Hydrogen line

High school (ages 12+)
Space & Astronomy

Name:

Date:

Step 1 · Read the article

Open the article and read it at the level above. Then answer the questions below in your own words.

https://smallwhale.org/articles/hydrogen-line

Write what each word means, using the article.

Do not copy the article. Write two things you learned, the way you would explain them to a friend.

Answers below are taken from the article’s stored facts, so they match what the student read.

1. What is the physical origin?Hyperfine transition in the ground state of neutral hydrogen
2. What is the frequency?1420.40575177 MHz
3. What is the 21-cm hydrogen line?It is a special radio signal that comes from hydrogen atoms when their tiny magnets flip, producing a wavelength of 21 centimeters that astronomers can detect.
4. Why do scientists call it a "secret signal"?Because it can travel through the dust that hides stars, letting us see hidden parts of our galaxy that normal light cannot reach.

Hyperfine Structure: Small energy differences in atomic spectra arising from the interaction between nuclear and electron magnetic moments.
Interferometry: A technique that combines signals from multiple telescopes to achieve higher resolution and sensitivity.
Cosmic Dawn: The period in the early universe when the first stars and galaxies began to emit light.
Epoch of Reionization: The era when the neutral hydrogen in the universe was reionized by ultraviolet radiation from early stars and galaxies.