Black Holes

NASA Telescopes Capture Stellar Delivery Service for Black Hole

Image of NGC 4424 with close-up inset image
NGC 4424
Credit: X-ray: NASA/CXC/Swinburne Univ. of Technology/A. Graham et al.; Optical: NASA/ESA/STScI

Astronomers may have witnessed a galaxy’s black hole delivery system in action. A new study using data from NASA’s Chandra X-ray Observatory and Hubble Space Telescope outlines how a large black hole may have been delivered to the spiral galaxy NGC 4424 by another, smaller galaxy.

NGC 4424 is located about 54 million light-years from Earth in the Virgo galaxy cluster. The main panel of this image, which has been previously released, shows a wide-field view of this galaxy in optical light from Hubble. The image is about 45,000 light-years wide. The center of this galaxy is expected to host a large black hole estimated to contain a mass between about 60,000 and 100,000 Suns. There are also likely to be millions of stellar-mass black holes, which contain between about 5 and 30 solar masses, spread throughout the galaxy.

Chandra Unveils Rotation Speed of One of the Most Massive Black Holes Ever Seen

Image of Julia Sisk-Reynés standing on an urban street in front of a monument.
Julia Sisk-Reynés

Our guest contributor is Julia Sisk-Reynés, the leader of a new black hole study that is the subject of our latest press release. Julia is a second-year PhD student at the Institute of Astronomy at the University of Cambridge, UK, where she is a member of the X-ray group working mainly with Prof. Chris Reynolds and Dr. James Matthews. Her primary focus is on constraining beyond the Standard Model Physics – in particular, axion-like particles (ALPs)- with X-ray observations of cluster-hosted active galaxies. The team have recently set the tightest limits to-date on the coupling of very light ALPs to electromagnetism with Chandra X-ray observations of the cluster-hosted quasar H1821+643. Julia came to Cambridge in 2020, straight after graduating from the University of Manchester with a master’s degree in physics. Amongst others, she did a project on assessing the sensitivity of the DarkSide-20k liquid argon experiment in Gran Sasso, Italy, to direct dark matter detection.

Black holes are one of the most tantalizing objects in the Universe. By 1915, Einstein’s Theory of General Relativity had introduced the notion that the gravity of black holes is so strong that they can distort the space-time around them … to the point where even light close to the black hole cannot escape! More recently, astronomers have gathered evidence that most – if not all – galaxies emitting lots of light at the center (also called active galactic nuclei or AGN) host a very massive black hole at their core. It is known that the properties of AGN and their central black holes are often linked. For example, the heavier the AGN, the heavier its host black hole. Therefore, the formation, growth, and evolution of black holes over time and their connection with the properties of their host galaxies are fascinating topics for astronomers to pursue.

Astronomers classify black holes into three groups, depending on their mass. Firstly, stellar-mass black holes, thought to form from the gravitational collapse of a star, weigh a few to a few tens of times the mass of the Sun. Then, we have a class of black holes of unknown origin which range from hundreds to tens of thousands of Suns, often referred to as “intermediate mass” black holes. A gravitational wave event detected in 2019 by the LIGO and VIRGO collaborations confirmed the existence of a black hole in this second category. Finally, supermassive Black Holes (SMBHs) weigh between millions and billions of Suns. While their origin is still debated, what we do know is that accretion, that is, the feeding of gas onto such black holes, is responsible for the X-ray emission coming from the AGN that surround them.

Looking at the Team Behind the Science

Image of sgra
Sagittarius A*: The Black Hole at the Center of the Milky Way Galaxy
Credit: X-ray: NASA/CXC/SAO; IR: NASA/HST/STScI. Inset: Radio (EHT Collaboration)

Many projects in astrophysics involve huge numbers of scientists and other collaborators — often ranging from senior professors to graduate students and undergraduates. A project like the EHT often requires smaller groups within these large collaborations to concentrate on different problems and questions.

The latest result about the Milky Way's central black using many different telescopes in concert with the Event Horizon Telescope (EHT) is an excellent example of such a successful web of groups working together with others in the project to make the sum even greater than its parts.

To learn more about the group behind the "multiwavelength" (MWL) observations that included Chandra and other telescopes, we asked Sera Markoff and Daryl Haggard, two of the coordinators of the EHT's MWL Working Group, a series of questions.

New NASA Black Hole Sonifications with a Remix

Credit: X-ray: NASA/CXC/Univ. of Cambridge/C. Reynolds et al.; Sonification: NASA/CXC/SAO/K.Arcand, SYSTEM Sounds (M. Russo, A. Santaguida)

Black Hole at the Center of the Perseus Galaxy Cluster (above)

Since 2003, the black hole at the center of the Perseus galaxy cluster has been associated with sound. This is because astronomers discovered that pressure waves sent out by the black hole caused ripples in the cluster's hot gas that could be translated into a note — one that humans cannot hear some 57 octaves below middle C. Now a new sonification brings more notes to this black hole sound machine. This new sonification — that is, the translation of astronomical data into sound — is being released for NASA's Black Hole Week this year.

In some ways, this sonification is unlike any other done before (1, 2, 3, 4) because it revisits the actual sound waves discovered in data from NASA's Chandra X-ray Observatory. The popular misconception that there is no sound in space originates with the fact that most of space is essentially a vacuum, providing no medium for sound waves to propagate through. A galaxy cluster, on the other hand, has copious amounts of gas that envelop the hundreds or even thousands of galaxies within it, providing a medium for the sound waves to travel.

Exploring New Pathways for Massive Black Hole Formation with Chandra

Image of Vivienne Baldassare
Vivienne Baldassare

We are happy to welcome Vivienne Baldassare as our guest blogger. Vivienne is an Assistant Professor of Physics and Astronomy at Washington State University, and led the paper that is the subject of our latest press release. Her work is mainly focused on searching for the smallest supermassive black holes in order to learn more about black hole formation and growth. Prior to her current position, she was a NASA Einstein fellow at Yale University. She earned her PhD in Astronomy & Astrophysics from the University of Michigan in 2017, and a bachelor's degree in Physics from CUNY Hunter College in 2012.

One of the biggest open questions in astrophysics is “how do massive black holes form?” Our recent research with NASA’s Chandra X-ray Observatory provides support for the theory that massive black holes can form in what astronomers call nuclear star clusters.

While big galaxies have supermassive black holes at their centers, small galaxies often have a nuclear star cluster. Nuclear star clusters are extremely dense, with millions of stars packed into a region that is tens of light years across. It was once suggested that supermassive black holes and nuclear star clusters may be mutually exclusive, with the former residing in big galaxies and the latter occurring in small galaxies. However, some galaxies (like our Milky Way!) have been found to contain both. And excitingly, some theories suggest that nuclear star clusters might be able to form massive black holes.

In my first year of graduate school, I carried out a project studying the properties of nuclear star clusters. After that, I transitioned to studying massive black holes in dwarf galaxies, but have always had a soft spot for these fascinating objects. Our new study brought these two areas together.

Feasting Black Holes Caught in Galactic Spiderweb

Image of the Spiderweb Galaxy Field
Spiderweb Galaxy Field
Credit: X-ray: NASA/CXC/INAF/P. Tozzi et al; Optical (Subaru): NAOJ/NINS; Optical (HST): NASA/STScI

Often, a spiderweb conjures the idea of captured prey soon to be consumed by a waiting predator. In the case of the "Spiderweb" protocluster, however, objects that lie within a giant cosmic web are feasting and growing, according to data from NASA's Chandra X-ray Observatory.

The Spiderweb galaxy, officially known as J1140-2629, gets its nickname from its web-like appearance in some optical light images. This likeness can be seen in the inset box where data from NASA's Hubble Space Telescope shows galaxies in orange, white, and blue, and data from Chandra is in purple. Located about 10.6 billion light years from Earth, the Spiderweb galaxy is at the center of a protocluster, a growing collection of galaxies and gas that will eventually evolve into a galaxy cluster.

"Mini" Monster Black Hole Could Hold Clues to Giant's Growth

Image of mrk462
Mrk 462
Credit: X-ray: NASA/CXC/Dartmouth Coll./J. Parker & R. Hickox; Optical/IR: Pan-STARRS

The graphic shows X-rays that NASA's Chandra X-ray Observatory detected from the dwarf galaxy Mrk 462. This X-ray emission (inset) is important because it reveals the presence of a growing supermassive black hole within this relatively small galaxy, as described in our latest press release. The mass contained in this black hole — about 200,000 times the mass of the Sun — provides information to astronomers about how some of the earliest black holes in the Universe may have formed and grown billions of years ago.

The background panel is an optical image from the Pan-STARRS telescope in Hawaii. There are several galaxies that are part of the HCG068 galaxy group on the left-hand side of the image. The galaxy that is emitting copious amounts of X-rays, however, is the much smaller galaxy located to the lower right of the image (marked by the arrow). Mrk 462 is a dwarf galaxy because it contains only a few hundred million stars, which means it holds about a hundred times fewer stars than a galaxy like the Milky Way. Black holes are notoriously hard to find in dwarf galaxies because they are usually too small and dim for optical light telescopes to track the rapid motions of stars in the centers.

Astronomers Spy Quartet of Cavities From Giant Black Holes

Optical & X-ray Images of  RBS 797, side-by-side
Galaxy Cluster RBS 797
Credit: X-ray: NASA/CXC/Univ. of Bologna/F. Ubertosi; Optical: NASA/STScl/M.Calzadilla

Four enormous cavities, or bubbles, have been found at the center of a galaxy cluster using NASA's Chandra X-ray Observatory, as described in our latest press release. The left panel of this graphic shows an optical image of the galaxy cluster called RBS 797, from NASA's Hubble Space Telescope. Hot gas that envelopes the individual galaxies is invisible in optical light, but it is detected in X-rays by Chandra (right). One pair of cavities can be seen towards the left and right of center in the Chandra image as black oval-shaped regions. The other pair is less distinct, but can be found above and below the center of the image.

"X-ray Magnifying Glass" Enhances View of Distant Black Holes

X-ray image and illustration of MG B2016+112
Gravitationally-Lensed System MG B2016+112
Credit: Illustration: NASA/CXC/M. Weiss; X-ray (inset): NASA/CXC/SAO/D. Schwartz et al.

A new technique using NASA's Chandra X-ray Observatory has allowed astronomers to obtain an unprecedented look at a black hole system in the early Universe, as reported in our latest press release. This is providing a way for astronomers to look at faint and distant X-ray objects in more detail than had previously been possible.

Astronomers used an alignment in space that shows "gravitational lensing" of light from two objects that are nearly 12 billion light years away. An artist's illustration in the main part of this graphic shows how the paths of light from these distant objects are bent and amplified by a galaxy along the line of sight between Earth and the objects.

Huge Rings Around a Black Hole

Image of V404 Cygni
V404 Cygni
Credit: X-ray: NASA/CXC/U.Wisc-Madison/S. Heinz et al.; Optical/IR: Pan-STARRS

This image features a spectacular set of rings around a black hole, captured using NASA's Chandra X-ray Observatory and Neil Gehrels Swift Observatory. The X-ray images of the giant rings reveal information about dust located in our galaxy, using a similar principle to the X-rays performed in doctor's offices and airports.

The black hole is part of a binary system called V404 Cygni, located about 7,800 light years away from Earth. The black hole is actively pulling material away from a companion star — with about half the mass of the Sun — into a disk around the invisible object. This material glows in X-rays, so astronomers refer to these systems as "X-ray binaries."

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