Stephenson 2-18 is a remarkable star of great interest to astronomers. Pinpointing its location involves understanding its immense distance and placement within the Milky Way’s intricate structure.
What is Stephenson 2-18?
Stephenson 2-18 is classified as a red supergiant star, and some studies suggest it could even be an extreme red hypergiant. It holds a position as one of the largest and most luminous stars discovered in the Milky Way. Its estimated radius is approximately 2,150 times that of our Sun. This immense size means that if Stephenson 2-18 were at the center of our solar system, its outer layers would extend beyond the orbit of Saturn, possibly reaching Neptune. It also shines with extraordinary brightness, with luminosity estimates varying from 90,000 to 630,000 times that of the Sun.
Pinpointing Its Location in the Cosmos
Stephenson 2-18 resides within our home galaxy, the Milky Way. It is found in a region associated with the open cluster Stephenson 2. This cluster is thought to be situated at the intersection of the northern end of the Milky Way’s central bar and the inner part of the Scutum-Centaurus Arm, also known as the Norma Arm.
The star is located at an approximate distance of 18,900 to 19,000 light-years from Earth. This distance can also be expressed as roughly 5,800 to 6,000 parsecs. However, the exact distance remains somewhat uncertain, with some estimations ranging between 10,000 and 25,000 light-years. This uncertainty stems partly from ongoing discussions about whether Stephenson 2-18 is a true member of the Stephenson 2 cluster or a foreground object.
Where to Find it in the Night Sky
From an Earth-based perspective, Stephenson 2-18 is located within the constellation Scutum, also known as the Shield. While its cosmic address places it deep within our galaxy, observing Stephenson 2-18 directly from Earth presents significant challenges.
The star is not visible to the naked eye. It is heavily obscured by vast amounts of interstellar dust and gas within the Milky Way, which absorb and scatter visible light. For this reason, astronomers rely on infrared telescopes to detect and study Stephenson 2-18, as infrared light can penetrate these dusty veils more effectively.
Why Its Location Matters
The specific location and extreme properties of Stephenson 2-18 offer valuable insights into various astrophysical processes. Studying such a distant and massive star helps astronomers refine their understanding of stellar evolution, particularly the life cycles of the most enormous stars.
The sheer distance to Stephenson 2-18 also underscores the vast scale of our galaxy and the universe beyond. Observing objects so far away helps scientists develop and test methods for measuring cosmic distances. The challenges of detecting and characterizing Stephenson 2-18 due to interstellar dust also inform research into the composition and distribution of matter within the Milky Way.