From Simple English Wikipedia, the free encyclopedia
The Milky Way hides galaxies behind it from our view
The
Zone of Avoidance
(ZOA) is the area of the night sky that is obscured by our own
galaxy
, the
Milky Way
.
Dust
and
stars
in the plane of the Milky Way (the
galactic plane
) block our view of about 20% of the sky at
visible
wavelengths
. As a result, optical galaxy catalogues are usually very incomplete close to the galactic plane.
In more recent years, many projects have attempted to bridge the gap in our knowledge caused by the Zone of Avoidance. However, the effects of the Zone drops at longer wavelengths, such as the
infrared
, and the Milky Way is effectively
transparent
at
radio
wavelengths. Surveys in the infrared have given us a more complete picture of the extragalactic sky. Indeed, two very large nearby galaxies,
Maffei 1
and
Maffei 2
, were discovered in the Zone of Avoidance by
Paolo Maffei
by their infrared emission in 1968. Even so, about 10% of the sky remains difficult to survey because extragalactic objects (for example, distant galaxies) can be confused with stars in the Milky Way.
Projects to survey the Zone of Avoidance at radio wavelengths have detected many galaxies that could not be detected in the infrared. Examples of galaxies detected from their HI emission include
Dwingeloo 1
and
Dwingeloo 2
.
Important superclusters of galaxies lying hidden or partly hidden by ZOA are The
Great Attractor
and the
Norma Cluster
.