Kelly McSweeney

Aug 7th 2020

Could JWST Discover the Largest Object in the Universe?


Soon, the James Webb Space Telescope (also known as JWST or Webb) will expand our views of the sky. Astronomers will use the new telescope to observe previously unseen regions of space, ranging from the galaxies that formed right after the Big Bang to the youngest star systems that are forming today.

Earth is minuscule in the scale of the universe. So far, astronomers have discovered giant planets, supermassive black holes, hypergiant stars, superclusters of galaxies and other large objects in between. And that’s while observing just a small sliver of the universe with the Hubble Space Telescope. It is hard to predict what Webb will ultimately discover.

“It’s a new instrument, the largest telescope ever built for space,” says Jon Arenberg, chief engineer for Space Science Missions at Northrop Grumman. “We’ll be able to collect data that we have not gotten our hands on before, including observing the early universe, in particular.”

Astronomers have already discovered some humongous objects, and JWST could soon uncover even more giants in space.

“By having this new instrument that that can observe even more galaxies than we’ve seen before, we will be able to look for structures and groups of these galaxies in places we’ve never looked,” Arenberg explains.

Contemplating the size of objects in space compared to our tiny home on Earth could make your head spin, but Arenberg finds comfort and pride in JWST’s mission of discovery.

“I feel empowered, enlightened, illuminated — not tiny,” Arenberg says. He adds, “The scale of the universe is huge. But so is our planet compared to me, and I don’t feel small or insignificant here on Earth.”

What Is the Largest Object in the Universe?

It’s a straightforward question with a nebulous answer. First, it depends on how you define size — by mass or volume. A giant cloud of gas, for example, is enormous in volume but relatively small in mass (it doesn’t contain much matter). Black holes, on the other hand, are defined by infinitely small volume with infinite density, according to Sky and Telescope.

Secondly, we’ll have to consider what counts as an object. If a group of particles is an object, what about a group of galaxies?

One thing is certain, the largest objects in space are much, much larger than Earth. They just appear small because they are so far away from us. Here are some of the largest known objects in the universe.

1. Largest Planet

Jupiter is the largest planet in our solar system. It’s a giant ball of gas that could fit all the other planets in the solar system inside it. According to NASA, more than 1,300 Earths would fit inside Jupiter.

But Jupiter is tiny compared to HAT-P-67 b, an exoplanet (orbiting a different star than our sun) that astronomers first observed in 2017. reported that this newly discovered planet is 2.08 times the size of Jupiter, although it isn’t as dense, weighing in at 60% less than Jupiter’s mass. It’s the biggest, fluffiest planet we know of so far.

2. Largest Star

According to NASA, our sun is a million times the size of the Earth. But to put this in context, if our entire solar system was the size of a quarter, the sun would be a microscopic speck of dust on that quarter.

As big as a million times Earth sounds, points out that our sun is only an average-sized star. Scientists have discovered “hypergiant” stars such as UY Scuti, which could fit more than 1,700 of our suns in its radius.

3. Largest Black Hole

Unlike stars, black holes don’t take up space, but they are dense. The largest black hole in our neighborhood, Sagittarius A*, is 4 million times more massive than the sun, according to MIT Technology Review. Meanwhile, 700 million light-years away from Earth, a galaxy called Holm 15A contains the largest known black hole in the observable universe. Astronomers used data gathered by the Very Large Telescope in Chile’s Atacama Desert to run simulations that map out this distant galaxy. Their models suggest that Holm 15A has a supermassive black hole that is at least 40 billion times more massive than the sun.

4. Largest Structure

Although structures might not technically count as “objects” according to astrophysics terminology, from a logical perspective, a structure is the largest object in the universe.

Gravity can make galaxies clump together in space. Multiple galaxies form clusters, which can form superclusters, and even long lines of galaxies called walls, according to New Scientist. The largest known structure is the Baryon Oscillation Spectroscopic Survey Great Wall. This superstructure is made of 830 galaxies bound by gravity that swirl together in a wall that is a billion light-years across.

JWST could help astronomers discover even larger superstructures.

“We will be able to collect images and spectra from hundreds or tens of thousands of galaxies. This will help astronomers identify groups of galaxies,” says Arenberg.

Frontier of the Future

Great societies have always pursued the unknown, explains Arenberg. He says, “Increasing our scientific knowledge is not only good in and of itself, but it’s the basis of our economy and our security.”

All these records for the largest objects in space could soon be broken as new, powerful telescopes reveal hidden spots in the universe.

Peering into deep space with JWST is the next step in a long legacy of exploration.

Arenberg says, “Americans have always prided themselves on discovery and the frontier since the beginning of the country. And this is just carrying on that legacy from our ancestors. We should dare to do these amazing things and inspire ourselves and inspire the next generation.”