Log out Go to App
Go to App

Learning Materials

Features

Discover

Chapter 23: Problem 10

How do astronomers determine the distances to H I (neutral hydrogen) clouds?

Short Answer

Expert verified
Astronomers determine the distances to H I (neutral hydrogen) clouds by observing the redshift of the 21 cm emission line specific to these clouds and using the estimated velocity with Hubble's Law to calculate the distance.

Step by step solution

01

Understand the basics of measuring astronomical distances

Astronomy utilizes several methods to determine distances in space. Some of these methods include parallax measurements, Cepheid variables, and supernovae. For distant objects like galaxies and gas clouds, astronomers often rely on redshift.
02

Understand the role of emission lines

The light from celestial objects often present emission lines. These are lines in a spectrum caused by emission of light at particular wavelengths, corresponding to different elements. Astronomers can observe these emission lines and measure their shifts due to motion of the celestial objects.
03

Understand the significance of the 21 cm spectral line

The 21 cm line is a specific emission line associated with H I (neutral hydrogen) clouds. The energy absorbed or emitted at this wavelength is due to a change in the spin state of the hydrogen atom's electron. By observing shifts in this 21 cm line, astronomers can determine the velocity of the H I cloud.
04

Determine the distance using redshift

The velocity of the H I cloud determined from the redshift of the 21 cm line can be used to estimate its distance from us. In an expanding universe, the velocity of an object is related to its distance from the observer. This relation is described by Hubble's Law. Using this law, astronomers can estimate the distance to H I clouds.

Unlock Step-by-Step Solutions & Ace Your Exams!

  • Full Textbook Solutions

    Get detailed explanations and key concepts

  • Unlimited Al creation

    Al flashcards, explanations, exams and more...

  • Ads-free access

    To over 500 millions flashcards

  • Money-back guarantee

    We refund you if you fail your exam.

Start your free trial

Over 30 million students worldwide already upgrade their learning with Vaia!

One App. One Place for Learning.

All the tools & learning materials you need for study success - in one app.

Get started for free

Most popular questions from this chapter

What is the evidence that there is a supermassive black hole at the center of our Galaxy? How is it possible to determine the mass of this black hole?

In our Galaxy, why are stars of spectral classes \(\mathrm{O}\) and \(\mathrm{B}\) only found in or near the spiral arms? Is the same true for stars of other spectral classes? Explain why or why not.

In what way are the orbits of stars in the galactic disk different from the orbits of planets in our solar system? What does this difference imply about the way that matter is distributed in the Galaxy?

What is the difference between dark matter and dark nebulae?

Calculate the energy of the photon emitted when a hydrogen atom undergoes a spin-flip transition. How many such photons would it take to equal the energy of a single \(\mathrm{H}_{\alpha}\) photon of wavelength \(656.3 \mathrm{~nm}\) ?
See all solutions

Recommended explanations on Physics Textbooks

Medical Physics

Read Explanation

Thermodynamics

Read Explanation

Engineering Physics

Read Explanation

Physical Quantities And Units

Read Explanation

Translational Dynamics

Read Explanation

Electromagnetism

Read Explanation
View all explanations

What do you think about this solution?

We value your feedback to improve our textbook solutions.

Study anywhere. Anytime. Across all devices.

Sign-up for free