Mass of black holes compared to parent star

Mass of black holes compared to parent star

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What is the range of percentage mass of parent star left in a stellar black hole directly after its formation?

What factors determine this number for a specific case?

There is no general consensus on this. Different evolutionary models give different results. The factors (in addition to the initial mass of the star) that effect the final black hole mass would be the rotation rate of the progenitor, its composition (or metallicity) and whether it was in a binary system or not and whether that binary system was able to transfer mass.

Rotation is thought to be important because it affects internal mixing and therefore the rate at which fuel is supplied to the core and the rat at which processed material gets to the surface, affecting the atmospheric composition. It can also enhance mass loss.

The composition is important because mass loss is driven by radiation and radiative opacities are higher for high metallicity compositions.

A set of calculations by Heger et al. (2003) are one of the canonical works on this subject. Below is a plot of initial mass versus remnant mass for stars with big bang primordial abundance (zero initial metallicity) and then the same again for stars of solar metallicity.

The ratio of the red line to dotted "no mass loss" line gives the fraction you are after. In zero metallicity (primordial) stars it increases from 10-40% for initial masses of 25-100 solar masses and is perhaps even higher for supermassive population III stars. (I stress that these are theoretical results).

For solar metallicity stars the results are a bit different. The ratio of the red line to the dotted line varies from 10-25% for 25-40 solar masses, but then it is not clear whether black holes can even form at even higher masses because of the much higher mass loss rates (see the difference between the dotted line and the blue curve).

Your question regards the formation of stellar-mass black holes, which form as the result of a Type II or Type Ib supernova explosion. This occurs when a massive star's core collapses from its own self-gravity, driving a rapid release of energy through nuclear reactions. This imparts a tremendous amount of energy in the form of photons and neutrinos to the rest of the star, which, as a result, blows the star up. This core region either becomes a neutron star or, when the mass of this core region is high enough, collapses directly into a black hole. While stars that can explode through this channel are rare in the Milky Way, i.e., compared to stars like our Sun, there are likely ~billions of neutron stars and stellar-mass black holes that have formed through this process.

Stars that explode as supernova are indeed massive, weighing in with masses at least ~8 times the mass of the Sun. Those that produce black holes in the center are even higher, usually above ~20 solar masses or so (this number is disputed… some of the nuclear physics in these extreme environments is uncertain).

Figure 2 of this paper might shed some light (… ) on your question. This paper ran a set of stellar evolution models to track how much mass was expelled during the explosion and how much mass remained post explosion. The horizontal axis gives the original mass of the star (in units of the Sun's mass, e.g., a value of 10 means 10 times the mass of the Sun), and the solid circles identify the final mass of the leftover remnant--which is either a neutron star or black hole. The vertical axis gives the mass of the remnant. Sadly they decided to use logarithmic space for the vertical axis, even though the range is only over a single order of magnitude. So to get the actual amount of mass, you have to undo the base-10 logarithm. For example, if a black dot had a value of 0.3 on the vertical axis, the mass of the remnant would be 10^(0.3) = 2.0 times the mass of the Sun. A value of 0.6 would be 10^(0.6) = 3.98 times the mass of the Sun, etc. They considered several different mechanisms for the explosion at higher masses (remember, things get more uncertain the bigger the star gets), which is why some horizontal values have multiple black dots. If you're curious, weaker explosions can allow some of the material to fall back down onto the remnant, which results in a black dot that is higher up on the plot.

Regardless, you can see that, for example, a 20 solar mass star creates a 10^(0.3)=2 solar mass remnant. A 30 solar mass star might create a remnant that is between 2 and 4 times the mass of the Sun. In all cases, the majority of the star's original mass is lost.

You might also glance at the plots of this paper as well. This paper looks like it did a slightly more careful job. Either paper still gives you the basic picture, however.

(Aside: Figure 2 is for 'solar metallicity' stars, which means 'stars that you might find in the Milky Way.' Figure 1 is for stars that would have formed in the early Universe, before a considerable amount of elements beyond helium had been formed.)

Intermediate-Mass Black Holes

Dynamical and accretion signatures alike point to a high fraction of 10 9 –10 10 M galaxies hosting black holes with MBH∼ 10 5 M. In contrast, there are no solid detections of black holes in globular clusters.

There are few observational constraints on black holes in any environment with MBH ≈ 100–10 4 M.

Considering low-mass galaxies with dynamical black hole masses and constraining limits, we find that the MBH–σ* relation continues unbroken to MBH ∼10 5 M, albeit with large scatter. We believe the scatter is at least partially driven by a broad range in black hole masses, because the occupation fraction appears to be relatively high in these galaxies.

We fold the observed scaling relations with our empirical limits on occupation fraction and the galaxy mass function to put observational bounds on the black hole mass function in galaxy nuclei.

We are pessimistic that local demographic observations of galaxy nuclei alone could constrain seeding mechanisms, although either high-redshift luminosity functions or robust measurements of off-nuclear black holes could begin to discriminate models.

Nearby black hole Cyg X-1 more massive than thought

A new study suggests that one of the closest black holes to Earth, and the first ever detected, is both farther away and more massive than we thought.

The study – published February 18, 2021 in the peer-reviewed journal Science – says that Cygnus X-1 is about 7,200 light-years from Earth, 20% farther away than astronomers had previously believed. Before the study’s new measurements, the black hole was believed to be about 6,100 light-years away and 15 times the mass of the sun. With an increase in distance, Cygnus X-1 is now believed to be 50% larger than previous estimates. That would make this black hole about 21 times the mass of our sun.

The new measurements make Cygnus X-1 the most massive stellar-mass black hole ever found without the use of gravitational waves.

Artist’s concept shows a stellar companion (in blue) losing gas to the black hole Cygnus X-1. This interaction between the companion and the black hole is what produces radiation. That radiation is what lets astronomers study the black hole. Image via International Centre for Radio Astronomy Research.

The conclusions of the new study come from new observations of the distance to the black hole. An international team of astronomers calculated the new values after time spent observing Cyg X-1 with the Very Long Baseline Array. The Very Long Baseline Array is a radio telescope made up of 10 different dishes spread across half the globe: from Hawaii, to locations scattered over the continental United States, to the U.S. Virgin Islands. The telescope uses not only its wide-spread dishes but the orbit of Earth around the sun, as shown in the video below. This telescope array can record time-lapse movies of supercharged gas speeding away from black holes.

The astronomers used measurements taken of Cyg X-1 and its environs from 2011 and compared them to recent observations taken over a six-day period. By noting how much the black hole and associated gas and dust moved compared to background stars, they could get an estimate of how far away the black hole is.

The new measurements are challenging what astronomers know about this class of black holes. Ilya Mandel of Monash University and the ARC Centre of Excellence in Gravitational Wave Discovery explained:

Stars lose mass to their surrounding environment through stellar winds that blow away from their surface. But to make a black hole this heavy, we need to dial down the amount of mass that bright stars lose during their lifetimes. The black hole in the Cygnus X-1 system began life as a star approximately 60 times the mass of the sun and collapsed tens of thousands of years ago. Incredibly, it’s orbiting its companion star – a supergiant – every 5 1/2 days at just 1/5 of the distance between the Earth and the sun. These new observations tell us the black hole is more than 20 times the mass of our sun, a 50% increase on previous estimates.

These extremes have an implication for the spin rate of the black hole as well. Cygnus X-1 is now believed to rotate close to the speed of light and faster than any other black hole found to date.

An optical image from the Digitized Sky Survey shows the black hole Cygnus X-1 region outlined in a red box. Cygnus X-1 is located near large active regions of star formation in the Milky Way, as seen in this image that spans some 700 light-years. Image via NASA/ Digitized Sky Survey.

Bottom line: New measurements of the distance to the black hole known as Cygnus X-1 reveal it to be farther away and therefore more massive than previously believed.

Delving Into The Mystery Of Black Hole Jets

The concept of a black hole jet isn’t a new one, but we still have a lot to learn about the mixture of particles found in the vicinity of them. Through the use of ESA’s XMM-Newton Observatory, astronomers have been taking a look at a black hole in our galaxy and found some surprising results.

As we know, stellar mass black holes take on materials from nearby stars. Matter from these companion stars is pulled away from the parent body toward the black hole and radiates a temperture so intense that it emits X-rays. However, a black hole doesn’t always ingest everything that comes its way. Sometimes they reject small portions of this incoming mass, pushing it away in the form of a set of powerful jets. These jets also feed the surroundings, releasing both mass and energy… robbing the black hole of fuel.

Through the study of jet composition, researchers are able to better determine what gets taken into a black hole and what doesn’t. Through observations taken at the radio wavelength of the electromagnetic spectrum, we have seen electrons crusing along at nearly the speed of light. However, it hasn’t been clearly determined whether the negative charge of the electrons is complemented by their anti-particles, positrons, or rather by heavier positively-charged particles in the jets, like protons or atomic nuclei.” With XMM-Newton’s power behind them, astronomers have had the opportunity to examine a black hole binary system called 4U1630–47 – a candidate known to have unexpected outbursts of X-rays for segments of time which last between months and years.

“In our observations, we found signs of highly ionised nuclei of two heavy elements, iron and nickel,” says María Díaz Trigo of the European Southern Observatory in Munich, Germany, lead author of the paper published in the journal Nature. “The discovery came as a surprise – and a good one, since it shows beyond doubt that the composition of black hole jets is much richer than just electrons.”

During September 2012, a team of astronomers headed up by Dr. Díaz Trigo and collaborators, observed 4U1630–47 with XMM-Newton. They also backed up their observations with near-simultaneous radio observations taken from the Australia Telescope Compact Array. Even though the studies were done close to each other – within just a couple of weeks – the results couldn’t have been more different.

According to Trigo’s team, the initial set of observations picked up X-ray signatures from the accretion disc, but there was no activity in the radio band. This is an indicator that the jets weren’t active at that time. However, in the second set of observations, there was activity in both X-ray and radio… the jets had turned back on! While examining the X-ray data from the second set, they also found iron nuclei in motion. These particles were moving both toward and away from XMM-Newton – proof the ions were part of twin jets aimed in opposite directions. However, that’s not all. There was also evidence of nickel nuclei pointing toward the observatory.

“From these ‘fingerprints’ of iron and nickel, we could show that the speed of the jet is very high, about two-thirds of the speed of light,” says co-author James Miller-Jones from the Curtin University node of the International Centre for Radio Astronomy Research in Perth, Australia.

“Moreover, the presence of heavy atomic nuclei in black hole jets means that mass and energy are being carried away from the black hole in much larger amounts than we previously thought, which may have an impact on the mechanism and rate by which the black hole accretes matter,” adds co-author Simone Migliari from the University of Barcelona, Spain.

Astounding new findings? Well… yeah. For a typical stellar-mass black hole, this is the first time that heavy nuclei has been detected within the jets. As of the present, there is only “one other X-ray binary that shows similar signatures from atomic nuclei in its jets – a source known as SS 433. This black hole system, however, is characterised by an unusually high accretion rate, which makes it difficult to compare its properties to those of more ordinary black holes.” Through these new observations of 4U1630–47, astronomers will be able to fill in information gaps about what causes jets to occur in black hole accretion disks and what drives them.

“While we now know a great deal about black holes and what happens around them, the formation of jets is still a big puzzle, so this observation is a major step forward in understanding this fascinating phenomenon,” says Norbert Schartel, ESA’s XMM-Newton Project Scientist.

Does A Star Gain Mass In Order To Make A Black Hole?

If a black hole is the remnants of an extremely large collapsed star, how does gravity of the dead star increase to create the black hole? Light could obviously escape the gravity of the star and the black hole is made from the dead star but, once the black hole is created, light can no longer escape. Does the mass somehow increase at the death of the star?

Your standard black hole is indeed the remnants of an extremely large, collapsed star, with the remnant sitting somewhere between 5-20 times more massive than our own sun. However, if we let nature produce a black hole, the black hole that is produced at the end of a supernova explosion is actually significantly less massive than the star that it once was.

Part of the drop in mass between star and black hole comes in the years before the supernova, when the star typically sheds a sizable fraction of its mass. Since the star has expanded so much as part of the red giant phase, it only has a loose gravitational grasp on the outer layers of its atmosphere, and they are easily pushed away from the star by the star’s stellar wind. Our sun has a stellar wind as well, and it’s one of the reasons Mars is still losing its atmosphere to space - it’s also the reason Earth’s magnetosphere is such a nice feature of our planet we’re protected from this kind of atmospheric blasting by the sun. However, the Sun’s stellar wind is dragging many fewer particles along with it, compared to a red giant star, so the sun’s mass loss is much less than it would be if it were a red giant.

The star has pre-emptively lost some of the mass it contained before it became a red giant, but there’s also the supernova explosion itself to consider. A good chunk of the material that was left within the star goes blasting outward, fast and hot enough to barrel into any gas and dust nearby and produce X-rays. It’s really only the very core of the star that stays put, and can be compressed into the black hole.

If the mass of the star is actually only partially transformed into a black hole, then I’ve actually made the paradox in your question worse. How is the gravitational pull of a much bigger star (which light can escape from) so much weaker than a black hole made of only a fraction of the star (which light can’t escape from)?

The gravitational pull from a large object on a small one, at any point in space, is only determined by the mass of the heavy object, the mass of the smaller object, and the distance between the centers of the two objects. So, by this logic, if you were a cosmic wizard and replaced the sun with a black hole of equal mass, none of these parameters have changed for the planets. The planets haven’t changed their mass, or their distance from the center of the solar system where the sun used to be, and if the sun and the black hole are the same mass, then the whole system is gravitationally identical.

Obviously, there are some cosmetic differences between the black hole and the star in this scenario, but gravitationally speaking, differences only arise when you start to get very close to the objects. At the surface of our sun, which is where light escapes from the star and streams out towards the rest of the Universe, we are still 432,700 miles (696,000 kilometres) away from the center of the sun. A black hole, on the other hand, is a much denser object, so you can get far closer to its center while still having the entire mass of the black hole to contend with. It’s this density that makes the difference between light being able to escape or not.

For our magical swap scenario, you would have to get within 1.83 miles (2.95 kilometers) of the coordinates marking the very center of the Sun (or where it used to be) before you would cross the event horizon, where light would no longer be able to escape. Within that sphere, 3.66 miles from edge to edge, is the entire mass of our current sun, packed into a single pinprick’s worth of space, instead of filling 432,700 miles of space.

It’s the same scenario with the black hole produced at the end of a supernova the black hole hasn’t grown in mass, or expanded its gravitational reach- it’s simply much more dense, so you (or light) can get much closer to the center of the black hole, while still being pulled on by the full mass of the black hole. It’s this combination of proximity and mass concentration that produces the gravitational extremes we’ve come to associate with black holes!

“Heaviest Black Hole Collision” Detected by Gravitational Waves Might Actually Be a Boson Star Merger

An international team of scientists led by the Galician Institute of High Energy Physics and the University of Aveiro, including an undergraduate from the Department of Physics at The Chinese University of Hong Kong (CUHK), has proposed the collision of two exotic compact objects known as boson stars as an alternative explanation for the origin of the gravitational wave signal GW190521. The hypothetical stars are among the simplest exotic compact objects proposed and constitute well founded dark matter candidates. Within this interpretation, the team is able to estimate the mass of a new particle constituent of these stars, an ultra-light boson with a mass billions of times smaller than that of the electron. Their analysis has been published in the journal Physical Review Letters on February 24, 2021.

The team is co-led by Dr. Juan Calderón Bustillo, a former professor from the Department of Physics at CUHK and now “La Caixa Junior Leader – Marie Curie Fellow”, at the Galician Institute of High Energy Physics, and Dr. Nicolás Sanchis-Gual, a postdoctoral researcher at the University of Aveiro and at the Instituto Superior Técnico (University of Lisbon). Other collaborators came from the University of Valencia, the University of Aveiro and Monash University. Samson Hin Wai Leong, a second-year undergraduate at CUHK, also participated.

Gravitational waves are ripples in the fabric of spacetime that travel at the speed of light. Predicted in Einstein’s General Theory of Relativity, they originate in the most violent events of the Universe, carrying information about their sources. Since 2015, the advanced detectors of the Laser Interferometer Gravitational Wave Observatory (LIGO) and Virgo have observed around 50 gravitational wave signals originated in the coalescence and merger of two of the most mysterious entities in the Universe — black holes and neutron stars.

In September 2020, LVC, the joint body of the LIGO Scientific Collaboration and the Virgo Collaboration, announced the detection of the gravitational wave signal GW190521. According to the LVC analysis, in which the CUHK group led by Professor Tjonnie Li, Associate Professor of the Department of Physics at CUHK was deeply involved, the signal was consistent with the collision of two black holes of 85 and 66 times the mass of the Sun, which produced a final 142 solar mass black hole. The latter was the first member ever found of a new black hole family — intermediate-mass black holes. According to Professor Tjonnie Li, this discovery was of paramount importance because such black holes had been long considered the missing link between the stellar-mass black holes that form from the collapse of stars, and the supermassive black holes that hide in the center of almost every galaxy.

Despite its significance, the observation of GW190521 poses an enormous challenge to the current understanding of stellar evolution, because one of the black holes merged has a “forbidden” size. The alternative explanation proposed by the team brings a new direction for the study. Dr. Nicolás Sanchis-Gual explained, “Boson stars are objects almost as compact as black holes but, unlike them, they do not have a ‘no return’ surface or event horizon. When they collide, they form a boson star that can become unstable, eventually collapsing to a black hole, and producing a signal consistent with what LVC observed last year. Unlike regular stars, which are made of what we commonly know as matter, boson stars are made up of ultra-light bosons. These bosons are one of the most appealing candidates for constituting dark matter forming around 27% of the Universe.”

The team compared the GW190521 signal to computer simulations of boson star mergers and found that these actually explain the data slightly better than the analysis conducted by LVC. The result implies that the source would have different properties than stated earlier. Dr. Juan Calderón Bustillo said, “First, we would not be talking about colliding black holes anymore, which eliminates the issue of dealing with a forbidden black hole. Second, because boson star mergers are much weaker, we infer a much closer distance than the one estimated by LVC. This leads to a much larger mass for the final black hole, of about 250 solar masses, so the fact that we have witnessed the formation of an intermediate-mass black hole remains true.”

Professor Toni Font, from the University of Valencia and one of the co-authors, explained that even though the analysis tends to favour “by design” the merging black holes hypothesis, a boson star merger is actually slightly preferred by the data, although in a non-conclusive way. Despite the computational framework of the current boson star simulations being still fairly limited and subject to major improvements, the team will further develop a more evolved model and study similar gravitational wave observations under the boson star merger assumption.

According to another co-author, Professor Carlos Herdeiro from the University of Aveiro, the finding not only involves the first observation of boson stars, but also that of their building block, a new particle known as the ultra-light boson. Such ultra-light bosons have been proposed as the constituents of what we know as dark matter. Moreover, the team can actually measure the mass of this putative new dark matter particle and a value of zero is discarded with high confidence. If it is confirmed by the subsequent analysis of GW190521 and other gravitational wave observations, the result would provide the first observational evidence for a long sought dark matter candidate.

Samson Hin Wai Leong, a student who joined the summer undergraduate research internship programme of CUHK added, “I worked with Professor Calderón Bustillo on the design of the software of this project, which successfully speeded up the calculations of the study, and eventually we were able to release our results immediately after LVC published their analysis. It is thrilling to work at the frontier of physics with the multicultural team and think about seeking a ‘darker’ origin of the ripples in spacetime, at the same time proving the existence of a dark matter particle.”

Reference: “GW190521 as a Merger of Proca Stars: A Potential New Vector Boson of 8.7×10 −13 eV” by Juan Calderón Bustillo, Nicolas Sanchis-Gual, Alejandro Torres-Forné, José A. Font, Avi Vajpeyi, Rory Smith, Carlos Herdeiro, Eugen Radu and Samson H. W. Leong, 24 February 2021, Physical Review Letters.
DOI: 10.1103/PhysRevLett.126.081101

Supermassive black holes control star formation in large galaxies

Young galaxies blaze with bright new stars forming at a rapid rate, but star formation eventually shuts down as a galaxy evolves. A new study, published January 1, 2018, in Nature, shows that the mass of the black hole in the center of the galaxy determines how soon this "quenching" of star formation occurs.

Every massive galaxy has a central supermassive black hole, more than a million times more massive than the sun, revealing its presence through its gravitational effects on the galaxy's stars and sometimes powering the energetic radiation from an active galactic nucleus (AGN). The energy pouring into a galaxy from an active galactic nucleus is thought to turn off star formation by heating and dispelling the gas that would otherwise condense into stars as it cooled.

This idea has been around for decades, and astrophysicists have found that simulations of galaxy evolution must incorporate feedback from the black hole in order to reproduce the observed properties of galaxies. But observational evidence of a connection between supermassive black holes and star formation has been lacking, until now.

"We've been dialing in the feedback to make the simulations work out, without really knowing how it happens," said Jean Brodie, professor of astronomy and astrophysics at UC Santa Cruz and a coauthor of the paper. "This is the first direct observational evidence where we can see the effect of the black hole on the star formation history of the galaxy."

The new results reveal a continuous interplay between black hole activity and star formation throughout a galaxy's life, affecting every generation of stars formed as the galaxy evolves.

Led by first author Ignacio Martín-Navarro, a postdoctoral researcher at UC Santa Cruz, the study focused on massive galaxies for which the mass of the central black hole had been measured in previous studies by analyzing the motions of stars near the center of the galaxy. To determine the star formation histories of the galaxies, Martín-Navarro analyzed detailed spectra of their light obtained by the Hobby-Eberly Telescope Massive Galaxy Survey.

Spectroscopy enables astronomers to separate and measure the different wavelengths of light from an object. Martín-Navarro used computational techniques to analyze the spectrum of each galaxy and recover its star formation history by finding the best combination of stellar populations to fit the spectroscopic data. "It tells you how much light is coming from stellar populations of different ages," he said.

When he compared the star formation histories of galaxies with black holes of different masses, he found striking differences. These differences only correlated with black hole mass and not with galactic morphology, size, or other properties.

"For galaxies with the same mass of stars but different black hole mass in the center, those galaxies with bigger black holes were quenched earlier and faster than those with smaller black holes. So star formation lasted longer in those galaxies with smaller central black holes," Martín-Navarro said.

Other researchers have looked for correlations between star formation and the luminosity of active galactic nuclei, without success. Martín-Navarro said that may be because the time scales are so different, with star formation occurring over hundreds of millions of years, while outbursts from active galactic nuclei occur over shorter periods of time.

A supermassive black hole is only luminous when it is actively gobbling up matter from its host galaxy's inner regions. Active galactic nuclei are highly variable and their properties depend on the size of the black hole, the rate of accretion of new material falling onto the black hole, and other factors.

"We used black hole mass as a proxy for the energy put into the galaxy by the AGN, because accretion onto more massive black holes leads to more energetic feedback from active galactic nuclei, which would quench star formation faster," Martín-Navarro explained.

The precise nature of the feedback from the black hole that quenches star formation remains uncertain, according to coauthor Aaron Romanowsky, an astronomer at San Jose State University and UC Observatories.

"There are different ways a black hole can put energy out into the galaxy, and theorists have all kinds of ideas about how quenching happens, but there's more work to be done to fit these new observations into the models," Romanowsky said.

Scientists find ‘monster’ black hole so big they didn’t think it was possible

Before now, scientists did not think it was possible for a stellar black hole to have a mass larger than 20 times that of the sun, an approximation based on their understanding of the way stars evolve and die in the Milky Way.

But that assumption was metaphorically crushed in the gravity of a “monster” black hole that a group of Chinese-led international scientists discovered inside our own galaxy. The hole has a mass 70 times that of the sun, researchers said in their study published in the journal Nature.

“No one has ever seen a 70-solar-mass stellar black hole anywhere,” Joel Bregman, one of the study authors and a professor of astronomy at the University of Michigan, said in an interview. “This is the first.”

Black holes form when a star runs out of fuel and collapses on itself, creating a strong gravitational pull that prevents anything — even light — from escaping. In the process, those stars lose much of their mass, producing black holes that reflect their diminished size.

The newly discovered black hole, named LB-1 by the team of researchers who published the study, is located 15,000 light-years from earth, according to a news release. And it is huge.

“Black holes of such mass should not even exist in our Galaxy, according to most of the current models of stellar evolution,” Liu Jifeng, a professor at the National Astronomical Observatory of China, said in a news release from the Chinese Academy of Sciences. “… Now theorists will have to take up the challenge of explaining its formation.”

Previously, about two dozen black holes have been discovered and studied in our galaxy using X-ray technology that detects a bright light emitted when a black hole eats a neighboring star. While successful, this process limited scientists’ ability to find more black holes because the vast majority of them in our galaxy are not actively consuming other stars.

LB-1 was discovered by China’s Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST), which has provided scientists with a new way to find the estimated 100 million black holes in the Milky Way. LAMOST enables researchers to detect black holes by first tracking stars that are orbiting something invisible to more than the naked eye, such as a black hole.

When LAMOST identified a star orbiting LB-1, the team next used the world’s largest telescopes — from the United States and Spain — to take a closer look at the system. The results, according to the news release, were “nothing short of fantastic.”

There are two kinds of black holes. Stellar black holes, like LB-1, are made from the evolution and death of stars, which rarely exceed 150 times the mass of the sun when they are born, Bregman said. There are also supermassive black holes, which almost always live in the center of galaxies and range from a million to a few billion times the mass of the sun.

Astronomers Measure Mass of Supermassive Black Hole in NGC 1097

Astronomers using the Atacama Large Millimeter/submillimeter Array, or ALMA, a network of several dozen radio dishes located in the high-elevation desert of northern Chile, have measured the mass of the supermassive black hole at the center of the barred spiral galaxy NGC 1097.

In this image, the larger-scale structure of NGC 1097 is easily visible. Image credit: ESO / R. Gendler.

NGC 1097 lies in the southern constellation Fornax at a distance of only 45 million light-years. Lurking at the very center of this face-on galaxy, a supermassive black hole is gradually sucking in the matter around it. The area immediately around the black hole shines powerfully with radiation coming from the material falling in.

The distinctive ring around the NGC 1097’s black hole is bursting with new star formation. An inflow of material toward the central bar of the galaxy is causing the ring to light up with new stars. The ring is around 5,000 light-years across, although the spiral arms of the galaxy extend tens of thousands of light-years beyond it.

A team of astronomers led by Dr Kyoko Onishi of the Graduate University for Advanced Studies (SOKENDAI) in Japan determined that NGC 1097 harbors a black hole 140 million times more massive than our Sun. In comparison, the black hole at the center of the Milky Way is a lightweight, with a mass of just a few million times that of our Sun.

This composite image shows the barred spiral galaxy NGC 1097. By studying the motion of two molecules, astronomers were able to determine that the supermassive black hole at the center of this galaxy has a mass 140 million times greater than our Sun. Image credit: ALMA / NRAO / ESO / NAOJ / K. Onishi / NASA / ESA / Hubble Space Telescope / E. Sturdivant / AUI / NSF.

First, Dr Onishi and co-authors measured the distribution and motion of two molecules – hydrogen cyanide and formylium – near the central region of NGC 1097.

They then compared the ALMA observations to various mathematical models, each corresponding to a different mass of the supermassive black hole.

The ‘best fit’ for these observations corresponded to a black hole weighing in at about 140 million solar masses. The results are published in the

“This is the first use of ALMA to make such a measurement for a spiral or barred spiral galaxy,” said Dr Kartik Sheth of the National Radio Astronomy Observatory in Charlottesville, Va., who is a co-author of paper about the results available online in the Astrophysical Journal.

“When you look at the exquisitely detailed observations from ALMA, it’s startling how well they fit in with these well tested models.”

“It’s exciting to think that we can now apply this same technique to other similar galaxies and better understand how these unbelievably massive objects affect their host galaxies.”

“Future observations with ALMA will continue to refine this technique and expand its applications to other spiral-type galaxies,” the astronomers said.

K. Onishi et al. 2015. A Measurement of the Black Hole Mass in NGC 1097 Using ALMA. ApJ 806, 39 doi: 10.1088/0004-637X/806/1/39

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