For the second hour today, we watched a National Geographic video on black holes. As with the other time we watched a documentary, we stopped frequently so Jared could ask questions, which he did. The documentary mainly dealt with supermassive black holes (those that reside in the centers of galaxies), but the beauty of black holes is that – apart from the slope of the gravitational potential well – they 'behave' in the same way, regardless of if they're the monster black holes at the centers of galaxies or stellar remnants left behind after a supernova explosion.

We reviewed the evolution of stars much more massive than the Sun, from the point when they've consumed all their fuel. The 'onion ring' model shows us that all elements heavier than hydrogen and helium were produced in nuclear processes inside massive stars. When the star becomes unstable due to the cessation of fusion, the massive envelope collapses onto the iron core. Two things happen next: the intense gravitational field compresses the core even further, so it becomes either a neutron star or a black hole, depending on the initial mass of the star, and the outer envelope slams onto the core and then back into space, creating a supernova explosion.

We began, as we always do, with a brief review of the previous lesson, so I can test Jared's understanding of the topic. Considering we had a long break, and Jared had two lessons last time, I was impressed with how much he had retained and understood. I went into a bit more depth on the topic of white dwarfs, and then we transitioned to studying the deaths of stars much more massive than the Sun. They follow the same path from birth in a molecular cloud to the main sequence, but thereafter there are differences, most notably, more massive stars consume their fuel faster than stars like our Sun, and, due to their higher gravity, they can initiate carbon fusion in their cores. All the elements up to iron are thus produced. When a massive star has consumed all its fuel, it undergoes a catastrophic explosion that we call a 'supernova'.

In today's second lesson, we continued with the fate of stars like our Sun. Once the star becomes unstable and loses its outer layers after the red giant phase, what's left behind is a very dense object known as a white dwarf. White dwarfs are only about the size of our Earth, but matter is packed in so densely that one spoonful of 'white dwarf matter' weighs as much an elephant. Matter is no longer in the form that we are used to here on Earth, and we need to invoke the Pauli Exclusion Principle to understand how the atoms are packed in so tight. We again covered a lot of material, and even if Jared had to sit through two hours of class today, he remained attentive and inquisitive right until the end.

In the first of today's lessons, I started by quizzing Jared on what he had learned the day before regarding the structure of atoms, and how our understanding has progressed. We then reviewed the first stages of a star's life (birth in a molecular cloud, the fusion of hydrogen into helium for about 10 billion years for a star like our Sun). At the end stages, when the star has consumed all its fuel, it becomes unstable and puffs out into what we call a red giant. In 5 billion years, when our Sun will become a red giant, it will encompass Earth's orbit. Following this period, the outer layers of the star will vent into space, and the star enters the stage we call a planetary nebula. We looked at some images of different planetary nebulae, and discussed how the elements formed in the fusion processes inside stars are now contributing to the interstellar medium.

In order to understand the full importance of the fusion processes inside stars, and what role they play in the life cycle of the stars, we need to understand the fundamentals of the elements. So today we studied the periodic table and discussed how the order of the elements in the table is related to the number of protons in the nucleus. We also revisited the basic principles of the structure of the atom, and we touched upon the strong nuclear force.

Today we moved on to the structure and evolution of stars. We discussed the fusion processes inside stars like the Sun, and I explained how the radiation pressure resulting from fusion (hydrogen into helium, primarily) counteracts the gravitational pressure, and so we have a perfect sphere in equilibrium. Stars spend the majority of their lives (around 90%) on the 'main sequence', after their birth in a gas cloud. A star like the Sun is expected to live around 10 billion years, which is how long it takes for the fuel to run out (once most of the hydrogen has been converted to helium in its core). All stars can categorized according to temperature and luminosity, and when plotted will show a fairly tight correlation on the 'Hertzsprung-Russell diagram'.

I began by quizzing Jared on eclipses (his homework for the previous day had been to study the mechanics of eclipses). Jared appears to be very interested in eclipses, and considering a partial eclipse was scheduled for the early evening of Thursday, I thought it would be a good opportunity to examine the topic closely. We then moved onto star charts, and discussed the different types of objects represented in star charts. I also quizzed Jared on his understanding of the different objects.

We started class with Jared telling me what he had learned last night reading about constellations. He had researched the topic well, and was very eager to share what had struck him. He remarked upon the fact that most of the constellations appeared to have Roman and Greek names, and so we reviewed the genesis of modern astronomy in Greek and Roman times. We also discussed the legacy of the early Egyptian astronomers, in that the individual stars in the constellations are still known by their Arabic names today. We used star charts to study the constellations, and we started looking at stellar brightnesses. At the end of the lesson, it was Jared who reminded me that there will be a partial solar eclipse tomorrow!

We started discussing the birth of the stars by reviewing the processes that occur in gas/molecular clouds - clumps of gas condense and through gravitation and friction the gas ignites and a star is born (when enough mass has accumulated). We also started looking at star charts, for we will use them in future lessons when discussing stellar magnitudes. In so doing, we touched again upon ancient civilizations that first charted the skies, and thus understood the cyclical nature of 'time'.