Overview
This lecture discusses recent James Webb Space Telescope (JWST) discoveries of mysterious, distant cosmic objects, exploring the hypothesis that some may be "dark stars" powered by dark matter rather than nuclear fusion.
James Webb Discoveries & Observations
- JWST observed extremely redshifted, distant objects from when the universe was about 300 million years old or less.
- These objects are visible mainly in infrared, matching JWST’s specialty.
- They appear very compact and luminous, challenging standard explanations like proto-galaxies or star clusters.
The Dark Star Hypothesis
- Dark stars are theoretical objects powered by dark matter annihilation instead of fusion.
- Originally proposed in 1783, the concept now focuses on clouds of hydrogen and helium heated by dark matter.
- Dark stars could be enormous (up to 1,000 astronomical units wide and over 100 solar masses).
- These objects would emit extreme heat (surface temperatures ~10,000 K) and might become seeds for supermassive black holes.
Recent Evidence and Spectral Analysis
- Recent studies by Katherine Freese and others found some JWST objects (e.g., GSGS Z14-0 and Z14-1) match dark star predictions in brightness, mass, and morphology.
- Spectroscopy revealed a potential helium 2 absorption line at 640 angstroms, predicted by dark star models but not expected in normal galaxies or clusters.
- An oxygen line at 88 micrometers (from ALMA) poses a problem, as oxygen implies supernovae, not expected in pure dark stars.
Scientific Uncertainty & Next Steps
- Helium signal is exciting but requires confirmation with stronger, repeated observations.
- Oxygen presence could indicate more complex objects or unusual early galaxies.
- The nature of these objects remains hypothetical until further observational evidence is gathered.
Key Terms & Definitions
- Redshift — Stretching of light to longer wavelengths due to the universe’s expansion, indicating great distance and age.
- Dark Star — A theorized early-universe object powered by dark matter particle annihilation.
- Spectroscopy — Analysis of an object’s light to determine its composition and physical properties.
- Helium 2 Absorption Line — A spectral feature indicating the presence of ionized helium, potentially linked to dark stars.
- ALMA — Atacama Large Millimeter/submillimeter Array, a telescope observing different wavelengths from JWST.
Action Items / Next Steps
- Monitor for new JWST and ALMA observations on these distant objects.
- Review assigned readings on dark matter and cosmic evolution.
- Prepare to discuss alternative explanations for early-universe luminous objects in the next class.