When are spectra continuous? When are they discreet line spectra?

Source- http://instruct1.cit.cornell.edu/courses/astro101/lec09.htm

Incandescent, high temperature, solids emit continuous spectra since electrons can fall into neighboring atoms during de-excitation and emit all possible frequencies. Excited gases emit discreet spectra which can be used to identify one gas from another since electrons must remain within ONE ATOM when undergoing energy transitions in gases.

As the peak frequency, f_o, shifts to the right, from red to green to blue, the temperature of an incandescent solid increases. The left radiation curve would indicate a "red hot" object. The middle curve would represent a "white hot" object. And the last curve, would represent a "blue hot" object.  Therefore, a red hot flame is cooler than a blue flame which is why your chemistry teacher always told you to use the "blue" portion of the bunsen burner's flame to heat your test-tubes.  Red hot stars are cooler than yellow stars (our sun) which are cooler than blue stars.  There are no green stars since equal amounts of longer red wavelengths and shorter blue/violet wavelengths are also emitted, producing the color white, not green.

Source - physics/as102/homework/homework3/Hmk3solann.htm

Any solid, liquid and dense (thick) gas at a temperature above absolute zero will produce a thermal, aka continuous, spectrum. A thermal spectrum is the simplest type of spectrum because its shape depends on only the temperature. Relatively dense gases produce it where frequent collisions between atoms occur. When these collisions occur the electrons are jiggled causing electromagnetic waves. Photons are then emitted of a variety of energies. The sum of all of these emitted photons creates a continuous spectrum.