Cepheus (constellation) facts for kids

Quick facts for kids
Cepheus

Constellation
List of stars in Cepheus
Abbreviation	Cep
Genitive	Cephei
Pronunciation	or genitive
Symbolism	the King/King Cepheus
Right ascension	20h 01m 56.4481s–09h 03m 19.7931s
Declination	88.6638870°–53.3532715°
Area	588 sq. deg. (27th)
Main stars	7
Bayer/Flamsteed stars	43
Stars brighter than 3.00m	1
Stars within 10.00 pc (32.62 ly)	3
Brightest star	α Cep (Alderamin) (2.45m)
Messier objects	0
Meteor showers	0
Bordering constellations	Cygnus Lacerta Cassiopeia Camelopardalis Draco Ursa Minor
Visible at latitudes between +90° and −1°. Best visible at 21:00 (9 p.m.) during the month of November.

Cepheus is a constellation found high in the northern sky. It is named after King Cepheus, a legendary ruler from Greek mythology. He was the king of a land called Aethiopia.

This constellation was first listed by the astronomer Ptolemy in the second century. Today, it is still recognized as one of the 88 modern constellations.

The brightest star in Cepheus is called Alderamin, also known as Alpha Cephei. It shines with an apparent magnitude of 2.5. Another special star, Delta Cephei, is the original example of a group of stars called Cepheid variables. These stars change their brightness in a regular way.

Cepheus is also home to some of the biggest stars we know. These include RW Cephei, an orange hypergiant, and several red supergiants like Mu Cephei and VV Cephei.

Beyond stars, Cepheus contains an incredibly bright object called a quasar named S5 0014+81. At its center is a super-duper massive black hole. This black hole is about 40 billion times heavier than our Sun. That makes it about 10,000 times more massive than the black hole at the center of our own Milky Way galaxy! It is one of the most massive black holes ever found.

History and Myth of King Cepheus

In ancient Greek stories, Cepheus was the King of Aethiopia. He was married to Queen Cassiopeia. They had a daughter named Andromeda.

All three of them – Cepheus, Cassiopeia, and Andromeda – are remembered in the night sky. They are all constellations we can see today.

Exploring the Stars of Cepheus

The constellation Cepheus as it may be seen with the naked eye.

Cepheus is filled with many interesting stars. Let's take a closer look at some of them.

Bright Stars and Variable Wonders

Alderamin, or Alpha Cephei, is the brightest star in this constellation. It has an apparent magnitude of 2.51.

Gamma Cephei, also known as Errai, is the second brightest star. Its apparent magnitude is 3.21. Errai is a binary star, meaning it's actually two stars orbiting each other. One is an orange giant or subgiant, and the other is a red dwarf. The main star also has a planet orbiting it, called Gamma Cephei Ab (Tadmor).

Delta Cephei is a yellow supergiant star, about 980 light-years from Earth. It is the most famous example of a Cepheid variable star. These stars get brighter and dimmer in a very regular pattern. This pattern helps scientists measure distances in space.

John Goodricke discovered Delta Cephei was a variable star in 1784. Its brightness changes between magnitude 3.5 and 4.4. This cycle takes about 5 days and 9 hours. Delta Cephei changes size as it pulsates. Its size varies from 40 to 46 times the diameter of our Sun. It is also a double star, with a fainter blue companion star.

Giant Stars and Stellar Explosions

Cepheus is home to four red supergiant stars that you can see without a telescope.

Mu Cephei is often called the Garnet Star because of its deep red color. It is a variable star, changing brightness between magnitude 5.1 and 3.4. Its cycle takes about two years. This star is enormous, with a radius between 972 and 1420 times that of the Sun. If it were in our Solar System, it would reach past the orbit of Jupiter.

VV Cephei A is another variable red supergiant, about 5,000 light-years away. It changes brightness between magnitude 5.4 and 4.8. It has a blue companion star called VV Cephei B. The red supergiant is about 1,050 times larger than the Sun. VV Cephei is also an eclipsing binary system. This means one star passes in front of the other, but these eclipses are too faint to see with your eyes.

Zeta Cephei is the fourth brightest star in the constellation, with a magnitude of 3.35. It is smaller than Mu Cephei and VV Cephei A, with a diameter less than 200 times that of the Sun. If it were at the center of our Solar System, its surface would be between the orbits of Venus and Earth.

The last of these visible red supergiants is V381 Cephei Aa. It has a maximum brightness of magnitude 5.5. This star is part of a triple star system and is about 980 times larger than the Sun.

All these four giant stars are expected to end their lives in a huge explosion called a supernova. This happens because they are much more massive than our Sun.

Nu Cephei is a blue supergiant star. It is similar to the bright star Deneb. Nu Cephei started with more than 20 times the mass of our Sun. It belongs to a group of stars called the Cepheus OB2 stellar association.

Double Stars and Nearby Neighbors

Cepheus also features several interesting double stars and binary stars.

Omicron Cephei is a binary star system. Its two stars orbit each other over 800 years. This system is 211 light-years from Earth. It includes an orange giant star (magnitude 4.9) and a smaller companion (magnitude 7.1).

Xi Cephei is another binary star, 102 light-years away. Its stars take about 4,000 years to complete one orbit. It has a blue-white main star (magnitude 4.4) and a yellow companion (magnitude 6.5).

Krüger 60 is a binary star system that is quite close to Earth, only 13 light-years away. It consists of two red dwarf stars, both too faint to see without a telescope (magnitude 11). Scientists once thought it might be the home system for 2I/Borisov, a comet that came from outside our Solar System. However, this idea was later found to be incorrect.

Cepheus C & B Regions – Spitzer Space Telescope (30 May 2019)

Amazing Deep-Sky Objects in Cepheus

Emission nebula in Cepheus seen by the Northern Sky Narrowband Survey.

NGC 7354 is a planetary nebula located in the constellation Cepheus.

The constellation Cepheus is a busy place in space. It has many areas where new stars are forming. It also has many glowing clouds of gas and dust called nebulae. Most of these amazing structures are found in the Orion Arm of our Milky Way galaxy. They are roughly 2,800 to 3,600 light-years away.

Star Clusters and Galaxies

• NGC 188 is an open cluster of stars. It is the closest open cluster to the North Celestial Pole. It is also one of the oldest open clusters known.
• NGC 6946 is a spiral galaxy often called the Fireworks Galaxy. This is because ten huge star explosions, called supernovae, have been seen there. That's more than in any other galaxy!
• IC 469 is another spiral galaxy. It has a bright, oval-shaped center and faint spiral arms.

Nebulae: Cosmic Clouds

• The nebula NGC 7538 is special because it holds the largest protostar ever found. A protostar is a star that is still in its very early stages of formation.
• NGC 7023 is a beautiful reflection nebula. It glows by reflecting light from nearby stars. It has a star cluster (Collinder 429) within it. This nebula is 1,400 light-years from Earth.
• Sh 2-155, also known as the Cave Nebula, is a faint and spread-out bright nebula. It is part of a larger cloud complex that includes glowing, reflecting, and dark nebulae.
• Sh 2-131 is a glowing cloud of gas lit up by stars from the IC 1396 cluster. Inside this cloud is a dark nebula called the Elephant’s Trunk.
• NGC 7822 (also called Sh 2-171) is an H II region. This is a cloud of ionized hydrogen gas where new stars are being born. It appears about 3 degrees wide in the sky.

Powerful Quasars and Black Holes

• The quasar 6C B0014+8120 is one of the most powerful objects in the entire universe. It gets its energy from a supermassive black hole that is as heavy as 40 billion Suns!

How We See Cepheus

Cepheus as depicted in Urania's Mirror, a set of constellation cards published in London, c. 1825.

Cepheus is often shown in pictures with his arms raised. This represents him praying to the gods to save his daughter, Andromeda. Sometimes, he is also shown as a grand king sitting on his throne.

Cepheus in Other Cultures

In Chinese astronomy, the stars that make up Cepheus are part of two different areas. These are the Purple Forbidden enclosure (紫微垣, Zǐ Wēi Yuán) and the Black Tortoise of the North (北方玄武, Běi Fāng Xuán Wǔ).

Names Inspired by Cepheus

USS Cepheus (AKA-18), named after the constellation.

The name Cepheus has been used for several things:

• Two ships of the United States Navy were named after the constellation: USS Cepheus (AKA-18) and USS Cepheus (AK-265).
• Update 3.4 of the video game Stellaris was also named "Cepheus".

See also

In Spanish: Cefeo (constelación) para niños