Have you ever looked up at the night sky from the city and thought it seemed a bit boring? You might see some well-known constellations like the Big Dipper or Orion’s Belt. But if you focus on a hazy patch of sky and hold out your thumb, how many stars do you think are hiding behind it? Ten? Twenty? Actually, if you used the Hubble Space Telescope to look at that tiny patch, you’d see not just stars but entire galaxies, each with billions of stars, and more than 1,000 of them could be hidden behind your thumb!
The universe is much bigger than what you can see from the city, and even larger than the starry sky you might see in the countryside. Astrophysicists, who study the universe, see it as having more stars than all the grains of sand on Earth. When you look at the stars at night, you’re participating in one of the oldest sciences in human history. People have been studying the sky long before we had navigation, farming, or even language. But unlike other sciences, astronomy is all about observing. We can’t do experiments in a lab with stars. Even though we’ve sent people to the moon and probes to the edge of our solar system, these distances are tiny compared to the vast spaces between stars.
So, how do we learn so much about galaxies, their makeup, and their numbers? It all starts with the stars we see at night. We want to know what they’re made of, how hot they are, how big, how old, and how far away they are. Amazingly, we can find out all this just from the light they give off.
One way we learn about stars is by turning their light into rainbows. When you see a rainbow on Earth, it’s sunlight scattered through water droplets, breaking into different colors. We can do something similar with starlight using special tools that spread out the light. When we look at the sun’s light, we see dark lines in the rainbow. These lines are like fingerprints of atoms. Each atom absorbs light at certain wavelengths, and by seeing how much light is missing, we can figure out which elements are in the sun’s atmosphere and how much of them there are. We use the same method to study other stars: make a rainbow, see what’s missing, and find out which elements are there.
But we don’t just look at the light we can see. Think about radio waves. They bring music to your car and can travel through space almost without stopping. Because they’ve traveled so far, radio waves can tell us about the universe’s early history, just a few thousand years after the Big Bang. We also study infrared light from cooler objects like gas and dust clouds, and ultraviolet light from hot stars that have just formed.
By studying different wavelengths, we get a fuller picture of any object and different views of the universe. That’s why astrophysicists use various telescopes that cover everything from infrared to ultraviolet to X-rays. They use giant radio dishes, large mirrors, and space satellites to catch light that the Earth’s atmosphere would block. Astrophysicists don’t just see the billions of stars in countless galaxies; they also hear, feel, and sense them in many ways, each telling a different story.
In the end, it all starts with light—the kind we can see and the kind we can’t. If you want to discover the universe’s secrets, just follow the light.
Imagine you are an ancient astronomer. Design your own constellation using a set of stars visible in the night sky. Draw it out and write a short story about its origin and significance. Share your constellation with the class and explain why you chose those particular stars.
Using a simple spectroscope, observe different light sources such as a light bulb or the sun (with proper safety measures). Record the spectrum you see and compare it to known spectra of elements. Discuss how this relates to how scientists determine the composition of stars.
Research different types of telescopes and the wavelengths they observe (e.g., radio, infrared, ultraviolet). Create a poster or digital presentation that explains how each type of telescope contributes to our understanding of the universe. Present your findings to the class.
On a clear night, hold your thumb up to the sky and estimate how many stars and galaxies might be hidden behind it. Research how the Hubble Space Telescope has expanded our view of the universe. Write a short essay on how technology has changed our understanding of space.
Listen to recordings of radio waves from space and explore how they are converted into sound. Create a multimedia project that combines images of space with these sounds. Reflect on how different senses can be used to study and appreciate the universe.
The city sky can often seem rather dull. If you look up at the patches of haze between buildings, you might spot familiar constellations like the Big Dipper or Orion’s Belt. But take a closer look at that hazy patch and hold out your thumb. How many stars do you think are hidden behind it? Ten? Twenty? Guess again. If you were to observe that small patch of sky with the Hubble Space Telescope, instead of seeing points of light, you would see smudges. These aren’t just stars; they’re galaxies, similar to our Milky Way. There are billions of stars in these galaxies, and more than 1,000 of them are concealed behind your thumb.
The universe is far larger than what you can see from the city, and even more expansive than the starry sky visible from the countryside. This is how astrophysicists perceive the universe, with more stars than all the grains of sand on Earth. By gazing at the stars at night, you’ve engaged in one of the oldest sciences in human history. The study of the heavens predates navigation, agriculture, and possibly even language itself. However, unlike other sciences, astronomy is purely observational. We cannot manipulate the parameters of our experiments in a laboratory setting. Our most advanced technology can send humans to the moon and probes to the edge of the solar system, but these distances are minuscule compared to the vast spaces between stars.
So how do we know so much about other galaxies, their composition, their numbers, or even their existence? We start with the first thing we see when we look up at night: the stars. We aim to learn about their properties: What are they made of? How hot are they? How massive? How old? How far are they from Earth? Remarkably, we can uncover all of this information simply from the light that shines in the sky.
We can decode one type of stellar message by transforming starlight into rainbows. When you observe a rainbow on Earth, you’re witnessing sunlight being scattered through water droplets in the atmosphere, breaking it into its various wavelengths. By studying the light from other stars, we can create rainbows using specific instruments that disperse light. When we analyze the scattered light from our sun, we notice something intriguing: dark lines in our rainbow. These lines are the unique fingerprints of atoms. Each type of atom in the solar atmosphere absorbs light at specific wavelengths, and the amount of absorption indicates the quantity of these atoms. By observing how much light is missing at these characteristic wavelengths, we can determine not only the elements present in the Sun’s atmosphere but also their concentrations. This same principle can be applied to study other stars: create a spectral rainbow, identify what’s missing, and discover which elements are present.
But our observations aren’t limited to just the wavelengths visible to our eyes. Consider radio waves. While they can bring music to your car, they can also travel almost unimpeded through space. Because they have traveled such vast distances, radio waves can provide insights into the early history of the universe, dating back just a few thousand years after the Big Bang. We can also examine infrared light emitted by cooler objects, like gas and dust clouds in space, as well as ultraviolet light from hot stars that have recently formed from those clouds.
Studying different wavelengths not only offers a more comprehensive view of any single object but also provides various perspectives of the universe. For this reason, astrophysicists utilize several types of telescopes that cover the spectrum from infrared to ultraviolet to X-ray, employing giant radio dishes, large mirrors, and space satellites to detect light that would otherwise be obstructed by the Earth’s atmosphere. Astrophysicists don’t just see the billions of stars among the countless galaxies in the universe; they hear, feel, and sense them through multiple channels, each revealing a different story.
Ultimately, it all begins with light—the kind we can see and the kind we can’t. If you want to uncover the secrets of the universe, just follow the light.
Stars – Massive, luminous spheres of plasma held together by gravity, often visible in the night sky. – The stars in the night sky are actually huge balls of gas burning millions of miles away.
Galaxies – Large systems of stars, dust, and gas bound together by gravity, often containing billions of stars. – The Milky Way is the galaxy that contains our solar system.
Universe – The vast, all-encompassing space that includes all matter, energy, planets, stars, galaxies, and even the empty space between them. – Scientists study the universe to understand how it began and how it continues to evolve.
Light – Electromagnetic radiation that is visible to the human eye and is responsible for the sense of sight. – Light from the sun takes about eight minutes to reach Earth.
Wavelengths – The distance between successive crests of a wave, especially in electromagnetic waves like light. – Different wavelengths of light are perceived as different colors by the human eye.
Astrophysicists – Scientists who study the physical properties and processes of celestial objects and phenomena. – Astrophysicists use complex equations to understand the behavior of stars and galaxies.
Astronomy – The scientific study of celestial objects, space, and the universe as a whole. – Astronomy helps us learn about the origins and future of our universe.
Telescopes – Instruments that collect and magnify light to observe distant objects in space. – Telescopes allow astronomers to see planets and stars that are far away from Earth.
Elements – Substances consisting of atoms with the same number of protons, found naturally in the universe. – Stars create new elements through the process of nuclear fusion.
Rainbow – A spectrum of light appearing in the sky when sunlight is refracted and dispersed by water droplets. – A rainbow forms when sunlight is split into its component colors by raindrops in the atmosphere.
