̽��ֱ�� of Cambridge - ̽��ֱ�� of Warsaw

Astronomers spot a ‘blinking giant’ near the centre of the Galaxy

sc604 — Fri, 11 Jun 2021 07:00:00 +0000

An international team of astronomers observed the star, VVV-WIT-08, decreasing in brightness by a factor of 30, so that it nearly disappeared from the sky. While many stars change in brightness because they pulsate or are eclipsed by another star in a binary system, it’s exceptionally rare for a star to become fainter over a period of several months and then brighten again.

̽��ֱ��researchers believe that VVV-WIT-08 may belong to a new class of ‘blinking giant’ binary star system, where a giant star ⎼ 100 times larger than the Sun ⎼ is eclipsed once every few decades by an as-yet unseen orbital companion. ̽��ֱ��companion, which may be another star or a planet, is surrounded by an opaque disc, which covers the giant star, causing it to disappear and reappear in the sky. ̽��ֱ��study is published in Monthly Notices of the Royal Astronomical Society.

̽��ֱ��discovery was led by Dr Leigh Smith from Cambridge’s Institute of Astronomy, working with scientists at the ̽��ֱ�� of Edinburgh, the ̽��ֱ�� of Hertfordshire, the ̽��ֱ�� of Warsaw in Poland and Universidad Andres Bello in Chile.

“It’s amazing that we just observed a dark, large and elongated object pass between us and the distant star and we can only speculate what its origin is,” said co-author Dr Sergey Koposov from the ̽��ֱ�� of Edinburgh.

Since the star is located in a dense region of the Milky Way, the researchers considered whether some unknown dark object could have simply drifted in front of the giant star by chance. However, simulations showed that there would have to be an implausibly large number of dark bodies floating around the Galaxy for this scenario to be likely.

One other star system of this sort has been known for a long time. ̽��ֱ��giant star Epsilon Aurigae is partly eclipsed by a huge disc of dust every 27 years, but only dims by about 50%. A second example, TYC 2505-672-1, was found a few years ago, and holds the current record for the eclipsing binary star system with the longest orbital period ⎼ 69 years ⎼ a record for which VVV-WIT-08 is currently a contender.

̽��ֱ��UK-based team has also found two more of these peculiar giant stars in addition to VVV-WIT-08, suggesting that these may be a new class of ‘blinking giant’ stars for astronomers to investigate.

VVV-WIT-08 was found by the VISTA Variables in the Via Lactea survey (VVV), a project using the British-built VISTA telescope in Chile and operated by the European Southern Observatory, that has been observing the same one billion stars for nearly a decade to search for examples with varying brightness in the infrared part of the spectrum.

Project co-leader Professor Philip Lucas from the ̽��ֱ�� of Hertfordshire said, “Occasionally we find variable stars that don’t fit into any established category, which we call ‘what-is-this?’, or ‘WIT’ objects. We really don’t know how these blinking giants came to be. It’s exciting to see such discoveries from VVV after so many years planning and gathering the data.”

While VVV-WIT-08 was discovered using VVV data, the dimming of the star was also observed by the Optical Gravitational Lensing Experiment (OGLE), a long-running observation campaign run by the ̽��ֱ�� of Warsaw. OGLE makes more frequent observations, but closer to the visible part of the spectrum. These frequent observations were key for modelling VVV-WIT-08, and they showed that the giant star dimmed by the same amount in both the visible and infrared light.

There now appear to be around half a dozen potential known star systems of this type, containing giant stars and large opaque discs. “There are certainly more to be found, but the challenge now is in figuring out what the hidden companions are, and how they came to be surrounded by discs, despite orbiting so far from the giant star,” said Smith. “In doing so, we might learn something new about how these kinds of systems evolve.”

Reference:
Leigh C Smith et al. ‘VVV-WIT-08: the giant star that blinked.’ Monthly Notices of the Royal Astronomical Society (2021). DOI: https://doi.org/10.1093/mnras/stab1211

Astronomers have spotted a giant ‘blinking’ star towards the centre of the Milky Way, more than 25,000 light years away.

There are certainly more to be found, but the challenge now is in figuring out what the hidden companions are, and how they came to be surrounded by discs, despite orbiting so far from the giant star

Leigh Smith

Amanda Smith

Artist's impression of the binary star VVV-WIT-08

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Yes

Cambridge to launch Polish Studies programme

ag236 — Fri, 14 Jul 2017 09:54:26 +0000

̽��ֱ��signing will mark the grant of 15 million złotys (approximately £3.1 million), allocated to the ̽��ֱ�� of Warsaw by the Polish Ministry of Science and Higher Education, to endow in perpetuity a Polish Studies Programme at Cambridge.

̽��ֱ��programme will provide opportunities for research collaboration, as well as teaching in Polish language, literature and culture.

̽��ֱ��programme’s research output will be complemented by a series of high-profile public events that will aim to stimulate research in Polish culture and society, and promote greater understanding of Poland’s role in European history as well as its position as a rising economic power.
̽��ֱ��new initiative will build on the success of the existing four-year pilot programme in Polish Studies at the ̽��ֱ��, led by Dr Stanley Bill of Cambridge’s Department of Slavonic Studies and supported by the Foundation for Polish Science (FNP), the M.B. Grabowski Fund, the Zdanowich Fund and Cambridge’s School of Arts and Humanities.

Professor Sir Leszek Borysiewicz, Vice-Chancellor of the ̽��ֱ�� of Cambridge, signed the agreement with the Rector of the ̽��ֱ�� of Warsaw, Professor Marcin Pałys.

Professor Martin Millett, Head of the School of Arts and Humanities at the ̽��ֱ�� of Cambridge, said: “We are delighted to be strengthening this relationship with our colleagues in Poland, which is not only of strategic importance to the ̽��ֱ�� of Cambridge, but of significant import at this time in the history of Europe.”

“ ̽��ֱ��continuity of Polish Studies at the ̽��ֱ�� of Cambridge is an opportunity for both parties to develop teaching and research cooperation,” said Assistant Professor Maciej Duszczyk, Vice Rector for Research at the ̽��ֱ�� of Warsaw. He added: “An Advisory Board for the new Polish Studies programme at Cambridge –consisting of representatives from the ̽��ֱ�� of Cambridge, the ̽��ֱ�� of Warsaw, and the Foundation for Polish Science—will be tasked with setting the framework for our collaboration.”

̽��ֱ��agreement was concluded with the support of Poland’s Ministry of Science and Higher Education.

In the autumn, representatives of both universities will meet in Warsaw to take part in an event to mark the enhanced collaboration.

Polish language, literature and culture will be a permanent feature of the ̽��ֱ�� of Cambridge’s research and teaching following the signing, today, of an agreement with the ̽��ֱ�� of Warsaw.

We are delighted to be strengthening this relationship with our colleagues in Poland, which is not only of strategic importance to the ̽��ֱ�� of Cambridge, but of significant import at this time in the history of Europe.

Prof Martin Millett

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Yes

British and Polish ̽��ֱ�� leaders reaffirm strong academic links

pbh25 — Fri, 16 Oct 2015 10:33:29 +0000

̽��ֱ��strength, and the considerable untapped potential, of academic links between the ̽��ֱ�� of Cambridge and Poland were in evidence during the recent visit of a group of senior Polish scientists and university leaders.

̽��ֱ��Polish delegation, including Professor Marcin Palys, Rector of Warsaw ̽��ֱ��, and Professor Maciej Żylicz, President of the Foundation for Polish Science (FNP), were in Cambridge last month for a round table on UK-Poland scientific collaboration. They were welcomed by the Vice-Chancellor of the ̽��ֱ�� of Cambridge, Professor Sir Leszek Borysiewicz, and by Dr Stanley Bill, Director of the ̽��ֱ��’s pilot initiative for Polish Studies.

Marking the first anniversary of the launch of the Polish Studies initiative, Dr Bill said: “ ̽��ֱ��high level meeting of leaders from British and Polish institutions generated a very fruitful exchange of ideas for future cooperation in science and innovation. It was especially encouraging to see consensus on the importance of the humanities in this process. Research collaboration in any area is a form of cultural exchange, and requires mutual respect and understanding.”

He added: “ ̽��ֱ��new initiative in Polish Studies in the Department of Slavonic Studies at Cambridge precisely aims to provide British students with knowledge of Poland's culture and language, while also educating the broader public through a series of special events. We believe that this work will form an important part of the process of building bridges between the UK and Poland across a range of areas.”

Commenting on the discussions about student mobility and researcher exchange, Professor Palys said: “ ̽��ֱ��interest for collaboration in scientific projects is clearly rising.” He expressed his support for the work of the Polish Studies programme, which, he said, “will trigger more research in humanities and beyond”.

At the end of the visit, which was supported by the British Embassy in Warsaw, Professor Żylicz remarked: “Poland has huge potential, and already quite significant scientific achievements in many fields of science. ̽��ֱ��United Kingdom brings to the table a culture of excellence in scientific work. As we gradually get to know each other and start to work together our scientific efforts may bring outstanding results.”

̽��ֱ��anniversary of the Polish Studies initiative has been marked with a 'fruitful exchange' of ideas.

Tony Bowden

Uniwersytet, Warsaw

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Yes

Gaia discovers its first supernova

sc604 — Fri, 12 Sep 2014 10:30:03 +0000

This powerful event, now named Gaia14aaa, took place in a distant galaxy some 500 million light-years away, and was revealed via a sudden rise in the galaxy’s brightness between two Gaia observations separated by one month.

Gaia, which began its scientific work in July, repeatedly scans the entire sky, so that each of the roughly one billion stars in the final catalogue will be examined an average of 70 times over the next five years.

“This kind of repeated survey comes in handy for studying the changeable nature of the sky,” said Simon Hodgkin from the ̽��ֱ�� of Cambridge’s Institute of Astronomy, who is part of Gaia’s Science Alert Team.

Many astronomical sources are variable: some exhibit a regular pattern, with a periodically rising and declining brightness, while others may undergo sudden and dramatic changes.

“As Gaia goes back to each patch of the sky over and over, we have a chance to spot thousands of ‘guest stars’ on the celestial tapestry,” said Hodgkin. “These transient sources can be signposts to some of the most powerful phenomena in the Universe, like this supernova.”

Gaia’s Science Alert Team includes astronomers from the Universities of Cambridge and Warsaw, who are combing through the scans in search of unexpected changes.

It did not take long until they found the first ‘anomaly’ in the form of a sudden spike in the light coming from a distant galaxy, detected on August 30th. ̽��ֱ��same galaxy appeared much dimmer when Gaia first looked at it just a month before.

“We immediately thought it might be a supernova, but needed more clues to back up our claim,” explains Łukasz Wyrzykowski from the Warsaw ̽��ֱ�� Astronomical Observatory.

Other powerful cosmic events may resemble a supernova in a distant galaxy, such as outbursts caused by the mass-devouring supermassive black hole at the galaxy centre.

However, in Gaia14aaa, the position of the bright spot of light was slightly offset from the galaxy’s core, suggesting that it was unlikely to be related to a central black hole.

̽��ֱ��astronomers looked for more information in the light of this new source. Besides recording the position and brightness of stars and galaxies, Gaia also splits their light to create a spectrum. In fact, Gaia uses two prisms spanning red and blue wavelength regions to produce a low-resolution spectrum that allows astronomers to seek signatures of the various chemical elements present in the source of that light.

“In the spectrum of this source, we could already see the presence of iron and other elements that are known to be found in supernovas,” said Nadejda Blagorodnova, a PhD student at the Institute of Astronomy.

In addition, the blue part of the spectrum appears significantly brighter than the red part, as expected in a supernova. And not just any supernova: the astronomers already suspected it might be a ‘Type Ia’ supernova – the explosion of a white dwarf locked in a binary system with a companion star.

While other types of supernovas are the explosive demises of massive stars, several times more massive than the Sun, Type Ia supernovas are the end product of their less massive counterparts.

Low-mass stars, with masses similar to the Sun’s, end their lives gently, puffing up their outer layers and leaving behind a compact white dwarf. Their high density means that white dwarfs can exert an intense gravitational pull on a nearby companion star, accreting mass from it until the white dwarf reaches a critical mass that then sparks a violent explosion.

To confirm the nature of this supernova, the astronomers complemented the Gaia data with more observations from the ground, using the Isaac Newton Telescope (INT) and the robotic Liverpool Telescope on La Palma, in the Canary Islands.

A high-resolution spectrum, obtained on September 3rd with the INT, confirmed not only that the explosion corresponds to a Type Ia supernova, but also provided an estimate of its distance. This proved that the supernova happened in the galaxy where it was observed.

“This is the first supernova in what we expect to be a long series of discoveries with Gaia,” said Dr Timo Prusti, ESA’s Gaia Project Scientist.

Supernovas are rare events: only a couple of these explosions happen every century in a typical galaxy. But they are not so rare over the whole sky, if we take into account the hundreds of billions of galaxies that populate the Universe.

Astronomers in the Science Alert Team are currently getting acquainted with the data, testing and optimising their detection software. In a few months, they expect Gaia to discover about three new supernovas every day.

In addition to supernovas, Gaia will discover thousands of transient sources of other kinds – stellar explosions on smaller scale than supernovas, flares from young stars coming to life, outbursts caused by black holes that disrupt and devour a nearby star, and possibly some entirely new phenomena never seen before.

“ ̽��ֱ��sky is ablaze with peculiar sources of light, and we are looking forward to probing plenty of those with Gaia in the coming years,” said Prusti.

Adapted from European Space Agency press release.

While scanning the sky to measure the positions and movements of stars in our Galaxy, Gaia has discovered its first stellar explosion in another galaxy far, far away.

As Gaia goes back to each patch of the sky over and over, we have a chance to spot thousands of ‘guest stars’ on the celestial tapestry

Simon Hodgkin

ESA/ATG medialab/C. Carreau

An artist’s impression of a Type Ia supernova – the explosion of a white dwarf locked in a binary system with a companion star.

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Yes