Deep space objects > Star clusters

Star clusters are a group of stars with a common origin and a gravitational link for a specific time. It is a useful tool for astronomers as it helps study and model stellar evolution. There are two main types of star clusters: open clusters (open) and globular clusters. Learn more about the galaxy’s star clusters in an interesting video.

Types of star clusters

Open star clusters

Open star clusters

Open star clusters are so named because individual stars can be resolved easily. For example, the Pleiades and Hyades are so close that individual stars can be easily seen with the naked eye. They are sometimes called galactic clusters because they are located in dusty spiral arms. Stars in an open cluster have a common origin (the same initial molecular cloud was formed). Usually, the cluster contains several hundred stars (can reach several thousand).

The stars are bound by gravity, but it’s pretty weak. The cluster revolves around the galaxy and finally dissipates due to gravitational contact with stronger objects. It is believed that the Sun appeared in an open cluster, which no longer exists. Therefore, these are always young objects. A nebula is still visible in the Pleiades, hinting at recent formation.

The open clusters are filled with Population I stars — young and highly metallic. In width, cover from 2 to 20 parsecs.

Messier open star clusters

Butterfly Cluster - Messier 6

M6

Ptolemy's Cluster - Messier 7

M7

Wild Duck Cluster - Messier 11

M11

Open Cluster - Messier 18

M18

Messier 21

M21

Open Cluster - Messier 23

M23

M25 - Open Cluster

M25

M26 - Open Cluster

M26

M29 - Open Cluster

M29

M34 - Open Cluster

M34

M35 - Open Cluster

M35

Open Cluster - Messier 36

M36

Open Cluster - Messier 37

M37

Open Cluster - Messier 38

M38

Open Cluster - Messier 39

M39

Open Cluster - Messier 41

M41

Manger Star Cluster - Messier 44

M44

Star Cluster Pleiades - Messier 45

M45

Open Cluster - Messier 46

M46

Open Cluster - Messier 47

M47

Open Cluster - Messier 48

M48

Open Cluster - Messier 50

M50

Open Cluster - Messier 52

M52

Open Cluster - Messier 67

M67

Open Cluster - Messier 93

M93

Open Cluster - Messier 103

M103

Other notable open star clusters

Perseus Double Cluster

The Perseus Cluster

Cluster of Hyades

Hyades star cluster

Star Cluster Jewelry Box

Jewelry box

Star Cluster Christmas Tree

Christmas tree

Snowflake Cluster

Snowflakes


Globular star clusters

Globular star clusters

Globular clusters of galaxies contain from a couple of thousand to a million stars located in a spherical gravitational system. They are in a halo and represent the most ancient stars – population II (developed, but low metallicity). The clusters are so old that any star (above the G or F class) has already stepped over the main sequence. The globular cluster has little dust and gas because new stars do not form there. The density in the interior is much higher than in areas near the Sun.

In globular clusters, stars also share a common origin. But this type holds objects firmly by gravity (stars do not scatter). There are approximately 200 globular clusters in the Milky Way. Among them, you can recall 47 Toucan, M4 and Omega Centauri. Although about the latter, there are suggestions that it may be a dwarf spheroidal galaxy.

Messier globular star clusters

M2 - Globular Cluster

M2

M3 - Globular Cluster

M3

M4 - Globular Cluster

М4

M5 - Globular Cluster

M5

Globular Cluster - Messier 9

M9

Globular Cluster - Messier 10

M10

Globular Cluster - Messier 12

M12

Hercules Cluster - Messier 13

M13

Globular Cluster - Messier 14

M14

Pegasus Cluster - Messier 15

M15

Globular Cluster - Messier 19

M19

Globular Cluster - Messier 22

M22

M28 - Globular cluster

M28

M30 - Globular cluster

M30

Globular Cluster - Messier 53

M53

Globular Cluster - Messier 54

M54

Globular Cluster - Messier 55

M55

Globular Cluster - Messier 56

M56

Globular Cluster - Messier 62

M62

Globular Cluster - Messier 68

M68

Globular Cluster - Messier 69

M69

Globular Cluster - Messier 70

M70

Globular Cluster - Messier 71

M71

Globular Cluster - Messier 72

M72

Globular Cluster - Messier 75

M75

Globular Cluster - Messier 79

M79

Globular Cluster - Messier 80

M80

Globular Cluster - Messier 92

M92

Messier 107 Cluster (M107)

M107

Other notable globular star clusters

Omega Centauri

Omega Centauri

Age of star clusters

Star clusters are incredibly valuable to astronomers because they can help determine the age of a star and track its evolution.

The stars of open clusters have a common origin, so their metallicity levels converge, which means that all members will pass through the evolutionary stages in the same way. In addition, they are located at the same distance, which also allows you to display the absolute value. If you see bright stars that stand out, then they are much lighter than their weaker neighbors.

With this information, scientists create digital charts for the clusters. They display the apparent value of V on the vertical axis relative to the digital index B – V horizontally. With spectrographic parallax, you can calibrate the chart to display the absolute value.

If we build diagrams for them, we get the bottom graph. Since they are at different distances, it is calibrated to absolute values.

A new scale is visible on the right vertical axis. “Years” is the age of the cluster. The pair in Perseus is so young that most of the stars are in the main sequence stage. The Pleiades are slightly older and do not have stars exceeding color index 0 (spectral type A0). More massive objects have already stepped over to the giant branches. M67 does not have a star hotter than a color index of 0.4. Most significant is the pivot point in the diagram, where the cluster turns off the main sequence. The lower the main sequence, the older the cluster.

Globulars are usually much older than open ones, so the color magnitude in the diagram shows more developed stars. They are also devoid of objects with a large mass. This point is illustrated below for example M55.

There is a cluster of hot stars in the main sequence above the shutdown point. They are called blue stragglers. Scientists believe that due to the high stellar densities in globular clusters, some are capable of merging. The combined mass makes the star hotter and brighter than the main mass. Star clusters are not eternal structures and they are destroyed. Examine this process in the video. Also, use the online star map to find the clusters yourself. If you can’t buy a telescope, then visit our page with a virtual model of the Milky Way galaxy or view a photo from the list of clusters.

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