For reasons that remain unclear, the mass of Procyon B is unusually low for a white dwarf star of its type. With a surface temperature of 7,740 K, it is also much cooler than Sirius B; this is a testament to its lesser mass and greater age. The mass of the progenitor star for Procyon B was about and it came to the end of its life some  billion years ago, after a main-sequence lifetime of  million years. Attempts to detect X-ray emission from Procyon with nonimaging, soft X-ray–sensitive detectors prior to 1975 failed. Extensive observations of Procyon were carried out with the Copernicus and TD-1A satellites in the late 1970s. The X-ray source associated with Procyon AB was observed on April 1, 1979, with the Einstein Observatory high-resolution imager (HRI). The HRI X-ray pointlike source location is ~4" south of Procyon A, on the edge of the 90% confidence error circle, indicating identification with Procyon A rather than Procyon B which was located about 5" north of Procyon A (about 9" from the X-ray source location). "α Canis Minoris" (Latinised to "Alpha Canis Minoris") is the star's Bayer designation. The name "Procyon" comes from the Ancient Greek (""), meaning "before the dog", since it precedes the "Dog Star" Sirius as it travels across the sky due to Earth's rotation. (Although Procyon has a greater right ascension, it also has a more northerly declination, which means it will rise above the horizon earlier than Sirius from most northerly latitudes.) In Greek mythology, Procyon is associated with Maera, a hound belonging to Erigone, daughter of Icarius of Athens. In 2016, the International Astronomical Union organized a Working Group on Star Names (WGSN) to catalog and standardize proper names for stars. The WGSN's first bulletin of July 2016 included a table of the first two batches of names approved by the WGSN; which included "Procyon" for the star α Canis Minoris A. The two dog stars are referred to in the most ancient literature and were venerated by the Babylonians and the Egyptians, In Babylonian mythology, Procyon was known as Nangar (the Carpenter), an aspect of Marduk, involved in constructing and organising the celestial sky.