The Triangulum Constellation – Facts in brief
What is it? –
The Triangulum Constellation is regarded as one of the smaller constellations, and is located in the Northern Hemisphere.
It fills an area of 131.8 square degrees, which represents about 0.32% of the sky, making it the 78th largest Constellation in terms of size.
It is sometimes confused with a totally different Constellation called Triangulum Australe (Triangulum as), which is located in the Southern Hemisphere.
The Triangulum Constellation is regarded as a fairly old constellation, as it is one of the original 48 Constellations listed by Greek Astronomer Ptolemy, in the 2nd century.
Triangulum is also one of the official International Astronomical Union (IAU) listed 88 modern constellations as seen in the night sky from Earth.
The Constellation of Triangulum is a member of The Perseus family, of Constellations, which also includes:
The name of this Constellation ‘Triangulum’ has associations with Greek and Roman culture.
The Ancient Greeks referred to the Triangulum Constellation as ‘Triangulum Deltoton’ as it resembles the shape of an upper case letter of the Greek alphabet – Delta
The Constellation of Triangulum
The name ‘Triangulum’ is Latin for ‘the ”triangle’
Triangulum is abbreviated to ‘Tri’, or ‘Trianguli’ (its Latin genitive name) and is quite easy to recognize, as it resembles the outline of the Triangle.
Where is it located? –
The Triangulum Constellation is positioned in the first quadrant of the Northern Hemisphere, north of the celestial equator.
It is sometimes referred to as being located in the NQ1 Quadrant, of the Northern Sky.
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 Triangulum Constellation contains a very large galaxy called the ‘Triangulum galaxy’; only the Milky Way and the Andromeda Galaxy are bigger.
Triangulum is not actually a part of the Milky Way but it is located close behind it.
The Milky Way contains the following Constellations:
In the Northern Hemisphere:
- At the top – Aquila; Ophiuchus; Sagittarius and Scorpius
- Close to the Centre – Cygnus and Lacerta
- Off the bottom – Perseus and Cassiopeia
In the Southern Hemisphere:
A faint section of the Milky Way is also visible in the Constellations of Canis Major, Orion and Puppis.
The Constellation of Triangulum is not circumpolar, meaning it is not visible all year round in the Northern latitudes.
There are 5 Constellations, some of which are neighbors of Triangulum, 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 –
- Carina Constellation
- Centaurus Constellation
- Crux Constellation (the smallest modern constellation listed by the International astronomical Union (IAU).
Locating a Constellation
It can seem daunting at times trying to locate your favorite Constellation in the great night sky.
However, if you can imagine an invisible coordinate grid draped over the dark sky it becomes easier.
Using the longitude and latitude coordinates of this grid it is possible to locate Constellations, the Asterisms of Main Stars and other Deep Sky Objects.
Co-ordinates of a right ascension, or left ascension and their declination are used to locate all of the Constellations, like Triangulum.
Triangulum is most prominent in the Northern Hemisphere, during the month of December.
The Constellation of Triangulum lies between a 01.hour 31.3m – 02.hour 50.4m right ascension (RA) and a Declination (Dec.) range of 25.60-37.35 square degrees.
It’s visible from the Northern Hemisphere at Latitudes between +90 degrees and – 60 degrees and covers an area of 132square degrees.
The Triangulum Constellation is bordered by several other Constellations:
- Andromeda – to the Northeast
- Pisces- to the Southeast
- Aries– to the Southwest
- Perseus – to the Northwest
It is visible in very dark sky conditions in the Northern Hemisphere during the winter months, around 21.00 in the evening.
How can you identify The Constellation of Triangulum?
The simplest method for spotting any particular Constellation from Earth is to locate the brightest star in that Constellation, and then look at the neighboring illuminations, to see if you can identify a recognizable pattern.
The reason that the Constellation of Triangulum is considered to be a faint Constellation is because the main Stars are of moderate brightness.
Triangulum has two formally named Stars, approved by the International Astronomical Union (IAU), they are called:
Stars in any Constellation are usually listed in order of luminosity from the brightest Star to the faintest Star.
In the Bayer classification of Stars the ‘Alpha’ letter is normally allocated to the brightest star, then ‘Beta’ and so on in decreasing order through the letters of the Greek alphabet.
- In the Constellation of Triangulum the brightest Star is called Deltoton (or Deltotum), but it has been allocated the Bayer designation of Beta Trianguli.
- The second brightest Star is known as Mothallah (Matallah or Ras al Mothallah from Arabic), it has been allocated the Bayer designation of Alpha Trianguli.
There are a total of 322 Stars that make up the Triangulum Constellation.
There are no first magnitude Stars within Triangulum.
The brightest Star in Triangulum is Beta Trianguli with an apparent visual magnitude of 3.00, which is considerably dimmer than a first magnitude Star.
FACT: First magnitude Stars are the brightest stars in the night sky with an apparent magnitude of less than 1.50.
It was Hipparchus, in the 1st century B.C. that developed the magnitude scale that ranks the luminosity of the bright Stars that are visible to the naked eye.
The 20 brightest Stars were allocated the first magnitude value, through to the faintest Stars that are still visible to the naked eye ranked as sixth magnitude Stars.
There are 300 known bright Stars in the sky with an apparent magnitude of 3.55 or brighter.
The Triangulum Constellation can be identified in the night sky as the shape of a long slim triangle.
It is also represented in other cultures, such as ‘a Great General’ or an ‘object of honor’
The brightest star, beta Tri, can be viewed from Earth, from a northern location, by the naked eye.
The Star System within Triangulum
The Constellation of Triangulum has 3 main Stars making up the shape of ‘the triangle’.
The bright stars forming the shape of the constellation known as the triangle, are listed from brightest Star to the fainter stars by a variety of designations – Bayer, Flamsteed and the Henry Draper Catalogue.
- The Bayer designation – allocates a letter of the Greek alphabet to the genitive to name a star – Alpha Trianguli
- The Flamsteed designation – allocates a number to the genitive to name a star – like 14 Trianguli
- The Henry Draper designation – allocates the abbreviation ‘HD’ and a number to name the star – like HD 10390
The main Stars forming the Constellation of Triangulum
1. Deltoton (Beta Trianguli, B Tri), –
A Binary Star, (a Double Star) 127 light years distant, from Earth and visible by the naked eye
2. Mothallah (alpha Trianguli, a Tri)
A spectroscopic Binary Star, a Sub giant, 63.3 light years from the Sun, and visible by the naked eye
3. Gamma Trianguli (Gamma Tri)
An A-type main sequence Star, 112 light years from Earth, and forms an optical line of site with 2 other Stars – Delta Trianguli and 7 Trianguli, known as an optical triple)
4. Delta Trianguli
A spectroscopic Binary Star, (where primary Star is a yellow dwarf and secondary Star is an orange dwarf star), located 35 light years distant from the Constellation of Triangulum and visible by the naked eye
5. Iota Trianguli (TZ Trianguli)
A Variable Star, 155 light years distant
After this magnitude it becomes barely possible to see further stars in the Constellation of Triangulum by the naked eye.
6. 14 Trianguli
A variable Star, 391 light years distant, and barely visible by the naked eye
7. 7 Trianguli
A Star, 293 light years distant, and barely visible by the naked eye
8. 10 Trianguli (HR 8523)
A Star, 350 light years distant, and barely visible by the naked eye
9. 12 Trianguli (HR 8541)
A Star, 155 light years distant, and barely visible by the naked eye
The only other Bayer named Star in this Constellation is Epsilon Trianguli (e Trianguli).
It is a Binary Star, also known as a multiple Star System that appears as a singe point of light. Its 2 Stars have apparent magnitudes of +5.50 and +11.4 and is located around 390 light years from Earth.
There are 3 named Star within Triangulum, although only 2 have been approved by the International Astronomical Union (IAU):
- Mothallah and Horna are approved names by the IAU
- Deltoton is not an approved name of this Star, (Beta Trianguli) by the IAU. Beta Trianguli is the brightest Star in Triangulum
- Delta Trianguli is the closest to Earth, and has an exoplanet, known as HD 9446
- HIP 13148 is the furthest Star, from the Sun
- HD 10348 is the dimmest Star in Triangulum that can still be seen by the naked eye
Location of Triangulum
Triangulum can be spotted in the Northern Hemisphere, also referred to as the Northern Sky.
The Constellation Triangulum is positioned between the easily recognizable Constellations of Andromeda and Perseus
The Triangulum Constellation is used as a guide-point in the sky used by astronomers and amateur stargazers to identify certain Deep Sky objects.
When to see the Constellation Triangulum
The Constellation of Triangulum is sometimes referred to as an inconspicuous winter Constellation in the Northern Sky. The best month to view Triangulum at its best is in the month of December.
The best time to spot it is in a dark sky (21.00 Daylight Saving Time) local time around the world.
How was it formed, found and named?
The word ‘Triangulum’ is referred to a triangle, which is the apparent shape of this Constellation.
The outline of Triangulum
The outline of this long thin triangle representing the Constellation of Triangulum comes from the position of its 3 main Stars.
You will have to use your imagination using the position of the Stars in this asterism, to imagine its image as a large triangle, they are:
- Beta Trianguli, Alpha Trianguli and Gamma Trianguli
What’s within the Triangulum Constellation?
Constellations are typically formed by of a number of different components – mainly Stars, Star Systems, Deep Sky Objects and Messier objects (galaxies).
The Triangulum Constellation contains:
- 3 named Stars
- 3 Stars in the outline
- 18 Bright Stars
- 14 Bayer/Flamsteed Stars
- 322 Stars in total (but only around 18 are visible by naked eye)
- 3 star systems with a known planet
- No meteor showers associated with this Constellation
- 1 Messier Objects
- No Global Clusters
- No Stars with an apparent magnitude brighter than +3.00
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.
Locating the ‘triangle-shape’ bright Stars in the dark sky usually identifies the Triangulum Constellation.
It should not be confused with another Constellation with a similar name ’Triangulum Australis’, (Triangulum as), as they are different.
Deep Sky Objects
Triangulum has deep sky objects, including objects from the Messier New General Catalogue (abbreviated to NGC) and from the Index Catalogue (IC):
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 Messier?
A Messier is a cluster of Stars
Charles Messier, a French astronomer, is credited with cataloging each of the Messier Star clusters, in 1764, for many Constellations.
There is only one Messier object within the Constellation of Triangulum.
Messier 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).
These later became known as Messier objects.
The Triangulum Galaxy
The Triangulum Galaxy (Messier 33) is a distant member of the Local group of Galaxies. It has an apparent magnitude of 5,8 (which would usually be visible by the naked eye) but is difficult to see by naked eye, as it is a diffuse object.
It is sometimes referred to as the ‘Pinwheel Galaxy’.
The ‘Local Group of Galaxies’ is the galaxy group that includes the two clusters of galaxies that form a ‘dumbbell shape’.
The Triangulum Galaxy is the third largest member of the local group.
These two spiral galaxies are the ’Milky Way’ and the ‘Andromeda Galaxy’.
Within the Local group of Galaxies there at least 80 other galaxies, mainly dwarf galaxies.
FACT: The term, ‘The Local Group’ of galaxies was first mentioned by Edwin Hubble in his book “The Realm of the Nebulae”, where he described it as a typical small group of nebulae.
NGC 925, also known as the Amatha Galaxy, is a barred spiral galaxy within Triangulum and located around 30 million light years away.
It has a bar structure and loosely wound spiral arms, but with no ring.
A star cluster is a large group of Stars that can be Globular Clusters or Open Clusters:
Global clusters (a spherical collection of ‘Old Stars,’) numbering hundreds to millions are tightly bound by gravity and orbit a galactic core
An open Cluster is a looser formation of ‘Young Stars’ that generally has less than a few hundred Stars.
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).
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
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 various Nebulae have been captured using professional Space telescopes, such as the NASA Spitzer Space Telescope, operated by NASA, and the famous Hubble Space Telescope.
Triangulum is often abbreviated to ‘Tri’ from a naming convention used by NASA.
Background & Facts:
The Greeks were the first ancient culture to name the modern 88 Constellations in the sky.
It was the Greek Astronomer – Ptolemy, who first cataloged 48 early constellations, in the 2nd Century (2 AD.).
Ptolemy listed the various constellations in his Almagest (a book recording astronomical data). He identified and listed Triangulum.
In 1603, The German Astronomer – Johann Bayer, systematically assigned names to many bright stars in Triangulum and then cataloged them in his Star atlas – ‘Uranometria Omnium Asterismorum’.
The Bayer designations are stellar designations where the stars within Constellations are initially identified by a name or letter from the Greek Alphabet from Alpha through Omega (in descending order of brightness).
The names of the Stars beginning with a letter of the Greek alphabet and are followed by the genitive form of their parent constellation’s Latin name, making ‘Trianguli’
However the first Star, with the brightest apparent magnitude is Beta Trianguli, not the Star Alpha Trianguli
The main Stars of Triangulum are listed by their apparent magnitude (luminosity) in decreasing order:
1. Beta Trianguli – an apparent visual magnitude of 3.0
2. Alpha Trianguli – a variable visual magnitude of 3.42
3. Gamma Trianguli – an apparent visual magnitude of 4.03
4. Delta Trianguli – an apparent visual magnitude of 4.84
5. Iota Trianguli – an apparent visual magnitude of 4.94
6. 14 Trianguli – an apparent visual magnitude of 5.15
7. 7 Trianguli – an apparent visual magnitude of 5.25
8. 10 Trianguli – an apparent visual magnitude of 5.29
9. 12 Trianguli – an apparent visual magnitude of 5.29
10. 15 Trianguli – an apparent visual magnitude of 5.38
It was the Polish astronomer Johannes Hevelius who picked out 3 faint Stars to form the Constellation of Triangulum Minus – 6 Trianguli, 10 Trianguli and 12 Trianguli.
At this point in 1690 Johannes Hevelius renamed the original as ‘Triangulum Majus’, in his ‘Firmamentum Sobiescianum’ catalogue.
The Bright Stars of Triangulum
If you look up and into the night sky you can imagine the recognizable outline of Constellation Triangulum as a triangle-shape.
Stars with Planets
Triangulum has 3 Stars with an exoplanets orbiting around it in the solar system but it is unlikely to be able to support life forms.
Not all the stars within the Triangulum 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 Triangulum? –
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 Triangulum 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.
Triangulum is located in the northern celestial sky at a +30 degree north declination, and an average 2 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 the Constellations have been named after animals with a story behind each name.
Historical significance: the legends, and myths
The importance of the Constellations dates way back to the times of the Babylonians who identified constellations with bright Stars.
Triangulum has been described in many different ways by many cultures.
The Babylonians recorded details of various bright stars within the constellations in their Babylonian star catalogues before 100 BCE.
In this Babylonian Star Catalogue ‘Triangulum’ and ‘Gamma Andromedae’ formed a constellation called ‘Mulapin’ in Arabic meaning ‘the Plough’. It is associated with the time of harvest.
In Mesopotamia it represented the time to begin spring ploughing of the fields.
Triangulum is not the subject of Greek or Roman mythology, as such, although many ancient civilizations had their own way of describing what they could see in the night sky.
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.
Yet, the theme across the cultures was ‘the triangle’.
The Greek astronomer, Eratothenes of Cyrene, linked the shape of Triangulum to the shape of the triangular Nile Delta.
The Roman astronomer, Hyginus, linked the shape of Triangulum to the triangular shape of the Island of Sicily. (Sicilia).
The Romans believed Ceres, the goddess of agriculture and grain crops, and the patron goddess of Sicily, was the one who begged Jupiter to place her Island of Sicily (Sicilia) into the heavens.
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.
FACT: The ancient lands of the Mesopotamians now stretches across Turkey, Syria, Iraq and Kuwait
Triangulum and the other constellations in the sky were not only the subject of legends but they had a practical use too.
The ancient Mesopotamians and in Asia used the orientation of the constellations to set the seasons for sowing crops and harvesting.
They believed that the appearance of the triangle in February signaled the time to start the Spring ploughing of the fields in Mesopotamia.
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 show
There are no annual meteor showers associated with the Constellation of Triangulum
Fun Facts about Constellations – Did you know that?
- The Constellation of Triangulum is not one of the 12 constellations of the Zodiac.
- Triangulum is also significant in other cultures – In Arabic culture it is known as the plough
- In Chinese astronomy the Constellation of Triangulum is associated with the ‘The General of Honor’
- Triangulum is represented in many cultures as a sign for harvest time and as a navigational guide.
- Ptolemy and Hipparchos called it Trigonon, while the Romans called it Trigonum
- The furthest exoplanet discovered was actually in the Andromeda Galaxy, not in the Milky Way.
- 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
- The Constellation of Triangulum is the 78th largest and occupies around 0.3% of the night sky
- Charles Messier the French Astronomer who cataloged the Messier objects has a crater on the Moon named after him.
- Constellations like Triangulum 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.
- 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.
- Spiral Galaxies make up about two thirds 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 sky 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