HI Disk of NGC 2403



NGC 2403 is a well-known spiral galaxy in the northern sky. Galaxies such as NGC 2403 contain, apart from billions of stars that are visible in the right image, a large disk of hydrogen gas. This gas emits radio waves that can be detected with radio telescopes. The image on the left shows, on the same scale as the optical image, the hydrogen disk of NGC 2403 as observed with the VLA C array. Seen on the sky, the size of this gas disk is about the same as that of the full moon. The images shows that the gas disk extends well beyond the optical galaxy. The gas disk shows the spiral structure of the disk, as well as large holes created by large supernova explosions.
Right: optical image of NGC 2403 based on images taken from the Digitized Sky Survey. The image on the left shows the total HI image of the gas disk of the spiral galaxy NGC 2403. The radio image is based on deep observations with the VLA C array (total integration time 48 hr) and covers an area of about 40 arcmin x 40 arcmin.


Legacy Astronomical Images


NRAO/AUI/NSF does not hold full copyright for this image. Contact the archivist for details.


Legacy Astronomical Image

Object Name

NGC 2403

Photo Credit

Tom Oosterloo, Astron, The Netherlands


Fraternali, Oosterloo, Sancisi


Very Large Array (VLA)

Type of Observation

spectral line

Center of Image

RA 7:36:51.000, Dec: 65:0:0.000 (J2000)

Field of View

0.666667 x 0.666667 degrees

Link to journal article


Contact the archivist for a high resolution tif of this image.


Galaxies Series


Spiral Unit


Legacy Astronomical Images, “HI Disk of NGC 2403,” NRAO Archives, accessed May 17, 2022, https://www.nrao.edu/archives/items/show/33577.