The continuous spectrum of the visible photosphere of the Sun is attributable to the radiative equilibrium of the $\mathrm{H}^{-}$ ion. This has been recognised for at least 80 years (Wildt 1939). Show This ion forms by the attachment of a free electron (with a continuous spectrum of energies) to a hydrogen atom, emitting a continuous spectrum of photons in the process. The reverse process, photodetachment, occurs at the same rate and is the principal source of continuum opacity in the solar photosphere. Absorption/emission by H$^{-}$ ions demands that the temperature is low enough not to dissociate the extra electron ($<10^{4}$K), but high enough that there is a supply of free electrons donated by the ionisation of alkali metals ($>3000$K). Superimposed on this continuum are dark, discrete absorption features caused by transitions within atomic species (mainly metals, but also H). These are dark because the photons at these frequencies arrive here from higher up in the atmosphere at cooler temperatures. The original question asks only about "sunlight", and the H$^{-}$ opacity is only effective between about 3,000-10,000K. Stars with hotter or colder photospheres are dominated by different opacity and hence emission mechanisms. In hotter stars the primary sources of continuous opacity at visible wavelengths, at temperatures exceeding 10,000K, are scattering by free electrons and the Paschen continuum arising from transitions between the $n=3$ state in hydrogen atoms and ionised hydrogen. There are also smaller contributions from free-free transitions of electrons in the electric fields of ions (bremsstrahlung). There can of course be a cooler, overlying layer in hot stars where H$^{-}$ can form, but it has a lower density and a small optical depth (i.e. photons travel through it) and it therefore does not contribute significantly to the photospheric continuum. In very cool photospheres, there are no free electrons and the atoms begin to form molecules like carbon monoxide, water, molecular hydrogen, titanium oxide, vanadium oxide etc There is actually very little true continuum absorption/emission in the visible part of the spectrum of these stars. Instead there is an overlapping mess of rotational/vibrational molecular transitions that form a pseudo-continuum when observed by instruments with finite spectral resolution. The dominant opacity in the visible spectrum at just below 3000K is due to TiO molecules. At even lower temperatures (below 2500K, and approaching the substellar regime), absorption and emission by dust becomes important, although there is negligible flux at visible wavelengths. M33: Triangulum Galaxy The small, northern constellation Triangulum harbors this magnificent face-on spiral galaxy, M33. Its popular names include the Pinwheel Galaxy or just the Triangulum Galaxy. M33 is over 50,000 light-years in diameter, third largest in the Local Group of galaxies after the Andromeda Galaxy (M31), and our own Milky Way. About 3 million light-years from the Milky Way, M33 is itself thought to be a satellite of the Andromeda Galaxy and astronomers in these two galaxies would likely have spectacular views of each other's grand spiral star systems. As for the view from planet Earth, this sharp composite image, a 25 panel mosaic, nicely shows off M33's blue star clusters and pinkish star forming regions that trace the galaxy's loosely wound spiral arms. In fact, the cavernous NGC 604 is the brightest star forming region, seen here at about the 1 o'clock position from the galaxy center. Like M31, M33's population of well-measured variable stars have helped make this nearby spiral a cosmic yardstick for establishing the distance scale of the Universe. M33: Triangulum Galaxy The small, northern constellation Triangulum harbors this magnificent face-on spiral galaxy, M33. Its popular names include the Pinwheel Galaxy or just the Triangulum Galaxy. M33 is over 50,000 light-years in diameter, third largest in the Local Group of galaxies after the Andromeda Galaxy (M31), and our own Milky Way. About 3 million light-years from the Milky Way, M33 is itself thought to be a satellite of the Andromeda Galaxy and astronomers in these two galaxies would likely have spectacular views of each other's grand spiral star systems. As for the view from planet Earth, this sharp composite image, a 25 panel mosaic, nicely shows off M33's blue star clusters and pinkish star forming regions that trace the galaxy's loosely wound spiral arms. In fact, the cavernous NGC 604 is the brightest star forming region, seen here at about the 1 o'clock position from the galaxy center. Like M31, M33's population of well-measured variable stars have helped make this nearby spiral a cosmic yardstick for establishing the distance scale of the Universe. What is the spectrum of the Sun?The spectrum starts with red light, with a wavelength of 700 nanometers (7,000 angstroms), at the top. It spans the range of visible light colors, including orange and yellow and green, and ends at the bottom with blue and violet colors with a wavelength of 400 nm (4,000 angstroms).
How does the Sun produce a continuous spectrum?The continuous (as distinct from the line) spectrum of the Sun is produced primarily by the photodissociation of negatively charged hydrogen ions (H−)—i.e., atoms of hydrogen to which an extra electron is loosely attached.
What is an example of a continuous spectrum?Continuous Spectrum. A rainbow is an example of a continuous spectrum. Here, the colors displayed are within the visible spectrum (between 380-760 nm). Light in this wavelength range is visible to the naked eye.
What light spectrum is continuous?Continuous Spectrum: A continuous spectrum contains all wavelengths of light in a certain range. Hot, dense light sources like stars, for example, emit a nearly continuous spectrum of light, which travels out in all directions and interacts with other materials in space.
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Is the Sun a continuous spectrum
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