Science
Proxima b : Earth-like planet spotted just 4 light years away
A planet just 30 per cent more massive than Earth orbits in the habitable zone of Proxima Centauri , which is just 4.25 light years away . How Earth-like is it really ?
Red sun in the morning – every day ESO / M . Kornmesser
Proxima b – the planet , was discovered by astronomers who spent years looking for signs of the tiny gravitational tug exerted by a planet on its star , after spotting hints of such disruption in 2013 . Proxima Centauri is 4.25 light years from Earth , making it slightly closer than the binary star system of Alpha Centauri , which the Proxima star is thought to loosely orbit .
“ We ’ ve been excited for a long time ,” says Guillem Anglada-Escudé of Queen Mary University of London , who led the discovery as part of a project called Pale Red Dot . “ We ’ ve been hunting for this signal and confirmation of the planet for almost four years .”
The team says the planet is likely to be 30 per cent more massive than Earth , although it could be bigger than that . It orbits the star at a distance of 7.3 million kilometres – less than 5 per cent of the distance between Earth and the sun – making its year last just 11.2 Earth days .
Ebola virus has lurked in a man ’ s semen for more than 500 days
By Debora MacKenzie
The Ebola virus can persist in a man ’ s semen for much longer than we thought . A man in Guinea who survived Ebola in 2014 is now known to have carried it for at least 531 days . Earlier this year , he transmitted the virus sexually , causing it to spread to at least 10 people , and killing 8 of them .
Ebola virus was known to persist in the testes of survivors , but until now the longest it had been detected surviving in this way was 284 days after a man ’ s recovery . The latest sexual transmission of the virus recorded had been 179 days after recovery .
If these long-lasting cases turn out to be more than just rare occurrences , Ebola has the potential to flare up again in the region of the 2014 epidemic for much longer than epidemiologists have been predicting .
Guinea resurgence
The 2014 epidemic mainly affected Liberia , Sierra Leone and Guinea , and by May 2016 the World Health Organization had counted more than 28,000 cases of infection , and more than 11,000 deaths .
By the end of 2015 , the WHO had declared that all known transmission chains in Guinea had ended , but in March this year , doctors in the town of N ’ Zérékoré reported that there had been three deaths that looked suspiciously like Ebola .
N ’ Zérékoré is in the forested region of Guinea where the 2014 epidemic first started , and health officials feared that the virus had crossed over from bats to humans again . But when they analysed the virus , they found it was very similar to the virus seen in a man in this area back in November 2014 .
Tracing contacts through the area , epidemiologists found that the resurgence of the virus had in fact been sparked by this same man . Following medical advice , he had abstained from sex for 8 months after recovering from Ebola , but it now seems that this is not long enough .
Vanishing trick
In January , 470 days after he initially fell ill , this man had sex with the woman who became the first known case in this year ’ s outbreak . She then spread the virus to nine more people , one of whom carried it to Liberia .
The outbreak now seems to have been contained . But the fact that the Ebola virus can persist in semen for more than 500 days could mean other resurgences are likely .
Source : New Scientist
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