First stars that formed after Big Bang identified
London, May 17: Japanese scientists have identified some of the first stars to form in the Universe just 250 million years after the Big Bang, according to a study published in Nature magazine.
Using the giant ALMA telescope in Chile, researchers were able to observe the distant galaxy MACS1149-JD1 when it was just 550 million years old, a time when it contained stars that were about 300 million years old, the study published on Wednesday said.
The galaxy's "red shift," a measurement technique that shows the distance to, and the age of astronomical objects, which was determined to be 9.1096, the largest value ever detected to date using spectral line analysis, Efe news reported.
The Japanese researchers arrived at that red shift measurement using the spectral lines of ionized oxygen insted of using ionized carbon, as is normally done in examining distant objects.
The results demonstrate the usefulness of ALMA as a tool for measuring the red shift of distant galaxies, Rychard Bouwens, an astrophysicist at Leiden University, said in another article in Nature.
The work of Takuya Hashimoto and his group at Osaka Sangyo University sheds light on the formation of the first stars and suggests that future telescopes - such as the James Webb Space Telescope, which will replace the Hubble 'scope in orbit starting in 2020 - could find new evidence on the formation of first-generation stars, Bouwens said.
Scientists believe that the Universe's first stars formed in regions of very dense matter, although understanding of that process is still limited.
Bouwens emphasised that it was still not clear whether the stellar activity detected in MACS1149-JD1 occurred in other regions in the early Universe, but he added that the discovery would spur similar studies of other galaxies.
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Delhi's air quality worst in country, hits 'severe' for first time this season
New Delhi, Nov 13: Delhi recorded the country's worst air quality on Wednesday as it turned 'severe' for the first time this season, with the AQI soaring to 418.
Bihar's Hajipur, with an Air Quality Index (AQI) of 417, had the the second-worst reading in the country, Central Pollution Control Board (CPCB) data showed.
Of Delhi's 36 monitoring stations, 30 reported air quality in the 'severe' category, the CPCB said.
In comparison, the national capital's 24-hour average AQI -- recorded at 4 pm every day -- stood at 334 on Tuesday.
An AQI between zero and 50 is considered 'good', 51 and 100 'satisfactory', 101 and 200 'moderate', 201 and 300 'poor', 301 and 400 'very poor', 401 and 450 'severe' and above 450 'severe plus'.
According to the CPCB data, the city's AQI was in the 'severe' category for three days in January.
On January 14, the AQI was recorded at 447, followed by 409 each on January 24 and 26.
The CPCB said 'severe' AQI affected healthy people and seriously impacted those with existing medical conditions.
The air quality in the national capital had been in the 'very poor' category since it plunged to the level on October 30.
According to the Centre's Decision Support System for Air Quality Management, vehicular emission was the top contributor to Delhi's pollution, with an estimated share of approximately 13.3 per cent.
The other prominent pollutants were PM2.5 and PM10.
PM2.5 and PM10 refer to fine particulate matter in the air, with the numbers indicating their size in micrometres.
PM2.5 are fine particles with a diameter of 2.5 micrometres or less, about the width of a human hair. These are so small that these can penetrate deep into the lungs and even enter the bloodstream, posing significant health risks.
PM10 are coarser particles with a diameter of 10 micrometres or less, about the width of 10 human hairs. While not as concerning as PM2.5, these can still irritate the airways and worsen respiratory problems.
Long-term exposure to these particulate matter can increase the risk of heart disease.
