NASA’s Nuclear Spectroscopic Telescope Array (NuSTAR) has imaged a system known as Was 49. The system consists of a large disk galaxy called Was 49a that is colliding with a smaller dwarf galaxy called Was 49b, located about 26,000 light-years from the larger galaxy’s center.
Data from the NuSTAR mission, along with information from the Sloan Digital Sky Survey and the Discovery Channel Telescope in Arizona, show luminous, high-energy X-rays shooting out from 49b’s galactic core, suggesting it hosts an active supermassive black hole that comprises more than 2 percent of the galaxy’s entire mass, scientists say.
“This is a completely unique system and runs contrary to what we understand of galaxy mergers,” Nathan Secrest, lead author of the study and postdoctoral fellow at the U.S. Naval Research Laboratory in Washington, D.C., said in a statement from NASA. “We didn’t think that dwarf galaxies hosted supermassive black holes this big. This black hole could be hundreds of times more massive than what we would expect for a galaxy of this size, depending on how the galaxy evolved in relation to other galaxies.”
The powerful bursts of high-energy radiation emitted from dwarf galaxy 49b are fueled by the gas and dust being gobbled up by the black hole. Normally, however, it is the larger of two merging galaxies that hosts the active supermassive black hole, according to the NASA statement.
“That is because, as galaxies approach each other, their gravitational interactions create a torque that funnels gas into the larger galaxy’s central black hole,” NASA officials said. “But in this case, the smaller galaxy hosts a more luminous AGN [active galactic nucleus] with a more active supermassive black hole, and the larger galaxy’s central black hole is relatively quiet.”
The pink-colored emissions captured in the image represent the gas and dust surrounding the active supermassive black hole, while the large green cloud represents the starlight of Was 49a. Although scientists have yet to determine how the supermassive black hole of 49b grew to be so big, they expect that it will collide with the dormant black hole of 49a in several hundred million years to form one ginormous galactic beast, according to the NASA statement.
“This study is important because it may give new insight into how supermassive black holes form and grow in such systems,” Secrest said in the statement. “By examining systems like this, we may find clues as to how our own galaxy’s supermassive black hole formed.”
From today (April 5) through April 14, astronomers will use a system of radio telescopes around the world to peer at the gigantic black hole at the center of the Milky Way, a behemoth called Sagittarius A* (Sgr A*) that’s 4 million times more massive than the sun.
The researchers hope to photograph Sgr A*’s event horizon — the “point of no return” beyond which nothing, not even light, can escape. (The interior of a black hole can never be imaged, because light cannot make it out.) [The Strangest Black Holes in the Universe]
“These are the observations that will help us to sort through all the wild theories about black holes — and there are many wild theories,” Gopal Narayanan, an astronomy research professor at the University of Massachusetts Amherst, said in a statement. “With data from this project, we will understand things about black holes that we have never understood before.”
The project, known as the Event Horizon Telescope (EHT), links up observatories in Hawaii, Arizona, California, Mexico, Chile, Spain and Antarctica to create the equivalent of a radio instrument the size of the entire Earth. Such a powerful tool is necessary to view the event horizon of Sgr A*, which lies 26,000 light-years from our planet, EHT team members said.
“That’s like trying to image a grapefruit on the surface of the moon,” Narayanan said.
During the current campaign, EHT is also eyeing the supermassive black hole at the core of the galaxy M87, which lies 53.5 million light-years from Earth. This monster black hole’s mass is about 6 billion times that of the sun, so its event horizon is larger than that of Sgr A*, Narayanan said.
These observations should help astronomers determine the mass, spin and other characteristics of supermassive black holes with better precision, team members said. The researchers also aim to learn more about how material accretes into disks around black holes, and the mechanics of the plasma jets that blast from these light-gobbling giants.
EHT could also reveal more about the “information paradox” — a long-standing puzzle about whether information about the material gobbled up by black holes can be destroyed — and other deep cosmological mysteries, team members said.
“At the very heart of Einstein’s general theory of relativity, there is a notion that quantum mechanics and general relativity can be melded, that there is a grand, unified theory of fundamental concepts,” Narayanan said. “The place to study that is at the event horizon of a black hole.”
Though the current observing campaign will be over soon, it will take a while for astronomers to piece together the images. For starters, so much information will be collected by the participating telescopes around the world that it will be physically flown, rather than transmitted, to the central processing facility at the Massachusetts Institute of Technology’s Haystack Observatory.
Then, the data will have to be calibrated to account for different weather, atmospheric and other conditions at the various sites. The first results from the campaign will likely be published next year, EHT team members said.
Researchers studied an object called SDSS J0104+1535, which lies about 750 light-years from Earth in the Milky Way’s “halo,” a population of extremely old stars above the galaxy’s familiar spiral disk.
SDSS J0104+1535 is a brown dwarf — a bizarre, gaseous body larger than a planet but too small to sustain the nuclear fusion reactions that power stars. New observations by the European Southern Observatory’s Very Large Telescope in Chile provide new details about this object, which astronomers think is 10 billion years old.
For example, study team members said, SDSS J0104+1535 is about 90 times more massive than Jupiter, making it the heaviest known brown dwarf. (For perspective: The sun is 1,050 times more massive than Jupiter. And Jupiter is 318 times more massive than Earth.)
In addition, just 0.01 percent of SDSS J0104+1535 consists of elements other than hydrogen and helium — meaning that the body is 250 times purer than the sun, and the purest brown dwarf ever observed
“Pure” in this sense refers to the stuff originally present just after the Big Bang that created the universe 13.82 billion years ago — mostly hydrogen and helium, along with small amounts of lithium. All the naturally occurring elements heavier than these three were created inside stars over the eons.
“We really didn’t expect to see brown dwarfs that are this pure,” study lead author ZengHua Zhang, of the Institute of Astrophysics in the Canary Islands, said in a statement. “Having found one, though, often suggests a much larger hitherto undiscovered population. I’d be very surprised if there aren’t many more similar objects out there waiting to be found.”
The new study has been accepted for publication in the journal Monthly Notices of the Royal Astronomical Society. You can read it for free at the online preprint site arXiv.org.
Infant stars have been discovered inside raging streams of material spewed into space by a monstrous black hole, according to a new study.
The rather resilient star babies were found in jets of material ejected into space by a monster black hole at the center of a galaxy 600 million light-years away from Earth. As is the case in many other galaxies, the incredible force of the black hole’s gravity accelerates the gas and dust around it, before eventually funneling the material into two jets that flow in opposite directions away from the black hole.
Inside one of those cosmic “fire hoses,” researchers found a population of stars that is “less than a few tens of millions of years old,” and most of which are being swept along in the outflow at a rapid clip, according to a statement from the European Southern Observatory, home to the Very Large Telescope (VLT) that made the observations possible. The jets appear to provide a rich environment for the stars to form in; the scientists found the stars appear to be brighter and hotter than stars that form in “less extreme” areas of the galaxy, according to the statement. [The Strangest Black Holes in the Universe]
The jet where the star formation was detected is coming from the center of one of two galaxies currently merging together, collectively known as IRAS F23128-5919. To detect the baby stars, the research team used the MUSE and X-shooter instruments on the VLT. The researchers initially made an indirect detection of the stars inside the thickly obscured jets. Later, they were able to directly observe the baby stars.
“Astronomers have thought for a while that conditions within these outflows could be right for star formation, but no one has seen it actually happening, as it’s a very difficult observation,” Roberto Maiolino, head of the team that made the discovery and a professor of experimental astrophysics at the University of Cambridge, said in the statement. “Our results are exciting because they show unambiguously that stars are being created inside these outflows.”
Black holes are strange regions where gravity is strong enough to bend light, warp space and distort time.
star-producing region, it may ultimately subject the stars to a turbulent fate.
“The stars that form further out in the flow experience less deceleration and can even fly off out of the galaxy altogether,” Helen Russell, a researcher at the Institute of Astronomy in Cambridge, said in the statement. But Russell said that stars forming closer to the galaxy’s center “might slow down and even start heading back inwards.”
If cosmic jets are ejecting stars into space across the universe that could help explain how the region between galaxies becomes enriched with “heavy” elements, the statement said. Stars fuse light elements, like hydrogen and helium, into heavier elements, including carbon, nitrogen, oxygen and many others. The explosion of very massive stars can produce even more heavy elements. Once the ejected stars die, they could spew these heavy elements into the intergalactic medium.
Stellar formation inside the flows is considerable — the new study finds that a star about 30 times the mass of the sun is formed in the flow about once per year.
“This accounts for over a quarter of the total star formation in the entire merging galaxy system,” according to the statement.
That’s a significant-enough contribution that the fate of these stars could help determine the shape of a massive galaxy, the statement said. Elliptical and spiral galaxies have different structures suggesting different formation processes, but both types are surrounded by a halo of stars. Studying stars formed inside black hole jets could help explain how those features form.
“If star formation is really occurring in most galactic outflows, as some theories predict, then this would provide a completely new scenario for our understanding of galaxy evolution,” Maiolino said in the statement.
The new study appears today (March 27) in the journal Nature.
Ever since first mentioned by Jon Michell in a letter to the Royal Society in 1783, black holes have captured the imagination of scientists, writers, filmmakers and other artists. Perhaps part of the allure is that these enigmatic objects have never actually been “seen.” But this could now be about to change as an international team of astronomers is connecting a number of telescopes on Earth in the hope of making the first ever image of a black hole.
Black holes are regions of space inside which the pull of gravity is so strong that nothing – not even light – can escape. Their existence was predicted mathematically by Karl Schwarzchild in 1915, as a solution to equations posed in Albert Einstein’s theory of general relativity.
Astronomers have had circumstantial evidence for many decades that supermassive black holes – a million to a billion times more massive than our sun – lie at the hearts of massive galaxies. That’s because they can see the gravitational pull they have on stars orbiting around the galactic centre. When overfed with material from the surrounding galactic environment, they also eject detectable plumes or jets of plasma to speeds close to that of light. Last year, the LIGO experiment provided even more proof by famously detecting ripples in space-time caused by two medium-mass black holes that merged millions of years ago.
But while we now know that black holes exist, questions regarding their origin, evolution and influence in the universe remain at the forefront of modern astronomy.
Catching a tiny spot on the sky
On April 5-14 2017, the team behind the Event Horizon Telescope hopes to test the fundamental theories of black-hole physics by attempting to take the first ever image of a black hole’s event horizon (the point at which theory predicts nothing can escape). By connecting a global array of radio telescopes together to form the equivalent of a giant Earth-sized telescope – using a technique known as Very Long Baseline Interferometry and Earth-aperture synthesis – scientists will peer into the heart of our Milky Way galaxy where a black hole that is 4m times more massive than our sun – Sagittarius A* – lurks.
Astronomers know there is a disk of dust and gas orbiting around the black hole. The path the light from this material takes will be distorted in the gravitational field of the black hole. Its brightness and colour are also expected to be altered in predictable ways. The tell-tale signature astronomers hope to see with the Event Horizon Telescope is a bright crescent shape rather than a disk. And they may even see the shadow of the black hole’s event horizon against the backdrop of this brightly shining swirling material.
The array connects nine stations spanning the globe – some individual telescopes, others collections of telescopes – in Antarctica, Chile, Hawaii, Spain, Mexico and Arizona. The “virtual telescope” has been in development for many years and the technology has been tested. However, these tests initially revealed a limited sensitivity and an angular resolution that was insufficient to probe down to the scales needed to reach the black hole. But the addition of sensitive new arrays of telescopes – including the Atacama Large Millimeter Array in Chile and the South Pole Telescope – will give the network a much-needed boost in power. It’s rather like putting on spectacles and suddenly being able to see both headlights from an oncoming car rather than a single blur of light.
The black hole is a compact source on the sky – its view at optical wavelengths (light that we can see) is completely blocked by large quantities of dust and gas. However, telescopes with sufficient resolution and operating at longer, radio millimetre wavelengths can peer through this cosmic fog.
The resolution of any kind of telescope – the finest detail that can be discerned and measured – is usually quoted as a small angle corresponding to the ratio of an object’s size to its distance. The angular size of the moon as seen from the Earth is about half a degree, or 1800 arc seconds. For any telescope, the bigger its aperture, the smaller the detail that can be resolved.
The resolution of a single radio telescope (typically with an aperture of 100 metres) is roughly about 60 arc seconds. This is comparable to the resolution of the unaided human eye and about a sixtieth of the apparent diameter of the full moon. But by connecting many telescopes, the Event Horizon Telescope will be about to achieve a resolution of 15-20 microarcsecond (0,000015 arcseconds), corresponding to being able to spy a grape at the distance of the moon.
What’s at stake?
Although the practice of connecting many telescopes in this way is well known, particular challenges lie ahead for the Event Horizon Telescope. The data recorded at each station in the network will be shipped to a central processing facility where a supercomputer will carefully combine all the data. Different weather, atmospheric and telescope conditions at each site will require meticulous calibration of the data so that scientists can be sure any features they find in the final images are not artefacts.
If it works, imaging the material inside the black hole region with angular resolutions comparable to that of its event horizon will open a new era of black hole studies and solve a number of big questions: do event horizons even exist? Does Einstein’s theory work in this region of extreme strong gravity or do we need a new theory to describe gravity this close to a black hole? Also, how are black holes fed and how is material ejected?
It may even even be possible to image the black holes at the center of nearby galaxies, such as the giant elliptical galaxy that lies at the heart of our local cluster of galaxies.
Ultimately, the combination of mathematical theory and deep physical insight, global international scientific collaborations and remarkable, tenacious long-term advances in cutting edge experimental physics and engineering look set to make revealing the nature of spacetime a defining feature of early 21st century science.
Two of the young stars were previously discovered speeding away from one another using radio and infrared observations, and observers had traced back to where they could have originated if they’d been from the same system initially. But something didn’t quite add up: the two seemed to not have as much combined energy as expected, suggesting that there might be at least one more star that was involved in the system’s breakup.
Now, astronomers think they’ve found the third — another runaway star that came from that same spot in the star-forming region 540 years ago, pinpointed in images from the Hubble Space Telescope.
“The new Hubble observations provide very strong evidence that the three stars were ejected from a multiple-star system,” the new work’s lead researcher, Kevin Luhman of Penn State University, said in a statement. “Astronomers had previously found a few other examples of fast-moving stars that trace back to multiple-star systems, and therefore were likely ejected. But these three stars are the youngest examples of such ejected stars.”
“They’re probably only a few hundred thousand years old,” Luhman added. “In fact, based on infrared images, the stars are still young enough to have disks of material leftover from their formation.”
The three stars are all in a region full of young stars called the Kleinmann-Low nebula, which is embedded in the Orion nebula 1,300 light-years away. Each is moving at top speeds of almost 30 times the speed of most of the nebula’s stars, researchers said in the statement, and the nebula’s thick shroud of dust hides them from most observers (often only radio waves, and sometimes infrared radiation, that the stars produce can make it through the dust).
Luhmann found the star while hunting for free-floating planets on a research team at the Space Telescope Science Institute in Maryland. He was looking at near-infrared data from Hubble’s Wide Field Camera 3, and noticed that one glowing spot had changed position in between 1998 and 2015 as compared to nearby stars — suggesting it was moving at about 130,000 mph (210,000 kph), according to the statement.
Working backward, he found that it could have originated in the same spot as the other two runaways. He projected that two members of the multiple-star system approached close enough to merge or form a close binary, unleashing the gravitational energy to fling all the stars outward. (The other two stars are moving away from the origin point at 60,000 mph, or 97,000 kph, and 22,000 mph, or 35,000 kph, respectively.)
According to simulations, such interactions should happen often in crowded clusters of young stars.
“But we haven’t observed many examples, especially in very young clusters,” Luhman said. “The Orion Nebula could be surrounded by additional fledgling stars that were ejected from it in the past and are now streaming away into space.”
Hubble’s observations of this galaxy cluster helped astronomers at the Atacama Large Millimeter/submillimeter Array (ALMA) in Chile to probe the secrets of the cosmos by watching how it interacts with the cosmic microwave background (CMB) — weak radiation left over from the Big Bang, when the universe as we know it was born.
The entire cosmos bears witness to the disruptive events surrounding the Big Bang. Marks left behind by the rapid expansion of space-time can be found by studying the universe’s most ancient light, the CMB. These 14 billion-year-old photons, or particles of light, now permeate the cosmos and can be used to learn about the universe via a phenomenon known as the Sunyaev-Zel’dovich effect.
Microwave radiation is invisible to the human eye, but astronomers can detect it. The microwave photons that create the CMB travel through the universe to Earth. “On their journey to us, they can pass through galaxy clusters that contain high-energy electrons,” NASA officials said in a statement. Passing through areas containing high-energy electrons can give these ancient photons get a little energy boost.
“Detecting these boosted photons through our telescopes is challenging but important,” NASA officials said. “They can help astronomers to understand some of the fundamental properties of the universe, such as the location and distribution of dense galaxy clusters.”
After ALMA observed the CMB around the galaxy cluster RX J1347.5-1145 (shown in blue), astronomers combined that data with an image from the Cluster Lensing and Supernova survey with Hubble (CLASH) to make this picture. Combining the visible-light image from Hubble with the invisible microwave data from ALMA helps astronomers understand how the CMB interacts with the galaxies inside the colossal cluster.
Supermassive black holes are thought to be embedded in the middle of most large galaxies, including the Milky Way. These monsters feed from a surrounding disk of gas, dust and other material, called an accretion disk. The gravitational pull of the black hole can heat up material in the accretion disk, causing it to radiate light.
Young and energetic black holes can gobble up only so much material, however, before the feeding process produces hot streams of gas from the accretion disk. These black-hole winds travel at about a quarter of the speed of light, and have the potential to disturb star formation in their wake
Using NuSTAR and the European Space Agency’s XMM-Newton telescope, scientists have for the first time observed winds from a nearby black hole interacting with radiation coming from the black hole’s edge, according to the authors of a study.
Harrison’s team wanted to learn about the temperatures of these winds, so they looked at X-rays coming from the black hole’s edge. As the X-rays pass through the winds, chemical elements present in the winds — such as iron and magnesium — absorb some wavelengths of light in the X-ray spectrum. The spectrum then displays holes, also called “absorption features,” revealing more about the wind’s composition.
“While observing this spectrum, the team noticed that the absorption features were disappearing and reappearing in the span of a few hours,” according to a statement from the California Institute of Technology (Caltech). “The team concluded that the X-rays were actually heating up the winds to very high temperatures — millions of degrees Fahrenheit — such that they became incapable of absorbing any more X-rays. The winds then cool off, and the absorption features return, starting the cycle over again.”
Being able to study the properties of these winds offers scientists an opportunity to learn more about how those winds impact the evolution of galaxies.
“We know that supermassive black holes affect the environment of their host galaxies, and powerful winds arising from near the black hole may be one means for them to do so,” Fiona Harrison, NuSTAR principal investigator and a physics and astronomy professor at Caltech, said in the statement. “The rapid variability, observed for the first time, is providing clues as to how these winds form, and how much energy they may carry out into the galaxy.”
The researchers are planning to conduct more observations to learn how the winds are formed, where their source of power is from and how long they last, among other features. The findings will be published tomorrow (March 2) in the journal Nature.
The dwarf planet Ceres keeps looking better and better as a possible home for alien life.
NASA’s Dawn spacecraft has spotted organic molecules — the carbon-containing building blocks of life as we know it — on Ceres for the first time, a study published today (Feb. 16) in the journal Science reports.
And these organics appear to be native, likely forming on Ceres rather than arriving via asteroid or comet strikes, study team members said.
“Because Ceres is a dwarf planet that may still preserve internal heat from its formation period and may even contain a subsurface ocean, this opens the possibility that primitive life could have developed on Ceres itself,” Michael Küppers, a planetary scientist based at the European Space Astronomy Centre just outside Madrid, said in an accompanying “News and Views” article in the same issue of Science.
“It joins Mars and several satellites of the giant planets in the list of locations in the solar system that may harbor life,” added Küppers, who was not involved in the organics discovery.
The $467 million Dawn mission launched in September 2007 to study Vesta and Ceres, the two largest objects in the main asteroid belt between Mars and Jupiter.
Dawn circled the 330-mile-wide (530 kilometers) Vesta from July 2011 through September 2012, when it departed for Ceres, which is 590 miles (950 km) across. Dawn arrived at the dwarf planet in March 2015, becoming the first spacecraft ever to orbit two different bodies beyond the Earth-moon system.
During its time at Ceres, Dawn has found bizarre bright spots on crater floors, discovered a likely ice volcano 2.5 miles (4 km) tall and helped scientists determine that water ice is common just beneath the surface, especially near the dwarf planet’s poles.
The newly announced organics discovery adds to this list of achievements. The carbon-containing molecules — which Dawn spotted using its visible and infrared mapping spectrometer instrument — are concentrated in a 385-square-mile (1,000 square km) area near Ceres’ 33-mile-wide (53 km) Ernutet crater, though there’s also a much smaller patch about 250 miles (400 km) away, in a crater called Inamahari.
And there could be more such areas; the team surveyed only Ceres’ middle latitudes, between 60 degrees north and 60 degrees south.
“We cannot exclude that there are other locations rich in organics not sampled by the survey, or below the detection limit,” study lead author Maria Cristina De Sanctis, of the Institute for Space Astrophysics and Space Planetology in Rome, told Space.com via email.
Dawn’s measurements aren’t precise enough to nail down exactly what the newfound organics are, but their signatures are consistent with tar-like substances such as kerite and asphaltite, study team members said.
“The organic-rich areas include carbonate and ammoniated species, which are clearly Ceres’ endogenous material, making it unlikely that the organics arrived via an external impactor,” co-author Simone Marchi, a senior research scientist at the Southwest Research Institute in Boulder, Colorado, said in a statement.
In addition, the intense heat generated by an asteroid or comet strike likely would have destroyed the organics, further suggesting that the molecules are native to Ceres, study team members said.
The organics might have formed via reactions involving hot water, De Sanctis and her colleagues said. Indeed, “Ceres shows clear signatures of pervasive hydrothermal activity and aqueous alteration,” they wrote in the new study.
Such activity likely would have taken place underground. Dawn mission scientists aren’t sure yet how organics generated in the interior could make it up to the surface and leave the signatures observed by the spacecraft.
“The geological and morphological settings of Ernutet are still under investigation with the high-resolution data acquired in the last months, and we do not have a definitive answer for why Ernutet is so special,” De Sanctis said.
It’s already clear, however, that Ceres is a complex and intriguing world — one that astrobiologists are getting more and more excited about.
“In some ways, it is very similar to Europa and Enceladus,” De Sanctis said, referring to ocean-harboring moons of Jupiter and Saturn, respectively.
“We see compounds on the surface of Ceres like the ones detected in the plume of Enceladus,” she added. “Ceres’ surface can be considered warmer with respect to the Saturnian and Jovian satellites, due to [its] distance from the sun. However, we do not have evidence of a subsurface ocean now on Ceres, but there are hints of subsurface recent fluids.”
The discovery is considered a key piece of evidence for a critical, but poorly understood period of time when the universe switched from being dark to radiating light.
Scientists theorize that energy from first-generation galaxies transformed the dark, electrically neutral universe into ionized and radiating plasma. But these faint galaxies are not easy to find.
This week, University of Texas astronomer Rachael Livermore and colleagues describe a successful hunt thanks to a new technique that combines deep-field Hubble Space Telescope images with what is known as “wavelet decomposition” — a light-masking equivalent of noise-canceling headphones — to computationally remove light from foreground galaxy clusters.
“The wavelet transform allows us to decompose an image into its components on different physical scales. Thus, we can isolate structures on large scales… and remove them, allowing objects on smaller scales to be identified more easily,” the scientists wrote in a draft of their upcoming paper, published on arXiv.org.
Ironically, astronomers first have to rely on galaxy clusters, which warp spacetime with their massive gravity, to serve as naturally occurring lenses that boost Hubble’s resolving power more than 100 times.
By then masking the light, Livermore, University of Texas astronomer Steven Finkelstein and Space Telescope Science Institute astronomer Jennifer Lotz found 167 galaxies that are 10 times fainter than any previously known, a number that shows “strong support” for how many early galaxies would have been needed to re-ionize the universe.
A more direct detection method will come after Hubble’s successor, the James Webb Space Telescope, is launched next year.
For decades, astronomers have tracked black holes with masses millions of times that of the sun, as well as those with tens of solar masses. But black holes between those two extremes have proved elusive. Now, astronomers studying a globular cluster have found just such a black hole at its center, showing that intermediate-mass black holes could be hiding out in these compact agglomerations of stars.
Lead study author Bülent Kiziltan, an astronomer at the Harvard-Smithsonian Center for Astrophysics (CfA), and his co-authors Holger Baumgardt (of Australia’s University of Queensland) and Abraham Loeb (also of CfA) found a black hole between 1,400 and 3,700 solar masses at the center of 47 Tucanae, a globular cluster in the southern sky some 16,700 light-years from Earth.
Black holes are usually found because they emit massive amounts of X-rays as matter falls in. Midsize black-hole candidates have been found in galaxies; a group from the University of Maryland and NASA’s Goddard Space Flight Center found one in another galaxy in 2015, and there are about a dozen objects in total.
Kiziltan and his team found this one by measuring motions of pulsars within the cluster. They found the telltale signs of a compact, massive object in the cluster’s heart. The likeliest explanation for the motions was a black hole.
“Intermediate-mass black holes have been expected [in globular clusters] for many decades,” Kiziltan told Space.com. “But we’ve not been able to find one conclusively.”
Theorists think stellar-mass black holes form from stars that are at least a few dozen times the mass of the sun. When they run out of nuclear fuel, there is no longer enough energy from radiation to hold the star’s outer layers against its immense gravity. The star collapses, and then explodes as a supernova. (Supernovas can outshine the galaxies in which they reside.) What’s left of the star then shrinks into a tiny volume. A 100-solar-mass star, as a black hole, would have a radius of about 180 miles (290 kilometers). The former star’s escape velocity exceeds that of light, resulting in a black hole, from which nothing can escape.
A big question for astronomers is what the population of black holes looks like. Given that there are supermassive black holes, and stellar-mass ones, there should be a population of black holes with masses between those two. But there don’t seem to be as many as expected. The centers of globular clusters, which are agglomerations of old stars, seemed a good place to look, as earlier studies indicated they might be there, according to the new study.
The problem is, black holes are visible only when stuff falls in them. As such, the researchers needed another method that didn’t depend on picking up radio emissions.
That’s why Kiziltan and his colleagues decided to look at the pulsars that inhabit a globular cluster. Pulsars form from stars less massive than those that make black holes. After those stars go supernova, they collapse into neutron stars
Some neutron stars spin rapidly and emit radio waves along a line offset from their rotational axes. These are called pulsars. Earthbound observers see them if Earth is in the radio beam as it sweeps across the sky. Pulsars’ rotation rates change so little that they are precise timekeepers. They are precise enough that by timing the signal and looking for any Doppler shifts, it’s possible to measure a pulsar’s movement along one’s line of sight.
Kiziltan’s group tracked the movement of some two dozen pulsars and used computer simulations to model the cluster to track down their black-hole candidate.
“We’re proposing a brand-new approach to the study of globular clusters,” Kiziltan said. “It’s not only that we see the dynamical signature of a black hole, but how to probe the region near it without going too close to it.” Probing the centers of globular clusters is usually difficult, because the density of stars makes it hard to see what’s going on.
Finding the intermediate-mass black hole raises more questions about how these black holes form, said Cole Miller, a professor of astronomy at the University of Maryland who studies black-hole formation. “Let’s say it’s an intermediate-mass black hole,” he said. “How did it get there?”
“Globular clusters have small escape speeds,” he said. “So the stars should blow away all the gas.” There will be some as stars age, such as a red giant’s stellar winds. “But that amount of gas is nowhere close enough to make an intermediate-mass black hole.”
This differs from the supermassive black holes at galactic centers, he added, because one would expect lots of matter to accumulate there, feeding a black hole and allowing it to grow very fast.
Both Kiziltan and Cole said there are several ways to grow black holes early in a cluster’s history. “One of my favorites is runaway collisions of stars or stellar- mass black holes,” Miller said. “An interesting effect is, if you have a bunch of stars in a dense stellar region, the heaviest will start runaway collisions.” Once a black hole forms — perhaps when a star that’s absorbed a few neighbors dies ― all the matter that isn’t in a stable orbit around the black hole will fall in or get ejected from the cluster, he said. That puts an automatic stop on the black hole’s growth.
For scientists to get a better handle on how such black holes might form in clusters, more of them need to be found — but that won’t be easy, Kiziltan said. The only reason it worked for 47 Tucanae was that there were enough pulsars in it to begin with, and they were close enough to see. Not every globular cluster has the right combination of distance and bright pulsars.
The wandering black hole was discovered lurking just outside a supernova remnant, a shell of expelled material left behind after a massive star explodes. Using the Atacama Submillimeter Telescope Experiment (ASTE) in Chile and the 45-meter (148 feet) Radio Telescope at Nobeyama Radio Observatory, astronomers found that the black hole had been previously hidden by a compact gas cloud emerging from the remnant.
The cloud itself has now been named “the Bullet,” because of its long, cone shape and its incredible speed — part of the cloud is moving away from the supernova remnant at more than 60 miles per second [100 kilometers per second], “which exceeds the speed of sound in interstellar space by more than two orders of magnitude,” Nobeyama Radio Observatory scientists said in the statement. The researchers now suspect that the black hole might have played a role in forming the gaseous “bullet.”
The supernova remnant, called W44, is located 10,000 light-years from Earth. The Bullet, which is about 2 light-years long [11.76 trillion miles, or 18.9 trillion km], is so energetic that it moves backward against the rotation of the Milky Way galaxy, according to the Nobeyama Radio Observatory statement.
“Most of the Bullet has an expanding motion with a speed of 50 km/s [31 miles per second], but the tip of the Bullet has a speed of 120 km/s [75 miles per second],” Masaya Yamada, lead author of the new study and a graduate student at Keio University in Japan, said in the statement. “Its kinetic energy is a few tens of times larger than that injected by the W44 supernova. It seems impossible to generate such an energetic cloud under ordinary environments.”
So what could possibly send such a huge amount of molecular gas streaming out of the supernova remnant at such high speeds? The discovery of the hidden black hole may offer an explanation.
The researchers developed two possible scenarios for how the Bullet might have formed. The first, called the explosion model, suggests that the cloud passed by a static black hole and was pulled in by the black hole’s strong gravitational forces. This could have created a powerful explosion of gas that was spit back out into space, Nobeyama scientists said.
Another theory, called the irruption model, proposes that a high-speed black hole tore through the dense molecular cloud, and the black hole’s powerful gravitational pull left a stream of gas in its wake. Further research is required to determine which model best explains the origin of the Bullet, according to the study, published Dec. 29, 2016, in The Astrophysical Journal Letters.
Although millions of black holes are thought to exist in the Milky Way, it is often difficult to locate them because they are completely black. However, this study has revealed a new way for astronomers to detect these types of elusive, stray black holes — by their influence on molecular gas clouds — that would otherwise float alone in space and remain unnoticed with no observable emissions, the scientists said in the statement.
Wormholes are a workhorse of sci-fi interstellar civilizations in books and on the screen because they solve the annoying problem of “Well, if we stuck to known physics, 99.99999 percent of the story would be as fascinating as watching people sleep.”
But could we do it? Could we actually warp and bend space-time to make a convenient tunnel, making all of our galactic dreams come true?
The concept of wormholes got its start when physicist Ludwig Flamm, and later Albert Einstein and Nathan Rosen, realized that black holes can be “extended.” When one goes about solving the fantastically complicated equations of general relativity, the machinery that predicts a black hole also predicts a phenomenon called a white hole. A white hole is pretty much what you think: Whereas a black hole’s event horizon marks a region of space that once you enter you can’t leave, it’s impossible to enter a white hole’s horizon, although anything already in there can escape.
That same mathematical machinery delivers a bonus, too: All black holes would be naturally “connected” to white holes via their singularities, making a tunnel through space. Woohoo, wormholes here we go!
Or not. While we have gobs of evidence for the existence of black holes, white holes appear to be mathematical fiction. There’s no known process in our universe that would actually form them, and even if they did pop into existence, their natural extreme instability would snuff them right out again.
Oh, yeah, and the mechanism for making black holes — the collapse of massive stars — also automatically prevents the formation of a symbiotic white hole.
And even if they did form (and they don’t), the extreme gravity of the mutual singularities would cause the wormhole tunnel to immediately stretch and snap much more quickly than anything could cross it.
Death by wormhole
But that doesn’t stop anybody from playing a fun game of “what if.” What if white holes could naturally form, or be constructed? What if we could stabilize them? What if we could attach a white hole’s singularity to a black hole and make a wormhole? What if? What if? What if?
Well, for one thing, traveling down such a wormhole would really, really suck. Literally. The entrance to the wormhole — the “throat” — sits inside the event horizon of the black hole.
That’s a problem.
The very definition of an event horizon — their very cosmique raison d’etre — is that once you enter them, you don’t get to come out. No way, no how. It doesn’t matter if there’s a wormhole tunnel inside it — you don’t get to leave.
Inside a black hole event horizon, you have only one destination: singularity town, the place of infinite density and soul-crushing gravitational forces.
So let’s say you enter a wormhole. You can watch light from another patch of the universe filter in from the opposite side. If someone else jumps in, you can meet them and have some tea together. And you can die — miserably — as you careen into the singularity.
Is there any way to make a working, even fun, wormhole, instead of a terrifying portal to inevitable destruction?
Surprisingly, yes. Well, not quite 100 percent absolutely “this is a normal part of our universe” yes. More like “if we play pretend” yes.
To construct a traversable wormhole, you need to overcome two important obstacles. First, the entrance to the wormhole has to actually sit outside the event horizon. That would allow you to enter the wormhole and blast through it to your faraway destination without fearing a “singular” encounter.
Second, the tunnel itself has to be stable and strong. It has to withstand the extreme gravity of the singularities and resist tearing apart when something flies down its length.
There is indeed a material that solves both problems. But that material has a problem all its own: It has negative mass.
That’s right: mass, but negative. A ring of negative-mass material could be used to construct a fully functional and useful wormhole. Since the exotic nature of negative mass warps spacetime in a unique way, it “inflates” the entrance to the wormhole outside the boundary of the event horizon, and stabilizes the throat of the wormhole against instabilities. It’s not an intuitive result but the math checks out.
But could such a substance exist? We’ve mapped out a good chunk of the universe, and we’ve never seen negative mass. If it did exist, it would have some pretty weird properties. For example, following the math of Newton’s Laws with some minus signs tossed in, we find that a negative-mass particle would push on a positive-mass particle, while the positive-mass particle would pull on the negative-mass one. Set two opposite-mass particles next to each other, perfectly still, and the pair would start accelerating, zooming off without any input of force.
What about the Casimir effect, the odd and fascinating attraction of two metal plates due to vacuum energy? That’s often trotted out as an example of the universe behaving badly, and a possible route to negative mass. But the Casimir force is characterized by local negative pressure (it pulls rather than pushes), not negative mass.Sure, we don’t know everything there is to know about quantum gravity and the nature of space-time at super-duper-teensy scales. Could an advanced civilization discover the path to negative mass and manipulate gravity in just the right way? Would a breakthrough in physics point a way to fashioning wormholes?
Honestly, probably not. There are just too many things working against them. Working wormholes would violate so many aspects about known (and extremely well tested) physics that I think it’s better to just work on other problems.
I know some people might accuse me of not being creative enough, but the universe doesn’t care about our creativity. The tools of science are harsh but fair judges; if an idea doesn’t work, it simply doesn’t work. There are many varied and beautiful mysteries in our universe, and we certainly haven’t unlocked all of the inner workings of the cosmos. But wormholes probably aren’t one of them.
Alpha Centauri is having a moment: Our mysterious neighboring star system has been seeing a surge of scientific interest lately, and for good reason.
Although space researchers have often focused on our own galaxy, Alpha Centauri has become a more viable option to closely study, and even potentially travel to one day. Our nearest stellar neighbor has received a lot of buzz recently due to the announcement of Breakthrough Starshot, a mission backed by famed cosmologist Stephen Hawking, Russian investor Yuri Milner and Facebook CEO Mark Zuckerberg, with the goal of sending probes to Alpha Centauri someday.
Although it’s the closest star system to our sun, Alpha Centauri is still 4.37 light-years (25 trillion miles, or 40 trillion kilometers) away from Earth. Because it’s so far away, reaching and studying Alpha Centauri poses significant challenges. But the three-star system — comprising Alpha Centauri A, Alpha Centauri B and a faint red dwarf star Proxima Centauri — also presents enormous opportunities for furthering space research, which is why it is the focus of our mission at Project Blue.
NASA’s Kepler space telescope has found thousands of exoplanets in the universe, many of which orbit in the habitable zones of their stars and could be Earth-like. In fact, one out of every two sun-like stars has a rocky, potentially Earth-like planet in its habitable zone. At Project Blue, we are aiming to actually see one with our own eyes — and take the first photograph of a planet like Earth.
So, why focus on Alpha Centauri? In short, it gives us the best opportunity to accomplish our mission.
A large reason for this is its proximity. After Alpha Centauri, the next-closest sun-like star is 2.5 times farther away and would require a telescope 2.5 times larger in order to be viewed at the same level of detail.
The system also has a unique binary structure: It contains not just one, but two stars similar to the sun, doubling our chances of finding planets in either of their habitable zones. In fact, that gives us an estimated 85 percent probability that the Alpha Centauri system harbors at least one potentially habitable planet. However, although the binary structure increases our odds, it also presents challenges. In order to take the photograph, we have to use a specialized system to efficiently suppress the light of two stars to see any potential surrounding planets.
Finally, the last reason our focus remains on our neighboring star system is that Alpha Centauri A is a yellow “G2”-type star that has a temperature and color that closely match the sun’s, thus increasing the chances of the existence of an Earth-like planet. Alpha Centauri B, which is a bit cooler and redder than our sun, is also still a good candidate to host a rocky planet like Earth.
The image we hope to take would reveal whether the planet appears blue, as Earth does from space, which could suggest that it hosts liquid oceans or a substantial atmosphere — and, therefore, the potential to support life.
Our chances of spotting a planet successfully are high in Alpha Centauri. This is only underscored by the discovery of an Earth-like planet in the star system earlier this year. Scientists have located the planet Proxima b, with a minimum mass 1.3 times that of Earth, orbiting in the habitable zone of its star, Proxima Centauri.
This recent discovery is indeed exciting, and it sparked Breakthrough Starshot to announce that it will focus on the potential to travel to Proxima b one day, once the technology is developed. However, the planet is not a good option for Project Blue. Because Proxima b orbits so closely to its small, dim star, it would be extremely difficult to image with a telescope, and as such, our focus remains on the larger stars Alpha Centauri A and B.
Alpha Centauri’s potential is exciting to not only the science community but the future of humanity, and it’s clear that it will provide us with some of our most exciting space discoveries in the years to come.
As astronomers work to learn more about the environment it, a new paper in Astrophysical Journal Letters makes predictions about what would happen to young, highly magnetized stars in Sgr A*’s vicinity. It’s the first time a star’s magnetic field has been included in simulations where a black hole tidally disrupted a star, meaning the star is pulled apart and stretched.
“Magnetic fields are a bit tricky numerically to simulate,” James Guillochon, an astrophysicist at the Harvard-Smithsonian Center for Astrophysics, told Seeker. In the past, it’s been hard to put magnetic fields in context with other influences on a star, such as gas pressure and gravity. This is especially true towards the boundary or atmosphere of the star.
The simulations show that if a star gets a “glancing blow” from a black hole, it can survive the encounter and its magnetic field amplifies strongly, by a factor of about 30. But if the star gets very close to the black hole, the star is tidally destroyed and the magnetic field maintains its strength.
“One of the immediate impacts is that we might see highly magnetized stars in the centers of galaxies, and that includes our own galactic center,” Guillochon added. “We also would expect this to affect the resulting flare that arises from the disruption of the star by the supermassive black hole. Half the matter of the star falls on to the black hole and feeds it, and that generates a luminous flare of a billion or 10 billion solar luminosities.”
A star disruption should theoretically be visible in our own galactic center, but Guillochon says that only happens about once every 10,000 years or so. Luckily, the stream of the disrupted star can persist for centuries, feeding the black hole.
Guillochon co-wrote a paper a couple of years ago about G2, a gas cloud falling into the galactic center in 2014 that produced far less activity than expected. It suggests that G2 could have been produced by the disruption of a red giant star, and its gas envelope is still feeding the black hole today.
He suggested that G2-like clouds would form by “clumping up” due to cooling instabilities, which would put regular deliveries of a G2-type cloud once every decade. When the material is highly magnetized, co-author Michael McCourt has previously suggested that the fields can help stabilize the clouds and prevent them from breaking apart. If the pattern holds true, highly magnetized clouds would continue to pass near the black hole over the next several decades.
That said, the challenge of learning about stars that survive disruption in the galactic center is they tend to be lower mass and hard to see. How many of them are magnetized, and how strongly, remains an open question, Guillochon said. Below is a short animation simulating a star’s magnetic field being torn apart by a black hole.