An O-type star is a hot, blue-white star of spectral type O in the Yerkes classification system employed by astronomers. They have temperatures in excess of 30,000 kelvins (K). Stars of this type have strong absorption lines of ionised helium, strong lines of other ionised elements, and hydrogen and neutral helium lines weaker than spectral type B.
The Trifid Nebula (M20) is sculpted and lit by the luminous O7.5III star visible at its centre in this infrared image.
The central star of NGC 6826 is a low-mass O6 star.
Alnitak is a triple star system with an O9.7 supergiant and an O9 giant as well as a B0 giant. These stars illuminate the nearby Flame Nebula.
The brightest star in the Trapezium cluster is O7V star θ 1 Orionis C. The other three are B0.5 and B1 main-sequence stars.
Star formation is the process by which dense regions within molecular clouds in interstellar space, sometimes referred to as "stellar nurseries" or "star-forming regions", collapse and form stars. As a branch of astronomy, star formation includes the study of the interstellar medium (ISM) and giant molecular clouds (GMC) as precursors to the star formation process, and the study of protostars and young stellar objects as its immediate products. It is closely related to planet formation, another branch of astronomy. Star formation theory, as well as accounting for the formation of a single star, must also account for the statistics of binary stars and the initial mass function. Most stars do not form in isolation but as part of a group of stars referred as star clusters or stellar associations.
The W51 nebula in Aquila - one of the largest star factories in the Milky Way (August 25, 2020)
Hubble Space Telescope image known as Pillars of Creation, where stars are forming in the Eagle Nebula
Assembly of galaxy in early Universe.
ALMA observations of the Orion Nebula complex provide insights into explosions at star birth.