That Supermassive Black Hole in our Galaxy? It has a Friend.

Two black holes are entwined in a gravitational tango in this artist’s conception. Photo Credit: NASA/JPL-Caltech/SwRI/MSSS/Christopher Go

Smadar Naoz is an associate professor of physics and astronomy in the UCLA College. She wrote this article for The Conversation.

Do supermassive black holes have friends? The nature of galaxy formation suggests that the answer is yes, and in fact, pairs of supermassive black holes should be common in the universe.

I am an astrophysicist and am interested in a wide range of theoretical problems in astrophysics, from the formation of the very first galaxies to the gravitational interactions of black holes, stars and even planets. Black holes are intriguing systems, and supermassive black holes and the dense stellar environments that surround them represent one of the most extreme places in our universe.

The supermassive black hole that lurks at the center of our galaxy, called Sgr A*, has a mass of about 4 million times that of our sun. A black hole is a place in space where gravity is so strong that neither particles or light can escape from it. Surrounding Sgr A* is a dense cluster of stars. Precise measurements of the orbits of these stars allowed astronomers to confirm the existence of this supermassive black hole and to measure its mass. For more than 20 years, scientists have been monitoring the orbits of these stars around the supermassive black hole. Based on what we’ve seen, my colleagues and I show that if there is a friend there, it might be a second black hole nearby that is at least 100,000 times the mass of the sun.

Supermassive black holes and their friends

Almost every galaxy, including our Milky Way, has a supermassive black hole at its heart, with masses of millions to billions of times the mass of the sun. Astronomers are still studying why the heart of galaxies often hosts a supermassive black hole. One popular idea connects to the possibility that supermassive holes have friends.

To understand this idea, we need to go back to when the universe was about 100 million years old, to the era of the very first galaxies. They were much smaller than today’s galaxies, about 10,000 or more times less massive than the Milky Way. Within these early galaxies the very first stars that died created black holes, of about tens to thousand the mass of the sun. These black holes sank to the center of gravity, the heart of their host galaxy. Since galaxies evolve by merging and colliding with one another, collisions between galaxies will result in supermassive black hole pairs – the key part of this story. The black holes then collide and grow in size as well. A black hole that is more than a million times the mass of our sun is considered supermassive.

If indeed the supermassive black hole has a friend revolving around it in close orbit, the center of the galaxy is locked in a complex dance. The partners’ gravitational tugs will also exert its own pull on the nearby stars disturbing their orbits. The two supermassive black holes are orbiting each other, and at the same time, each is exerting its own pull on the stars around it.

The gravitational forces from the black holes pull on these stars and make them change their orbit; in other words, after one revolution around the supermassive black hole pair, a star will not go exactly back to the point at which it began.

Using our understanding of the gravitational interaction between the possible supermassive black hole pair and the surrounding stars, astronomers can predict what will happen to stars. Astrophysicists like my colleagues and me can compare our predictions to observations, and then can determine the possible orbits of stars and figure out whether the supermassive black hole has a companion that is exerting gravitational influence.

Using a well-studied star, called S0-2, which orbits the supermassive black hole that lies at the center of the galaxy every 16 years, we can already rule out the idea that there is a second supermassive black hole with mass above 100,000 times the mass of the sun and farther than about 200 times the distance between the sun and the Earth. If there was such a companion, then I and my colleagues would have detected its effects on the orbit of SO-2.

But that doesn’t mean that a smaller companion black hole cannot still hide there. Such an object may not alter the orbit of SO-2 in a way we can easily measure.

The physics of supermassive black holes

Supermassive black holes have gotten a lot of attention lately. In particular, the recent image of such a giant at the center of the galaxy M87 opened a new window to understanding the physics behind black holes.

The proximity of the Milky Way’s galactic center – a mere 24,000 light-years away – provides a unique laboratory for addressing issues in the fundamental physics of supermassive black holes. For example, astrophysicists like myself would like to understand their impact on the central regions of galaxies and their role in galaxy formation and evolution. The detection of a pair of supermassive black holes in the galactic center would indicate that the Milky Way merged with another, possibly small, galaxy at some time in the past.

That’s not all that monitoring the surrounding stars can tell us. Measurements of the star S0-2 allowed scientists to carry out a unique test of Einstein’s general theory of relativity. In May 2018, S0-2 zoomed past the supermassive black hole at a distance of only about 130 times the Earth’s distance from the sun. According to Einstein’s theory, the wavelength of light emitted by the star should stretch as it climbs from the deep gravitational well of the supermassive black hole.

The stretching wavelength that Einstein predicted – which makes the star appear redder – was detected and proves that the theory of general relativity accurately describes the physics in this extreme gravitational zone. I am eagerly awaiting the second closest approach of S0-2, which will occur in about 16 years, because astrophysicists like myself will be able to test more of Einstein’s predictions about general relativity, including the change of the orientation of the stars’ elongated orbit. But if the supermassive black hole has a partner, this could alter the expected result.

Finally, if there are two massive black holes orbiting each other at the galactic center, as my team suggests is possible, they will emit gravitational waves. Since 2015, the LIGO-Virgo observatories have been detecting gravitational wave radiation from merging stellar-mass black holes and neutron stars. These groundbreaking detections have opened a new way for scientists to sense the universe.

Any waves emitted by our hypothetical black hole pair will be at low frequencies, too low for the LIGO-Virgo detectors to sense. But a planned space-based detector known as LISA may be able to detect these waves which will help astrophysicists figure out whether our galactic center black hole is alone or has a partner.

This article originally appeared in the UCLA Newsroom.

Image of interstellar comet.

New NASA image provides more details about first observed interstellar comet

Image of interstellar comet.

The interstellar comet Comet 2I/Borisov (blueish image at right) near a spiral galaxy (left), in an image taken Nov. 16. Photo credit: NASA, ESA and David Jewitt/UCLA

A new image from NASA’s Hubble Space Telescope provides important new details about the first interstellar comet astronomers have seen in our solar system.

The comet, called Comet 2I/Borisov (the “I” stands for interstellar), was spotted near a spiral galaxy known as 2MASX J10500165-0152029. It was approximately 203 million miles from Earth when the image was taken on Nov. 16.

“Data from the Hubble Space Telescope give us the best measure of the size of comet 2I/Borisov’s nucleus, which is the really important part of the comet,” said David Jewitt, a UCLA professor of planetary science and astronomy who analyzed and interpreted the data from the new image.

Jewitt collaborated on the new analysis with colleagues from the University of Hawaii, Germany’s Max Planck Institute for Solar System Research, the Space Telescope Science Institute in Baltimore and Johns Hopkins University’s Applied Physics Laboratory. The scientists were surprised to learn that the nucleus has a radius measuring only about half of a kilometer — or less than one-fifteenth the size that earlier investigations suggested it might be.

“That is important because knowing its size helps us to determine the total number, and mass, of other similar objects in the solar system and the Milky Way,” Jewitt said. “2I/Borisov is the first known interstellar comet, and we would like to learn how many others there are.”

The comet is traveling at a breathtaking speed of 110,000 miles per hour — one of the fastest comets ever seen, Jewitt said. More commonly, comets travel at about half that speed.

Crimean astronomer Gennady Borisov discovered the comet on Aug. 30, using a telescope he built. Based on precise measurements of its changing position, the International Astronomical Union’s Minor Planet Center calculated a likely orbit for the comet, which shows that it came from elsewhere in the galaxy. Jewitt said its precise point of origin is unknown.

A second Hubble Space Telescope image of the comet, taken on Dec. 9, shows the comet even closer to Earth, approximately 185 million miles from Earth, he said.

Comets are icy bodies thought to be fragments left behind when planets form in the outer parts of planetary systems.

Observations by numerous telescopes show that the comet’s chemical composition is similar to that of comets previously observed in our solar system, which provides evidence that comets also form around other stars, Jewitt said. By mid-2020, the comet will have zoomed past Jupiter on its way back into interstellar space, where it will drift for billions of years, Jewitt said.

This article originally appeared in the UCLA Newsroom.

Picture of a valley oak tree.

One of California’s iconic tree species offers lessons for conservation

Picture of a valley oak tree.

The valley oak, the largest oak in California, grows to over 100 feet tall and provides habitat and food for a variety of animals. Photo credit: Victoria Sork/UCLA


With increasing regularity, Californians are witnessing firsthand the destructive power of wildfires. But not everyone sees what happens after the flames die down, when debris is cleared, homes and lives rebuilt — and trees replanted to help nature recover.

New research led by UCLA evolutionary biologist Victoria Sork examines whether the trees being replanted in the wake of California’s fires will be able to survive a climate that is continuing to warm.

The study, which is published in the Proceedings of the Natural Academy of Sciences, focuses on California’s iconic valley oak. The research is among the first to demonstrate the potential of using genomics to inform conservation strategies — essentially giving species an evolutionary boost. The study showed that planting trees that are genetically better suited to higher temperatures makes them more likely to survive and grow to maturity.

“When we think about managing ecosystems under rapidly changing climates, we have to realize trees need to be able to survive past 50 years,” Sork said.

The paper also discovered something surprising: The valley oak, an essential component of many ecosystems in California, is already poorly adapted to its environment — even considering climate conditions in 2019.

“They actually seem to grow better in cooler climates than they’re in right now,” said Luke Browne, a postdoctoral scholar at the UCLA La Kretz Center for California Conservation Science and the study’s lead author. “They might grow better if climates were more like they were 21,000 years ago, during the last ice age.”

During the peak of the last ice age, summer temperatures were about 4 to 5 degrees Celsius colder, and ice covered most of Canada and mountainous areas of the U.S.

In the fields of conservation and land management, it is a common assumption that plants and animals are adapted to their environments — that’s how evolution and natural selection are supposed to work. The new research casts doubt on that assumption.

The study is part of an ongoing project initiated by Sork and Jessica Wright, an expert in conservation genetics at the USDA Forest Service, more than 10 years ago.

Researchers gathered 11,000 seeds from 94 locations throughout the trees’ range, which stretches from the Santa Monica Mountains to the Cascade foothills in the northern part of the state. They grew them to saplings in a greenhouse and planted them in two large experimental gardens, in Chico and Placerville, California. They tracked how well trees from different locations grew, and sequenced the genomes of their mother trees to link genetic information and growth rates.

The researchers then identified which genetic variants would be more likely to thrive as climate change continues to warm California. They predicted that, under predicted future warmer temperatures, trees containing beneficial genetic variations would have 11% higher growth rates than the average for all of the trees in the experiment, and 25% higher growth rates than the trees without the beneficial variations.

Information like that could help the U.S. Forest Service, for example, in its efforts to restore forests with species that have the best chance for long-term survival.

“Studies like this one provide valuable insights that help land managers make informed decisions on reforestation projects,” Wright said. “When planting trees in a particular location, managers have to decide where to collect the acorns.”

By 2070, average temperatures in the state are projected to be up to 4.8 degrees warmer than they were during the mid- to late 20th century.

“That’s going to have consequences for how fast these trees grow,” Browne said. “We’re at a challenging time to figure out the best way to do conservation science. This paper shows one approach we could use that takes advantage of modern genomics.”

The study did not determine why valley oaks are not well adapted to their environment. It might be because the climate has already warmed up so much, the trees’ long lifespans — up to 500 years — or some other, unknown factor.

The valley oak is the largest oak in California; it grows to over 100 feet tall, and has dark green leaves and a deeply grooved trunk. It is considered a foundational species because it provides habitat and food for a variety of animals, including squirrels, birds, deer and insects. In parts of the state, it is one of the only species of tree that exists. Valley oaks provide benefits to humans, too: filtering water and providing shady places to escape the heat.

Although it focuses on the oak, the paper has broader implications for conservation science in a changing climate — especially for species that evolve and adapt slowly. That’s what Sork and Wright were thinking when they initiated the project.

At the time, they hoped to find conservation strategies that could eventually be implemented using genetic information alone — without extensive field experiments.

“Not everyone in the world is going to be able to collect 11,000 seeds and plant them in a common garden,” Sork said.

This article originally appeared in the UCLA Newsroom.

UCLA historian Kelly Lytle Hernández awarded MacArthur Fellowship

Kelly Lytle Hernández, a 2019 MacArthur Foundation Fellow, is one of 14 UCLA faculty to be chosen for the honor. Photo credit: John D. & Catherine T. MacArthur Foundation

UCLA professor Kelly Lytle Hernández, an award-winning author and scholar of race, mass incarceration and immigration, was announced today as a recipient of a prestigious MacArthur Fellowship from the John D. and Catherine T. MacArthur Foundation.

Lytle Hernández, who is a professor of history and African American studies, is the director of UCLA’s Ralph J. Bunche Center for African American Studies, which under her leadership has focused on supporting research into two critical themes in the modern black world — work and justice. The Bunche Center is home to Million Dollar Hoods, which maps the fiscal and human cost of mass incarceration in Los Angeles. Lytle Hernández is the director and principal investigator on the project.

“Lytle Hernández’s investigation of the intersecting histories of race, mass incarceration, immigration, and cross-border politics is deepening our understanding of how imprisonment has been used as a mechanism for social control in the United States,” the foundation said.

The MacArthur Fellowship is a $625,000, no-strings-attached award to people the foundation deems “extraordinarily talented and creative individuals.” Fellows are chosen based on three criteria: exceptional creativity, promise for important future advances based on a track record of accomplishments, and potential for the fellowship to facilitate subsequent creative work. Lytle Hernández is one of 26 individuals the foundation selected for fellowships in 2019.

“As a scholar, I both work deeply alone and deeply in community, but until very recently the scholarly communities I’ve worked in — immigration and the carceral state — have been fairly separate,” said Lytle Hernández, who holds the Thomas E. Lifka Chair in History at UCLA. “I hope my work has helped people understand immigration as another aspect of mass incarceration in the United States and that my award further helps people understand that these two regimes are intertwined. This award will help us continue this work across communities and shine a light on this kind of thinking that unites these two crises that others often see as distinct.”

Lytle Hernández, 45, received a her bachelor’s degree from UC San Diego in 1996 and earned her doctorate in 2002 from UCLA.

For her first book, “MIGRA! A History of the U.S. Border Patrol,” Lytle Hernández pored over historical records to illuminate the border patrol’s nearly exclusive focus on policing unauthorized immigration from Mexico.

In “City of Inmates: Conquest, Rebellion, and the Rise of Human Caging in Los Angeles,” she began zeroing in on another dimension of race and law enforcement, specifically what forces shaped Los Angeles so that it came to operate the largest jail system in the United States.

“What I found in the archives is that since the very first days of U.S. rule in Los Angeles — the Tongva Basin — incarceration has persistently operated as a means of purging, removing, caging, containing, erasing, disappearing and otherwise eliminating indigenous communities and racially targeted populations,” Lytle Hernández said in an interview about the book.

The MacArthur Fellowship, which is commonly referred to as the “genius grant,” is according to the foundation, intended to encourage people of outstanding talent to pursue their own creative, intellectual and professional inclinations. Recipients may be writers, scientists, artists, social scientists, humanists, teachers, entrepreneurs, or those in other fields, with or without institutional affiliations.

Lytle Hernández joins 13 other UCLA faculty as MacArthur fellows, including mathematician Terence Tao, choreographer Kyle Abraham, director Peter Sellars, astrophysicist Andrea Ghez and historian of religion Gregory Schopen.

While unsure of her specific plans for the award, Lytle Hernández said that she will continue to expand the scope and scale of her social justice scholarship, including with partners outside of UCLA.

“I’d like to create a space for myself and others — especially community organizers and movement-driven scholars — to write,” she said, noting that these people’s calendars tend to be jammed by the “urgency of their work.” “I’d like to create space that allows myself and others to process the work that we’re doing and to share it.”

This article originally appeared in the UCLA Newsroom.

College Senior José Gonzalez is on a Mission to Understand Autism

L to R – Megan McEvoy, Jose Gonzalez, Gina Poe,

UCLA senior José Gonzalez is on a mission to move the needle on autism research. With the support of COMPASS, his family and his mentors, he is well on his way.

The California native was raised in a small Central Valley town in the heart of the state’s agricultural greenbelt. All five of José’s siblings earned college degrees—a point of great pride for his parents, who were unable to receive an education past the sixth grade.

“My parents always stressed the importance of higher education as the way to move up,” Jose said.

José’s father, originally from Mexico, works as a foreman in the citrus orchards of The Wonderful Company, which provides college scholarships and other incentives for their employees’ children who maintain good GPAs. That financial assistance helped the Gonzalez children pay for college.

In his sophomore year, José began participating in COMPASS and received the Life Sciences Dean’s Award, which provides stipends allowing students to pursue research work rather than work at part-time jobs. He has benefited from the invaluable guidance and mentorship of UCLA faculty and COMPASS co-directors Megan McEvoy and Gina Poe, scientists who have helped José navigate the challenges of a science degree.

Now a senior, José works in the lab of one of the world’s leading autism experts, Dr. Daniel Geschwind, studying genes that regulate developmental pathways integral to brain development. José’s decision to study autism was spurred when his nephew was diagnosed with the disorder, and he says the experience has been transformative.

“Without COMPASS, I would not have had the chance to work in Dr. Geschwind’s lab or be on the career trajectory I’m on now,” he said.

José’s goal is to become a pediatric neurologist with his own lab at a university, much like his mentor, Dr. Geschwind.