An Etymological Dictionary of Astronomy and Astrophysics
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In atomic physics, an initial energy state in an emission transition.

→ upper; → level.

Of an integral operator, the point at which the integration ends.

→ upper; → limit.

A → main sequence star with a mass above 1.5 Msun. Upper main sequence stars have high central temperatures so that they produce their energy through the → CNO cycle. The outward energy flux is very high and therefore this flux cannot be maintained by → radiative transfer. Thus, upper main sequence stars have → convective cores. Outside the core, there is a → radiative zone. The mass of the convective core gradually diminishes as the hydrogen is consumed. The surface hydrogen is fully ionized and the → opacity is due to → electron scattering The opacity due to electron scattering.

→ upper; → main; → sequence.

The upper part of the Earth's → mantle which begins at the base of the → crust around 35 km and extends downward to about 410 km.

→ upper; → mantle.

Same as → upper mass limit.

→ upper; → mass; → cut-off.

The highest mass range admitted in a star formation model. The high mass end of the → initial mass function. The upper mass limit is a critical parameter in understanding → stellar populations, → star formation, and → massive star feedback in galaxies.

→ upper; → mass; → limit.

The movement of a celestial body across a celestial meridian's upper branch. Same as → upper culmination.

→ upper; → transit.

1) Toward or in the higher part of a stream; against the current. → downstream
2) Directed upstream; situated upstream.

→ up; → stream.

Farâz, → height; water, → water.

A → supernova remnant located in the southern Milky Way in the constellation → Vela. It has a large angular diameter of about 8° and lies 250 ± 30 pc away (Cha et al. 1999, ApJ 515, L25). Its overall emission is dominated by the interaction of the → supernova blast wave with the → interstellar medium. This SNR is also notable for a number of protrusions extending well beyond its rim, which were suggested to be fragments of ejecta from the supernova explosion. X-ray spectroscopy has since confirmed several of these protrusions to indeed be strongly enriched with ejecta. The age of the SNR is estimated to be ~11,000 years, based on the spin-down rate of the associated → Vela pulsar, but ages as large as 20,000-30,000 years have also been argued.

→ Vela; → supernova remnant.

The irregular supercluster that contains the Virgo cluster and the Local Group. At least 100 galaxy groups and clusters are located within its diameter of 110 million light-years. It is one of millions of superclusters in the observable Universe.

→ Virgo; → supercluster.

The explosive ejection of superheated matter from a → volcano.

→ volcanic; → eruption.

A group of people working together to achieve a stated goal.

→ work; → -ing; → group.

A supergiant star of type F and G whose effective temperature is between 4800 and 7500 K. Yellow supergiants are extremely rare, because they represent a very short-lived phase, typically a few tens of thousands of year, in the evolution of → massive stars.

→ yellow; → supergiant.

The removal of non-significant zeroes from a number. For example, replacing 531.2300 by 531.23.

→ zero; → suppression.