How Do We Know That Galaxy Clusters Contain a Lot

question 89

Multiple Choice

How do we know that galaxy clusters contain a lot of mass in the form of hot gas that fills spaces between individual galaxies?

• A)We infer its existence by observing its gravitational effects on the galaxy motions.
• B)The hot gas shows up as bright pink in visible-light photos of galaxy clusters.
• C)We can observe the frictional effects of the hot gas in slowing the speeds of galaxies in the clusters.
• D)We detect this gas with X-ray telescopes.

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Definitions:

Standard Error of Mean

The estimation of the standard deviation of the sample mean, reflecting the variability of the sample mean from the population mean.

Two-Tailed

Pertaining to tests of statistical significance that consider both directions of deviation from a null hypothesis.

Null Hypothesis

A statistical hypothesis that proposes there is no significant difference or effect and that any observed variation is due to chance.

Critical Value

A threshold value in hypothesis testing that separates the region where the null hypothesis is rejected from the region where it is not.