What two distinct physical phenomena can cause a galaxy to appear red?
Answer
Intrinsically old stellar population or extreme redshift due to distance
A galaxy can exhibit a red appearance due to two completely separate physical origins, creating an ambiguity that astronomers must resolve. The first cause is intrinsic: the galaxy has aged past its vigorous star-forming period and is now dominated by older, cooler stars, like red giants, which inherently emit longer, redder wavelengths. The second cause is entirely related to cosmology and distance: the galaxy might actually be young and blue, but because it is incredibly far away, the expansion of space has stretched its light significantly through redshift, pushing its observed color toward the red end of the spectrum, regardless of its current stellar content.
Related Questions
What stellar population primarily dictates a galaxy's vibrant blue appearance?What physical process stretches light waves leading to the phenomenon of redshift for distant galaxies?What two distinct physical phenomena can cause a galaxy to appear red?If a galaxy has a measured redshift value of z=3, by what factor has its light wavelength been stretched?What foundational relationship did Edwin Hubble establish concerning galaxies based on redshift measurements?What chiefly dictates the intrinsic color of a galaxy, separate from distance effects?Which celestial object is explicitly mentioned as exhibiting a blueshift due to approaching the observer?Why are powerful infrared instruments like those on the James Webb Space Telescope essential for observing the very first galaxies?How did the light forming the Cosmic Microwave Background (CMB) achieve its current microwave frequency?When astronomers analyze a galaxy spectrum, how is the known wavelength of spectral lines like hydrogen used to calculate distance?