Speaker
Description
The Hubble's Constant (H0)is one of the most fundamental and essential cosmological parameters which gives the expansion of Local Universe. Hubble’s Constant is measured by different methods and one of them is by using electromagnetic sources called distance ladder. With the detections of gravitational waves and using Gravitational Wave (GW) analysis this value can be measured; making GW sources another significant method to act as standard sirens with their electromagnetic counterparts from their host galaxy and adding to the accuracy. The GW event GW 170817 which was the result of the merger of two neutron stars helped to find H0. The corresponding counterpart electromagnetic event was recorded from the host galaxy NGC4993. The GW170817 event is considerable success in measuring the value of universe acceleration close to the value H0 = 70.0+12.0 −8.0 kms−1 Mpc−1. These results from GW170817 event are compared with the other observations which are done by methods involving CMB and Cosmic Distance Ladder. The H0 is also calculated from the data of another GW event GW19081, which is the merger of Compact Binary Coalescence involving a 22.2 – 24.3 Solar Masses Blackhole and a compact object with a mass of 2.50 – 2.67 Solar Masses. The EM counterpart of this event is unknown so far and hence the event is named Dark Siren. The GW merger event GW190814 gives a different value for H0. The Hubble’s value calculated from the data of GW190814 is close to H0 = 75+59 −13 km s−1Mpc−1 . There have been many other GW detections and they fit closely to the General Relativity. But these all detections are further adding to the different values of H0 thus escalating the Hubble's Tension. However, with further development in the technology and more GW events to be recorded in the coming future, we suppose the uncertainty limits will reduce.
