Milky-Way Now Has a Twin
Scientists said in reports published last month that millions of light-years from Earth, a new galaxy that is incredibly similar to our own is hidden, surprisingly stable, and unpredictable. Scientists have said the discovery has changed the way galaxies shape their understanding.
Scientists from the Inter-University Centre for Astronomy and Astrophysics (IUCAA), Pune have discovered one of the earliest galaxies in the universe, situated about 9.3 billion light-years away from the Earth. The breakthrough discovery, published on Monday, was made using AstroSat—the first multi-wavelength satellite of India.
Launched by the Indian Space Research Organisation (ISRO) on September 28, 2015, and developed by multiple research institutes from India and Canada, the satellite specialises in studying celestial sources in X-ray, optical and UV spectral bands simultaneously. It consists of five payloads that assist in capturing UV light coming from celestial objects.
The satellite, using its unique features, recently detected an extreme-ultraviolet light coming from the galaxy named AUDFs01. The discovery is expected to help our understanding of the earliest source of light in the universe. According to a study published in the journal Nature, the galaxy, called SPT0418-47, is located 12 billion light-years away from earth. Astronomers at the Max Planck Institute for Astrophysics (MPI) used the Atacama Large Millimeter / Submillimeter Array (ALMA), one of the world’s most powerful telescopes, to find a young galaxy.
Even the most powerful telescopes fail to capture accurate observations.
The new galaxy was found in the area of space called the Hubble eXtreme Deep Field by the wide-field UltraViolet Imaging Telescope (UVIT) of AstroSat. It is a small area based in the constellation Fornax, which was created using the data collected by the Hubble space telescope in 2003 and 2004. This part contains thousands of galaxies.
The research team observed and examined the UV light and its source for more than 28 hours in October 2016. However, it reportedly took nearly two years for the researchers to confirm that the emission was originating from an early galaxy.
The UV radiation coming from distant celestial objects is hard to record from Earth, as most of it is absorbed by the planet’s atmosphere. Therefore, scientists have to use telescopes in space to make such discoveries.
As per reports, NASA’s Hubble Space Telescope (HST), which is larger than the UVIT, was unable to detect UV emission from this galaxy as the signals were too faint. AstroSat managed to identify it successfully since the background noise in the UVIT detector is comparatively lower than the HST.
Since the galaxy is so far away, it is regarded by astronomers as it was when the universe was just 1.4 billion years old. They said that SPT0418-47 is “highly unchaotic”—contradictory to existing ideas that all young galaxies are” turbulent and unstable “as opposed to more mature galaxies like the Milky Way.
SPT0418-47 does not appear to possess spiral arms like the Milky Way. But both SPT0418-47 and our galaxy have spinning disks and bulges around their poles-huge clusters of closely packed stars.
Researchers used a new computer modeling technology to recreate the actual shape of the galaxy and the motion of its gas from ALMA data.
It is the first time scientists have detected a bulge so early in the universe ‘s history, the release said — making SPT0418-47 the “Milky Way look-alike” more distant.
“The big surprise was to find that this galaxy is very close to nearby galaxies, contrary to all model predictions and previous, less detailed observations,” said co-author Filippo Fraternali of the Netherlands Astronomical Institute of Kapteyn, University of Groningen.
Study of a baby galaxy that helps astronomers to see the universe only as it was just 10 percent of its current age is critical to understanding how galaxies are forming and developing. It’s unclear how a well-ordered galaxy could have evolved so long after the Big Bang, which suggests that the early universe might be less chaotic than it once was assumed.
While they have some similarities, astronomers expect SPT0418-47 to evolve into a galaxy that is distinctly alien to the Milky Way. They expect that it will ultimately become part of the elliptical galaxy class.
In the future, astronomers expect to determine how widespread and chaotic these baby disk galaxies are to further our knowledge of our own galaxy‘s evolution.
Scientists believe that shortly after the big bang, the universe reached its highest temperature and gradually began to cool. During this time, it consisted mostly of subatomic particles like protons, neutrons, and photons. With time, these neutrons and protons combined to form deuteron and helium, which attracted electrons and finally fused to form neutral hydrogen.
Theoretically, at this very point, through the help of these ancient elements, the first light formed and was allowed to flow freely in all directions in space. However, there were no stars, galaxies or any other celestial objects for more than 200 million years after the Big Bang.
Cosmic Dark Age refers to a brief time when the universe was completely dark, and it eventually came to an end when the first generation of stars again started to form. This further resulted in the splitting of atoms in protons and electrons that led to the reionisation of the universe. However, what processed resulted in this reionisation remains a mystery. And now, UVIT detecting the extreme-UV emission offers an unexpected hope towards solving this mystery.
The photons emitted through such reionisation sources in the early universe are obstructed by light-blocking dust or carbon, or intergalactic medium. Therefore, with the current level of knowledge and technology, it is impossible to observe such radiation from the Earth.
Fortunately, some radiation does reach our space telescopes and this has been studied through this research. As per reports, this is the first time a galaxy has been observed in the extreme ultraviolet light and will further help to shed light on the conditions of the early universe.
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