referred to as the fifth feature in the Milky Way. The “spur” interpretation may be incorrect. To understand the form of the Local Arm between the Sagittarius and Perseus arms, the stellar density of a specific population of stars with about 1 Gyr of age between 90° ≤ l ≤ 270° have been mapped using the Gaia DR2. The 1 Gyr population have been employed because they are significantly more-evolved objects than the gas in HMSFRs tracing the Local Arm. Investigations have been carried out to compare both the stellar density and gas distribution along the Local Arm. Researchers have found a marginally significant arm-like stellar overdensity close to the Local Arm, identified with the HMSFRs especially in the region of 90° ≤ l ≤ 190°. They have concluded that the Local Arm is the arm segment associated with only the gas and star-forming clouds, with a significant stellar overdensity. Additionally, they have found that the pitch angle of the stellar arm is slightly larger than the gas-defined arm, and also there is an offset between gas-defined and stellar arm. The offset and different pitch angles between the stellar and HMSFR-defined spiral arms are consistent with the expectation that star formation lags the gas compression in a spiral density wave lasting longer than the typical star formation timescale of 107 − 108 years. Messier objects The Orion Arm contains a number of Messier objects: The Butterfly Cluster (M6) The Ptolemy Cluster (M7) Open Cluster M23 Open Cluster M25 The Dumbbell Nebula (M27) Open Cluster M29 Open Cluster M34 Open Cluster M35 Open Cluster M39 Winnecke 4 (M40) Open Cluster M41 The Orion Nebula (M42) The De Mairan's Nebula (M43) The Beehive Cluster (M44) The Pleiades (M45) Open Cluster M46 Open Cluster M47 Open Cluster M48 Open Cluster M50 The Ring Nebula (M57) Open Cluster M67 M73 The Little Dumbbell Nebula (M76) Diffuse Nebula M78 Open Cluster M93 The Owl Nebula (M97) Interactive maps Other maps See also Galactic disc Gould Belt Jon Lomberg's Milky Way painting used as background for Kepler Mission diagram, showing our location on the Orion Spur Local Bubble Loop I Bubble List of Messier objects List of nearest stars and brown dwarfs References External links Messier Objects in the Milky Way (SEDS) A 3D map of the Milky Way Galaxy Milky Way arms Galactic astronomy Spiral galaxies