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Irregular galaxy facts for kids

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Irregular galaxy NGC 1427A (captured by the Hubble Space Telescope)
NGC 1427A, an example of an irregular galaxy about 52 million light years distant.
HubbleTuningFork
Tuning-fork style diagram of the Hubble sequence

An irregular galaxy is a galaxy that does not have a distinct regular shape, like a spiral or an elliptical galaxy.

Irregular galaxies do not fall into any of the regular types of the Hubble sequence. They do not have a bulge in the centre, nor any trace of spiral structure. They are quite common: they may make up a quarter of all galaxies. Most were once spiral or elliptical galaxies but were deformed by gravitational pull. Irregular galaxies also contain abundant amounts of gas and dust.

There are three sorts of irregular galaxies:

  1. An Irr-I galaxy (Irr I) is an irregular galaxy that features some structure but not enough to place it cleanly into the Hubble sequence. Some of the irregular galaxies are small spiral galaxies that are being distorted by the gravity of a larger neighbour.
  2. An Irr-II galaxy (Irr II) is an irregular galaxy that does not appear to feature any structure that can place it into the Hubble sequence.
  3. Dwarf irregulars, This type of galaxy may be important, as they often have a low level of metallicity and relatively high levels of gas. This is similar to the earliest galaxies in the Universe. They may be a local (and recent) version of the faint blue galaxies known to exist in deep field galaxy surveys.

The Magellanic Cloud galaxies were once classified as irregular galaxies, but have since been found to contain barred spiral structures.

Images for kids

  • A frenzy of stars IC 4710

    IC 4710 lies roughly 25 million light-years away in the southern constellation of Pavo.

  • Surveying the cosmos

    ESO 486-21 is a spiral galaxy with a somewhat irregular and ill-defined structure.

  • Spotlight on IC 3583

    Irregular galaxy IC 3583 has been found to have a bar of stars running through its center.

  • A lopsided lynx NGC 2337

    NGC 2337 is an irregular galaxy that resides 25 million light-years away in the constellation of Lynx.

  • A distinctly disorganised dwarf

    UGC 4459 is an irregular dwarf galaxy located approximately 11 million light-years away in the constellation of Ursa Major.

  • Meeting the neighbours

    Dwarf irregular galaxy known as PGC 18431.

  • A spattering of blue

    IC 559 is classified as a type Sm galaxy.

  • A cosmic optical illusion

    Irregular dwarf galaxy PGC 16389 covers its neighboring galaxy APMBGC 252+125-117.

See also

Kids robot.svg In Spanish: Galaxia irregular para niños

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Irregular galaxy Facts for Kids. Kiddle Encyclopedia.