Our "Local Arm" Is Longer Than Thought.

Meanwhile, Poggio and her colleagues mapped more than 750,000 of the most massive main-sequence stars, 353 newborn star clusters, and 1,923 young Cepheid variables, giant pulsating stars with well-known distances. COLUMNS/DEPARTMENTS MILKY WAY WHILE ASTRONOMERS generally agree that the Milky Way has four major spiral arms, what they look like is still an open question. In the January Astronomy & Astrophysics, Xu and his colleagues picked out 9,750 stars of spectral type O to B2, massive and brilliant stars that are at most 20 million years old and thus not too far from their birthplaces in the spiral arms. [Extracted from the article]