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Spiral Galaxy NGC 3003
Jon Hofman

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NGC 3003

NCG 3003 is a spiral galaxy located over 55 Mpc(mega parsecs) or 181 million light years from Earth. Viewed with its galactic plane tilted slightly toward earth, it is around 200,000 light years across—twice the size of our own Milky Way. In the lower middle of the picture, a line shows the passage of the asteroid Scheila. This asteroid, which is part of the main asteroid belt of our solar system, passed in front of the field of view of the galaxy on January 21, 2001. The distance traveled by the asteroid while the pictures were being taken was 240 million kilometers.

Classification and Inclination
The galaxy is classified as SB(rs)bc. Formally, this means that it is barred (SB), has some transition rings (rs), a fairly small bulge at the center and rather loose and textured arms (bc). Because spiral galaxies are shaped roughly like flat discs, different viewing perspectives can show very different shapes of the same galaxy. Viewed from Earth, NGC 3003 is tilted at an angle—not edge on, nor face on.

Picture Processing and Color
The picture above is a composite image. In astronomy, almost all images are composites. This means that the picture is made up of several, sometimes many, separate pictures layered on top of each other, rather than the single-exposure photography we are most familiar with. After taking exposures with different color or wavelength filters, software can be used to combine the data into a more accurate or more interesting image. In this case, I combined the data from four different color filters: blue, green, red, and infrared.
The composite color image can tell us interesting things about what’s going in the galaxy. The blue streaks around the outside edge of the galaxy indicate the presence of newly formed stars, very hot and very bright. Bright blobs toward the center of the galaxy are open star clusters containing thousands of stars of roughly the same age. The faint bulge in the middle could contain a black hole.

NCG 3003 blue filter
Optical blue filter from Calvin-Rehoboth telescope

NGC 3003 HI
Radio 21 cm HI from WRST telescope (via NED on NGC3003).

NGC 3003 Ha
6580 Angstroms from CAHA 2.2m telescope (via NED on NGC3003).

The three pictures above are identically scaled. But each picture is of a different wavelength. The top image is blue light from the visible spectrum. The middle picture is at radio wavelength (21 cm). It shows radiation from non-ionized hydrogen (HI). The bottom picture is of ionized hydrogen (Halpha) at 6580 angstroms. The size of the HI region is much greater than what is seen in the optical or Ha images. While the galaxy is 64 kpc across when viewed in the visible spectrum, it is 96 kpc across in the radio bandwidth. This is a 33% increase.

Kutner, Marc L. Astronomy: A Physical Perspective, 2nd ed. Cambridge: Cambridge University Press, 2003.

Elmegreen, Debra M. Galaxies and Galactic Structure. Prentice Hall, 1998. Pages 15-27.

This research has made use of the NASA/IPAC Extragalactic Database (NED) which is operated by the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration.

Right Ascension (J2000) 09:48:36
Declination (J2000) +33:25:00
Filters used blue(B), green(V), red(R), and infrared(I)
Exposure time per filter 6x180, 26x300, and 4x75 seconds in B, 33x180 seconds in V, 33x180 seconds in R, 33x180 seconds in I
Date observed

January 21-22 and February 8,11, 20011



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