He arranged the different groups of galaxies in what became known as the Hubble sequence.

In 1936 Hubble produced a classification system for galaxies that is used to this day, the Hubble sequence.

A slightly more extensive description of galaxy types based on their appearance is given by the Hubble sequence.

Since the Hubble sequence is entirely based upon visual morphological type, it may miss certain important characteristics of galaxies such as star formation rate ( in starburst galaxies ) and activity in the core ( in active galaxies ).

A time sequence of Hubble Space Telescope images, taken in the 15 years from 1994 to 2009, showing the collision of the expanding supernova remnant with a ring of dense material ejected by the progenitor star 20, 000 years before the supernova.

While the LMC is often considered an irregular type galaxy ( the NASA Extragalactic Database lists the Hubble sequence type as Irr / SB ( s ) m ), the LMC contains a very prominent bar in its center, suggesting that it may have previously been a barred spiral galaxy.

The Hubble sequence is a morphological classification scheme for galaxies invented by Edwin Hubble in 1926.

Tuning-fork style diagram of the Hubble sequence

To this day, the Hubble sequence is the most commonly used system for classifying galaxies, both in professional astronomical research and in amateur astronomy.

The Pinwheel Galaxy ( Messier 101 / NGC 5457 ): a spiral galaxy classified as type Scd on the Hubble sequence

On the right of the Hubble sequence diagram are two parallel branches encompassing the spiral galaxies.

Although strictly part of the de Vaucouleurs system of classification, the Sd class is often included in the Hubble sequence.

Later observations ( by Hubble himself, among others ) showed Hubble's belief to be correct and the S0 class was included in the definitive exposition of the Hubble sequence by Allan Sandage.

Galaxies that do not fit into the Hubble sequence, because they have no regular structure ( either disk-like or ellipsoidal ), are termed irregular galaxies.

In his extension to the Hubble sequence, de Vaucouleurs called the Irr I galaxies ' Magellanic irregulars ', after the Magellanic Clouds-two satellites of the Milky Way which Hubble classified as Irr I.

In the extended Hubble sequence, the Magellanic irregulars are usually placed at the end of the spiral branch of the Hubble tuning fork.

This nomenclature is the source of the common, but erroneous, belief that the Hubble sequence was intended to reflect a supposed evolutionary sequence, from elliptical galaxies through lenticulars to either barred or regular spirals.

Nevertheless, the Hubble sequence is still commonly used in the field of extragalactic astronomy and Hubble types are known to correlate with many physically relevant properties of galaxies, such as luminosities, colours, masses ( of stars and gas ) and star formation rates.

The two stars in the black field of the mission patch indicate the flight's numerical designation in the Space Transportation System's mission sequence.

The three large orange triangular points of the mission patch indicate the flight's numerical designation in the Space Transportation System's mission sequence.

The path of the red, white, and blue streak on the mission patch indicates the flight's numerical designation in the Space Transportation System's mission sequence.

The five points of the blue star of the mission patch indicate the flight's numerical designation in the Space Transportation System's mission sequence.

The six white stars in the upper blue field of the mission patch indicate the flight's numerical designation in the Space Transportation System's mission sequence.

The seven white stars in the black field of the mission patch, as well as the arm extending from the shuttle in the shape of a 7, indicate the flight's numerical designation in the Space Transportation System's mission sequence.

An iconic example is found at the end of the " Dawn of Man " sequence in the film 2001: A Space Odyssey.

The film's title is a play on the 1977 Bond film The Spy Who Loved Me and contains plot elements from James Bond films, Diamonds Are Forever ( Laser Gun Plot and Cloning ), You Only Live Twice ( Secret Volcano Base ), Moonraker ( Outer Space Ventures ), The Man with the Golden Gun ( Mini Me based on character Nick Nack ) and On Her Majesty's Secret Service ( opening sequence in which Vanessa Kensington dies ).

In 2004, American science fiction screenwriter Ronald D. Moore stated the style of the first season's opening credits of Space: 1999 inspired the opening credit sequence for his acclaimed remake of Battlestar Galactica.

The animators also used their own voices for all the characters instead of hiring voice actors in order to keep costs down, although it does feature one professional voice actor, Michael Rye, as the narrator in the attract sequence ( he is also the narrator for Space Ace and Dragon's Lair II ).

The phrase would be incorporated into the opening credits sequence in following episodes, as part of the famous " Space: The Final Frontier ..." speech given by Captain Kirk.

It was notably spoofed during the Medieval Times sequence in the Jim Carrey movie The Cable Guy, in The Simpsons episode Deep Space Homer, and on Futurama as the national anthem of Dr. Zoidberg's home panet, Decapod 10.

The three stars on the left and two stars on the right of STS-32's insignia symbolized the flight's numerical designation in the Space Transportation System's mission sequence.

The thirteen complete stars in the blue field of the U. S. flag of the mission insignia symbolize the flight's numerical designation in the Space Transportation System's mission sequence ( the 17 stars in the black field were indicative of the flight's original designation as STS-17 ).

* Detailed dissection of the title sequence for Space: 1999

The 12 stars within the blue field indicate the flight's original numerical designation as STS-12 in the Space Transportation System's mission sequence.

The thirty-six stars on the insignia symbolize the flight's numerical designation in the Space Transportation System's mission sequence ; the stars also form part of a stylized American flag, forming the background to an image of a bald eagle, the American national bird.

The three stars on the top and seven stars on the bottom of the insignia symbolize the flight's numerical designation in the Space Transportation System's mission sequence.

The four stars on the top-left and three stars on the top-right of the insignia symbolize the flight's numerical designation in the Space Transportation System's mission sequence.

The four stars in the lower blue field and two stars in the upper blue field of the insignia symbolize the flight's numerical designation in the Space Transportation System's mission sequence.

The five stars and three stripes of the insignia symbolize the flight's numerical designation in the Space Transportation System's mission sequence.

The five stars and shape of the robotic arm of the insignia symbolize the flight's numerical designation in the Space Transportation System's mission sequence.

The five stars on the left and nine stars on the right of the insignia symbolize the flight's numerical designation in the Space Transportation System's mission sequence.