Telescopes and models of the Universe

In a nutshell

As technology developed, astronomers have gone from observing the Universe using the naked eye to using space telescopes. Space telescopes allow more information to be collected and produce more detailed images.

Pre-modern observations of the Universe

Ancient astronomers looked at the star with the naked eye and split them into constellations. They observed and recorded patterns of when the different constellations appeared in the night sky.

They also built monuments and devices to show the position of the stars or the Sun throughout a day or a year. This enabled them to keep track of the seasons.

Example

A sundial is a device that tells the time of day. It works as the Sun shines on the device and the shadow created points towards the time. The earliest versions of sundials date back to around $1500$ BCE (BC) from ancient Egyptian and Babylonian astronomy.

Modern telescopes

The astronomical telescope was invented in the early $17th$ century by Galileo Galilei. This invention allowed people to observe closer features of the moon and the planets and develop the heliocentric model of the solar system.

Physics; Space physics; KS4 Year 10; Telescopes and models of the Universe

Modern telescopes have improved upon this invention and astronomers can now get access to more information. They have a range in sizes, from small telescopes that students can use to larger telescopes found in observatories.

These telescopes can detect other electromagnetic (EM) frequencies that the human eye cannot see. They also have a greater magnification and the data recorded can be processed by computers.

Models of the Solar System

The Greek astronomer Ptomely created the geocentric model of the Solar System. This model put Earth at the centre of the Solar System with each planet and the Sun orbiting around the Earth.

However Nicolaus Copernicus, a Polish astronomer, thought that the Solar System followed the heliocentric model. This put the Sun at the centre of the Solar System with each planet orbiting around it.

The invention of the telescope allowed astronomers to make more observations about the Solar System. Galileo discovered some of Jupiter's moons which showed that not everything orbited the Earth. This, and other evidence, was used to support the heliocentric model of the Solar System.

Geocentric model

Physics; Space physics; KS4 Year 10; Telescopes and models of the Universe

1.	The Earth
2.	The Moon
3.	Mercury
4.	Venus
5.	The Sun
6.	Mars
7.	Jupiter
8.	Saturn
9.	Fixed stars

Heliocentric model

1.	The Sun
2.	Mercury
3.	Venus
4.	Earth (and the Moon)
5.	Mars
6.	Jupiter
7.	Saturn

Physics; Space physics; KS4 Year 10; Telescopes and models of the Universe

Space telescopes

The atmosphere is a limiting factor in how well astronomers can observe the Universe from Earth. This is because the atmosphere absorbs wavelengths of EM radiation which stops them from being detected.

Physics; Space physics; KS4 Year 10; Telescopes and models of the Universe

A.	The Earth's atmosphere
B.	Increasing wavelength
1.	Gamma rays
2.	X-rays
3.	Ultraviolet radiation
4.	Visible light
5.	Infrared radiation
6.	Microwaves
7.	Radio waves
8.	Optical telescope
9.	Radio telescope

Example

Visible light and radio waves are observed by telescopes on Earth. However, most ultraviolet light does not penetrate the atmosphere so cannot be detected.

Space telescopes overcome this as they are positioned in space where the atmosphere does not affect the signals they receive. This means more information can be detected and the images produced are clearer and much more detailed.

However, as they are positioned in space they are much harder to repair and are more expensive to produce.

Example

The James Webb Space Telescope (JWST) was launched on $25th$  December $2021$ . The first image was released in July $2022$ and captured much more information than the Hubble did in $2017$ ! This shows that the technology astronomers have access to is constantly improving.