ASTRONOMY

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• Well, now that we have thoroughly covered the earth and its origins, let’s discover a bit about space.

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• Since it is the most prominent feature of our solar system, let’s begin our discussion with the sun.

• The sun is massive and actually makes up 99.8% of our solar system’s mass.

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• As a result, the sun exerts enormous amounts of gravity on the objects which surround it.

• This gravity causes a logical elliptical pattern of motion called an orbit.

ASTRONOMY• Now you may have already deduced that the

sun does not have a solid surface.• It is actually a ball of hot gas all the way

through.• About ¼ of the sun is made of Helium.• About ¾ of the sun is made of Hydrogen.

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• However, the sun is sectioned off into layers.• The interior of the sun consists of a core, the

radiation zone, and the convection zone.

ASTRONOMY• The core of the sun is where the energy of the

sun comes from.• It is not burning any type of fuel, but rather

giving off energy through nuclear fusion.• This is when hydrogen ions combine to form

helium and that gives off energy.

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• The total mass of helium is slightly less that hydrogen that makes it…the remaining mass is transformed into energy.

ASTRONOMY• The next layer of the sun is called the

radiation layer.• This is a layer of very tightly packed gasses

under extreme pressure in which energy is transferred in mostly electromagnetic radiation.

• Because the layer is so tightly packed, energy can take over 100,000 years to pass through it.

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• Finally, the outermost layer is called the convection zone.

• As gasses reach the surface, they cool and sink once more to the core where the cycle begins again.

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• Perhaps you’ve never thought this about the sun, but it actually has an atmosphere.

• Its parts are the photosphere, chromosphere and corona.

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• The photosphere as the name implies is the innermost sphere that gives off visible light.

• Again, the sun doesn’t have a solid surface, but the gasses given off by the sun are dense enough to be visible.

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• The chromosphere is the middle layer which gives off color.

• Again, this is a word that can be broken into its Greek roots.

ASTRONOMY• Finally, the corona (which means “crown” in

Latin) is the outermost layer of the thinnest gasses.

• This stretches into space for millions of kilometers.

• This creates thin streams of particles called the solar wind.

• We’ll come back to those later.

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• Over the decades as we have studied the sun, various features have exhibited themselves again and again.

• Among them are sunspots, prominences and solar flares.

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• Sunspots can look small to even the heavily telescoped eye, but in truth many are larger than the earth!

• These are spots of gasses on the sun’s surface, which are cooler than those around them, thus they appear darker.

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• The fact that these spots appeared to be moving stumped some scientists.

• At last however, they realized that it is because the sun rotates on an axis just like the earth does!

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• Another feature is called a prominence.• This is when several groups of sunspots are

linked by reddish loops of gasses.

ASTRONOMY• A solar flare is when those groups of sunspots

SUDDENLY connect.• This releases a mass of magnetic energy which

abruptly heats the gasses on the surface of the sun to millions of degrees Celsius.

• This basically causes an eruption.• That eruption is a solar flare.

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• Solar winds are basically electromagnetic particles from the sun that reach the earth.

• Usually, the radiation is blocked by our atmosphere.

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• But at the poles, the radiation can enter the atmosphere causing certain molecules to glow.

• These glowing ribbons created by solar winds are called auroras.

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• However, there is a risk when this enters our atmosphere of a magnetic storm.

• These can interrupt radio, TV and phone signals and even cause mass power outages.

MAGNETIC STORM

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• As we work our way our into the solar system, we will most certainly stumble upon planets.

• Since they are vastly different from the others, we’ll discuss the inner planets first.

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• The four inner planets are small, dense and have rocky surfaces.

• Because you could walk on their surfaces, they are called terrestrial planets.

• The Latin word “terra” means Earth.

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• Earth is very unique in many ways you already know about.

• It consists of three layers; the core, mantle and crust.

• It has an atmosphere which extends about 100km above the surface.

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• But most importantly, Earth is the only planet able to support liquid water.

• This is what makes life here possible for us.

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• Let’s discuss a planet slightly more foreign.• Mercury is the innermost planet to the sun.• It is also the smallest terrestrial planet.

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• Mercury was studied by a probe called Mariner 10 in 1974 and 1975.

• They found a crater laden, rocky surface which has not changed much over billions of years.

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• Mercury has little to no atmosphere.• Due to this fact, temperatures fluctuate wildly

on its surface ranging from 430⁰C in the day and -170⁰C at night.

• That’s 806⁰F to -338⁰F!

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• Venus is farther away from the sun, but it is far from cool.

• In fact, on average, it is the hottest planet of them all!

• Sometimes, Venus is called “Earth’s Twin” because of its similar internal structure.

• However, Venus and Earth are VERY different.

ASTRONOMY• Venus is odd in that it takes about 7.5 months

to rotate around the sun, but 8 months to revolve around its axis.

• Thus, Venus’s day is longer than its year!• Also, it’s rotation on its axis is opposite ours.• Scientists believe Venus got smacked into

reversal by some large object.

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• Unlike Mercury, Venus has an extremely thick atmosphere.

• It always appears cloudy there because of this and the greenhouse effect occurs due to heat being trapped.

• This is why it is so hot…on average hotter than Mercury.

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• It was discovered by the probe Magellan that Venus’s surface is covered by volcanoes and broad planes which were created by lava flow.

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• After we bypass Earth, we reach Mars, the red planet.

• It is red because of the iron rich rocks constantly oxidizing…otherwise known as rusting.

ASTRONOMY• Mars has an atmosphere of over 95% Carbon

Dioxide.• It is much thinner than Venus’s atmosphere.• Mars is slightly smaller than Earth, but you

could walk on its surface with proper equipment.

ASTRONOMY• The surface of Mars holds the most mystery

and promise.• Scientists can see on the surface what appear

to be canyons and features resembling coastlines.

• This implies that perhaps Mars was once home to liquid water!

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• However, that would have been at a time when its atmosphere was thicker and climate warmer.

• Liquid water could not exist on Mars now.• There is frozen water on Mars which resides in

ice caps closely resembling ours!• Some may also be frozen underground.

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• Since Mars is tilted on its axis like us, it undergoes season changes like we do.

• In Martian winter the ice caps grow and in Martian spring they shrink.

ASTRONOMY• Over the decades, many probes have explored

Mars.• They found strong evidence that liquid water

was once present and also that volcanoes were and are present.

• The Martian Olympus Mons is the largest volcano in our solar system!

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• The Outer Planets are much stranger than the terrestrial worlds.

• These consist of four gas giants and the tiny Pluto.

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• Jupiter as well as the other gas giants are composed mainly of Hydrogen and Helium and have no solid surface.

• However, they are MUCH larger than Earth and the other terrestrial planets.

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• Despite their name gas giants have a core of mostly liquid Hydrogen and Helium.

• This is due to the enormous pressure at the core of these planets.

• Because of said pressure, the temperature is also much greater at their cores.

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• Which of the gas giants has rings?• Actually, they all do!• A ring is simply a think disk of small particles

of ice and rock.• Some are so thin, we can barely see them.

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• Jupiter is the largest planet and the one with the most mass.

• In fact, Jupiter’s mass is about 2.5 times that of all the other planets put together!

ASTRONOMY• One of Jupiter’s most prominent features it its

Great Red Spot.• The Hydrogen/Helium atmosphere contains a

constant storm that, when viewed from space, appears as the spot.

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• With no land mass to weaken the storm, it rages on.

• It was first sighted in the 1600s and likely existed long before that.

• By the way…The Great Red Spot is larger than Earth!

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• Jupiter likely has a (relatively) small dense core of rock and iron surrounded by a liquid mantle of hydrogen and helium.

• Scientists believe this is true of all the gas giants.

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• The pressure at Jupiter’s core is believed to be about 30 million times greater than Earth’s surface.

ASTRONOMY• Being so large, Jupiter has many moons.• Galileo discovered four of them which he

named Io, Europa, Ganymede and Callisto.• We now have found 49 official (named)

moons of Jupiter and another 14 which are still under consideration.

ASTRONOMY• Europa is one of the most promising objects in

our solar system in terms of supporting life like ours.

• There is strong evidence to suggest that there is liquid water on Europa now!

• Constantly, oxygen is building up there and in only a few million years, there could be enough to support complex life.

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• Saturn is the next planet out.• It too has raging storms on its surface, though

not as destructive as on Jupiter.• It’s average density is less than water.

ASTRONOMY• The rings around Saturn are largely what it is

known for however.• Saturn has many rings broken up by dark

bands of nothing, then more rings.• By simple chance, Saturn has the most

spectacular rings of any planet.

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• Saturn has many moons the largest of which is called simply Titan.

• Today, Saturn has 52 official moons.

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• Uranus is next and it’s diameter is four times that of the earth and it is still dwarfed in comparison to the other gas giants.

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• Two things make Uranus stand out.• The first is that it, like Saturn, has prominent

rings, though they are thinner and darker.

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• Secondly, it’s axis of rotation skewers the planet horizontally, causing Uranus to rotate on its side.

• This too is believed to have been caused by a wayward flying object in space.

• Uranus is believed to have at least 27 moons.

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• Neptune is very similar to Uranus in size and color.

• It is a cold, blue planet hence it being named after the God of the Sea, Neptune.

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• When scientists noticed that Uranus was not quite following the path predicted by gravitational charts, they knew there must be something else at play.

• Thus, Neptune was predicted and later discovered.

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• Like Jupiter, Neptune has a Great Spot, only its great spot is dark.

• However, it is also likely a giant storm.

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• Neptune has many moons, like the other gas giants.

• The largest of these is called Triton and it has a very thin atmosphere.

• There are about 13 moons of Neptune.

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• Pluto is the last in the line of our solar system.• However, PLUTO IS NO LONGER A PLANET!!!• On August 24th, 2006 Astronomers ruled that

Pluto was actually a dwarf, and simply not large enough to be called a planet.

ASTRONOMY• This was partially thanks to several other

dwarfs discovered by Astronomer Mike Brown some of which are larger than Pluto.

• There are over 40 dwarfs discovered to date.• One of those larger than Pluto is UB313…

nicknamed Xena.

I DID IT!!! I KILLED PLUTO!!!

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• Pluto is terrestrial in composition and has one “moon” (if it can be called that) named Charon.

• Pluto revolves around the sun once every 248 Earth years.

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• Beyond our planets lie the stars.• Groups of stars in set patterns are called

constellations.• We still use some constellations to locate

things in the night sky.

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• Stars are hot spheres of gas like our sun.• Their energy is created by nuclear fusion and

that causes them to glow just like our sun.• We classify stars by their color, temperature,

size, composition and brightness.

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• The color difference of some stars can be seen with the naked eye.

• One star called Betelgeuse (part of Orion) looks reddish whereas Rigel looks bluish-white.

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• Stars with a temperature of about 3200 degrees Celsius (cool by start standards), burn reddish.

• Stars with a temperature of about 5500 degrees Celsius (like our sun), burn yellow.

• Stars with a temperature of 20000 degrees Celsius or over, burn white or bluish.

ASTRONOMY• There are many size classifications for stars also.• Our sun is a medium sized star.• A few very large stars are called giants or

supergiants.• Most stars are smaller than our sun and are

called white dwarf stars.• Some even smaller stars, called neutron stars,

are only about 20km in diameter.

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• What actually makes up stars is called the composition.

• A device called a spectrograph can deduce what makes up a star by what color light it gives off.

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• Finally, the brightness of a star can vary greatly.

• Generally speaking, the hotter the star, the brighter it glows.

• The larger, the brighter also!

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• As you may know, there is a difference in how bright a star really is an what we can see from Earth.

• Absolute brightness is the brightness a star would have were it “standard distance” from earth.

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• Apparent Brightness is how bright a star appears to be as seen from Earth.

• Many stars have been misjudged and misclassified simply because of their distance from Earth!

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• About a century ago, two scientists names Hertzprung and Russell developed a diagram mapping the temperature and absolute brightness together on an x-y plane.

• The resulting Hertzsprung-Russell Diagram is still used today!

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• All this is fascinating, but how do stars come to be?

• A star begins its “life” as a nebula or a large cloud of gas and dust spread out into a large volume.

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• The densest part of the nebula pulls all dust and gas inward until all the material is compacted into a small volume.

• At this stage we call the star a protostar.• The Greek prefix proto- means “earliest”.

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• When the gasses and dust compact enough, nuclear fusion begins.

• When this happens energy is released as heat and light.

• This is when our star really begins to take shape!

ASTRONOMY• But how long will our star “live”?• That depends on its mass.• Generally, smaller stars have longer lives.• Now, that may seem odd in your brain, but

think of it like this.• The smaller the star, the slower it will burn

and thus, the longer it lives.

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• Stars smaller than our sun can live for up to 200 billion years.

• Our sun will likely live for 10 billion…minus the 4.6 billion its already burned.

ASTRONOMY• When a star begins to “die” is core shrinks

while its outer portion expands.• At this point it becomes either a red giant or a

supergiant.• When the entire process is complete, the star

will become either a white dwarf, neutron star or black hole.

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• White dwarfs happen when the outer gasses of a dying star simply float away leaving only the bluish-white core.

• This cools and becomes a white dwarf.• When these stop glowing and cool completely,

they are called black dwarfs.

ASTRONOMY• Stars with greater mass sometimes suddenly

run out of fuel and can explode.• This is called a supernova.• When the debris from that collects and

condenses, a neutron star can form.• These are lesser in volume, but greater in

mass than our sun.

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• In the late 60’s, British astronomy student, Jocelyn Bell began receiving mysterious radio signals from space at the lab in which she worked.

• Other astronomers confirmed that the radio signals were legitimate, but could not identify the source.

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• The nicknamed the source “LGM”, short for Little Green Men assuming that the signals were from extraterrestrial life forms.

• It turned out to be a neutron star spinning rapidly enough to produce a radio signal.

• A neutron star that does this is called a pulsar.

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• Some dying stars basically collapse inward on themselves creating a black hole.

• This is a mass with a gravitational pull so strong that not even light can escape.

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• Obviously, no one has ever “seen” a black hole, but through magnetic wave testing, x-ray testing and other such experiments, their presence is definite.