August 14, 2016

The Kiso 5639 Galaxy

Kiso 5639 Galaxy

In this NASA Hubble Space Telescope image, a firestorm of star birth is lighting up one end of the diminutive galaxy Kiso 5639. The dwarf galaxy is shaped like a flattened pancake, but because it is tilted edge-on, it resembles a skyrocket, with a brilliant blazing head and a long, star-studded tail.

Kiso 5639 is a member of a class of galaxies called "tadpoles" because of their bright heads and elongated tails. This galaxy resides relatively nearby, at 82 million light-years away. Tadpoles 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 2,700 light-years across makes the hydrogen clouds glow. The mass of these young stars equals about 1 million suns. The stars are grouped into large clusters that formed less than 1 million years ago.

Stars consist mainly of hydrogen and helium, but cook up other "heavier" elements, such as oxygen and carbon. When the stars die, they release their heavy elements and enrich the surrounding gas. In Kiso 5639, the bright gas in the galaxy's head is more deficient in heavy elements than the rest of the galaxy. Astronomers, therefore, think that this new star-formation event was triggered when the galaxy accreted primordial gas from its surroundings, since intergalactic space contains more pristine, hydrogen-rich gas.

The elongated tail, seen stretching away from the galaxy's head and scattered with bright blue stars, contains at least four distinct star-forming regions. These stars appear to be older than those in the star-forming head.

Hubble also revealed giant holes peppered throughout the starburst end. These cavities give this area a Swiss-cheese appearance because numerous supernova detonations — like firework aerial bursts — have carved out holes of rarified superheated gas. Wispy filaments, comprising gas and some stars, extend away from the main body of the cosmic tadpole.

The observations were taken in February 2015 and July 2015 with Hubble's Wide Field Camera 3.

Image Credit: NASA, ESA
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