The newest photo from the NASA/ESA Hubble Space Telescope is of a rare type of galaxy, known as a ‘tadpole.’
Kiso 5639 is a member of a class of galaxies called ‘tadpoles’ because of their bright heads and elongated tails. New Hubble/WFC3 observations comprising this image cover a wide portion of the spectrum, including ultraviolet, optical, H-alpha, and infrared emission. Together, they paint a beautifully detailed picture of Kiso 5639. Image credit: NASA / ESA / D. Elmegreen, Vassar College / B. Elmegreen, IBM’s Thomas J. Watson Research Center / J. Almeida, C. Munoz-Tunon, & M. Filho, Instituto de Astrofisica de Canarias / J. Mendez-Abreu, University of St. Andrews / J. Gallagher, University of Wisconsin-Madison / M. Rafelski, NASA Goddard Space Flight Center / D. Ceverino, Center for Astronomy at Heidelberg University.
The Universe is a swirling pool of galaxies moving through the emptiness of space. Whilst spirals and ellipticals are the two main galaxy types in the Universe, there are also other, odder types.
The subject of the new Hubble image is Kiso 5639, an unusual dwarf galaxy located 82 million light-years away.
Otherwise known as KUG 1138+327 and LEDA 36252, this galaxy is an example of what is known as a tadpole galaxy because of their bright, compact heads and elongated tails.
Tadpole galaxies are rare in the local Universe but more common in the distant cosmos, suggesting that many galaxies pass through a phase like this as they evolve.
Hubble observations of Kiso 5639 have uncovered the stellar content and bright pink glow of hydrogen at one end of the galaxy.
A burst of new stars in a region measuring about 2,700 light-years across makes the hydrogen clouds glow.
The mass of these young stars equals about one million suns. The stars are grouped into several dozen clusters that formed less than one million years ago.
Other star formation is taking place throughout the galaxy but on a much smaller scale. Star clusters in the rest of Kiso 5639 are between several million to a few billion years old.
Vassar College astronomer Debra Elmegreen and co-authors used Hubble’s Wide Field Planetary Camera 3 (WFC3) to conduct a detailed imaging study of this galaxy.
“I think Kiso 5639 is a beautiful, up-close example of what must have been common long ago,” Dr. Elmegreen said.
“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.”
Hubble’s crisp resolution helped the astronomers analyze the giant star-forming clumps in Kiso 5639 and determine the masses and ages of the star clusters.
“There is much more star formation going on in the head than what you would expect in such a tiny galaxy,” said co-author Dr. Bruce Elmegreen, from IBM’s Thomas J. Watson Research Center.
“And we think the star formation is triggered by the ongoing accretion of metal-poor gas onto a part of an otherwise quiescent dwarf galaxy.”
Hubble also revealed giant holes peppered throughout the star-forming head of Kiso 5639.
These cavities give the galaxy’s head a Swiss-cheese appearance because numerous supernova detonations – like firework aerial bursts – have carved out holes of rarified superheated gas.
The team’s results have been accepted for publication in the Astrophysical Journal (arXiv.org preprint).
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Debra Meloy Elmegreen et al. 2016. Hubble Space Telescope Observations of Accretion-Induced Star Formation in the Tadpole Galaxy Kiso 5639. ApJ, accepted for publication; arXiv: 1605.02822
