M33 in radio and optical

Minimum credit line: Image courtesy of NRAO/AUI and NOAO/AURA/NSF(for details, see Image Use Policy).

About this Image

This image of the Triangulum Galaxy was created by combining optical data from the National Science Foundation's 0.9-meter telescope on Kitt Peak in Arizona with radio data from the National Science Foundation's Very Large Array (VLA) telescope in New Mexico and the Westerbork Synthesis Radio Telescope (WSRT) in the Netherlands. Also known as M33, the Triangulum Galaxy is part of the Local Group of galaxies, which includes the Andromeda Galaxy (M31) and our galaxy, the Milky Way. M33 is over thirty thousand light years across, and more than two million light years away.

The optical data in this image show the many stars within the galaxy as well as reddish star forming regions that are filled with hot Hydrogen gas. The radio data reveal the cool Hydrogen gas within the galaxy, gas which cannot be seen with an optical telescope. Combined together, the radio and optical give a more comprehensive view of star formation in this galaxy. The color image was generated by combining images taken with the 0.9-meter telescope through four filters (B, V, I and Hydrogen-alpha) and 21cm neutral Hydrogen data taken with the VLA and WSRT (shown in blue-violet). The image is one square degree in field of view, roughly five times the size of the Moon. A very high resolution (8107 x 8270 pixels) version of this image is available on request.

Investigator(s):  Travis Rector, David Thilker and Robert Braun

Alternate Resolutions Help

This image is available in the following downloadable versions:If you would like to obtain a higher resolution version of this image, please contact us.

For More Information

Technical Data

    Telescope VLA 
    Date of Observation 1998-08-15 
    Type of Observation Spectral Line Observations 
    Wavelength 21 cm 
    Frequency 1420.4 MHz 
    Species HI 
    Center of Image RA: 01:33:51.02, Dec: 30:39:36.70 (J2000)  
    Field of View 1.0000 x 1.0000 degrees  
    Technical Caption The radio data were obtained from VLA observations taken both in its B-array and CS-array configurations, with a spatial resolution of 10" and velocity resolution of 1.3 km/s. The VLA data have been supplemented by total power observations obtained at the Westerbork Synthesis Radio Telescope.  

  • Astronomical database entries for M33
    • Query NED for images of M33
    • Query SIMBAD for more M33 data


To search the Image Gallery for other images of M33, click the Submit button.
Object Name Show Results As:

To search the Image Gallery for similar images, click the Submit button.
Category Sub-Category Telescope Mode Show Results As:

For more search options, please use our Advanced Search form.