Why stars differ in brightness, space telescopes and a human sundial
Week 29 · Theme 4 Change and Stability, Unit 4 Patterns in the Sky: Concept 4.3 Sun and Star Brightness (B), Unit Project Human Sundial · 3 lessons
2
Space telescopes, old and new
Discovery Education Science P5: Term 2, Unit 4, pp. 176–179
GoalSay what astrophysicists do, and compare the Hubble and James Webb space telescopes.
New words
astrophysicist · a scientist who uses ideas about force, energy and motion to understand stars and the universegalaxy · a huge group of stars, gas and dust held together by gravityinfrared light · light we cannot see but can feel as heat
Explanation
Astrophysicists are scientists who study how stars and galaxies work. They use ideas of force, energy and motion, computer models and mathematics. They also study the pictures sent by space telescopes. The Hubble Space Telescope was launched in 1990 and orbits Earth. Its sharp pictures helped us learn how old the universe is and how stars are born and die. The James Webb Space Telescope was launched in 2021. It looks mostly at infrared light, which lets it see through dust clouds and look at very faint, faraway objects. It is far beyond the Moon, about four times as far as the Moon is from Earth, and its big mirror was folded up for the launch and opened in space like a paper unfolding. The two telescopes do not replace each other: they see the sky in different ways and work as a team.
Hubble
James Webb
Launched
1990
2021
Where
orbits Earth
far beyond the Moon
Mainly sees
visible and ultraviolet light
infrared light
Worked examples
Years in space in 2026: Hubble 2026 − 1990 = 36 years; Webb 2026 − 2021 = 5 years. Hubble is 36 − 5 = 31 years older in space.
a star such as the Sun→many stars with gas and dust→a galaxy
A galaxy such as our Milky Way holds an enormous number of stars, all held together by gravity. Our Sun is one star in the Milky Way. Galaxies are far too big and complex to draw honestly, so we describe them in words.
Task
Tool
look at pictures
space telescope data
test ideas
computer models
measure
mathematics
An astrophysicist’s day: Dr Mariam studies a new picture from a space telescope, builds a computer model of a star and writes a report. She asks questions, collects evidence, and uses math. She never looks straight at the Sun.
Class activity
Telescope fact cards. Make two cards, one for Hubble and one for Webb. On each write when it was launched, where it is, and what kind of light it mostly studies. Add one question you would ask an astrophysicist. Then draw a timeline from 1990 to 2026 with both launches marked, and work out the years each has been in space.
Practice
1
What do astrophysicists study, and which three ideas do they use?
They study stars and galaxies, using ideas of force, energy and motion.
2
Which telescope orbits Earth, and which is far beyond the Moon?
Hubble orbits Earth; the Webb is far beyond the Moon.
3
Hubble was launched in 1990. How many years later was Webb launched in 2021?
2021 − 1990 = 31 years later.
4
Why does the Webb telescope look at infrared light?
Infrared light passes through dust clouds and shows very faint, faraway objects.
