Webb Captures Stellar Gymnastics in The Cartwheel Galaxy
By NASA
The Cartwheel Galaxy, located about 500 million light-years away
in the Sculptor constellation, is a rare sight. Its appearance, much like that
of the wheel of a wagon, is the result of an intense event – a high-speed
collision between a large spiral galaxy and a smaller galaxy not visible in
this image. Collisions of galactic proportions cause a cascade of different,
smaller events between the galaxies involved; the Cartwheel is no exception.
The collision most notably affected the galaxy’s shape and
structure. The Cartwheel Galaxy sports two rings — a bright inner ring and a
surrounding, colorful ring. These two rings expand outwards from the center of
the collision, like ripples in a pond after a stone is tossed into it. Because
of these distinctive features, astronomers call this a “ring galaxy,” a
structure less common than spiral galaxies like our Milky Way.
The bright core contains a tremendous amount of hot dust with the
brightest areas being the home to gigantic young star clusters. On the other
hand, the outer ring, which has expanded for about 440 million years, is
dominated by star formation and supernovas. As this ring expands, it plows into
surrounding gas and triggers star formation.
Other telescopes, including the Hubble Space Telescope, have previously examined the Cartwheel. But the dramatic galaxy has been shrouded in mystery – perhaps literally, given the amount of dust that obscures the view. Webb, with its ability to detect infrared light, now uncovers new insights into the nature of the Cartwheel.
The Near-Infrared Camera (NIRCam), Webb’s primary imager, looks in the near-infrared range from 0.6 to 5 microns, seeing crucial wavelengths of light that can reveal even more stars than observed in visible light. This is because young stars, many of which are forming in the outer ring, are less obscured by the presence of dust when observed in infrared light.
In this image, NIRCam data are colored blue, orange, and yellow. The galaxy displays many individual blue dots, which are individual stars or pockets of star formation. NIRCam also reveals the difference between the smooth distribution or shape of the older star populations and dense dust in the core compared to the clumpy shapes associated with the younger star populations outside of it.
Learning finer details about the dust that inhabits the galaxy,
however, requires Webb’s Mid-Infrared
Instrument (MIRI). MIRI data are colored red in this
composite image. It reveals regions within the Cartwheel Galaxy rich in
hydrocarbons and other chemical compounds, as well as silicate dust, like much
of the dust on Earth. These regions form a series of spiraling spokes that essentially
form the galaxy’s skeleton. These spokes are evident in previous Hubble
observations released in 2018, but they become much more
prominent in this Webb image.
Webb’s observations underscore that the Cartwheel is in a very
transitory stage. The galaxy, which was presumably a normal spiral galaxy like
the Milky Way before its collision, will continue to transform. 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.
The James Webb Space Telescope is the world's premier space
science observatory. Webb will solve mysteries in our solar system, look beyond
to distant worlds around other stars, and probe the mysterious structures and
origins of our universe and our place in it. Webb is an international program
led by NASA with its partners, ESA (European Space Agency) and the Canadian
Space Agency.