Want a Glimpse of Eternity? Here’s How
Humans are storytellers. In a world, or universe, that is often emotionless and indifferent, we have a need to emotionally connect, fit in, figure out our place. Our grandparents tell us stories their grandparents told them that tell us who we are. Religion, a kind of story we tell ourselves, is based on explaining our surroundings in terms that would make our existence make sense. We watch TV and movies to see other people’s stories and relate them to ourselves, pursue science to find out the stories and histories of nature, and seek out stories in the form of education or news to help us understand certain things; perhaps that’s why you clicked on this post.
Stargazing is how the universe tells us its story. Our ancestors, long ago, gazed into the same skies as we do today, even linking them into constellations, telling stories about them, and projecting their human emotions onto the heavens. This mostly unchanging structure of the cosmos — to us — highlights the incredible scale of the universe and time itself, compared to our tiny little existence on a space rock in one galaxy upon billions. The contents of the night sky are nothing but the histories of celestial objects, their light ancient by the time it reaches us. Therefore, by stargazing, we can gaze back through time, allowing the universe to tell us its stories and our place in them. Though astrophysicists use complex methods and massive telescopes to study the stories of the cosmos in detail, all you really need is a night sky and your eyes.
Part One: The Groundworks (find a practical guide further below)
Celestial sphere and its lines
First, let’s go over the basic structure of the sky. Of course, the universe itself is three-dimensional, but seen from Earth at a glance, all the stars look the same distance away — two-dimensional — as if someone had painted them onto the heavens. For simple stargazing and orientation, it helps to picture the night sky as a sort of spherical structure, or globe, encapsulating the Earth, and all the constellations as permanent fixtures on it. The ancient Greeks actually saw the sky this way, and believed this sphere was rotating around the Earth, rather than the Earth itself spinning.
As you know, the Earth is a globe (flat earthers, look away); the top of the globe is the north pole, the bottom is the south, and around the middle is the equator. These points, as well as the latitudinal and longitudinal lines, translate onto the surrounding sky-globe. The North pole of this sky-globe, or celestial sphere, lies directly above Earth’s north pole, and so on. Rather than picturing yourself as an insignificant speck in the universe (which we are), this system helps you see the sky with respect to you, the observer, in the (fictitious) center of it all.
In the sky, latitude (vertical lines) is called declination (dec.), and is measured in degrees, just like on Earth. Similar to our planet, the celestial equator is at 0°. Going south, this number goes down until it reaches -90° at the south pole; heading north, it goes up, reaching (positive) 90° at the north pole.
Then there is the ecliptic: the representation of the Earth’s orbit around the sun. As our model is geocentric, the ecliptic shows the change in the sun’s position relative to Earth over the course of one year, and gives us a handy reference point when stargazing. It is slightly lopsided compared to the celestial equator, because Earth orbits at a slight angle (which gives us seasons).
As the planets were formed from material spinning around the young sun so fast that it flattened into a disc at this angle, most other planets move along a similar path to the sun in our skies (in fact, this is how the Zodiac cycle is determined; the constellations of the Zodiac lie along the ecliptic, and as the sun moves along it, the constellation/sign it ‘blocks’ is the current Zodiac month. The same goes for planets, which also follow the ecliptic; that’s why astrologists say things like ‘Venus is in Aries’, meaning that Venus is currently ‘in front of’ the Aries constellation).
The sky’s version of longitude (horizontal lines on the globe), called Right Ascension (RA), is a little more complicated. The zero point for longitude on Earth is the vertical Prime Meridian line, passing through Greenwich, London. The celestial RA’s zero point is similar, but is defined by the point of vernal, or spring, equinox: where the sun crosses the celestial equator on the first day of spring in the north. To make things more confusing, RA is expressed in time: the sphere’s 360° are divided by the 24 hours in a day — so 15° is equal to one hour. As opposed to the declination values, where the poles are the maximum value, RA starts at 0° — the celestial Prime Meridian — and is measured eastwards, going all the way around the globe and encompassing all 360° and 24 hours of time until it’s back where it started, and the values reset.
Let’s see an example: Vega, one of the brightest stars in the sky, has an RA of 18h 36m 56s and a dec. of +38° 47′ 1″. You may ask yourself why, as the Earth rotates, those coordinates stay the same; Vega isn’t always eighteen and a half hours away from a given point, after all. The thing is, the heavenly coordinates are as permanent as the ones on Earth; they are completely separate from one another. The RA and dec. lines are just set points in the sky used for guidance, nothing else.
Altaz system and orientation
Alright, we can now picture ourselves as standing on a spinning sphere inside a bigger, static sphere with gridlines and numbers on it. But although the dec. and RA lines in the sphere do not change, since the Earth spins, our position in relation to them does. We humans are able to see half of the celestial sphere at any given time; we would be able to see all of it, but as we are standing on Earth, the planet underneath us blocks the other half (though buildings, trees, etc. can block more). Here are the points on this hemispherical viewpoint:
· The observer stands in the center; half the celestial sphere — the sky — is above, the ground is below.
· The halfway point — where the Earth meets the sky — is the horizon.
· The point directly above the observer is the zenith.
· An imaginary line passing from north, through the zenith over the observer, to south, is called the observer’s local celestial meridian, which splits the sky in two.
· The angle between a given object in the sky and the horizon, with respect to the observer, is called the altitude
· The angle between north and the direction the object faces, also with respect to the observer, is the azimuth (for example, an object due South has an azimuth of 180°).
· This is known as the Altaz system, and is helpful for orientation.
Now picture yourself on an empty snowbank on the North Pole of the Earth; the northern celestial pole (NCP) is directly above you, and your local celestial sphere’s equator is parallel with the celestial equator. Conveniently, the star Polaris is located at more or less exactly at the NCP. According to our celestial coordinate system, Polaris’s declination is 90°: the maximum northern value (remember, declination and RA are permanent points in the sky). Standing on the north pole, Polaris would be exactly above you, so its altitude with respect to you, the observer, is also 90°.
But at Earth’s equator, your celestial sphere encompasses a completely different part of the sky. Here, the latitude value (Earth) and declination value (sky) are both at 0°. When you look north, Polaris is no longer above you, but directly on the horizon, at a 0° angle to you. Walk further south, and this value goes into the negatives; that is, you can no longer see the star. So you go to Paris, and spot Polaris at a 48.9° angle above the horizon again: the exact latitudinal coordinate of the city. Therefore, the NCP’s angle of altitude with respect to the observer corresponds with the observer’s latitudinal position on the globe, which is essential for navigation. Of course, in the southern hemisphere, the southern celestial pole (SCP) can be used the same way, but doesn’t come with a handy star pinpointing its position.
Seasons
As if things weren’t complex enough, depending on where you are, some constellations change with the seasons. In the 24 hours of a day, you are technically able to see the entire sky, but during the daytime, the sun and its light blocks out part of it (why you can’t see stars during the day). What you can and can’t see changes over the seasons. The Earth orbits the sun at an angle — that is what the ecliptic line represents. Because of this, depending on where it is in its orbit, either the upper (northern) or lower (southern) half of the Earth receives more sunlight a day. The only time this is equal is at equinox: when the ecliptic (the sun’s lopsided path in our sky-globe) lines up with the celestial equator. This change in daylight gives us seasons.
This means that as the Earth orbits the sun, the part of the Earth facing away from the sun and into the universe beyond at nighttime changes. If you stand at Earth’s equator and look into the night sky, six months later, the Earth will be on the opposite side of the sun, and the sky will have completely different stars. Similarly, the part of the sky that is obscured by daylight changes.
These disappearing stars are called seasonal stars, but there are some others, known as circumpolar stars, that remain visible in their corresponding hemisphere for the whole year. As they are so close to the celestial poles, they always remain at an angle where we can see them. For example, Polaris is visible all year from the northern hemisphere. In fact, the surrounding stars seem to circle around Polaris (the NCP) throughout the night, even though it is our planet that is spinning.
That’s not all, though. The familiar solar day is 24 hours long because it is based on Earth’s yearly orbit around the sun. A true day on Earth — the time it takes to rotate once — is not a neat 24 hours, as it turns out, but 23 hours, 56 minutes, and 4 seconds. This is called sidereal time, and is relative to the stars, not the sun.
Therefore, because we calculate our days based on the sun’s position, not the stars’, the stars rise about 4 minutes earlier every night. Over 30 days, a given star will rise 2 hours earlier; over the seasons, the entire sky might change. For example, in the Northern hemisphere, you can just see Orion setting behind the sun in April, before he disappears in the shrouds of daylight for the summer. But in the winter, all of those daily 4-minute differences have added up to make the hunter visible at night again.
So, how is all this useful to stargazing? While many apps and charts exist that will conveniently point out the location of every heavenly body or set of coordinates you want (and the real calculations are pretty complex), these concepts are useful to approximate or predict the location of a given celestial object.
Let’s go back to sidereal time for a second. Local sidereal time is star time at your location; when a star is directly overhead (at your local celestial meridian), its RA value (which is expressed in time) corresponds to your local sidereal time. How does this work? At vernal equinox (around March 21st every year), sun and star time align, so they are both briefly 00:00 at midnight. But a star day is 4 minutes shorter than a sun day, so a star overhead at 00:00 will return to that exact position 23 hours, 56 minutes, and four seconds later. When a star with an RA value of 6 hours is overhead, you know that it is 6 o’clock in star time (for practical purposes, though, it is probably easier to just google your local sidereal time according to your location).
Once you know your local sidereal time and have the coordinates of a star you want to see, you can ballpark an estimate for when it will be directly overhead. Just subtract the star’s RA value from your local sidereal time — the result is how long it has been since the star has passed overhead, known as the local hour angle (if you get a negative value, the star has yet to pass your local celestial meridian).
To find the star, you can convert the local hour angle to degrees by multiplying the hours by 15. Then, you can use your hands and fingers to roughly measure out the degrees of the sky until you find the star, using the coordinates of your celestial meridian as a starting point. Just remember that the local hour angle (as it is based in sidereal time) changes as the Earth rotates, so this will only work at the corresponding sidereal time.
Here are some basic measurements (all with the hand stretched out at arm’s length; you can use these vertically or horizontally):
· The little finger’s width is about 1°
· Three fingers’ width (first, second, and ring) is about 5°
· The fist’s width is about 10°
· The outstretched first finger and pinky (rock’n’roll horns) are about 15°
· The outstretched thumb to pinky (surfer shaka sign) is about 25° — also the span of the Big Dipper
If you don’t want to bother with local hour angles, you can use this handy calculator to find stars; just input your location, date, and the star’s RA and dec. values, and it will tell you the altitude/azimuth values (in degrees) of the sky you need to look in. Then, simply use your fingers to find it. Similarly, if you have a reference point with known values and can see it in the sky, you can use your fingers to get the altitude/azimuth values of other bodies; you could even calculate its RA value (calculating declination would only be possible if you were standing at the poles). However, many stargazing apps exist if you don’t feel like dealing with the numbers.
Though the cosmos speaks a slightly different language than we are used to, we can learn this language to interpret it and not only learn from it, but simply enjoy the communications. Of course, it is possible to stargaze without understanding these things; however, using a simple roadmap can be helpful to not get lost. It is important not to forget the profound complexity of our universe while using this generalized, two-dimensional system, but the extreme simplification necessary for us to keep track of it only underlines just how above our heads (literally) the cosmos is. Perhaps, consider the model as a sort of Rosetta’s Stone to help you navigate the universe and try to understand its endless fascinations.
Part Two: The Practical
Now that we’ve gone over the basics of the language of the cosmos, we can start reading its story. So, what are some good heavenly bodies to start with?
Circumpolar (year-round) stars and constellations *Note that these may be barely or not visible at or near the equator; but at the poles, most stars are circumpolar*
Northern Hemisphere
· Big Dipper. Easily the most identifiable constellation, it consists of seven stars in the shape of a pot or spoon. It is part of the larger constellation Ursa Major (Big Bear), which is not quite as obvious. Since it is a northern circumpolar constellation, look towards the north to find it.
· Polaris: the North Star, signifying true north. It is not very difficult to locate, but not really obvious either. Find it by looking at the unignorable Big Dipper; focus on the two outermost stars on the end of the bowl part. These are called the pointers. Multiply their distance about five times in the direction opposite the ‘bottom of the pot’, and you’ll find Polaris.
· Cassiopeia: the Queen of Ethiopia, and an M or W (zigzagged, in any case) shaped constellation. Once you find Polaris from the Big Dipper, keep going along that line for around the same distance (and a bit to the right).
· Little Dipper. Once you’ve found Polaris, you’ve automatically found this group of stars (part of the constellation Ursa Minor, Little Bear). Similar to its big brother, it is also ladle or pot shaped. Polaris constitutes the outermost star on the handle of the pot.
· Vega: one of the brightest stars in the sky. It is part of the tiny constellation Lyra (harp), is 25 light-years away, and three times the size of our sun. To find it, once again get to Polaris from the Big Dipper; when you reach it, follow a straight line in the direction of the Little Dipper slightly longer than that from the Big Dipper to Polaris. Vega is so bright that it’s not to be missed.
· Andromeda: the nearest (big) galaxy, and the most distant object visible with the naked eye. Just about everything we are able to observe from the Earth is within our own galaxy, the Milky Way. Andromeda is 2.5 million light years away; that’s like looking 2.5 million years back into time. Alarmingly, it is hurtling towards us at 110 kilometers per second, but will only merge with our galaxy in about 4.5 billion years; what humankind will look like then is anyone’s guess, but it’ll be a spectacular view. Andromeda can be spotted by taking the second ‘point’ of Cassiopeia’s ‘W’ and following it to the right. It’ll look like a faint little smudge in the sky.
Southern Hemisphere
· Crux, or Southern Cross: a tiny yet mighty constellation. As its name suggests, it is cross or kite-shaped, consisting of five bright stars, and has made its way onto several flags of southern countries. Unfortunately, the southern hemisphere does not have a Polaris-like indicator of true south, making navigation a little trickier, so you might need a compass for this one. However, the foot of the crucifix points downwards towards the southern celestial pole. So, look south, and the distinct shape is quite obvious.
· Jewel Box cluster: a small collection of stars to be seen next to the star at the east point of the crux. Though its individual stars can be seen with a telescope, you can see a blurry shape with the naked eye.
· Coalsack nebula: a dark patch of the sky consisting of light-absorbing dust. It is right underneath the Jewel Box, and is obvious due to the patch’s lack of stars.
· To the east of the Crux are the southern pointers: two bright stars in line with the top of the crucifix. If you connect them and draw a perpendicular line from the middle point the south, that imaginary line will intersect with that from the Southern Cross. Directly below this intersection is the Southern Celestial Pole
o What is perhaps more interesting about the pointers (part of the constellation Centaurus) is that the brighter of those two stars, Alpha Centauri, is a star system only about 4 light-years away from us, making it our closest neighbor. It consists of three stars: Alpha Centauri A, B, and C. A and B are sun-like and slightly further away. C, a red dwarf known as Proxima Centauri, is the closest star to the sun. Though it has only 12.5% of the sun’s mass, three exoplanets orbit it; one of these is in the habitable zone, so it may be suitable for life. Even though Proxima Centauri alone is too faint to see with the naked eye, its two brighter sister stars make the system the third-brightest star in the night sky.
· Centaurus: the centaur. Once you’ve familiarized yourself with the pointers, you can see them as the front two ‘hooves’ of the centaur (he is facing towards the east of the crux). The two back legs are on the west of the crux; the closer one is pretty much parallel with the bottom star of the crucifix. His head is more to the northwest of the crux; he kind of looks like he’s waving his hands around his head.
· Carina: the keel. This constellation used to be part of the bigger Argo Navis constellation: the ship of the Argonauts. It is to the west of Crux, and might have been hard to spot were it not for the star Canopus: the second brightest star in the sky. Canopus is the outermost star of the constellation; from there, it takes on a sort of question-mark shape.
Seasonal objects *Note that depending on your hemisphere, some constellations may appear flipped*
· Orion: the hunter. He is best visible in the winter from the north, and in summer from the south. To spot him, look for the three bright stars in a row that form his belt, and the hourglass-like shape around it. He appears to be headless, holding a bow in one hand and appearing to have just released its string with the other. He is located on the celestial equator and rises high in the sky during peak visibility.
o Within Orion lies one of the most infamous stars of the galaxy: Betelgeuse. A red giant 1400 times the size of our sun, it is expected to go supernova within the next 100,000 years (not much time in cosmic terms). It is located at Orion’s left (as seen from us) shoulder, and appears reddish in the sky. Its brightness also varies as it sometimes gets concealed by a dust cloud.
o Another bright star in Orion is Rigel, a blue supergiant star 79 times the size of the sun. It lies underneath the rightmost star of the belt, making up Orion’s right foot (from our perspective).
· Orion, or rather his belt, is useful to find the brightest star in the sky, Sirius. Simply follow the line the belt makes to the left, and Sirius is not to be missed. The star is only 8.6 light years away from us, and visible during roughly the same times as Orion.
· Sirius makes up part of the constellation Canis Major (big dog), earning it the nickname ‘dog star’. It marks the chest of the dog, between its head and legs. Its visibility is also similar to that of Orion.
· The Milky Way: our home galaxy. It looks like a massive ghostly veil across the sky — our planet is located in the ‘suburbs’, or outer areas of the galaxy, so we are seeing the Milky Way’s galactic center from its side. Its intensity depending on the surrounding darkness — it is very difficult, if not impossible, to see in the city. Its vastness means that it is visible throughout the year, but every place has a so-called Milky Way Season when the extraordinary galactic center is not obscured by daylight; here is a handy guide for determining it for your location. In general, though, it lies to the south when you are in the north, and the other way around.
Planets
Planets, unlike stars, are not stationary objects on the celestial globe; their RA and dec. values change. But they follow the ecliptic: the path of the sun. Therefore, keep track of the sun’s path that day (remember that the sun’s path changes with the seasons). The moon’s path will do too, as it differs only 5° from the ecliptic. Another important note: planets are large and bright, but do not twinkle like stars. Their brightness also changes according to their current distance from Earth, and not all of them are easy to spot. Here’s a quick guide:
· Mercury. The smallest and closest planet to the sun, it follows the star’s movement closely, meaning it always appears at dawn and dusk (though the exact times vary). As it is located within our orbit around the sun — called an ‘inferior’ planet — we can use the sun’s motion to track it, though its proximity to the star makes it hard to see. In the evening, it sets in the west; in the morning, it rises in the east. It is a maximum of 28° away from the sun, and often appears yellowish.
· Venus. As another inferior planet, Venus follows the sun’s motion in our sky. It is much bigger and brighter than Mercury, making it the third-brightest object in the sky; this is also helped by its highly reflective atmosphere, which Mercury lacks. Venus also appears at dawn and dusk, but with about 40° between it and the sun, making it much easier to see. Like the moon, Venus has phases, though these are only visible with a telescope.
· Mars. Orbiting outside of the Earth’s orbit, it is the first superior planet, which makes it much harder to track. Though its reddish hue means it is easy to identify, it is really only possible to find out its place in the sky by using a star chart app or looking up its current position. But if it is the right color, doesn’t twinkle, and is in line with the ecliptic, chances are it’s Mars.
· Jupiter. The king of the planets is very bright in the night sky, but again, as a superior planet, it is not always visible at night and requires additional research on its position. However, when it does make an appearance, it is white-reddish and quite bright. With enough darkness and a set of binoculars or a telescope, you can even make out some of its moons.
· Saturn. Once again, you might need to look up its current position before trying to find it in the sky. Despite it only being a little smaller than Jupiter, it is much further away, making it dimmer in appearance. It has a slight golden hue, but with the naked eye, its glorious rings are not visible from Earth.
· Unfortunately, Uranus, Neptune, and Pluto are too far away to be seen with the naked eye.
Meteor showers
· Perseids: occur when the Earth moves through a cloud of debris left behind by the passing of the comet Swift-Tuttle. The shower starts around mid-July and peaks mid-August (exact dates vary by year), and have about 100–150 meteors per hour. Their name comes from the point in the sky from which they appear to originate from — the radiant — which, for this shower, is the constellation Perseus. To find it, first find the W shape of Cassiopeia; Perseus should be adjacent to the first point of the W. Since these constellations are circumpolar in the northern hemisphere, the meteors are best visible there.
· Geminids: occur around December and usually peak around the 14th. With 120–160 meteors per hour, they originate from an asteroid, not a comet, and their radiant is located in the constellation Gemini. Gemini is not circumpolar and, similar to Orion, is best seen in the wintertime in the north, though some meteors can be seen in the south. It is located above Betelgeuse, the big red star on Orion’s left shoulder.
· Orionids: occur in October, peaking near the end of the month (varies by year). They consist of debris left behind by the passage of Halley’s comet. As its name suggests, the radiant is Orion, which, during this time of year, is best to be seen in the southern hemisphere; but again, meteors may be seen from the north as well. The shower generates about 50–70 meteors per hour.
Of course, there are many more showers; these are just the most intense ones.
I could suggest any number of apps, websites, binoculars, and telescopes for enhanced awareness, but even without those tools, the magic of stargazing lies in the simple act of looking deep into the cosmos and listening to its stories. It can provide you with an intrinsic sense of humanity: you can experience the same emotions and thoughts as our earliest ancestors as they mused over the same view. In fact, in the field of archeoastronomy, historians are able to determine alignments of ancient buildings with the same stars we have today. While some things have changed in the course of civilization — for example, Polaris only became the North Star in 500 AD — the vast majority of stars are so far away from us that the difference over this time, on a human scale, is barely anything.
Seen this way, stargazing gives you a perspective like no other; the immensity, sense of time, and our insignificance is humbling in the best way. It makes you think about all the other worlds we can’t even fathom; perhaps, someone else is lying there in a distant galaxy, staring at the stars, and pondering all the same things.
Therefore, while the methods and facts detailed here are useful for orientation, they should not distract from the pure wonder that comes from it. As described elegantly by Walt Whitman, with all the charts and numbers, it is important not to forget why they were invented in the first place. After all, the infinite inspiration that the universe provides us with is so enchanting that scientists spend their careers decoding its language. But like music — also a form of storytelling — you certainly don’t need to be an expert to be captivated by it. So, whether you understand the language or not, on the next clear night, listen to the song of the cosmos and appreciate what it is trying to tell you.
Originally published at https://notrocketscience.substack.com on December 11, 2022.
