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Merging quasars from the 'Cosmic Dawn' reveal how the universe was formed

Let us transport ourselves back in time to an era when the universe was a mere 900 million years old, a period known as the “Cosmic Dawn.”

Amidst this evolution of our universe, astronomers have made an extraordinary discovery: a pair of merging quasars, each powered by a supermassive black hole, locked in a gravitational dance of immense scale and energy.

This observation offers a rare glimpse into the dynamic processes that shaped the early universe and its structures.

Supermassive hearts of merging quasars

Before delving into this celestial phenomenon, it’s essential to understand the key players. Quasars are exceedingly luminous astronomical objects that often outshine entire galaxies.

This immense energy output is generated by a supermassive black hole residing at the core of the quasar.

These black holes, millions or even billions of times more massive than our Sun, exert a gravitational pull so powerful that it draws in surrounding matter.

Merging quasars from the 'Cosmic Dawn' reveal how the universe was formed. Credit: NOIRlab/NSF
Merging quasars from the ‘Cosmic Dawn’ reveal how the universe was formed. Credit: NOIRlab/NSF

As this matter spirals towards the black hole, it forms an accretion disk, a swirling vortex of gas and dust.

Within this disk, intense frictional and gravitational forces generate extreme temperatures, causing the matter to emit vast amounts of radiation across the electromagnetic spectrum.

This radiant energy is what makes quasars some of the brightest objects in the observable universe. The study of quasars provides valuable insights into the evolution of galaxies and the behavior of matter under extreme gravitational conditions.

Cosmic dawn

The early universe, a period known as the Cosmic Dawn, was a time of immense change. Roughly 50 million years after the Big Bang, the first stars and galaxies began to form, marking a pivotal shift from darkness to light.

This emergence of luminous objects initiated the Epoch of Reionization, a transformative phase in cosmic history.

During the Epoch of Reionization, the universe’s abundant neutral hydrogen gas was bombarded with intense ultraviolet radiation emitted by these nascent stars and galaxies.

This radiation had enough energy to strip electrons from the hydrogen atoms, a process known as ionization.

The ionization of hydrogen fundamentally altered the properties of the universe, making it transparent to certain wavelengths of light and paving the way for the formation of the complex structures, such as galaxies and galaxy clusters, that we observe in the universe today.

Merging quasars discovered

Enter Yoshiki Matsuoka, an astronomer at Ehime University in Japan, and his astute team. While meticulously examining images captured by the Hyper Suprime-Cam on the Subaru Telescope, they noticed a curious pair of red dots nestled closely together.

“The discovery was purely serendipitous,” Matsuoka remarked, unaware of the remarkable implications this chance observation held.

Subaru telescope captures two quasars merging in the early universe. Credit: NOIRLab/NSF
Subaru telescope captures two quasars merging in the early universe. Credit: NOIRLab/NSF

Upon closer inspection, these red dots were revealed to be quasars, each harboring a colossal black hole exceeding 100 million solar masses.

Astoundingly, these quasars were separated by a mere 10,000 light-years, a distance comparable to the width of our Milky Way galaxy.

This close proximity was no mere coincidence but a telltale sign of a cataclysmic merger in progress. The host galaxies of these quasars were locked in a gravitational embrace, their supermassive black holes spiraling towards an inevitable collision.

This merger will ultimately give birth to a single, even more monstrous black hole, forever altering the cosmic landscape.

Gaseous bridge

The Gemini Near-Infrared Spectrograph (GNIRS) on Gemini North played a crucial role in confirming the identity of these merging quasars and uncovering the secrets of their host galaxies.

“What we learned from the GNIRS observations was that the quasars are too faint to detect in near-infrared, even with one of the largest telescopes on the ground,” Matsuoka revealed.

This faintness indicated that a portion of the observed light originated not from the quasars themselves but from the intense star formation occurring within their merging galaxies.

Furthermore, the GNIRS observations detected a bridge of gas connecting the two quasars, providing compelling evidence of their impending merger.

Glimpse into the early universe

This monumental discovery offers a rare glimpse into a period of the universe that has long remained elusive.

By studying these distant objects, astronomers can unlock valuable insights into the processes that shaped the early universe and laid the foundation for the magnificent cosmic structures we marvel at today.

The discovery of this merging quasar pair marks a significant milestone in our understanding of the cosmos.

As astronomers venture deeper into the universe’s mysteries, they anticipate uncovering more of these enigmatic objects, gradually piecing together the intricate puzzle of the early universe’s evolution.

The highly anticipated Vera C. Rubin Observatory’s Legacy Survey of Space and Time (LSST) is poised to revolutionize quasar research.

With its unparalleled ability to peer into the depths of space, the LSST is expected to detect millions of quasars, ushering in a new era of discovery and unveiling the secrets of these cosmic powerhouses.


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