A curve or surface that is tangential to every curve or surface in a family. For example, if a family of circles has radius a and centre at a distance b > a from a fixed point C, the envelope will be an annulus with the two circles having radii b+a and b − a.
An annulus as an envelope
A cloud of gas and dust surrounding a star or other astronomical object. Stellar envelopes are of many types. Hot young stars generate hot glowing envelopes, either by ionizing the surrounding gas or by ejecting hot material. Evolved stars shed their outer layers and generate cool circumstellar envelopes which are rich in dust and molecules. When the hot core of the old star is exposed, the envelope is ionized and may be detected as an emission nebula—as a planetary nebula, for example.
See ring conformations.
A smooth curved outline giving the shape of an oscillating signal whose amplitude varies over time. See also amplitude modulation.
Envelope
- framestone
- framework
- Framework Convention on Climatic Change
- framework grains
- framework(in mechanics)
- framework porosity
- Framework Programme
- Framework Programmes, I–VII
- framing
- France
- franc fort
- franchise
- Francia, José Gaspar Rodriguez de (1776–1840)
- Francis (1936–)
- Francisco
- Francis Ferdinand (1863–1914)
- Francis I (1494–1547)
- Francis Joseph (1830–1916)
- Francis of Assisi, St (1181–1226)
- Francis, Thomas Jr.
- francium
- Franck, James
- Franck–Condon principle
- Franco, Francisco (1892–1975)
- Franconian