Seventh Years: Lesson One

Professor Nakamura was ready, and a little bit excited. Seventh year was when things got really interesting, in his opinion. He waited for the students to enter before greeting them cordially. “Welcome to seventh year astronomy! My name is Professor Nakamura, and I’ll be teaching you for this semester.” He paused to smile, hoping he was being inviting. “For this evening’s subject, we turn to the sun and stars, and their composition. So please, take out your parchments and quills and get ready to take notes.” Professor Nakamura tapped on the blackboard and writing began to appear in neat print. He read the notes aloud in a clear yet obvious Japanese accent, blended interestingly with a New Zealand one.

Corona: Corona is the outermost layer of the sun. The only time it is visible is during an eclipse. It is very low density because it is a cloud of plasma with high transparency, unlike the inner layers. The corona is the extended atmosphere of the Sun, which has a volume much larger than the volume enclosed by the Sun's photosphere. A flow of plasma outward from the Sun into interplanetary space is the solar wind.

Chromosphere: The next layer of the sun, occasionally seen as a red circle on the outside of the sun. Concentration of hydrogen gives it its red colour. This area is much hotter than the next part of the Sun’s composition.

Photosphere: The visible surface of the Sun, the photosphere, is the layer below which the Sun becomes opaque to visible light. Above the photosphere, visible sunlight is free to propagate into space, and almost all of its energy escapes the Sun entirely. You can find out the composition, temperature, and pressure by analysing the colour spectrum of sunlight. A little side fact, helium was discovered by Norman Lockyer in 1868. He named it helium after the Greek God of the Sun Helio, 25 years later we were able to isolate helium here on Earth.

Convective zone: The Sun's convection zone extends from 0.7 solar radii (500,000 km) to near the surface. The thermal columns of the convection zone form an imprint on the surface of the Sun giving it a granular appearance called solar granulation at the smallest scale and supergranulation at larger scales.

Radiative zone: From the core out to about 0.7 solar radii, thermal radiation is the primary means of energy transfer. The temperature drops from approximately 7 million to 2 million kelvins with increasing distance from the core. This temperature gradient is less than the value needed for convection, which explains why the transfer of energy through this zone is by radiation instead of thermal convection.

The Core: the innermost 20-25% of the Sun's radius, where temperature (energies) and pressure are sufficient for nuclear fusion to occur.

“And that’s that for tonight, next lesson we will continue as we seem to have run out of time.” Professor Nakamura smiled once more as the students began to pack their things up. “Don’t forget to read the required chapters! It’ll help you for your exams,” he called out as everyone started to leave.
Aurora couldn’t believe she was in her final semester of school. So much had happened between when she’d first arrived and now, now it was almost over. That felt too unreal for her. Too unreal. In her mind she did still feel like the 11 year old who’d arrived, but she really wasn’t. The teen was now already considering pre-filling out the job application to be a healer. She knew that she had to manage this semester to get it, but Aurora felt pretty optimistic about her chances with it. The teen was getting herself together, gathering up books and notes, making sure she had everything she would need before she headed out of the room.

Aurora walked into the astronomy classroom and took her usual spot in the room. She glanced at the professor and knew she’d try to remember the man’s name though given this was her last semester she wasn’t sure that she would be able to. The gryffindor prefect nodded and looked to the board as the words appear. She began writing it down, making sure to get down all the parts which seemed important to note. She was focused on getting it down and then nodded as the lesson was wrapped up. She made sure to get down the required reading and then headed out of the classroom, intending to seek out her sister.

Users who are viewing this thread