Pune: A team of astronomers working at the National Centre for Radio Astrophysics here has discovered an extremely rare galaxy of gigantic size.
This galaxy — located about nine billion light years away — emits powerful radio waves, the researchers found.
Such galaxies with extremely large ‘radio size’ are called giant radio galaxies.
“Our work presents a case study of a rare example of a GRG (giant radio galaxy) caught in dying phase in the distant universe,” the researchers said.
This newly discovered galaxy known by its scientific identification ‘J021659-044920’ was discovered using the Giant Metrewave Radio Telescope (GMRT), an array of 30 fully steerable, 45-meter diameter antennas, spread out over a 30-km region around Khodad, near Narayangaon town of Pune district.
This project was led by Prathamesh Tamhane from the Indian Institute of Science Education and Research (IISER-Pune) working under the supervision of Yogesh Wadadekar at the National Centre for Radio Astrophysics.
While radio galaxies with size less than a million light years are common, giant radio galaxies are extremely rare, even more so, at large cosmic distances where only a handful has been discovered so far.
This newly discovered galaxy is the newest member of this elite group, the astronomers said.
The findings were detailed in the journal Monthly Notices of the Royal Astronomical Society.
New York, September 24, 2017: Researchers have found that some ultra-high energy cosmic rays that occasionally hit Earth come from a distant source outside the Milky Way.
Cosmic rays are atomic nuclei that travel through space at speeds close to that of light. Low-energy cosmic rays come from the Sun or from our own galaxy, but the origin of the highest-energy particles has been the subject of debate ever since they were first discovered fifty years ago.
Do they come from our Galaxy or from distant extragalactic objects?
The study published in the journal Science demonstrated that those cosmic rays with energies a million times greater than that of the protons accelerated in the Large Hadron Collider – the world’s largest and most powerful particle accelerator – come from much further away than from our own galaxy.
They were detected from 2004 to 2016 at the largest cosmic ray observatory ever built, the Pierre Auger Observatory in Argentina.
“We are now considerably closer to solving the mystery of where and how these extraordinary particles are created — a question of great interest to astrophysicists,” said Karl-Heinz Kampert from University of Wuppertal in Germany.
“Our observation provides compelling evidence that the sites of acceleration are outside the Milky Way,” Kampert who is spokesperson for the Auger Collaboration, which involves more than 400 scientists from 18 countries, said.
Cosmic rays are the nuclei of elements from hydrogen to iron. The highest-energy cosmic rays, those of interest in this study, only strike about once per square kilometre per year — equivalent to hitting the area of a soccer field about once per century.
Such rare particles are detectable because they create showers of secondary particles — including electrons, photons and muons – as they interact with the nuclei in the atmosphere.
These cosmic ray showers spread out, sweeping through the atmosphere at the speed of light in a disc-like structure, like a dinner plate but several kilometres in diameter.
At the Auger Observatory, the shower particles are detected through the light they produce in several of 1,600 detectors, spread over 3,000 square kilometres of western Argentina and each containing 12 tons of water.
Tracking these arrivals tells scientists the direction from which the cosmic rays came.
After racking up detections of more than 30,000 cosmic particles, the scientists found one section of the sky was producing significantly more than its share.
The probability of this happening by a random fluctuation is extremely small, the scientists said — a chance of about two in ten million.
“This result unequivocally establishes that ultra-high energy cosmic rays are not just random wanderers of our nearby universe,” Paolo Privitera of University of Chicago who heads the US groups participating in the project, said. (IANS)
Researches in Japan have discovered a super-massive black hole in Milky Way Galaxy
The black hole is believed to weigh as much as 400 suns
According to studies, at least 100 million of these small black holes should exist in the Milky Way
Japan, September 5, 2017 : Astronomers have found new evidence for the existence of a mid-sized black hole, considered the missing link in the evolution of super-massive black holes.
Astronomers in Japan found the possible black hole in our own Milky Way galaxy, a long-theorized object which is bigger than the small black holes formed from a single star, but still much smaller than giant black holes such as the one at the center of the Milky Way.
Black holes are difficult to find because they do not emit any light. However, scientists can detect them by their influence on nearby objects.
The astronomers in Japan found new evidence of the so-called intermediate-mass black hole when they turned a powerful telescope in Chile’s Atacama desert on a gas cloud near the center of the Milky Way. The gases in the cloud move at unusual speeds, and the scientists believed they were being pulled by immense gravitational forces. They say the gravitational force is likely caused by a black hole measuring about 1.4 trillion kilometers across.
The findings are published in the journal Nature Astronomy.
Theoretical studies predict at least 100 million of these small black holes should exist in the Milky Way, however only about 60 have been found.
The possible mid-sized black hole is much smaller than the super massive black hole that is located in the center of the galaxy, known as Sagittarius A, which weighs as much as 400 million suns.
“This is the first detection of an intermediate-mass black hole candidate in the Milky Way galaxy,” said the study’s leader, Tomoharu Oka from Keio University, Japan.
If confirmed, the intermediate-mass black hole could help explain how supermassive black holes operate. One theory is that supermassive black holes, which are at the center of most massive galaxies, are formed when smaller black holes steadily coalesce into larger ones. However, until now no definitive evidence has existed for intermediate-mass black holes that could indicate a middle step between the small and massive black holes already detected.
Researchers say they will continue to study the intermediate-mass black hole candidate in the hope of confirming its existence. (VOA)
LONDON, Sept 08, 2016: An international team of researchers has found that a stellar system classified as a globular cluster for the 40-odd years since its detection actually has properties uncommon for a globular cluster that make it the ideal candidate for a living fossil from the early days of the Milky Way.
The cluster, known as Terzan 5 — 19,000 light-years from Earth- harbours stars of hugely different ages — an age-gap of roughly seven billion years and bridges the gap in understanding between our galaxy’s past and its present, the study said.
“Such galactic fossils allow astronomers to reconstruct an important piece of the history of our Milky Way,” explained lead author of the study Francesco Ferraro from University of Bologna in Italy.
While the properties of Terzan 5 are uncommon for a globular cluster, they are very similar to the stellar population which can be found in the galactic bulge, the tightly packed central region of the Milky Way.
These similarities could make Terzan 5 a fossilised relic of galaxy formation, representing one of the earliest building blocks of the Milky Way.
“Terzan 5 could represent an intriguing link between the local and the distant Universe, a surviving witness of the Galactic bulge assembly process,” Ferraro said.
The team scoured data from the Advanced Camera for Surveys and the Wide Field Camera 3 on board Hubble, as well as from a suite of other ground-based telescopes.
They found compelling evidence that there are two distinct kinds of stars in Terzan 5 which not only differ in the elements they contain, but have an age-gap of roughly seven billion years.
The ages of the two populations indicate that the star formation process in Terzan 5 was not continuous, but was dominated by two distinct bursts of star formation.
“This requires the Terzan 5 ancestor to have large amounts of gas for a second generation of stars and to be quite massive. At least 100 million times the mass of the Sun,” co-author of the study Davide Massari from National Institute for Astrophysics (INAF) , Italy.