Train with 25 lakh litres of water reaches parched Chennai

Leiden, Jul 2: Astronomers have discovered a luminous galaxy caught in the act of reionizing its surrounding gas only 800 million years after the Big Bang.

The research, led by Romain Meyer, PhD student at UCL in London, UK, has been presented at the virtual annual meeting of the European Astronomical Society (EAS).

Studying the first galaxies that formed 13 billion years ago is essential to understanding our cosmic origins. One of the current hot topics in extragalactic astronomy is 'cosmic reionization,' the process in which the intergalactic gas was ionized (atoms stripped of their electrons).

Cosmic reionization is similar to an unsolved murder: We have clear evidence for it, but who did it, how and when? We now have strong evidence that hydrogen reionization was completed about 13 billion years ago, in the first billion years of the universe, with bubbles of ionized gas slowly growing and overlapping.

The objects capable of creating such ionized hydrogen bubbles have however remained mysterious until now: the discovery of a luminous galaxy in which 60-100 percent of ionizing photons escape, is likely responsible for ionizing its local bubble. This suggests the case is closer to being solved.

The two main suspects for cosmic reionization are usually 1) a population of numerous faint galaxies leaking ~10 percent of their energetic photons, and 2) an 'oligarchy' of luminous galaxies with a much larger percentage (>50 percent) of photons escaping each galaxy.

In either case, these first galaxies were very different from those today: galaxies in the local universe are very inefficient leakers, with only <2-3 percent of ionizing photons escaping their host. To understand which galaxies governed cosmic reionization, astronomers must measure the so-called escape fractions of galaxies in the reionization era.

The detection of light from excited hydrogen atoms (the so-called Lyman-alpha line) can be used to infer the fraction of escaping photons. On the one hand, such detections are rare because reionization-era galaxies are surrounded by neutral gas which absorbs that signature hydrogen emission.

On the other hand, if this hydrogen signal is detected it represents a 'smoking gun' for a large ionized bubble, meaning we have caught a galaxy reionizing its surroundings. The size of the bubble and the galaxy's luminosity determines whether it is solely responsible for creating this ionized bubble or if unseen accomplices are necessary.

The discovery of a luminous galaxy 800 million years after the Big Bang supports the scenario where an 'oligarchy' of bright leakers emits most of the ionizing photons.

"It is the first time we can point to an object responsible for creating an ionized bubble, without the need for a contribution from unseen galaxies.

Additional observations with the upcoming James Webb Space Telescope will enable us to study further what is likely one of the best suspects for the unsolved case of cosmic reionization," said Meyer.

The Brazilian government said that the Amazon rainforest witnessed deforestation of a record 829 sq km in May, the highest monthly level since 2015.

On Friday, the National Institute for Space Research (INPE) said that deforestation in the Amazon increased by 91 sq km compared to the same period last year, reports Xinhua news agency.

Between January and April, destruction of the forest by illegal loggers and ranchers rose 55 per cent, or a total of 1,202 sq km was wiped out, it said.

The Real-time Deforestation Detection system, a federal project created to monitor human activity in the Amazon, alerted authorities to the increase in the rate of destruction of the rainforest.

A recent study by the Amazon Environmental Research Institute (IPAM) warned that deforestation in 2020 could reach 11,900 sq km if the pace of May, June, and July follows the historical average.

Deforestation in the region has soared since President Jair Bolsonaro took office last year, according to conservation groups.

He has argued that more farming and mining in protected areas of the forest were the only way to lift the region out of poverty.

Bolsonaro's environmental policies have been widely condemned but he has rejected the criticism, saying Brazil remains an example for conservation.

Consumer watchdog Which? has claimed that more than one billion Android phones and tablets are vulnerable to hackers as they no longer supported by security updates.

According to the research report, the most at-risk phones are any that run Android 4 or older and those smartphones running Android 7.0 which can not be updated are also at risk.

Based on data from Google analysed by Which?, two in five android device users around the world are no longer receiving the important updates. Currently, those devices are unlikely to have issues, but the lack of security leaves them open to attack.

"It is very concerning that expensive Android devices have such a short shelf life before they lose security support, leaving millions of users at risk of serious consequences if they fall victim to hackers," Kate Bevan editor Which? said in a statement.

"Google and phone manufacturers need to be upfront about security updates with clear information about how long they will last and what customers should do when they run out. The government must also push ahead with planned legislation to ensure manufacturers are far more transparent about security updates for smart devices and their impact on consumers," Kate added.

Android phone released around 2012 or earlier, including popular models like the Samsung Galaxy S3 and Sony Xperia S, are particularly at risk to hackers.

Which? has made suggestions to Android users on what to consider if they have an older phone that may be at risk.

Any Android device which is more than two years old, check whether it can be updated to a newer version of the operating system. If it is on an earlier version than Android 7.0 Nougat, try to update via Settings> System>Advanced System update.

In case a user is not able tto update the phone, the device could be at risk of being hacked if it is running a version of Android 4 or lower.

A user also need to be careful about downloading apps outside the Google Play store and should also install a mobile anti-virus via an app.