other tools to help stargazers find their way around the sky. This article just covers the bare minimum; there is much, much more out there.
An excellent beginners book is The Stars by H.A. Rey, the author behind the Curious George series of childrens books.
The internet, not surprisingly, has an awesome wealth of information on astronomy. One of the very best sites is:
http://skytonight.com/Sky Tonight has a java applet called the Interactive Sky Chart, an incredible tool that will show you the sky at any place on Earth, at any requested date and time. The display includes the positions of the planets, the sun, and the moon. This is far and above the easiest way to know where the planets are!
To really appreciate the night sky, however, requires some serious memorization. You need to memorize the names and shapes of all the easily-identified constellations, and the list of the 21 brightest stars.
Happy stargazing!
David M. Woods, MBA, is a software developer in Houston, Texas. He is a life-long astronomy buff and teaches a class in stargazing at a Houston school called Liesure Learning (
http://LLU.com)
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