Classical Cepheid variables are higher mass population I stars. RR Lyrae variables are much more common than Cepheids, but also much less luminous. The average absolute magnitude of an RR Lyrae star is about +0.75, only 40 or 50 times brighter than our Sun.
- What is the major difference between Cepheids and RR Lyrae?
- Are Cepheid stars High mass?
- What is the most important important difference between Cepheids and RR Lyrae variable stars?
- What is the difference between classical Cepheids and Type II Cepheids and why does this difference exist in the universe today?
- What type of star is RR Lyrae?
- Why do more massive stars pulsate more slowly than smaller ones?
- What kind of star is an RR Lyrae variable star?
- What are RR Lyrae stars and how do they help astronomers?
- What are RR Lyrae and Cepheid variable stars and why are they important to understanding the universe?
What is the major difference between Cepheids and RR Lyrae?
Cepheid variables are a vital tool for measuring the distances of relatively nearby galaxies (out to about 40 million parsecs, or 130 million light years). RR Lyrae stars can also be used to measure distances, but since they are less luminous, they can only be seen to smaller distances.
Are Cepheid stars High mass?
Type II Cepheids (also termed Population II Cepheids) are population II variable stars which pulsate with periods typically between 1 and 50 days. Type II Cepheids are typically metal-poor, old (~10 Gyr), low mass objects (~half the mass of the Sun).
What is the most important important difference between Cepheids and RR Lyrae variable stars?
Cepheids are higher luminosity stars than RR Lyrae variables, and have longer periods. Cepheids are higher luminosity stars than RR Lyrae variables, and have longer periods. Compared to the Milky Way, how many stars are contained in the most massive galaxies?
What is the difference between classical Cepheids and Type II Cepheids and why does this difference exist in the universe today?
Classical Cepheids are used to determine distances to galaxies within the Local Group and beyond, and are a means by which the Hubble Constant can be established (see below). Type II Cepheids are Population II (metal-poor) variable stars which pulsate with periods of typically between 1 and 50 days.
What type of star is RR Lyrae?
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. They lie in the instability strip of the Hertzsprung-Russell diagram and suffer instabilities that cause their size to periodically change.
Why do more massive stars pulsate more slowly than smaller ones?
In the case of pulsating variables this is due to the periodic expansion and contraction of the surface layers of the stars. This means the star actually increases and decreases in size periodically.
What kind of star is an RR Lyrae variable star?
horizontal branch 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. They lie in the instability strip of the Hertzsprung-Russell diagram and suffer instabilities that cause their size to periodically change.
What are RR Lyrae stars and how do they help astronomers?
RR Lyrae variables are periodic variable stars, commonly found in globular clusters. They are used as standard candles to measure (extra) galactic distances, assisting with the cosmic distance ladder.
What are RR Lyrae and Cepheid variable stars and why are they important to understanding the universe?
Key concepts and summary Light curves of these stars show that their luminosities vary with a regularly repeating period. RR Lyrae stars can be used as standard bulbs, and cepheid variables obey a period-luminosity relation, so measuring their periods can tell us their luminosities.