Astronomy Final Week 3 Flashcards

Questions and Answers

Which of the following types of galaxies are reddest in color? (Select all that apply)

Irregulars

Spirals

Ellipticals (correct)

Lenticulars

What is the Tully-Fisher relation?

The further away a galaxy is, the faster its recession velocity.

The longer the period of a galaxy's variable stars, the more luminous it is.

The faster a spiral galaxy's rotation speed, the more luminous it is. (correct)

The smaller a galaxy appears, the further away it is.

The redder a galaxy's color, the further away it is.

Which of the following statements about types of galaxies is not true?

Large elliptical galaxies are more common in clusters of galaxies than they are outside of clusters.

Spiral galaxies have younger stars than elliptical galaxies.

Elliptical galaxies are bluer and contain more dust than spiral galaxies. (correct)

Among the large galaxies in the universe outside of clusters, most are spiral.

The most basic difference between elliptical galaxies and spiral galaxies is that ________.

elliptical galaxies lack anything resembling the disk of a spiral galaxy Signup and view all the answers

Hubble's galaxy classification diagram (the 'tuning fork') ________.

Relates galaxies according to their shapes, but not according to any evolutionary status. Signup and view all the answers

Suppose we observe a Cepheid variable in a distant galaxy. The Cepheid brightens and dims with a regular period of about 10 days. What can we learn from this observation?

We can learn the distance to the galaxy. Signup and view all the answers

In 1924, Edwin Hubble proved that the Andromeda Galaxy lay far beyond the bounds of the Milky Way. How was he able to prove this?

He proved this by observing individual Cepheid variable stars in Andromeda and applying the period-luminosity relation. Signup and view all the answers

Suppose that Hubble's constant were 20 kilometers per second per million light-years. How fast would we expect a galaxy 100 million light-years away to be moving?

Away from us at 2,000 km/s Signup and view all the answers

Why are white dwarf supernovae more useful than massive star supernovae for measuring cosmic distances?

White dwarf supernovae all have roughly the same true peak luminosity, while massive supernovae come in a wide range of peak luminosities. Signup and view all the answers

Suppose an elliptical galaxy is so far away that we cannot see even its brightest stars individually. Which of the following techniques might allow us to measure its distance?

We could use a white dwarf supernova as a standard candle. Signup and view all the answers

What is the best way to determine a galaxy's redshift?

Take a spectrum of the galaxy, and measure the difference in wavelength of spectral lines from the wavelengths of those same lines as measured in the laboratory. Signup and view all the answers

Study Notes

Galaxy Types

Elliptical galaxies appear reddest in color compared to spirals, lenticulars, and irregulars.
Spiral galaxies contain younger stars, whereas elliptical galaxies have older star populations.

Tully-Fisher Relation

The Tully-Fisher relation indicates that faster rotation speeds in spiral galaxies correlate with higher luminosity.

Misconceptions about Galaxies

Elliptical galaxies do not contain more dust than spiral galaxies; they are generally bluer and richer in dust.

Distinction Between Galaxy Types

The most basic distinction is that elliptical galaxies lack a disk structure, which is present in spiral galaxies.

Hubble's Galaxy Classification

Hubble's galaxy classification diagram (the "tuning fork") categorizes galaxies based on shape without implying evolutionary relationships.

Cepheid Variables

Observing a Cepheid variable's brightness changes can help determine the distance to its host galaxy.

Hubble's Discovery

Edwin Hubble confirmed Andromeda's distance using the period-luminosity relationship of individual Cepheid variable stars.

Hubble's Law

If Hubble's constant is 20 km/s per million light-years, a galaxy 100 million light-years away would be moving away at 2,000 km/s.

Supernovae Significance

White dwarf supernovae are more reliable for measuring distances due to their consistent peak luminosity compared to massive star supernovae.

Measuring Distances to Galaxies

For distant elliptical galaxies, using white dwarf supernovae as standard candles is effective when direct observation of stars is not possible.

Determining Redshift

The best method to determine a galaxy's redshift is through spectral analysis, measuring the shift of spectral lines from laboratory wavelengths.

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Description

Test your knowledge of key concepts in astronomy with these flashcards for Week 3. This quiz covers important topics such as types of galaxies and the Tully-Fisher relation. Perfect for final exam preparation.