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Lord_Chris

Astronomy Thread

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We have a history thread, so why not an astronomy thread too? ;)

 

I've got to say, this thread was kind of inspired by Crusader's history thread, I'll keep this thread updated with all the things to look out for in the night sky, and I'll try to add some articles every now and then about what is what, how you can tell and what the features of the different things are .etc.

 

But before we get started, I'd recommend downloading the program Stellarium. This can be configured to show the stars where you live, and is available on Windows, Linux, MacOS as well as Ubuntu for free. It's also available on Android and iOS for a small price.

 

stellarium-001.png

 

I'd like to start with the full moon (or this time, Super Moon - I'll let you know more about that at some other point ;) ) which will be available in four days time (August 29th). The moon will be on the opposite side of the earth to the sun, and this will occur approximately 18:35 UTC. That's one hour later here in the UK due to DST. The moon will be on one of its closest approaches to earth, and will probably look brighter and larger compared to usual.


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The fields have eyes, and the woods have ears.

⁠— Geoffrey Chaucer, The Canterbury Tales: The Knight's Tale

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Thanks both of you! I'm going to start today at some point with articles.

 

Stellarium is really good for showing you what stars are in what place - and it's not even limited to Earth either. I've viewed from Mars, and Mars' moon Phobos before.

 

You can have custom landscapes, plugins, star regions .etc.


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The fields have eyes, and the woods have ears.

⁠— Geoffrey Chaucer, The Canterbury Tales: The Knight's Tale

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[colour=#6EA4BF]The Universe, Galaxies and Nebulae[/colour]

 

20_080815galaxiavialactea.jpg

 

What exactly is The Universe?

 

There are lots of similar, confusing terms in space, and this is certainly no exception. The Universe is everything in existence.

 

What is a Galaxy?

 

A galaxy is a system of millions, or billions, of stars, together with gas or dust, which is held together by gravitational pull. A galaxy contains hundreds of solar systems, similar, or not similar to our own. Each solar system contains a central sun, like ours (or mostly bigger) and several planets of several shapes and sizes. Each star inside a galaxy is a sun, and each sun belongs to a unique solar system (in 99% of cases). Our galaxy is called The Milky Way, below is a map of our Galaxy along with the position of our sun.

 

The Milky Wayhttp://qph.is.quoracdn.net/main-qimg-0ecf217e39e271c7a6e09a1015e01149?convert_to_webp=true[/img]

 

What is a Nebula?

 

A Nebula (or Nebulae plural) is a cloud of gas and dust in the outer solar system. Many people mix up the difference between Galaxies and Nebulae due to this difference. They are in some ways, similar, but are completely separate things. A Nebula is a region where stars are formed. Every star is born in a Nebula - and they can also contain remains of dead, or dying stars.

 

Rosette Nebulahttp://static.giaoducthoidai.vn/uploaded/tranghn/2015_02_22/329801423735560_woyc.jpg?width=500[/img]

 

How many galaxies are there?

 

There are hundreds of billions of galaxies, and in each one is hundreds of billions of stars. That's one to two hundred billion solar systems at least in The Milky Way, including our own. Our sun is just one of the hundreds of billions of stars in The Milky Way alone.


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The fields have eyes, and the woods have ears.

⁠— Geoffrey Chaucer, The Canterbury Tales: The Knight's Tale

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[colour=#6EA4BF]Days, Months Years and Seasons[/colour]

 

These all happen at different times, and for different lengths on each planet. Ancient Civilisations took note of days months and years by two possibilities: One, the Sun, or two, the Moon. This allowed people to know when to plant crops and search for seasonal foods. Several civilisations including the Mayans and Babylonians developed complex ways to tell seasonal changes.

 

 

earth-seasons.png?1

 

Days

 

We all know what a day is, and every planet has them. But do you actually know what causes them?

 

A day is the amount of time for a planet to spin 365 degrees on its orbit. Because of this fact, there is always one side of a planet facing the sun, while the other half is in darkness - and this is exactly why the night is dark; there is no light making it from the Sun, which makes the opposite side of the planet dark. Most people think that a day is 24 hours, but in fact, it's very slightly less. A day is actually 23 hours, 56 minutes and 4 seconds. The extra four minutes gets added up, and every four years, this is responsible for what becomes a leap year - an extra day gets added into February to make the calendars correct.

 

Interesting fact: The calendar was created by the Romans in 45 BC.

 

space_p12.jpg

 

Months

 

A month is the amount of time for a moon to orbit the earth. The luna orbit means that one side of the moon is deadlocked towards the Earth, and the "dark side" of the moon will never be shown on the earth due to how the moon rotates. The moon rotates in this manner due to Earth's own gravity. The moon also goes through various stages, such as Waxing Gibbous, Waning Gibbous, Full Moon and New Moon.

 

FG08_11.jpg

 

Years

 

This is the amount of time that a planet takes to orbit the sun. A planet is rotating constantly on its axis (as shown above) but it's also moving around the sun at the same time. This is what is responsible for years. Every 365 and a quarter days (due to a day not being exactly 24 hours) a new year begins.

 

Seasons

 

Seasons are the one thing that people can find confusing. Seasons depend on the tilt of the Earth's axis. You now know that the Earth moves on its axis, and moves around the Sun. The seasons Spring, Summer, Autumn and Winter are all caused by the tilt of the Earth's axis. This is also why the opposite side of the Earth has the opposite season. For example, in Australia, it can snow during the Summer, because Australia is on the opposite side of the Earth to the UK. So when we get warn weather, it's Australia's winter even though the season is called Summer still. I'd also like to point out that the tilt of the Earth is in fact caused by the Moon.

 

Due to seasons, Constellations in the night sky can appear at different points in the night sky throughout the year.

 

earth-sun-seasons-jpg.jpg


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The fields have eyes, and the woods have ears.

⁠— Geoffrey Chaucer, The Canterbury Tales: The Knight's Tale

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Interesting fact: The calendar was created by the Romans in 45 BC.

Another interesting tidbit (perhaps more historical) is that the calendar Chris is reference was called the Julian Calendar which was altered in 1582 and called the Gregorian Calendar in honor of the pope at that time (Gregory XIII) who supposedly created the reform himself.

 

Many Eastern Orthodox countries (obviously not Roman Catholic) did not adopt the reforms. However, the very slight difference added up over time, and the eastern nations used the Julian Calendar up through the 19th century (and AFAIK into the early 20th). Now here's a fun fact: when Napoleon I started his Austerlitz campaign, the Austrian emperor was allied to the Tsar of Russia and arranged for a certain time for the bulk of the Russian army to aid the Austrians. However, the Russians were weeks behind schedule because their high command didn't take into account the calendar difference. xD


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[colour=#6EA4BF]The formation of the Earth, and life[/colour]

 

brodo%20primordiale.jpg

 

We see Earth as a pretty important planet, but as a matter of fact our solar system is just a home for our sun with a few bits and pieces left over. The formation of earth began as all of the other planets did; forming from rocks which were left over after the sun was created 4.5 billion years ago. These were then held together through gravity, and over time began to orbit the sun.

 

The Earth was almost entirely molten, and it was collisions with other asteroids, meteors and space objects that made the planet bigger. One very large collision was thought to make the earth start spinning on its axis, responsible for day and night. Another was thought to have made the moon (more below) and it was over time that the planet cooled, the Volcanoes stopped erupting, and eventually liquid water was formed.

 

But just how did water end up on Earth after it was molten for so long?

 

No one really knows. One of the most common theories is that comets, which are made up of frozen Ice, smashed into the Earth. However, there are a few weaknesses with this theory. One being, that comets are only really found in the outer solar system, so for the most part, they would be too far away to impact the Earth.

 

Another significant weakness is that the water here in earth contains a mixture of H2O (Hydrogen water) and HDO (Heavy density water). In 1986, a space probe had a close encounter with the comet Halley (Halley's comet) and discovered that the composition was in similar quantities to that on Earth. However, most of the other comets which have so far been analysed have twice as much HDO as on Earth. But comets are so far away from the sun, that we do not know if in fact this was representative of all comets.

 

One other theory about how water formed was due to the Steam the volcanoes were giving out. But because this is part of the water cycle, and some kind of water source must exist, there is a flaw in this theory too.

 

The origin of life

 

The earliest life forms were only in the oceans on the planet, and were very basic bacteria, and some of these are called "extremophiles". These have the ability to survive in the most extreme conditions, such as at the bottom of the Antarctic now, which receives 0.1% of sunlight - or possibly 3.8 billion years ago. Some believe these also exist of Jupiter's moon "Europa".

 

But there are also questions as to how exactly this formed in the first place. We believe it was from a comet with water, but there is no firm evidence. Eventually, over a long time, animals became increasingly complex, and divided into two groups; one that used the air, and the other which chose the stay hidden and use the water, and we evolved to better use the planet.

 

human_evolution.jpg


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[colour=#6EA4BF]The formation of The Moon[/colour]

 

moon-formation-theories-debated_69202_600x450.jpg

 

It's been a beacon for travellers, a guide for keeping time, and in some cultures, it's even been a god. It's the only celestial body ever visited by man, and NASA is talking of a permanent outpost there. But just how did the moon form?

 

The formation of The Moon

 

There have been four theories on how the moon formed. All but one, have significant weaknesses.

 

The Capture theory

 

This states the Earth simply captured The Moon through it's own gravity. This theory would show why the moon and the earth have different iron compositions, if they formed in two different places in the solar system, however, it does not explain why the moon is moving away from us each year - or how the Earth's gravity managed to capture something that big in the first place, since the moon is roughly a quarter the size of the earth. And if the earth did capture the moon, it would be moving closer to it, not further away.

 

goim014.jpg

 

The Accretion theory

 

This theory states the earth and the moon were formed as a double system. But there are a lot of problems with this theory, such as the angular momentum of both planets.

 

Fission Theory

 

This theory was proposed by George Darwin, the son of Charles Darwin and in part received some attention because of his father. However, he very soon moved out of his father's shadow. George Darwin discovered through mathematical calculations that the moon is moving gradually further away from the earth each year, and managed to work it backwards, to get to the stage where the moon was moving around the earth 5-6 times a day, however, unfortunately he couldn't get any further, the maths just wouldn't let him do it.

 

It wasn't actually proved the moon is moving further away fro the earth until Astronauts landed on the moon and set up mirrors on the surface of the moon, approximately 86 years later. You can shine a light on the moon, this will bounce back, and you can monitor the distance. The distance the moon is moving away from the earth is 3.8 centimetres per year.

 

The fission theory states that the earth just ejected part of it's mass which then started orbiting around the earth, becoming the moon.

 

Moongiantimpactweb.jpg

 

The giant impact theory

 

This theory is the most up-to-date and accurate theory as to how the moon formed. According to tests done, another planet about the size of the current planet Mars could have formed near the Earth at the start of the solar system. This theory stipulates that the planet came too close to Earth, and smashed into it. The debris then was thought to coalesce into the moon without a year. The planet in this theory which crashed into Earth has been called "Theia".

 

It accounts for the small metallic core of the Moon, as well as the fact that the moon has a much lower iron content than the Earth, which was proven when Astronauts brought back moon rocks after the Apollo missions. There are a few small discrepancies still to be corrected, but by large, it works. The Earth was probably molten at this time anyway, but we believe that this is what started the Earth spinning, which is what gave us day and night.

 

moon-formation.jpg?w=360


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⁠— Geoffrey Chaucer, The Canterbury Tales: The Knight's Tale

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Thanks Crusader! I try to add pictures that immediately hook people, looks like I'm on the right track! :D


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The fields have eyes, and the woods have ears.

⁠— Geoffrey Chaucer, The Canterbury Tales: The Knight's Tale

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[colour=#6EA4BF]Venus - our sister planet[/colour]

 

Venus-Radiant.jpg

 

Venus is described as Earth's sister planet, because for a long time people thought they were similar, and are similar in size. It wasn't until 1962 that people found out the truth ....

 

When the Romans looked up at Venus, they named the planet after their goddess of Love. But if they knew what we know now, they would probably have called it after the god of underworld. With toxic air, intense heat, volcanic eruptions and atmospheric pressure 93 times heavier than Earth's, this planet is certainly not the planet of beauty.

 

Venus

 

Venus has been hit by some massive asteroids and meteors in the past. Scientists believe that it's been hit by one so big, it has actually reversed the rotation of the planet. Venus is the only planet which rotates in a retrograde rotation (backwards), and it also has a very slow rotation - in fact, a Venusian day, which lasts 243 Earth days, is longer than a Venusian year, which lasts for 225 days on Earth. So not only does the sun rise in the west and set in the east, but a day lasts considerably longer than a year!

 

Even though Venus is the second planet to the Sun, it is considerably hotter, at an average temperature of 900 degrees Fahrenheit (approx. 482 degrees Celsius). This is due to the greenhouse effect, the very process which keeps life alive on Earth (without which, the Earth would be roughly 40 degrees cooler). Some scientists have called this the "runaway" greenhouse effect, and stipulate that this could be what Earth becomes, if global warming is not taken care of, as we are already heading in that direction. Venus really could become hell on earth, literally.

 

greenhouse-effect-2.jpg

 

On Venus, 96% of the atmosphere is carbon dioxide, which traps the heat inside, keeping the planet roasting. The planet also has a lot of sulphur dioxide in the atmosphere from the constantly erupting volcanoes. Sulphur dioxide alone can cause circulatory collapse and severe breathing difficulties. But in addition, lightening is constantly going off, which is not only more powerful, but also never reaches the ground, due to the atmospheric pressure. Instead, it simply jumps from cloud to cloud.

 

Interesting fact: On Venus, it snows metal, and rains sulphuric acid.

 

18vh0bzyhhafhpng.png

 

There are no plants to convert the Carbon dioxide to oxygen, and even if plants existed, they would probably last a few seconds at the most, due to the pressure of the atmosphere, and also the heat. Similarly if a person could survive the heat, they would also probably be crushed by the pressure. Potentially anyway, a human would last maybe 1 second before being burned up. Venus is littered with hundreds of monstrous volcanoes, such as Maat Mons (see below), which is 35,000 feet high (much higher than Mount Everest). The constant eruptions only worsen the state of the atmosphere. Scientists speculate there could be any amount of volcanoes between a thousand to a million.

 

Another major difference between Venus to other planets is that it is not covered in a lot of craters; instead, most of the surface is littered with cooled, and cooling, lava flows.

 

maat_mons.gif


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The fields have eyes, and the woods have ears.

⁠— Geoffrey Chaucer, The Canterbury Tales: The Knight's Tale

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