New research of oldest light confirms age of the universe

Credit: © Andrea Danti / stock.adobe.com

Just how old is the universe? Astrophysicists have been debating this question for decades. In recent years, new scientific measurements have suggested the universe may be hundreds of millions of years younger than its previously estimated age of approximately 13.8 billions of years.

Now new research published in a series of papers by an international team of astrophysicists, including Neelima Sehgal, PhD, from Stony Brook University, suggest the universe is about 13.8 billion years old. By using observations from the Atacama Cosmology Telescope (ACT) in Chile, their findings match the measurements of the Planck satellite data of the same ancient light.

The ACT research team is an international collaboration of scientists from 41 institutions in seven countries. The Stony Brook team from the Department of Physics and Astronomy in the College of Arts and Sciences, led by Professor Sehgal, plays an essential role in analyzing the cosmic microwave background (CMB) -- the afterglow light from the Big Bang.

"In Stony Brook-led work we are restoring the 'baby photo' of the universe to its original condition, eliminating the wear and tear of time and space that distorted the image," explains Professor Sehgal, a co-author on the papers. "Only by seeing this sharper baby photo or image of the universe, can we more fully understand how our universe was born."

Obtaining the best image of the infant universe, explains Professor Sehgal, helps scientists better understand the origins of the universe, how we got to where we are on Earth, the galaxies, where we are going, how the universe may end, and when that ending may occur.

The ACT team estimates the age of the universe by measuring its oldest light. Other scientific groups take measurements of galaxies to make universe age estimates.

The new ACT estimate on the age of the universe matches the one provided by the standard model of the universe and measurements of the same light made by the Planck satellite. This adds a fresh twist to an ongoing debate in the astrophysics community, says Simone Aiola, first author of one of the new papers on the findings posted to arXiv.org.

"Now we've come up with an answer where Planck and ACT agree," says Aiola, a researcher at the Flatiron Institute's Center for Computational Astrophysics in New York City. "It speaks to the fact that these difficult measurements are reliable."

In 2019, a research team measuring the movements of galaxies calculated that the universe is hundreds of millions of years younger than the Planck team predicted. That discrepancy suggested that a new model for the universe might be needed and sparked concerns that one of the sets of measurements might be incorrect.

The age of the universe also reveals how fast the cosmos is expanding, a number quantified by the Hubble constant. The ACT measurements suggest a Hubble constant of 67.6 kilometers per second per megaparsec. That means an object 1 megaparsec (around 3.26 million light-years) from Earth is moving away from us at 67.6 kilometers per second due to the expansion of the universe. This result agrees almost exactly with the previous estimate of 67.4 kilometers per second per megaparsec by the Planck satellite team, but it's slower than the 74 kilometers per second per megaparsec inferred from the measurements of galaxies.

"I didn't have a particular preference for any specific value -- it was going to be interesting one way or another," says Steve Choi of Cornell University, first author of another paper posted to arXiv.org. "We find an expansion rate that is right on the estimate by the Planck satellite team. This gives us more confidence in measurements of the universe's oldest light."

As ACT continues making observations, astronomers will have an even clearer picture of the CMB and a more exact idea of how long ago the cosmos began. The ACT team will also scour those observations for signs of physics that doesn't fit the standard cosmological model. Such strange physics could resolve the disagreement between the predictions of the age and expansion rate of the universe arising from the measurements of the CMB and the motions of galaxies.

The ACT research is funded by the National Science Foundation (NSF), and the NSF also funds the work of Professor Sehgal and colleagues at Stony Brook.

Breakthrough in deciphering the birth of supermassive black holes

“On the left, a color composite image of the Hubble space telescope in the center of” Mirachs Ghost “. On the right, the new ALMA image of this same region, revealing the distribution of the cold and dense gas which swirls around this center of this object in exquisite detail. »Credit: Cardiff University

A research team led by scientists from Cardiff University says it is closer to understanding how a supermassive black hole (SMBH) was born thanks to a new technique that allowed them to zoom in on one of these. enigmatic cosmic objects with unprecedented detail.

Scientists do not know if SMBH formed in extreme conditions soon after the big bang, in a process called effondrement direct '', ou ont été cultivées beaucoup plus tard à partir de trous noirs seed ”resulting from the death of massive stars.

If the first method were true, SMBH would be born with extremely large masses – hundreds of thousands to millions of times more massive than our Sun – and would have a fixed minimum size.

If the latter were true, the SMBH would start relatively small, about 100 times the mass of our Sun, and would begin to grow over time by feeding on the stars and the gas clouds that live around them.

Astronomers have long strived to find the lowest mass SMBHs, which are the missing links needed to decipher this problem.

In a study released today, the Cardiff-led team pushed the boundaries, revealing one of the lowest mass SMBHs ever observed in the center of a nearby galaxy, weighing less than a million times the mass from our sun.

The SMBH lives in a galaxy known as “Mirach’s Ghost”, due to its proximity to a very bright star called Mirach, which gives it a ghostly shadow.

The results were obtained using a new technique with the Atacama Large Millimeter / submillimeter Array (ALMA) network, an advanced telescope located at the top of the Chajnantor plateau in the Chilean Andes which is used to study the light of some of the coldest objects in the Universe.

“The SMBH in Mirach’s Ghost appears to have mass in the range predicted by” direct collapse “models,” said Dr. Tim Davis of the School of Physics and Astronomy at Cardiff University.

“We know it is currently active and swallowing gas, so some of the more extreme” direct collapse “models that only do very massive SMBHs cannot be true.

“That alone is not enough to tell the difference between the ‘seed’ image and ‘direct collapse’ – we have to understand the statistics for that – but it is a giant step in the right direction. ”

Black holes are objects that have collapsed under the weight of gravity, leaving behind small but incredibly dense regions of space from which nothing can escape, not even light.

A SMBH is the largest type of black hole which can represent hundreds of thousands, even billions of times the mass of the Sun.

It is believed that almost all large galaxies, like our own Milky Way galaxy, contain an SMBH located at its center.

“SMBHs have also been found in very distant galaxies as they appeared a few hundred million years after the big bang,” said Dr. Marc Sarzi, a member of Dr. Davis’ team at the Armagh Observatory & Planetarium.

“This suggests that at least some SMBHs could have become very massive in a very short time, which is difficult to explain according to the models of formation and evolution of galaxies. ”

“All black holes develop when they swallow clouds of gas and disturb stars that venture too close to them, but some have a more active life than others. ”

“Searching for the smallest SMBHs in nearby galaxies could therefore help us reveal how SMBHs start,” said Dr. Sarzi.

In their study, the international team used new techniques to zoom further than ever before into the heart of a small neighboring galaxy, called NGC404, allowing them to observe the swirling clouds of gas that surrounded the SMBH in its center.

The ALMA telescope allowed the team to resolve gas clouds in the heart of the galaxy, revealing details just 1.5 light years in diameter, making it one of the gas maps to the Highest resolution ever in another galaxy.

Being able to observe this galaxy with such high resolution allowed the team to overcome a decade of conflicting results and reveal the true nature of SMBH in the center of the galaxy.

“Our study shows that with this new technique, we can really begin to explore both the properties and the origins of these mysterious objects,” continued Dr. Davis.

“If there is a minimum mass for a supermassive black hole, we have not yet found it. ”

The results of the study were published today in the Royal Astronomical Society Monthly Notices.