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Sunburst Arc Doppelgangers Captured in Distant Regions of the Universe



  Sunburst Arc Galaxy

This image, taken with the NASA / ESA Hubble Space Telescope, shows a massive cluster of galaxies, about 4.6 billion light years away. Along its borders four bright arcs are visible; they are copies of the same distant galaxy, named Sunburst Arc.
The Sunburst Arc galaxy is almost 1

1 billion years old and light from it is being lent to many images through gravitational lensing. The Sunburst Arc is among the brightest known galaxies and its image can be seen 12 times over four arches.
Three arches can be seen in the top right of the image, the fourth arch in the lower left. The last one is partially obscured by a bright foreground star, located on the Milky Way. Credit: ESA / Hubble, NASA, Rivera-Thorsen et al.

Astronomers using the NASA / ESA Hubble Space Telescope observed a galaxy in distant regions of the Universe that appears to have doubled at least 12 times in the night sky. This unique vision, created by powerful gravitational lensing, helps astronomers gain a better understanding of the cosmic period known as the period of reionization.

This new image from the NASA / ESA Hubble Space Telescope shows an astronomical object whose image is multiplied by the impact of powerful gravitational lenses. The galaxy, called the Sunburst Arc, is about 11 billion light-years away from Earth and is lent to many images of a massive cluster of galaxies 4.6 billion light-years away [1].

The mass of the galaxy cluster was large enough to bend and enlarge the light from the farther galaxy behind it. This process leads not only to a deformation of light from the object, but also to an reproduction of the image of the expanse of space.

In the case of the Sunburst Arc the effect of the lens led to at least 12 galaxy images, distributed across four major arches. Three of these arches are visible at the top right of the image, while a counterarc can be seen on the lower left – partially hidden by a bright foreground star inside the Milky Way .

Hubble uses these cosmic glasses to study objects that are otherwise too weak and too small for even extremely sensitive instruments. The Sunburst Arc is no exception, despite being one of the brightest gravitationally lented galaxies known.

The lens produces different Sunburst Arc images between 10 and 30 times brighter. This allows Hubble to view structures as small as 520 light-years in total – a rare detailed observation for something far away. It compares reasonably well to the stars forming regions in galaxies in the local Universe, allowing astronomers to study the galaxy and its atmosphere more efficiently. in the history of the Universe: a period known as the period of reionization – a period that began only 150 million years after the Big Bang [2].

The period of reionization was a major period in the early Universe, one that culminated in the "dark ages", the period before the first stars were created when the Universe was dark and filled with neutral hydrogen [3] . Once the first stars were formed, they began to exhibit light, producing the high quality photons necessary to ionize the neutral hydrogen [4].

This converts intergalactic matter into an almost ionized form in which it exists today. However, in order to ionize intergalactic hydrogen, the high-energy radiation from these early stars had to escape their host galaxies without first being absorbed by the interstellar matter. So far only a small number of galaxies have been found to "leak" high-energy photons into deep space. How this light escaped from the first galaxies remains a mystery.

  Night Sky Surrounding Sunburst Arc

The wide-field field of the night sky shows the region where the Sunburst Arc is nicknamed. Credit: ESA / Digitized Sky Survey 2. Acknowledgment: Davide De Martin

The Sunburst Arc analysis helps astronomers to add another piece to the puzzle – apparently at least some photons can leave space through narrow channels in a gas rich neutral medium. This is the first observation of a long-term process [5]. While this process is unlikely to be the main mechanism that has led the Universe to be reionized, it may very well have provided a decisive push.

Notes

[1] The official designation of the Sunburst Arc galaxy is PSZ1 G311.65-18.48.

[2] The further we look at space, the further back we look at the time. It allows astronomers to study different times of the Universe, by studying objects at different distances.

[3] Ionization is the process of gaining or losing electrons in order to leave charges electrically. Time is known as reionization because, after the Big Bang, matter was formed first of protons and electrons. Then, during the reorganization – about 380 000 years after the Big Bang – neutral hydrogen formed from these particles in the first place.

[4] While an ionised hydrogen atom consists only of the core of an atom (a proton) a neutral hydrogen atom contains a nucleus of a proton orbited by an electron .

[5] The paper describing these observations will appear in Science on November 8, 2019.


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