First of all, what is a constellation?
Before we dive into the Pyxis Constellation, let’s first take a look at what exactly a constellation is.
A constellation is an area on the celestial sphere (an imaginary sphere) where a group of visible stars are located.
These stars typically form a pattern or outline, which we perceive to represent an inanimate object, (like the mariner’s compass, or Argo Navis the ship, an animal (like the fox, a mythical person (like Jason and the Argonauts, or even a type of creature (like Pegasus, the winged-horse, or Medusa),from Greek mythology.
It is also an astronomy term used to describe a variety of groups of stars that have been given a specific name such as –
Constellations are constantly moving and move in the direction from East to West.
The Constellation Pyxis – Facts in brief:
What is it? –
Pyxis, the Compass Constellation, is regarded as a fairly small and faint constellation in the southern sky. It is listed as the 65th largest Constellation overall filling around 0.5% of the night sky.
The name ‘Pyxis’ is Latin for the ‘mariner’s compass’, or the ‘magnetic compass’.
It is a diminutive of the words ‘Pyxis Nautica’, or ‘Pixis Nautica’ meaning a nautical compass.
Pyxis, abbreviated to ‘Pyx’, or ‘Pyxis Nautica, Pixis Nautica’ (its Latin name) is quite easy to recognize, as it resembles the outline of the compass.
How was it formed, found and named?
The Constellation of Pyxis is not one of the original 48 Constellations that were devised and later catalogued by Ptolemy.
It was in fact many years later that the French astronomer Nicolas Louis de Lacaille introduced this constellation to the world as part of his studies of the Constellations. This was from a location on Earth known as the Cape of Good Hope, in modern day South Africa.
Pyxis is one of the 14 constellations named by Nicolas Louis de Lacaille in the 18th Century. He originally called it ‘La Boussole’, (the box). It later adopted the Latin name of Pixis Nautica, which was eventually shortened to Pyxis.
Pyxis fills an area of 221 square degrees.
- Initially, the shapes of their star patterns informally categorized the Constellations in the sky.
- Eventually, the International Astronomical Union published the official listing of constellation boundaries, mapping the constellations by their sky coordinates not by their line patterns and shapes.
Pyxis is one of the 88 Constellations listed in the official IAU chart published by the International Astronomical Union (IAU).
The Constellation of Pyxis is located in the path of the Milky Way.
The 3 main bright Stars in Pyxis are positioned in a row, they are:
- Alpha Pyxidis, Beta Pyxidis and Gamma Pyxidis
Where is it located? –
The Pyxis Constellation is positioned in the second quadrant of the Southern Hemisphere, south of the celestial equator (which is different from the ecliptic). Being located south of the celestial equator makes it more visible from the Southern Hemisphere.
It is sometimes referred to as being located in the SQ2 Quadrant.
FACT: The ecliptic is the imaginary line tracing the route that The Sun, the Moon, and the Planets take across the sky, over the year.
The plane of the Milky Way passes through the Constellation of Pyxis close to the Stars that previously formed the now renamed Constellation Argo Navis (this Constellation was imagined as the ship from the Greek myth of Jason and the Argonauts)
The Constellation of Pyxis is not considered to be a circumpolar constellation as it is not visible throughout the year in Southern latitudes.
It is best seen early in the year between the months of January and March
The Circumpolar Constellations
There are 5 Constellations that are visible throughout the year, from most locations located north of the celestial equator, making them Circumpolar, they are:
- Cassiopeia Constellation
- Cepheus Constellation
- Draco Constellation
- Ursa Major Constellation
- Ursa Minor Constellation
FACT: A constellation that is visible all year round is known as a Circumpolar Constellation.
There are 3 Southern Constellations that are also circumpolar –
Where can it be seen?
Co-ordinates of a right ascension, or left ascension and their declination are used to locate all of the Constellations, like Pyxis.
Pyxis is most prominent in the Southern Hemisphere.
The Constellation of Pyxis lies at a 9 hours right ascension, and a declination of -30 degrees South.
It’s more easily visible from the Southern Hemisphere at latitudes between +50 degrees and -90 degrees and covers an area of 221 square degrees in the Southern sky.
Meet The Neighbors
The Pyxis Constellation is bordered by several other Constellations:
It is most visible in the Southern Hemisphere in the evening around 21.00 hours, during the month of January.
The Heavenly Waters Family of Constellations
Pyxis is a member of the ‘Heavenly Waters Family of Constellations’. This group of Constellations includes:
How can you identify The Constellation of Pyxis?
The simplest method for spotting any particular Constellation from Earth is to first of all locate the brightest star in that Constellation, and then look at the neighboring illuminations, or other neighboring well-known Constellations, to see if you can identify a recognizable pattern.
There are few bright stars located within the faint Constellation of Pyxis.
There are only 10 main Stars that make up the main Pyxis Constellation.
The bright Stars in any Constellation are listed and named in order of luminosity, using the Bayer designation system, from the brightest Star to the faintest Star.
A Bayer designation for a Star is where the ‘Alpha’ letter is normally allocated to the brightest star in front of its Latin genitive name (Pyxidis), then ‘Beta’ and so on in decreasing order through the letters of the Greek alphabet (although not all the Greek letters are used in every constellation).
- The brightest Star is Alpha Pyxidis), and has an apparent visual magnitude of 3.68
- The second brightest Star in Pyxis is called ‘Beta Pyxidis’
- The 3 main Stars are positioned in a straight line
- The closest main Star is located around 207 light years and the furthest is around 879 light years away.
- The closest Star with an exoplanet is HD 73256 located around 123 light years from Earth
- The dimmest Star that can be seen by the naked eye is HD 73072 with an apparent magnitude of around 5.95
- The farthest Star is HIP 43041, and it’s located around 81541 light years from the Sun
- There are 18 Stars in Pyxis that are visible by the naked eye in a clear dark night sky.
- A total of 629 Stars have been identified and scanned by the Hipparcos satellite but not all are visible by the naked eye.
The Pyxis Constellation can be identified in the night sky as the compass, such as a magnetic compass or the mariner’s compass that would have been used as a navigation tool back in the 18th Century and 19th Century.
The brightest stars of Pyxis can be viewed from Earth, from a Southern location in the evening, by the naked eye.
The Star System within Pyxis
There are no named Stars within Constellation Pyxis.
The Constellation of Pyxis has 10 main Stars making up the imaginary outline of the compass positioned on the sail of Jason’s Argo Navis ship.
The stars that form the overall shape of Pyxis, listed from brightest Star to fainter stars are still faint in comparison to many other constellations. They are:
- Alpha Pyxidis (a Pyx) – the brightest in Pyxis
- Beta Pyxidis (b Pyx) – the second brightest in Pyxis
- Gamma Pyxidis (y Pyx) – a singular orange Giant hued Star, a red clump Star
- Kappa Pyxidis (k Pyx) – a Giant Star
- Theta Pyxidis (ΘPyx) – a Red Giant Star
- Lambada Pyxidis (λ Pyx) – a yellow hued Star that’s part of a Binary System
- Zeta Pyxidis (ζ Pyx) – a Binary Star
- Delta Pyxidis (δ Pyx) – a Star
FACT: Hipparcos created the apparent magnitude system to rank the brightness of Stars (for example he decided that that the grade of a first magnitude star should be twice as bright as a second magnitude Star, and so on.
The Location of Pyxis
This Constellation can be spotted in the Southern Hemisphere, also referred to as the Southern celestial sky.
The Constellation Pyxis is surrounded by various recognizable Constellations namely Antila, Hydra (the largest Constellation in the night sky), Puppis and Vela.
The identifiable outlines of these Constellations are used as a guide-point in the sky used by astronomers and amateur stargazers to identify certain Deep Sky Objects of interest.
The naming of Pyxis
This constellation was originally known as Pyxis Nautica, represented as a type of marine compass. The image of Pyxis should not be confused with the Constellation of Circinus, which is represented as a draftsman’s compass.
The Constellation of Pyxis is located close to the old Constellation of Argo Navis (now defunct) associated with the myth of Jason and the Argonauts.
Originally the main Star asterism in Argo Navis were imagined as parts of the whole ship image:
- Carina represented – the keel or hull of the ship
- Vela represented – the sail of the ship
- Puppis represented – the stern or the poop deck of the ship
Eventually these three parts of Argo Navis became known as independent Constellations.
Changing the name of the constellation
The Latin name for the mast of a ship is ‘Malus’.
In the 19th Century, British astronomer John Hershel suggested that an area within the Constellation Argo Navis was represented by the image of a mast should be renamed Malus instead of Pyxis.
This idea wasn’t popular and now Malus is not recognized.
What’s within the Pyxis Constellation?
The different components housed by Constellations are mainly Stars, Deep Sky Objects and Messier objects (galaxies).
The Constellation Pyxis is formed by of a number of different components:
- 5 main Stars
- 4 stars that host an exoplanet
- 0 named Stars
- No associated meteor showers
- 0 Messier Objects
What is a Bright Star?
The sky is home to various bright stars.
The brightness of a star is measured by a value called its magnitude (apparent magnitude) and they come in different sizes, composition, mass and color.
Their vast distance away from us is measured in light years from the Earth, the Sun or even the Milky Way.
The lower the magnitude value the brighter the star appears in the night sky when viewed from Earth.
FACT: The Sun is considered to be the brightest star in the sky.
Pyxis Constellation can be identified by locating the brightest Star alpha Pyxidis, in a straight line with the beta Pyxidis and Gamma Pyxidis stars in the center of this small constellation.
As well as Stars and Star Clusters, thePyxis Constellation also has deep sky objects and galaxies (or even globular clusters or open clusters).
Deep Sky Objects
The Constellation of Pyxis contains deep sky objects, including objects from the Henry Draper Catalogue of Stars (abbreviated to HD and a designated number as an identifier)
There are no Messier objects, but there are Messier NGC catalogued objects present in Pyxis.
FACT: A Deep Sky Object is an astronomical object, that is not a solar system object like the Sun, Moon, Comet or a Planet. An individual Star is not considered to be a Deep Sky Object.
Deep Sky Objects are faint objects that can still be observed by the naked eye in the night sky from Earth.
Deep Sky Objects include Galaxies, Star Clusters and Nebulae.
- Star clusters – such as Globular Clusters of Stars or Open Clusters of Stars
- Dark Nebula, Planetary Nebula, Diffuse Nebula, and Supernova remnants
- Galaxy Groups, Galaxies, Gravitational Lenses and Quasars.
What is a Nebula?
A Nebula is a massive cloud of gas and dust in Space.
Some Nebulae are formed when a star explodes and then dies, as is the case with a Supernova. Sometimes they can act as Star nurseries and are the areas where new Stars are forming.
The Nebulae are the spaces in between the stars referred to as interstellar space.
There are several types of Nebulae:
- Bright Nebulae,
- Emission Nebulae,
- Reflection Nebulae,
- Dark Nebulae
- Planetary Nebulae
There are Planetary nebula within Pyxis designated under the Charles Messier classification and listed in his New General Catalogue (usually abbreviated to NGC):
- NGC 2818 is a Planetary Nebula in Pyxis, with an apparent magnitude of 11.6 and not visible by the naked eye
FACT: a ‘reflection nebula’ is an interstellar cloud that should be a dark nebula (a molecular cloud) however its dust reflects light from a nearby bright star and it reflects the light, hence the name.
Images of the Nebulae have been captured using professional Space telescopes, such as the NASA Spitzer Space Telescope, operated by NASA, and the famous Hubble Space Telescope.
Pyxis is often abbreviated to ‘Pyxi’ from a naming convention used by NASA.
What is a Messier?
A Messier is a cluster of Stars
Charles Messier, a French astronomer, is credited with cataloging each of the Messier Star clusters, around 1764.
He is famous for publishing an astronomical catalogue that lists 110 nebulae and star clusters, known as the New General Catalogue (used in its abbreviated form NGC and numbered).
There are no Messier object star clusters within Constellation Pyxis, but there are some NGC listed objects
FACT: A star cluster is a large group of Stars that can be Globular Clusters or Open Clusters:
- Globular Clusters:
A global cluster is a spherical collection of ‘Old Stars,’ numbering hundreds to millions, that are tightly bound by gravity and orbits a galactic core.
- Open Clusters:
An open cluster is a looser formation of ‘Young Stars’ that generally has less than a few hundred Stars.
NGC 2627 is an open cluster. It is located south of the celestial equator. It has a visual magnitude of 8.4, meaning it is not visible by the naked eye but it is visible using binoculars.
NGC 2658 is another open cluster. It is also located south of the celestial equator. It has a visual magnitude of 9.2, meaning it is not visible by the naked eye but it is visible using binoculars
NGC 2635 is another open cluster. It has a visual magnitude of 11.2, meaning it is not visible by the naked eye but it is visible with the help of binoculars
A supernova remnant is the structure that’s left after a star explodes in a supernova.
There are 3 types of supernova remnants: shell-like, composite and mixed-morphology (or thermal composite).
NGC 2613 is a Spiral Galaxy in Pyxis. It is located close to the celestial equator and that means it is partly visible from both the Northern Hemisphere and the Southern Hemisphere at certain times of the year.
It has a visual magnitude of 10.42. As a minimum visual magnitude of +6.0 is required for any sky object to be seen by the naked eye, NGC 2613 is only visible with the help of binoculars.
What is the Milky Way?
The Milky Way is a Spiral Galaxy, containing over 200 billion Stars, and actually forms part of the Constellation of Sagittarius.
The Milky Way itself is not a Constellation of Stars. It is the Galaxy that contains our solar system and it gets its name from the fact that it looks like a hazy swirl or river of milk across the sky, when viewed from earth. It is made up of gas, dust and stars, with spiral arms wrapped around it, and a massive black hole in the center of the Galaxy.
Not all of the Stars in the Universe are contained within the Milky Way. It is at its brightest if looking towards the galactic center in the direction of Sagittarius.
The Stars that make up the Milky Way are many light years away and cannot be individually identified by the naked eye.
Background & Facts:
The Greeks were the first ancient culture to name the modern Constellations in the sky.
However, in the case of the Constellation of Pyxis there were no associated Greek myths, nor did they know about the magnetic compass.
It was the well-known Greek Astronomer – Ptolemy, who first cataloged the 48 early constellations, in the 2nd Century (2 AD.), but he did not catalogue the Constellation of Pyxis.
Nicolas Louis de Lacaille
It was the French astronomer Nicolas Louis de Lacaille who first recorded the Constellation of Pyxis as he surveyed the Southern skies. and originally depicted it as ‘La boussole’, a magnetic compass used by seamen.
In the second edition of his sky charts he used the Latin name ‘Pixis Nautica, which he later shortened to ‘Pyxis’.
Pyxis still remains as one of the 88 modern Constellations defined by the IAU.
In 1603, The German Astronomer – Johann Bayer, systematically assigned names to the brightest stars in each constellation and cataloged them in his Star atlas – ‘Uranometria Omnium Asterismorum’.
The Bayer designations are stellar designations where the stars within Constellations are initially identifiedby a name or a letter from the Greek Alphabet from Alpha through Omega (in order of brightness).
1. The names of the Stars begin with a letter of the Greek alphabet starting with– Alpha, then beta, gamma, etc.
2. Followed by the genitive form of their parent constellation’s Latin name – ‘Pyxidis’
3. Giving the first Star name Alpha Pyxidis
The main stars of Pyxis are named by their apparent magnitude (luminosity) from brightest to faintest star in decreasing order, Stars with an apparent magnitude of less than +5.00 include:
1. Alpha Pyxidis – an apparent visual magnitude of 3.68
2. Beta Pyxidis – a variable visual magnitude of 3.97
3. Gamma Pyxidis – an apparent visual magnitude of 4.02
4. Kappa Pyxidis – an apparent visual magnitude of 4.62
5. Theta Pyxidis- an apparent visual magnitude of 4.71
6. Lambada Pyxidis– an apparent visual magnitude of 4.71
7. Zeta Pyxidis – an apparent visual magnitude of 4.86
8. Delta Pyxidis – an apparent visual magnitude of 4.87
The Bright Stars of Pyxis
The Bright Stars
If you look up and into the night sky you can imagine the recognizable outline of the Constellation of Pyxis, which is a compass.
This main constellation is made up of 10 main Stars
Stars with Planets
Pyxis has 4 Stars with an exoplanet orbiting around it in the solar system but they is unlikely to be able to support life forms.
The furthest exoplanet discovered was actually in the Andromeda Galaxy, not in the Milky Way.
Not all the stars within the Pyxis Constellation are visible to the naked eye but with telescopes and modern imagery techniques is it possible to glimpse all of the stars.
FACT: An exoplanet (also referred to as an extrasolar Planet) is a planet that orbits a Star that is not located within our Solar System (exoplanets do not orbit our Sun)
Nothing stands still in the sky.
Planets are continually being discovered and lists updated.
The Constellations change their positions throughout the year as the Earth rotates around the Sun.
This means our position in space is forever changing and as a result our view of what’s in space changes too, and will continue to do so.
What is the purpose of the Constellation of Pyxis –
In ancient times the dots, bright lights and perceived objects in the sky were of great interest and the makings of folklore to a great range of people from seamen to farmers.
From children to the elderly, we have had an ongoing fascination, with our solar system and star system. Perhaps it’s because the enormity and variety within it makes us realize just how large and exciting the universe is.
FACT: The Star System or Stellar System is a small number of stars that orbit around each other and are bound together by gravity.
When it becomes a large group of stars, again bound together in the same way, by gravity, it is known as a Galaxy or Star Cluster.
Whether they contain small groups of stars or larger groups of start the both come under the classification of ‘Star System’.
The Pyxis celestial pole
The celestial pole defines the poles of the celestial equatorial coordinate system.
An object at the Celestial pole has a declination of 0 degrees.
- The declinations for the north celestial pole is +90 degrees
- The declinations for the south celestial pole is -90 degrees
The celestial poles are not permanently in a fixed position against the background of the stars as everything moves in Space.
Pyxis is located in the Southern celestial sky at a +50 degree north and -90 degrees declination, and an average 9-hours right ascension.
Navigational tools in the sky
The many Constellations in the night sky were a useful navigation tool and guide as well as the subject of legends and myths.
42 of all the Constellations have been named after animals with a story behind each name.
Historical significance: surrounding Constellation of Pyxis
Many ancient civilizations have related the Constellations in the sky to suit their beliefs and creations itself. They have been the subject of folklore and experiences for a very long time.
Pyxis is not connected with any Greek or Roman myths or gods, however it has been connected with images and associations in other cultures based on the shape of a marine compass.
In the 18th Century when Nicolas Louis de Lacaille cataloged the Constellation of Pyxis, he positioned it close to the other Constellations that appear as a ship with a compass on the mast..
The two Constellations close by were Puppis, imagined as the hull of the ship and Vela known as the sail.
At that time John Hershel created a Constellation called Malus, but this Constellation is now obsolete.
Ancient associations with the constellations
The Greeks, the Romans and the Sumerians all had an interest in the constellations in the sky.
The Sumerians were the first literate civilization of the Ancient Mesopotamia (an area occupying parts of Turkey and the Syria of today, Iraq, Iran)
The Sumerian civilization was not unified like the ancient Greek or Roman civilizations it was bonded by a common attitude.
Their belief systems featured many deities. They regarded their gods as being responsible for everything and as such held them in great respect. Many stories arose as a result.
For thousands of years, various cultures around the world have identified and named the constellation we know and see in the night sky as Pyxis.
The Mesopotamian civilization (the first known civilization) identified constellations like Pyxis.
FACT: The ancient lands of the Mesopotamians now stretches across Turkey, Syria, Iraq and Kuwait
Pyxis and the other constellations in the sky had a practical use.
The ancient Mesopotamians and in Asia used the orientation of the constellations to set the seasons for sowing crops and harvesting.
The Babylonians also recorded details of various bright stars within the constellations in their Babylonian star catalogues before 100BCE.
What is the difference between a constellation and an asterism?
An asterism is a group of stars that appear to form a pattern in the night sky but with no officially determined boundaries.
It can make up part of a constellation or cross the boundaries of an official constellation or even a defunct constellation.
An asterism is a more vague assembly of stars than a recognized constellation.
The meteor showers for Pyxis
There are no annual meteor showers associated with the Constellation of Pyxis
Fun Facts about Constellations – Did you know that?
- The Constellation of Pyxis is not one of the 12 constellations of the Zodiac, that appear when the Sun sets
- The sky is not divided equally between all the constellations
- Constellations have been represented in many cultures as a sign for harvest time and as a navigational guide
- The old Constellation of Malus (the mast) no longer exists, it is now part of Pyxis
- Another constellation introduced in this area by Johann Bode, a German astronomer was called ‘Lochium Funis’ and was represented as the log and the line, and depicted as coiling around Pyxis. This Constellation is now obsolete.
- The compass is also significant in other cultures
- In the ancient Chinese culture, a Constellation called Tianmiao, the celestial temple that was dedicated to the Emperor’s ancestors from way back in time. The Chinese Constellation of Tianmiao had around 14 Stars, which are described as being in an arch shape in the area we know today as Pyxis and part of the neighboring Constellation of Antila.
- As the Constellation of Pyxis is made up of Stars that are in many different locations and vast distances from each other it is now possible to go to just one location to view it. It is visible from many different locations.
- The average distance to the main Stars in Pyxis is around 500 light years away.
- There are over 4000 known exoplanets in the night sky, with another 5000 awaiting classification
- The scale of a Constellation is measured in square degrees
- The planet Jupiter is often cited when making size comparisons between planets or stars. The Jupiter mass is a unit of mass equal to the total mass of planet Jupiter
- Charles Messier the French Astronomer who cataloged the Messier objects has a crater on the Moon named after him.
- Constellations like Pyxis are not part of our Solar System; they are groups of stars that appear to form shapes that are visible with the naked eye from Earth.
- The largest Constellation is called Hydra and the smallest Constellation is called Crux
- The Sun does not belong to any constellation.
- A Constellation does not actually exist as a fixed object, it is a group of bright stars that happen to be in a random place and are light years apart and ever moving. We see the pattern of their presence.
- The center of a Galaxy does not contain a Giant Star it contains a massive Black Hole.
- Red Dwarf is not a Dwarf Planet it is a Star. Most common Stars are Red Dwarf (cool Stars)
- Spiral Galaxies make up about two third of all the Galaxies in the Universe
Commonly Asked Questions
Q. What is the celestial sphere?
A. In astronomy and navigation terms, the celestial sphere is imaginary.
This virtual sphere has a large radius that is concentric with Earth.
We can imagine all objects in the night sky as being projected upon the inside of this celestial sphere, as if it has images placed inside a dome.
Q. What’s the difference between a Constellation and an asterism?
A. The stars that make up a Constellation have a definite position and form, whereas an asterism is a collection of stars without a fixed position
Q. What prevents us seeing the Stars and Constellations in the night sky?
A. Light pollution, fog, city lights and artificial lights all limit our visibility of the objects in the sky at night.
Q. Will the Constellations change over time?
A. The Constellations are continually on the move.
The images we form in our imagination to make objects, shapes and patterns out of the constellations have already shifted over time.
As we view the night skies from Earth they are likely to continue to shift and possibly in time the images may look very different.
- Photo by Andy Holmes on Unsplash – https://unsplash.com/s/photos/constellation