If you’ve ever looked up at the night sky and wondered about the stars, you’ve probably heard of the Hubble Space Telescope. What is the Hubble Telescope? It’s one of humanity’s most important tools for understanding the universe.
Launched in 1990, Hubble is a giant observatory that orbits high above Earth. It takes incredibly clear pictures of planets, stars, and galaxies. Because it’s in space, it doesn’t have to look through Earth’s blurry atmosphere, which gives it a crystal-clear view.
This article will tell you everything about this amazing machine. We’ll cover how it works, its rocky start, its greatest discoveries, and how it changed astronomy forever.
What Is The Hubble Telescope
The Hubble Space Telescope is a Cassegrain reflector telescope. It has a 2.4-meter (7.9-foot) primary mirror that collects light from distant objects. That light is then analyzed by its suite of scientific instruments.
Hubble orbits Earth at an altitude of about 547 kilometers (340 miles). It travels at a speed of roughly 27,000 kilometers per hour (17,000 mph), completing an orbit every 95 minutes. It’s about the size of a large school bus and weighs as much as two adult elephants.
Unlike telescopes on the ground, Hubble sees in not just visible light (the light our eyes see), but also ultraviolet and near-infrared light. This allows it to observe phenomena that are invisible to us, like the birth of stars inside dense clouds of dust.
The Instruments On Board
Hubble doesn’t use just one camera. It has several key instruments that work together:
- Wide Field Camera 3 (WFC3): The main camera for visible and infrared light. It took many of Hubble’s most famous colorful images.
- Advanced Camera for Surveys (ACS): Designed for wide-field imaging in visible light, it’s great for surveying large areas of sky.
- Cosmic Origins Spectrograph (COS): Splits light into its component colors (a spectrum) to study the composition and temperature of objects.
- Space Telescope Imaging Spectrograph (STIS): Another spectrograph, useful for studying black holes and galaxy cores.
A Rocky Start and a Famous Fix
Hubble’s story didn’t begin smoothly. Just weeks after launch, scientists realized there was a serious problem. The primary mirror had been ground perfectly, but to the wrong shape—a flaw called spherical aberration. It was only 1/50th the thickness of a human hair off, but that was enough to make the images blurry.
This was a huge embarrasment for NASA and a setback for science. However, engineers quickly designed a solution. In 1993, astronauts on the Space Shuttle Endeavour conducted a daring servicing mission. They installed a set of corrective optics, basically glasses for Hubble, called COSTAR (Corrective Optics Space Telescope Axial Replacement). The fix was a complete success, and Hubble began returning the stunning, sharp images we know today.
The Importance of Servicing Missions
Hubble was designed to be serviced by astronauts. Over its life, five Space Shuttle missions visited the telescope to repair, upgrade, and replace parts. These missions:
- Fixed the flawed mirror (1993).
- Updated old instruments with newer, more powerful ones.
- Replaced failing gyroscopes and batteries.
- Extended Hubble’s operational life for decades.
The last servicing mission was in 2009. Without these incredible engineering feats, Hubble would have stopped working years ago.
Hubble’s Greatest Hits: Discoveries That Changed Science
Hubble’s contributions to astronomy are almost to many to count. It has helped pin down the age of the universe, found evidence for supermassive black holes, and watched weather on other planets.
Pinpointing the Age of the Universe
Before Hubble, estimates for the age of the universe ranged from 10 to 20 billion years. Hubble’s precise observations of pulsating stars called Cepheid variables allowed scientists to measure the expansion rate of the universe (the Hubble Constant) with unprecedented accuracy. This led to the currently accepted age of about 13.8 billion years.
The Deep Field Images
Some of Hubble’s most profound work came from pointing at what looked like empty space. In 1995, astronomers aimed Hubble at a tiny, dark patch of sky for 10 days straight. The result was the Hubble Deep Field, revealing thousands of galaxies in a area the size of a grain of sand held at arm’s length.
This proved the universe is filled with an unimaginable number of galaxies. Later, the Ultra Deep Field and eXtreme Deep Field looked even longer and farther, seeing galaxies as they were just a few hundred million years after the Big Bang.
Atmospheric Studies of Exoplanets
Hubble wasn’t built to find planets around other stars (exoplanets), but it became a master at studying them. It was the first telescope to directly detect the atmosphere of an exoplanet. By watching a planet pass in front of its star, Hubble’s spectrographs can analyze the starlight filtering through the planet’s air, identifying chemicals like sodium, water vapor, and even helium.
Tracking the Expansion of the Universe
Observations of distant supernovae by Hubble helped reveal that the expansion of the universe is not slowing down, as once thought, but accelerating. This led to the Nobel Prize-winning discovery of dark energy, a mysterious force that makes up about 68% of the cosmos and pushes galaxies apart.
How Hubble’s Images Are Made
You might wonder why Hubble’s pictures are so colorful and beautiful. The process is both scientific and artistic.
- Grayscale Data: Hubble’s cameras take black-and-white images. They use filters that only let in specific wavelengths of light, often corresponding to the glow of specific elements (like red for sulfur, green for hydrogen, blue for oxygen).
- Color Assignment: Astronomers assign a color to each filter’s image. They often use a “natural” palette (red for red light, etc.) or a “representative” palette to highlight features.
- Combination: The colored images are layered on top of each other in software to create the final full-color composite. The colors help scientists see structure and composition that would be invisible otherwise.
So, while the colors are “real” in that they represent real data, they are not exactly what the human eye would see, especially in infrared or ultraviolet light.
Hubble’s Legacy and Future
After over 30 years in operation, Hubble is still going strong. It continues to make vital observations, often working in tandem with newer telescopes like the James Webb Space Telescope (JWST). Webb sees primarily in infrared, complementing Hubble’s visible and ultraviolet vision.
Hubble’s ultimate fate is tied to its orbit. Very slowly, atmospheric drag is causing it to descend. Without a boost, it will re-enter Earth’s atmosphere sometime in the 2030s. NASA is currently studying options for a safe deorbit, possibly using a robotic spacecraft.
But it’s legacy is secure. It has made over 1.5 million observations and fueled more than 19,000 scientific papers. It brought the cosmos into our homes and inspired generations to look up and ask questions. It showed us our place in a vast and beautiful universe.
Frequently Asked Questions (FAQ)
How far can the Hubble telescope see?
Hubble can see galaxies over 13.4 billion light-years away. This means it’s looking at light that left those galaxies when the universe was very young. Its deepest views, like the eXtreme Deep Field, capture galaxies from about 500 million years after the Big Bang.
Where is the Hubble telescope right now?
You can actually track Hubble in real-time! NASA has a website called “Where is Hubble?” that shows its position above Earth. It orbits our planet roughly every 95 minutes, so its location changes constantly as it circles the globe.
Can I see the Hubble telescope from Earth?
Yes, you can! Hubble is often visible from the ground as a bright, fast-moving star. It doesn’t have flashing lights. Websites and apps like Heavens-Above can tell you when it will pass over your location. You’ll need a clear, dark sky to spot it.
Why is Hubble better than telescopes on Earth?
Hubble’s main advantage is it’s location above Earth’s atmosphere. The atmosphere distorts light (which is why stars twinkle) and blocks certain wavelengths like ultraviolet light. Being in space gives Hubble a steady, clear view 24/7, without clouds or daylight interrupting.
Who was the Hubble telescope named after?
It was named after astronomer Edwin P. Hubble. In the 1920s, he made the groundbreaking discovery that the universe is expanding. This was the foundation for the Big Bang theory. The telescope named in his honor continues to study that expansion.
How much did the Hubble telescope cost?
The initial development and launch cost about $1.5 billion (in 1990 dollars). When you factor in the servicing missions and over 30 years of operations, the total cost is estimated to be over $10 billion. Most scientists agree it has been worth every penny for the knowledge it has provided.
How are pictures from Hubble telescope taken?
Hubble doesn’t use film or a typical digital camera. Its instruments use detectors called CCDs to capture light as digital data. This data is beamed to Earth via satellites, where scientists process and combine the information from different filters to create the final images we see.
What will replace the Hubble telescope?
The James Webb Space Telescope (launched in 2021) is considered Hubble’s scientific successor, though it sees in different light. However, Hubble has not been replaced directly. NASA’s upcoming Nancy Grace Roman Space Telescope, set to launch in 2027, will have a field of view 100 times wider than Hubble’s, surveying the sky much faster.