The Intermittent Growth of the First Supermassive Black Holes

May
31
Edwige Pezzulli
Dr. Edwige Pezzulli

It is a pleasure to welcome Edwige Pezzulli as a guest blogger. Edwige led the black hole study that is the subject of our latest press release. She is a Ph.D. student at the University la Sapienza in Rome (Italy), under the supervision of Raffaella Schneider. During her Ph.D., she spent several months at the Institute d’Astrophysique de Paris (IAP) in France. She has mainly worked on the study of the origin and properties of the first black holes in the Universe.

“As an adult, I’d like to be sent into a black hole!” This is my first memory from childhood on the topic of space.

Since then, I have studied and discovered a lot more about black holes, and yet they still fascinate me in the same way. Considered, for many, the most exotic objects ever discovered, supermassive black holes are the tip of the iceberg of the “dark” side of the Universe. Supermassive black holes are behemoths located in the centers of galaxies and can be among the most luminous sources ever known, from the radiation of surrounding material.

In particular, observations of the Universe’s earliest supermassive black holes, with masses about a billion times that of the Sun, open the door to many questions, especially this one: how did these monsters form in such a short time?

Astronomers find black holes with similar masses in the present-day universe, but these black holes have grown to their enormous size over a much longer period of time – about 13.8 billion years – compared to those that formed about a billion years after the Big Bang. In order to tackle the question of how supermassive black holes formed in the very early Universe, it is imperative to make numerous observations of the light they generate while pulling in, ie accreting, matter as they grow.

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Observatories Combine to Crack Open the Crab Nebula

May
10
Screening
The Crab Nebula

Astronomers have produced a highly detailed image of the Crab Nebula, by combining data from telescopes spanning nearly the entire breadth of the electromagnetic spectrum, from radio waves seen by the Karl G. Jansky Very Large Array (VLA) to the powerful X-ray glow as seen by the orbiting Chandra X-ray Observatory. And, in between, the Hubble Space Telescope's crisp visible-light view and the infrared perspective of the Spitzer Space Telescope.

The Crab Nebula, the result of a bright supernova explosion seen by Chinese and other astronomers in the year 1054, is 6,500 light-years from Earth. At its center is a super-dense neutron star, rotating once every 33 milliseconds, shooting out rotating lighthouse-like beams of radio waves and light — a pulsar. The nebula's intricate shape is caused by a complex interplay of the pulsar, a fast-moving wind of particles coming from the pulsar, and material originally ejected by the supernova explosion and by the star itself before the explosion.

This image combines data from five different telescopes: The VLA (radio) in red; Spitzer Space Telescope (infrared) in yellow; Hubble Space Telescope (visible) in green; XMM-Newton (ultraviolet) in blue; and Chandra X-ray Observatory (X-ray) in purple.

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Astronomers Pursue Renegade Supermassive Black Hole

May
09
illustration
CXO J101527.2+625911

Supermassive holes are generally stationary objects, sitting at the centers of most galaxies. However, using data from NASA's Chandra X-ray Observatory and other telescopes, astronomers recently hunted down what could be a supermassive black hole that may be on the move.

This possible renegade black hole, which contains about 160 million times the mass of our Sun, is located in an elliptical galaxy about 3.9 billion light years from Earth. Astronomers are interested in these moving supermassive black holes because they may reveal more about the properties of these enigmatic objects.

This black hole may have "recoiled," in the terminology used by scientists, when two smaller supermassive black holes collided and merged to form an even larger one. At the same time, this collision would have generated gravitational waves that emitted more strongly in one direction than others. This newly formed black hole could have received a kick in the opposite direction of those stronger gravitational waves. This kick would have pushed the black hole out of the galaxy's center, as depicted in the artist's illustration.

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Is Dark Matter "Fuzzy"?

Apr
27
Screening
Four of the 13 galaxies clusters used in the study. The clusters are, starting at the top left
and going clockwise, Abell 262, Abell 383, Abell 1413, and Abell 2390.

Astronomers have used data from NASA's Chandra X-ray Observatory to study the properties of dark matter, the mysterious, invisible substance that makes up a majority of matter in the universe. The study, which involves 13 galaxy clusters, explores the possibility that dark matter may be more "fuzzy" than "cold," perhaps even adding to the complexity surrounding this cosmic conundrum.

For several decades, astronomers have known about dark matter. Although it cannot be observed directly, dark matter does interact via gravity with normal, radiating matter (that is, anything made up of protons, neutrons, and electrons bundled into atoms). Capitalizing on this interaction, astronomers have studied the effects of dark matter using a variety of techniques, including observations of the motion of stars in galaxies, the motion of galaxies in galaxy clusters, and the distribution of X-ray emitting hot gas in galaxy clusters. Dark matter has also left an imprint on the radiation left over from the Big Bang 13.8 billion years ago.

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The Arrhythmic Beating of a Black Hole Heart

Apr
18
Screening
NGC 4696

At the center of the Centaurus galaxy cluster, there is a large elliptical galaxy called NGC 4696. Deeper still, there is a supermassive black hole buried within the core of this galaxy.

New data from NASA's Chandra X-ray Observatory and other telescopes has revealed details about this giant black hole, located some 145 million light years from Earth. Although the black hole itself is undetected, astronomers are learning about the impact it has on the galaxy it inhabits and the larger cluster around it.

In some ways, this black hole resembles a beating heart that pumps blood outward into the body via the arteries. Likewise, a black hole can inject material and energy into its host galaxy and beyond.

By examining the details of the X-ray data from Chandra, scientists have found evidence for repeated bursts of energetic particles in jets generated by the supermassive black hole at the center of NGC 4696. These bursts create vast cavities in the hot gas that fills the space between the galaxies in the cluster. The bursts also create shock waves, akin to sonic booms produced by high-speed airplanes, which travel tens of thousands of light years across the cluster.

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Pathways to the Stars -- I

Apr
06
Blog placeholder graphic
Illustration: NASA/CXC/K.DiVona

(A continuing series on how astrophysicists’ varied career paths. Pathways to the Stars -- II)

Our blogger today is Dr. Wallace Tucker, who has worked on the Chandra project since its inception and has been involved with high-energy astrophysics for several decades. In one of his many roles, Wallace has served as the Chandra Science Spokesperson, helping non-experts understand and enjoy the amazing discoveries Chandra makes. He is the author of several popular books including one published by Smithsonian Books.


How did you get to be an astrophysicist working with the Chandra X-ray Observatory?

This is a question that almost all of us who work with Chandra get asked at one point or another. Apart from cocktail party conversation — not that astrophysicists go to that many cocktail parties, in my experience — the answer is relevant in terms of ongoing efforts to increase the number of young people seeking careers in science, technology, engineering and mathematics.

And, on the principle that "none of us is as smart as all of us," it is important for maximizing the scientific return of Chandra to get as many people involved as possible. Think about it: some of the bright young minds working on Chandra data today were in elementary school when Chandra was launched!

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400 Students, Educators, and Technology Professionals Attend "Hidden Figures" Event

Apr
04
Screening
Photo Credit: Tracy Karin Prell

Over 400 female middle and high school students, educators, and technology professionals attended a viewing of Hidden Figures and panel discussion at the Warwick Showcase Cinemas on Friday, March 24, 2017. The event was presented by Tech Collective, Rhode Island's industry association for technology, in partnership with NASA's Chandray X-ray Observatory and Providence P-TECH industry partners. The event included a private screening of the 2017 Oscar winning movie followed by a panel discussion featuring a diverse group of female STEAM professionals in Rhode Island.

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A Serendipitous Discovery May Provide Our First View of a New Population of X-ray Transients

Mar
28
Franz E. Bauer
Franz E. Bauer

It is a pleasure to welcome Franz E. Bauer as a guest blogger. Franz led the study that is the subject of our latest press release. He is an associate professor at Pontificia Universidad Catolica de Chile in Santiago, Chile, where his group studies the cosmic evolution of star-forming galaxies and supermassive black holes, as well as a variety of transient phenomena. He completed his PhD at the University of Virginia in 2001, then worked at Pennsylvania State University, University of Cambridge (UK), and Columbia University before finally moving to Chile.

Like many discoveries in astrophysics, the subject of our recent study was an act of serendipity. Our large international collaboration had been allocated a series of long observations with Chandra to push the exposure from 45 days to 75 days for the deepest X-ray image on the sky to date, the Chandra Deep Field-South (CDF-S). The primary goal of this project was to explore the poorly understood realm of the ultra-faint X-ray universe, to learn how supermassive black holes form in the early Universe and by what mechanisms they grow to become the present day "monsters" that we see today (for details, see a January 2017 press release led by Bin Luo from Nanjing University and Fabio Vito from Penn State University and an associated blog post by Fabio Vito). However, the leaders of this project, colleagues Drs. Niel Brandt (Penn State University) and Bin Luo, had studied variability from known X-ray objects in the previous data containing 45 days of exposure, and were thus monitoring the individual observations as they arrived to check for large deviations.

To our surprise, during one 13-hour observation on October 1st, 2014, a bright, new source emerged (see Figure 1), at a location where no source had been detected, even when summing up all of the previous exposures together. Two days later, in the next Chandra observation, it was gone! We had never anticipated that our observations would capture such a rare, fast transient. After convincing ourselves that it was not some weird instrumental effect, we reported it to the astronomy community as Luo, Brandt & Bauer (2014) in ATEL 6541, to encourage follow-up observations at other wavelengths and gain more clues as to the origin of this unique event.

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A White Dwarf and a Black Hole in a Tight Orbit

Mar
13
Dr. Arash Bahramian
Dr. Arash Bahramian

We are very happy to welcome Dr. Arash Bahramian as our guest blogger. Dr. Bahramian completed his graduate studies at University of Alberta, Canada with Dr. Craig Heinke on X-ray binaries in globular clusters. After defending his PhD in 2016, he moved to Michigan State University to work with Dr. Jay Strader on study of black holes in globular clusters. He is the first author of the paper featured in our most recent press release.

Stellar mass black holes are formed by the deaths of massive stars. Like other black holes, these objects do not emit any light of their own, and astronomers try to identify them from their interactions with their environment. For example, in a close binary with another star, the black hole's strong gravity pulls material from the companion star. This material falls towards the black hole through a disk called an accretion disk. The massive release of energy due to infall of matter towards the black hole plus friction between particles in the disk, makes this disk extremely hot (about a million degrees Kelvin, roughly 200 times hotter than the surface of the Sun). This temperature is high enough to make the disk bright in X-rays, and so X-ray observatories like NASA's Chandra X-ray Observatory have been used to identify and study these systems.

Over the last few decades, dozens of stellar mass black holes (and black hole candidates) in close binaries with another star have been identified throughout our Galaxy. However, none of these black holes were found in old dense stellar clusters known as globular clusters. This was surprising at first, as we would expect a lot of black holes (maybe around 1000 of them) in these clusters, because many massive stars should have turned into black holes. Furthermore, a crowded stellar environment like a cluster makes interactions between black holes and other stars more likely. For a long time, this absence of black holes in dense stellar clusters was thought to be a result of black holes getting kicked out of the cluster, due to their strong gravity and rapid movement after interacting with other stars and other black holes in the cluster.

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From Art to Astrophysics – and Back Again

Mar
02
Melissa Weiss Walter
Melissa Weiss Walter (Photo: Brin Deuk Morris)

We are thrilled to welcome Melissa Weiss Walter as a guest blogger. As Mel describes below, she served as the graphic designer, illustrator and social media developer for Chandra's publicity and outreach efforts for many years. Recently, she has scaled back her Chandra time to focus on her personal artistic endeavors. Thankfully, she remains part of the Chandra family and continues to contribute to Chandra releases.

I have been working with the Chandra team in various capacities for close to two decades. I began creating illustrations of black holes after graduating from the University of Rhode Island. Soon after Chandra launched, I was brought on board to continue as their science illustrator and also as their graphic designer. When MySpace took off like a rocket and we realized that social media was here to stay, I also took on the role as a social media administrator.

In 2015, after working with the team full-time for fourteen years, I made the decision to take a step back. I was able to continue just with my duties in science illustration so that I could pursue a career in fine art. Though I may have discontinued my time with Chandra on a full-time basis, I took with me the inspiration of many years looking at the wonders of our Universe through Chandra's eyes.

Before making the change, I had always loved the work I did with the Chandra team. However, I was so busy creating materials that I didn't have a lot of time to reflect on the content I was using. I knew what we did was important but I never realized how influenced I was becoming by the wonders we communicated with the public on a daily basis.

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