- The hydrogen line, discovered in 1951, revolutionised radio astronomy. It is used for studying distant stars and searching for extraterrestrial intelligence.
- The hydrogen atom is composed of one proton and one electron. Both particles have a property called spin, which can be up or down.
- Spins can be aligned (up or down) or anti-aligned (opposite directions).
- Energy States and Emissions:
- The atom sheds excess energy when the electron flips its spin, emitting electromagnetic radiation with a wavelength of 21 cm.
- This emission appears as a characteristic line in detectors, known as the hydrogen line.
- Significance in Astronomy:
- Enabled the detection of cold, neutral hydrogen atomic gas clouds in interstellar space.
- Allowed the creation of the first map of the Milky Way galaxy, revealing its spiral arms.
- It holds the potential for sending information across space that an alien civilization might detect.
- The Rosette Nebula, a large hydrogen, sulphur, and oxygen gas cloud in the constellation of Monoceros, is 5,200 light years away from Earth and can be studied using this emission.
Dig Deeper: What is SETI (Search for Extraterrestrial Intelligence)?
