Baby universes branching off of our universe shortly after the Big Bang appear to us as black holes. Credit: Kavli IPMU
The Kavli Institute for the Physics and Mathematics of the Universe (Kavli IPMU) is home to many interdisciplinary projects which benefit from the synergy of a wide range of expertise available at the institute. One such project is the study of black holes that could have formed in the early universe, before stars and galaxies were born.
Such primordial black holes (PBHs) could account for all or part of dark matter, be responsible for some of the observed gravitational waves signals, and seed supermassive black holes found in the center of our Galaxy and other galaxies. They could also play a role in the synthesis of heavy elements when they collide with neutron stars and destroy them, releasing neutron-rich material.
In particular, there is an exciting possibility that the mysterious dark matter, which accounts for most of the matter in the universe, is composed of primordial black holes. The 2020 Nobel Prize in physics was awarded to a theorist, Roger Penrose, and two astronomers, Reinhard Genzel and Andrea Ghez, for their discoveries that confirmed the existence of black holes. Since black holes are known to exist in nature, they make a very appealing candidate for dark matter.
The recent progress in fundamental theory, astrophysics, and astronomical observations in search of PBHs has been made by an international team of particle physicists, cosmologists and astronomers, including Kavli IPMU members Alexander Kusenko, Misao Sasaki, Sunao Sugiyama, Masahiro Takada and Volodymyr Takhistov.
To learn more about primordial black holes, the research team looked at the early universe for clues. The early universe was so dense that any positive density fluctuation of more than 50 percent would create a black hole. However, cosmological perturbations that seeded galaxies are known to be much smaller. Nevertheless, a number of processes in the early universe could have created the right conditions for the black holes to form.
Hyper Suprime-Cam (HSC) is a gigantic digital camera on the Subaru Telescope. Credit: HSC project / NAOJ
One exciting possibility is that primordial black holes could form from the “baby universes” created during inflation, a period of rapid expansion that is believed to be responsible for seeding the structures we observe today, such as galaxies and clusters of galaxies. During inflation, baby universes can branch off of our universe. A small baby (or “daughter”) universe would eventually collapse, but the large amount of energy released in the small volume causes a black hole to form.
An even more peculiar fate awaits a bigger baby universe. If it is bigger than some critical size, Einstein’s theory of gravity allows the baby universe to exist in a state that appears different to an observer on the inside and the outside. An internal observer sees it as an expanding universe, while an outside observer (such as us) sees it as a black hole. In either case, the big and the small baby universes are seen by us as primordial black holes, which conceal the underlying structure of multiple universes behind their “event horizons.” The event horizon is a boundary below which everything, even light, is trapped and cannot escape the black hole.
A star in the Andromeda galaxy temporarily becomes brighter if a primordial black hole passes in front of the star, focusing its light in accordance with the theory of gravity. Credit: Kavli IPMU/HSC Collaboration
In their paper, the team described a novel scenario for PBH formation and showed that the black holes from the “multiverse” scenario can be found using the Hyper Suprime-Cam (HSC) of the 8.2m Subaru Telescope, a gigantic digital camera — the management of which Kavli IPMU has played a crucial role — near the 4,200 meter summit of Mt. Mauna Kea in Hawaii. Their work is an exciting extension of the HSC search of PBH that Masahiro Takada, a Principal Investigator at the Kavli IPMU, and his team are pursuing. The HSC team has recently reported leading constraints on the existence of PBHs in Niikura, Takada et. al. Nature Astronomy 3, 524–534 (2019)
Why was the HSC indispensable in this research? The HSC has a unique capability to image the entire Andromeda galaxy every few minutes. If a black hole passes through the line of sight to one of the stars, the black hole’s gravity bends the light rays and makes the star appear brighter than before for a short period of time. The duration of the star’s brightening tells the astronomers the mass of the black hole. With HSC observations, one can simultaneously observe one hundred million stars, casting a wide net for primordial black holes that may be crossing one of the lines of sight.
The first HSC observations have already reported a very intriguing candidate event consistent with a PBH from the “multiverse,” with a black hole mass comparable to the mass of the Moon. Encouraged by this first sign, and guided by the new theoretical understanding, the team is conducting a new round of observations to extend the search and to provide a definitive test of whether PBHs from the multiverse scenario can account for all dark matter.
Reference: “Exploring Primordial Black Holes from the Multiverse with Optical Telescopes” by Alexander Kusenko, Misao Sasaki, Sunao Sugiyama, Masahiro Takada, Volodymyr Takhistov and Edoardo Vitagliano, 30 October 2020, Physical Review Letters. DOI: 10.1103/PhysRevLett.125.181304
OSLO -An “unusually large meteor” briefly lit up southern Norway on Sunday, creating a spectacular sound and light display as it rumbled across the sky, and a bit of it may have hit Earth, possibly not far from the capital, Oslo, experts said.
There were no immediate reports of injuries or damage.
Reports of sightings started arriving around 1 a.m. with the phenomena being seen as far north as Trondheim.
A web camera in Holmestrand, south of Oslo, captured a fireball falling from the sky and erupting into a bright flash lighting up a marina.
The Norwegian Meteor network was analysing video footage and other data on Sunday to try to pinpoint the meteor’s origin and destination.
Preliminary data suggested a meteorite may have hit Earth in a large wooded area, called Finnemarka, just 60 km (40 miles) west of the capital, Oslo, the network said.
“This was crazy,” the network’s Morten Bilet, who saw and heard the meteor, told Reuters.
By Sunday afternoon no debris had been found and given the “demanding” location, one could take “some 10 years” searching for possible meteorites, Bilet said.
The meteor travelled at 15-20 km per second and lit up the night sky for about five to six seconds, Bilet said. The summer sky was dark, with the days starting to get shorter from the end of June.
Some eyewitnesses also said they felt a stronger wind blow with the event also causing a pressure wave, Bilet said.
“What we had last night was a large rock travelling likely from between Mars and Jupiter, which is our asteroid belt. And when that whizzes in, it creates a rumble, light and great excitement among us (experts) and maybe some fear among others,” Bilet said.
There were no reports of damage or people being particularly frightened, Bilet said, adding that for those nearest it was likely more of a “spooky” event.
A meteor that exploded over the central Russia near the city of Chelyabinsk in 2013 rained fireballs over a vast area and caused a shock wave that smashed windows, damaged buildings and injured 1,200 people.
Seaspan’s plans to consolidate its ship repair business at Vancouver Drydock is running into opposition from its residential neighbours.
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Seaspan Shipbuilding is outgrowing its operations on the North Shore, but the company’s plans to expand its companion Vancouver Drydock is colliding with concerns of the residential neighbourhood that has grown up around the century-old industrial waterfront.
Building new ships for the Canadian Coast Guard and Royal Canadian Navy was absorbing Seaspan’s capacity to repair ships at its main shipyard at the end of Pemberton Avenue, said company spokeswoman Kris Neely.
Neely said the company has been thinking about expanding for awhile, as part of a vision to create a “multi generational business.”
“As part of that, we’re consolidating our repair and maintenance services out of Vancouver Drydock and then being able to focus on shipbuilding efforts at our Vancouver Shipyard.”
Their plan is to push Seaspan’s existing dry dock facilities on the Lower Lonsdale waterfront 40 metres further into Burrard Inlet, then ask the Port of Vancouver to extend its water lot lease 40 metres to the west in order to add three smaller dry docks.
Seaspan submitted an application for a review of the plan to the port in April. That federal authority deemed the application complete on June 21, opening up a public comment period. That included virtual public meetings July 13 and 15, and ends July 30.
Many of the comments from residents of condo towers that face the proposed expansion have expressed opposition to allowing Seaspan’s migration west when it has space to the east of its existing docks that is already within its lease.
It isn’t just a matter of views being blocked by new facilities jutting out in front of condos, said resident Al Parsons. Residents are concerned about the impact of additional noise and pollution, including tug boats operating in the waters in front of Shipyard Commons, the bustling commercial district and public space with its waterfront trail and a playground.
“We knew Seaspan was our neighbour when we moved in,” Parsons said. “What we didn’t know was that they were going to continue to move westward and, I think, impose themselves on the (waterfront) Spirit Trail.
“It has walkers, joggers, cyclists, there’s a playground that was built for kids, which is going to be right beside this expansion.”
Parsons said residents aren’t opposed to the idea of expansion and support an initiative that Seaspan says would create 100 jobs, but don’t like there wasn’t any consultation before the company submitted its application.
And they are pushing back against a possible westward expansion, unless Seaspan proves it cannot expand east within their existing lease.
The City of North Vancouver is working on a response to Seaspan’s proposal, but would like to see the public comment period extended and all resident and business concerns taken into consideration.
“I understand the concerns and share many of them,” Mayor Linda Buchanan said in a statement. “This project will bring more family-supporting jobs to the community, but the quality of life of residents needs to be a priority as well.”
Neely said Seaspan did look at other options for this expansion, but siting the new dry docks on the east side of its operations would block water access to a fabrication shop on the site that builds components for new vessels at Vancouver Shipyards.
However, Parsons argued that the east side is perhaps more inconvenient for Seaspan, which would be free to use the east side of its property for other purposes if it were granted a westward expansion.
“I know the water lot is deemed industrial but, frankly, Seaspan is pushing too hard on this neighbourhood that a lot of people contribute tax dollars to support annually.”
NASA on Friday said it had selected SpaceX to launch a planned voyage to Jupiter’s icy moon Europa, a huge win for Elon Musk’s company as it sets its sights deeper into the solar system.
The Europa Clipper mission will launch in October 2024 on a Falcon Heavy rocket from the Kennedy Space Center in Florida, with the total contract worth $178 million.
The mission was previously supposed to take off on NASA’s own Space Launch System (SLS) rocket, which has been plagued by delays and cost overruns, with critics calling it a “jobs program” for the state of Alabama where much of the development work is taking place.
While SLS isn’t yet operational, Falcon Heavy has deployed on both commercial and government missions since its maiden flight in 2018 when it carried Musk’s own Tesla Roadster into space.
It generates more than five million pounds of thrust (22 million Newtons) at liftoff, equal to approximately eighteen 747 aircraft.
The Europa clipper orbiter will make about 40 to 50 close passes over Europa to determine whether the icy moon could harbor conditions suitable for life.
Its payload will include cameras and spectrometers to produce high-resolution images and compositional maps of the surface and atmosphere, as well as radar to penetrate the ice layer to search for liquid water below.
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