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The US Embassy and Consulates' air quality monitors measure airborne fine particulate matter (commonly referred to as PM 2.5 because they are less than or equal to 2.5 microns in diameter) on the compounds of the Embassy and Consulates. Pixabay

If you are puzzled at the divergent data on air quality and the myriad numbers being thrown around, for those living in and around Delhi, it may be a good idea to get acquainted with the Air Quality Index (AQI) and the numbers behind it since bad air has become an annual fixture.

Under the American system, only PM 2.5 values are taken to determine the level of pollution and the AQI number. Under the American system, values above 500 are considered beyond the AQI.

The US Embassy and Consulates’ air quality monitors measure airborne fine particulate matter (commonly referred to as PM 2.5 because they are less than or equal to 2.5 microns in diameter) on the compounds of the Embassy and Consulates. The caveat is that data from a single monitoring station cannot be applied to an entire city.

The air quality data collected at the US Embassy and Consulates may differ from other monitors located in the same city.

Under the American system, only PM 2.5 values are taken to determine the level of pollution and the AQI number. Pixabay

Under the Indian computation, Central Pollution Control Board (CPCB) and Safar India give an index value for AQI which is a numerical scale used for reporting day-to-day air quality with regard to human health and the environment.

The CPCB launched AQI for effective communication of air quality status to people in terms which are easy to understand, and which transforms complex air quality data of various pollutants into a single number (index value), nomenclature and colour.

There are six AQI categories — good, satisfactory, moderately polluted, poor, very poor, and severe.

So, there is a singe AQI number or index value which CPCB puts out or Safar India, another official data source, puts out.

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AQ sub-index and health breakpoints are evolved for eight pollutants (PM10, PM2.5, NO2, SO2, CO, O3, NH3, and Pb) for which short-term (up to 24 hours) National Ambient Air Quality Standards are prescribed.

Apart from AQI, there is a count for major pollutants, PM 10 and PM 2.5 which are given separately by these monitoring and forecasting agencies.

In addition, there will be different AQI scores for different locations in a large metropolis like Delhi. For instance, at 5.15 p.m. on Friday, the AQI in Delhi at different locations varied from 450 in Vasant Vihar to a high of 643 in Siri Fort.

The AQI at different localities was mapped at Kalkaji (544), Okhla (553), Tughlakabad (588), Mundka (610), Punjabi Bagh (600) and Anand Vihar (602) — all with varying readings.

Under the American system, values above 500 are considered beyond the AQI. Pixabay

With the public health emergency being declared, experts say the announcement could have come earlier.

Tanushree Ganguly, Programme Associate, Council on Energy, Environment and Water said, “Delhi has been experiencing severe air quality conditions for the past four days and PM 2.5 levels have now exceeded 300ug/m3. While declaring a public health emergency today is definitely a welcome move, the announcement could have come earlier”.

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She said the authorities must consider lowering the threshold concentration needed for declaring an emergency so that vulnerable sections of the population are not exposed to such high concentrations of PM2.5. “Also, at such high levels of ambient concentration, the indoor air quality also gets worse”. (IANS)



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If humanity is hurt, God is hurt.

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Milky Way galaxy as seen from Chitkul Valley

NASA's Chandra X-ray Observatory has for the first time spotted signs of a planet transiting a star outside of the Milky Way galaxy, opening up a new avenue to search for exoplanets at greater distances than ever before.

The possible exoplanet -- or planets outside of our Solar System -- candidate is located in the spiral galaxy Messier 51 (M51), also called the Whirlpool Galaxy because of its distinctive profile, NASA said in a statement.

Astronomers have, so far, found all other known exoplanets and exoplanet candidates in the Milky Way galaxy, almost all of them less than about 3,000 light-years from Earth.

An exoplanet in M51 would be about 28 million light-years away, meaning it would be thousands of times farther away than those in the Milky Way, NASA said.

"We are trying to open up a whole new arena for finding other worlds by searching for planet candidates at X-ray wavelengths, a strategy that makes it possible to discover them in other galaxies," said Rosanne Di Stefano of the Center for Astrophysics at Harvard and Smithsonian (CfA) in Cambridge, Massachusetts, who led the study.

The findings are published in the journal Nature Astronomy.

The exoplanet candidate was spotted in a binary system called M51-ULS-1, located in M51. This binary system contains a black hole or neutron star orbiting a companion star with a mass about 20 times that of the Sun. The X-ray transit they found using Chandra data lasted about three hours, during which the X-ray emission decreased to zero.

Based on this and other information, the team estimates the exoplanet candidate in M51-ULS-1 would be roughly the size of Saturn and orbit the neutron star or black hole at about twice the distance of Saturn from the Sun.

The team looked for X-ray transits in three galaxies beyond the Milky Way galaxy, using both Chandra and the European Space Agency's XMM-Newton. Their search covered 55 systems in M51, 64 systems in Messier 101 (the "Pinwheel" galaxy), and 119 systems in Messier 104 (the "Sombrero" galaxy).

However, more data would be needed to verify the interpretation as an extragalactic exoplanet. One challenge is that the planet candidate's large orbit means it would not cross in front of its binary partner again for about 70 years, thwarting any attempts for a confirming observation for decades, NASA said.

Named in honor of the late Indian-American Nobel laureate, Subrahmanyan Chandrasekhar, the Chandra X-ray Observatory is the world's most powerful X-ray telescope. It has eight times greater resolution and is able to detect sources more than 20-times fainter than any previous X-ray telescope.

Known to the world as Chandra (which means "moon" or "luminous" in Sanskrit), Chandrasekhar was widely regarded as one of the foremost astrophysicists of the twentieth century. (IANS/JB)

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