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Sextans A Context Image (Webb and KPNO)

Two panels showing different views of a small galaxy. The left panel, labeled Webb, shows a region of space filled with stars and small clumps of glowing orange and tan dust. The right panel is labeled KPNO. This image shows stars on the black background of space, with a higher concentration of them in a globe at the center. On the edges of this circular globe, there are puffs of pink gas. A small portion of the of the galaxy in the right panel is outlined with a white box, and the image from the left panel appears in that box at a 45-degree angle. Lines extend from the corner of the box to the panel at the left.

NASA’s James Webb Space Telescope’s image of a portion of the nearby Sextans A galaxy is put into context using a ground-based image from the Nicholas U. Mayall 4-meter Telescope at Kitt Peak National Observatory. The image from Webb shows the galaxy in both near- and mid-infrared light, while Kitt Peak captures optical, or visible, light.

Sextans A is an irregular dwarf galaxy, and is only 4 million light-years away, which is nearby to the Milky Way in relative terms. It’s also a fairly small galaxy, measuring 5,000 light-years across (the Milky Way is about 100,000 light-years across). Sextans A is chemically primitive, meaning it has a very low content of metals heavier than hydrogen and helium.

About the Object

  • R.A. Position
    R.A. PositionRight ascension – analogous to longitude – is one component of an object's position.
    10:11:02.11
  • Dec. Position
    Dec. PositionDeclination – analogous to latitude – is one component of an object's position.
    -04:42:49.55
  • Constellation
    ConstellationOne of 88 recognized regions of the celestial sphere in which the object appears.
    Sextans
  • Distance
    DistanceThe physical distance from Earth to the astronomical object. Distances within our solar system are usually measured in Astronomical Units (AU). Distances between stars are usually measured in light-years. Interstellar distances can also be measured in parsecs.
    About 4.4 million light-years
  • Dimensions
    DimensionsThe physical size of the object or the apparent angle it subtends on the sky.
    Pull-out image is 1.65 arcminutes across (about 2,000 light-years)

About the Data

  • Data Description
    Data DescriptionProposal: A description of the observations, their scientific justification, and the links to the data available in the science archive.
    Science Team: The astronomers who planned the observations and analyzed the data. "PI" refers to the Principal Investigator.

    The Webb image on the left was was created with Webb data from proposal: 2391 (J. Roman-Duval)

  • Instrument
    InstrumentThe science instrument used to produce the data.
    Left image: Webb> NIRCam, MIRI Right image: Nicholas U. Mayall 4-meter Telescope, KPNO> Mosaic 1
  • Exposure Dates
    Exposure DatesThe date(s) that the telescope made its observations and the total exposure time.
    Webb> 02-04 Jan. 2023, 13 April 2023
  • Filters
    FiltersThe camera filters that were used in the science observations.
    Left> NIRCam: F115W, F150W, F200W, F335M MIRI: F560W, F770W, F1000W, F1130W Right>  F355W; F438W; F502N; F538W; F651W; F820W; F657N; F673N
  • Object Name
    Object NameA name or catalog number that astronomers use to identify an astronomical object.
    Sextans A, UGCA 205
  • Object Description
    Object DescriptionThe type of astronomical object.
    Irregular, dwarf galaxy
  • Release Date
    January 6, 2026
  • Science Release
    NASA Webb Finds Early-Universe Analog’s Unexpected Talent for Making Dust
    Read the release
  • Credit
    Image: STScI, NASA, ESA, CSA, KPNO, NSF's NOIRLab, AURA, Elizabeth Tarantino (STScI), Phil Massey (Lowell Obs.), George Jacoby (NSF, AURA), Chris Smith (NSF, AURA); Image Processing: Alyssa Pagan (STScI), Travis Rector (UAA), Mahdi Zamani (NSF's NOIRLab), Davide De Martin (NSF's NOIRLab)

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Two panels showing different views of a small galaxy. The left panel, labeled Webb, shows a region of space filled with stars and small clumps of glowing orange and tan dust. The right panel is labeled KPNO. This image shows stars on the black background of space, with a higher concentration of them in a globe at the center. On the edges of this circular globe, there are puffs of pink gas. A small portion of the of the galaxy in the right panel is outlined with a white box, and the image from the left panel appears in that box at a 45-degree angle. Lines extend from the corner of the box to the panel at the left.
Color Info
Color InfoA brief description of the methods used to convert telescope data into the color image being presented.

The left image is a composite of separate exposures acquired by the James Webb Space Telescope using the NIRCam and MIRI instruments. Several filters were used to sample specific wavelength ranges. The color results from assigning different hues (colors) to each monochromatic (grayscale) image associated with an individual filter. In this case, the assigned colors are:  Blue= F115W, Cyan= F150W+F200W, Green= F335M, Yellow= F560W, Orange= F770W, Red=F1000W+F1130W The right image is a composite of separate exposures acquired by the Nicholas U. Mayall 4-meter Telescope using the Mosaic I instrument. Several filters were used to sample specific wavelength ranges. The color results from assigning different hues (colors) to each monochromatic (grayscale) image associated with an individual filter. In this case, the assigned colors are:  Purple= F355W, Blue= F438W, Cyan= F502N, Green= F538W, Yellow= F651W, Orange= F820W, Red= F657N, Magenta= F673N    

Related Images & Videos

A region of space is filled with stars and clumps of glowing orange and tan dust. A small portion of the sky at the center of the image is outlined with a white box. Lines extend from the corner of the box to the inset panel at the top right showing a magnified version of the outlined portion of the image. In the inset, there are smatterings of dim whitish-blueish stars and about seven glowing red orbs across the center in a line. Also across the center of the inset is a green glow. The background of the image is filled with stars and galaxies of various shapes and colors.

Sextans A PAHs Pull-out (NIRCam and MIRI Image)

Images from NASA’s James Webb Space Telescope of the dwarf galaxy Sextans A reveal polycyclic aromatic hydrocarbons (PAHs), large carbon-based molecules that can be a signifier of star formation. The inset at the top right zooms in on those PAHs, which are represented in green.

Image titled u201cJames Webb Space Telescope; Sextans A, UGCA 205,u201d with compass arrows, scale bar, and color key. At the left, a region of space is filled with stars and clumps of glowing orange and tan dust. A small portion of the sky at the center of the image is outlined with a white box. In the inset, there are smatterings of dim whitish-blueish stars and about seven glowing red orbs across the center in a line. Also across center of the image is a green glow. At the bottom left are compass arrows indicating the orientation of the image on the sky. The east arrow points toward 2 ou2019clock. The north arrow points in the 10 ou2019clock direction. At the bottom left is a scale bar labeled 300 light-years, 15 arcsec. The length of the scale bar is about one tenth of the total image. Below the image is a color key showing which NIRCam and MIRI filters were used to create the image and which visible-light color is assigned to each filter.

Sextans A PAHs Pull-out (Compass Image)

This image of dwarf galaxy Sextans A, captured by NASA’s James Webb Space Telescope’s Near Infrared Camera (NIRCam) and Mid-Infrared Instrument (MIRI), shows compass arrows, scale bar, and color key for reference.

Graphic titled u201cGiant Star in Dwarf Galaxy Sextans A: Iron-Rich Dust at Low Metallicitiesu201d showing a graph of brightness versus wavelength, with two sets of data and two model spectra. One set of data is represented in 12 orange triangle data points, and the other is a solid yellow line. A cyan solid line represents u201cIron + 0.8% silicatesu201d and a red dashed line represents u201cIron + 5% silicates.u201d They appear on a graph of Brightness on the y-axis versus Wavelength of Light in microns on x-axis. The y-axis ranges from dimmer at bottom to brighter at top. The x-axis ranges from 0 to 12 microns.

Giant Star in Dwarf Galaxy Sextans A (Spectrum)

This graph shows a spectrum of an Asymptotic Giant Branch (AGB) star in the Sextans A galaxy. It compares data collected by NASA’s James Webb Space Telescope with models of mostly silicate-free dust and dust containing at least 5% silicates.

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Details

Last Updated
Jan 06, 2026
Location
NASA Goddard Space Flight Center
Contact
Media

Laura Betz
NASA’s Goddard Space Flight Center
Greenbelt, Maryland
laura.e.betz@nasa.gov

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