How do astronomers measure the distance to RR Lyrae stars?

RR Lyrae stars make it easy to determine the distance to another galaxy. Just measure the average apparent magnitude of the variables, and compare the known absolute magnitude. A typical RR Lyrae has a luminosity perhaps 50 times greater than the Sun.

Read more

What important measurement did RR Lyrae variables allow astronomers to get?

RR Lyrae's brightness (between 7th and 8th magnitude) made it bright enough to observe spectroscopically in such a way that the changes in its spectrum could be traced throughout its cycle of variability. This enabled astronomers to measure changes in spectral type, as well as to detect the presence of emission lines. What are stars called that vary noticeably in brightness? A variable star is, quite simply, a star that changes brightness. A star is considered variable if its apparent magnitude (brightness) is altered in any way from our perspective on Earth.

Moreover, what does rr mean in rr lyrae?

any of the very regular, short-period, pulsating variable stars having periods between 1.5 and 29 hours. Word origin. RR, astronomical code designation of tenth variable + Lyrae, gen. And another question, how do astronomers find variable stars? Amateur astronomers can do useful scientific study of variable stars by visually comparing the star with other stars within the same telescopic field of view of which the magnitudes are known and constant. By estimating the variable's magnitude and noting the time of observation a visual lightcurve can be constructed.

Moreover, why are variable stars important to astronomers?

Research on variable stars is important because it provides information about stellar properties, such as mass, radius, luminosity, temperature, internal and external structure, composition, and evolution. Variable stars need to be systematically observed over decades in order to determine their long-time behavior. Accordingly, why are rr lyrae stars useful distance indicators? RR Lyrae star, any of a group of old giant stars of the class called pulsating variables (see variable star) that pulsate with periods of about 0.2?1 day. The intrinsic luminosities of RR Lyrae stars are relatively well-determined, which makes them useful as distance indicators.

There are two basic types of variable stars: intrinsic variables, whose luminosity actually changes, and extrinsic variables, whose apparent changes in brightness are due to changes in the amount of their light that can reach Earth. A star could be an intrinsic variable because it periodically swells and shrinks.