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‘Gravitational slingshot’ in star clusters may explain stellar streams

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After finding three times more black holes than expected in the Palomar 5 cluster, scientists believe they may have unlocked an understanding of how stellar streams are formed.

In the darkness of space, there are voyages of stars travelling in bright streams.

The origins of these stellar ‘tidal streams’ aren’t fully known, but they are thought to be ejected from disrupted dwarf galaxies or from star clusters.

A new paper published in Nature Astronomy addresses star clusters, black holes and their relation with star streams by examining Palomar 5, a globular cluster.

“We do not know how these streams form, but one idea is that they are disrupted star clusters,” explained Prof Mark Gieles from the Institute of Cosmos Sciences of the University of Barcelona, who is lead author of the paper.

“However, none of the recently discovered streams have a star cluster associated with them, hence we can not be sure. So, to understand how these streams formed, we need to study one with a stellar system associated with it. Palomar 5 is the only case, making it a Rosetta Stone for understanding stream formation.”

The 10bn-year-old cluster Palomar 5 is located about 80,000 light-years away in the Serpens constellation, and is one of roughly 150 globular clusters that orbit around the Milky Way.

Born during the earliest stages of galaxy formation, it is now in its final stages of dissolution. In Palomar 5, the researchers believe that they might have unlocked an understanding of these stellar streams.

‘Gravitational slingshot’

Researchers simulated the orbits and the evolution of each star from the formation of the cluster until its final dissolution. They varied the initial properties of the cluster until a good match with observations of the stream and the cluster was found.

While Palomar 5 formed with a lower black hole fraction, they found that stars escaped more efficiently than black holes.

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“The number of black holes is roughly three times larger than expected from the number of stars in the cluster, and it means that more than 20pc of the total cluster mass is made up of black holes,” said Gieles.

“They each have a mass of about 20 times the mass of the sun and they formed in supernova explosions at the end of the lives of massive stars, when the cluster was still very young.”

Over time, the black hole fraction began to increase, puffing up the cluster in what researchers called a “gravitational slingshot” interaction. This launched even more stars into the void, creating the star stream.

As more and more stars fly out of the cluster, in approximately a billion years’ time, Palomar 5 will disappear and only black holes will be there at its demise.

“This work has helped us understand that even though the fluffy Palomar 5 cluster has the brightest and longest tails of any cluster in the Milky Way, it is not unique,” added Dr Denis Erkal, a co-author of the paper from the University of Surrey.

“Instead, we believe that many similarly puffed up, black hole-dominated clusters have already disintegrated in the Milky Way tides to form the recently discovered thin stellar streams.”

The researchers highlighted the importance of the work for understanding globular cluster formation, the initial masses of stars and for the evolution of massive stars. What’s more, it has important implications for the study of gravitational waves.

“It is believed that a large fraction of binary black hole mergers form in star clusters,” said Dr Fabio Antonini from Cardiff University, another co-author on the paper.

“A big unknown in this scenario is how many black holes there are in clusters, which is hard to constrain observationally because we cannot see black holes. Our method gives us a way to learn how many [black holes] there are in a star cluster by looking at the stars they eject.”

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Power Capital takes majority interest in Terra Solar’s portfolio

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Terra Solar, a NovaUCD start-up founded in 2016, is giving up its sites in Wexford and Cork to Power Capital to develop solar farms.

Dublin-based company Power Capital Renewable Energy (PCRE) has announced plans to acquire majority interest in Terra Solar’s 400MW portfolio.

This will bring the company’s total solar assets to 840MW and boost its presence in the Irish solar power space.

A start-up that sprung out of NovaUCD, the University College Dublin accelerator, Terra Solar was founded by David Fewer and André Fernon in 2016. State-owned ESB was one of Terra Solar’s early investors, putting up €2.5m for a stake in the company.

Paris-based VC firm Omnes Capital will back the development of the solar sites over the next few years, which require around €200m to build out. Irish and international lenders will also back the development.

Power Capital director Peter Duff said that his company’s aim of becoming Ireland’s leading independent power producer has come a step closer with the deal.

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“Both Terra Solar and PCRE share common values and ambitions to help Ireland meet its 2030 targets and we are excited that Terra Solar chose us as a partner to bring these sites through construction,” he said.

The solar farm sites, located in Wexford and Cork, are a culmination of more than four years of engagement with local landowners, communities and planners, said Fewer.

“We will be retaining an equity stake in the developments and will be working intensively with all stakeholders over the coming few years to ensure that these sites are successfully constructed while equally continuing to grow our remaining development pipeline of 600MW.”

Justin Brown, co-founder of Power Capital, said that the company is currently in talks with other industry bodies about “increasing our foothold in the sector and we expect to see renewable energy being the dominant generator of electricity across Ireland within the next decade”.

Construction on the solar farms is set to begin in 2022 and the project is expected to be completed in the next five years.

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2021 iPhone photography awards – in pictures | Technology

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The 14th annual iPhone photography awards offer glimpses of beauty, hope and the endurance of the human spirit. Out of thousands of submissions, photojournalist Istvan Kerekes of Hungary was named the grand prize winner for his image Transylvanian Shepherds. In it, two rugged shepherds traverse an equally rugged industrial landscape, bearing a pair of lambs in their arms.

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With Alphabet’s legendary commitment to products, we can’t wait to see what its robotics biz Intrinsic achieves • The Register

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Alphabet today launched its latest tech startup, Intrinsic, which aims to build commercial software that will power industrial robots.

Intrinsic will focus on developing software control tools for industrial robots used in manufacturing, we’re told. Its pitch is that the days of humans having to manually program and adjust a robot’s every move are over, and that mechanical bots should be more autonomous and smart, thanks to advances in artificial intelligence and leaps in training techniques.

This could make robots easier to direct – give them a task, and they’ll figure out the specifics – and more efficient – the AI can work out the best way to achieve its goal.

“Over the last few years, our team has been exploring how to give industrial robots the ability to sense, learn, and automatically make adjustments as they’re completing tasks, so they work in a wider range of settings and applications,” said CEO Wendy Tan White.

“Working in collaboration with teams across Alphabet, and with our partners in real-world manufacturing settings, we’ve been testing software that uses techniques like automated perception, deep learning, reinforcement learning, motion planning, simulation, and force control.”

Tan White – a British entrepreneur and investor who was made an MBE by the Queen in 2016 for her services to the tech industry – will leave her role as vice president of X, Alphabet’s moonshot R&D lab, to concentrate on Intrinsic.

She earlier co-founded and was CEO of website-building biz Moonfruit, and helped multiple early-stage companies get up and running as a general partner at Entrepreneur First, a tech accelerator. She is also a board trustee of the UK’s Alan Turing Institute, and member of Blighty’s Digital Economic Council.

“I loved the role I played in creating platforms that inspired the imagination and entrepreneurship of people all over the world, and I’ve recently stepped into a similar opportunity: I’m delighted to share that I’m now leading Intrinsic, a new Alphabet company,” she said.

The new outfit is another venture to emerge from Google-parent Alphabet’s X labs, along with Waymo, the self-driving car startup; and Verily, a biotech biz. ®

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