Discovery of Massive Early Galaxies Defies Prior Understanding of the Universe

2023-02-23

Six massive galaxies discovered in the early universe are upending what scientists previously understood about the origins of galaxies in the universe.

“These objects are way more massive​ than anyone expected,” said Joel Leja, assistant professor of astronomy and astrophysics at Penn State, who modeled light from these galaxies. “We expected only to find tiny, young, baby galaxies at this point in time, but we’ve discovered galaxies as mature as our own in what was previously understood to be the dawn of the universe.”

Using the first dataset released from NASA’s James Webb Space Telescope, the international team of scientists discovered objects as mature as the Milky Way when the universe was only 3% of its current age, about 500-700 million years after the Big Bang. The telescope is equipped with infrared-sensing instruments capable of detecting light that was emitted by the most ancient stars and galaxies. Essentially, the telescope allows scientists to see back in time roughly 13.5 billion years, near the beginning of the universe as we know it, Leja explained.

“This is our first glimpse back this far, so it’s important that we keep an open mind about what we are seeing,” Leja said. “While the data indicates they are likely galaxies, I think there is a real possibility that a few of these objects turn out to be obscured supermassive black holes. Regardless, the amount of mass we discovered means that the known mass in stars at this period of our universe is up to 100 times greater than we had previously thought. Even if we cut the sample in half, this is still an astounding change.

In a paper published today (Feb. 22) in Nature, the researchers show evidence that the six galaxies are far more massive than anyone expected and call into question what scientists previously understood about galaxy formation at the very beginning of the universe.

“The revelation that massive galaxy formation began extremely early in the history of the universe upends what many of us had thought was settled science,” said Leja. “We’ve been informally calling these objects ‘universe breakers’ — and they have been living up to their name so far.”

Leja explained that the galaxies the team discovered are so massive that they are in tension with 99% of models for cosmology. Accounting for such a high amount of mass would require either altering the models for cosmology or revising the scientific understanding of galaxy formation in the early universe — that galaxies started as small clouds of stars and dust that gradually grew larger over time. Either scenario requires a fundamental shift in our understanding of how the universe came to be, he added.

“We looked into the very early universe for the first time and had no idea what we were going to find,” Leja said. “It turns out we found something so unexpected it actually creates problems for science. It calls the whole picture of early galaxy formation into question.”

On July 12, NASA released the first full-color images and spectroscopic data from the James Webb Space Telescope. The largest infrared telescope in space, Webb was designed to see the genesis of the cosmos, its high resolution allowing it to view objects too old, distant or faint for the Hubble Space Telescope.

“When we got the data, everyone just started diving in and these massive things popped out really fast,” Leja said. “We started doing the modeling and tried to figure out what they were, because they were so big and bright. My first thought was we had made a mistake and we would just find it and move on with our lives. But we have yet to find that mistake, despite a lot of trying.”

Leja explained that one way to confirm the team’s findings and alleviate any remaining concerns would be to take a spectrum image of the massive galaxies. That would provide the team data on the true distances, and also the gasses and other elements that made up the galaxies. The team could then use the data to model a clearer picture of what the galaxies looked like, and how massive they truly were.

“A spectrum will immediately tell us whether or not these things are real,” Leja said. “It will show us how big they are, how far away they are. What’s funny is we have all these things we hope to learn from James Webb and this was nowhere near the top of the list. We’ve found something we never thought to ask the universe — and it happened way faster than I thought, but here we are.”

The other co-authors on the paper are Elijah Mathews and Bingjie Wang of Penn State, Ivo Labbe of the Swinburne University of Technology, Pieter van Dokkum of Yale University, Erica Nelson of the University of Colorado, Rachel Bezanson of the University of Pittsburgh, Katherine A. Suess of the University of California and Stanford University, Gabriel Brammer of the University of Copenhagen, Katherine Whitaker of the University of Massachusetts and the University of Copenhagen, and Mauro Stefanon of the Universitat de Valencia.

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Junyu Zhang selected as Eberly College of Science’s Fall 2022 Student Marshal

2022-12-14

Junyu Zhang of Chongqing, China, will be honored as the student marshal for the Eberly College of Science during Penn State’s fall commencement ceremonies on Saturday, Dec. 17, on the University Park campus.

Zhang will graduate with a 4.0 grade point average and bachelor’s degrees in astronomy, physics, and mathematics. He is a Schreyer Scholar in the Schreyer Honors College and has been a member of the Dean’s List every semester. Zhang has been honored with several awards and scholarships, including the John and Elizabeth Holmes Teas Scholarship from 2021 to 2022, the Bert Elsbach Honors Scholarship from 2020 to 2021, the Evan Pugh Scholar Senior Award in 2021, and the President’s Freshman Award in 2020.

“It is my great honor to be selected as student marshal for the Eberly College of Science,” he said. “I could not have achieved such a huge accomplishment without the support of my family, my mentors, my professors, and my friends. Therefore, I would like to share this honor with them.”

While at Penn State, Zhang conducted research with both Joel Leja, assistant professor of astronomy and astrophysics, and Niel Brandt, Verne M. Willaman Professor of Astronomy & Astrophysics and professor of physics. In his work with Leja, Zhang used a computer code called Prospector to investigate various wavelengths of light that are emitted by galaxies in order to identify markers that might distinguish galaxies that normally form stars from “rejuvenating galaxies” that fully quench—stop producing stars—and then become star-forming once more. Because rejuvenating galaxies are rare in the universe, these studies may help astronomers better understand the conditions under which stars and galaxies form. With Brandt, Zhang used data from X-ray surveys to identify active galactic nuclei found at the centers of some galaxies that have high redshift—the light they give off is skewed toward the red end of the spectrum due to their distance from Earth—and to better understand how they affect their host galaxies.

“The most important lesson that I will take with me from my time at Penn State is to follow your heart,” Zhang said. “One of the bravest decisions I ever made was to transfer to Penn State and change my major. Although I lost almost all three years I spent at my original university, I am now able to study what I love and achieve such an accomplishment like becoming a student marshal.”

After graduation, Zhang plans to continue his research in astronomy by pursuing a graduate degree.

Zhang is a graduate of Chongqing Nankai Secondary School in Chongqing, China. His parents are Li Mu and Kedi Zhang.

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Rare Cosmic Explosion Blasts Hole in Established Science

2022-12-08

On Dec. 11, 2021, the NASA’s Neil Gehrels Swift Observatory, which has its Mission Operations Center at Penn State, detected a blast of high-energy light from a galaxy roughly 1 billion light-years away. The event, which was simultaneously detected by Fermi Gamma-ray Space Telescope, brings into question what was thought to be settled science concerning gamma-ray bursts (GRBs), the most energetic explosions in the universe.

“It was something we had never seen before,” said Simone Dichiara, assistant research professor of astronomy and astrophysics at Penn State and member of the Swift team. “We knew it wasn’t associated with a supernova, the death of a massive star, because it was too close. It was a completely different kind of optical signal, one that we associate with a kilonova, the explosion triggered by colliding neutron stars.”

The Swift team was able to rapidly identify the explosion’s location, in the constellation Boötes, enabling other facilities to quickly respond with follow-up observations. Their observations have provided the earliest look yet at the first stages of a kilonova, according to a NASA release. Their findings were published today (Dec. 7) in the journal Nature.

Gamma-ray bursts come in two varieties: long and short. Scientists previously understood long GRBs, which last a couple of seconds to one minute, as forming when a super massive star explodes as a supernova. Short GRBs, which last less than two seconds, were previously thought to only occur when two compact objects — like two neutron stars or a neutron star and a black hole — collide to form a kilonova.

The revelation that a kilonova could trigger a long gamma-ray burst rewrites the decades-long paradigm of cosmic explosions: that long GRBs are strictly the signature of the death of massive stars, Dichiara explained. The discovery means not all long GRBs are made by supernovae, some are produced by the merger of neutron stars.

“This event was a game-changer that showed to us how our well-established knowledge of the universe was in fact only a partial and incomplete view,” said Eleonora Troja, an astronomer at the University of Rome Tor Vergata and lead author on the paper. “This result was hard to digest at first and we spent months trying to figure out alternative explanations, but in the end this is the only one that works well. Although we have been studying GRBs for decades, it is awesome to see how the universe can surprise us in the most unexpected ways.”

The work was supported by the European Research Council through the Consolidator grant BHianca and by the National Science Foundation.

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Tracing the Origins of Rare Cosmic Explosions

2022-11-30

The galactic homes of 84 short gamma-ray bursts (sGRBs)—produced by the collision of two neutron stars—have now been pinpointed in what is the most extensive inventory to date. A team that includes astronomers from Penn State used information from several highly sensitive instruments at the W.M. Keck Observatory, Las Campanas Observatory, MMT Observatory, and Gemini Observatory, combined with some of the most sophisticated galaxy modeling ever used in the field to identify the sources of these sGRBs.

“At most, astronomers might detect about a dozen short gamma-ray bursts each year, and so far only one has a confirmed origin from a neutron star merger,” said Joel Leja, assistant professor of astronomy and astrophysics at Penn State and a member of the research team. “Their mysterious origins have led us to take a lateral approach by instead trying to understand the environments where these objects thrive. The resulting catalog greatly expands our knowledge of where sGRBs come from and will help astronomers determine their true origins.” 

SGRBs are momentary flashes of intense gamma-ray light emitted when two neutron stars collide. As an homage to the fact that sGRBs are among the brightest explosions in the universe, the team calls their catalog BRIGHT (Broadband Repository for Investigating Gamma-ray burst Host Traits) with all of their data and modeling products online for community use.

“This is the largest catalog of sGRB host galaxies to ever exist, so we expect it to be the gold standard for many years to come,” said Anya Nugent, an astronomy graduate student at Northwestern University who led the research, observational efforts with Keck and the MMT observatories, and one of the two publications on the study. 

While the gamma-rays from sGRBs last only seconds, the optical light that is also produced in the event can continue for hours before fading below detection thresholds, called an afterglow. SGRB afterglows were first discovered in 2005 by NASA’s Neil Gehrels Swift Observatory, whose mission operations center is located at Penn State. Since then, astronomers have spent the last 17 years trying to find out which galaxies these powerful bursts originated from, as the stars within a galaxy can give insight into the environmental conditions needed to produce these events and can connect them to their neutron star merger origins. The only sGRB with a confirmed neutron star merger origin, GRB 170817A, was detected just seconds after gravitational wave detectors observed the binary neutron star merger, GW170817.

“One way to better understand gamma ray bursts is to understand the types of ‘cosmic ecosystems’ which they tend to live in, meaning the gas and stars in the environment around them—their host galaxies,” said Leja. “We modeled the galaxies where these gamma-ray burst happened, including information about how many stars are in the galaxy, how it formed, how many heavy elements are there, and how much dust obscures our view of the galaxy. This allowed us to understand how galaxies where gamma-ray bursts explode are different than other galaxies.”

Learning about sGRB host galaxies is crucial to understanding the blasts themselves and offers clues about the types of stars that created them as well as their distance from Earth. Since neutron star mergers create heavy elements like gold and platinum, the data will also deepen scientists’ understanding of when precious metals were first created in the universe.

“Building this catalog and finally having enough host galaxies to see patterns and draw significant conclusions is exactly what the field needed to push our understanding of these fantastic events and what happens to stars after they die,” said Nugent.

“In a decade, the next generation of gravitational wave observatories will be able to detect neutron star mergers out to the same distances as we do sGRBs today. Thus, our catalog will serve as a benchmark for comparison to future detections of neutron star mergers,” added Wen-fai Fong, assistant professor of astronomy and physics at Northwestern University and lead author of one of the publications.

The first paper in the study

, published in The Astrophysical Journal, found that sGRBs occur at earlier times in the universe and at greater distances from their host galaxy’s centers than previously thought. Surprisingly, several of these explosions were found just outside their host galaxies as if they were “kicked out,” raising questions as to how they were able to travel that far.

Published in the same journal, the second research paper

in the study probed the characteristics of 69 of the identified sGRB host galaxies. The findings suggest about 85 percent of them are young, actively star-forming galaxies — a stark contrast to earlier studies that characterized the population of sGRB host galaxies as relatively old and approaching death. This means neutron star systems may form in a broad range of environments and many of them have quick formation-to-merger timescales.

Many questions remain about how neutron stars merge and how long the process takes. But observing sGRBs and their host galaxies provides one of the best perspectives to answer them and can offer more data about neutron star mergers and their hosts at much farther distances, and more frequently, than current gravitational wave detectors. This new sGRB host catalog will therefore serve as a vital reference point in the coming decade to understand the full evolution of these systems over cosmic time. 

The James Webb Space Telescope (JWST) is poised to further advance our understanding of neutron star mergers and how far back in time they began, as it will be able to detect the faintest host galaxies that exist at very early times in the universe.

“This field is so young— there is so much more to learn,” said Leja. “We hope that we can learn even more about the cosmic environment of sGRBs with near-future observatories, and in this way better understand what precipitates these mysterious explosions.”

In addition to Leja, the research team at Penn State also includes Derek Fox, associate professor of astronomy and astrophysics.

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Bright light from early universe 'opens new chapter in astronomy'

2022-11-30

UNIVERSITY PARK, Pa. — An unexpectedly rich array of early galaxies that was largely hidden until now has been observed by researchers using data from NASA’s James Webb Space Telescope.

The researchers found two exceptionally bright galaxies that existed approximately 350 and 450 million years after the big bang. Their extreme brightness is puzzling to astronomers and challenges existing models of galaxy formation.

“These objects are remarkable because they are far brighter than we would expect from our models of how galaxies form,” said Joel Leja, assistant professor of astronomy and astrophysics at Penn State, who developed the code used to analyze light from the distant galaxies.

As a postdoctoral fellow at the Harvard-Smithsonian Center for Astrophysics, Leja developed code capable of making sense of infrared data from distant galaxies, such as those imaged by Webb, proving that they are in fact our first glimpses of the very early universe.

“The code combines models of all the things that live in galaxies and interprets the light we observe from them,” said Leja. “This includes things like stars of various ages and elemental compositions, cosmic dust that blocks the light we see from stars, emission from gaseous nebulae, and so on.”

Two research papers, one led by Marco Castellano of the National Institute for Astrophysics in Rome, Italy, and another by Rohan Naidu of the Harvard-Smithsonian Center for Astrophysics and the Massachusetts Institute of Technology with Leja as co-author, have been published in the Astrophysical Journal Letters. The two papers describe the bright celestial objects, which both teams discovered separately in quick succession just days after Webb officially started science operations.

“With Webb, we were amazed to find the most distant starlight that anyone had ever seen, just days after Webb released its first data,” Naidu said in a NASA news release.

With just four days of analysis, the researchers found two exceptionally bright galaxies. They determined the young galaxies transformed gas into stars extremely rapidly, meaning the onset of stellar birth may have started just 100 million years after the big bang, roughly 13.8 billion years ago. The researchers also determined the two galaxies existed approximately 450 and 350 million years after the big bang, though future spectroscopic measurements with Webb will help confirm their findings.

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Bright Light from Early Universe 'Opens New Chapter in Astronomy'

2022-11-21

UNIVERSITY PARK, Pa. — An unexpectedly rich array of early galaxies that was largely hidden until now has been observed by researchers using data from NASA’s James Webb Space Telescope.

The researchers found two exceptionally bright galaxies that existed approximately 350 and 450 million years after the big bang. Their extreme brightness is puzzling to astronomers and challenges existing models of galaxy formation.

“These objects are remarkable because they are far brighter than we would expect from our models of how galaxies form,” said Joel Leja, assistant professor of astronomy and astrophysics at Penn State, who developed the code used to analyze light from the distant galaxies.

As a postdoctoral fellow at the Harvard-Smithsonian Center for Astrophysics, Leja developed code capable of making sense of infrared data from distant galaxies, such as those imaged by Webb, proving that they are in fact our first glimpses of the very early universe.

“The code combines models of all the things that live in galaxies and interprets the light we observe from them,” said Leja. “This includes things like stars of various ages and elemental compositions, cosmic dust that blocks the light we see from stars, emission from gaseous nebulae, and so on.”

Two research papers, one led by Marco Castellano of the National Institute for Astrophysics in Rome, Italy, and another by Rohan Naidu of the Harvard-Smithsonian Center for Astrophysics and the Massachusetts Institute of Technology with Leja as co-author, have been published in the Astrophysical Journal Letters. The two papers describe the bright celestial objects, which both teams discovered separately in quick succession just days after Webb officially started science operations.

“With Webb, we were amazed to find the most distant starlight that anyone had ever seen, just days after Webb released its first data,” Naidu said in a NASA news release.

With just four days of analysis, the researchers found two exceptionally bright galaxies. They determined the young galaxies transformed gas into stars extremely rapidly, meaning the onset of stellar birth may have started just 100 million years after the big bang, roughly 13.8 billion years ago. The researchers also determined the two galaxies existed approximately 450 and 350 million years after the big bang, though future spectroscopic measurements with Webb will help confirm their findings.

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Swift telescope captures brightest gamma-ray burst ever recorded

2022-11-04

On October 9, 2022, an unusually bright and long-lasting gamma-ray burst—the most powerful type of explosion in the universe—was detected by the Neil Gehrels Swift Observatory, whose Mission Operations Center is located at Penn State and led by Professor of Astronomy and Astrophysics John Nousek. The burst—the brightest ever recorded, called GRB 221009A—originated from the death of a massive star about two billion light years away, likely collapsing to form a black hole and sending gamma rays, X-rays, and other particles into space.

A striking image of the burst’s afterglow was captured by Swift’s X-Ray Telescope, which is led by Penn State Research Professor of Astronomy and Astrophysics Jamie Kennea and was originally built under the leadership of Professor of Astronomy and Astrophysics David Burrows. Swift and other observatories are continuing to observe the aftermath of the event, which could help provide new insights into stellar collapse, the birth of a black hole, and the conditions in distant galaxies.

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NASA selects STAR-X for $3M mission concept study

2022-08-30

STAR-X, the Survey and Time-domain Astrophysical Research Explorer, a proposed NASA Medium-Class Explorer (MIDEX) mission that includes Penn State astronomer Niel Brandt, has been selected by the NASA Explorers Program for further study. STAR-X is one of two proposed MIDEX missions that will receive $3 million for a nine-month detailed study of mission requirements. At the end of this period, one of the proposed missions will be selected for a target launch date in 2027-2028 and be eligible for up to $300 million in additional funding.

Comprised of an X-ray telescope, an ultraviolet (UV) telescope, and a responsive spacecraft, STAR-X is designed to conduct time-domain surveys, which study how astronomical objects change with time, and to respond rapidly to transient cosmic events discovered by other observatories such as LIGO, Rubin LSST, the Roman Space Telescope, and the Square Kilometer Array. The mission is led by Principal Investigator William Zhang at NASA’s Goddard Space Flight Center (GSFC) in Greenbelt, Maryland. Penn State’s Brandt, who is the Verne M. Willaman Professor of Astronomy and Astrophysics and Professor of Physics, is involved in planning the STAR-X cosmic X-ray surveys, active galaxy studies, and fast X-ray transient studies.

“I can’t wait to use STAR-X to investigate the first supermassive black holes and understand mysterious, explosive X-ray transient sources,” said Brandt. “STAR-X will also provide the essential X-ray and UV follow-up capabilities for remarkable cosmic objects discovered by the Rubin LSST in optical light.”

The STAR-X spacecraft would be able to turn rapidly to point a sensitive wide-field X-ray telescope and a UV telescope at transient cosmic sources, such as supernova explosions and feeding supermassive black holes. Deep X-ray surveys would map black holes and hot gas trapped in distant clusters of galaxies; combined with infrared observations from NASA’s upcoming Roman Space Telescope, these observations would trace how massive clusters of galaxies built up over cosmic history.

STAR-X would provide revolutionary capabilities including unprecedented X-ray and UV volumetric survey speed; a unique combination of large field-of-view, large X-ray collecting area, low background, and excellent imaging; increased sensitivity for characterizing diffuse emissions, and increased speed and sensitivity for the discovery of faint X-ray point sources. It fills the gap in X-ray and UV survey coverage, providing simultaneous X-ray and UV observations, which are among the earliest and most uniquely informative astrophysical signals that probe the inner regions around compact objects like black holes and neutron stars, and it complements optical, infrared, and gravitational wave facilities.

The mission’s Deputy Principal Investigator, Ann Hornschemeier, who is also Lab Chief for X-ray Astrophysics at GSFC, earned a Ph.D. in Astronomy and Astrophysics at Penn State, mentored by Brandt, in 2002.

“Ann is superb - a bundle of energy, and the right person to push STAR-X to succeed,” said Brandt.

NASA Explorer missions conduct focused scientific investigations and develop instruments that fill scientific gaps between the agency’s larger space science missions. The proposals were competitively selected based on potential science value and feasibility of development plans. The Explorers Program is the oldest continuous NASA program and is designed to provide frequent, low-cost access to space using principal investigator-led space science investigations relevant to the Science Mission Directorate’s astrophysics and heliophysics programs.

“NASA’s Explorers Program has a proud tradition of supporting innovative approaches to exceptional science, and these selections hold that same promise,” said Thomas Zurbuchen, associate administrator for NASA’s Science Mission Directorate at NASA Headquarters in Washington. “From studying the evolution of galaxies to explosive, high-energy events, these proposals are inspiring in their scope and creativity to explore the unknown in our universe.”

Since the launch of Explorer 1 in 1958, which discovered the Earth’s radiation belts, the Explorers Program has launched more than 90 missions, including the Uhuru and Cosmic Background Explorer (COBE) missions that led to Nobel prizes for their investigators.

The program is managed by NASA Goddard for NASA’s Science Mission Directorate in Washington, which conducts a wide variety of research and scientific exploration programs for Earth studies, space weather, the solar system, and the universe. More information can be found at the Explorers Program website (https://explorers.gsfc.nasa.gov/).

Further technical details about the observatory are available at (http://star-x.xraydeep.org/observatory/).

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Hubble Finds Isolated Black Hole Roaming Our Milky Way Galaxy

2022-06-21

Though an estimated 100 million black holes are predicted to roam among the stars in our Milky Way galaxy, astronomers have never conclusively identified an isolated black hole – until now. Previously, black holes with the mass of the newly identified one had only been detected in binary systems in which the black hole is gravitationally bound to a normal, visible star. Now, following six years of meticulous observations, NASA’s Hubble Space Telescope has provided, for the first time ever, strong evidence for a lone black hole drifting through interstellar space.

A paper describing the discovery, by a team that includes Penn State astronomer Howard Bond, has been accepted for publication in the Astrophysical Journal.

“Black holes have been in the news recently as a spectacular image of the black hole at the center of our Milky Way galaxy was released a few weeks ago,” said Bond, professor of practice in astronomy and astrophysics at Penn State. “This black hole has a mass of 4 million times that of our Sun; it’s what’s called a supermassive black hole. Our object, by contrast, has a mass of only 7.1 times that of the Sun. It’s a ‘stellar-mass’ black hole. There are very likely many of these objects in the Milky Way, but they are extremely difficult to detect since they emit no light. Ours is the first one to be identified based on the black hole deflecting the image of a background star that it passed closely in front of.”

The black hole that was detected lies about 5,000 light-years away, in the Carina-Sagittarius spiral arm of our galaxy. For context, the nearest star to our solar system, Proxima Centauri, is a little over 4 light-years away.

Black holes roaming our galaxy are born from rare, monstrous stars (less than one-thousandth of the galaxy’s stellar population) that are at least 20 times more massive than our Sun. These stars explode as supernovae, and the remnant core is crushed by gravity into a black hole. Because the self-detonation is not perfectly symmetrical, the black hole may get a kick, and go careening through our galaxy like a blasted cannonball.

Telescopes can’t photograph a wayward black hole because it doesn’t emit any light. However, a black hole warps space, which then deflects and amplifies starlight from anything that momentarily lines up exactly behind it.

Ground-based telescopes, which monitor the brightness of millions of stars in the rich star fields toward the central bulge of our Milky Way, look for such a tell-tale sudden brightening of one of them when a massive object passes between us and the star. Then Hubble follows up on the most interesting such events.

Kailash Sahu of the Space Telescope Science Institute in Baltimore, Maryland, along with his team, made the discovery in a survey designed to find just such isolated black holes. The warping of space due to the gravity of a foreground object passing in front of a star located far behind it will briefly bend and amplify the light of the background star as it passes in front of it. The phenomenon, called gravitational microlensing, is used to study stars and exoplanets in the approximately 20,000 events seen so far inside our galaxy.

The signature of a foreground black hole stands out as unique among other microlensing events. The very intense gravity of the black hole will stretch out the duration of the lensing event for over 200 days.

Next, Hubble was used to measure the amount of deflection of the background star’s image by the black hole. Hubble is capable of the extraordinary precision needed for such measurements. The star’s image was offset from where it normally would be by two milliarcseconds. That’s equivalent to measuring the diameter of a 25-cent coin in Los Angeles as seen from New York City.

This astrometric microlensing technique provided information on the mass, distance, and velocity of the black hole. The amount of deflection by the black hole’s intense warping of space allowed the team to estimate it weighs about seven solar masses. The isolated black hole is traveling across the galaxy at 90,000 miles per hour (fast enough to travel from Earth to the moon in less than three hours). That’s faster than most of the other neighboring stars in that region of our galaxy.

“Astrometric microlensing is conceptually simple but observationally very tough,” said Sahu. “It is the only technique for identifying isolated black holes.”

The existence of stellar-mass black holes has been known since the early 1970’s, but all of them–until now–are found in binary star systems.

“Detections of isolated black holes will provide new insights into the population of these objects in our Milky Way,” said Sahu.

NASA’s upcoming Nancy Grace Roman Space Telescope will discover several thousand microlensing events out of which many are expected to be black holes, and the deflections will be measured with very high accuracy.

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