Kelly McSweeney

Feb 25th 2022

Uncovering a Lost Galaxy in the Virgo Cluster


A lost galaxy has been uncovered in a new image from NASA’s Hubble Space Telescope. In truth, the galaxy was never really lost — but it was buried in stardust.

“Astronomy is and always will be a technology-limited science,” says Jonathan Arenberg, Chief Engineer for Space Science Missions at Northrop Grumman.

Arenberg explains that the new image was created using a combination of several sensors — notably, infrared sensors that can see through the dust that likely clouded earlier views of the galaxy.

German-British astronomer William Herschel observed the galaxy, dubbed NGC 4535, in 1785, according to The galaxy is located in the Virgo Cluster, and when it’s viewed through a small ground-based telescope, it looks fuzzy because the light is dispersed through the dust. In the 1950s, amateur astronomer and poet Leland S. Copeland observed the galaxy and named it “the lost galaxy,” likely due to its hazy appearance.

Getting to Know NGC 4535

The lost galaxy is one of the largest galaxies in the Virgo Cluster, which is located 50 million light-years from Earth. This distance across space-time means that, by the time we are able to observe it, we aren’t seeing a current image. Rather, we’re observing the galaxy’s light as it was 50 million years ago. In the context of the history of the universe, this was just a few years after the dinosaurs died, Arenberg explains.

“If somebody on that cluster could have seen Earth, they wouldn’t have seen humans,” he says. “That gives you an idea of how big and far apart things are.”

Atlas of the Universe points out that the Virgo Cluster has roughly 2,000 galaxies (many of which are dwarf galaxies) in a diameter of approximately 15 million light-years. In comparison, our Milky Way galaxy is in the Local Group, which contains 50 times the number of galaxies in a similar diameter.

NGC 4535 is a barred spiral galaxy; it has a spiral structure that is similar to the Milky Way’s but with a distinct bar throughout the center and arms stretching from the bar.

Older Telescopes vs. Hubble

Previous observations of the lost galaxy likely struggled to capture a clear picture because of several limitations with older telescopes, Arenberg says. First, ground-based telescopes have to look through Earth’s atmosphere. Some larger ground-based observatories have additional sensors to make up for the atmospheric challenges, but Herschel and Copeland likely could only see visible light. Plus, Hubble is much bigger than the telescopes they would have used and can capture more light. Mostly, the difference is the technology. We can think of old telescopes as being like older cameras that use film.

“They would have a thin film of photosensitive material such as silver salt, and when the light hit it, it would change the chemistry to create a negative,” Arenberg says.

Hubble, on the other hand, has a suite of charge-coupled devices (CCDs), which are like the array of sensors in a digital camera or smartphone.

“As light falls on the sensor, it takes that light and turns it into a series of numbers that is a representation of an image,” says Arenberg.

The lost galaxy has a lot of dust, which is hard to see through because dust scatters light. The longer the wavelength, the less light scatters, so if the earlier astronomers were using a naked eye or film, the dust would have scattered the light from the galaxy, making it appear fuzzy or “lost.”

Hubble mostly observes visible light, but it also has some capability in the infrared portion of the electromagnetic spectrum. This allows astronomers to lay data from different wavelengths on top of each other to create a picture of the barred spiral galaxy.

“Infrared essentially peels away the dust,” he says. “And the Webb Telescope will do that in spades because it is designed to primarily work in the infrared range.”

A Note About Color

The breathtaking image of NGC 4535 was created with scientific data and a bit of artistic license. Hubble doesn’t actually take color photos, as NASA points out. Instead, it uses several different filters to observe objects in space and represents the intensity of light in different numbers. Humans can only see colors in visible light, which is a relatively tiny portion of the spectrum.

Our eyes can’t see light in X-rays or infrared, so astronomers choose colors that we can see to represent the images in ways that our eyes and brains can process and appreciate. For example, in the image of the lost galaxy, the yellower stars represent the older, cooler stars that are clustered at the center of the galaxy, as Live Science reports. Meanwhile, the bright blue stars represent the younger, hotter stars in the galaxy’s arms.

Future Observations and the Importance of Dust

When Webb launches later in 2021, it will be approximately 100 times more powerful than Hubble, with an emphasis on using infrared sensors to observe early galaxies.

“If Webb were to look at the same galaxy, we would have a crisper view of the stars and the arms of the galaxy,” Arenberg says. “The dust halo that we see now would be diminished.”

While Webb is Hubble’s successor, it isn’t meant to be its replacement. Instead, both telescopes could be used in tandem, with Hubble focusing on the visible light and Webb focusing on infrared.

“They are fundamentally different kinds of instruments, but operating together, they provide much more powerful insight than either one of them operating alone,” Arenberg explains.

Dust can get in the way and cloud our views of planets and stars in galaxies such as NGC 4535. But understanding the physics and science of space dust is crucial to our understanding of the universe, so we don’t want to ignore it. The elements that make up our very existence come from dust moving in space, pushing around heavier elements.

“The planet that we live on and the atoms that make up our bodies are manufactured as a result of the evolving universe, and they got to this planet — they got to our ancestors and into us because of dust transport,” Arenberg explains.

In order to make the best observations of objects in the universe, we need to use several different tools to view space. Ideally, we would look at the lost galaxy with every band of the electromagnetic spectrum — from high-energy, short-wavelength gamma rays to low-energy long-wavelength radio waves and everything in between.

In order to observe and understand the universe and how it evolves, we need observations from every part of the spectrum. The recently released image of NGC 4535 emphasizes this point, demonstrating why we need so many different tools — Hubble, Webb and ground telescopes alike — to collect data from the universe at different wavelengths and energies.

“There is not one perfect wavelength that will unlock the secrets of the universe,” says Arenberg.

Hubble’s Eventual Descent

More than three decades after it launched, the Hubble space telescope continues to provide valuable data for scientists to study and stunning images that inspire amateurs and experts alike. Eventually, NASA will need to retire Hubble and safely remove it from orbit. Arenberg explains that Hubble is located in a low Earth orbit, not entirely out of our atmosphere.

“It bumps into the occasional molecule and suffers drag,” he says.

Plus, it is large enough that it probably wouldn’t burn up in the atmosphere the way smaller objects do, and we wouldn’t want it to fall without control. Someday, scientists will guide it to safely return home. Until then, we can look forward to continued observations, soon with the added boost of Webb’s infrared eyes toward even more distant galaxies.

Interested in all things in outer space and exploration? We are, too. Take a look at open positions at Northrop Grumman and consider joining our team.