Table of Contents
- 1 What is the difference between classical Cepheids and Type II Cepheids and why does this difference exist in the universe today?
- 2 What is the difference between Type 1 and Type 2 Cepheids?
- 3 What are RR Lyrae and Cepheid variable stars and why are they important to understanding the universe?
- 4 What makes a Cepheid variable a variable star?
- 5 Can a Cepheid variable pulsate in more than one mode?
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 is the most important important difference between Cepheids and RR Lyrae variable stars?
RR Lyrae variables pulsate irregularly as compared to Cepheids which are very regular. Cepheids vary because they pulsate; RR Lyrae variables vary because they are binaries. Cepheids are higher luminosity stars than RR Lyrae variables, and have longer periods.
Are Cepheids brighter than supernova?
Supernovae are much much brighter than Cepheids, allowing us to observe them to even greater distances.
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.
Where are Cepheids plotted?
Cepheids occupy an elon- gated horizontal instability strip on the H-R diagram as massive stars transition from the main sequence to the giant and supergiant branches. RR Lyrae variables are older pulsating white giants with low metallicity.
What is the main difference between RR Lyrae variables and Cepheid variables?
RR Lyrae variables thus have shorter periods and lower luminosities than Cepheid variables. The variation in the luminosity of RR Lyrae and Cepheid stars results from the fact that they pulsate in and out. The radius of a Cepheid can vary by as much as 10 or 20 percent.
What are RR Lyrae and Cepheid variable stars and why are they important to understanding the universe?
Cepheids and RR Lyrae stars are two types of pulsating variable stars. 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.
How many types of Cepheids are there?
What are examples of variable stars?
The Cepheids and RR Lyrae stars are typical examples of such variables. The explosive (or eruptive) variables include novas, supernovas, and similar stars that undergo sudden outbursts of radiant energy, which results in rapid brightening.
What makes a Cepheid variable a variable star?
Variable stars are essentially stars that experience fluctuations in their brightness (aka. absolute luminosity). Cepheids Variables are special type of variable star in that they are hot and massive – five to twenty times as much mass as our Sun – and are known for their tendency to pulsate radially and vary in both diameter and temperature.
How is the period of a Cepheid determined?
Leavitt was able to measure the period of each star by measuring the timing of its ups and downs in brightness. What she determined was that the brighter the Cepheid, the longer its period. In fact, Cepheids are very special variable stars because their period (the time they take to brighten, dim and brighten again) is.
What are the Cepheid variables in the Magellanic Cloud?
Cepheids Cepheids, also called Cepheid Variables, are stars which brigthen and dim periodically. This behavior allows them to be used as cosmic yardsticks out to distances of a few tens of millions of light-years. In 1912, Henrietta Swan Leavitt noted that 25 stars, called Cepheid stars, in the Magellanic cloud would brighten and dim periodically.
Can a Cepheid variable pulsate in more than one mode?
A small proportion of Cepheid variables have been observed to pulsate in two modes at the same time, usually the fundamental and first overtone, occasionally the second overtone. A very small number pulsate in three modes, or an unusual combination of modes including higher overtones.