The habitable zone
The habitable zone, also known as the “Goldilocks zone,” is the region around a star where conditions may be just right for the existence of liquid water on a planet’s surface. Liquid water is considered a key ingredient for the emergence of life as we know it, so the habitable zone is often seen as a promising target for the search for extraterrestrial life.
In our solar system, the habitable zone is defined as the region around the Sun where the temperature is just right for liquid water to exist on a planet’s surface. This region extends roughly from the orbit of Venus to the orbit of Mars. Venus is too close to the Sun and has a runaway greenhouse effect that has made its surface too hot and inhospitable for life as we know it. Mars, on the other hand, is farther from the Sun and has a thin atmosphere, which has caused its surface to become too cold and dry for liquid water to exist in significant quantities. However, it’s possible that Mars may have had liquid water on its surface in the past, and that microbial life could have emerged and possibly even persisted underground.
Nuclear Fusion in the sun
Nuclear fusion in the sun is an incredibly powerful process that generates an enormous amount of energy. In fact, the amount of energy produced by fusion in the sun is what makes life on Earth possible.
Scientists estimate that the sun loses about 4 million metric tons of mass every second due to the energy produced by nuclear fusion. This may seem like a lot, but it’s actually a very small fraction of the sun’s total mass, which is about 2 x 10^30 kilograms.
picture from NASA 2014
In the sun, the primary fusion reaction is the fusion of hydrogen nuclei (protons) into helium. This process is known as the proton-proton chain reaction. It occurs in the sun’s core, where temperatures are high enough to overcome the electrostatic repulsion between the positively charged protons.
Historical Astronomers in Context
Johannes Kepler (27 Dec 1571 – 15 Nov 16)
Two events that took place during Kepler’s lifetime:
1) 1571 – Battle of Lepanto, in which the Holy League defeated the Ottoman navy.
2) 1618 – The Thirty Years War begins in Europe.
Kepler’s chief and most well-known contribution were the three laws of planetary motion, also referred to as Kepler’s Laws.
Kepler also produced some of the first reliable estimates of the distances between the earth and the Sun.
His other major contribution was the telescopic discovery of moons around Jupiter with the telescope he invented himself.
My personal reflections:
I found it interesting because in the past I learned the history separately. My teacher or the textbook often categorizes historical events with respect to their geological location, not the time they took place. So, it is interesting to realize that these things happened at a close period. And it is astonishing that in the same era, some countries are having fights, and some countries are living in peace. And to be honest, my history grade was not high back in high school, so I just realized how early astronomers calculated the distances in our solar system, though not that accurately.
The Galilean Moons
The Galilean moons, or Galilean satellites, are the four largest moons of Jupiter: Io, Europa, Ganymede, and Callisto. They were first seen by Galileo Galilei in December 1609 or January 1610, and recognized by him as satellites of Jupiter in March 1610. They were the first objects found to orbit a planet other than the Earth.
This was a photo taken by myself using an unprofessional telescope, there should be four Galilean satellites, but in this picture there is only three. The one on the right lower corner was an optical illusion of Jupiter itself. It is not the telescope’s problem, in fact, it is my phone camera’s fault.
Hi! My name is Tianyou Xie, you can call me Bill.
I’m in the class of 2026 and I came from China
This is a picture of me and my cousin, I’m the one on the right.
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