Chemistry in Space

A short lesson on spectroscopy methods used to identify the identity of chemicals and elements in stars, exoplanet atmospheres, and the interstellar medium.

Transcript

1. CHEMISTRY IN SPACE ASTRONOMICAL SPECTROSCOPY
2. • We assume that the laws of science are the same everywhere • We can learn about the chemistry of objects in space because the atoms that compose distant objects are the same as those we have on Earth • What properties can we measure at interstellar distances?
3. • Electrons only orbit atoms at specific energy levels and fill the available levels around an atom from lowest to highest energy • When they are excited (at a higher energy) or relax (to a lower energy) they “leap” between those levels and absorb or emit the difference in energy
4. • Because electrons can only move between specific energies, they can only absorb or emit specific colours • We can use this fact to determine what elements are compose materials in the lab or stars in distant galaxies = ′ ∙ ℎ = ℎ ∙ ℎ = ′ ∙ ℎ
5. • Fewer than 100 years ago, astronomers thought that the Sun was made of the same materials in the same proportions as the Earth • In her 1925 PhD thesis, Cecilia Payne- Gaposchkin used spectroscopy to show that the sun was mostly hydrogen and helium • She and her assistants went on to catalogue over 2 million stars
6. • Helium was discovered in the Sun before it was discovered on Earth! • It is named after Helios, the Greek god of the sun • Most of Earth’s atmospheric helium escapes into space, so we have to collect it from underground, distilled from natural gas
7. TARGET PROJECT – PART I
8. • When we know the spectrum of a distant star, we can use that as a light source to investigate materials between that star and Earth • Light from the star will be absorbed by elements as well as complex molecules • Water • Carbon Monoxide • Sugars • Metals and oxides
9. • Galaxies are mainly hydrogen and helium, so when we can tell if galaxies are moving towards or away from the Earth due to Doppler shift • Most of the galaxies observed are red shifted, so unless we are very special, the universe is expanding everywhere
10. • Spectroscopy is also used in the search for life • We can tell if a planet passes in front of its sun by the decrease in luminosity (brightness) • We can tell what’s on the planet because the light passes through the atmosphere • Certain gases may indicate the presence of life • Oxygen • Methane • Water
11. TARGET PROJECT – PART II
12. QUESTIONS? ASTRONOMICAL SPECTROSCOPY