Lenticular Galaxy: Definition, Facts, Difference

Lenticular galaxies are a unique type of galaxy classified as S0 in the Hubble system. They exhibit properties of both spiral and elliptical galaxies, possessing a central bulge like ellipticals and a disk like spirals but lacking spiral arms. Lenticular galaxies consist mainly of aging stars with little ongoing star formation. They retain some dust and gas in their disks and have a halo of interstellar matter surrounding them. Lenticular galaxies serve as a bridge between spiral and elliptical galaxies in classification systems.

Lenticular galaxies make up 10% of all observed galaxies but account for up to 60% of the population within galaxy clusters. They have high bulge-to-disk ratios, exceeding 4:1. Lenticular galaxies are known to cannibalize other galaxies, incorporating their mass and stars. Some display features like stellar rings or shells, remnants of past galactic mergers. Many lenticular galaxies were once spiral galaxies stripped of gas and dust through interactions with other galaxies.

They lack spiral arms and have older stellar populations with little ongoing star formation. Lenticular galaxies contain less gas compared to spiral galaxies. They have increased total mass and mass-to-light ratios, reflected in increased velocity dispersions. Lenticular galaxies are characterized by a large central bulge surrounded by a featureless disk with surface brightness, measuring 20-22 mag/arcsec^2.

Lenticular galaxies possess a bulge, rotating disk, and in some cases, a nucleus or bar. They have a bulge-to-disk ratio and a halo of stars and dark matter. Lenticular galaxies lack interstellar material and have stellar populations billions of years in age. Their shape resembles a lens with a convex profile, appearing flat when viewed from the side. Lenticular galaxies range in size from 10,000 to 100,000 light-years in diameter.

Examples of lenticular galaxies include NGC 4479, NGC 2787, and NGC 3115 (Spindle Galaxy). NGC 4479 is located in the Virgo constellation, 55 million light-years from Earth, with a diameter of 30,000 light-years. NGC 2787 is a barred lenticular galaxy in Ursa Major, 25 million light-years away, with a 20,000 light-year diameter. NGC 3115 resides in Sextans, 32 million light-years from Earth, spanning 50,000 light-years and housing a supermassive black hole of 2 billion solar masses.

What is a lenticular galaxy?

Lenticular galaxy is a type of galaxy exhibiting properties of both spiral and elliptical galaxies, classified as S0 in the Hubble system.Astronomers consider lenticular galaxies early-type galaxies with little ongoing star formation, consisting mainly of aging stars. Lenticular galaxies have a halo of interstellar matter surrounding them and retain amounts of dust and gas in their disks. Galaxy clusters contain lenticular galaxies, which are found in the universe and serve as a bridge between spiral and elliptical galaxies in classification systems.

Lenticular galaxies have a morphology that sets them apart from other galaxy types. Lenticular galaxies possess a central bulge and a flat disk of stars, similar to spiral galaxies. Lenticular galaxies lack prominent spiral arms and contain little interstellar gas and dust, resembling elliptical galaxies in these aspects.

Lenticular galaxy formation occurs through the merger of two galaxies or depletion of gas and dust in spiral galaxies. Galaxy mergers trigger the formation of a disk structure while stripping away spiral arms due to gravitational interactions. Lenticular galaxies have a disk shape with a central bulge and feature a prominent central bar. The disk of a lenticular galaxy appears smooth without spiral structure, giving it a lens shape when viewed edge-on. The disk contains stars, while the bulge contains a mix of old and young stars.

Lenticular galaxies range in size from dwarf galaxies to giant galaxies. Lenticular galaxy sizes span from thousands to hundreds of thousands of light-years in diameter. Lenticular galaxies have masses ranging from billions to hundreds of billions of solar masses.

What are fun facts about lenticular galaxies?

Lenticular galaxies are hybrids, blending features of ellipticals and spirals. These galaxies possess a central bulge and flattened disk, composed of old stars. Lenticular galaxies lack spiral arms but have a gas and dust halo. Galaxy mergers form these intermediate celestial bodies, stripping away gas and limiting star formation.

Fun facts about lenticular galaxies are listed below:

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• Composition of lenticular galaxies: They contain mostly old stars, with little gas and dust for new star formation, often exhibiting bar-shaped structures across their central regions.
• High bulge-to-disk ratios: Lenticular galaxies possess large bulge-to-disk ratios, often exceeding 4:1, setting them apart from other galaxy types.
• Rarity in the universe: Lenticular galaxies make up only 10% of all observed galaxies.
• Dominance in galaxy clusters: Lenticular galaxies account for up to 60% of the population within galaxy clusters.
• Galactic cannibalism: Lenticular galaxies are known to cannibalize smaller galaxies, incorporating their mass and stars.
• Distinctive features from mergers: Some lenticular galaxies display features like stellar rings or shells, which are remnants of past galactic mergers.
• Hubble classification position: Lenticular galaxies sit at the intersection of spiral and elliptical sequences in the Hubble classification scheme.
• Discovery of lenticular galaxies: Lenticular galaxies were first identified by Edwin Hubble in the 1920s. Hubble recognized lenticular galaxies as a distinct class intermediate between spiral and elliptical galaxies.
• Transformation history: Many lenticular galaxies were once spiral galaxies that were stripped of their gas and dust through interactions with other galaxies.

How does a lenticular galaxy differ from a spiral galaxy?

Lenticular galaxies differ from spiral galaxies. Lenticular galaxies possess a central bulge and disk but lack spiral arms. Lenticular galaxies have older stellar populations and complex structures. Spiral galaxies feature sweeping arms of stars, gas, and dust. Lenticular galaxies are called “armless spirals” due to their featureless disks.

The age of  stellar populations within lenticular galaxies differs from those in spiral galaxies. Lenticular galaxies have older stellar populations. Color-magnitude diagrams reveal a population of older, redder stars in lenticular galaxies, whereas spiral galaxies contain a mix of old and young stars.

Lenticular galaxies lack ongoing star formation. The slow rate of star formation activity is attributed to the absence of interstellar gas and dust, which are essential for creating stars.

Lenticular galaxies lack interstellar gas compared to spiral galaxies. Spiral galaxies contain quantities of hydrogen and helium gas, fueling continuous star formation. The absence of gas in lenticular galaxies results from factors including gas stripping, past star formation, and supernova explosions.

Lenticular galaxies are characterized by a central bulge and a disk structure. The central bulge is surrounded by a featureless disk with high surface brightness, measuring 20-22 mag/arcsec^2.

Lenticular galaxies have higher total mass and mass-to-light ratios compared to spiral galaxies. The increased mass is reflected in higher velocity dispersions, indicating greater random motion among stars within the galaxy.

What are the characteristics of a lenticular galaxy?

Lenticular galaxies possess characteristics of both spiral and elliptical galaxies. Central bulges resemble ellipticals, while disks mirror spirals. Lenticular galaxies lack spiral arms and contain mainly aging, red stars. Little ongoing star formation occurs in lenticular galaxies. Dust disks remain detectable in infrared. Diameters of lenticular galaxies range from 10,000 to 100,000 light-years. Dark matter provides gravitational scaffolding for structure formation.

The characteristics of a lenticular galaxy are outlined below:

• Lenticular galaxy central bulge: A densely packed region of older stars, spherical in shape.
• Lenticular galaxy rotating disk: Lacks spiral arms and surrounds the central bulge.
• Lenticular galaxy bulge-to-disk ratio: Exhibits a high ratio, with a large bulge compared to the disk.
• Lenticular galaxy central nucleus: Some have a packed region of stars at the center.
• Lenticular galaxy halo: A diffuse spherical region of stars and dark matter surrounding certain galaxies.
• Lenticular galaxy bars: Elongated regions of stars running through the center of some galaxies.
• Lenticular galaxy interstellar material: Lacks significant material, resulting in little ongoing star formation.
• Lenticular galaxy stellar populations: Composed of stars billions of years old.
• Lenticular galaxy appearance: Flat when viewed from the side due to their disk component.
• Lenticular galaxy shape: Resembles a lens with a convex profile.
• Lenticular galaxy morphology: Occupies an intermediate position between spiral and elliptical galaxies.

What is the shape of a lenticular galaxy?

Lenticular galaxies have a lens-like shape. Central bulges contain packed older stars. Disks surround bulges, housing a mix of older and younger stars. S0 galaxies lack spiral arms, distinguishing them from spiral galaxies. SB0 galaxies feature bar-like structures in central bulges.

The shape of lenticular galaxies combines features of both spiral and elliptical galaxies, resulting in a hybrid appearance. Lenticular galaxies look like half-spiral, half-elliptical galaxies when observed from angles. Some lenticular galaxies possess ill-defined arms or a rounded shape, contributing to their appearance.

Lenticular galaxies appear as a line with a bright central bulge when viewed edge-on. The edge-on view reveals an elliptical shape with a major axis 2-3 times longer than the minor axis. NGC 4111, a lenticular galaxy, has a major axis of 5.5 arcminutes and a minor axis of 2.5 arcminutes. Lenticular galaxies have an axis ratio of about 0.45 and an ellipticity of 0.25, as exemplified by NGC 4111.

The median diameter of lenticular galaxies is 30,000 light-years. Lenticular galaxies have a mass between 10^9 to 10^11 solar masses, contributing to their shape and structure.

What are lenticular galaxy examples?

Lenticular galaxies include Cartwheel Galaxy (ESO 350-40), NGC 4479, NGC 2787, NGC 5866, and NGC 3115. M84 (NGC 4374), NGC 5308, NGC 4111, and IC 4479 are examples. Cartwheel Galaxy lies 500 million light-years away in Sculptor constellation. NGC 4479 is situated 55 million light-years in Virgo constellation. Lenticular galaxies represent 20% of all galaxies.

Examples of lenticular galaxies are provided in the table below.

NGC 4479 is an example of a lenticular galaxy. NGC 4479 is situated in the constellation Virgo, 55 million light-years from Earth. Astronomers classify NGC 4479 as a type S0 galaxy with a diameter of around 30,000 light-years. NGC 2787 represents a barred lenticular galaxy. NGC 2787 is found in the constellation Ursa Major, 25 million light-years away. NGC 2787 has a diameter of 20,000 light-years and is classified as a type SB0 galaxy.

NGC 3115, known as the Spindle Galaxy, is one of the nearest lenticular galaxies to Earth. NGC 3115 is located in the constellation Sextans, 32 million light-years away. NGC 3115 has a diameter of around 50,000 light-years and houses a supermassive black hole with a mass of 2 billion solar masses. M84, cataloged as NGC 4374, is another prominent lenticular galaxy. M84 resides in the constellation Virgo, 60 million light-years from Earth. M84 has a diameter of around 100,000 light-years and contains over 1,700 observed globular clusters.