There are many astronomical object types that come under the description of deep-sky objects. These objects are called “Deep Sky” because they are difficult to find with the naked-eye and almost impossible to find from cities owing to light pollution. However, if you are situated away from the cities with dark, clear skies you should be able to spot many of them with even basic binoculars or a small telescope. The majority of the Deep Sky Objects are classified into

  • Star clusters
    • Open clusters
    • Globular clusters
  • Nebulae
    • Bright nebulae
      • Emission nebulae
      • Reflection nebulae
    • Dark nebulae
    • Planetary nebulae
  • Galaxies

You would have read about these in detail in https://www.awestronomy.com/celestial-objects-galaxies-and-everything-else/

The Messier objects are a set of 110 astronomical objects, of which 103 were included in lists published by French astronomer Charles Messier in the late Eighteenth century. Messier was a comet hunter, and was frustrated by objects which resembled but were not comets, so he compiled a list of them to avoid wasting time on them. In addition to the 103 items published by Messier, seven more are thought to have been observed by Messier and have been added to the list by other astronomers over the years.

The Messier catalogue comprises nearly all the most spectacular examples of the five types of deep-sky object – diffuse nebulae, planetary nebulae, open clusters, globular clusters, and galaxies – visible from European latitudes. Furthermore, almost all of the Messier objects are among the closest to Earth in their respective classes, which makes them heavily studied with professional class instruments that today can resolve very small and visually spectacular details in them.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Since these objects could be observed visually with the relatively small-aperture refracting telescope (approximately 100 mm, or 4 inches) used by Messier to study the sky, they are among the brightest and thus most attractive astronomical objects observable from Earth, and are popular targets for visual study and astrophotography available to modern amateur astronomers using larger aperture equipment.

 

To know more about each of the Messier Objects in detail, do visit the links below.

http://www.seasky.org/astronomy/astronomy-messier.html

https://www.nasa.gov/content/goddard/hubble-s-messier-catalog