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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 World Health Organisation (WHO) on Saturday launched a Health Alert on WhatsApp where over 1.5 billion users can ask questions and they will be provided with reliable information about new coronavirus 24/7.

This will also serve government decision-makers by providing the latest numbers and situation reports, WhatsApp said in a statement.

To contact the WHO Health Alert, save the number +41 79 893 1892 in phone contacts, and then simply text the word 'Hi' in a WhatsApp message to get started.

The service responds to a series of prompts and will be updated daily with the latest information.

"You can also visit the WhatsApp Coronavirus Information Hub at whatsapp.com/coronavirus," and click on the WHO link on the homepage to open up a chat with the WHO Health Alert if you have WhatsApp installed," said the micro-blogging platform.

The WHO Health Alert will provide official information on topics such as how to protect yourself from infection, travel advice, and debunking new coronavirus myths.

The service is initially launching in English but will be available in all six languages within the coming weeks (English, Arabic, Chinese, French, Russian and Spanish.)

"Digital technology gives us an unprecedented opportunity for vital health information to go viral and spread faster than the pandemic. We are proud to have partners like Facebook and WhatsApp, that are supporting us in reaching billions of people with important health information," said Dr Tedros Adhanom Ghebreyesus, Director-General of the WHO.

The WHO Health Alert is the latest official NGO or government helpline to become available on WhatsApp, joining the Singapore Government, The Israel Ministry of Health, the South Africa Department of Health, and KOMINFO Indonesia.

Earlier this week, WhatsApp, in partnership with the World Health Organization, UNICEF, and UNDP, launched the WhatsApp Coronavirus Information Hub. The hub offers general tips and resources for users around the world to reduce the spread of rumours and connect with accurate health information.

WhatsApp also announced a $1 million grant to the International Fact Checking Network to support fact-checking for the #CoronaVirusFacts Alliance.

In a first, the Supreme Court on Friday allowed the service of summons and notices, a necessity in almost all legal proceedings, through instant messenger like WhatsApp as well as by e-mail and fax.

A bench headed by Chief Justice SA Bobde observed that it has been brought to the notice of the court that it is not feasible to visit post offices for service of notices, summons, and pleadings. The bench also comprising Justices AS Bopanna and R Subhash Reddy observed that notice and summons should be sent through e-mail on the same day along with instant message through WhatsApp and other phone messenger services.

The bench clarified that all methods should be deployed for a valid service on the party. "Two blue ticks would convey that the receiver has seen the notice," noted the bench.

The bench declined the request of the Attorney General for specifically naming WhatsApp as a mode of effectuating service. The top court noted that it would not be practical to specify only WhatsApp. The apex court also permitted RBI to extend the validity of cheques in the backdrop of lockdown to contain the coronavirus outbreak.

Senior advocate V Giri representing RBI informed the bench that he had circulated the note regarding validity of a cheque as directions issued on the previous hearing.

The bench noted that it will be in discretion of the RBI to issue orders which are suitable to alter the validity of the period of a cheque.

During an earlier hearing on the matter on July 7, the Attorney General contended before the top court that the Centre had some reservations in connection with the utilization of mobile applications like WhatsApp and other apps for service of summons. The Centre's top law officer informed the apex court that these apps claimed to be encrypted, and they were not trustworthy.

The RBI counsel had contended before the top court that it was considering clarifying the validity of a cheque which has been reduced to 3 months from 6 months.