Astronomy. My first Year Notes
written by Kirstie Calderon Lewis
My own notes of Astronomy First Year lesson 1 - 9. All notes from the lessons and my own work on Astronomy. Important information for quizzes and essays can be find within the notes.
Last Updated
05/31/21
Chapters
9
Reads
916
Lesson Eight
Chapter 8
Comets
• Discuss the bodies in the solar system that are smaller than the planets: comets, meteors, asteroids, and dwarf planets.
• A comet is a small body that’s composed of water ice in addition to various other ices, like frozen methane and carbon dioxide, as well as rock and dust.
• Sizes range from a few hundred meters to tens of kilometres.
• Passes close enough to the Sun, it gets warm enough that the ice melts and evaporates into an atmosphere, called the coma consisting of gas and dust.
• The remaining solid part of the comet, meanwhile, is called the nucleus.
• The light and radiation from the Sun actually exert a pressure that, along with the solar wind, can push this atmosphere away from the comet, forming a tail or two: one of gas and one of dust.
• Most comets originate far from the Sun.
• Some of them get pulled into orbits that come close to the Sun by the gravity of one of the planets or, for those extremely far away from our solar system, by a passing star.
• Typical direction of tails during a comet's orbit near the Sun.
• Most famous comet, Halley’s Comet, was named after Edmond Halley, the English astronomer who, in 1705, discovered its period of about 75 years.
• The space rock has been observed several times since 240 B.C.E.
• It can be seen with the naked eye every time it comes close to the Sun. The last time it was seen was in 1986.
• More spectacular when its next returns in 2061.
• Another famous comet is the Hale-Bopp Comet. Discovered on July 23, 1995 by two American observers, Alan Hale and Thomas Bopp. Its dust tail extended 40 to 45 degrees across the sky. Its closest approach to Earth, on March 27, 1997, was 1.315 A.U.
• Magical properties? Muggles used to think that they announced, and maybe even foretold, the violent death of one or more high-status people. There was a bright comet in the sky when the Roman emperor Julius Caesar was stabbed to death, and a connection was made between the comet and the assassination.
• Since all celestial bodies reflect solar magic towards us and comets can get extremely bright, it seemed reasonable to suppose that they would reflect a lot of magic our way.
• Halley’s Comet last visited Earth’s neighbourhood in 1986, there was plenty of excitement within the magical astronomical community, and a lot of magical research relating to the comet was performed and published.
• The magical newspapers covered the arrival of the comet in great detail: they exaggerated the theories published by the researchers and presented them as established facts.
• We now know why no magic accompanied Halley’s comet: its brighter tail was made of water vapour, which transmits rather than reflects solar magic, and its dust tail was too sparse and its nucleus too small to reflect a noticeable amount of magic from so far away.
• Eight years after Halley’s Comet’s last sighting, Voldemort returned, and more and more people, some of whom were of high status, suffered a violent death.
• Their suspicions were strengthened when a great many witches and wizards met a violent death during the Battle of Hogwarts, a few short months after the closest approach of Hale-Bopp.
Meteors, Meteoroids and Meteorites
Meteors
• Commonly known as shooting stars
• Caused by a small object entering the Earth’s atmosphere where it is heated by friction until it becomes incandescent, leaving a trail of glowing particles behind it.
• Usually you can see one or two meteors an hour.
• Few times a year a lot more of them can be seen in that space of time, sometimes hundreds of them. Called a meteor shower.
• The trails all seem to come from the same point in the sky, called the radiant.
• A meteor shower is named after the constellation in which the radiant is seen.
• What causes a meteor shower? When a comet is heated by the Sun, it leaves behind a trail of gas and dust. If the comet’s path intersects the Earth’s orbit, the Earth will pass through the trail of dust every year, and the dust particles will enter the Earth’s atmosphere and produce a meteor shower.
• How can you find out in advance when one will occur? Many sources that will tell you when to look for one. In those sources you will see the terms Right Ascension (RA) and Declination (Dec).
Meteoroids and Meteorites
• The objects that cause meteors are called meteoroids. Most of them are about the size of a grain of sand and vaporize entirely in the atmosphere, but occasionally one comes along that is large enough to survive and hit the ground, and then it’s called a meteorite.
• A meteoroid remains chemically pristine in space; if it lands and becomes a meteorite, only the surface gets contaminated with earthly material, while the rest of it is made up of the same stuff as the early solar system.
• Its interior can be analysed to discover what the solar system used to be made of.
• A meteorite is identified as having come from another planet or some other body, most often Mars or the Moon.
• These objects can give valuable information about the chemical composition of the bodies.
• If the impact of a meteorite is energetic enough, it will leave a crater - a hole in the ground that’s much bigger than the object that created it. Planets and satellites without a thick atmosphere or active geological processes remain covered with craters from such impacts. Small craters on Earth are soon eroded away by wind and rain, or shifting plate tectonics, but the largest of them remain visible for quite some time, leaving evidence that a big impact occurred sometime in the past.
• Magical properties of Meteorites? They certainly do, since they are made of the same magical stuff that formed the early solar system.
• This magic is wild and unpredictable, and it interferes with any magic we do.
• Wilbur van Snobbe. He found a half-buried meteorite and tried to cast the Summoning Charm to unearth it so that he could sell it to a museum. The spell missed its target and hit a nearby rock, which flew up and hit him on the head instead of landing at his feet, the destination on which he had concentrated. He rushed to the spot where he had found the meteorite, with the intention of trying once again to unearth it with his wand. His wizardly pride was rudely shattered when he saw a Muggle in the process of unearthing it with the appropriate tool for the job: a shovel.
Asteroids
• An asteroid is like a meteoroid, only bigger – that is, more than 100 meters across. The largest known asteroid, Ceres, is almost 1000 kilometres in diameter.
• Asteroids differ from comets in that they never acquire an atmosphere, because they don’t have any ices to evaporate if they pass close to the Sun.
• They are divided into three groups depending upon what they’re primarily made of: carbon-rich, stony, and metallic.
• Asteroids come in many shapes and sizes, but the largest ones are round because their gravity moulds them into spheres.
• Asteroids come in many shapes and sizes, but the largest ones are round because their gravity moulds them into spheres.
• Ida, the first asteroid to be discovered with a moon. As you can see, it is far from being round.
• Most asteroids are located in the asteroid belt, which is between the orbits of Mars and Jupiter.
• Some are closer to the Sun, and of those, a few come close enough to Earth to be called near-Earth asteroids. Astronomers keep a close watch on near-Earth asteroids because there is always the chance that one of them could hit Earth or explode nearby, with results ranging from mildly dangerous to catastrophic.
Dwarf Planets
• A dwarf planet isn’t just a smaller version of a planet: the term doesn’t refer to size but to criteria decided upon by the International Astronomical Union in 2006.
• Pluto, discovered in 1930, was long considered to be the solar system’s ninth planet. But in 2005, a body was discovered that is about the same size as Pluto; it was named Eris. In 2006, the International Astronomical Union (IAU), concerned that future discovery of many such objects would lead to a proliferation of planets, decided a modification of what we call a planet was needed. This change would narrow the definition to exclude numerous bodies like Pluto and Eris. Thus, they invented the term dwarf planet to describe such objects.
• According to the new definition, a planet has to satisfy three conditions: 1) It orbits the Sun or another star, rather than another body. 2)It has enough self-gravity for its shape to be nearly spherical. 3) It has cleared its orbit of space debris.
• An object that satisfies the first two conditions but not the third one is now deemed a dwarf planet. Five bodies are currently classified as such and were so classified in the following order: Pluto, Eris, Ceres (also the largest known asteroid), Haumea (which is elongated because it rotates so fast), and Makemake.
• Pluto has five moons. Charon, Styx, Nix, Kerberos, and Hydra
• Ceres has no moons.
• Haumea has two moons, Namaka and Hi’iaka
• Eris has one moon, Dysnomia.
• Makemake has one moon, not yet named. Nicknamed MK 2
• All dwarf planets, except for Ceres orbits are in the Kuiper belt. A region of space outside of Neptune’s orbit, although Pluto occasionally comes closer to the Sun than Neptune’s path.
• The Kuiper belt contains a lot of bodies, some of which are almost as big as Pluto, and the more space debris there is near the orbit of an object, the harder it is for that object to clear it. If Pluto had been located in an emptier part of the solar system, it might still be called a planet. Pluto got demoted not because of its own properties, but because it was unlucky enough to be in a part of the solar system with a lot of debris around it, which, in some people’s opinion, is not a valid criterion for demoting it. Other people argue that limiting the growth of the number of planets is indeed a valid reason for demoting Pluto.
• Like the planets and the Moon, the dwarf planets do reflect magic to Earth. Pluto’s magic, which is just barely detectable. The other dwarf planets are either too small or too far away for their magic to have any noticeable effect here.
• Discuss the bodies in the solar system that are smaller than the planets: comets, meteors, asteroids, and dwarf planets.
• A comet is a small body that’s composed of water ice in addition to various other ices, like frozen methane and carbon dioxide, as well as rock and dust.
• Sizes range from a few hundred meters to tens of kilometres.
• Passes close enough to the Sun, it gets warm enough that the ice melts and evaporates into an atmosphere, called the coma consisting of gas and dust.
• The remaining solid part of the comet, meanwhile, is called the nucleus.
• The light and radiation from the Sun actually exert a pressure that, along with the solar wind, can push this atmosphere away from the comet, forming a tail or two: one of gas and one of dust.
• Most comets originate far from the Sun.
• Some of them get pulled into orbits that come close to the Sun by the gravity of one of the planets or, for those extremely far away from our solar system, by a passing star.
• Typical direction of tails during a comet's orbit near the Sun.
• Most famous comet, Halley’s Comet, was named after Edmond Halley, the English astronomer who, in 1705, discovered its period of about 75 years.
• The space rock has been observed several times since 240 B.C.E.
• It can be seen with the naked eye every time it comes close to the Sun. The last time it was seen was in 1986.
• More spectacular when its next returns in 2061.
• Another famous comet is the Hale-Bopp Comet. Discovered on July 23, 1995 by two American observers, Alan Hale and Thomas Bopp. Its dust tail extended 40 to 45 degrees across the sky. Its closest approach to Earth, on March 27, 1997, was 1.315 A.U.
• Magical properties? Muggles used to think that they announced, and maybe even foretold, the violent death of one or more high-status people. There was a bright comet in the sky when the Roman emperor Julius Caesar was stabbed to death, and a connection was made between the comet and the assassination.
• Since all celestial bodies reflect solar magic towards us and comets can get extremely bright, it seemed reasonable to suppose that they would reflect a lot of magic our way.
• Halley’s Comet last visited Earth’s neighbourhood in 1986, there was plenty of excitement within the magical astronomical community, and a lot of magical research relating to the comet was performed and published.
• The magical newspapers covered the arrival of the comet in great detail: they exaggerated the theories published by the researchers and presented them as established facts.
• We now know why no magic accompanied Halley’s comet: its brighter tail was made of water vapour, which transmits rather than reflects solar magic, and its dust tail was too sparse and its nucleus too small to reflect a noticeable amount of magic from so far away.
• Eight years after Halley’s Comet’s last sighting, Voldemort returned, and more and more people, some of whom were of high status, suffered a violent death.
• Their suspicions were strengthened when a great many witches and wizards met a violent death during the Battle of Hogwarts, a few short months after the closest approach of Hale-Bopp.
Meteors, Meteoroids and Meteorites
Meteors
• Commonly known as shooting stars
• Caused by a small object entering the Earth’s atmosphere where it is heated by friction until it becomes incandescent, leaving a trail of glowing particles behind it.
• Usually you can see one or two meteors an hour.
• Few times a year a lot more of them can be seen in that space of time, sometimes hundreds of them. Called a meteor shower.
• The trails all seem to come from the same point in the sky, called the radiant.
• A meteor shower is named after the constellation in which the radiant is seen.
• What causes a meteor shower? When a comet is heated by the Sun, it leaves behind a trail of gas and dust. If the comet’s path intersects the Earth’s orbit, the Earth will pass through the trail of dust every year, and the dust particles will enter the Earth’s atmosphere and produce a meteor shower.
• How can you find out in advance when one will occur? Many sources that will tell you when to look for one. In those sources you will see the terms Right Ascension (RA) and Declination (Dec).
Meteoroids and Meteorites
• The objects that cause meteors are called meteoroids. Most of them are about the size of a grain of sand and vaporize entirely in the atmosphere, but occasionally one comes along that is large enough to survive and hit the ground, and then it’s called a meteorite.
• A meteoroid remains chemically pristine in space; if it lands and becomes a meteorite, only the surface gets contaminated with earthly material, while the rest of it is made up of the same stuff as the early solar system.
• Its interior can be analysed to discover what the solar system used to be made of.
• A meteorite is identified as having come from another planet or some other body, most often Mars or the Moon.
• These objects can give valuable information about the chemical composition of the bodies.
• If the impact of a meteorite is energetic enough, it will leave a crater - a hole in the ground that’s much bigger than the object that created it. Planets and satellites without a thick atmosphere or active geological processes remain covered with craters from such impacts. Small craters on Earth are soon eroded away by wind and rain, or shifting plate tectonics, but the largest of them remain visible for quite some time, leaving evidence that a big impact occurred sometime in the past.
• Magical properties of Meteorites? They certainly do, since they are made of the same magical stuff that formed the early solar system.
• This magic is wild and unpredictable, and it interferes with any magic we do.
• Wilbur van Snobbe. He found a half-buried meteorite and tried to cast the Summoning Charm to unearth it so that he could sell it to a museum. The spell missed its target and hit a nearby rock, which flew up and hit him on the head instead of landing at his feet, the destination on which he had concentrated. He rushed to the spot where he had found the meteorite, with the intention of trying once again to unearth it with his wand. His wizardly pride was rudely shattered when he saw a Muggle in the process of unearthing it with the appropriate tool for the job: a shovel.
Asteroids
• An asteroid is like a meteoroid, only bigger – that is, more than 100 meters across. The largest known asteroid, Ceres, is almost 1000 kilometres in diameter.
• Asteroids differ from comets in that they never acquire an atmosphere, because they don’t have any ices to evaporate if they pass close to the Sun.
• They are divided into three groups depending upon what they’re primarily made of: carbon-rich, stony, and metallic.
• Asteroids come in many shapes and sizes, but the largest ones are round because their gravity moulds them into spheres.
• Asteroids come in many shapes and sizes, but the largest ones are round because their gravity moulds them into spheres.
• Ida, the first asteroid to be discovered with a moon. As you can see, it is far from being round.
• Most asteroids are located in the asteroid belt, which is between the orbits of Mars and Jupiter.
• Some are closer to the Sun, and of those, a few come close enough to Earth to be called near-Earth asteroids. Astronomers keep a close watch on near-Earth asteroids because there is always the chance that one of them could hit Earth or explode nearby, with results ranging from mildly dangerous to catastrophic.
Dwarf Planets
• A dwarf planet isn’t just a smaller version of a planet: the term doesn’t refer to size but to criteria decided upon by the International Astronomical Union in 2006.
• Pluto, discovered in 1930, was long considered to be the solar system’s ninth planet. But in 2005, a body was discovered that is about the same size as Pluto; it was named Eris. In 2006, the International Astronomical Union (IAU), concerned that future discovery of many such objects would lead to a proliferation of planets, decided a modification of what we call a planet was needed. This change would narrow the definition to exclude numerous bodies like Pluto and Eris. Thus, they invented the term dwarf planet to describe such objects.
• According to the new definition, a planet has to satisfy three conditions: 1) It orbits the Sun or another star, rather than another body. 2)It has enough self-gravity for its shape to be nearly spherical. 3) It has cleared its orbit of space debris.
• An object that satisfies the first two conditions but not the third one is now deemed a dwarf planet. Five bodies are currently classified as such and were so classified in the following order: Pluto, Eris, Ceres (also the largest known asteroid), Haumea (which is elongated because it rotates so fast), and Makemake.
• Pluto has five moons. Charon, Styx, Nix, Kerberos, and Hydra
• Ceres has no moons.
• Haumea has two moons, Namaka and Hi’iaka
• Eris has one moon, Dysnomia.
• Makemake has one moon, not yet named. Nicknamed MK 2
• All dwarf planets, except for Ceres orbits are in the Kuiper belt. A region of space outside of Neptune’s orbit, although Pluto occasionally comes closer to the Sun than Neptune’s path.
• The Kuiper belt contains a lot of bodies, some of which are almost as big as Pluto, and the more space debris there is near the orbit of an object, the harder it is for that object to clear it. If Pluto had been located in an emptier part of the solar system, it might still be called a planet. Pluto got demoted not because of its own properties, but because it was unlucky enough to be in a part of the solar system with a lot of debris around it, which, in some people’s opinion, is not a valid criterion for demoting it. Other people argue that limiting the growth of the number of planets is indeed a valid reason for demoting Pluto.
• Like the planets and the Moon, the dwarf planets do reflect magic to Earth. Pluto’s magic, which is just barely detectable. The other dwarf planets are either too small or too far away for their magic to have any noticeable effect here.
