The Hubble Telescope: Its Life, Death, and Discoveries

‍Yes, seriously. 

Hubble has allowed us to witness the birth of new stars, see alien planets outside our solar system, and get a closer look at supermassive black holes. These sights captured our imaginations and — more importantly — deepened our understanding of how life and everything that we know came to be. 

Unfortunately, Hubble obviously won’t last forever. But although its days are numbered, it’s not quite done making history just yet.

Fun facts: An overview of Hubble

Hubble has peered far, far back into the universe, so it’s easy to forget that it isn’t actually that far away. Hubble is in low-Earth orbit, just 320 miles (515 km) above our planet’s surface. It’s far enough away that it has a crystal-clear view, free from the haze of our atmosphere. But it’s close enough that astronauts can reach the telescope to repair and upgrade its various components. 

Hubble is roughly the size of a school bus and weighs about the same as two full-grown elephants. Now, Imagine that very heavy school bus racing around at about 17,500 miles per hour (27,300 km/h). That’s how fast Hubble travels. 

And it also has impressive eyes. It can lock on a target that’s about equal to the width of a human hair as seen from a mile away. In its more than 30-year tenure, it has locked on more than a target or two. To date, Hubble has sent back more than 290 terabytes of data. 

To collect all that data, Hubble is decked out with some remarkably advanced technologies. It was the first space telescope with the ability to capture wavelengths of light spanning from near-infrared to ultraviolet. As a friendly reminder, the various frequencies of light are (from low to high) radio waves, microwaves, infrared, visible light, ultraviolet, X-rays, and gamma rays. 

While in orbit, its primary mirror collects light from cosmic objects from both our own solar system and the distant universe — it can look back as far as 13.4 billion years. And Hubble’s resolution is superior to the human eye by a factor of around 1,000. What does that mean, exactly? Well, it’s basically equivalent to resolving two fireflies less than 10 feet (3 m) apart in Tokyo all the way from Washington, D.C. 

And in 2021, Hubble got a new assistant, sort of. 

Its successor, the James Webb Space Telescope, is flashier, bigger, and more powerful. While Hubble’s mirror is just 7.9 feet (2.4 m) in diameter, Webb’s honeycomb-shaped mirrors combine for a total diameter of 21 feet four inches (6.5 m), meaning it has more than six times the light-collecting area. NASA says the Webb telescope will complement and extend Hubble’s work with longer wavelength coverage, a larger field of view, and improved sensitivity. 

That’s got some people wondering… is this the beginning of the end for Hubble? If it is, did Hubble accomplish everything it set out to do?

Hubble’s major discoveries 

Hubble’s original mission was to spend at least 15 years looking out at the farthest and dimmest regions of the cosmos. To say that Hubble has exceeded expectations would be a vast understatement. The time it’s been in service is one thing — 30 years and counting — but the window Hubble has opened into the cosmos is another matter entirely. 

As already noted, the telescope’s more than 1.6 million observations have contributed to 21,000 peer-reviewed scientific publications. These papers have been referenced in other publications more than 900,000 times, and they continue to be referenced an average of 150 times a day. 

One of Hubble's most important contributions to science was identifying the age of our universe. 

Before Hubble launched, calculations of the universe’s age were imprecise, ranging from 10 billion to 20 billion years. Hubble helped scientists clock the age of the universe at 13.8 billion years by comparing the brightness of a Cepheid star in our galaxy to a similar one in a faraway galaxy. 

Hubble's observations also helped show that the universe is not only expanding, its expansion is actually accelerating. The discovery won Adam Riess, an astronomer at the Space Telescope Science Institute (STScI) and Krieger-Eisenhower Professor in Physics and Astronomy at The Johns Hopkins University in Baltimore, the 2011 Nobel Prize in Physics. It provided the first concrete evidence that the objects in our universe will continue to get farther and farther apart until, eventually, the cosmos goes entirely dark and dies an icy death. 

Hubble also provided hard evidence that most galaxies have enormous black holes at their center. The larger the galaxy, the larger the black hole. This suggested that, as black holes grew with their galaxies, they devoured a portion of their galaxies’ mass. Hubble helped confirm that the largest supermassive black hole in our vicinity is that of Messier 87, which harbors a black hole 6.5 billion times more massive than our Sun. 

On a lighter note (pun intended), Hubble also saw the birth of stars. Its infrared detectors pierced the massive, turbulent clouds of gas and dust — also known as nebula — that give life to thousands of stars. The process is violent but bewitchingly beautiful. 

Closer to home, Hubble studied the outer planets in our solar system and their moons. In fact, it took the first images of bright auroras at Saturn and Jupiter’s poles. These observations yielded essential clues in the search for life beyond Earth. For instance, on Jupiter’s moon, Ganymede, Hubble’s detection of its auroras provided the best evidence yet for an underground saltwater ocean — an ocean with more water than all of Earth’s oceans. 

And examining Hubble’s observations led scientists to make another, perhaps more significant, finding: water vapor in Ganymede’s atmosphere. This provided further evidence that the planet could be habitable — not for humans, obviously, but possibly for alien microbes.

Hubble’s seemingly endless cycle of repairs 

Over the course o more than 30 years of observations, Hubble has been the butt of a joke or two… mostly because of equipment issues tracing back to its first days in service. 

When Hubble began to return scientific data to Earth, astronomers saw stars surrounded by fuzzy halos of light instead of point-like images of stars. It turns out the edges of the primary mirror were ground too flat. The error was ultimately just the width of a human hair, but that tiny difference was enough to cause major problems. Hubble’s images were blurry. 

NASA engineers built the Wide Field Camera 3 — which would become the most technologically advanced instrument on board — to correct the flaw in the primary mirror. Basically, Hubble has to wear “glasses,” but it has been worth it. The images sent back in December 1993 taken with the new setup were breathtaking. 

And that is far from the only upgrade. In fact, engineers designed Hubble to have many replaceable parts that astronauts could switch out. This design allowed the telescope to be upgraded with new, cutting-edge instruments during the various servicing missions from 1993 to 2009. 

However, no more servicing missions are scheduled to repair or replace the equipment. In many ways, Hubble is now on its own.  

Still, engineers are working on ways to keep the Hubble operating as long as possible. They’ve even figured out a way for the telescope to continue observing the universe with… wait for it… just one gyroscope. Hubble’s six gyroscopes help it turn and lock onto new targets. When one failed in 2018, the telescope entered “safe mode” for about three weeks. Engineers realized they could compensate with other sensors on the spacecraft if any fail in the future.

But don’t get your hopes up too much. In 2021, Hubble went offline twice due to issues with its hardware and instruments, further proving that Hubble has aged significantly. If Hubble’s past is any indication, its crafty engineers will find solutions to the multitude of problems that could go wrong for some time to come, but there’s only so much even they can do.

What’s next for Hubble? 

Hubble will continue to blaze a trail for at least a few more years. The subsystems and instruments “have a reliability exceeding 80 percent through 2025,” Hubble mission head Thomas Brown has said.

But given its current status, at any point in time, there’s a very real chance that issues with Hubble will reach the point of no return. To that end, nobody knows for sure exactly how long Hubble will be able to keep studying the cosmos. 

Scientists do know that Hubble’s orbit is stable until the 2030s. Its orbit was once as high as 360 miles (579 km), but it has slowly descended over time due to atmospheric drag. 

To keep Hubble from falling toward Earth, the telescope would need to be boosted to a higher orbit. Alternatively, the telescope could be steered to crash into Earth’s atmosphere when the orbit decays. It would be a controlled reentry, so there wouldn’t be any risk to human life. But Hubble would perish in a ball of fire, burning upon reentry. 

With the James Webb Space Telescope now making its own observations, some may wonder whether it may finally be time for Hubble to retire. After all, Hubble more or less enjoyed its over 30 years in the Sun. Isn’t it time for the young (and incredibly powerful) new space telescope to have its turn in the limelight? In truth, the two telescopes work in tandem to make and verify discoveries, assisting one another in their work. 

So, although its days are definitely numbered, Hubble’s still contributing to science and isn't down for the count just yet.