International Pulsar Timing Array
Pune-based National Centre for Radio Astrophysics (NCRA) hosted the ﬁve-day annual International Pulsar Timing Array (IPTA) meet in June
o The meet is a collaboration of radio astronomers from a dozen countries across the globe
Upgrade of the Giant Metrewave Radio Telescope (GMRT) in Pune and the Ooty Radio Telescope (ORT) has helped India meet the parameters for being a full member of the IPTA
International Pulsar Timing Array
IPTA is a collaboration of radio astronomers from a dozen countries across the globe. It uses more than 12 radio telescopes all over the world with an aim to detect ultra-low frequency gravitational waves (nano-hertz gravitational waves)
India has been an associate member (not a permanent member) of the IPTA since the last four years. But this is the ﬁrst time that we will be hosting the annual meeting.
Gravitational waves are disturbances in the space-time metric and are caused by the motion of mass in the universe
o They are a consequence of Einstein‘s theory of General Relativity, with their existence demonstrated through timing observations of double neutron star binaries
o Gravitation waves are like waves with a ripple effect just like the ripple effect we see when a pebble is dropped in a still pond. Instead of the up and down motion, the G
waves are like sound waves; they expand and compress
o These waves affect radio pulses from 10 km size stars called radio pulsars by changing ever so slightly the period of radio pulsation of these stars
o The ﬁrst gravitational waves detected by LIGO was a high frequency wave, while what IPTA is trying to detect has a frequency of about a billionth of a second
Pulsar Timing Array
It is a set of pulsars which is analysed to search for correlated signatures in the pulse arrival times
There are many applications for pulsar timing arrays. The most well known is to use an array of millisecond pulsars to detect and analyse gravitational waves
Pulsar is a highly magnetised rotating celestial object of very high mass that emits a beam of electromagnetic radiation
o The radiation can be seen when it points towards the earth as pulses of emissions, which appear with clockwise precision
o Hence they are the best celestial clocks
If there is a gravitation wave passing past the pulsar, there will be a blip or difference in the otherwise disciplined pulsars. By studying this variation over a period of time, we can determine a pattern in it.
3D X-ray map of Universe
A joint team of German-Russian scientists launched a space telescope named SpectrumRoentgenGamma (SRG), which will create a three-dimensional (3D) X-ray map of the universe and unveil unknown supermassive black holes, dark energy and stars.
The four-year mission will survey the entire sky eight times and track the evolution of the universe and dark energy — a mysterious repulsive force — that is accelerating its expansion.
It also aims to detect up to three million supermassive black holes — many of which are unknown — and X-rays from as many as 700,000 stars in the Milky Way. The telescope is the ﬁrst to be sensitive to highenergy ‗hard‘ X-rays and map the entire sky.
SRG will carry two independent X-ray telescopes:
o German-built eROSITA (Extended Roentgen Survey with an Imaging Telescope Array)
o Russian-built ART-XC (Astronomical Roentgen Telescope — X-ray Concentrator)
The SRG will also ﬁnd how dark matter — the main engine of galaxy formation — is spread in the universe
o It will, however, not detect gamma radiation
X-ray sky surveys have also been conducted by previous missions, but they were not able to map the entire sky
While Germany’s ROSAT mission in the 1990s was sensitive only to ‗soft‘ X-rays, with energies of about 2 keV, existing missions, such as NASA‘s Chandra X-ray Observatory and NuSTAR, can see high-energy radiation and resolve tiny details of cosmic structures. But, they see only small parts of the sky
SRG was ﬁrst proposed in 1987, but due to numerous developments like collapse of Soviet Union, end of NASA‘s space-shuttle programme, delayed it.
One of the novel ways being experimented to control dengue and chikungunya is to release mosquitoes infected with a bacteria, Wolbachia, which prevents replication of disease-causing virus in the guts of mosquitoes
o Now, Indian scientists have found that a strain of wolbachia naturally occurs in mosquito species, Ae. Aegypti, in South India
Wolbachia is shown to hinder the replication and dissemination of pathogens in mosquito besides, inducing reproductive abnormalities
o Therefore, researchers have been artiﬁcially infecting mosquitoes with wolbachia and exploring if such mosquitoes may be released to for controlling dengue
Though, the prevalence of wolbachia in Culex mosquito was detected in 1924, the wolbachia infection of Anopheles mosquitoes was detected only in 2014
Certain strains of wolbachia have proven efﬁcient to interfere with mosquitoes‘ biology thereby reducing virus transmission
o It is also safe to humans
Scientists have been trying to trans infect this bacterium into mosquito eggs artiﬁcially and release them. Mostly, the bacteria get expelled from the mosquitoes in subsequent generations, unless the infection happens in a natural way. So ﬁnding the natural occurrence of wolbachia strains in these mosquitoes is important
Wolbachiaint errupts viral replication in mosquitoes. This results in low viral concentration within mosquitoes, making them incapable of transmitting the disease
Sensors to Sniff out Explosives
A group of Indian scientists has now developed a new polymer-based ﬂuorescent optical sensor, which is a highly sensitive, selective and economically viable explosive detector.
The polymer material was synthesised using the Reversible Addition-Fragmentation ChainTransfer (RAFT) copolymerisation technique. The material — alanyl-based ﬂuorescent dansyl tagged copolymer (DCP) — exhibits yellow-green ﬂuorescence under ultra violet light and works on ‗quenching‘ of the emission.
o Quenching is a property wherein the usually electron-rich ﬂuorescent material transfers electrons — by photo-induced-electron-transfer — to an electron acceptor like the
nitroaromatics. When exposed to explosives, the copolymer loses its ﬂuorescent light intensity, indicating the presence of nitroaromatics
Nitroaromatics are industrial-class chemicals used widely in making dyes, pesticides and polymers
o They also form the primary compounds of explosives like Trinitrotoluene (TNT), which are hazardous chemicals, hard to detect, and pose civilian as well as military safety
It exhibits high sensitivity and selectivity towards nitroaromatic explosives like DNT, TNT and TNP in solution,even at extremely low concentrations. It is also effective in detecting the saturated vapours of these explosives
Conventional methods used to detect explosives involve employing sniffer dogs or sophisticated instruments, which are neither economical nor readily translated for ﬁeld use