Cancer is a group of stars.
It looks like a crab. The stars are hard to see. They are very dim. You can look for them at night. Do you like looking at stars?
Cancer is a group of stars.
It looks like a crab. The stars are very dim. They are hard to see in the city.
This group has a special part called the Beehive Cluster. It looks like a bunch of stars together. It is near the middle of the crab. One star in this group has five planets. Some of those planets might be like Earth. You can see these stars in the spring.
It is a fun part of the sky to find.
Cancer is a group of stars in the sky.
Its name is Latin for crab. It is one of the twelve zodiac signs. The stars in Cancer are quite faint. You cannot see them from a bright city. The brightest star is called Beta Cancri. It is also known as Altarf.
This star is much bigger than our Sun. It is 50 times wider than the Sun.
Cancer also has many planets. One star system is called 55 Cancri. It has five planets. One of these planets might be like Earth. It sits in the habitable zone. This means it could have temperatures like our home.
In the middle of the crab is a cluster. We call this the Beehive Cluster. It is a group of many stars. It is very close to Earth. It is three times the size of the full Moon. People can see it easily with a telescope. Some people call it Praesepe. In old stories, it looked like a manger for donkeys.
Cancer is a medium-sized constellation in the northern sky. Its name comes from the Latin word for crab. It is one of the twelve signs of the zodiac. This group of stars covers 506 square degrees of the sky. That makes it the 31st largest constellation out of 88.
You can see it best at 9 p.m. during March. However, the stars are quite faint. Most people cannot see them from a bright city.
Many interesting things happen within this patch of sky. One star system is called 55 Cancri. It is about 40.9 light-years away from Earth. This system has five planets orbiting its main star. One of these is a super-Earth. Another planet sits in the habitable zone. This means its temperature might be similar to Earth.
Other stars in Cancer are also very large. The star Beta Cancri is an orange giant. It is 50 times wider than our Sun. It shines 660 times brighter than the Sun does.
People have studied these stars for a very long time. The German mapmaker Johann Bayer used Greek letters to label the stars. In 1922, the International Astronomical Union gave it the short name "Cnc." Later, in 1930, an astronomer named Eugène Delporte set its official boundaries.
He used a shape called a polygon to mark the edges. These lines help astronomers know exactly where the crab begins and ends.
Cancer holds some very famous objects for stargazers. In the center is the Beehive Cluster, also called Messier 44.
It is a large group of about 50 stars. It is one of the closest clusters to our Solar System. The cluster is three times the size of a full Moon. Galileo was one of the first people to see it. He used a telescope in 1609 to spot 40 stars there.
Many old stories explain why this constellation looks like a crab. In Greek myths, it was a crab that bit Hercules. The goddess Hera placed the crab in the stars.
Ancient people in other lands saw different things. In Babylon, it might have been a snapping turtle. The Egyptians saw it as a sacred symbol. Even today, we use the name Tropic of Cancer. This name comes from where the Sun sits in the sky during the summer solstice.
Cancer is a medium-sized constellation located in the Northern celestial hemisphere. Its name is the Latin word for crab, a creature it is commonly represented as in star charts. As one of the twelve constellations of the zodiac, it holds a significant place in astronomy. The constellation covers an area of 506 square degrees, which accounts for 0.921% of the entire sky. This size makes it the 31st largest of the 88 official constellations.
Because its stars are relatively faint, Cancer is often difficult to observe. In fact, under the bright lights of a city, the constellation is invisible to the naked eye. It is best viewed at 9 p.m. during the month of March.
The stars within Cancer vary greatly in brightness and type. The brightest star is Beta Cancri, also known as Altarf. It has an apparent magnitude of 3.5, meaning it is quite dim. This star is a binary system, consisting of an orange giant and a faint red dwarf companion. The orange giant is an aging star that has expanded to roughly 50 times the diameter of our Sun. It also shines with 660 times the luminosity, or brightness, of the Sun. Another notable star is Delta Cancri, or Asellus Australis, which is an orange-hued giant. It holds the record for the longest name in astronomy: "Arkushanangarushashutu," which comes from the ancient Babylonian language.
Beyond single stars, Cancer contains complex multiple star systems. Alpha Cancri, or Acubens, is a quadruple star system. This means it is made up of four stars working together. The primary part of the system consists of two white main sequence stars. The secondary part includes two smaller stars that are likely red dwarfs. Another example is Zeta Cancri, known as Tegmine, which also contains at least four stars. These stars form a binary pair with an orbital period of 1,100 years. Such systems show how gravity keeps multiple stars locked in long, predictable dances around one another.
One of the most exciting discoveries in Cancer involves the search for other worlds. The star system Rho1 Cancri, also called 55 Cancri, is located about 40.9 light-years from Earth. This system is a binary star consisting of a yellow dwarf and a red dwarf. Astronomers have found five planets orbiting the primary star. These include one super-Earth and four gas giants. One of these gas giants sits within the habitable zone. This is the region around a star where temperatures might allow for liquid water.
This makes 55 Cancri a very important target for scientists studying planetary systems.
For amateur astronomers, the most famous feature in Cancer is the Praesepe cluster. Also known as Messier 44 or the Beehive Cluster, it sits near the center of the constellation. It is an open cluster, which is a group of stars that formed from the same cloud of gas. Praesepe is about 590 light-years away and is one of the closest clusters to our Solar System. The cluster covers an area three times the size of the full Moon. It contains about 1,010 high-probability members, most of which are red dwarfs.
In 1609, Galileo Galilei used his telescope to observe the cluster, spotting 40 stars within it.
The history of Cancer is filled with ancient mythology and early scientific mapping. The Greek myth tells of a crab that bit the hero Heracles during his fight with the Hydra. The goddess Hera placed the crab in the sky to honor it. In ancient Babylon, the constellation was known as MUL.AL.LUL, which could mean a crab or a snapping turtle. In Egypt, around 2000 BC, it was seen as a sacred symbol of immortality. Astronomers like Claudius Ptolemy recorded the constellation in his work, the Almagest. Later, in 1922, the International Astronomical Union adopted the abbreviation "Cnc" for the constellation. In 1930, the Belgian astronomer Eugène Delporte defined its official boundaries using a polygon shape.
Cancer also connects to important mathematical and physical measurements in space. In 2002, scientists used a distant object called a quasar within this region to measure the speed of gravity. Another object, OJ 287, is a massive source located 3.5 billion light-years away. It contains a supermassive black hole with a mass of 18 billion solar masses. This is more than six times larger than the previous largest black hole known. Even the name "Tropic of Cancer" connects the constellation to the Earth's tilt. This name marks the northernmost latitude where the Sun can be directly overhead. While the Sun's position has shifted due to the precession of the equinoxes, the name remains a part of our geography.
Where will your curiosity go next?
🖼️ Images & Media (4)
More to explore
✨ What else?
Related topics you might enjoy
🔬 Go deeper
More advanced topics to explore
🪜 Step back
Simpler topics to build understanding
What is Nepedia?
A free, ad-free encyclopedia for children. Every article is written at five reading levels, so the same page works for a five-year-old and a fifteen-year-old — use the level switcher above to see this one change. No account needed to read.