It is one of the universe’s living fossils.
The two main types of galaxies found in the known universe are spiral and elliptical. Our Milky Way is a lovely example of a spiral galaxy. But there are also some stranger-looking galaxies out there, including ones known as tadpoles. As you would expect, tadpole galaxies look like immature frogs, with bright, compact heads and elongated tails.
The recently discovered tadpole galaxy, LEDA 36252 or Kiso 5639, is one such example. Using the NASA/ESA Hubble Space Telescope and the Wide Field Camera 3 (WFC3), astronomers were able to capture a detailed image of the unusually shaped galaxy.
Tadpole galaxies are rare in the local universe. In a sample of 10,000 galaxies, only 20 would be tadpoles. In fact, only 500 galaxies have ever been classified as tadpoles.
However, they are more common in the early universe — in other words, much further away from us. Nevertheless, the image of LEDA 36252 is important because it can provide astronomers with a better understanding of the evolutionary processes that occur in these unusual galaxies, such as accretion of cosmic gas, starburst activity, and the formation of globular star clusters.
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"I think [LEDA 36252] is a beautiful, up-close example of what must have been common long ago. The current thinking is that galaxies in the early universe grow from accreting gas from the surrounding neighborhood. It's a stage that galaxies, including our Milky Way, must go through as they are growing up," Debra Elmegreen of Vassar College, lead researcher on the project that recorded the image, told Tech Times.
According to ESA, generally, the stars in tadpole galaxies are very old. In fact, they are described as living fossils from the early universe. Although LEDA 36252 is, for the most part, no exception to the rule, it does contain some interesting and surprising features.
LEDA’s head contains a mass of young stars equivalent to roughly 10,000 suns. These stars are grouped into large clusters, which stretch 2,700 light-years, and consist mainly of hydrogen and helium. Astronomers believe that this unexpected new star formation was the result of the tadpole galaxy accreting primordial gas — gas created moments after the Big Bang that contains very little heavy elements — from its surroundings.
What’s more, according to the observations, there are signs of strong stellar winds and supernova explosions, seen as holes in LEDA 36252’s head.
Within the galaxy’s elongated tail, there are at least four distinct star-forming regions, but according to the astronomers, they seem to be older than the one in the head.
Interestingly, there is a galaxy named the Tadpole Galaxy, which was previously imaged by Hubble. This galaxy was named for its elongated appearance; however, it is actually a spiral galaxy, not a tadpole.
The paper describing LEDA 36252 was published in The Astrophysical Journal.
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