Orbit of Chandrayaan-2’s lander lowered, one step closer to Moon landing

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.

Mumbai, Jan 19: After Kerala and Punjab, the Maha Vikas Agadi (MVA) government is also mulling over a resolution against the Citizenship (Amendment) Act, 2019 in Maharashtra Assembly.

Speaking to news agency, Congress spokesperson Raju Waghmare said: "Our senior party leader Balasaheb Thorat has also shared his stand on the CAA. Even Chief Minister Uddhav Thackeray has said that we are against the CAA. As far as the resolution against CAA is concerned, our senior leaders of MVA will sit together and decide."

If this happens, then Maharashtra will be the third state to pass a resolution against CAA, which grants citizenship to non-Muslim refugees from Pakistan, Afghanistan, and Bangladesh, who came to India on or before December 31, 2014.

Emphasising that CAA is 'unconstitutional,' senior lawyer and Congress leader Kapil Sibal has said that every state Assembly has the constitutional right to pass a resolution and seek CAA's withdrawal.

He added that it would be problematic to oppose the CAA if the law is declared to be 'constitutional' by the Supreme Court.

"I believe the CAA is unconstitutional. Every State Assembly has the constitutional right to pass a resolution and seek its withdrawal. When and if the law is declared to be constitutional by the Supreme Court then it will be problematic to oppose it. The fight must go on!" Sibal tweeted.

Earlier speaking at the Kerala Literature Festival on Saturday, the Congress leader had said that constitutionally no state can say that it will not implement the amended Citizenship Act, as doing so will be "unconstitutional".

Kerala government has also approached the Supreme Court against the CAA following the passage of a resolution against it in the state Assembly.

Punjab chief minister Amarinder Singh has also announced that the Congress state government is going to join Kerala in the Supreme Court in the case.

Tezpur (Assam), Mar 2: Seven boys, who had appeared for their class 10 board examinations, were apprehended on Sunday for allegedly raping and killing a 12-year-old girl in Assam's Biswanath district, police said.

The girl was hanged from a tree after the crime.

The incident happened on Friday in Chakla village under the jurisdiction of Gohpur police station, they said.

A senior police officer told PTI that the culprits, all of them High School Leaving Certificate (HSLC) examinees, were on the run, but were nabbed by a police team.

The accused after the examination had called the victim to a house on the pretext of organising a party and raped her, the officer said.

It is suspected that the girl was raped on Friday night and then hanged from a tree in a forest near the house, the senior police officer said.

The body was found on Saturday.