Cassiopeia Constellation

Queen Cassiopeia of Aethiopia is one of the most recognisable constellations because of its prominence in the north sky. There are 5 bright stars in close proximity which makes it one of two main methods of identifying the polar north star of Polaris. The constellation is visible year around in the northern hemisphere and is such considered a circumpolar constellation as it appears to rotate around the north star.

Cassiopeia is linked to many other constellations through Greek mythology. She was the wife of King Cepheus, the mother of Andromeda, and the mother in law of Perseus.

Cassiopeia constellation is one of the original 48 constellations listed by the Egyptian mathematician Ptolemy, who lived under Roman rule in Alexandria in the 2nd century. These constellations formed the basis for the modern list agreed by the IAU. Constellations from the southern hemisphere, unable to be seen from the Mediterranean, represent the majority of additions to the list.

As the earth moves in its orbit around the sun, each night you are looking at a different portion of the sky. When looking at stars it is important to be aware of what is within your view. Northern hemisphere stargazers can group constellations into 3 groups; circumpolar, summer and winter constellations. The circumpolar constellations are in the north sky, appear to move around the north star and are visible throughout the year. The constellations in the south sky are only visible for part of the year and are grouped as either summer or winter constellations. Each is visible from between 4 to 10 months.

It is important to be aware of the specific time of year and hour of the night when deciding what to look for. These pages below show the constellations in each group so you can find the constellations that interest you.

CIRCUMPOLAR (year around) – Ursa Major – Cassiopeia – Ursa Minor – Draco – Cepheus

WINTER – Pegasus – Pisces – Aries – Auriga – Taurus – Orion – Canis Major  – Canis Minor – Gemini – Lynx – Cancer – Leo – Winter Hexagon

SUMMER – Virgo – Libra – Scorpius – Bootes – Hercules – Lyra – Ophiuchus – Sagittarius – Aquila – Cygnus – Capricornus – Aquarius

Or use this guide to easily see which constellations are easiest to find right now:

BEST CONSTELLATIONS TO FIND THIS MONTH

Cassiopeia Quick Facts:

Symbolism: Seated Queen

Neighbouring constellations: Ursa Minor*, Cepheus*, Perseus (south east), Pegasus (south west). 

Brightest star: Navi, 2.15 magnitude (63rd brightest star in night sky)

Stars brighter than 3 magnitude: 4

Primary stars: 5 (the 5 stars form a W shape, on an angle they are viewed as a profile of a throne)

Latitude: 55 – 65 degrees north

Northern Hemisphere Season: Circumpolar (year round)

*Circumpolar constellations do not maintain the same coordinal direction to each other as they all rotate around the north star Polaris in the constellation Ursa Minor. The direction however can always be determined from the constellation with the top of the W pointing to the north star.

Which months can you see Cassiopeia constellation?

Cassiopeia can be seen all year but can be found high in the sky at 21:00 from October to January:

• Early evening viewers (pre 21:00) can find the constellation from September in the north east sky until February in the north west sky. Cassiopeia will be visible overhead from November to December.
• Mid evening viewers (21:00-23:30) can find the constellation from August in the north east sky until January in the northwest sky. Cassiopeia will be visible overhead in from October to November. 
• Late evening viewers (after 23:30) can find the constellation from July in the north east sky until December in the north west sky. Cassiopeia will be visible overhead from September to October.
• Early morning viewers can find the constellation from May in the north east sky to October in the north west sky. Cassiopeia will be visible overhead from from July to August.

As time passes the constellation will gradually appear earlier in the day with ranges below showing the window of opportunity in each month. Cassiopeia sits between 55-65 degrees north latitude. Therefore, the further south your position the lower it will appear in the north sky. At its maximum range it is possible to see Cassiopeia at latitudes between +90 and -20. Above Latitudes of 45 degrees north the constellation remains above the horizon at all times.

Best time to see Cassiopeia:

Present throughout night from October to November

Best visible at 21:00 from October to January

January: visible in the north sky at sunset 60 degrees above horizon. It will rotate towards the horizon, dropping too low in the sky to observe after 01:00.

February: visible in the north west sky at sunset 50 degrees above horizon. It will rotate towards the horizon, dropping too low in the sky to observe after 23:00.

March: visible in the north west sky at sunset 30 degrees above horizon. It will rotate towards the horizon, dropping too low in the sky to observe after 21:00. It will return to 15 degrees above the north east horizon at sunrise.

April: visible in the north west sky at sunset 15 degrees above horizon. It will rotate towards the horizon, dropping too low in the sky to observe after 20:00. It will return to 15 degrees above the north east horizon at 04:00, increasing to 25 degrees by sunrise.

May: in the evening sky the constellation will be very low on the horizon and difficult to observe. It will return to 15 degrees above the north east horizon at 02:00, increasing to 35 degrees by sunrise.

June: in the evening sky the constellation will be very low on the horizon and difficult to observe. It will return to 15 degrees above the north east horizon at 24:00, increasing to 45 degrees by sunrise.

July: in the evening sky the constellation will be very low on the horizon and difficult to observe. It will return to 15 degrees above the north east horizon at 22:00, increasing to 60 degrees in the north sky by sunrise.

August: in the early evening sky the constellation will be very low on the horizon and difficult to observe. It will return to 15 degrees above the north east horizon at 20:00. It will reach its peak at 04:00, and return to 60 degrees in the north sky by sunrise.

September: visible in the north east sky at sunset 25 degrees above horizon. It will reach its peak at 02:00, and return to 45 degrees in the north west sky by sunrise.

October: visible in the north east sky at sunset 35 degrees above horizon. It will reach its peak at 24:00, and return to 30 degrees in the north west sky by sunrise.

November: visible in the north east sky at sunset 45 degrees above horizon. It will reach its peak at 21:30, and return to 15 degrees in the north west sky by 05:00.

December: visible in the north east sky at sunset 60 degrees above horizon. It will reach its peak at 19:30. It will rotate towards the horizon, dropping too low in the north west sky to observe after 03:00.

Trajectory: The constellation is between 55-65 degrees north, placing it around degrees from Polaris. The constellation will rotate around the northern star maintaining its distance. As such viewers can expect it to follow an arch from the north east horizon arching across the north east sky until it reaches its peak high in the north sky, then following a parallel arch in the north west sky until it reaches near to the north west horizon. Those at very high northern hemisphere latitudes may also be able to view it cross low in the north sky to complete its rotation. Its peak trajectory in Wadi Rum is 70 degrees above the northern horizon and is viewable in the evening from November to January.

Not the right time for Ursa Major? Have a look what constellations you can see tonight.

How to find Cassiopeia constellation?

Difficulty to find: Easy – Difficulty to interpret: Medium-Hard – Locating asterism: Big Dipper (saucepan)

Cassiopeia is a collection of 5 bright stars near to each other in the north sky and is one of the easiest constellations to find without any aides.

You will looking for 5 stars zigzagging in the north sky to form a W shape. Depending on the position of this constellation the W could be facing any direction. However depending on you latitude it should always be around 30 degrees from the point directly north and above the horizon equal to your latitude. For viewers in Wadi Rum that is around 30 degrees. That point is the north star and Cassiopeia constellation appears to be circling it. The top of the W will always be facing that point so when it is highest in the sky it will appear as an M, in the north east sky it will appear as a 3 and in the north west sky it will appear as an E.

Step 1: Make sure you are familiar with what time of night the constellation will be in the sky for the time of year you are looking. Use the guide above to confirm the cycles and the appropriate area of the sky

Step 2: The constellation will always be in the north sky so orient yourself with a clear view of the sky to the north

NOTE: All 5 stars in Cassiopeia are among the 200 brightest visible from earth (including those in the southern hemisphere that you never see and those that pass in the day so they are all very clear)

Step 3: There will be very few groupings of bright stars within your view if you followed the previous steps and are looking at the right time and in the right direction. The only other candidate will be those of the Big Dipper in the Ursa Major constellation. The Big Dipper is 7 stars and does not appear as a W so you can now use that to guide you. Cassiopeia should be on the opposite side of the north star from Ursa Major. If you cross the point of the north star to a similar distance on the opposite side of the north star you should find Cassiopeia. If Ursa Major is directly above the north star then you will need to look directly below it towards the northern horizon. If you are at a low latitude and have determined that it is below your point of visiblity you may need to come back later in the night. The circumpolar constellations are rotating anticlockwise and move at around the same speed as the hour hands on a clock so you can determine the movement.

Cassiopeia now known can be used to locate other constellations and determine the coordinal direction. Until last century it was one of the primary guides for night time navigation in the northern hemisphere. As it is opposite the Big Dipper, one of these two bright star groupings is always visible in the northern hemisphere sky and can be used to locate the north star.

Learn how to form the shape of Cassiopeia constellation

Cassiopeia is one of the easiest stars to identify the shape of as all of its stars are bright. Rather than requiring the identification of  a specific star and using this to find the shape, Cassiopeia is identifiable from its shape. Although the form itself a basic W and difficult to visualise as the seated queen explained by Ptolemy it is a convenient grouping to locate and highly effective navigational tool in the northern hemisphere

Cassiopeia in the Ancient World

Greek mythology

Cassiopeia is the queen of Aethiopia, which was a historic region of the upper Nile and where modern day Ethiopia derives its name. She shared the throne with King Cepheus and now share neighbouring constellations in the night sky.

Cassiopeia is best is known from Greek mythology from the story of Perseus. Cassiopeia made claim that her daughter Andromeda was as beautiful as Poseidon’s sea nymphs. Poseidon was angered by this and sent Cetus a sea serpent to kill Andromeda. Cetus destroyed everything in his path as he searched the lands for Andromeda. It was told that the only way to stop Cetus was to sacrifice Andromeda so she was chained naked to a rock. Perseus came to the rescue of Andromeda, killing Cetus and setting her free.

Perseus then decided to wed Andromeda despite her previously agreeing to a marriage with Phineus. At the wedding a conflict broke out and Perseus turned Phineus to stone with the head of Medusa which he had cut off in an earlier quest. 

Main stars of Cassiopeia constellation

Navi (+2.15, 550ly, 1k suns, #63)

Navi is a modern name given by NASA that is Ivan spelt backwards after astronaut Grissom who was one on the first manned shuttle into space and was also the first person to enter space twice before dying in the failed Apollo 1 launch. It has a very significant range of brightness but is considered the 63rd brightest star. It has an apparent magnitude of +2.15 but can vary from +1.6 to +3.0. The distance from earth is 550 light years. It is 43 times the size of the sun. Navi marks the middle of the W.

Navi has a number of unusual attributes to consider:

• Despite being a very bright star and one of the main navigational stars in the sky it did not inherit any name from the Greek, Latin or Arabic astronomers who named almost all noteworthy stellar objects. As such it was named in modern times as a honour of NASA astronauts who died int the Apollo 1 launch. The lead astronauts middle name was Ivan which reversed is Navi and it was a key star used in missions for navigating.
• The star has an significant variance in brightness which makes its ranking of brightness contested. At its brightest it is the 24th brightest star. At its dimmest it is 176th.

Schedar (+2.24m, 228ly, 93k suns, #71)

Schedar is from Arabic meaning ‘breast’ due to its position in the queens chest. It is the 32nd brightest star with an apparent magnitude of +2.24. The distance from earth is 228 light years. It is 93,500 times the size of the sun. Schedar is the star at the base of the second V or at the bottom of the second downstroke of the W

Caph (+2.27m, 55ly, 43 suns. #74)

Caph is from Arabic meaning ‘palm’ (of the hand) with historic texts noting that it originated  as a reference to the 5 stars together’. It is the 74th brightest star with an apparent magnitude of +2.27. The distance from earth is 55 light years. It is 43 times the size of the sun. Caph marks the star at the end of the W.

Rukbat  (+2.66m, 99ly, 60 suns, #109)

Rukbat or Ruchbah is from the Arabic for ‘knee’ which is a shared name with a star in Sagittarius constellation. It is the 109th brightest star with an apparent magnitude of +2.66. The distance from earth is 99 light years. It is 60 times the size of the sun. Rukbat marks the star at the bottom of the first downstroke of the W.

Segin (+3.37, 410ly, 200 suns, #245)

Segin which has disputed pronunciation and rather than having a clear meaning is assumed to have been a historic mistranslation between Greek, Latin and Arabic by past astronomers. It is the 245th brightest star with an apparent magnitude of +3.37. The distance from earth is 410 light years. Segin is 200 times the size of the sun. Segin marks the star at the beginning of the W.

Wadi Rum is one of the best locations in the world to see the full beauty of the stars. Combining high altitudes, clear skies and no light pollution. You may be surprised how many stars are visible to the naked eye. Come with us and spend a night under the stars.