### Dark Matter and Dark Energy

**Dark Matter**:
1. **WIMPs (Weakly Interacting Massive Particles)**: Hypothetical particles interacting via weak nuclear force and gravity. Evidence includes gravitational effects unexplained by visible matter.
2. **Axions**: Extremely light particles potentially solving quantum chromodynamics issues. Indirect evidence from astrophysical observations.
3. **Sterile Neutrinos**: Hypothetical non-weak-interacting neutrinos, supported by some cosmological observations.

**Dark Energy**:
1. **Cosmological Constant (Λ)**: Constant energy density explaining the universe’s accelerating expansion, evidenced by Type Ia supernovae.
2. **Quintessence**: Dynamic field varying over time, with potential but lacking strong observational support.

### Promising Exoplanets and Their Characteristics

**Key Characteristics**:
1. **Size and Mass**: Earth-sized or super-Earths.
2. **Composition**: Rocky planets.
3. **Atmosphere**: Capable of supporting liquid water.
4. **Distance from Star**: Within the habitable zone.
5. **Stellar Type**: Stable, long-lived stars (G-type, K-type).

**Significant Discoveries**:
1. **Proxima Centauri b**: In Proxima Centauri’s habitable zone.
2. **TRAPPIST-1 System**: Seven Earth-sized planets, three in the habitable zone.
3. **Kepler-452b**: In the habitable zone of a Sun-like star.
4. **LHS 1140 b**: Super-Earth with a stable orbit in the habitable zone.

### Detection Methods

1. **Transit Method**: Observes star dimming during planet transit.
2. **Radial Velocity Method**: Measures star’s wobble due to orbiting planets.
3. **Direct Imaging**: Captures images of exoplanets.
4. **Spectroscopy**: Analyzes light for atmospheric composition.

### Future Missions

**James Webb Space Telescope** and **European Extremely Large Telescope** will enhance atmospheric studies and habitable planet identification.