Andromeda

Andromeda is a constellation (a specific area or region in the sky that includes a distinct pattern of stars). It's one of the 88 constellations you can see from Earth. Andromeda can be seen from the Northern Hemisphere from June until February, so astronomers call it an autumn constellation. Fall is the season when Andromeda is easiest to spot in the night sky in Massachusetts.

What is a Constellation?

Astronomers used to classify constellations as a group of stars, but now a days constellations are thought of as specific areas in the sky. The distinct pattern of stars that the Greek astronomer Ptolemy first defined 2,000 years ago and all of the surrounding stars, galaxies, and other celestial objects that aren't part of the pattern but are in the same area are now considered part of the constellation. Every constellation includes a group of well-known, bright stars that form a distinct pattern. Recognizing a constellation's pattern helps people find the constellation and correctly identify the stars within it.

What Does Andromeda's Star Pattern Look Like?

The 4 brightest and easiest to spot stars in the Andromeda constellation pattern are: Almaak, Mirach, Alpheratz, and Adhil. These stars are named after letters in the Greek alphabet. Astronomers used letters in the Greek alphabet to name and rank stars based on how bright the stars were in comparison to one another.

When lines are drawn to connect them, the stars in the Andromeda constellation form this shape:

The shape is supposed to be princess Andromeda, who is chained to the sky.

What Stars and Other Celestial Bodies Make Up Andromeda?

The constellation Andromeda is one of the largest of the 88 constellations that are visible from Earth. In addition to the 4 stars that make up the shape of Andromeda, the constellation also includes a really bright star called Upsilon Andromedae (nicknamed UpsAnd), which is similar to the sun. The UpsAnd star is so bright that it prevents us from seeing a bunch of newly discovered distant planets that are outside of our galaxy.

This is a picture that was taken with a telescope camera of the UpsAnd Star. It's so bright that you can't see the newly discovered planets close to it.

Just as the planets in our solar system orbit the sun, scientists think that these newly discovered distant planets might be orbiting the UpsAnd star. When telescopes become more powerful, we might be able to learn more about these far away planets in the Andromeda constellation.

A Detailed View of the Andromeda Constellation (the star UpsAnd is labeled)

The Andromeda constellation also includes the famous Andromeda Galaxy, a spiral galaxy that is about 2.5 million light years away from Earth. You can learn more about Andromeda Galaxy by reading this page.

This is a picture of the Andromeda Galaxy that was taken with two special space telescope cameras: ESA's Herschel space telescope and the XMM-Newton’s X-ray telescope. The red coloring shows rings of dust where new stars are forming and the blue X-ray image shows stars approaching the ends of their lives.

Why is the Constellation named Andromeda?

Nearly 2,000 years ago, Ptolemy, a famous astronomer and mathematician living in a city in Egypt called Alexandria, created a list of 48 constellations. Each constellation included a pattern of stars he saw in the night sky. Most of the constellations were named after characters from Greek mythology. Ptolemy's list of constellations included the constellation Andromeda.

During Ptolemy's lifetime, the Greeks wrote and told fictional stories called myths. Myths were part of ancient Greek's culture and religion. They wrote myths about their gods and heroes. Greek teachers used myths to teach students lessons about right versus wrong and explain the world around them. Because Greek mythology was such a big part of daily life for Greeks in Ptolemy's time and because the existence of the stars was attributed to the Greek gods, many constellations, including Andromeda, were named after characters from popular Greek myths. Ptolemy named the constellation Andromeda after the famous mythical princess Andromeda. He also named one constellation next to Andromeda Cassiopeia, because in Greek Mythology, Cassiopeia was princess Andromeda's mother. He named another constellation that neighbors Andromeda Perseus, because in the Greek myth, Perseus is the hero who saves Andromeda from being eaten by a sea monster.

The Myth of Andromeda

In Greek mythology, Andromeda was a beautiful princess. Her mother, the queen of Ethiopia, was named Cassiopeia. Queen Cassiopeia bragged to the sea nymphs (very pretty spirit women who live in and control the sea) that Andromeda was prettier than they were. The sea nymphs became very angry at Cassiopeia, so they went to Poseidon (the king and god of the sea) and asked him to punish Cassiopeia for being so rude. Poseidon punished Cassiopeia by sending a sea monster named Cetus to attack the country of Ethiopia, where Queen Cassiopeia and Princess Andromeda lived.

To save Ethiopia from being destroyed by the sea monster Cetus, Andromeda's dad chained his daughter to a rock by the sea and offered her as a sacrifice to Cetus the sea monster. A hero named Perseus saved Andromeda from being eaten by turning Cetus the sea monster into stone before he could eat the princess.

There's another constellation named after the hero Perseus that's right next to the constellation Andromeda.

Old drawings of the Andromeda Constellation show a woman with chains on her wrists, because the part of the Greek myth that is most famous is the part where Andromeda's dad chains her to a rock and offers her as a sacrifice to the sea monster Cetus.

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