Teachers, scroll down for a short list of key resources in our Teachers’ Toolkit.
- EGS8p7 has been identified, at about 13.2 billion years old, as the oldest and most distant galaxy yet detected. What is a galaxy?
- Astrophysicists calculated EGS8p7’s distance by determining its redshift. What is redshift? Take a look at the scale above for a clue.
- Redshift, symbolized by the letter z, describes the phenomenon of electromagnetic radiation (light or heat) being stretched, increasing its wavelength to the “red” end of the electromagnetic spectrum. NASA’s Spitzer Space Telescope, which detects infrared radiation, was initially used to study EGS8p7.
- Cosmological redshift is a measurement of the expansion of the universe. The greater an object’s redshift, the further its distance. EGS8p7 has a redshift of 8.68. According to scientists, galaxies like EGS8p7 have moved more than “30 billion light years from Earth [or, what would become Earth] since [they were] born. We are actually looking back through 95% of all time to see this galaxy.”
- Why are light and redshifts from the oldest, most distant galaxies difficult to detect?
- The early universe was a hot, cloudy, soup—not very good at transmitting light.
- “Right after the Big Bang, the universe was basically a big mess of charged particles. Photons were scattered by free electrons and thus the early universe could not transmit light. Within 380,000 years after the Big Bang, the universe had cooled down enough for the free electrons and protons to combine,” creating crystal-clear neutral hydrogen. This period is nicknamed the Epoch of Reionization.
Nat Geo: Hubble Captures Colorful Universe
Caltech: Farthest Galaxy Detected
(extra credit) The Astrophysical Journal: Ly? Emission from a Luminous z=8.68 Galaxy: Implications for Galaxies as Tracers of Cosmic Reionization