Hubble captures rare "tadpole" galaxy during a dramatic bout of star creation

This image of Kiso 5639 was captured using Hubble's Wide Field Camera 3 – it is believed that the galaxy encountered the primordial gas filament some time in the last 1 million years(Credit: NASA, ESA, D. Elmegreen (Vassar College))

The Hubble Space Telescope has captured a maelstrom of star creation taking place in a nearby "tadpole" galaxy known as Kiso 5639. The activity was unexpected, as the galaxy is thought to be passing through a desert-like region of space devoid of the vital materials needed for the creation of new stars.

The discovery of a specimen such as Kiso 5639 a mere 82 million light-years away amongst the largely spiral and elliptical galaxies that make up the Milky Way's neighbours is a rare find indeed. Described as "tadpole galaxies" due to their bright heads and extended tails, this family of galaxies is thought to have been much more common in the early universe, and appear often in Hubble's Ultra-Deep Field images.

Out of a sample of 10,000 galaxies in the local universe, there is expected to be a mere 20 tadpoles in our little corner of the universe. Due to the relative lack of primordial gas in the region, the galaxy has suffered a stunted evolution, with the majority its the stars dating back to the time at which the galaxy first formed.

However, upon analysis of the Hubble data, astronomers discovered a flurry of star formation taking place in the head of the tadpole. Several dozen youthful star clusters were detected within the 2,700 light-year wide expanse, all of which were estimated to be less than 1 million years old. This makes them mere babies compared to clusters permeating the rest of the galaxy, many of which are billions of years old.

The clusters that house the younger generation of stars are thought to be far larger than their geriatric counterparts. It is estimated that the newly created stellar bodies boast a cumulative mass the equivilent to 10,000 Suns. Researchers attribute the unexpected bout of star formation to an influx of interstellar material, which is being drawn into the galaxy as it passes through a rare filament of primordial gas punctuating the otherwise barren expanse.

By using special filters to split the light down into its component wavelengths, astronomers noted a distinct lack of heavy elements in the gas that makes up the head region of Kiso 5639. This is due to the fact that the gas has yet to be subjected to the dramatic lifecycle of stars, which will see the material transformed into heavier elements in the hearts of the new generation of stars through stellar fusion, and subsequently distributed through violent supernova explosions.

Whilst star birth is illuminating the head of the galaxy, the dramatic deaths of a number of older cosmic giants are also leaving their mark. The new release reveals that the head of Kiso 5639 is riddled with holes, created as the forces released by cataclysmic supernovae explosions from the last generation of stars carve out vast cavities in the surrounding clouds of dust and gas.

In the same way that the Milky Way rotates as it lumbers through space, Kiso 5639 is also constantly on the move. The spinning motion is likely to bring more of the tadpole galaxy into contact with the material filament, which will lead to star formation spreading beyond the head to other regions of the galaxy.

Source: NASA

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