Kurzgesagt – In a Nutshell
Sources – The Night Sky Poster
The Night Sky Poster – Sources
Data & Code
The "Night Sky Poster" is a data-based visualization of all stars and celestial objects that humans can see at night from Earth with the naked eye, provided the sky is clear and free of light pollution. Since we are working with large amounts of data, it is quite impossible to create this poster completely by hand, so we decided to use a code-based design approach for the Night Sky Poster.
The code we used is a modified version of The Western Constellations project by Eleanor Lutz, released under the GPL 3.0 license. If you want to read more about the process, the code, and the creator's thoughts behind the project, take a look at the original repository.
We have adjusted the code in a few places to highlight certain features or sort the data differently. Some parts of the code, such as the position of the planets, are experimental - but the map can also be implemented without them. The code and its output are just the foundation on which the rest of the design is based. The illustrations, script, and typography were created outside of the programming environment. In the end, everything was brought together in Adobe Illustrator to create the final The Night Sky Poster.
We share our code in this GitHub repository under the same GPL 3.0 license. You can also use and change this code to create your own map of the night sky:
https://github.com/kurzgesagt-inanutshell/The-Night-Sky-Poster
STARS
We have grouped visible stars by apparent magnitude. The scale starts with the star Vega, which gives us magnitude 0.0. Each -1 magnitude is 2.512 times brighter, with negative numbers being brightest.
-2 to 0: The brightest stars:
0 to 2: Highly visible stars.
2 to 4: Less visible stars.
4 to 6.5: The dimmest stars.
The Magnitude Scale, ANTF, retrieved 2021
“With the recalibration of Hipparchus' original values the bright star Vega is now defined to have an apparent magnitude of 0.0”
“If a star of magnitude 1 is 2.512 × brighter than a star of magnitude 2 and 100 × brighter than a sixth magnitude star how much brighter is it than a star of magnitude 3? You need to be careful here. It is not simply 2 × 2.512 different. You need to remember that a difference of one magnitude equals 5√100 = 2.512. A difference of 2 magnitudes therefore = 2.5122 = 6.31 × difference in brightness.”
https://www.atnf.csiro.au/outreach/education/senior/astrophysics/photometry_magnitude.html
VARIABLE STARS
The brightness of these stars changes over time. We’re showing them at their brightest.
We show variable stars at their brightest point because in most cases, variable stars are not visible at their average brightness.
Pulsating Variable Stars, ANTF, retrieved 2021
“Pulsating variable stars are intrinsic variables as their variation in brightness is due to a physical change within the star. In the case of pulsating variables this is due to the periodic expansion and contraction of the surface layers of the stars.”
https://www.atnf.csiro.au/outreach/education/senior/astrophysics/variable_pulsating.html
MESSIER OBJECTS
Messier objects are star clusters, galaxies, nebulas and more. We show the ten brightest on this map, namely the following:
-M45, -M24, -M7, -M31, -M44, -M42, -M6, -M47, -M41, -M25.
We depict the Messier objects on the map using icons based on NASA imagery.
Hubble’s Messier Catalog, NASA, 2021
https://www.nasa.gov/content/goddard/hubble-s-messier-catalog#grid
Messier Object Data, sorted by Apparent Visual Magnitude, 2013
https://www.messier.seds.org/dataMag.html
ZODIAC CONSTELLATIONS
These are the 12 historically significant constellations that the Sun crosses as it travels across the sky.
Zodiac Constellations, Constellation Guide, 2021
https://www.constellation-guide.com/constellation-map/zodiac-constellations/
OFFICIAL CONSTELLATIONS
The International Astronomical Union has officially recognized 88 constellations, with the modern versions based on contributions of astronomer Eugène Delporte.
The Constellations, IAU, retrieved 2021
https://www.iau.org/public/themes/constellations/
88 Officially Recognized Constellations, NASA, retrieved 2021
https://starchild.gsfc.nasa.gov/docs/StarChild/questions/88constellations.html
There are official depictions of the constellations as defined by the IAU, as well as many other ways to draw lines between the stars. These alternate depictions are equally valid but sometimes more visually striking.
We have chosen to use alternate depictions for the following constellations in coordination with our consulting expert Prof. Matthew Caplan
The Official link points to the depiction by the IAU. The Alternative link is a design we found to be more visually impressive or evocative of the legends and stories behind the constellation.
Virgo
Official: https://www.iau.org/static/public/constellations/gif/VIR.gif
Alternate: http://www.seasky.org/constellations/constellation-virgo.html (Sea and sky version)
Libra
Official: https://www.iau.org/static/public/constellations/gif/LIB.gif
Alternate: https://www.dkfindout.com/uk/space/constellations/libra/
Hercules
Official: https://www.iau.org/static/public/constellations/gif/HER.gif
Alternate: https://en.wikipedia.org/wiki/Hercules_(constellation)#/media/File:Hercules_constellation_map_visualization.PNG
Leo
Official: https://www.iau.org/static/public/constellations/gif/LEO.gif
Alternate: https://en.wikipedia.org/wiki/File:Leo_constellation_map_visualization.PNG
Scorpio
Official: https://www.iau.org/static/public/constellations/gif/SCO.gif
Alternate: https://bloximages.chicago2.vip.townnews.com/azdailysun.com/content/tncms/assets/v3/editorial/f/e2/fe23882a-e0ff-5a81-a59f-ef4cf56f6307/5764aa73f0ddd.image.gif
PLANETS
Planets can easily be confused with stars due to their brightness, but they are wandering through the sky. We show the positions of Mercury, Venus, Mars, Jupiter, Uranus and Saturn on 9th of July 2013. Neptune is not included because it is too faint.
We use magnitude 6.5 as the threshold for what the human eye can see. Uranus at magnitude 6 is barely visible, but Neptune at magnitude 8 is never visible.
How bright are the planets?, Sky & Telescope, 2020
https://skyandtelescope.org/observing/measuring-planet-magnitudes/
We chose to depict the positions of the visible planets according to where they were on the night of Tuesday 9th of July, 2013. That is the date of Kurzgesagt’s founding!
You can check their positions at other dates and times using this sky map:
https://in-the-sky.org/skymap.php
This Map in Detail:
Night Vision
We depict the nearly 9000 objects with an apparent magnitude of 6.5 or brighter. Even in perfect conditions the human eye cannot see anything dimmer so what remains is the ‘visible’ part of the night sky. The 10 brightest stars are: Sirius, Canopus, Arcturus, Alpha Centauri, Vega, Capella, Rigel, Procyon, Achernar and Betelgeuse. Try to find these cosmic highlights on the map!
There are many millions of objects in the sky, but only a fraction of them are visible to the human eye. This is due to the limiting magnitude of 6.5
Limiting Magnitude, Swinburne University of Technology, retrieved 2021
“After dark adaptation and under the very best observing conditions, the limiting magnitude of the human eye is about magnitude 6.5. However, this is an average, and some people have reported seeing objects fainter than this. At night, from a busy city with lots of light pollution, the limiting magnitude may drop to magnitude 1 or 2, meaning that only the brightest stars are visible.”
https://astronomy.swin.edu.au/cosmos/L/Limiting+Magnitude
Here is a list of the 100 brightest stars in the sky:
Brightest Stars, Abrams Planetarium, retrieved 2021
https://web.pa.msu.edu/people/horvatin/Astronomy_Facts/brightest_stars.html
Stars and Constellations
These are the lines we have drawn between groupings of stars in certain patches. There are 88 official constellations according to the International Astronomical Union, as established in 1928. They are defined by boundaries based on sky coordinates and each one may contain stars that are very far apart from each other, but appear close to us. The most recognizable are the 12 zodiac constellations. These cover the band of the sky that the Sun and Moon traverse.
The history of constellations spans thousands of years, with the modern 88 constellations accepted by the IAU in 1928 only being the most recent event. They are actually specific boundaries that cover the entire sky like patchwork. How the lines connect the stars within those boundaries is less important and open to interpretation.
What is a constellation?, Constellation Guide, 2021
“While modern constellations are defined as areas of the sky and not star patterns, historically the term constellation was commonly used for asterisms formed by the constellations’ brightest stars. These asterisms are often the most conspicuous parts of constellations, which is why the term constellation is still colloquially (and incorrectly) used synonymously with asterism.”
https://www.constellation-guide.com/what-is-a-constellation/
A Spherical Sky
The map of the night sky is a globe unrolled onto a flat surface. It can be divided using the same latitudes and longitudes as we do down on our own spherical Earth. That means you can see more of the top or bottom half of this map depending on how far North or South you are on the planet.
Our map is supposed to be a projection of the night sky placed on a table or wall and read while looking down at it. It might seem reversed left-to-right compared to maps which are supposed to be held above your head and read from below.
The ‘latitude’ and ‘longitude’ divisions are similar to those used on a map of the Earth, but their correct names are Declination (in degrees) and Right Ascension (in hours/minutes).
How to read a star chart?, Optical Mechanics, retrieved 2021
https://www.opticalmechanics.com/how-to-read-a-star-chart/
Our Connection to the Past:
Signs in the Sky
Divine interpretation
The sky has been granted divine significance in many cultures throughout history. It was believed that the future could be predicted and the will of the gods revealed by interpreting cosmic events. Comets and eclipses were believed to have the greatest significance – from the assassination of Caesar to the birth of Christ. The tradition continues today in the form of astrology.
Astral Divination in the Context of Mesopotamian Divination, Medicine, Religion, Magic,
Society, and Scholarship, David Brown, 2006
“The fundamental premise lying behind celestial and other forms of divination in
Mesopotamia was that the gods would, on occasions, impart information to humans through signs, that could bode both well and ill, providing a positive or
negative answer to a query, or more specific (unfalsifiable) information on what
will happen in the future.”
https://core.ac.uk/download/pdf/228878114.pdf
R.6068, British Museum, retrieved 2021
“In 44 BC, following the death of Julius Caesar, a comet appeared in the heavens over Rome and was accepted to be a manifestation of the divine soul of Julius Caesar. It was thought to herald a new age of peace and prosperity”
https://www.britishmuseum.org/collection/object/C_R-6068
The Star of Bethlehem, a comet in 5 BC and the date of Christ’s birth, Colin J. Humphreys, 1992
“The Star of Bethlehem was a Comet?
[...] In particular it is suggested that the Magi originally saw the comet in the east in the
morning sky (see later). They travelled to Jerusalem, a journey time of 1–2 months (see later), and in this time the comet had moved through about 90_, from the east to the south, which is consistent with the 1 or 2 degrees per day typical motion of a comet.”
https://legacy.tyndalehouse.com/tynbul/Library/TynBull_1992_43_1_02_Humphreys_StarBethlehem.pdf
Our illustration is inspired by Themis, the oracle of Delphi, a mythological figure who presided over ancient oracles at a time when Ancient Greeks gave special significance to the ‘kometes’ that appeared in the sky.
Themis, Theoi, retrieved 2021
“She was also a prophetic goddess who presided over the most ancient oracles, including Delphoi (Delphi). In this role, she was the divine voice (themistes) who first instructed mankind in the primal laws of justice and morality, such as the precepts of piety, the rules of hospitality, good governance, conduct of assembly, and pious offerings to the gods.”
https://www.theoi.com/Titan/TitanisThemis.html
Comet, Oxford reference, 2021
“The name derives from the Greek kometes, meaning ‘long-haired’”
https://www.oxfordreference.com/view/10.1093/oi/authority.20110803095626574
Pleiades
Humanity’s Oldest Tale
Some of humanity’s oldest tales speak of seven sisters in the sky: the Pleiades. Six of the stars in the constellation are easily visible, but spotting the seventh star may have been used as a visual acuity test throughout history. Actually the Pleiades cluster is much larger though: through telescopes we can see that it contains over a thousand stars.
Nature’s sight test in the night sky, Optician, 2021
“For those wishing to test their eyesight further, or who are located in the southern hemisphere, there is another test available at the Pleiades star cluster. Known as the Seven Sisters and located in the constellation of Taurus, it actually consists of more than seven stars. To see all seven main stars, it is said, would mark one out as a warrior suitable for battle; to be able to see five is considered good.”
https://www.opticianonline.net/features/natures-sight-test-in-the-night-sky
Wandering Stars
Planets in Disguise
Ancient peoples noticed that five lights in the night moved distinctly from the rest. These moving lights were first called `wandering stars`. Sumerian astronomers from over 4000 years ago then named them Enki, Innana, Gugulanna, Enlil and Ninurta. Today we know them as Mercury, Venus, Mars, Jupiter, and Saturn.
Names of the Planets, Robert Little, 2008
http://www.weasner.com/etx/fun/2008/little/Names_of_the_Planets.htm
Our illustration is inspired by the Sumerian astronomers who first tracked and gave written names to the planets. Their tablets were copied by the Ancient Babylonians, and it is the latter that survived to this day.
Understanding planets in Ancient Mesopotamia, Enn Kasak and Raul Veede, 2001
“Writing was invented by Sumerians ca 3200 BC. Cuneiform tablets of Sumerian period give us very interesting material but unfortunately no astronomical or astrological texts. Though some texts have been thought to originate from former periods, they have been only found in later copies, making dating extremely difficult. The oldest existing texts about stars, one astrological and one astronomical, both come from the Old Babylonian period.”
https://www.folklore.ee/folklore/vol16/planets.pdf
Ancient Records
Sky Clocks
Humanity discovered the practical uses of watching the night sky long ago. Record keeping and many tools were developed to assist this. These include the Egyptian Nabta Playa stone circle from 7000 years ago, the famous 5000 year old Stonehenge in England, tablets with constellation names from 4000 years ago, and amazing devices such as the 2000 year old Antikythera mechanism.
Nabta Playa: The world's first astronomical site was built in Africa and is older than Stonehenge, Astronomy, 2020
“Located in Africa, Nabta Playa stands some 700 miles south of the Great Pyramid of Giza in Egypt. It was built more than 7,000 years ago, making Nabta Playa the oldest stone circle in the world — and possibly Earth’s oldest astronomical observatory.”
Astronomy at Nabta Playa, J. McKim Malville, 2014
“In the Late and Terminal Neolithic (7,500–5,400 BP), nomadic pastoralists built a ceremonial center on the western shore of Nabta Playa, consisting of some 30 complex megalithic structures, stone circles, and lines of megaliths crossing the playa.”
https://link.springer.com/referenceworkentry/10.1007%2F978-1-4614-6141-8_101
Stonehenge, Encyclopædia Britannica, retrieved 2021
“Stonehenge was built in six stages between 3000 and 1520 BCE, during the transition from the Neolithic Period (New Stone Age) to the Bronze Age.”
https://www.britannica.com/topic/Stonehenge
Morphometric findings on the Nebra Sky Disc, Henning Dathe and Harald Krüger, 2018
“Being dated to the end of the Early Bronze Age around 1600 bc, the Sky Disc is considered the earliest known transportable astronomical representation of the night sky.”
https://www.tandfonline.com/doi/full/10.1080/1751696X.2018.1433358
Omens in the Stars: A Brief History of Babylonian Astrology, Kepler College, retrieved 2021
“Some of the oldest recorded astrological tablets date back to Babylonian civilization from 2400 BCE. Records show this region settled as early as 4000 BCE and growing into the cultural region known as Babylonia—is what is presently known as Iraq.”
Mysterious Antikythera Mechanism Is Even Older Than We Thought, Smithsonian magazine, 2014
“The 82 discolored, corroded bronze fragments of the Antikythera Mechanism may not look like much on their own. But assembled they reveal a complex mechanism, with 37 gears that track the sun and moon and predict eclipses. This astronomical calendar or calculator was discovered in a shipwreck off the coast of Crete in 1901 and is more than 2,000 years old.”
Our illustration is a depiction of the Nabta Playa stone circle as best illustrated here:
Some notes on the Canaries and the Sahara, Mark Milburn, 2003
https://mdc.ulpgc.es/utils/getfile/collection/almog/id/464/filename/451.pdf
13 Months
Ancient Babylon Until Today
The 12 constellations were decided upon by the ancient Babylonians at around 500 BC, and they corresponded to the 12 months we still use today. The Chinese had an even more ancient constellation-calendar since 3000 BC, with a 13th month added around every three years as a leap month.
Origins of the ancient constellations: II. The Mediterranean traditions, Rogers, J. H., 1998
“The classical map of the sky, with the 48 Greek constellations, was derived from at least two different pre-Greek traditions. One tradition comprised the 12 signs of the zodiac, with several associated animal constellations, all of which developed over ~3200-500 BC in Mesopotamia in a religious or ritual tradition. These were taken over by the Greeks around 500 BC.”
https://ui.adsabs.harvard.edu/abs/1998JBAA..108...79R/abstract
Our illustration is inspired by the ancient Babylonian priest-astronomers called the Chaldeans who created clay tablets such as the Enuma Anu Enlil to record centuries of observations and how to interpret them as omens for their king.
Mesopotamian Astronomy, Explorable, 2010
“From 1800 BC, they meticulously plotted the movement of the sun and the moon, using them to track the procession of the seasons. The societal class responsible for this were the Chaldeans, priest-astronomers who began to look to the skies for the prediction of events, astrologers as much as astronomers.”
https://explorable.com/mesopotamian-astronomy
Library of Ashurbanipal, British Museum, retrieved 2021
“Tablet 50 seems to have contained omens concerning the appearance of various stars or constellations and their relation to events on earth.”
https://www.britishmuseum.org/collection/object/W_K-4292
Shifting Constellations
Stories of Past Nights
Since stars move in their orbits around the galaxy, we are not looking at exactly the same night sky as previous generations. Only the stories we’ve invented about them have persisted, and they form a cultural connection as we pass them forward. Even today we give special significance to the stars, as we discover more about them than ever before.
The constellations change as the Earth wobbles around its axis of rotation, and as it orbits the Milky way along with our Sun.
The future of the Orion constellation, ESA, 2017
“Stars are not motionless in the sky: their positions change continuously as they move through our Galaxy, the Milky Way. These motions, too slow to be appreciated with the naked eye over a human lifetime, can be captured by high-precision observations like those performed by ESA’s billion-star surveyor, Gaia.
By measuring their current movements, we can reconstruct the past trajectories of stars through the Milky Way to study the origins of our Galaxy, and even estimate stellar paths millions of years into the future.”
https://www.esa.int/Science_Exploration/Space_Science/Gaia/The_future_of_the_Orion_constellation
Our illustration faces a modern person with a hunter-gatherer from an era long before writing existed. Some cave paintings from over 40,000 years ago are thought to show constellations in the sky, so star-gazing might be an activity that we share with our earliest ancestors.
Cave paintings reveal ancient Europeans’ knowledge of the stars, Science Focus, 2019
“Some of the world’s oldest cave paintings are now thought to depict not wild animals as was previously thought, but constellations in the night sky. This suggests that in these artworks, people were using the positions of constellations to represent dates, and mark events such as comets hitting Earth.[...]
Some of the art in question dates back as far as 40,000 years ago, around the time Neanderthals became extinct.”
Light Pollution
Losing Our Oldest Heritage
Light pollution from artificial lighting has obscured the night sky in cities and created a glow that extends far beyond. It affects 99% of the human population and the majority of us have a reduced view of what lies above us. 60% of Europeans and almost 80% of North Americans cannot see objects dimmer than an apparent magnitude of 5. Astronomers are the worst affected.
The new world atlas of artificial night sky brightness, Fabio Falchi et al., 2016
“This atlas shows that more than 80% of the world and more than 99% of the U.S. and European populations live under light-polluted skies. The Milky Way is hidden from more than one-third of humanity, including 60% of Europeans and nearly 80% of North Americans. Moreover, 23% of the world’s land surfaces between 75°N and 60°S, 88% of Europe, and almost half of the United States experience light-polluted nights.”
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4928945/
Interstellar Travel
Reaching for the Stars
The stars have always been something we observe from a distance, and they seem further away than ever after we discovered the light-years that separate us from them. However, should we start considering stars as places we could reach? Interstellar probes are on the drawing boards and soon we will have the technology to physically visit these lights in the sky.
Various plans are in motion to develop an interstellar probe in the next few decades. A human trip to the stars is further off.
Starshot, Breakthrough Initiatives, retrieved 2021
“In the last decade and a half, rapid technological advances have opened up the possibility of light-powered space travel at a significant fraction of light speed. This involves a ground-based light beamer pushing ultra-light nanocrafts – miniature space probes attached to lightsails – to speeds of up to 100 million miles an hour. Such a system would allow a flyby mission to reach Alpha Centauri in just over 20 years from launch, beaming home images of its recently-discovered planet Proxima b, and any other planets that may lie in the system, as well as collecting other scientific data such as analysis of magnetic fields.”
https://breakthroughinitiatives.org/initiative/3
Our illustration depicts an astronaut approaching the Alpha Centauri system. It is composed of two stars; Alpha Centauri A and the smaller Alpha Centauri B, orbiting each other closely. A third star, the dim and far away Proxima Centauri, would not be seen in the same view.
Alpha Centauri: A Triple Star System about 4 Light Years from Earth, NASA, 2018
“The stars in the Alpha Centauri system include a pair called “A” and “B,” (AB for short) which orbit relatively close to each other. Alpha Cen A is a near twin of our Sun in almost every way, including age, while Alpha Cen B is somewhat smaller and dimmer but still quite similar to the Sun. The third member, Alpha Cen C (also known as Proxima), is a much smaller red dwarf star that travels around the AB pair in a much larger orbit that takes it more than 10 thousand times farther from the AB pair than the Earth-Sun distance. Proxima currently holds the title of the nearest star to Earth, although AB is a very close second.”
