Supermassive black holes tend to sit, more or less stationary, at the centers of galaxies. But not all of these awesome cosmic objects stay put; some may be knocked askew, wobbling around galaxies like cosmic nomads.
We call such black holes ‘wanderers’, and they’re largely theoretical, because they are difficult (but not impossible) to observe, and therefore quantify. But a new set of simulations has allowed a team of scientists to work out how many wanderers there should be, and whereabouts – which in turn could help us identify them out there in the Universe.
This could have important implications for our understanding of how supermassive black holes – monsters millions to billions of times the mass of our Sun – form and grow, a process that is shrouded in mystery.
Cosmologists think that supermassive black holes (SMBHs) reside at the nuclei of all – or at least most – galaxies in the Universe. These objects’ masses are usually roughly proportional to the mass of the central galactic bulge around them, which suggests that the evolution of the black hole and its galaxy are somehow linked.
But the formation pathways of supermassive black holes are unclear. We know that stellar-mass black holes form from the core collapse of massive stars, but that mechanism doesn’t work for black holes over about 55 times the mass of the Sun.
Astronomers think that SMBHs grow via the accretion of stars and gas and dust, and mergers with other black holes (very chunky ones at nuclei of other galaxies, when those galaxies collide).
But cosmological timescales are very different from our human timescales, and the process of two galaxies colliding can take a very long time. This makes the potential window for the merger to be disrupted quite large, and the process could be delayed or even prevented entirely, resulting in these black hole ‘wanderers’.
A team of astronomers led by Angelo Ricarte of the Harvard & Smithsonian Center for Astrophysics has used the Romulus cosmological simulations to estimate how frequently this ought to have occurred in the past, and how many black holes would still be wandering today.
These simulations self-consistently track the orbital evolution of pairs of supermassive black holes, which means they are able to predict which black holes are likely to make it to the center of their new galactic home, and how long this process should take – as well as how many never get there.
“Romulus predicts that many supermassive black hole binaries form after several billions of years of orbital evolution, while some SMBHs will never make it to the center,” the researchers wrote in their paper.
“As a result, Milky Way-mass galaxies in Romulus are found to host an average of 12 supermassive black holes, which typically wander the halo far from the galactic center.”
In the early Universe, before about 2 billion years after the Big Bang, the team found, wanderers both outnumber and outshine the supermassive black holes in galactic nuclei. This means they would produce most of the light we would expect to see shining from the material around active SMBHs, glowing brightly as it orbits and accretes onto the black hole.
They remain close to their seed mass – that is, the mass at which they formed – and probably originate in smaller satellite galaxies that orbit larger ones.
And some wanderers should still be around today, according to the simulations. In the local Universe, there should actually be quite a few hanging around.
“We find that the number of wandering black holes scales roughly linearly with the halo mass, such that we expect thousands of wandering black holes in galaxy cluster halos,” the researchers wrote.
“Locally, these wanderers account for around 10 percent of the local black hole mass budget once seed masses are accounted for.”
These black holes may not necessarily be active, and therefore would be very difficult to spot. In an upcoming paper, the team will be exploring in detail the possible ways we could observe these lost wanderers.
The research has been published in the Monthly Notices of the Royal Astronomical Society.
A 900-year-old cosmic mystery has been solved by astronomers – CTV News
The mystery behind the origins of a supernova first spotted by 12th-century Chinese and Japanese astronomers has been solved, according to an international team of 21st-century astronomers.
New research, published Wednesday in The Astrophysical Journal, has linked astronomical reports from more than 800 years ago with a faint, fast-expanding nebula surrounding Parker’s Star, one of the hottest stars in the Milky Way galaxy.
The nebula, dubbed Pa30, fits the profile, location and age of the supernova, which was originally documented in 1181 AD.
“The historical reports place the guest star between two Chinese constellations, Chuanshe and Huagai,” Albert Zijlstra, astrophysics professor at the University of Manchester, said in a news release. “Parker’s Star fits the position well. That means both the age and location fit with the events of 1181.”
The first astronomers to lay eyes on the supernova, referred to as SN 1181, described it being as bright as the planet Saturn and remaining visible for six months, the authors of the study said.
Previous research has suggested Parker’s Star and the Pa30 nebula may be the result of the merging of two white dwarf stars. Such events are thought to lead to a rare and faint type of supernova called a “Type Iax” supernova.
“Only around 10 per cent of supernovae are of this type and they are not well understood. The fact that SN 1181 was faint but faded very slowly fits this type,” Zijlstra said. “It is the only such event where we can study both the remnant nebula and the merged star, and also have a description of the explosion itself.”
The key to unlocking the mystery of this historical supernova was the discovery that the Pa30 nebula is expanding at a velocity of more than 1,100 kilometres per second. From this, researchers were able to calculate the nebula’s age to be around 1,000 years old, which coincides with the events of 1181 AD.
“Combining all this information such as the age, location, event brightness and historically recorded 185-day duration, indicates that Parker’s Star and Pa30 are the counterparts of SN 1181,” Zijlstra said. “This is the only Type Iax supernova where detailed studies of the remnant star and nebula are possible.”
There have been five supernovae in the Milky Way in past millennium, and up until now, SN 1181 was the only one whose origins remained unknown.
“It is nice to be able to solve both a historical and an astronomical mystery,” Zijlstra said.
The team of astronomers who made the discovery hail from Hong Kong, the U.K., Spain, Hungary and France.
SpaceX launches amateur crew on private Earth-circling trip – Al Jazeera English
SpaceX’s first private flight has been launched into orbit with two contest winners, a healthcare worker and their rich sponsor on board, the most ambitious leap yet in space tourism.
The launch on Wednesday night was the first time a spacecraft circled Earth with an all-amateur crew and no professional astronauts.
“Punch it, SpaceX!” the flight’s billionaire leader, Jared Isaacman, urged moments before liftoff.
The Dragon capsule’s two men and two women are looking to spend three days circling the planet from an unusually high orbit – 160km (100 miles) higher than the International Space Station – before splashing down off the Florida coast this weekend.
It is SpaceX founder Elon Musk’s first entry in the competition for space tourism dollars.
Isaacman is the third billionaire to launch this summer, following the brief space-skimming flights by Virgin Galactic’s Richard Branson and Blue Origin’s Jeff Bezos in July. Only 38, Isaacman made his fortune from a payment-processing company he started in his teens.
Joining Isaacman on the trip dubbed Inspiration4 is Hayley Arceneaux, 29, a childhood bone cancer survivor who works as a physician assistant where she was treated – St Jude Children’s Research Hospital in Memphis, Tennessee. Isaacman has pledged $100m out of his own pocket to the hospital and is seeking another $100m in donations.
Arceneaux became the youngest American in space and the first person in space with a prosthesis, a titanium rod in her left leg.
Also along for the ride are sweepstakes winners Chris Sembroski, 42, a data engineer in Everett, Washington, and Sian Proctor, 51, a community college educator in Tempe, Arizona.
Once opposed to space tourism, NASA is now a supporter.
“Low-Earth orbit is now more accessible for more people to experience the wonders of space,” tweeted NASA Administrator Bill Nelson, who was a congressman when he hitched a ride on a space shuttle decades ago.
Researchers create a novel method of bioprinting neuron cells – Medical Xpress
A group of researchers including a Concordia Ph.D. student have developed a new method of bioprinting adult neuron cells. They’re using a new laser-assisted technology that maintains high levels of cell viability and functionality.
Ph.D. candidate and 2020-21 Public Scholar Hamid Orimi and his co-authors present the feasibility of a new bioprinting technology they developed in a recent paper published in the journal Micromachines. They demonstrate how the methodology they created, called Laser-Induced Side Transfer (LIST), improves on existing bioprinting techniques by using bioinks of differing viscosities, allowing for better 3D printing. Orimi, his Concordia co-supervisor Sivakumar Narayanswamy in the Gina Cody School of Engineering and Computer Science, CRHMR co-supervisor Christos Boutopoulos and co-authors at the Université de Montréal first presented the method in the Nature journal Scientific Reports in 2020.
Orimi co-wrote the newer paper with lead author Katiane Roversi, Sebastien Talbot and Boutopoulos at UdeM and Marcelo Falchetti and Edroaldo da Rocha at Federal University of Santa Catarina in Brazil. In it, the researchers demonstrate that the technology can be used to successfully print sensory neurons, a vital component of the peripheral nervous system. This, they say, is promising for the long-term development of bioprinting’s potential, including disease modeling, drug testing and implant fabrication.
Viable and functional
The researchers used dorsal root ganglion (DRG) neurons from the peripheral nervous system of mice to test their technology. The neurons were suspended in a bioink solution and loaded into a square capillary above a biocompatible substrate. Low-energy nanosecond laser pulses were focused on the middle of the capillary, generating microbubbles that expanded and ejected a cell-laden microjet onto the substrate below it. The samples were briefly incubated, then washed and re-incubated for 48 hours.
The team then ran several tests to measure the printed cells’ capacities. A viability assay found that 86 percent of the cells remained alive two days after printing. The researchers note that viability rates improved when the laser used lower energy. The thermomechanics associated with higher laser energy use was more likely to damage the cells.
Other tests measured neurite outgrowth (in which developing neurons produce new projections as they grow in response to guidance cues), neuropeptide release, calcium imaging and RNA sequencing. Overall, the results were generally encouraging, suggesting that the technique could be an important contribution to the field of bioprinting.
Good for people and animals
“In general, people often leap to conclusions when we talk about bioprinting,” Orimi says. “They think that we can now print things like human organs for transplants. While this is a long-term objective, we are very far from that point. But there are still many ways to use this technology.”
Nearest at hand is drug discovery. The team hopes to get approval to continue their research into cell grafting, which can assist greatly in drug discovery, such as for nerve recovery medicines.
Another advantage to using this technology, Orimi says, is a decrease in animal testing. This not only has a humanitarian aspect—fewer animals will be euthanized to carry out experiments meant to benefit humans—but it will also produce more accurate results, since testing will be carried out on human, not animal, tissue.
Hamid Ebrahimi Orimi et al, Drop-on-demand cell bioprinting via Laser Induced Side Transfer (LIST), Scientific Reports (2020). DOI: 10.1038/s41598-020-66565-x
University of Montreal
Researchers create a novel method of bioprinting neuron cells (2021, September 15)
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