The lecture series on Astronomy started off on August 22 with a wonderful inaugural lecture on “Demoting Pluto: After one year” by Dr. Aniket Sule, one of the eminent astronomers of today’s time and a member of Khagol Mandal. This lecture was attended by about 40 people, seeking answers to numerous questions about this celestial body which is no more a part of our Solar System.

Dr. Sule began the lecture with a basic idea of ‘size’ when we talk about huge celestial bodies. The initial introduction itself made everyone realize how ordinary our Sun is and how even smaller Pluto is. The size being one of the major factors in the objections raised against Pluto, this explanation laid a foundation of the lecture. Then came a brief visit to our Solar System since the ancient times and how it gained each of its members that we know today.

With a base of fundamental knowledge about our Solar System, Dr. Sule moved on to the actual topic for the day: Pluto and its subsequent demotion. He talked about the initial predictions made about it and how those predictions proved to be a result of sheer coincidence later. The credit of accurate prediction of Pluto’s position goes to American astronomer Clyde Tombaugh who discovered it in 1930.

Then coming down to the fundamental question: “What’s wrong with Pluto?” Dr. Sule went on to explain the oddity in various features of Pluto like the inclination of its orbit, the size ratio of Pluto with other satellites in Solar System and also its own satellite. Later, some new bodies in the kuiper belt were discovered. It was found that some of the bodies called as Kuiper Belt Objects (KBOs) also have larger diameter than Pluto. Discovery of Sedna and Xena (2003 UB313) and consequent study of their orbits chiefly compelled the scientific community to seriously consider this issue.

Further Dr. Sule explained how the need of defining what a planet was realized and how International Astronomy Union kicked off with an organized debate over this matter. Dr. Sule was himself present at this assembly and he gave a lively account of everything that happened there! The hot topic was taken on an anvil in 26^th General Assembly where a primary poll was conducted and looking at the result, the first draft of the definition was prepared. This draft faced many objections and was rejected unanimously. Naturally, IAU came up with second resolution for the definition of ‘planet’. Even this second resolution was rejected and ultimately, IAU decided to hand over the charges into third party’s hands in order to have an unbiased debate. Third resolution was drafted and it was presented by Prof. Jocelyn Bell to the assembly.

In the end, the various terms like planet, dwarf planet, satellites etc. were delineated precisely and the issue was resolved. On a last node, Dr. Sule shed light on consequences of demotion of Pluto. He concluded the lecture with some funny cartoon sketches which depicted the reactions of people on this matter, all over the world. The lecture was followed by a brief interaction session which gave voice to questions on other topics in astronomy.

Discussion on "Phoenix mission" and "Magnitude of binary system"

On Wednesday, 8th August we discussed about the recent launch of the mars mission “Phoenix”. Sukhada gave the statistics and the information about the mission. Nasa launched it on 4th August. Previous rovers Opportunity and Spirit were lost in the Martian storm. Due to this NASA named the mission as Phoenix. Phoenix will take 10 months to reach the planet. The lander will land on the polar region and will search the soil for water content, minerals and organic compounds which will unveil the history of the planet Mars. The lander has 8 special ovens which will heat the collected sample upto 1000 degree Celsius and will analyze it with the spectrometers. The discussion ended with one unanswered question; “What is the mode of Energy used to create such high temperatures in the Oven? Can the Solar panels be sufficient enough to generate the high temperature?”

Then Jayshree raised one question; “If we have a binary star system and we know the apparent magnitude of both the stars then how can we calculate the total magnitude of the system?” Sukhada said that the magnitude cannot be add up or the total magnitude cannot be the average of the two. Noone was having the idea or the formula to calculate the total magnitude of the system. Bhide kaka told that, “The magnitude will differ if the stars are revolving in such a way that one star comes in between us and the other star i.e. the pair is the eclipting binary system. Also the distance between the two stars will matter in the calculation.” He gave the example of galaxies. Though galaxies contain billions of stars we are seeing galaxies very faint as the individual stars brightness will not just add up to give the total brightness of the galaxy but their inter stellar distances will affect the summation of their brightness and what we see is the very faint galaxy than a bright patch.

Lecture on New Advances In Optical Astronomy

On Saturday, 4th August there was a lecture arranged by the Nehru science centre, Mumbai. Nehru Science centre is going to conduct a lecture series “Vistas In Astronomy” and Saturday’s lecture was the inaugural lecture. The topic was “New Advances in Optical Astronomy”. Prof. Ram Sagar, Director of Aryabhatta Research Institute
of observational SciencES (ARIES) was the honorable speaker for the lecture. The ARIES is situated in the high altitude Manora peak of Nainital. ARIES has 4 giant telescopes and it is building a 3.6 m huge telescope in the Devasthal near Nainital.

In his speech Prof. Ram Sagar briefly discussed different kinds of telescopes (detectors) used for the different wavelengths of light. Then he gave the statistics differentiating the abilities of human eye and telescopes and discussed the need of having bigger aperture for light gathering. He also discussed the difference in ground based telescope and a satellite telescope and mensioned the new techniques implemented to overcome the difficulties like air turbulence. He described the new technique of auto correcting the curvature of large diameter telescopes used with comparatively less thickness. This technique has decreased the cost of building the large diameter telescopes. Then he described the advantages of using photographic plate over human eye and the charge coupled devices (CCD’s) over the photographic plates.

After he finished his lecture I asked him the first question: “Why the interferometry is not yet been used effectively with optical telescopes?” On this question he gave the answer as, “The incoherence in the coming beam of light is the main problem implementing the interferometry in the optical region. In radio interferometry we are working on the specific wavelength and hence the problem does not occur. But in case of optical observations we are dealing with a band of spectrum and hence we have to take into consideration the incoherence.”

The overall lecture was very good and informative. The response to the lecture was also very good. From Khagol Mandal, I, Anup, Nilesh, Sameer, Jay, Vikrant, Anshulee, Akshaya, Vineeta and Juie attended the lecture.