From University of Warwick (UK) : “Planetary shields will buckle under stellar winds from their dying stars”

From University of Warwick (UK)

21 July 2021

Peter Thorley
Media Relations Manager (Warwick Medical School and Department of Physics) | Press & Media Relations | University of Warwick
Email: peter.thorley@warwick.ac.uk
Mob: +44 (0) 7824 540863

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An illustration of material being ejected from the Sun (left) interacting with the magnetosphere of the Earth (right). When the Sun evolves to become a red giant star, the Earth may be swallowed by our star’s atmosphere, and with a much more unstable solar wind, even the resilient and protective magnetospheres of the giant outer planets may be stripped away.NASA Marshall Space Flight Center (US) / National Aeronautics Space Agency (US).

Any life identified on planets orbiting white dwarf stars almost certainly evolved after the star’s death, says a new study led by the University of Warwick that reveals the consequences of the intense and furious stellar winds that will batter a planet as its star is dying.

The research is published in MNRAS, and lead author Dr Dimitri Veras of the University of Warwick will present it today (21 July) at the online National Astronomy Meeting (NAM 2021).

The research provides new insight for astronomers searching for signs of life around these dead stars by examining the impact that their winds will have on orbiting planets during the star’s transition to the white dwarf stage. The study concludes that it is nearly impossible for life to survive cataclysmic stellar evolution unless the planet has an intensely strong magnetic field – or magnetosphere – that can shield it from the worst effects.

In the case of Earth, solar wind particles can erode the protective layers of the atmosphere that shield humans from harmful ultraviolet radiation. The terrestrial magnetosphere acts like a shield to divert those particles away through its magnetic field. Not all planets have a magnetosphere, but Earth’s is generated by its iron core, which rotates like a dynamo to create its magnetic field.

All stars eventually run out of available hydrogen that fuels the nuclear fusion in their cores. In the Sun the core will then contract and heat up, driving an enormous expansion of the outer atmosphere of the star into a ‘red giant’. The Sun will then stretch to a diameter of tens of millions of kilometres, swallowing the inner planets, possibly including the Earth. At the same time the loss of mass in the star means it has a weaker gravitational pull so the remaining planets move further away.

The Sun will then stretch to a diameter of tens of millions of kilometres, swallowing the inner planets, possibly including the Earth. At the same time the loss of mass in the star means it has a weaker gravitational pull, so the remaining planets move further away.

During the red giant phase, the solar wind will be far stronger than today, and it will fluctuate dramatically. Veras and Vidotto modelled the winds from 11 different types of stars, with masses ranging from one to seven times the mass of our Sun.

Their model demonstrated how the density and speed of the stellar wind, combined with an expanding planetary orbit, conspires to alternatively shrink and expand the magnetosphere of a planet over time. For any planet to maintain its magnetosphere throughout all stages of stellar evolution, its magnetic field needs to be at least one hundred times stronger than Jupiter’s current magnetic field.

The process of stellar evolution also results in a shift in a star’s habitable zone which is the distance that would allow a planet to be the right temperature to support liquid water. In our solar system the habitable zone would move from about 150 million km from the Sun-where Earth is currently positioned-up to 6 billion km or beyond Neptune. Although an orbiting planet would also change position during the giant branch phases, the scientists found that the habitable zone moves outward more quickly than the planet posing additional challenges to any existing life hoping to survive the process.

Eventually the red giant sheds its entire outer atmosphere, leaving behind the dense hot white dwarf remnant. These do not emit stellar winds, so once the star reaches this stage the danger to surviving planets has passed.

Dr Dimitri Veras of the University of Warwick Department of Physics said: “This study demonstrates the difficulty of a planet maintaining its protective magnetosphere throughout the entirety of the giant branch phases of stellar evolution.”

“One conclusion is that life on a planet in the habitable zone around a white dwarf would almost certainly develop during the white dwarf phase unless that life was able to withstand multiple extreme and sudden changes in its environment.”

“We know that the solar wind in the past eroded the Martian atmosphere, which, unlike Earth, does not have a large-scale magnetosphere. What we were not expecting to find is that the solar wind in the future could be as damaging even to those planets that are protected by a magnetic field”, says Dr Aline Vidotto of Trinity College Dublin, the University of Dublin(IE), the co-author of the study.

Future missions like the James Webb Space Telescope due to be launched later this year should reveal more about planets that orbit white dwarf stars, including whether planets within their habitable zones show biomarkers that indicate the presence of life, so the study provides valuable context to any potential discoveries.

So far no terrestrial planet that could support life around a white dwarf has been found, but two known gas giants are close enough to their star’s habitable zone to suggest that such a planet could exist. These planets likely moved in closer to the white dwarf as a result of interactions with other planets further out.

Dr Veras adds: “These examples show that giant planets can approach very close to the habitable zone. The habitable zone for a white dwarf is very close to the star because they emit much less light than a Sun-like star. However, white dwarfs are also very steady stars as they have no winds. A planet that’s parked in the white dwarf habitable zone could remain there for billions of years, allowing time for life to develop provided that the conditions are suitable.”

See the full article here.

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The establishment of the The University of Warwick (UK) was given approval by the government in 1961 and received its Royal Charter of Incorporation in 1965.

The idea for a university in Coventry was mooted shortly after the conclusion of the Second World War but it was a bold and imaginative partnership of the City and the County which brought the University into being on a 400-acre site jointly granted by the two authorities. Since then, the University has incorporated the former Coventry College of Education in 1978 and has extended its land holdings by the purchase of adjoining farm land.

The University initially admitted a small intake of graduate students in 1964 and took its first 450 undergraduates in October 1965. In October 2013, the student population was over 23,000 of which 9,775 are postgraduates. Around a third of the student body comes from overseas and over 120 countries are represented on the campus.

The University of Warwick is a public research university on the outskirts of Coventry between the West Midlands and Warwickshire, England. The University was founded in 1965 as part of a government initiative to expand higher education. The Warwick Business School was established in 1967, the Warwick Law School in 1968, Warwick Manufacturing Group (WMG) in 1980, and Warwick Medical School in 2000. Warwick incorporated Coventry College of Education in 1979 and Horticulture Research International in 2004.

Warwick is primarily based on a 290 hectares (720 acres) campus on the outskirts of Coventry, with a satellite campus in Wellesbourne and a central London base at the Shard. It is organised into three faculties — Arts, Science Engineering and Medicine, and Social Sciences — within which there are 32 departments. As of 2019, Warwick has around 26,531 full-time students and 2,492 academic and research staff. It had a consolidated income of £679.9 million in 2019/20, of which £131.7 million was from research grants and contracts. Warwick Arts Centre is a multi-venue arts complex in the university’s main campus and is the largest venue of its kind in the UK, which is not in London.

Warwick has an average intake of 4,950 undergraduates out of 38,071 applicants (7.7 applicants per place).

Warwick is a member of Association of Commonwealth Universities (UK), the Association of MBAs, EQUIS, the European University Association (EU), the Midlands Innovation group, the Russell Group (UK), Sutton 13. It is the only European member of the Center for Urban Science and Progress, a collaboration with New York University (US). The university has extensive commercial activities, including the University of Warwick Science Park and Warwick Manufacturing Group.

Warwick’s alumni and staff include winners of the Nobel Prize, Turing Award, Fields Medal, Richard W. Hamming Medal, Emmy Award, Grammy, and the Padma Vibhushan, and are fellows to the British Academy, the Royal Society of Literature, the Royal Academy of Engineering, and the Royal Society. Alumni also include heads of state, government officials, leaders in intergovernmental organisations, and the current chief economist at the Bank of England. Researchers at Warwick have also made significant contributions such as the development of penicillin, music therapy, Washington Consensus, Second-wave feminism, computing standards, including ISO and ECMA, complexity theory, contract theory, and the International Political Economy as a field of study.

Twentieth century

The idea for a university in Warwickshire was first mooted shortly after World War II, although it was not founded for a further two decades. A partnership of the city and county councils ultimately provided the impetus for the university to be established on a 400-acre (1.6 km^2) site jointly granted by the two authorities. There was some discussion between local sponsors from both the city and county over whether it should be named after Coventry or Warwickshire. The name “University of Warwick” was adopted, even though Warwick, the county town, lies some 8 miles (13 km) to its southwest and Coventry’s city centre is only 3.5 miles (5.6 km) northeast of the campus. The establishment of the University of Warwick was given approval by the government in 1961 and it received its Royal Charter of Incorporation in 1965. Since then, the university has incorporated the former Coventry College of Education in 1979 and has extended its land holdings by the continuing purchase of adjoining farm land. The university also benefited from a substantial donation from the family of John ‘Jack’ Martin, a Coventry businessman who had made a fortune from investment in Smirnoff vodka, and which enabled the construction of the Warwick Arts Centre.

The university initially admitted a small intake of graduate students in 1964 and took its first 450 undergraduates in October 1965. Since its establishment Warwick has expanded its grounds to 721 acres (2.9 km^2), with many modern buildings and academic facilities, lakes, and woodlands. In the 1960s and 1970s, Warwick had a reputation as a politically radical institution.

Under Vice-Chancellor Lord Butterworth, Warwick was the first UK university to adopt a business approach to higher education, develop close links with the business community and exploit the commercial value of its research. These tendencies were discussed by British historian and then-Warwick lecturer, E. P. Thompson, in his 1970 edited book Warwick University Ltd.

The Leicester Warwick Medical School, a new medical school based jointly at Warwick and University of Leicester (UK), opened in September 2000.

On the recommendation of Tony Blair, Bill Clinton chose Warwick as the venue for his last major foreign policy address as US President in December 2000. Sandy Berger, Clinton’s National Security Advisor, explaining the decision in a press briefing on 7 December 2000, said that: “Warwick is one of Britain’s newest and finest research universities, singled out by Prime Minister Blair as a model both of academic excellence and independence from the government.”

Twenty-first century
The university was seen as a favoured institution of the Labour government during the New Labour years (1997 to 2010). It was academic partner for a number of flagship Government schemes including the National Academy for Gifted and Talented Youth and the NHS University (now defunct). Tony Blair described Warwick as “a beacon among British universities for its dynamism, quality and entrepreneurial zeal”. In a 2012 study by Virgin Media Business, Warwick was described as the most “digitally-savvy” UK university.

In February 2001, IBM donated a new S/390 computer and software worth £2 million to Warwick, to form part of a “Grid” enabling users to remotely share computing power. In April 2004 Warwick merged with the Wellesbourne and Kirton sites of Horticulture Research International. In July 2004 Warwick was the location for an important agreement between the Labour Party and the trade unions on Labour policy and trade union law, which has subsequently become known as the “Warwick Agreement”.

In June 2006 the new University Hospital Coventry opened, including a 102,000 sq ft (9,500 m^2) university clinical sciences building. Warwick Medical School was granted independent degree-awarding status in 2007, and the School’s partnership with the University of Leicester was dissolved in the same year. In February 2010, Lord Bhattacharyya, director and founder of the WMG unit at Warwick, made a £1 million donation to the university to support science grants and awards.

In February 2012 Warwick and Melbourne-based Monash University (AU) announced the formation of a strategic partnership, including the creation of 10 joint senior academic posts, new dual master’s and joint doctoral degrees, and co-ordination of research programmes. In March 2012 Warwick and Queen Mary, University of London announced the creation of a strategic partnership, including research collaboration, some joint teaching of English, history and computer science undergraduates, and the creation of eight joint post-doctoral research fellowships.

In April 2012 it was announced that Warwick would be the only European university participating in the Center for Urban Science and Progress, an applied science research institute to be based in New York consisting of an international consortium of universities and technology companies led by New York University and NYU Tandon School of Engineering (US). In August 2012, Warwick and five other Midlands-based universities — Aston University (UK), the University of Birmingham (UK), the University of Leicester (UK), Loughborough University (UK) and the University of Nottingham — formed the M5 Group, a regional bloc intended to maximise the member institutions’ research income and enable closer collaboration.

In September 2013 it was announced that a new National Automotive Innovation Centre would be built by WMG at Warwick’s main campus at a cost of £100 million, with £50 million to be contributed by Jaguar Land Rover and £30 million by Tata Motors.

In July 2014, the government announced that Warwick would be the host for the £1 billion Advanced Propulsion Centre, a joint venture between the Automotive Council and industry. The ten-year programme intends to position the university and the UK as leaders in the field of research into the next generation of automotive technology.

In September 2015, Warwick celebrated its 50th anniversary (1965–2015) and was designated “University of the Year” by The Times and The Sunday Times.

Research

In 2013/14 Warwick had a total research income of £90.1 million, of which £33.9 million was from Research Councils; £25.9 million was from central government, local authorities and public corporations; £12.7 million was from the European Union; £7.9 million was from UK industry and commerce; £5.2 million was from UK charitable bodies; £4.0 million was from overseas sources; and £0.5 million was from other sources.

In the 2014 UK Research Excellence Framework (REF), Warwick was again ranked 7th overall (as 2008) amongst multi-faculty institutions and was the top-ranked university in the Midlands. Some 87% of the University’s academic staff were rated as being in “world-leading” or “internationally excellent” departments with top research ratings of 4* or 3*.

Warwick is particularly strong in the areas of decision sciences research (economics, finance, management, mathematics and statistics). For instance, researchers of the Warwick Business School have won the highest prize of the prestigious European Case Clearing House (ECCH: the equivalent of the Oscars in terms of management research).

Warwick has established a number of stand-alone units to manage and extract commercial value from its research activities. The four most prominent examples of these units are University of Warwick Science Park; Warwick HRI; Warwick Ventures (the technology transfer arm of the University); and WMG.