The Hyades is the closest open star cluster to Earth and one of the easiest star clusters to see with the naked eye. Located in the constellation Taurus, its brightest visible stars form a broad V-shaped pattern that outlines the face of the Bull.
Although the bright orange star Aldebaran appears to be part of this pattern, it is actually a foreground star and does not belong to the cluster. The Hyades itself contains hundreds of stars that formed together from the same cloud of gas and dust and have traveled through the Milky Way as a group for hundreds of millions of years.
Here are some of the most interesting facts about the Hyades, including what its stars are like, why Aldebaran is not one of them, and how to find the cluster in the night sky.
Quick Hyades Facts
- Object type: Open star cluster
- Constellation: Taurus
- Distance: About 150 light-years
- Age: About 625 million years
- Apparent magnitude: 0.5
- Size: About 15 light-years across
- Coordinates: RA 04h 27m, Dec +15° 52′
- Other names: Melotte 25, Collinder 50, Caldwell 41
The Hyades Contains Hundreds of Stars
The Hyades contains hundreds of known stars, although only a small fraction are bright enough to see with the naked eye. Among its most prominent members are four orange giant stars — Gamma Tauri, Delta¹ Tauri, Epsilon Tauri and Theta¹ Tauri — which stand out within the cluster’s familiar V-shaped pattern.
These stars have exhausted the hydrogen in their cores and expanded into giants after leaving the main sequence. Epsilon Tauri, also known as Ain, is particularly interesting because it hosts a giant planet, making it one of the best-known examples of a planet orbiting an evolved star in an open cluster.
The Hyades also contains many fainter main-sequence stars, including numerous low-mass red dwarfs, as well as white dwarfs left behind by more massive stars that evolved more quickly. This mixture of stars at different evolutionary stages reflects the cluster’s considerable age.
The Hyades Is About 625 Million Years Old
At about 625 million years old, the Hyades is a relatively mature open cluster. Its stars formed at roughly the same time, but their different masses mean they have evolved at different rates. The most massive original members have already left the main sequence, while lower-mass stars can continue shining for billions or even trillions of years.
The cluster itself will not remain together forever. Gravitational encounters between its stars and the influence of the Milky Way are gradually pulling members away, creating long tidal tails of former Hyades stars extending far beyond the familiar V-shaped cluster. Eventually, the Hyades will disperse completely and its remaining stars will continue orbiting the galaxy independently.
Aldebaran Is Not Actually Part of the Hyades
The bright orange star Aldebaran appears to sit among the Hyades and marks the eye of Taurus, but it is not actually a member of the cluster. This is simply a line-of-sight effect: Aldebaran lies about 65 light-years from Earth, less than half the distance of the Hyades, and only appears in front of the cluster from our viewpoint.
This chance alignment makes the Hyades especially distinctive in the night sky. Aldebaran provides an excellent visual signpost for finding the broad V-shaped group of Hyades stars surrounding it. Despite appearing to belong to the cluster, Aldebaran is actually a foreground star and, like the Hyades, lies within the constellation Taurus.
How to Find the Hyades in the Night Sky
The Hyades is easy to find because its brightest stars form the distinctive V-shaped face of Taurus. From the Northern Hemisphere, first locate Orion and follow the line of Orion’s Belt northwest until you reach the bright orange star Aldebaran. The loose group of stars surrounding it is the Hyades.
As the finder chart below shows, the larger outline of Taurus extends away from the Hyades to form the Bull’s long horns. These stars are part of the constellation pattern, not the Hyades cluster itself. The Hyades is the much smaller V-shaped group centered around the apparent position of Aldebaran.
When and How to See the Hyades
For Northern Hemisphere observers, the Hyades is best seen during autumn and winter, when Taurus is prominent in the evening sky. By January, the cluster is already well placed after nightfall and remains visible during the evening into early spring.
No equipment is needed to enjoy the Hyades. Its brighter members are readily visible to the naked eye under reasonably dark skies, while binoculars reveal many more stars without losing the cluster’s broad overall shape. A telescope is generally less suitable for viewing the Hyades as a whole because its relatively narrow field of view shows only a small part of this unusually large cluster at one time.
The Hyades and Pleiades Are Similar in Size but Look Very Different
The Hyades and Pleiades are both open star clusters in Taurus, but they look strikingly different in the night sky. The Hyades forms a broad V-shaped pattern, while the Pleiades appears as a much smaller and more tightly packed group of stars.
Much of this difference is simply a matter of perspective. Despite their very different appearance, the Hyades and Pleiades are both roughly 15 light-years across. The Pleiades, however, is nearly three times farther from Earth, so it appears as a small, compact group while the much closer Hyades seems to spread widely across the sky.
The two clusters are also at very different stages of their lives. The Hyades is about 625 million years old, while the Pleiades is only around 100 million years old. Some of the Hyades’ more massive stars have therefore already evolved into giants or ended their lives as white dwarfs, while the brightest Pleiades members are still hot, blue-white stars.
Despite appearing relatively close together in our sky, the Hyades and Pleiades are completely separate star clusters that formed independently of one another.
The Hyades Has Been Known Since Ancient Times
The Hyades has been recognized since ancient times, and its prominent place in Taurus inspired stories in several early cultures. In Greek mythology, the Hyades were daughters of Atlas and half-sisters of the Pleiades. One tradition says they were placed among the stars after mourning the death of their brother Hyas, who had been killed while hunting.
The Hyades also became strongly associated with rain and stormy weather. Their name has traditionally been linked with rain, while Greek and Roman writers referred to their seasonal appearance when describing wet or unsettled weather. This association was reinforced by the cluster’s appearance in the evening sky during the wetter part of the Mediterranean year.
Long before astronomers understood the Hyades as a physical family of stars, its distinctive V-shaped pattern therefore served both as a recognizable celestial landmark and as a seasonal marker.