Skip to main content

Hubble captures a dusty galaxy that holds a luminous secret

The image from the Hubble Space Telescope this week shows the dusty galaxy NGC 7172, located 110 million light-years away in the constellation of Piscis Austrinus (the southern fish). This might look like a typical galaxy from this angle, but in fact, it holds a secret.

“The lane of dust threading its way across NGC 7172 is obscuring the luminous heart of the galaxy, making NGC 7172 appear to be nothing more than a normal spiral galaxy viewed from the side,” Hubble scientists write. However, on closer inspection astronomers found something unexpected: “When astronomers inspected NGC 7172 across the electromagnetic spectrum they quickly discovered that there was more to it than meets the eye: NGC 7172 is a Seyfert galaxy — a type of galaxy with an intensely luminous active galactic nucleus powered by matter accreting onto a supermassive black hole.”

Tendrils of dark dust threading across the heart of the spiral galaxy NGC 7172.
This image from the NASA/ESA Hubble Space Telescope reveals tendrils of dark dust threading across the heart of the spiral galaxy NGC 7172. The galaxy lies approximately 110 million light-years from Earth in the constellation Piscis Austrinus. ESA/Hubble & NASA, D. J. Rosario, A. Barth; Acknowledgment: L. Shatz

Hubble views objects like this galaxy in the visible light wavelength, which is the same as what the human eye can see. This image was taken using two of its instruments, the Advanced Camera for Surveys and Wide Field Camera 3.

To understand more about the structure of this galaxy, though, it was necessary to look through a different wavelength. In the 1980s astronomers observed the galaxy in the infrared wavelength, which can look through clouds of dust to observe structures beneath. Observations at these wavelengths revealed the brightly glowing heart of the Seyfert galaxy.

The Hubble image uses data collected for a study of active galactic nuclei, a group that includes Seyfert galaxies. Active galactic nuclei are brightly-glowing regions at the heart of galaxies that seem to be brighter than can be accounted for due to the density of stars there. These regions can be so bright that they are brighter than the entire rest of the galaxy.

Editors' Recommendations

Georgina Torbet
Georgina is the Digital Trends space writer, covering human space exploration, planetary science, and cosmology. She…
One galaxy, two views: see a comparison of images from Hubble and Webb
The peculiar galaxy NGC 3256 takes centre stage in this image from the NASA/ESA Hubble Space Telescope. This distorted galaxy is the wreckage of a head-on collision between two spiral galaxies which likely occurred 500 million years ago, and it is studded with clumps of young stars which were formed as gas and dust from the two galaxies collided.

It might not seem obvious why astronomers need multiple different powerful space telescopes. Surely a more powerful telescope is better than a less powerful one? So why are there multiple different telescopes in orbit, either around Earth or around the sun?

The answer is to do with two main factors. One is the telescope's field of view, meaning how much of the sky it looks at. Some telescopes are useful for looking at large areas of the sky in less detail, working as survey telescopes to identify objects for further research or to look at the universe on a large scale -- like the recently launched Euclid mission. While others, like the Hubble Space Telescope, look at small areas of the sky in great detail, which is useful for studying particular objects.

Read more
Hubble image of the week shows an unusual jellyfish galaxy
The jellyfish galaxy JO206 trails across this image from the NASA/ESA Hubble Space Telescope, showcasing a colorful star-forming disk surrounded by a pale, luminous cloud of dust. A handful of foreground bright stars with crisscross diffraction spikes stands out against an inky black backdrop at the bottom of the image. JO206 lies over 700 million light-years from Earth in the constellation Aquarius.

This week's image from the Hubble Space Telescope shows an unusual type of galaxy named for its aquatic look-alike: a jellyfish.

The jellyfish galaxy JO206 is shown below in an image taken using Hubble's Wide Field Camera 3 instrument. Located 700 million light-years away, in the constellation of Aquarius, this image of the galaxy shows both the bright center of the galaxy and its long tendrils reaching out toward the bottom right. It is these tendrils that give jellyfish galaxies their names, and they are formed through a process called ram pressure stripping.

Read more
Hubble scientists create tool for erasing satellite trails from images
This image captures the streak of an Earth-orbiting artificial satellite crossing Hubble's field of view during an observation of "The Mice" interacting galaxies (NGC 4676). A typical satellite trail is very thin and will affect less than 0.5% of a single Hubble exposure. Though in this case the satellite overlaps a portion of the target galaxy, the observation quality is not affected. That's because multiple exposures are taken of the same target. And the satellite trail is not in other frames. Developers at the Space Telescope Science Institute in Baltimore, Maryland, have software that identifies the bad pixels from the satellite photobombing, the extent to which they affect the image, and then flags them. When flagged, scientists can recover the full field of view. Even as the number of satellites increases over the decade, these tools for cleaning the images will still be applicable.

With ever-increasing numbers of satellites in the sky, astronomers have repeatedly expressed worry over how these satellites could impact scientific research. Earlier this year, a study of Hubble Space Telescope observations showed how some images were being ruined by streaks of light coming from satellites -- and while only a small percentage of Hubble images were affected, the authors raised concerns that with the projected number of satellites set to explode in the next decade, the problem could become serious.

Now, astronomers at the Space Telescope Science Institute (STScI), which runs Hubble, have come up with a tool to deal with satellite streaks in Hubble images. "We developed a new tool to identify satellite trails that is an improvement over the previous satellite software because it is much more sensitive. So we think it will be better for identifying and removing satellite trails in Hubble images," said Dave Stark of STScI in a statement.

Read more