South African astronomers, together with collaborators from Moscow have discovered Luminous Blue Variable star. A very rare sighting as the star is very old and may soon blow apart causing a supernova explosion, one of the most powerful explosions in the Universe.
Astronomer Dr A. Kniazev from the South African Astronomical Observatory (SAAO), together with collaborators from the Lomonosov Moscow State University Dr V. Gvaramadze and Dr L. Berdnikov, has recently discovered a new example of an incredibly rare kind of star known as a Luminous Blue Variable star (LBV). Out of the billions of stars mapped in our skies, only sixteen confirmed Luminous Blue Variable stars are known to date. The star, named WS1, is the latest addition to this rare group of stars. LBV stars are of interest to astronomers because they are extremely old stars which may soon die and blow apart in a supernova explosion, one of the most powerful explosions in the Universe.
Just like humans, stars do not live forever. Once their fuel has run out they stop shining and die. Stars that are much more massive than the Sun end their lives in powerful supernova explosions which can outshine all the other billions of stars in their galaxy put together. We never know when or where one of these explosions will take place but we can keep an eye on those stars most likely to go supernova in the near future: Luminous Blue Variable stars. Luminous Blue Variables (LBVs) represent a stage in the evolution of very massive stars towards the end of their life. For stars with initial masses of between 20-25 times that of our Sun the LBV stage occurs just before the star dies in a spectacular supernova explosion. For even more massive stars, they pass through the LBV phase slightly earlier in their lifetimes, but those stars too will eventually die in a supernova explosion.
LBV stars are much hotter and therefore more luminous than our Sun. They are some of the most luminous stars known, with brightnesses ranging from 250,000 to 1 million times brighter than our Sun. As a consequence of their high mass they evolve very quickly and have – astronomically speaking – short lifetimes. LBV type stars have a total lifetime of around a few million years and spend much less than one million years in the LBV phase of their evolution. The LBV phase can be thought of as a “stellar retirement” for the most massive stars. The Sun for comparison has a total lifetime of around 9 billion years. Because the LBV phase is so short-lived you have to be incredibly lucky to catch a star at the LBV stage of its life. This explains why they are so rare compared with other types of star.
LBV stars are losing vast amounts of mass as their upper atmosphere streams off into space in a so-called “stellar wind”. These stars undergo random outbursts at their surfaces, spewing their outer atmosphere into space. These outbursts cause variations in their brightness which is one of the key observational signatures of such a star. Another consequence of their immense mass loss is the formation of a bipolar or circular nebula, or cloud, around the star composed of material that has been lost from the star’s atmosphere. These nebulae are found enveloping approximately 70% of confirmed LBV stars. Eta Carinae is a famous and well studied example of a LBV star with a beautiful bipolar nebula.
As most LBVs are enshrouded in a nebula, astronomers often look for possible LBV candidates by searching for such nebulae. In the case of WS1, Kniazev and collaborators were alerted to the possibility that the star could be a LBV because they found in 2011 that it is surrounded by a circular shell of material that emits light at infra-red wavelengths. This prompted them to make follow up optical observations of the central star to confirm whether or not the star was a LBV. In 2011, using the Southern African Large Telescope (SALT) they obtained a spectrum of the star (akin to a fingerprint) and found features in the spectrum typically associated with LBV type stars. However, this information was not sufficient to confirm whether WS1 was indeed a LBV. To do this, astronomers needed to observe the star over a long time period to confirm whether its variability in brightness and in its spectral features matched that expected from a LBV type star. Kniazev and collaborators continued to observe WS1 between 2013 and 2014 using the SALT telescope to look for changes in the star’s spectrum. They also monitored the star’s brightness between 2011 and 2014 using the South African Astronomical Observatory’s 1.9 m telescope and combined their observations with publicly available data spanning over forty years.
By combining the information from all their observations they found that WS1 did indeed exhibit all the observational characteristics of a LBV type star and concluded that WS1 is an incredibly rare Luminous Blue Variable star.
“We were very lucky to discover major spectral and brightness changes in WS1 without having to wait for too long”, says Kniazev. “With this discovery, we unambiguously proved the LBV status of this star. We expect that subsequent spectral analysis will allow us to determine fundamental parameters of WS1, for example its temperature and luminosity. We also hope to find more bona fide LBVs using SALT, which will help us to understand better the evolution of LBV type stars and their relation to other types of massive, old stars.”
This discovery, published as a Letter to Monthly Notices of the Royal Astronomical Society brings the total number of LBV stars known to date to sixteen.
* Follow Gadget on Twitter on @GadgetZA
SA gets digital archive
As the world entered the centenary of Nelson Mandela’s birth on Mandela Day, 18 July 2018, South Africa celebrated the launch of a digital living archive.
The southafrica.co.za site carries content about the country’s collective heritage in South Africa’s eleven official languages.
Designed as a nation building, educational and brand promotion web based tool, the free-to-view platform features award-winning photographic and written content by leading South African photographers, authors, academics and photojournalists.
The emphasis is on quality, credible, factual content that celebrates a collective heritage in terms of the following: Cultural Heritage; Natural Heritage; Education; History; Agriculture; Industry; Mining; and Travel.
At the same time as reflecting on the nation’s history, southafrica.co.za celebrates South Africa’s natural, cultural and economic assets so that the youth can learn about their nation in their home language.
Southafrica.co.za Founder and CEO Hans Gerrizen conceptualised southafrica.co.za as a means for youth and communities from outlying areas to benefit from the digital age in terms of the web tool’s empowering educational component.
“We can only stand to deepen our collective experience of democracy and become a more forward planning nation if we know facts about our nation’s past and present in everyone’s home language,” he says.
Southafrica.co.za, with sister company Siyabona Africa, is the organiser and sponsor of the Mandela: 100 Moments photographic exhibition that runs until 30 September at Cape Town’s V&A Waterfront-based Nelson Mandela Gateway to Robben Island. The 3-month exhibition, which runs daily from 08h00 until 15h00, is showcasing one hundred iconic Nelson Mandela images taken by veteran South African photojournalist and self-taught lensman Peter Magubane.
Street art goes electric
Kaspersky Lab and British street artist D*Face have unveiled the first-ever “art helmet” design at the Formula E finale for electric cars in New York.
The ‘Save The World’ helmets will be raced by DS Virgin Racing’s drivers, Sam Bird and Alex Lynn, as they traverse the New York street circuit during the final races of the Formula E season.
The announcement signals the first art helmet by a Formula E team, continuing the heritage of art in motorsport and the cybersecurity brand’s commitment to contemporary art, creativity and innovation. D*Face took inspiration from Kaspersky Lab’s tagline, “A Company To Save The World”, and hopes that his colourful work will inspire people to take positive action.
D*Face will announce his first-ever art car design with a custom-made livery for the DS Virgin Racing Team. Its design will be released at the “Art Goes Green” event after Saturday’s race. The helmets and art car are the latest installations in the “Save the World” collection, following a major permanent public mural that was installed in Brooklyn, New York, in May.
D*Face, whose real name is Dean Stockton, said: “It is exciting to work with Kaspersky Lab on this project and create art with a real message of hope for a better future. After all, this is our world and we need to look after it. It will take every one of us to make a real lasting, impactful change. I love the mentality of the DS Virgin Racing Team and that of Formula E by showcasing sport in a way that doesn’t harm the environment, but is still just as exhilarating and fun.
“It is time for us all to stand together and make a change… be that stopping data steals, climate change, plastic waste or using damaging fuels. I want everyone to make a pledge to do one thing that will help make a change.”
As a sponsor of DS Virgin Racing Team, Kaspersky Lab is responsible for protecting the team’s devices against cyber threats. The company sees the technical environment in the global sport of Formula E as the next frontier in furthering its research and development of new technologies to keep vehicles secure in the digital world.
Sylvain Filippi, Managing Director at DS Virgin Racing, said: “The whole team fully supports this great initiative and our thanks got to Kaspersky and D*Face for their collaboration. It’s an honour to have such an innovative artist bring his talents to bear in our team ahead of the season-finale; the car, drivers’ crash helmets and mural all look amazing.”
Aldo Fucelli Pessot del Bo, Head of Global Partnerships and Sponsorships at Kaspersky Lab added: “There is a need for innovation on a global scale, both in contemporary art and in the fast-growing sport of Formula E. Now, for the first time ever, Kaspersky Lab is proudly bringing together the two sectors in an effort to Save the World and unleash creativity, encourage freedom of expression and further innovation.”