💡 Light Pollution & the Night Sky
⭐ About Stars
A star is a giant glowing ball of hot gas in space that can be seen in the night sky, though only a small percentage are visible to the naked eye.
What Makes Stars Shine and Twinkle?
Stars are born in patches of gas and dust floating in space, known as stellar nurseries. Gravity pulls the gas and dust closer together, forming clumps until they are large enough and collapse, releasing energy. As the temperature and pressure rise in these clumps, hydrogen atoms are squished together and form a new element, helium, through a process called nuclear fusion. It is this process that causes the star to shine.
Why Do Planets Shine?
After stars are formed, leftover gas and dust swirl around the new star in a spinning disk, called a protoplanetary disk. As this material spins around, it bumps together and clumps up, similar to snowballs. These clumps keep growing, eventually forming a planet. Despite forming similar to stars, planets do not form large enough clumps to drive nuclear fusion. As a result, planets do not produce their own light, and instead reflect light from the Sun.
Planet or Star?
Looking at the night sky, you might notice some "stars" twinkle while others don't. Starlight enters our atmosphere, and the light waves bend as they pass through pockets of air at different temperatures. This bending of light is called refraction, and since the light is coming from a single point, stars appear to twinkle. Planets are much closer and instead appear as tiny discs in the sky — the light we get from planets is much larger, cancelling out the refraction.
Living Like Our Ancestors
With just the naked eye, ancient civilisations were able to observe and record the night sky, noting the positions of stars, eclipses, and moon phases. Through this, they created star maps — the first recorded one made in 1000 BCE by the Assyro-Babylonians in Mesopotamia, in what is now present-day southern Iraq. Ancient Greeks noticed that whilst most stars moved east to west in fixed positions, some wandered — naming them "planetes" (wanderers), which we now know as planets.
💡 Save Our Stars — Light Pollution
What Is Light Pollution?
Light pollution is the excessive use of artificial light, which projects up into the night sky and creates a sky glow, turning night into day. Mostly found over urban areas, nighttime use of cars, streetlamps, and other poorly designed lights brighten up the sky, affecting humans, plants, and animals. Light pollution drowns out light from celestial bodies such as galaxies, planets, and stars.
Why Is It a Problem?
Light pollution affects humans, plants, and animals by confusing our natural circadian rhythm. In humans, artificial light decreases melatonin production — the hormone that helps us sleep. Plants and animals also use natural light signals from the sun, moon, and stars to time their behaviours. Nocturnal animals with migration patterns are guided by moonlight and get lost and confused. Light pollution also prevents nocturnal animals from feeding in lit areas, as they risk being eaten by predators.
The Bortle Scale
Created by John E. Bortle in 2001, most astronomers use the Bortle Scale to classify the level of light pollution in an area. It is a 9-level numeric scale: class 1 is an excellent dark sky with no light interference, and class 9 refers to inner-city sky viewing where light significantly reduces the number of objects visible.
What Can Be Done?
- Only turn lights on when necessary and for a specific purpose.
- Use adaptive light controls to manage timing, intensity, and colour.
- Keep low-intensity lighting close to the ground.
- Only use warm-coloured bulbs — blue LED light reduces melatonin in both humans and wildlife.
- Add caps to streetlamps to redirect light downward, keeping it out of the night sky.
Interactive Map
Want to find out how light-polluted your area is? Check out this interactive light pollution map!
