Here are three images of the pair of colliding galaxies known as `The Antennae', the best studied galaxy crash in the Universe. The images are taken at progressively longer wavelengths: 0.5 micrometers (visible light), 5.0 micrometers (infrared light) and 850 micrometers ('sub-millimeter' light).

The sharpness of the images is diameter by two quantities: the wavelength at which the image is taken and the diameter of the telescope mirror (camera lens). Increasing the wavelength decreases the sharpness. An image taken at a wavelength of 5 micrometers is 10 times less sharp than an image taken -- through the same lens -- at a wavelength of 0.5 micrometers. The loss of diameter can be compensated by increasing the diameter of the lens. In space, an image taken through a lens with a diameter of 2.5 meters is 10 times sharper than an image taken -- at the same wavelength -- through a lens with a diameter of 0.25 meters.

In the table below you can see that for the three telescopes used to obtain the three images both the wavelength and the diameter of the lens vary. The combined effect on the image sharpness is shown in the final column of the table.

The Antennae as imaged using the ACS camera on the Hubble Space Telescope shows by far the most details. The centers of the two galaxies (the `nuclei') can be recognized by their yellowish color, indicating an old, aging stellar population. Clusters of young massive stars appear blueish. They dominate the one remaining spiral arm of the upper galaxy. Even younger massive stars are hiding in the regions showing up as red. These stars are illuminating their birth clouds, causing them to glow in a very specific shade of red: the finger print of hydrogen atoms. The region showing up as brown in between the two nuclei is where gas clouds from the two colliding galaxies are piling up. This is where the next generation of stars is forming! The region appears dark because large amounts of dust hide the forming and recently formed stars from view. In infrared light the obscuration is far lower, and we can see the new stars illuminating their birth clouds.

The Antennae as imaged using the IRAC infrared camera on the Spitzer Space Telescope shows 30 times less detail than the Hubble Space Telescope image. Not only is the diameter of the telescope mirror of Spitzer 3 times smaller than that of Hubble, also the wavelength of the infrared light is 10 times longer than that of visible light. This results in the 3x10=30 times lower sharpness. Despite the lower sharpness the Spitzer-IRAC image contains valuable information! The false color image shows in red the light produced by PAH molecules indicating where new stars are being formed. In blue/white, the false color image shows where old stars reside: mainly in the nuclei of the two galaxies. The latter appear yellow in the true color image taken by the Hubble telescope.

The Antennae as imaged using the SCUBA camera on the James Maxwell Joint Telescope (JCMT) shows 283 times less detail than the Hubble image. The wavelengths that SCUBA studies are 1700 times longer than those of visible light, but this is compensated by a 6 times larger diameter of the JCMT telescope mirror. This results in a 1700/6=283 times lower sharpness of the SCUBA image compared to Hubble the image. Despite the lack of resolution, the SCUBA image contains valuable information on where in the colliding galaxies the coldest gas clouds are piled up. These are the sites where eventually new stars will form! The brightest of these regions corresponds to a region of very strong obscuration (with a brown hue) in the Hubble image. In 2010, when the ALMA telescope array will be completed, image quality at millimeter wavelengths will improve drastically, offering Hubble quality sharpness at these very long wavelengths. To achieve this, the diameter of the ALMA array can be beefed up to 18 kilometers (compared to 2.5 meters for Hubble)!