The longer the variability period, the more luminous the Cepheid. Through observations of Cepheid variables, astronomers have
determined the distances to other galaxies
. They compare the Cepheid variable’s apparent brightness with its intrinsic brightness.
What is the relationship between period and luminosity of a Cepheid variable star?
(3) The greater the luminosity of a Cepheid star, the longer its period of oscillation. It was discovered empirically in 1912, by the Harvard astronomer Henrietta Leavitt, that
a Cepheid’s period of pulsation
is linked to its luminosity.
What is the relationship between period and luminosity?
More luminous Cepheids are cooler and larger and have longer periods. Along with the temperature changes their radii also
change
during each pulsation (e.g. by ~25% for the longer-period l Car), resulting in brightness variations up to two magnitudes. The brightness changes are more pronounced at shorter wavelengths.
What is the period-luminosity relationship What is the period-luminosity relationship it is a relationship between a galaxies rate of rotation and its size it is the relationship between a Cepheid variable stars period of brightening dimming and its average luminosity the higher the luminosity The longer the period of brightening and dimming it is the relationship between?
It is a relationship between a galaxies rate of rotation and its size. It is the relationship between a Cepheid Variable star’s period of brightening/dimming and its average luminosity. The higher the luminosity, the shorter the period of brightening and dimming.
Why is the period-luminosity relationship important?
Because the luminosity of Cepheids can be easily found from the pulsation period,
they are very useful in finding distances to the star clusters or galaxies in which they reside
. … Edwin Hubble measured the distance to the Andromeda Galaxy in 1923 using the period-luminosity relation for Type II Cepheids.
How do you find the period of a luminosity relationship?
M
v
= – [2.76 (log
10
(P) – 1.0)] – 4.16
, where P is in days. If logarithms are a faint memory, you may wish to peruse a refresher on logs. For each Cepheid you discovered, use the above equation to determine the absolute magnitude of the Cepheid from its period.
Why is the period-luminosity relationship important quizlet?
Who discovered the period-luminosity relationship, and why was it so critical? Henrietta Swan Leavitt discovered the period-luminosity relationship. This relationship is critical
because it tells us the longer the pulsation period, the more luminous the star.
What is the period of a Cepheid variable?
A Cepheid variable star has a period of
3.7 days
, and from this we know its absolute magnitude is -3.1.
What is the difference between Type 1 and Type 2 Cepheids?
There are actually two classes of Cepheid: Type I Cepheids (δ Cepheus is a classical Cepheid) are population I stars with high metallicities, and
pulsation periods generally less than 10 days
. Type II Cepheids (W Virginis stars), are low-metallicity, population II stars with pulsation periods between 10 and 100 days.
What is the period-luminosity relationship quizlet?
The period-luminosity relationship discovered by Henrietta Leavitt for Cepheid variable stars, relating variability to over-all brightness says that. the
shorter the period
, the lower the luminosity of the star. The event that settled the debate between Curtis and Shapley about the ‘spiral nebulae’ was.
Why do galactic disks appear blue?
The disks appear bluer
because they are the site of ongoing star formation
. Massive stars are very bright and very hot, which gives their light a blue color, but they also have very short lifetimes by stellar standards. … Only the smaller, cooler stars remain giving these galaxies a red color.
Why do Cepheids pulsate?
Pulsating variable stars are intrinsic variables as their variation in brightness is due to a physical change within the star. In the case of pulsating variables this is due to
the periodic expansion and contraction of the surface layers of the stars
.
Why do RR Lyrae stars pulsate?
RR Lyrae stars pulse in a manner similar to Cepheid variables, but the nature and histories of these stars is thought to be rather different. Like all variables on the Cepheid instability strip, pulsations are
caused by the κ-mechanism, when the opacity of ionised helium varies with its temperature
.
Where are we at in our galaxy?
We’re about 26,000 light-years from the center of the galaxy,
on the inner edge of the Orion-Cygnus Arm
. It’s sandwiched by two primary spiral arms, the Sagittarius and Perseus Arms. The artists’ concepts above and below show the Orion-Cygnus Arm, the home spiral arm of our sun in the Milky Way galaxy.
Who invented Parallax?
The quantity is very small and never reaches 1/206,265 in radians, or 1′′ in sexagesimal measure. Stellar parallax. Encyclopædia Britannica, Inc. Using a heliometer designed by German physicist Joseph von Fraunhofer,
German astronomer Friedrich Wilhelm Bessel
was the first to measure stellar parallax in 1838.
What are the typical periods of RR Lyrae stars?
RR Lyrae are variable, horizontal branch stars with periods ranging from
a few hours to 2 days
, and optical brightnesses that typically vary between 0.3 and 2 magnitudes.
