Astronomy   View all facts   Glossary   Help

physical object > natural object > celestial body > star > early star > O star

O star
subject			fact

O star	has lifetime 3 to 6 million years
	has color blue-white
	has surface temperature 35000 K
	has relative abundance rare
	has rotation velocity very high
	has absorption line He II
	has definition Very hot blue star, whose spectra is dominated by the lines of singly ionized helium (see Pickering series). (Most other lines are from at least doubly ionized elements, though H and He I lines are also present.) O stars are useful because they are found in dust clouds and virtually define the spiral arms.
	is a kind of early star
early star	has spectral type O, B, A, and early F
star	has star surface temperature
	has V magnitude
	has B magnitude
	has U magnitude
	has position on celestial sphere from the point of view of Earth
	has parallax from the point of view of Earth's orbit
	has proper motion
	has radiation at surface which is diffused out from the hotter core
	has energy source gravitational contraction and or fusion
	has energy production which takes place primarily within the core
	has surface density which depends on luminosity class
	has apparent magnitude
	has absolute magnitude
	has age
	has catalog star catalog
	has material hydrogen, helium
	has velocity determined from proper motion and radial velocity
	has mass greater than 0.08 the sun's mass
celestial body	has spectra
physical object	has location or center of gravity
	has angular momentum
	has momentum
	has temperature
	has volume
	has extent

Kinds of O star :

• AE Aurigae (6 facts) - Runaway star which diverges from a comparatively small area in Orion.
• Mintaka (5 facts) - One of the three stars in Orion's belt, and the star along whose line of sight interstellar gas was first spectroscopically detected.
• O((f)) (4 facts) - O-type stars in which N III is present in emission and He is strong in absorption.
• O(f) (4 facts) - O-type stars in which N III is present in emission and He II is weakly present in absorption or emission.
• Oe (4 facts) - O star with emissions in the Balmer lines.
• Oef (4 facts) - Early O stars that show double emission lines in He II λ4686.
• Of star (5 facts) - Peculiar O stars in which emission features at λλ4634-4641 from N III and 4686 from He II are present. They have a well-developed absorption spectrum, which implies that the excitation mechanism of the emission lines is selective, unlike that of Wolf-Rayet stars. The spectra of Of stars are usually variable, and the intensities of their emission lines vary in an irregular manner. Of stars belong to extreme Population I. All O stars earlier than 05 are Of.
• Plaskett's star (6 facts) (HD 47129) - A very massive O-type giant with known anomalies in its spectrum. It is a spectroscopic binary in which mass exchange is occurring. Its spectrum can be interpreted to mean that each component has a mass of 75 M_sun.
• sdO (3 facts) - Subdwarf O star showing few very broad and shallow Balmer lines and a very strong He II 4686 line.
• Theta2 Orionis (8 facts) (2U 0525-06) - A spectroscopic binary tentatively identified with 2U 0525-06.
• Zeta Ophiuchi (7 facts) - A reddened O star (a runaway star from the Sco-Cen association) with a high rotational velocity. It is well known for its strong interstellar absorption lines in the visible part of the spectrum.
• Zeta Pup (4 facts) - The brightest Of star known, embedded in the Gum Nebula. It has an envelope which is rapidly accelerating outward.
• Zeta Puppis (10 facts) (HR 3165)

Next early star: peculiar star    Up: early star    Previous early star: luminous blue variable