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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.

Pune, Jul 24: Agile and dexterous, 85-year-old Shantabai Pawar wields sticks with absolute ease as she displays 'lathi-kathi' on the streets of Pune.

A video of her, displaying her skills in the Indian martial art form for livelihood, has gone viral on social media.

Pawar told media persons that she learnt the art form when she was only eight and has been practising it since then. The ancient martial art s believed to be linked to Dombari community, a nomadic tribe in Maharashtra.

"I have been pursuing the art of lathi-kathi since I was eight. I have never left it. It is part of me and it is an honour to practice it. My father taught me this. He taught me to work hard," Pawar told media persons.

In the video, the sari-clad octogenarian takes a warrior-like stride and effortlessly rotates a stick several times in a second in her hand and around her head and then does it with two sticks together with a smile on her face. She also tosses a stick in the air and catches it with ease.

The assembled gathering is impressed and enthused.

"People come and say, 'Well done Daadi!' I practice it to earn money for my children and grandchildren," she said.

Pawar leaves her home in the morning in the conditions created by coronavirus and performs the art form on roads and streets.

"I go to various areas to perform the art form and people give money," she said.

The artiste also uses thali and stick to gather the attention of people as most of them are indoors due to conditions created by COVID-19.

Senior citizens have been advised against venturing out due to their greater susceptibility to coronavirus but Pawar said she is not afraid to step out.

"People do advise me to not go out due to fear of COVID-19 but I am not scared. Whenever I step out, I pray to my God and he has kept me safe so far," she said.

Aishwarya Kale, a dancer and the person who uploaded the video on social media, said that it is "only an artist who can understand what help another artist needs".

"I was in that area shopping for some items and it was then I saw her performing and thought that I should film her and upload her video on social media. But I never thought that the video would go viral and she would receive financial help not just from people in the country but overseas as well," Kale told media persons.

"She is now getting honour for her craft that she couldn't get in the last 85 years. I feel good that through my small video, her art form has become viral," she added. 

Facebook will introduce a new notification screen on its platform that will warn users if the article they are about to share is over 90 days old, the company announced on Thursday.

“We’re starting to globally roll out a notification screen that will let people know when news articles they are about to share are more than 90 days old,” Facebook wrote in a blog post.

The social media platform had previously introduced a context button in 2018 that provides information about the sources of articles in the News Feed. Building upon that, the new feature will inform users about the timeliness of the article.

“To ensure people have the context they need to make informed decisions about what to share on Facebook, the notification screen will appear when people click the share button on articles older than 90 days, but will allow people to continue sharing if they decide an article is still relevant,” Facebook said.

The social media giant stated that timeliness is important in understanding the context of an article and curbing the spread of misinformation on the platform.

“News publishers, in particular, have expressed concerns about older stories being shared on social media as current news, which can misconstrue the state of current events. Some news publishers have already taken steps to address this on their own websites by prominently labelling older articles to prevent outdated news from being used in misleading ways,” Facebook added.

Apart from this, the platform will also be testing a similar notification screen for information related to the global Covid-19 pandemic. The notification screen will provide information about the source of the link shared in a post if the link is related to information on Covid-19. It will also direct people to its previously introduced Covid-19 information centre for “authoritative” health information, it said.