Maffei 1&2

These two galaxies are of special interest to infrared astronomers. They are the largest ever to be discovered in infrared, rather than visible, light. They were first noted as anomalous sources on infrared photographic plates in 1968 by the astronomer Paolo Maffei, but within several years were confirmed to be galaxies.

Both galaxies are several arcminutes across in diameter, making them among the largest in the sky. Most other galaxies of their size had been cataloged over a century ago! The reason for their late discovery is that they both lie deep within the dusty plane of our Milky Way Galaxy. This foreground dust (spread out hundreds to thousands of parsecs away) blocks our visible light view of these more distant objects (several million parsecs away).

In the infrared this obscuring dust becomes increasingly transparent, allowing us to see these hidden galaxies. Their yellowish infrared colors are caused by the same effect that reddens the sun at sunset: the bluer, shorter wavelengths of light are blocked more effectively by the dust allowing only the redder, longer wavelengths through.

Maffei 1 is a classic elliptical galaxy while Maffei 2 has a strong bar and obvious, if somewhat asymmetric spiral arms. A strong burst of massive star formation is ongoing in the core of Maffei 2, deduced from strong far infrared and radio emissions, that is possibly driven by an ongoing merger with a small satellite companion galaxy.