March-2017 Colloquium

Date : 22-03-2017
Time : 16:00:00
Speaker : Dr. Kinsuk Acharyya
Reader, Planetary Sciences Division
Area : DEAN'S OFFICE
Venue : K. R. Ramanathan Auditorium, PRL

Abstract

Observations reveal that our Universe is surprisingly molecular. Molecules are found almost everywhere starting from the high-redshift galaxies to the nearby solar system. More than 200 different gas phase molecules and around 20 molecular species on the dust grain surface has been detected in the various astrophysical environments. Many of these molecules are organic, and therefore important astro-biologically. These molecules range in complexity from diatomic H2 to a 15-atom linear nitrile, HC13N, and many of these molecules are quite unusual by terrestrial standards. In the gas phase, H2 is the most abundant molecule by far, with CO in the second position, four order of magnitude lower. On the other hand, water dominates on the dust grain surface. More complex molecules are even less abundant – at least 4 to 10 orders of magnitude lower than H2. These molecules are very important because they could be the precursors of more complex biomolecules including simple amino acids, such as glycine. The possible molecular precursors of larger organic molecules, such as CH4, H2O, NH3, HCOOH, CH3COOH are all detected in the various astrophysical environments. Thus understanding how these molecules are formed in the variety of astrophysical conditions are of prime importance. This talk will discuss about how these molecules are formed and ongoing research work.

Date : 15-03-2017
Time : 16:00:00
Speaker : Dr. Priyanka Chaturvedi
Post Doctoral Fellow
Area : DEAN'S OFFICE
Venue : K. R. Ramanathan Auditorium, PRL

Abstract

A vast majority of observations of M dwarfs, of varying masses, have reported a higher radius by 10-20% than those predicted by the theoretical models. The mismatch of the radii as seen in these stars is termed as the 'M dwarf radius problem'. Studying M dwarfs in Eclipsing Binaries (EBs) with an aim to alleviate the M dwarf radius problem has been the motivation for the current research work. Mass measurements have been performed by Radial velocity observations using the high-resolution spectrograph, PARAS coupled with the 1.2 m telescope at Gurushikhar Observatory, Mount Abu, India. A software code, PARAS SPEC has been also developed to determine the stellar properties of the host star. I shall be briefly talking about this tool as well.

Date : 08-03-2017
Time : 16:00:00
Speaker : Dr. Naveen Chauhan
Scientist-SD
Area : DEAN'S OFFICE
Venue : K. R. Ramanathan Auditorium, PRL

Abstract

Nowadays luminescence has gained its place in different industrial and research areas. It is finding an important place in our everyday life and knowingly or unknowingly we are using materials possessing luminescent properties. In Geo-sciences it is widely used for the paleo-climatic studies, earthquake prediction, study of meteorites, evolution of deserts, Tsunami studies and other evolutionary studies. Luminescence dating is a radiation damage based method that utilizes the trapping of radiation induced charges in lattice defects and retaining some of these for geological timescales. In this method, the trapped charge concentration in a mineral is assumed to be zero at a time t=0 which later build up due to radiation exposure at a constant rate. This trapped charges can thus be probed via stimulated luminescence emission for estimating the radiation dose and hence the duration of exposure. In the present colloquium I will discuss the basics of luminescence technique, some of the issues which are being researched. I will also discuss ongoing research and instrumental development and the new program which are initiated in PRL.