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Astronomy

Webb and Hubble examine spooky spiral galaxies: IC 2163 and NGC 2207

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Webb and Hubble examine spooky spiral galaxies: IC 2163 and NGC 2207

Stare deeply at these galaxies. They appear as if blood is pumping through the top of a flesh-free face. The long, ghastly ‘stare’ of their searing eye-like cores shines out into the supreme cosmic darkness.

Two spiral galaxies take up almost the entire view and appear to be overlapping. The galaxy at left, IC 2163, is smaller and more compact than the galaxy at right, NGC 2207. The black background of space is dotted with foreground stars and extremely distant galaxies.
The gruesome palette of these galaxies is owed to a mix of mid-infrared light from the NASA/ESA/CSA James Webb Space Telescope, and visible and ultraviolet light from the NASA/ESA Hubble Space Telescope. The pair grazed one another millions of years ago. The smaller spiral on the left, catalogued as IC 2163, passed behind NGC 2207, the larger spiral galaxy at right.
Both have increased star formation rates. Combined, they are estimated to form the equivalent of two dozen new stars that are the size of the Sun annually. Our Milky Way galaxy forms the equivalent of two or three new Sun-like stars per year.
Both galaxies have hosted seven known supernovae, each of which may have cleared space in their arms, rearranging gas and dust that later cooled, and allowed many new stars to form. (Find these areas by looking for the bluest regions).
Credit: NASA, ESA, CSA, STScI

These galaxies have only grazed one another so far, with the smaller spiral on the left, catalogued as IC 2163, ever so slowly ‘creeping’ behind NGC 2207, the spiral galaxy on the right, millions of years ago.

The pair’s macabre colours represent a combination of mid-infrared light from the NASA/ESA/CSA James Webb Space Telescope and visible and ultraviolet light from the NASA/ESA Hubble Space Telescope.

Look for potential evidence of their ‘light scrape’ in the shock fronts, where material from the galaxies may have slammed together. These lines represented in brighter red, including the ‘eyelids’, may cause the appearance of the galaxies’ bulging, vein-like arms.

The galaxies’ first pass may have also distorted their delicately curved arms, pulling out tidal extensions in several places. The diffuse, tiny spiral arms between IC 2163’s core and its far left arm may be an example of this activity. Even more tendrils look like they’re hanging between the galaxies’ cores. Another extension ‘drifts’ off the top of the larger galaxy, forming a thin, semi-transparent arm that practically runs off screen.

Both galaxies have high star formation rates, like innumerable individual hearts fluttering all across their arms. Each year, the galaxies produce the equivalent of two dozen new stars that are the size of the Sun. Our Milky Way galaxy only forms the equivalent of two or three new Sun-like stars per year. Both galaxies have also hosted seven known supernovae in recent decades, a high number compared to an average of one every 50 years in the Milky Way. Each supernova may have cleared space in the galaxies’ arms, rearranging gas and dust that later cooled, and allowed many new stars to form.

To spot the star-forming ‘action sequences,’ look for the bright blue areas captured by Hubble in ultraviolet light, and the pink and white regions detailed mainly by Webb’s mid-infrared data. Larger areas of stars are known as super star clusters. Look for examples of these in the top-most spiral arm that wraps above the larger galaxy and points left. Other bright regions in the galaxies are mini starbursts — locations where many stars form in quick succession. Additionally, the top and bottom ‘eyelid’ of IC 2163, the smaller galaxy on the left, is filled with newer star formation and burns brightly.

A graphic labelled “Hubble and Webb Space Telescopes; Spiral Galaxies IC 2163 and NGC 2207.” At the centre are two overlapping spiral galaxies set against the black background of space.
This image of galaxies IC 2163 and NGC 2207, captured by the Hubble and James Webb space telescopes. Hubble’s data are from its Wide Field Planetary Camera 2 (WFPC2). Webb’s data are from its Mid-InfraRed Instrument (MIRI).
The image shows a scale bar, compass arrows, and colour key for reference.
The scale bar is labelled in light-years along the top, which is the distance that light travels in one Earth-year. (It takes three years for light to travel a distance equal to the length of the scale bar.) One light-year is equal to about 9.46 trillion kilometres.
The scale bar is also labelled in arcminutes, which is a measure of angular distance on the sky. One arcsecond is equal to an angular measurement of 1/3600 of one degree. There are 60 arcminutes in a degree and 60 arcseconds in an arcminute. (The full Moon has an angular diameter of about 30 arcminutes.) The actual size of an object that covers one arcsecond on the sky depends on its distance from the telescope.
The north and east compass arrows show the orientation of the image on the sky. Note that the relationship between north and east on the sky (as seen from below) is flipped relative to direction arrows on a map of the ground (as seen from above).
This image shows invisible ultraviolet, visible, and mid-infrared wavelengths of light that have been translated into visible-light colours. The colour key shows which WFPC2 and MIRI filters were used when collecting the light. The colour of each filter name is the visible-light colour used to represent the infrared light that passes through that filter.
Credit: NASA, ESA, CSA, STScI

What’s next for these spirals? Over many millions of years, the galaxies may swing by one another repeatedly. It’s possible that their cores and arms will meld, leaving behind completely reshaped arms, and an even brighter, cyclops-like ‘eye’ at the core. Star formation will also slow down once their stores of gas and dust deplete, and the scene will calm.

Two spiral galaxies take up almost the entire view and appear to be overlapping. They are angled from top left to bottom right. The galaxy at left, IC 2163, is smaller and more compact than the galaxy at right, NGC 2207. The background of space is black, dotted with tiny foreground stars and extremely distant galaxies.
The James Webb Space Telescope’s mid-infrared image of galaxies IC 2163 and NGC 2207 recalls the iciness of long-dead bones mixed with eerie vapours. Two large luminous ‘eyes’ lie at the galaxies’ cores, and gauzy spiral arms reach out into the vast distances of space.
Webb’s mid-infrared image excels at showing where the cold dust glows throughout these galaxies — and helps pinpoint where stars and star clusters are buried within the dust. Find these regions by looking for the pink dots along the spiral arms. Many of these areas are home to actively forming stars that are still encased in the gas and dust that feeds their growth. Other pink dots may be objects that lie well behind these galaxies, including extremely distant active supermassive black holes known as quasars.
The largest, brightest pink region that glimmers with eight prominent diffraction spikes at the bottom right is a mini starburst — a location where many stars are forming in quick succession. Find the lace-like holes in the spiral arms. These areas are brimming with star formation.
Finally, scan the black background of space, where objects shine brightly in a rainbow of colours. Blue circles with tiny diffraction spikes are foreground stars. Objects without spikes are very distant galaxies.
Credit: NASA, ESA, CSA, STScI

Want to ‘pull apart’ these images? Examine the galaxies’ skeleton-like appearance in Webb’s mid-infrared image, and compare the Hubble and Webb images side by side.

Two views of the same object are shown side by side, split evenly. The Hubble observation is at left, and the Webb observation is at right. Both show an angled pair of spiral galaxies, IC 2163 at top left, and NGC 2207, at bottom right.
These are two views of the same scene, each showing two overlapping spiral galaxies, IC 2163 at left and NGC 2207 at right. The NASA/ESA Hubble Space Telescope’s ultraviolet- and visible-light observation is at left, and the NASA/ESA/CSA James Webb Space Telescope’s mid-infrared light observation is at right.
In Hubble’s image, the star-filled spiral arms glow brightly in blue, and the galaxies’ cores in orange. Both galaxies are covered in dark brown dust lanes, which obscure the view of IC 2163’s core at left.
In Webb’s image, cold dust takes centre stage, casting the galaxies’ arms in white. Areas where stars are still deeply embedded in the dust appear pink. Other pink dots may be objects that lie well behind these galaxies, including active supermassive black holes known as quasars.
Turn your eye toward the bottom right of the Webb image. The largest, brightest pink region that glimmers with eight prominent diffraction spikes is a mini starburst — a location where many stars are forming in quick succession. The same region in the Hubble image appears as a bright blue cluster of stars.
The lace-like holes in the white spiral arms of Webb’s images are often where supernovae exploded long ago. In the same regions, Hubble shows these areas are now populated with newer stars.
The black areas to the upper right and lower left of the Hubble image do not contain any data.
Credit: NASA, ESA, CSA, STScI

 

Press release from ESA Webb.

ScientifiCult è una Testata Giornalistica registrata presso il Tribunale di Bari numero R.G. 5296/2021 - R.S. 21. Direttrice Responsabile: Alessandra Randazzo

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