What is a Galaxy?

Galaxies are enormous conglomerations of stars and interstellar material. The qualifying morphological properties of these objects, however, remain flexible due to two principal factors: continuity and irregularity.

Note: What is a Galaxy?

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Basics of Calculus

This is a one-page note on the basics of calculus. Introduction to the study of change, Differential Calculus, Integral Calculus, Fundamental Theorem of Calculus, formula of Newton and Leibnitz. Full note in PDF.

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On the White Dwarf Mass Limit and S. Chandrasekhar

Subrahmanyan Chandrasekhar (1910–1995) was born into a Brahmin family in Lahore, then India. At the age as early as 21, he was responsible for deriving a theoretical mass limit an ideal white dwarf star can achieve without collapsing in on itself, now referred to as the Chandrasekhar limit, and accepted at 1.39 M⊙. This was one of the most important discoveries in the 20th century as it paved the way for better understanding of the processes occurring during the collapses of degenerate stars that may lead to such phenomena as black holes—ingredients crucial for the development of our modern cosmological theories.

Note: On the White Dwarf Mass Limit and S. Chandrasekhar

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Stellar-Mass Black Holes

Stellar-mass black holes are the result of a gravitational collapse of a massive star at the end of its life. The core of such star collapses to singularity – a point of infinite density and space-time curvature – that is cloaked in the event horizon. The gravitational force of the resulting black hole is so strong that no light or signal can escape its event horizon. This essay will address how astronomers search for stellar-mass black holes, will attempt to describe their characteristics, and will also discuss the current knowledge on Milky Way black hole candidates and their companion stars, and the connection between X-ray sources and black holes.

Essay: Stellar-Mass Black Holes

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150 Years Ago Today… Note on the Variable Nebula in Taurus

gbobs

Tracing the origins of the discovery and the development of observations of NGC 1555, also referred to as the Hind’s Variable Nebula in the constellation Taurus, reveal an interesting story of how a faint glow in the sky became on the most discussed objects in the sky.

Essay: 150 Years Ago Today... Note on the Variable Nebula in Taurus

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NGC 4755: Color-Magnitude Diagrams (CMDs) and Zero-Age Main Sequence Luminosities

The CMD submitted in the previous fortnight shows members of NGC 4755 – an open cluster in Crux. The stars were selected in the SIMBAD database as they all belong to the cluster - all at more or less the same distance, and this simplifies working with apparent mag- nitudes that are available in the database.

Note: NGC 4755: Color-Magnitude Diagrams (CMDs) and Zero-Age Main Sequence Luminosities

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The Importance of Astrology for the Development and Survival of Astronomy During Medieval Times

As an amateur astronomer, I was to an unnecessary degree opposed to the concept of astrology, especially if questioned about its scientific impact. The more I progress through the history course at Swinburne, the more I realize how naive that position was. It is too easy to underestimate the contributions of astrology from the pinnacles of modern astrophysics and freedom of thought, especially after it has been decoupled from the mainstream science.

Note: Importance of Astrology for the Development and Survival of Astronomy During Medieval Times

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