NGC 1555 - Herbig-Haro Object

NGC 1555, also known as the Hind Variable Nebula, is a reflection nebula in the constellation Taurus.

This is the nebula that surrounds the well-known and studied T Tauri, the prototype star of an important class of variable stars, the T Tauri variables; its position is easily identified, about 3°20' WNW of ε Tauri, of magnitude 3.53 and which constitutes the northern vertex of the open Hyades cluster. Beginning in the 1930s, its brightness gradually increased, appearing as a clear arched halo on the western side of the illuminating star.

In 1958, another nebula associated with T Tauri, later catalogued as NGC 1554, was also observed by Otto Struve; however, within about ten years it disappeared completely. It could probably have been a transient nebula in the region that was illuminated by radiation from nearby stars: in particular, Struve refers to a fourteenth-magnitude star; this cloud, which is no longer observable, is therefore called the "Lost Struve Nebula". Modern celestial charts often tend to merge these two nebulae under the single designation NGC 1554/5. The T Tauri region and associated nebulae are located at a distance of about 576 light-years.