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Chapter 24: Problem 47

Explain why the dark matter in galaxy clusters could not be neutral hydrogen.

Short Answer

Expert verified
Dark matter, which does not interact with electromagnetic forces, fundamentally differs from neutral hydrogen. In the high temperature environments of galaxy clusters, hydrogen is usually ionized while neutral hydrogen can absorb and emit radiation. These properties make it inconsistent with the characteristics of dark matter, making neutral hydrogen an unlikely constituent of dark matter.

Step by step solution

01

Understand Dark Matter

Begin by understanding dark matter. Dark matter is a form of matter thought to account for approximately 85% of the matter in the universe. It does not interact with the electromagnetic force, meaning it neither emits nor reflects light, making it extremely difficult to spot.
02

Understand Neutral Hydrogen

Next, familiarize oneself with neutral hydrogen. Hydrogen is usually in an ionized state in high temperature environments, such as those found within galaxy clusters. Neutral hydrogen can absorb and emit radiation, specifically at a wavelength of 21 cm, and hence can be detected through radio astronomy.
03

Compare Dark Matter and Neutral Hydrogen

Comparing dark matter and neutral hydrogen brings the realization that their characteristics differ significantly. The fact that neutral hydrogen emits radiation contradicts the fundamental properties of dark matter that it does not interact with electromagnetic forces at all. Therefore, it is improbable for the dark matter in galaxy clusters to be neutral hydrogen.

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Most popular questions from this chapter

Use the Stamy Night Enthusiast \({ }^{\mathrm{TM}}\) program to observe other galaxies. Select Favourites \(>\) Guides \(>\) Atlas to display the entire celestial sphere. Open the Options pane, expand the Deep Space list, and click the box for Messier Objects to display these objects. Open the Find pane and select each of the following galaxies in turn. Zoom in as necessary to see the shape of the galaxy to determine its Hubble classification as well as you can, and explain your reasoning: (i) Virgo A (M87); (ii) M105; (iii) \(\mathrm{M} 102\); (iv) M104; (v) M109.

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. What was the Shapley-Curtis "debate" all about? Was a winner declared at the end of the "debate"? Whose ideas turned out to be correct?
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