Why are distant open clusters difficult to see in the plane of the Milky Way?
Most of the brightest stars are older yellow stars, but a few young blue stars are also visible. This picture is a composite of three images taken by the Hubble Space Telescope.
Distant open clusters located in the plane of the Milky Way are difficult to observe because of the presence of interstellar dust.1
This dust, which is pervasive throughout the galactic plane, obscures and reddens starlight, causing objects to fade significantly as distance increases. Consequently, any open cluster situated more than a few thousand light-years from the Sun is typically hidden from optical view by this material. While these clusters are highly concentrated along the galactic plane, this obscuration makes it challenging for astronomers to study their large-scale distribution directly.21
To overcome these limitations, researchers have utilized infrared array detectors, which can penetrate the dust to reveal young star groups that were previously hidden.1