Unit 3: Chapter 3: Solar System 1 Introduction

One Astronomical Unit (AU) is equal to the average value of the Earth-Sun distance

AU: used to signify distances of various objects from the sun or from each other within the solar system. (93 million miles or 150 million Km)

Improvements in making lenses and mirrors helped increase the power of telescopes and opened up a universe that no one could ever have imagined! William Herschel built the biggest telescope of his time. In 1781, while looking at stars not visible to the naked eye, he accidently discovered a new planet. It was named after the Greek god, Uranus.

As people were able to make more polished lenses, the more powerful they became William Herschel, built one of the biggest telescopes at that time, he found the new planet and named it Uranus after the Greek God. He discovered it accidently while looking for stars

Here is another view that shows the order of planets. Note the distances are not to scale!

Distances aren't drawn to scale

Galileo's most amazing discovery was that the 5 wandering stars were not stars at all. They were spheres like earth and moon that shine in the sky by reflecting sunlight.

Earth and the five wanderers are now called planets. They revolve around the sun at different distances. This was the beginning of discovering the family of objects we now call The Solar System Most revolutionary discovery that Galileo made with the telescope. He concluded that the spheres were planets, not stars. This was the beginning of the search of the complete description of our universe

We now know that the solar system is made up of many more objects than the 7 wanderers plus our earth

Every time we find an object that shifts in position with respect to the fixed stars, it is likely to be a new solar system object! This was discovered in 2018, probably a comet discovered. It moves so irs closer and cant be a star so its part of our solar system

True or False: It would take about a 100 earths to fill up a hollowed out sun.

False

True or False: Our solar system and our galaxy would occupy about the same amount of space in the universe

False

The first telescope could only magnify by a factor of three! Galileo's improvements increased the magnification to 23 which enabled him to see mountains on the moon, spots on the sun, moons around Jupiter and individual stars in the Milky way!

Galileo made lots of improvements on the telescope

The 4 outer planets are giants compared to the size of the 4 inner planets! Jupiter/Saturn are quite a lot bigger than Uranus/Neptune.

Huge size difference from the 4 inner ones. Saturn and Jupiter are a lot bigger than Uranus and neptune

A small wobble in the orbits of Uranus and Neptune led to the prediction of another object lying beyond their orbits. On February 18, 1930, Clyde William Tombaugh discovered Pluto. After a long stint of being regarded as the ninth planet of the solar system Pluto was demoted in 2006 to a new category of objects called dwarf planets.

Next major discovery came out by using mathematics. They predicted there had to be another planet or object out further than the sun that was causing them to wobble. Pluto (the smallest planet). In 2006, they decided that it was demoted into dwarf planet category. A lot of people don't think Pluto should have been demoted. So, there are still only 8 planets in the solar system because pluto is a dwarf planet.

Below is the same picture with planets and dwarf planets labeled and orbital paths drawn in. You can see why this realistic picture is rarely published!!

Orbits of dwarf planets are more flattened or eliprical orbits like pluto. Orbits in middle are those of the 8 planets.

The discovery of the telescope in 1608 by a Dutch eyeglass maker named Hans Lippershey revolutionized the science of Astronomy. The telescope magnifies objects and allows one to see details not visible to the naked eye.

Reason Galileo was able to defend the objections was with the help of the telescope Invention of telescope was a huge push/part of the furthering of astronomy. Magnifies objects as you see them.

Other stars are not part of our Solar System! But they each have their own systems of varying numbers of planets ... we call them star systems!

Stars aren't part of our solar systems (they have their own solar system (star System)). Every star has its own planets around them. Even the biggest telescopes can't show these.

Now compare planet sizes to the size of Sun! Sun's diameter is 109 times the diameter of Earth and 1.3 million Earths can fit inside it!

Sun is huge even compared to Saturn and Jupiter

Another fact about the Solar System that is not depicted very well in popular images is the relative size of different planetary orbits!

The 4 inner planets are crowded together while the 4 outer planets are spaced out over long distances High variation in distance and height way from sun. Compared to size of solar system, earth would seem crowded. Diameter of the solar system is a 100 times the Earth-Sun distance

In the zoomed-in version below you can see Earth's tiny moon beside it and on the right are four largest dwarf planets including Pluto

The 4 little dots on right are the largest dwarf planets in the solar system (pluto is one of the biggest)

The 9000 or so stars we can see with our eyes are a tiny fraction of the 400 billion stars in our galaxy, each one with its own family of planets and moons

The stars we can see with our naked eye are 9,000. That is a tiny fraction of the number of stars within our galaxy (milky way galaxy). Our sun is one of its spiraled arm (we can only see the stars within that circle).

Brightness of an object in the sky depends on two things, its inherent brightness, called its luminosity, and also how far it is from us. Objects can be invisible to the naked eye either because they are not inherently very bright or they are too far away from us. Stars that are much, much further away can be visible while planets that are closer to us may be invisible

There are 2 things that matter, how bright and how large it looks to us...the inherent brightness (light emitting from it) and the distance of it from us. If star is further away, same luminosity but brightness changes

The solar system is mostly empty space!

There is even more empty space around it ... in our model the next closest star would be in SF or LA

And finally the relative sizes of the planets are hardy ever depicted in proper proportion. Below are the relative sizes of the inner 4 planets

These are depicted in a misleading way in life. Earth, Venus, mercury, and mars. Earth and Venus are a lot bigger and mars is bigger than mercury

Typical images of the Solar System create a very misleading impression of its scale and also of the relative size of different planets!

This picture doesn't really give you a good idea of how our solar system really is

Our galaxy is one of more than 100 billion similar galaxies in the observable universe!! In this photo shot by Hubble Space Telescope, each blob is a galaxy made of billions of stars

This was taken by a telescope. Shows all galaxys. There are at least 100 billion galaxies.

True or False: The distance between Neptune and the Sun is about 30 times the distance between Earth and Sun.

True

Studying the details of Uranus' orbit revealed that it was being pulled outwards by some other object. Newton's laws were then used to predict the object's location in the sky!

Using these amazing calculations done by Le Verrier yet another planet was discovered in 1846. This bluish planet was named Neptune after the Roman god of sea. The solar system had now grown in size to 8 planets. Used more for mathematics. They found the laws of gravitation didn't really match Newtons, is because there was probably something outside pulling on Uranus' planet. They found out it was another planet moving it, and it was Neptune named after the Roman god of Sea.

Imagine yourself watching from the window of a spaceship approaching the Solar System from the top of its orbital plane. The diameter of the Solar System is about 10 billion miles. What will you see when you are about that distance from the sun? Assuming you are approaching it from the top

You will see the sun as a fairly bright star and Saturn and Jupiter as dim stars lost in the background. All other planets will be invisible Wont see very much. You will see a bright star (sun). The only other thing youd see if you knew what they were, tiny dim stars (Saturn and Jupiter). Turns out all other planets including earth wouldn't be visible with your naked eye (unless you use a telescope). Magazines don't use this image because its not as intriguing.

Which two properties determine how bright an object will appear to our naked eye when looking at it in the night sky?

luminosity and distance from earth

Which category of objects or objects listed below is NOT considered part of our modern day view of the solar system

stars