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Lecture

The Cosmic Distance Ladder

In course

PHYS-643: Astrophysics VI : The variable Universe

Introduction to time-variable astrophysical objects and processes, from Space Weather to stars, black holes, and galaxies. Introduction to time-series analysis, instrumentation targeting variability, and the importance of the time domain for astronomy, cos ...

Description

This lecture covers the fundamental problem of distance in astronomy, explaining the importance of distance measurements for interpreting observations. It discusses methods like wide-angle astrometry, direct distance measurement, and detached eclipsing binary distances. The presentation also delves into topics such as the Leavitt Law, the Tip of the Red Giant Branch, and the Hubble tension, providing insights into cosmological parameters derived from the Planck Cosmic Microwave Background data.

Instructor

Richard Irving Anderson

Official source

Ontological neighbourhood

Astronomy

Astrophysics: Physical cosmology, Stellar astronomy

Related concepts (32)

Hubble's law

Hubble's law, also known as the Hubble–Lemaître law, is the observation in physical cosmology that galaxies are moving away from Earth at speeds proportional to their distance. In other words, the farther they are, the faster they are moving away from Earth. The velocity of the galaxies has been determined by their redshift, a shift of the light they emit toward the red end of the visible spectrum. Hubble's law is considered the first observational basis for the expansion of the universe, and today it serves as one of the pieces of evidence most often cited in support of the Big Bang model.

Cosmic distance ladder

The cosmic distance ladder (also known as the extragalactic distance scale) is the succession of methods by which astronomers determine the distances to celestial objects. A direct distance measurement of an astronomical object is possible only for those objects that are "close enough" (within about a thousand parsecs) to Earth. The techniques for determining distances to more distant objects are all based on various measured correlations between methods that work at close distances and methods that work at larger distances.

Lambda-CDM model

The ΛCDM (Lambda cold dark matter) or Lambda-CDM model is a parameterization of the Big Bang cosmological model in which the universe contains three major components: first, a cosmological constant denoted by Lambda (Greek Λ) associated with dark energy; second, the postulated cold dark matter (abbreviated CDM); and third, ordinary matter.

Distance measure

Distance measures are used in physical cosmology to give a natural notion of the distance between two objects or events in the universe. They are often used to tie some observable quantity (such as the luminosity of a distant quasar, the redshift of a distant galaxy, or the angular size of the acoustic peaks in the cosmic microwave background (CMB) power spectrum) to another quantity that is not directly observable, but is more convenient for calculations (such as the comoving coordinates of the quasar, galaxy, etc.

Physical cosmology

Physical cosmology is a branch of cosmology concerned with the study of cosmological models. A cosmological model, or simply cosmology, provides a description of the largest-scale structures and dynamics of the universe and allows study of fundamental questions about its origin, structure, evolution, and ultimate fate. Cosmology as a science originated with the Copernican principle, which implies that celestial bodies obey identical physical laws to those on Earth, and Newtonian mechanics, which first allowed those physical laws to be understood.

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