Every “spot” on Earth has a corresponding “spot” in the sky. For instance, on the spot where you are now, directly overhead, is the zenith. There is only one zenith where you stand. No two spots share the same zenith. Every spot on a sphere “points to” a different location in the sky. Nobody shares your zenith.
Your Zenith is Unique
Imagine the boundary of your country as a set of these spots. These locations can be projected onto the celestial sphere. Projecting shapes of countries onto the sky can help you really “see” how large or small a country is. Seeing countries from the inside out helps to understand the shape of the Earth as a sphere.
That Star is Someone’s “First Star I See Tonight.”
When you see a star rising you are actually seeing a star that someone 6 timezones east of you sees directly overhead.
Sirius rises just before dawn (heliacal rising) in mid August (at latitude 40˚N). It rises earlier and earlier each day until by November it is rising at midnight. When people on the east coast of the USA see Sirius rising, people in Western Europe see the same star Sirius high in the sky at the meridian.
Dalle-2 Generated this image of a figure standing, wondering at the cosmos. Prompt: “gentle, happy 8 year old child, standing in a sunset forest, looking through a small, glass-covered hole in the earth that has stars deep inside, digital art, unsaturated colors” – Credit: Daniel Cummings
Heliacal rising.
Sidereal time.
Take a picture of the stars before the dawn every day.
Just before dawn, while the sky is still dark, and the stars are still out.
Tomorrow, the same thing, just before dawn, while the Earth still blocks the Sun.
Learning the Zodiac constellations in order is a great way to get familiar with the ecliptic and the celestial sphere. The Zodiac is not just for astrology – astronomers use the constellations of the Zodiac to name 13 regions of the sky.
Zodiac Constellations zoomed in on Ophiuchus – the “13th” Zodiac Constellation between Sagittarius and Scorpio. The constellation borders (marked red) show how astronomers divide up the sky into named regions.
Zodiac Constellations List
These are the Zodiac constellations in the correct order from Aries to Pisces.
Order
Mnemonic
Name
Description
Emojis
1
All
Aries
Ram
♈ 🐏
2
The
Taurus
Bull
♉ 🐄
3
Great
Gemini
Twins
♊ 👯♂️
4
Constellations
Cancer
Crab
♋ 🦀
5
Look
Leo
Lion
♌ 🦁
6
Very
Virgo
Virgin
♍ 👰
7
Lovely
Libra
Scales
♎ ⚖️
8
Shining
Scorpio
Scorpion
♏ 🦂
9
Orderly
Ophiuchus
Snake-wrestler
⛎ 🐍🤼♂️
10
Stars
Sagittarius
Archer
♐ 🏹
11
Creating
Capricorn
Goat-Fish
♑ 🐐🐠
12
Animal
Aquarius
Water-bearer
♒ 🚰
13
Patterns
Pisces
Fish
♓ 🐟
Table showing the order of the Zodiac Constellations, their names, descriptions, and emojis
Memorize the Constellations of the Zodiac in order
This mnemonic (memory device) can help you remember the correct order of the constellations of the Zodiac. This is the best way to memorize the order of the constellations of the Zodiac. It starts with Aries and ends with Pisces.
“All the great constellations look very lovely; shining, (orderly) stars creating animal patterns.”
Why does the Zodiac constellations list start with Aries?
When astrology was invented it was the same activity as astronomy – observing and cataloging sky objects and their locations) but over the years the two practices have become very different. Astrology is now concerned with how the movement of the skies affects humans while astronomy has become a science. Scientists build knowledge to make predictions about physical events.
During early astrology/astronomy times, the most important thing about the study of the stars was to know where the Sun, Moon, planets, and other solar system objects were located in relation to the steady, orderly background of stars.
Why does the order of the Zodiac constellations read right to left?
The Sun moving “through” Aries into Taurus over a month. Each frame of the animation is about 3 days.
The Sun, Moon, and planets seem to move “through” these 13 constellations in order through the year. Starting with Aries, let’s follow the movement of the Sun against the backdrop of the steady stars. The next constellation that the Sun “moves into” is Taurus. Taurus is to the east (left) of Aries! The Sun appears to move into the next Zodiac constellation about once a month.
Why did we add Ophiuchus to the original 12 Zodiac constellations?
Ophiuchus is a constellation, not an astrology “sign.” However, it is an official constellation that intersects the ecliptic. So, while astrologers do not consider this a Zodiac sign, astronomers include it because the constellation is located on the ecliptic.
The Ecliptic is a path in the sky that solar system objects follow
The solar system objects move generally west-to-east in a small band of the sky – this band of sky is called the ecliptic. All the Zodiac constellations are “on” the ecliptic and all the Sun, Moon, planets and other solar system objects move along the ecliptic over time.
There is another line in the sky called the celestial equator that is an imaginary line the rises from the equator of the Earth. The celestial equator and the ecliptic intersect at a “location” in the sky.
Right now in 2020 that intersection location is “in” the constellation Pisces.
The thin, diagonal line that connects the Zodiac constellations is called the ecliptic. This image shows the ecliptic intersecting with the celestial equator.
However, when astrology was created this intersection point was “in” the constellation Aries.
This image shows the intersection of the ecliptic with the celestial equator in the year 100 BCE.
This was known as the “First Point of Aries.” Astronomer Guy Ottewell writes about this imaginary point in the sky on his website UniversalWorkshop.
Summary
You can learn the order of the Zodiac constellations by using the mnemonic device shown in this article. There is a pathway in the sky that the solar system objects seem to follow. It is called the ecliptic. The Zodiac constellations are the 13 constellations lined up in the sky “on” this imaginary line.
The order of the Zodiac constellations is made because of the way the Sun, Moon, and planets seem to move east-to-west past these constellations in order during the year.
We start the Zodiac names list with Aries because the Zodiac constellations were first named thousands of years ago. At this time, the ecliptic intersected the celestial equator “in” the constellation Aries.
Earth Map in the Sky – Landforms as Constellations
Learn how to see the map of Earth in the starry sky.
Stars help us find our way. Stars are like a giant map in the sky that tells us where we are on the surface of the Earth. Sailors use them as a “map” to navigate the world. For thousands of years, the stars were stationary markers of latitude and longitude.
We are going to learn to map something new onto the sky: locations on the Earth! We can create an exciting new set of “constellations” out of the shapes of the continents on the Earth.
We live on a sphere so we can see half of the sky (a hemisphere) at any one moment. It’s easy to imagine half the Earth mapped onto half the sky. Keep reading to learn how.
A new way to experience life on a sphere. It’s an Earth map projected onto the starry sky. Image created by: Daniel Cummings
Zenith Stars
Wherever you are on the Earth, when you look straight up (toward your zenith), you might see one star, but there are a bunch of other stars within view. All of the stars you see in the sky are directly overhead some other place on the Earth. Every place on Earth has their own set of stars directly overhead – their “zenith stars.”
Look up at any star in the night sky; that star is directly over some place on Earth. There are hundreds of “faraway zeniths” up there.
World Zeniths – See the Map of the Earth in the Sky
Every star maps to a location on Earth and every location on Earth maps to a star.
If you live in the western hemisphere, you can learn to look up and “see” the land borders of the North American and South American continents visible, projected into the sky like a giant painting on a curved ceiling. You can learn to see even more landforms in the sky – you can learn to see the entire western half of the Earth projected in the sky.
Visualize Countries in the Sky
We can learn to see country outlines in the sky. The key is to imagine yourself at the center of the Earth looking out into space “through” a translucent Earth surface.
Here is a good way to visualize these countries-in-the-sky even when you are on the surface. Imagine that you can look up and see your location at the zenith.
When I do this, I see southern New York state, Long Island jutting out into the water like a long pier, and the wide Hudson River emptying past New York City. Eastward is the dark expanse of the Atlantic Ocean and low on the eastern horizon are the countries of Europe and West Africa.
Westward in the sky, I can see the outline of the west coast of the US. Then, there is a big blank space of the Pacific Ocean and a spot near the western horizon that is Hawaii.
The Map of the Earth in the Sky is Reversed
Map of Earth landforms as they map to the starry sky. Map is reversed because it is projected into the sky. The places named at the cardinal directions (N, E, S, W) are the locations where New York horizon stars are zenith stars. Image created by: Daniel Cummings
There is one odd thing about the map as you see it in the sky… it’s reversed – as if seen in a mirror! This happens because we project the map lines outward into space toward the stars. When we look at the map this way it’s as if we are “inside” the Earth looking outward.
The map of the USA covers about 58˚ of sky from east-to-west. 58˚ is about 2x pinky-to-thumb (spread out all your fingers of both hands and touch thumbs). Your left pinky tip should be on your zenith. If you are in New York or somewhere on the east coast, the right pinky tip will indicate the approximate western edge of the USA.
Physical Astronomy – Stars Map to Places on Earth
Physical Astronomy Activity Instructions to learn to see the Map of the Earth in the Sky. Faraway Zenith stars help us visualize what it is like to live on the surface of a sphere. Image created by: Daniel Cummings
Learn to see the zenith map in your sky using this Physical Astronomy technique.
Exercise 1: face south and point high in the sky.
Face south. Then, reach both hands straight up over your head and point above your head with both pointer fingers. You are pointing at your zenith. Now, bring both arms down until they are pointing one due east and one due west. You are pointing at two points in the sky that are zeniths for someone else.
When I do this exercise in New York, my left hand (the eastern) points at a spot in the starry sky that is the zenith star for someone in the country of Nigeria in West Africa. This is a location on the globe that is 6 time zones east. My right hand (the western) points at a spot in the sky that is the zenith for someone in the island state of Hawaii in the middle of the Pacific Ocean. This location is 6 time zones west of New York.
So, when I look at the eastern horizon sky I am looking at the starry sky that is already directly above a place 6 time zones ahead of me. I am looking at someone else’s zenith stars.
Exercise 2: Repeat exercise 1. But this time, face east.
Secret! You Can See a Star That Another Person Can’t
If you do this physical astronomy exercise right after sunset, the eastern and southern zenith locations are in night, but the western and northern sky points are over Earth locations that still have daytime.
This means that you can see the star that is at their zenith, but they cannot see that star. For example, Seattle still has 3 hours of sunlight left in their day so stars are invisible behind blue sky. The city of Yekaterinburg is on the opposite side of the world and just after sunset in New York it faces the Sun and has a bright daytime sky!
We are on the night time side of the Earth and we can see the current zenith stars of Seattle and Yekaterinburg – but people who live in these cities cannot see them! They have to wait to rotate to the night time side of the Earth to see stars.
Project an imaginary map of the Earth into the sky. The map has to be the correct size so that when it is viewed from a distance it “covers” the same distances.
If a map is too close, it is just the same size as the territory. So, we have to choose the correct distance to project the zeniths. As the zenith map “projector screen” moves away from the Earth we see more of the borders of the Earth. But, at some point the distance of the map corresponds exactly to the faraway zeniths.
Our question is: “How far away from the Earth do you have to be so the landforms (like the continents) have an angular diameter that is equivalent to their “actual size” in the sky?” How far away does our imaginary zenith map USA (about 3000 miles wide) image have to be to cover 58 degrees of arc in the sky?
The Earth is approximately 24,901 miles in circumference at the equator. If we can see half the sky from any point on the Earth, then we can “see” half the Earth projected onto the sky by the zenith map. That means that for 180˚ of sky we can “see” about 12,450 miles of the Earth’s surface projected into space. 12,450/180 = 69 miles. When 1 degree of arc spans 69 equatorial miles the image is “at” the correct distance.
1 Degree of Sky equals 69 Miles
So, at the equator every degree of sky covers about 69 miles in every direction. As you go towards the poles the longitude degrees (east and west) cover less and less zenith map distance, but the latitude degrees (north and south) always stretch 69 miles. Every 15˚ of sky equals about 1035 (69*15) miles.
The distance between your pointer finger and your pinky (when you hold your arm and hand stretched out in front of you) is 15˚ – so you are measuring about 1035 miles on Earth with that sky measurement. One pinky width is equal to 1˚, which is 69 miles of zenith map!
The Math – Inverse Tangent and Angular Diameter
There is a simple calculation that helps us determine how far away something needs to be to fill just 1˚ of the sky. Here we use just a tiny drop of trigonometry to discover the “tangent of 1 degree.”
The tangent of 1˚ is 0.017455. The inverse of something is when you divide 1 by the number you want to invert. So, the inverse of 0.017455 (1/0.017455) is 57.29. The inverse of the tangent of 1˚ helps us figure out the distance something has to be to appear to be 1 degree angular diameter.
So, 57.29 * 69 miles = 3,953 miles away! This is how far away the “map” has to be to show you your hemisphere of the Earth map. 3,953 miles is higher than low Earth orbit (LEO) satellites (lower than 1200 miles); it’s closer than geosynchronous satellites (at about 23,000 miles); and it’s about 1/60 the way to the Moon.
So, imagine that the Earth map is projected onto a screen – an imaginary celestial sphere, shell-shaped – that is quite close to the Earth and encircles us. It shows us our Earthen landforms and the oceans beside, superimposed in the sky.
Summary
We live on a sphere. When we look at out night sky we are able to see stars low on our horizon that are visible directly above someone else – one-quarter the way around the around the world in all directions.
If you live within 6 time zones of someone that means that you share some “simultaneous sky.” Anyone living further than 6 time zones away sees a completely different sky – unless you can see circumpolar stars that dip under the North Star. That means that you can see countries past the North Pole and down the other side of the globe.
Your zenith is yours – it is unique and changing all the time. Not even someone standing right beside you shares your zenith. You can use this idea of the zenith stars to comprehend the vast and mysterious experience of life on a sphere.
Webster’s 1913 Edition has this funny little entry that defines sporades:
||Spor”a*des, noun plural. [L., fr. Gr. spora`des. Cf. Sporadic.] (Astron.) Stars not included in any constellation; — called also informed, or unformed, stars.
Before that year there were wild places in between constellations where stars could exist. After 1930 all of the stars had been pinned down – like rows of dead butterflies. Every star is now “inside” a constellation boundary.
We don’t need this word sporades any more; all the stars have been captured.
Have you ever looked up and wondered how many stars are in the sky?
How many stars are in the sky right now?
It’s a simple question with a surprising answer!
This question has layers of answers – the most common answer is “it depends” – it depends on where you are, what part of the year it is, what time it is, and most of all… how dark are your skies and how powerful is your telescope?
Let’s start with a quick (approximate) list of how many stars you might be able to see at once at night under “normal” conditions with no telescope. (The details on these calculations are near the end of this article.)
How many stars can I see at night:
The most stars anyone can see from the Earth (no telescope): 3700
The number of stars can you see at a dark sky site: 2000
How many stars can I see in my suburban yard: 200
How many stars can I see in a large city: 20
Another trick answer to “how many stars are in the sky?” is: “all of them!” All of them are in the sky, but they are just not visible to you “right now” for one reason or another.
I know, these answers are not quite what you may be looking for. Let’s look a little bit deeper by starting our search for how many stars can I see at night.
Quiz – How many stars are in the sky, how well do you know them?
Let’s start by taking a short quiz (answers are just a scroll away, so don’t peek!):
Which star is the brightest in the sky?
Which star is the closest to us?
Which star is the first one discovered to have a planet supporting life?
Which stars have a solar system?
Scroll down a bit to see the answers to this first part of the quiz.
While we are waiting to scroll (and to keep the peekers from peeking!)… let’s talk a little bit about how professional astronomers count the stars.
Annie Jump Cannon – Harvard star counter extraordinaire
Annie Jump Cannon – Harvard University Image: Public Domain
Have you ever tried to count the stars? If you have, you probably gave up at some point because there were too many to keep track of.
In the early 1900s there was a tenacious Harvard astronomer named Annie Jump Cannon who didn’t give up counting! In fact, she counted so many stars that she almost lost track.
To keep everything organized she started categorizing them by their colors. She invented the spectral classification system – O,B,A,F,G,K,M – and personally classified over 350,000 stars!
Her method of categorizing stars is still in use today.
The answers to the star Quiz
The Sun compared to other stars. Image: Daniel Cummings
The number of stars in the sky is…
SPOILER ALERT! – Here are the answers to the quiz above!
The quiz is a trick quiz because the answers to are all “the Sun.” If we don’t include the Sun in this quiz then we get very different answers and the answers are:
Sirius is the brightest star (it is almost as bright as Jupiter),
Proxima Centauri is the closest star (it is 4.22 light years away),
No star’s exoplanets have yet been proven to support life – the Sun is the only star so far to host life.
There is only one solar system. The answer to question 4 is truly a trick question: “No other stars have a solar system… because only one star is named “Sol” … the Sun! The “Solar System” is named after Sol – the Sun. See: Sol+ar = Solar. Other stars would have planetary systems named after the star. For instance, there may be a “Sirius-ar system” that hosts a planet like Earth.
The Known Universe
Ok, now you are done with the quiz let’s get counting stars. Go outside, look up, start counting!
Artist’s conception of the known universe. Credit: Pablo Carlos Budassi via Wikipedia
Before, we start… There is one tiny problem with counting the number of stars. Even with the best tools humans have invented, we can only see a small part of the universe. Astronomers call this the “known universe” and it stretches about 14 billion years back through time in one direction, and (we assume) 14 billion years back in another direction.
Ten sextillion stars in the known universe
Astronomers have estimated the number of stars in the Milky Way galaxy as one hundred billion (this is a low estimate by the way). The Milky Way is an average galaxy. Astronomers estimate that there are one hundred billion galaxies in the known universe (another low estimate). The math to figure out the total number of stars in the universe is as simple as the result is mind-boggling!
Counting to one million is not like Counting to one billion
A million is way, way smaller than a billion.
It would take 11 days to count to one million if you counted one number per second without doing anything else. Counting to a billion at the same pace (one per second) would take you 32 years of continuous counting!
Count to 1 million at a rate of 1 per second = 11 days Count to 1 billion = 32 years
– Arithmetic
If you counted all the stars in the Milky Way at the rate of one per second, it would take you about 3200 years to finish counting our one galaxy’s set of stars.
How many stars in my sky now?
Ok. So, let’s get real. Now we know how many stars there may be in the entire known universe, let’s narrow the question.
Here is how we will narrow the question. Let’s create a set of ideal conditions that will guarantee we see as many stars as possible.
This is the set of almost ideal seeing conditions. This set of conditions would guarantee seeing the most number of stars that anyone could ever see with the naked eye:
I am on a tall mountain top with no trees looking up at the perfectly clear and calm sky right now. It is midnight. I can now see approximately half the stars in the sky. These near perfect seeing conditions make it so that I can see stars to magnitude 6 with my 20/20 vision.
Number of stars in the sky I see
According to David Haworth of Stargazing.net there are approximately 7400 magnitude 6 or brighter stars. Remember, we can only see half the sky at any time. So, cutting 7400 in half we get 3700 stars. 3700 stars is the greatest number of stars that any earth-bound human can ever see at any one moment without a telescope or other aides.
Stars in my sky right now
Now we know how many stars you might ever see at once, let’s look at how most people see the sky.
Most people cannot see 3700 stars because of serious light pollution, horizons full of trees and landforms, and atmosphere, lots of watery, moving atmosphere floating above us.
If you are lucky and go camping in a dark sky area you might be able to see about 2000 stars on a good night.
In a typical, light-polluted suburban sky you can see approximately 200-300 stars.
In the middle of a big city the number of stars goes down to about 12 to 20.
12 Stars.
12. That’s not a lot of stars. Maybe take a trip out of the city to see the stars?
Summary
You can see 3700 stars under perfect viewing conditions.
You can see about 2000 under excellent dark skies.
You can see about 300 stars in the suburbs.
You can see 12 stars under bright city lights.
References for how many stars
Stargazing.net – David Haworth compiled data on the number of stars at each magnitude and presented it in a nice table.
Sky and Telescope article – covers skyglow, light measuring technology, light maps, NELM and more. Authoritative.
Space.com article – how astronomers estimate the number of stars in the Milky Way.
National Geographic Kids – Mini article on light pollution with estimates on how many stars are visible from different places.
You can use these 8 ways to find the North Star (Polaris). These are all fun ways to find the North Star. The North Star is special because of its position in the starry sky.
A long exposure photograph showing all of the other northern sky stars circling around the North Star. Image provided by ESO.
8 ways to find the North Star
Look north and guess – you can find the North Star in a relatively dark region of the sky and there are not many other bright stars around it. If you are south of the equator, head north before you try to look for the North Star because you won’t be able to see it until you get the Earth out of the way.
Use the Big Dipper cup stars as pointers. This is the classic way to find the North Star. The two stars of the Big Dipper cup are known as the “pointer stars” and they show you which star is the North Star. The North Star is about 5 lengths of the pointer stars away.
Camera timelapse – ooh! I love timelapse. A great timelapse of the night sky is an unbeatable way to relax. By taking a timelapse of the starry sky you can detect the apparent motion of the stars. If your timelapse covers enough of the sky (with a wide angle view) chances are that you will be able to identify the North Star because it is the star that moves the least.
Phone app – grab a planetarium app like SkySafari. Almost every star app these days has a “Augmented Reality” view that you can use to find Polaris. Just use the AR method of holding the phoone up above your head and searching around or you can type the name of a star into the search box in the app.
Observe the sky, patiently measuring the movement of every star. The one that moves the least is Polaris. This might take a long time because the stars move pretty slowly.
Mark a known spot as your North Star viewing spot. This is easy to do with a product like the Star Spot. You can return to that spot any time of day or night to sight the star – the North Star is always in the same place in the sky.
The North Star is located in between the two easy-to-identify constellations The Big Dipper and Cassiopeia – the Queen.
Memorize its color and the stars around it – this is easier than it sounds! Polaris is a yellow supergiant and has a faint yellow tint. Also, the North Star is located in a region of the Milky Way that has fewer stars so it is surrounded by dark areas of the night sky.
A reader has suggested a 9th way! Create the Summer Diamond. Add a new triangle to the Summer Triangle asterism by using the North Star as a new point. Suggested to me in January 2023 by Peter Birren (Author of the wonderful Objects in the Heavens astronomy book) see below for an illustration. This method is most useful in the summer and early fall months because that is when the Summer Triangle is most visible.
Find the North Star using new asterism – the Summer Diamond. Proposed by Peter Birren.
The Standard way to find Polaris, aka the North Star
Here is the classic way to find the North Star! Use the pointer stars of the Big Dipper. This is a reliable method for finding the North Star that has been taught to generations.
Find the Big Dipper to find the North Star
Look at the two stars in the picture below. One is Dubhe – which is labeled a for alpha, and the other Merak – which is labeled b for beta. These form the outer lip of the Big Dipper’s cup. These two stars can be used to create an imaginary line to “point” at the North Star.
The distance from the pointer stars to the North Star is about 5 times the distance between Dubhe and Merak.
The North Star is shown in this image as a red dot labeled “Polaris.”
Use the two pointer stars of the Big Dipper to find the North Star (Polaris). Picture credit user Bonĉ source Wikipedia
These instructions work for the 80% of people who live in the northern hemisphere – anywhere north of the equator. For the 20% of people who live in the southern hemisphere the North Star is not visible because it is blocked by the Earth. As you move south toward the equator (and eventually move past the equator), the North Star gradually sinks lower in the sky until it stays completely below the northern horizon.
A Merry-Go-Round is a good model of daily Earth rotation.
The Earth is like a merry-go-round showing us seasonal constellations
That iconic childhood ride. Round and round each day we go, round and round each year we go, where we stop nobody knows! When we look out from the edge of the ride we can see the space beyond. Sometimes the Sun occupies that space, and sometimes that space is the night sky filled with stars.Click here to continue reading…
Your hands and arms help you see the orbits of Mercury and Venus and the shape of solar system
Question: If you could see the orbit of Venus would it fill the whole sky?
The answer might surprise you!
You can use your hands and arms to see the size of the orbits of the solar system’s inner planets: Mercury and Venus.
Imagine (as pictured below) if the orbit of Mercury were visible as a red oval and the orbit of Venus were visible in green.
Two hand spans show the orbit of Mercury, elbows show the orbit of Venus.
Physical Astronomy – see Mercury and Venus orbits
Caution! Do not look directly at the Sun without proper solar safety glasses on.
Turn toward the Sun, hold your arms out straight, hands up in the air with fingers spread wide and thumbs touching. Your pinky fingers now span the width of the orbit of Mercury and your elbows span the width of the orbit of Venus.
Both of the entire orbits of Mercury and Venus orbits would be visible in the sky all at once – if they could be made visible during the day.
