SMBH Archives

February 22, 2018 by Matt Williams

Maybe There’s no Connection Between Supermassive Black Holes and Their Host Galaxies?

Artist's impression of an ionized gas outflow (green) driven by the central supermassive black hole does not affect the star formation of its host galaxy. This situation may occur if the ionized gas is outflowing perpendicularly to the molecular gas. Credit: ALMA (ESO/NAOJ/NRAO)

For decades, astrophysicists have puzzled over the relationship between Supermassive Black Holes (SMBHs) and their respective galaxies. Since the 1970s, it has been understood the majority of massive galaxies have an SMBH at their center, and that these are surrounded by rotating tori of gas and dust. The presence of these black holes and tori are what cause massive galaxies to have an Active Galactic Nucleus (AGN).

However, a recent study conducted by an international team of researchers revealed a startling conclusion when studying this relationship. Using the Atacama Large Millimeter/submillimeter Array (ALMA) to observe an active galaxy with a strong ionized gas outflow from the galactic center, the team obtained results that could indicate that there is no relationship between a an SMBH and its host galaxy.

The study, titled “No sign of strong molecular gas outflow in an infrared-bright dust-obscured galaxy with strong ionized-gas outflow“, recently appeared in the Astrophysical Journal. The study was led by Yoshiki Toba of the Academia Sinica Institute of Astronomy and Astrophysics in Taiwan and included members from Ehime University, Kogakuin University, and the National Astronomical Observatory of Japan, The Graduate University for Advanced Studies (SOKENDAI), and Johns Hopkins University.

*Images from the Sloan Digital Sky Survey (SDSS) (left), and mid-infrared image from WISE (right), respectively. Credit: Sloan Digital Sky Survey/NASA/JPLCaltech*

The question of how SMBHs have affected galactic evolution remains one of the greatest unresolved questions in modern astronomy. Among astrophysicists, it is something of a foregone conclusion that SMBHs have a significant impact on the formation and evolution of galaxies. According to this accepted notion, SMBHs significantly influence the molecular gas in galaxies, which has a profound effect on star formation.

Basically, this theory holds that larger galaxies accumulate more gas, thus resulting in more stars and a more massive central black hole. At the same time, there is a feedback mechanism, where growing black holes accrete more matter on themselves. This results in them sending out a tremendous amount of energy in the form of radiation and particle jets, which is believed to curtail star formation in their vicinity.

However, when observing an infrared (IR)-bright dust-obscured galaxy (DOG) – WISE1029+0501 – Yoshiki and his colleagues obtained results that contradicted this notion. After conducting a detailed analysis using ALMA, the team found that there were no signs of significant molecular gas outflow coming from WISE1029+0501. They also found that star-forming activity in the galaxy was neither more intense or suppressed.

This indicates that a strong ionized gas outflow coming from the SMBH in WISE1029+0501 did not significantly affect the surrounding molecular gas or star formation. As Dr. Yoshiki Toba explained, this result:

“[H]as made the co-evolution of galaxies and supermassive black holes more puzzling. The next step is looking into more data of this kind of galaxies. That is crucial for understanding the full picture of the formation and evolution of galaxies and supermassive black holes”.

*Emission from Carbon Monoxide (Left) and Cold Dust (Right) in WISE1029 Observed by ALMA (image). Credit: ALMA (ESO/NAOJ/NRAO), Toba et al.*

This not only flies in the face of conventional wisdom, but also in the face of recent studies that showed a tight correlation between the mass of central black holes and those of their host galaxies. This correlation suggests that supermassive black holes and their host galaxies evolved together over the course of the past 13.8 billion years and closely interacted as they grew.

In this respect, this latest study has only deepened the mystery of the relationship between SMBHs and their galaxies. As Tohru Nagao, a Professor at Ehime University and a co-author on the study, indicated:

“[W]e astronomers do not understand the real relation between the activity of supermassive black holes and star formation in galaxies. Therefore, many astronomers including us are eager to observe the real scene of the interaction between the nuclear outflow and the star-forming activities, for revealing the mystery of the co-evolution.”

The team selected WISE1029+0501 for their study because astronomers believe that DOGs harbor actively growing SMBHs in their nuclei. In particular, WISE1029+0501 is an extreme example of galaxies where outflowing gas is being ionized by the intense radiation from its SMBH. As such, researchers have been highly motivated to see what happens to this galaxy’s molecular gas.

The study was made possible thanks to ALMA’s sensitivity, which is excellent when it comes to investigating the properties of molecular gas and star-forming activity in galaxies. In fact, multiple studies have been conducted in recent years that have relied on ALMA to investigate the gas properties and SMBHs of distant galaxies.

And while the results of this study contradict widely-held theories about galactic evolution, Yoshiki and his colleagues are excited about what this study could reveal. In the end, it may be that radiation from a SMBH does not always affect the molecular gas and star formation of its host galaxy.

“[U]nderstanding such co-evolution is crucial for astronomy,” said Yoshiki. “By collecting statistical data of this kind of galaxies and continuing in more follow-up observations using ALMA, we hope to reveal the truth.”

Further Reading: ALMA Observatory, Astrophysical Journal

February 20, 2018February 17, 2023 by Matt Williams

Astronomers Observe the Rotating Accretion Disk Around the Supermassive Black Hole in M77

Artist’s impression of the dusty gaseous torus around an active supermassive black hole. ALMA revealed the rotation of the torus very clearly for the first time. Credit: ALMA (ESO/NAOJ/NRAO)

During the 1970s, scientists confirmed that radio emissions coming from the center of our galaxy were due to the presence of a Supermassive Black Hole (SMBH). Located about 26,000 light-years from Earth between the Sagittarius and Scorpius constellation, this feature came to be known as Sagittarius A*. Since that time, astronomers have come to understand that most massive galaxies have an SMBH at their center.

What’s more, astronomers have come to learn that black holes in these galaxies are surrounded by massive rotating toruses of dust and gas, which is what accounts for the energy they put out. However, it was only recently that a team of astronomers, using the the Atacama Large Millimeter/submillimeter Array (ALMA), were able to capture an image of the rotating dusty gas torus around the supermassive black hole of M77.

The study which details their findings recently appeared in the Astronomical Journal Letters under the title “ALMA Reveals an Inhomogeneous Compact Rotating Dense Molecular Torus at the NGC 1068 Nucleus“. The study was conducted by a team of Japanese researchers from the National Astronomical Observatory of Japan – led by Masatoshi Imanishi – with assistance from Kagoshima University.

The central region of the spiral galaxy M77. The NASA/ESA Hubble Space Telescope imaged the distribution of stars. ALMA revealed the distribution of gas in the very center of the galaxy. Credit: ALMA (ESO/NAOJ/NRAO)/Imanishi et al./NASA/ESA Hubble Space Telescope and A. van der Hoeven

Like most massive galaxies, M77 has an Active Galactic Nucleus (AGN), where dust and gas are being accreted onto its SMBH, leading to higher-than-normal luminosity. For some time, astronomers have puzzled over the curious relationship that exists between SMBHs and galaxies. Whereas more massive galaxies have larger SMBHs, host galaxies are still 10 billion times larger than their central black hole.

This naturally raises questions about how two objects of vastly different scales could directly affect each other. As a result, astronomers have sought to study AGN is order to determine how galaxies and black holes co-evolve. For the sake of their study, the team conducted high-resolution observations of the central region of M77, a barred spiral galaxy located about 47 million light years from Earth.

Using ALMA, the team imaged the area around M77’s center and were able to resolve a compact gaseous structure with a radius of 20 light-years. As expected, the team found that the compact structure was rotating around the galaxies central black hole. As Masatoshi Imanishi explained in an ALMA press release:

“To interpret various observational features of AGNs, astronomers have assumed rotating donut-like structures of dusty gas around active supermassive black holes. This is called the ‘unified model’ of AGN. However, the dusty gaseous donut is very tiny in appearance. With the high resolution of ALMA, now we can directly see the structure.”

*Motion of gas around the supermassive black hole in the center of M77. The gas moving toward us is shown in blue and that moving away from us is in red. Credit: ALMA (ESO/NAOJ/NRAO), Imanishi et al.*

In the past, astronomers have observed the center of M77, but no one has been able to resolve the rotating torus at its center until now. This was made possible thanks to the superior resolution of ALMA, as well as the selection of molecular emissions lines. These emissions lines include hydrogen cyanide (HCN) and formyl ions (HCO+), which emit microwaves only in dense gas, and carbon monoxide – which emits microwaves under a variety of conditions.

The observations of these emission lines confirmed another prediction made by the team, which was that the torus would be very dense. “Previous observations have revealed the east-west elongation of the dusty gaseous torus,” said Imanishi. “The dynamics revealed from our ALMA data agrees exactly with the expected rotational orientation of the torus.”

However, their observations also indicated that the distribution of gas around an SMBH is more complicated that what a simple unified model suggests. According to this model, the rotation of the torus would follow the gravity of the black hole; but what Imanishi and his team found indicated that gas and dust in the torus also exhibit signs of highly random motion.

These could be an indication that the AGN at the center of M77 had a violent history, which could include merging with a small galaxy in the past. In short, the team’s observations indicate that galactic mergers may have a significant impact on how AGNs form and behave. In this respect, their observations of M77s torus are already providing clues as to the galaxy’s history and evolution.

*NASA’s Spitzer Space Telescope captured this stunning infrared image of the center of the Milky Way Galaxy, where the black hole Sagittarius A resides. Credit: NASA/JPL-Caltech*

The study of SMBHs, while intensive, is also very challenging. On the one hand, the closest SMBH (Sagittarius A*) is relatively quiet, with only a small amount of gas accreting onto it. At the same time, it is located at the center of our galaxy, where it is obscured by intervening dust, gas and stars. As such, astronomers are forced to look to other galaxies to study how SMBHs and their galaxies co-exist.

And thanks to decades of study and improvements in instrumentation, scientists are beginning to get a clear glimpse of these mysterious regions for the first time. By being able to study them in detail, astronomers are also gaining valuable insight into how such massive black holes and their ringed structures could coexist with their galaxies over time.

Further Reading: ALMA, arXiv

February 2, 2018 by Matt Williams

Outflows From Black Holes are Creating New Molecules Where There Should Only be Destruction

During the 1960s, scientists discovered a massive radio source (known as Sagittarius A*) at the center of the Milky Way, which was later revealed to be a Supermassive Black Holes (SMBH). Since then, they have learned that these SMBHs reside at the center of most massive galaxies. The presence of these black holes is also what allows the centers of these galaxies to have a higher than normal luminosity – aka. Active Galactic Nuclei (AGNs).

In the past few years, astronomers have also observed fast molecular outflows emanating from AGNs which left them puzzled. For one, it was a mystery how any particles could survive the heat and energy of a black hole’s outflow. But according to a new study produced by researchers from Northwestern University, these molecules were actually born within the winds themselves. This theory may help explain how stars form in extreme environments.

The study recently appeared in The Monthly Notices of the Royal Astronomical Society under the title “The origin of fast molecular outflows in quasars: molecule formation in AGN-driven galactic winds.” The study was conducted by Lindheimer post-doctoral fellow Alexander J Richings and assistant professor Claude-André Faucher-Giguère from Northwestern University’s Center for Interdisciplinary Research and Exploration in Astrophysics (CIERA).

*Artist’s impression of a black hole’s wind sweeping away galactic gas. Credit: ESA*

For the sake of their study, Richings developed the first-ever computer code capable of modeling the detailed chemical processes in interstellar gas which are accelerated by a growing SMBH’s radiation. Meanwhile, Claude-André Faucher-Giguère contributed his expertise, having spent his career studying the formation and evolution of galaxies. As Richings explained in a Northwestern press release:

“When a black hole wind sweeps up gas from its host galaxy, the gas is heated to high temperatures, which destroy any existing molecules. By modeling the molecular chemistry in computer simulations of black hole winds, we found that this swept-up gas can subsequently cool and form new molecules.”

The existence of energetic outflows form SMBHs was first confirmed in 2015, when researchers used the ESA’s Herschel Space Observatory and data from the Japanese/US Suzaku satellite to observe the AGN of a galaxy known as IRAS F11119+3257. Such outflows, they determined, are responsible for draining galaxies of their interstellar gas, which has an arresting effect on the formation of new stars and can lead to “red and dead” elliptical galaxies.

This was followed-up in 2017 with observations that indicated that rapidly moving new stars formed in these outflows, something that astronomers previously thought to be impossible because of the extreme conditions present within them. By theorizing that these particles are actually the product of black hole winds, Richings and Faucher-Giguère have managed to address questions raised by these previous observations.

Artist's concept of Sagittarius A, the supermassive black hole at the center of our galaxy. Credit: NASA/JPL — *Artist’s concept of Sagittarius A, the supermassive black hole at the center of our galaxy. Credit: NASA/JPL*

Essentially, their theory helps explain predictions made in the past, which appeared contradictory at first glance. On the one hand, it upholds the prediction that black hole winds destroy molecules they collide with. However, it also predicts that new molecules are formed within these winds – including hydrogen, carbon monoxide and water – which can give birth to new stars. As Faucher-Giguère explained:

“This is the first time that the molecule formation process has been simulated in full detail, and in our view, it is a very compelling explanation for the observation that molecules are ubiquitous in supermassive black hole winds, which has been one of the major outstanding problems in the field.”

Richings and Faucher-Giguère look forward to the day when their theory can be confirmed by next-generation missions. They predict that new molecules formed by black hole outflows would be brighter in the infrared wavelength than pre-existing molecules. So when the James Webb Space Telescope takes to space in the Spring of 2019, it will be able to map these outflows in detail using its advance IR instruments.

One of the most exciting things about the current era of astronomy is the way new discoveries are shedding light on decades-old mysteries. But when these discoveries lead to theories that offer symmetry to what were once thought to be incongruous pieces of evidence, that’s when things get especially exciting. Basically, it lets us know that we are moving closer to a greater understanding of our Universe!

Further Reading: Northwestern University, MNRAS

September 8, 2017September 8, 2017 by Matt Williams

Chinese Astronomers Spot Two New Hypervelocity Stars

An artist's conception of a hypervelocity star that has escaped the Milky Way. Credit: NASA

Most stars in our galaxy behave predictably, orbiting around the center of the Milky Way at speeds of about 100 km/s (62 mi/s). But some stars achieve velocities that are significantly greater, to the point that they are even able to escape the gravitational pull of the galaxy. These are known as hypervelocity stars (HVS), a rare type of star that is believed to be the result of interactions with a supermassive black hole (SMBH).

The existence of HVS is something that astronomers first theorized in the late 1980s, and only 20 have been identified so far. But thanks to a new study by a team of Chinese astronomers, two new hypervelocity stars have been added to that list. These stars, which have been designated LAMOST-HVS2 and LAMOST-HVS3, travel at speeds of up to 1,000 km/s (620 mi/s) and are thought to have originated in the center of our galaxy.

The study which describes the team’s findings, titled “Discovery of Two New Hypervelocity Stars From the LAMOST Spectroscopic Surveys“, recently appeared online. Led by Yang Huang of the South-Western Institute for Astronomy Research at Yunnan University in Kunming, China, the team relied on data from Large Sky Area Multi-Object Fibre Spectroscopic Telescope (LAMOST) to detect these two new hypervelocity stars.

*Footprint of the LAMOST pilot survey and the first three years’ general survey. Credit: LAMOST*

Astronomers estimates that only 1000 HVS exist within the Milky Way. Given that there are as many as 200 billion stars in our galaxy, that’s just 0.0000005 % of the galactic population. While these stars are thought to originate in the center of our galaxy – supposedly as a result of interaction with our SMBH, Sagittarius A* – they manage to travel pretty far, sometimes even escaping our galaxy altogether.

It is for this very reason that astronomers are so interested in HVS. Given their speed, and the vast distances they can cover, tracking them and creating a database of their movements could provide constraints on the shape of the dark matter halo of our galaxy. Hence why Dr. Huang and his colleagues began sifting through LAMOST data to find evidence of new HVS.

Located in Hebei Province, northwestern China, the LAMOST observatory is operated by the Chinese Academy of Sciences. Over the course of five years, this observatory conducted a spectroscopic survey of 10 million stars in the Milky Way, as well as millions of galaxies. In June of 2017, LAMOST released its third Data Release (DR3), which included spectra obtained during the pilot survey and its first three years’ of regular surveys.

Containing high-quality spectra of 4.66 million stars and the stellar parameters of an additional 3.17 million, DR3 is currently the largest public spectral set and stellar parameter catalogue in the world. Already, LAMOST data had been used to identify one hypervelocity star, a B1IV/V-type (main sequence blue subgiant/subdwarf) star that was 11 Solar Masses, 13490 times as bright as our Sun, and had an effective temperature of 26,000 K (25,727 °C; 46,340 °F).

*Artist’s impression of hypervelocity stars (HVSs) speeding through the Galaxy. Credit: ESA*

This HVS was designated LAMOST-HSV1, in honor of the observatory. After detecting two new HVSs in the LAMOST data, these stars were designated as LAMOST-HSV2 and LAMOST-HSV3. Interestingly enough, these newly-discovered HVSs are also main sequence blue subdwarfs – or a B2V-type and B7V-type star, respectively.

Whereas HSV2 is 7.3 Solar Masses, is 2399 times as luminous as our Sun, and has an effective temperature of 20,600 K (20,327 °C; 36,620 °F), HSV3 is 3.9 Solar Masses, is 309 times as luminous as the Sun, and has an effective temperature of 14,000 K (24,740 °C; 44,564 °F). The researchers also considered the possible origins of all three HVSs based on their spatial positions and flight times.

In addition to considering that they originated in the center of the Milky Way, they also consider alternate possibilities. As they state in their study:

“The three HVSs are all spatially associated with known young stellar structures near the GC, which supports a GC origin for them. However, two of them, i.e. LAMOST-HVS1 and 2, have life times smaller than their flight times, indicating that they do not have enough time to travel from the GC to the current positions unless they are blue stragglers (as in the case of HVS HE 0437-5439). The third one (LAMOST-HVS3) has a life time larger than its flight time and thus does not have this problem.

In other words, the origins of these stars is still something of a mystery. Beyond the idea that they were sped up by interacting with the SMBH at the center of our galaxy, the team also considered other possibilities that have suggested over the years.

*Artist’s impression of the ESA’s Gaia spacecraft, looking into the heart of the Milky Way Galaxy. Credit: ESA/ATG medialab/ESO/S. Brunier*

As they state in these study, these “include the tidal debris of an accreted and disrupted dwarf galaxy (Abadi et al. 2009), the surviving companion stars of Type Ia supernova (SNe Ia) explosions (Wang & Han 2009), the result of dynamical interaction between multiple stars (e.g, Gvaramadze et al. 2009), and the runaways ejected from the Large Magellanic Cloud (LMC), assuming that the latter hosts a MBH (Boubert et al. 2016).”

In the future, Huang and his colleagues indicate that their study will benefit from additional information that will be provided by the ESA’s Gaia mission, which they claim will shed additional light on how HVS behave and where they come from. As they state in their conclusions:

“The upcoming accurate proper motion measurements by Gaia should provide a direct constraint on their origins. Finally, we expect more HVSs to be discovered by the ongoing LAMOST spectroscopic surveys and thus to provide further constraint on the nature and ejection mechanisms of HVSs.”

Further Reading: arXiv

May 13, 2017November 5, 2018 by Matt Williams

Astronomers Find a Rogue Supermassive Black Hole, Kicked out by a Galactic Collision

Using data from Chandra and other telescopes, astronomers have found a possible "recoiling" black hole. Credit: NASA/CXC/M.Weiss

When galaxies collide, all manner of chaos can ensue. Though the process takes millions of years, the merger of two galaxies can result in Supermassive Black Holes (SMBHs, which reside at their centers) merging and becoming even larger. It can also result in stars being kicked out of their galaxies, sending them and even their systems of planets into space as “rogue stars“.

But according to a new study by an international team of astronomers, it appears that in some cases, SMBHs could also be ejected from their galaxies after a merger occurs. Using data from NASA’s Chandra X-ray Observatory and other telescopes, the team detected what could be a “renegade supermassive black hole” that is traveling away from its galaxy.

According to the team’s study – which appeared in the Astrophysical Journal under the title A Potential Recoiling Supermassive Black Hole, CXO J101527.2+625911 – the renegade black hole was detected at a distance of about 3.9 billion light years from Earth. It appears to have come from within an elliptical galaxy, and contains the equivalent of 160 million times the mass of our Sun.

*Hubble data showing the two bright points near the middle of the galaxy. Credit: NASA/CXC/NRAO/D.-C.Kim/STScI*

The team found this black hole while searching through thousands of galaxies for evidence of black holes that showed signs of being in motion. This consisted of sifting through data obtained by the Chandra X-ray telescope for bright X-ray sources – a common feature of rapidly-growing SMBHs – that were observed as part of the Sloan Digital Sky Survey (SDSS).

They then looked at Hubble data of all these X-ray bright galaxies to see if it would reveal two bright peaks at the center of any. These bright peaks would be a telltale indication that a pair of supermassive black holes were present, or that a recoiling black hole was moving away from the center of the galaxy. Last, the astronomers examined the SDSS spectral data, which shows how the amount of optical light varies with wavelength.

From all of this, the researchers invariably found what they considered to be a good candidate for a renegade black hole. With the help data from the SDSS and the Keck telescope in Hawaii, they determined that this candidate was located near, but visibly offset from, the center of its galaxy. They also noted that it had a velocity that was different from the galaxy – properties which suggested that it was moving on its own.

The image below, which was generated from Hubble data, shows the two bright points near the center of the galaxy. Whereas the one on the left was located within the center, the one on the right (the renegade SMBH) was located about 3,000 light years away from the center. Between the X-ray and optical data, all indications pointed towards it being a black hole that was kicked from its galaxy.

*The bright X-ray source detected with Chandra (left), and data obtained from the SDSS and the Keck telescope in Hawaii. Credit: NASA/CXC/NRAO/D.-C.Kim/STScI*

In terms of what could have caused this, the team ventured that the back hole might have “recoiled” when two smaller SMBHs collided and merged. This collision would have generated gravitational waves that could have then pushed the black hole out of the galaxy’s center. They further ventured that the black hole may have formed and been set in motion by the collision of two smaller black holes.

Another possible explanation is that two SMBHs are located in the center of this galaxy, but one of them is not producing detectable radiation – which would mean that it is growing too slowly. However, the researchers favor the explanation that what they observed was a renegade black hole, as it seems to be more consistent with the evidence. For example, their study showed signs that the host galaxy was experiencing some disturbance in its outer regions.

This is a possible indication that the merger between the two galaxies occurred in the relatively recent past. Since SMBH mergers are thought to occur when their host galaxies merge, this reservation favors the renegade black hole theory. In addition, the data showed that in this galaxy, stars were forming at a high rate. This agrees with computer simulations that predict that merging galaxies experience an enhanced rate of star formation.

But of course, additional researches is needed before any conclusions can be reached. In the meantime, the findings are likely to be of particular interest to astronomers. Not only does this study involve a truly rare phenomenon – a SMBH that is in motion, rather than resting at the center of a galaxy – but the unique properties involved could help us to learn more about these rare and enigmatic features.

*Detection of an unusually bright X-Ray flare from Sagittarius A*, a supermassive black hole in the center of the Milky Way galaxy. Credit: NASA/CXC/Stanford/I. Zhuravleva et al.*

For one, the study of SMBHs could reveal more about the rate and direction of spin of these enigmatic objects before they merge. From this, astronomers would be able to better predict when and where SMBHs are about to merge. Studying the speed of recoiling black holes could also reveal additional information about gravitational waves, which could unlock additional secrets about the nature of space time.

And above all, witnessing a renegade black hole is an opportunity to see some pretty amazing forces at work. Assuming the observations are correct, there will no doubt be follow-up surveys designed to see where the SMBH is traveling and what effect it is having on the surrounding cosmic environment.

Ever since the 1970s, scientists have been of the opinion that most galaxies have SMBHs at their center. In the years and decades that followed, research confirmed the presence of black holes not only at the center of our galaxy – Sagittarius A* – but at the center of all almost all known massive galaxies. Ranging in mass from the hundreds of thousands to billions of Solar masses, these objects exert a powerful influence on their respective galaxies.

Be sure to enjoy this video, courtesy of the Chandra X-Ray Observatory:

Further Reading: Chandra X-ray Observatory, arXiv

April 20, 2016May 5, 2016 by Matt Williams

Supermassive Black Holes In Distant Galaxies Are Mysteriously Aligned

A supermassive black hole has been found in an unusual spot: an isolated region of space where only small, dim galaxies reside. Image credit: NASA/JPL-Caltech — A team of astronomers from South Africa have noticed a series of supermassive black holes in distant galaxies that are all spinning in the same direction. Credit: NASA/JPL-Caltech

In 1974, astronomers detected a massive source of radio wave emissions coming from the center of our galaxy. Within a few decades time, it was concluded that the radio wave source corresponded to a particularly large, spinning black hole. Known as Sagittarius A, this particular black hole is so large that only the designation “supermassive” would do. Since its discovery, astronomers have come to conclude that supermassive black holes (SMBHs) lie at the center of almost all of the known massive galaxies.

But thanks to a recent radio imaging by a team of researchers from the University of Cape Town and University of the Western Cape, in South Africa, it has been further determined that in a region of the distant universe, the SMBHs are all spinning out radio jets in the same direction. This finding, which shows an alignment of the jets of galaxies over a large volume of space, is the first of its kind, and could tell us much about the early Universe.

Continue reading “Supermassive Black Holes In Distant Galaxies Are Mysteriously Aligned”

December 3, 2014September 19, 2017 by Matt Williams

10 Interesting Facts About the Milky Way

Viewed from above, we can now see that our gaze takes across the Perseus Arm (toward the constellation Cygnus), parts of the Sagittarius and Scutum-Centaurus arms (toward the constellations Scutum, Sagittarius and Ophiuchus) and across the central bar. Interstellar dust obscures much of the center of the galaxy. Credit: NASA et. all with additions by the author.

The Milky Way Galaxy is an immense and very interesting place. Not only does it measure some 120,000–180,000 light-years in diameter, it is home to planet Earth, the birthplace of humanity. Our Solar System resides roughly 27,000 light-years away from the Galactic Center, on the inner edge of one of the spiral-shaped concentrations of gas and dust particles called the Orion Arm.

But within these facts about the Milky Way lie some additional tidbits of information, all of which are sure to impress and inspire. Here are ten such facts, listed in no particular order:

1. It’s Warped:

For starters, the Milky Way is a disk about 120,000 light years across with a central bulge that has a diameter of 12,000 light years (see the Guide to Space article for more information). The disk is far from perfectly flat though, as can be seen in the picture below. In fact, it is warped in shape, a fact which astronomers attribute to the our galaxy’s two neighbors -the Large and Small Magellanic clouds.

These two dwarf galaxies — which are part of our “Local Group” of galaxies and may be orbiting the Milky Way — are believed to have been pulling on the dark matter in our galaxy like in a game of galactic tug-of-war. The tugging creates a sort of oscillating frequency that pulls on the galaxy’s hydrogen gas, of which the Milky Way has lots of (for more information, check out How the Milky Way got its Warp).

The Spiral Galaxy ESO 510-13 is warped similar to our own. Credit: NASA/Hubble Heritage Team (STScI / AURA), C. Conselice (U. Wisconsin / STScI/ NASA — *The warp of Spiral Galaxy ESO 510-13 is similar to that of our own. Credit: NASA/Hubble*

2. It Has a Halo, but You Can’t Directly See It:

Scientists believe that 90% of our galaxy’s mass consists of dark matter, which gives it a mysterious halo. That means that all of the “luminous matter” – i.e. that which we can see with the naked eye or a telescopes – makes up less than 10% of the mass of the Milky Way. Its halo is not the conventional glowing sort we tend to think of when picturing angels or observing comets.

In this case, the halo is actually invisible, but its existence has been demonstrated by running simulations of how the Milky Way would appear without this invisible mass, and how fast the stars inside our galaxy’s disk orbit the center.

The heavier the galaxy, the faster they should be orbiting. If one were to assume that the galaxy is made up only of matter that we can see, then the rotation rate would be significantly less than what we observe. Hence, the rest of that mass must be made up of an elusive, invisible mass – aka. “dark matter” – or matter that only interacts gravitationally with “normal matter”.

To see some images of the probable distribution and density of dark matter in our galaxy, check out The Via Lactea Project.

3. It has Over 200 Billion Stars:

As galaxies go, the Milky Way is a middleweight. The largest galaxy we know of, which is designated IC 1101, has over 100 trillion stars, and other large galaxies can have as many as a trillion. Dwarf galaxies such as the aforementioned Large Magellanic Cloud have about 10 billion stars. The Milky Way has between 100-400 billion stars; but when you look up into the night sky, the most you can see from any one point on the globe is about 2,500. This number is not fixed, however, because the Milky Way is constantly losing stars through supernovae, and producing new ones all the time (about seven per year).

These images taken by the Spitzer Space Telescope show the dust and gas concentrations around a supernova. Credit: NASA/JPL-Caltech — *These images taken by the Spitzer Space Telescope show dust and gas concentrations around a distant supernova. Credit: NASA/JPL-Caltech*

4. It’s Really Dusty and Gassy:

Though it may not look like it to the casual observer, the Milky Way is full of dust and gas. This matter makes up a whopping 10-15% of the luminous/visible matter in our galaxy, with the remainder being the stars. Our galaxy is roughly 100,000 light years across, and we can only see about 6,000 light years into the disk in the visible spectrum. Still, when light pollution is not significant, the dusty ring of the Milky Way can be discerned in the night sky.

The thickness of the dust deflects visible light (as is explained here) but infrared light can pass through the dust, which makes infrared telescopes like the Spitzer Space Telescope extremely valuable tools in mapping and studying the galaxy. Spitzer can peer through the dust to give us extraordinarily clear views of what is going on at the heart of the galaxy and in star-forming regions.

5. It was Made From Other Galaxies:

The Milky Way wasn’t always as it is today – a beautiful, warped spiral. It became its current size and shape by eating up other galaxies, and is still doing so today. In fact, the Canis Major Dwarf Galaxy is the closest galaxy to the Milky Way because its stars are currently being added to the Milky Way’s disk. And our galaxy has consumed others in its long history, such as the Sagittarius Dwarf Galaxy.

6. Every Picture You’ve Seen of the Milky Way Isn’t It:

Currently, we can’t take a picture of the Milky Way from above. This is due to the fact that we are inside the galactic disk, about 26,000 light years from the galactic center. It would be like trying to take a picture of your own house from the inside. This means that any of the beautiful pictures you’ve ever seen of a spiral galaxy that is supposedly the Milky Way is either a picture of another spiral galaxy, or the rendering of a talented artist.

Imaging the Milky Way from above is a long, long way off. However, this doesn’t mean that we can’t take breathtaking images of the Milky Way from our vantage point!

7. There is a Black Hole at the Center:

Most larger galaxies have a supermassive black hole (SMBH) at the center, and the Milky Way is no exception. The center of our galaxy is called Sagittarius A*, a massive source of radio waves that is believed to be a black hole that measures 22,5 million kilometers (14 million miles) across – about the size of Mercury’s orbit. But this is just the black hole itself.

All of the mass trying to get into the black hole – called the accretion disk – forms a disk that has 4.6 million times the mass of our Sun and would fit inside the orbit of the Earth. Though like other black holes, Sgr A* tries to consume anything that happens to be nearby, star formation has been detected near this behemoth astronomical phenomenon.

8. It’s Almost as Old as the Universe Itself:

The most recent estimates place the age of the Universe at about 13.7 billion years. Our Milky Way has been around for about 13.6 billion of those years, give or take another 800 million. The oldest stars in our the Milky Way are found in globular clusters, and the age of our galaxy is determined by measuring the age of these stars, and then extrapolating the age of what preceded them.

Though some of the constituents of the Milky Way have been around for a long time, the disk and bulge themselves didn’t form until about 10-12 billion years ago. And that bulge may have formed earlier than the rest of the galaxy.

9. It’s Part of the Virgo Supercluster:

As big as it is, the Milky Way is part of an even larger galactic structures. Our closest neighbors include the Large and Small Magellanic Clouds, and the Andromeda Galaxy – the closest spiral galaxy to the Milky Way. Along with some 50 other galaxies, the Milky Way and its immediate surroundings make up a cluster known as the Local Group.

*A mosaic of telescopic images showing the galaxies of the Virgo Supercluster. Credit: NASA/Rogelio Bernal Andreo*

And yet, this is still just a small fraction of our stellar neighborhood. Farther out, we find that the Milky Way is part of an even larger grouping of galaxies known as the Virgo Supercluster. Superclusters are groupings of galaxies on very large scales that measure in the hundreds of millions of light years in diameter. In between these superclusters are large stretches of open space where intrepid explorers or space probes would encounter very little in the way of galaxies or matter.

In the case of the Virgo Supercluster, at least 100 galaxy groups and clusters are located within it massive 33 megaparsec (110 million light-year) diameter. And a 2014 study indicates that the Virgo Supercluster is only a lobe of a greater supercluster, Laniakea, which is centered on the Great Attractor.

10. It’s on the move:

The Milky Way, along with everything else in the Universe, is moving through space. The Earth moves around the Sun, the Sun around the Milky Way, and the Milky Way as part of the Local Group, which is moving relative to the Cosmic Microwave Background (CMB) radiation – the radiation left over from the Big Bang.

The CMB is a convenient reference point to use when determining the velocity of things in the universe. Relative to the CMB, the Local Group is calculated to be moving at a speed of about 600 km/s, which works out to about 2.2 million km/h. Such speeds stagger the mind and squash any notions of moving fast within our humble, terrestrial frame of reference!

We have written many interesting articles about the Milky Way for Universe Today. Here’s 10 Interesting Facts about the Milky Way, How Big is the Milky Way?, What is the Closest Galaxy to the Milky Way?, and How Many Stars Are There in the Milky Way?

For many more facts about the Milky Way, visit the Guide to Space, listen to the Astronomy Cast episode on the Milky Way, or visit the Students for the Exploration and Development of Space at seds.org.

December 3, 2014November 29, 2019 by Matt Williams

Planets Could Travel Along with Rogue ‘Hypervelocity’ Stars, Spreading Life Throughout the Universe

Back in 1988, astronomer Jack Hills predicted a type of “rogue”star might exist that is not bound to any particular galaxy. These stars, he reasoned, were periodically ejected from their host galaxy by some sort of mechanism to begin traveling through interstellar space.

Since that time, astronomers have made numerous discoveries that indicate these rogue, traveling stars indeed do exist, and far from being an occasional phenomenon, they are actually quite common. What’s more, some of these stars were found to be traveling at extremely high speeds, leading to the designation of hypervelocity stars (HVS).

And now, in a series of papers that published in arXiv Astrophysics, two Harvard researchers have argued that some of these stars may be traveling close to the speed of light. Known as semi-relativistic hypervelocity stars (SHS), these fast-movers are apparently caused by galactic mergers, where the gravitational effect is so strong that it fling stars out of a galaxy entirely. These stars, the researchers say, may have the potential to spread life throughout the Universe.

This finding comes on the heels of two other major announcements. The first occurred in early November when a paper published in the Astrophysical Journal reported that as many as 200 billion rogue stars have been detected in a cluster of galaxies some 4 billion light years away. These observations were made by the Hubble Space Telescope’s Frontier Fields program, which made ultra-deep multiwavelength observations of the Abell 2744 galaxy cluster.

This was followed by a study published in Science, where an international team of astronomers claimed that as many as half the stars in the entire universe live outside of galaxies.

Using ESO's Very Large Telescope, astronomers have recorded a massive star moving at more than 2.6 million kilometres per hour. Stars are not born with such large velocities. Its position in the sky leads to the suggestion that the star was kicked out from the Large Magellanic Cloud, providing indirect evidence for a massive black hole in the Milky Way's closest neighbour. Credit: ESO — *Image of a moving star captured by the ESO Very Large Telescope, believed to have been ejected from the Large Magellanic Cloud. Credit: ESO*

However, the recent observations made by Abraham Loeb and James Guillochon of Harvard University are arguably the most significant yet concerning these rogue celestial bodies. According to their research papers, these stars may also play a role in spreading life beyond the boundaries of their host galaxies.

In their first paper, the researchers trace these stars to galaxy mergers, which presumably lead to the formation of massive black hole binaries in their centers. According to their calculations, these supermassive black holes (SMBH) will occasionally slingshot stars to semi-relativistic speeds.

“We predict the existence of a new population of stars coasting through the Universe at nearly the speed of light,” Loeb told Universe Today via email. “The stars are ejected by slingshots made of pairs of massive black holes which form during mergers of galaxies.”

These findings have further reinforced that massive compact bodies, widely known as a supermassive black holes (SMBH), exist at the center of galaxies. Here, the fastest known stars exist, orbiting the SMBH and accelerating up to speeds of 10,000 km per second (3 percent the speed of light).

According to Leob and Guillochon, however, those that are ejected as a result of galactic mergers are accelerated to anywhere from one-tenth to one-third the speed of light (roughly 30,000 – 100,000 km per second).

Image of a hypervelocity star found in data from the Sloan Digital Sky Survey. Credit: Vanderbilt University

Observing these semi-relativistic stars could tell us much about the distant cosmos, according to the Harvard researchers. Compared to conventional research, which relied on subatomic particles like photons, neutrinos, and cosmic rays from distant galaxies, studying ejected stars offers numerous advantages.

“Traditionally, cosmologists used light to study the Universe but objects moving less than the speed of light offer new possibilities,” said Loeb. “For example, stars moving at different speeds allow us to probe a distant source galaxy at different look-back times (since they must have been ejected at different times in order to reach us today), in difference from photons that give us just one snapshot of the galaxy.”

In their second paper, the researchers calculate that there are roughly a trillion of these stars out there to be studied. And given that these stars were detected thanks to the Spitzer Space Telescope, it is likely that future generations will be able to study them using more advanced equipment.

All-sky infrared surveys could locate thousands of these stars speeding through the cosmos. And spectrographic analysis could tell us much about the galaxies they came from.

But how could these fast moving stars be capable of spreading life throughout the cosmos?

Could an alien spore really travel light years between different star systems? Well, as long as your theory doesn't require it to still be alive when it arrives - sure it can. — *The Theory of Panspermia argues that life is distributed throughout the universe by celestial objects. Credit: NASA/Jenny Mottar*

“Tightly bound planets can join the stars for the ride,” said Loeb. “The fastest stars traverse billions of light years through the universe, offering a thrilling cosmic journey for extra-terrestrial civilizations. In the past, astronomers considered the possibility of transferring life between planets within the solar system and maybe through our Milky Way galaxy. But this newly predicted population of stars can transport life between galaxies across the entire universe.”

The possibility that traveling stars and planets could have been responsible for the spread of life throughout the universe is likely to have implications as a potential addition to the Theory of Panspermia, which states that life exists throughout the universe and is spread by meteorites, comets, asteroids.

But Loeb told Universe Today that a traveling planetary system could have potential uses for our species someday.

“Our descendants might contemplate boarding a related planetary system once the Milky Way will merge with its sister galaxy, Andromeda, in a few billion years,” he said.

Further Reading: arxiv.org/1411.5022, arxiv.org/1411.5030

November 29, 2014December 23, 2015 by Matt Williams

Astronomers Poised to Capture Image of Supermassive Milky Way Black Hole

This artist's conception illustrates a supermassive black hole (central black dot) at the core of a young, star-rich galaxy. Now astronomers have found a rogue SMBH travelling through space. Image credit: NASA/JPL-Caltech

Scientists have long suspected that supermassive black holes (SMBH) reside at the center of every large galaxy in our universe. These can be billions of times more massive than our sun, and are so powerful that activity at their boundaries can ripple throughout their host galaxies.

In the case of the Milky Way galaxy, this SMBH is believed to correspond with the location of a complex radio source known as Sagittarius A*. Like all black holes, no one has even been able to confirm that they exist, simply because no one has ever been able to observe one.

But thanks to researchers working out of MIT’s Haystack Observatory, that may be about to change. Using a new telescope array known as the “Event Horizon Telescope” (EHT), the MIT team hopes to produce this “image of the century” very soon.Initially predicted by Einstein, scientists have been forced to study black holes by observing their apparent effect on space and matter in their vicinity. These include stellar bodies that have periodically disappeared into dark regions, never to be heard from again.

As Sheperd Doeleman, assistant director of the Haystack Observatory at Massachusetts Institute of Technology (MIT), said of black holes: “It’s an exit door from our universe. You walk through that door, you’re not coming back.”

Image of the M87 Galaxy, 50 million ly from the Milky Way, which is believed to have a SMBH at its center. Credit: NASA/CXC/KIPAC/NSF/NRAO/AUI — *Image of the M87, a giant elliptical galaxy that is believed to have a SMBH at its center. Credit: NASA/CXC/KIPAC/NSF/NRAO/AUI*

As the most extreme object predict by Einstein’s theory of gravity, supermassive black holes are the places in space where, according to Doeleman, “gravity completely goes haywire and crushes an enormous mass into an incredibly close space.”

To create the EHT array, the scientists linked together radio dishes in Hawaii, Arizona, and California. The combined power of the EHT means that it can see details 2,000 times finer than what’s visible to the Hubble Space Telescope.

These radio dishes were then trained on M87, a galaxy some 50 million light years from the Milky Way in the Virgo Cluster, and Sagittarius A* to study the event horizons at their cores.

Other instruments have been able to observe and measure the effects of a black hole on stars, planets, and light. But so far, no one has ever actually seen the Milky Way’s Supermassive black hole.

According to David Rabanus, instruments manager for ALMA: “There is no telescope available which can resolve such a small radius,” he said. “It’s a very high-mass black hole, but that mass is concentrated in a very, very small region.”

Doeleman’s research focuses on studying super massive black holes with sufficient resolution to directly observe the event horizon. To do this his group assembles global networks of telescopes that observe at mm wavelengths to create an Earth-size virtual telescope using the technique of Very Long Baseline Interferometry (VLBI).

: Image of Sagittarius A*, the complex radio source at the center of the Milky Way, and believed to be a SMBH. Credit: NASA/Chandra

“We target SgrA*, the 4 million solar mass black hole at the center of the Milky Way, and M87, a giant elliptical galaxy,” says Doeleman. “Both of these objects present to us the largest apparent event horizons in the Universe, and both can be resolved by (sub)mm VLBI arrays.” he added. “We call this project The Event Horizon Telescope (EHT).”

Ultimately, the EHT project is a world-wide collaboration that combines the resolving power of numerous antennas from a global network of radio telescopes to capture the first image ever of the most exotic object in our Universe – the event horizon of a black hole.

“In essence, we are making a virtual telescope with a mirror that is as big as the Earth,” said Doeleman who is the principal investigator of the Event Horizon Telescope. “Each radio telescope we use can be thought of as a small silvered portion of a large mirror. With enough such silvered spots, one can start to make an image.”

“The Event Horizon Telescope is the first to resolve spatial scales comparable to the size of the event horizon of a black hole,” said University of California, Berkeley astronomer Jason Dexter. “I don’t think it’s crazy to think we might get an image in the next five years.”

First postulated by Albert Einstein’s Theory of General Relativity, the existence of black holes has since been supported by decades’ worth of observations, measurements, and experiments. But never has it been possible to directly observe and image one of these maelstroms, whose sheer gravitational power twists and mangle the very fabric of space and time.

Finally being able to observe one will not only be a major scientific breakthrough, but could very well provide the most impressive imagery ever captured.

November 19, 2014December 23, 2015 by Jason Major

Did a Galactic Smashup Kick Out a Supermassive Black Hole?

Near-infrared image of the dwarf galaxy Markarian 177 and what appears to be an ejected SMBH. Credit: W. M. Keck Observatory/M. Koss (ETH Zurich) et al.

Crazy things can happen when galaxies collide, as they sometimes do. Although individual stars rarely impact each other, the gravitational interactions between galaxies can pull enormous amounts of gas and dust into long streamers, spark the formation of new stars, and even kick objects out into intergalactic space altogether. This is what very well may have happened to SDSS1133, a suspected supermassive black hole found thousands of light-years away from its original home.

The two Keck 10-meter domes atop Mauna Kea. (Rick Peterson/WMKO)

Seen above in a near-infrared image acquired with the Keck II telescope in Hawaii, SDSS1133 is the 40-light-year-wide bright source observed 2,300 light-years out from the dwarf galaxy Markarian 177, located 90 million light-years away in the constellation Ursa Major (or, to use the more familiar asterism, inside the bowl of the Big Dipper.)

The two bright spots at the disturbed core of Markarian 177 are thought to indicate recent star formation, which could have occurred in the wake of a previous collision.

“We suspect we’re seeing the aftermath of a merger of two small galaxies and their central black holes,” said Laura Blecha, an Einstein Fellow in the University of Maryland’s Department of Astronomy and a co-author of an international study of SDSS1133. “Astronomers searching for recoiling black holes have been unable to confirm a detection, so finding even one of these sources would be a major discovery.”

Interactions between supermassive black holes during a galactic collision would also result in gravitational waves, elusive phenomena predicted by Einstein that are high on astronomers’ most-wanted list of confirmed detections.

Watch an animation of how the suspected collision and subsequent eviction may have happened:

But besides how it got to where it is, the true nature of SDSS1133 is a mystery as well.

The persistently bright near-infrared source has been detected in observations going back at least 60 years. Whether or not SDSS1133 is indeed a supermassive black hole has yet to be determined, but if it isn’t then it’s a very unusual type of extremely massive star known as an LBV, or Luminous Blue Variable. If that is the case though, it’s peculiar even for an LBV; SDSS1133 would have had to have been continuously pouring out energy in a for over half a century until it exploded as a supernova in 2001.

To help determine exactly what SDSS1133 is, continued observations with Hubble’s Cosmic Origins Spectrograph instrument are planned for Oct. 2015.

“We found in the Pan-STARRS1 imaging that SDSS1133 has been getting significantly brighter at visible wavelengths over the last six months and that bolstered the black hole interpretation and our case to study SDSS1133 now with HST,” said Yanxia Li, a UH Manoa graduate student involved in the research.

And, based on data from NASA’s Swift mission the UV emission of SDSS1133 hasn’t changed in ten years, “not something typically seen in a young supernova remnant” according to Michael Koss, who led the study and is now an astronomer at ETH Zurich.

Regardless of what SDSS1133 turns out to be, the idea of such a massive and energetic object soaring through intergalactic space is intriguing, to say the least.

The study will be published in the Nov. 21 edition of Monthly Notices of the Royal Astronomical Society.

Source: Keck Observatory