The James Webb Space Telescope has captured the Cartwheel galaxy in unparalleled detail in a breathtaking composite from Webb’s Near-Infrared Camera (NIRCam) and Mid-Infrared Instrument (MIRI).
The Cartwheel Galaxy, known to astronomers as ESO 350-40 or PGC 2248, was first discovered by the Swiss astronomer Fritz Zwicky in 1941. It’s span is estimated at 150,000 light years, slightly smaller than the Andromeda Galaxy.
The Cartwheel, positioned about 500 million light-years from Earth in the constellation Sculptor, took its current shape in a dramatic head-on collision between two galaxies. The impact sent two rings expanding from the galaxy’s center,
“like ripples in a pond after a stone is tossed into it”,
NASA and the ESA said.
An Ever Expanding 440 Million Year Old Ring
This image from Webb’s Mid-Infrared Instrument (MIRI) shows a group of galaxies, including a large distorted ring-shaped galaxy known as the Cartwheel. The Cartwheel Galaxy, located 500 million light-years away in the Sculptor constellation, is composed of a bright inner ring and an active outer ring. While this outer ring has a lot of star formation, the dusty area in between reveals many stars and star clusters.
Credit: NASA, ESA, CSA, STScI, Webb ERO Production Team
Nearer to the galaxy’s center, a smaller nucleic white ring lingers. The outer ring, with its spokes of colour, has been expanding into the universe for around 440 million years, the statement added. Multiple optical arms or spokes, observed connecting the outer ring to the inner, are theorized to be reforming spiral arms following the collision.
As the outer ring continues to expand, it runs into gas, triggering the formation of new stars.
Previously, in 2007, the Hubble telescope had snapped images of the ring galaxy, which is believed to have been a spiral galaxy like our own Milky Way before it was hit by a smaller intruder galaxy. The Webb telescope, launched in December 2021, has a far greater reach.
Hubble Space Telescope true-color image of the Cartwheel Galaxy.
Credit: Kirk Borne (ST ScI), and NASA/ESA
Webb’s ability to detect infrared light revealed new details about star formation in the galaxy, as well as the behaviour of the supermassive black hole at its heart, NASA and the ESA said.
Cartwheel Galaxy Still In Transitory Stage
The observations indicate that the Cartwheel Galaxy is still in a
“very transitory stage,”
the space agencies said.
“While Webb gives us a snapshot of the current state of the Cartwheel, it also provides insight into what happened to this galaxy in the past and how it will evolve in the future,”
they added.
Galaxy PGC 2248 X-ray Sources
When gigantic stars explode as supernovas, they leave behind neutron stars and black holes. Some of these neutron stars and black holes have nearby companion stars, and become powerful sources of X-rays as they pull matter off their companions.
The brightest X-ray sources are most probably black holes that have companion stars. They appear as the white dots that lie along the rim of the X-ray image of Galaxy PGC 2248. The Cartwheel contains an unusually large number of these black hole binary X-ray sources, because many massive stars formed in the ring.
How Many Stars Are In The Cartwheel Galaxy?
The outer ring alone has at least several billion young stars. It is so large that the Milky Way could easily fit inside of it. Its estimated mass is between 2.9 and 4.8 billion solar masses.
In the local universe, the Cartwheel Galaxy is one of the brightest sources of ultraviolet emission. It rotates at a speed of 217 km/s and is moving away from us at 9,050 km/s.
