Skip to main content

A galaxy with layers like an onion shines in Dark Energy Camera image

A new image taken by the Dark Energy Camera shows a “galactic onion,” a shell galaxy with multiple layers that are spread out over a distance of 150,000 light-years. At around twice the size of the Milky Way, the galaxy NGC 3923 is large, but even larger is a nearby galaxy cluster that has so much mass that it is bending space-time, making the light from distant galaxies behind it bend like a magnifying glass in a process called gravitational lensing.

The Dark Energy Camera is ground-based instrument located at the Víctor M. Blanco 4-meter Telescope in Chile and was originally built to observe many galaxies as part of a project called the Dark Energy Survey. Now, it is also used for other observations such as imaging dwarf galaxies, merging galaxies, and more.

The symmetrical, onion-like layers of shell galaxy NGC 3923 are showcased in this galaxy-rich image taken by the US Department of Energy’s (DOE) Dark Energy Camera mounted on the National Science Foundation’s (NSF) Víctor M. Blanco 4-meter Telescope at Cerro Tololo Inter-American Observatory in Chile, a Program of NSF’s NOIRLab. A nearby, massive galaxy cluster is also captured exhibiting the phenomenon known as gravitational lensing.
The symmetrical, onion-like layers of shell galaxy NGC 3923 are showcased in this galaxy-rich image taken by the U.S. Department of Energy Dark Energy Camera mounted on the National Science Foundation’s (NSF) Víctor M. Blanco 4-meter Telescope at Cerro Tololo Inter-American Observatory in Chile. A nearby, massive galaxy cluster is also captured exhibiting the phenomenon known as gravitational lensing. DESI Legacy Imaging Surveys/LBNL/DOE & KPNO/CTIO/NOIRLab/NSF/AURA Image processing: T.A. Rector (University of Alaska Anchorage/NSF’s NOIRLab), M. Zamani (NSF’s NOIRLab), R. Colombari (NSF’s NOIRLab) & D. de Martin (NSF’s NOIRLab)

The main feature of this image is the shell galaxy, which is a type of elliptical galaxy in which the stars are not spread evenly, but are instead arranged into shell-like structures. Spiral galaxies like the Milky Way don’t have this arrangement of stars, but it is thought that around one-tenth of elliptical galaxies do, and that the structure is created when two galaxies merge and a larger galaxy absorbs a smaller companion.

Two galaxies merging was what happened here, as NOIRLab explains: “As they merged, the larger galaxy’s gravitational field slowly peeled off stars from the smaller galaxy’s disk. Those stars began to gradually mix with the larger galaxy’s outer halo, forming concentric bands, or shells. A simple analogy is adding a drop of food color to a bowl of batter that you’re slowly stirring. The drop gets stretched out in a spiral that remains visible for a long time before completely mixing.”

The other important feature of this image is harder to see, but is located at the top center. A massive galaxy cluster called PLCK G287.0+32.9 is bending space-time and warping the light coming from distant galaxies, making them appear stretched out.

To see the image in its full glory and to appreciate all the details, a large zoomable version of the image is available on the NOIRLab website.

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
This one instrument has surveyed 2 million objects to understand dark energy
The Dark Energy Spectroscopic Instrument (DESI) making observations in the night sky on the Nicholas U. Mayall 4-meter Telescope at Kitt Peak National Observatory in Arizona.

The vastness of the universe is hard to comprehend, let alone map, but a cosmological project from the National Science Foundation's NOIRLab aims to do just that. The Dark Energy Spectroscopic Instrument (DESI) is designed to create a 3D map of millions of astronomical objects, and an early release of data from the project combines the thousands of exposures taken by the instrument during its validation phase in 2020 and 2021. It contains nearly 2 million objects.

The video below shows part of the survey validation data, with detailed portions of the sky shown in 20 different directions. Each "beam" of light is one part of the data, showing objects like stars, galaxies, and quasars. There are over 700,000 objects in this 3D map, and as impressive as that is, this represents just 1% of the total volume that will be mapped out in the DESI survey.

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