Date: February 3, 2024
Venue: EnTC Commons, Vishwakarma Institute of Technology (VIT), Pune
Organizer: Antariksh VI (Astronomy Club)
Attendees: 16
On the afternoon of February 3, 2024, Antariksh VI—the Astronomy Club of VIT Pune—held an enlightening internal talk titled “Theories of Habitable Exoplanets”. Led by core member Kaushik Salunke, the session was a deep dive into the complex theories, definitions, and methods behind exoplanet research, especially focusing on the conditions and criteria for habitability. This area of study, increasingly popular among astrophysicists, seeks to answer fundamental questions about the existence of life beyond Earth.
Session Highlights
1. Definition of an Exoplanet
- Basic Definition: Exoplanets are planets that orbit stars outside of our solar system. They vary significantly in size, composition, and orbit. Kaushik explained that understanding exoplanets helps scientists broaden their perspective of planetary diversity beyond the familiar examples of our own solar system.
- Criteria for Classification: Kaushik clarified that for an object to be classified as an exoplanet, it must have a mass below the limit required for thermonuclear fusion of deuterium, calculated to be 13 Jupiter masses. Objects above this mass threshold are classified as "brown dwarfs," regardless of their formation process or location.
2. Milestones in Exoplanet Discovery
- Early Evidence and Detections: The talk highlighted key moments in exoplanet discovery:
- 1917: Early indications of planets beyond our solar system began to emerge.
- 1988: The first unconfirmed detection sparked further investigation into exoplanetary research.
- 1992: The first confirmed detection of an exoplanet orbiting a pulsar was made, a breakthrough in the field.
- 2024: As of this year, more than 5,600 exoplanets have been confirmed, with many of them discovered through advanced observation techniques.
3. Notable Planets and Observatories in Exoplanet Research
- Noteworthy Exoplanets: Kaushik discussed some of the most remarkable exoplanets discovered to date:
- Poltergeist and Phobetor: Among the first confirmed exoplanets, orbiting a pulsar.
- Pegasi 51b (Hot Jupiter): One of the first gas giants discovered orbiting close to its star.
- Draugr: A small exoplanet discovered within the PSR B1257+12 system.
- Important Observatories and Telescopes:
- Spitzer Space Telescope: Notable for its infrared observations, contributing to exoplanet research.
- TRAPPIST (Transiting Planets and Planetesimals Small Telescope): A telescope that contributed significantly to the discovery of the TRAPPIST-1 planetary system.
- Kepler and Kepler K2 Missions: Major contributors to exoplanet discovery, including identifying Earth-sized planets within habitable zones.
- James Webb Space Telescope (JWST): Kaushik noted JWST’s role in pushing the limits of observation, particularly for detecting atmospheric compositions of exoplanets.
4. Definition of a Habitable Exoplanet
- Kaushik outlined the essential characteristics that define a habitable exoplanet:
- Solid Surface: A stable surface is necessary to support complex life forms and create stable environmental conditions.
- Presence of Water: Liquid water is considered vital for life as we know it, making it a key criterion for habitability.
- Stable Atmosphere: A suitable atmosphere protects against harmful radiation and helps regulate surface temperatures, which is crucial for maintaining habitable conditions.
5. Theories on the Habitability of Exoplanets
- Goldilocks Zone (Habitable Zone): Kaushik described the habitable zone as the region around a star where temperatures allow liquid water to exist on a planet’s surface. The habitable zone varies depending on the star’s type and brightness.
- Greenhouse Gases: He explained the role of greenhouse gases in trapping heat, which can create a stable, moderate climate on a planet, potentially making it more habitable.
- Atmospheric Composition: The mixture of gases in an exoplanet’s atmosphere is critical for determining its potential to support life. Certain gases, like oxygen and methane, may indicate biological processes.
6. Factors Affecting Habitability
- Stellar Type: The type and age of a star greatly influence the habitability of its planets. Stars with stable energy output are more likely to host habitable planets.
- Planetary Composition: The materials that make up a planet—such as rock, gas, or ice—impact its habitability. Rocky planets are considered more likely to support life.
- Magnetic Fields: Kaushik pointed out that magnetic fields can protect a planet from harmful cosmic and solar radiation, which plays a role in preserving atmospheric stability and habitability.
7. Methods for Detecting Habitable Exoplanets
- Transit Photometry: This method involves observing the decrease in a star’s brightness when a planet passes in front of it. By analyzing the amount of dimming, scientists can infer the planet’s size, orbit, and possible atmospheric characteristics.
- Doppler Spectroscopy: Also known as the “wobble method,” Doppler spectroscopy detects exoplanets by measuring shifts in the star’s light spectrum caused by gravitational pull from an orbiting planet.
- Direct Imaging: With powerful telescopes, scientists can capture images of exoplanets by blocking out the host star’s light. Though challenging, this technique is advancing, especially with tools like the JWST.
8. Examples of Potentially Habitable Exoplanets
- Proxima Centauri b: Orbiting the nearest star to the Sun, Proxima Centauri b lies within the habitable zone, and its proximity makes it a prime candidate for future study.
- Kepler-452b: Often called “Earth’s cousin,” this exoplanet orbits a star similar to the Sun and is located in the habitable zone, making it a significant target for studying Earth-like conditions.
- TRAPPIST-1e: This rocky exoplanet within the habitable zone of the TRAPPIST-1 system is considered highly promising for the study of potentially habitable environments.
9. Planet Profiling
- Target Attributes for Habitability: Kaushik compared Earth-like conditions to those on several known exoplanets, focusing on distance from the star, atmospheric composition, and temperature.
- Proxima Centauri b: A rocky composition with an estimated equilibrium temperature of 234 K.
- TRAPPIST-1e: Compact atmosphere and an equilibrium temperature around 246.1 K.
- Kepler-452b: Likely a super-Earth with a stable environment and equilibrium temperature around 263 K.
10. Challenges in Studying Habitable Exoplanets
- Technological Limitations: Existing telescopes and instruments have limitations in observing and analyzing exoplanets in detail, especially those located far away.
- Distance and Time Constraints: Many exoplanets are located light-years away, making it challenging to gather direct information.
- Atmospheric Analysis Complexity: Studying exoplanetary atmospheres requires advanced techniques, as these atmospheres are often faint and difficult to characterize.
11. Conclusion and Future Prospects
- Advancements in Technology: Kaushik concluded by discussing how ongoing advancements in telescopic and analytical technologies are steadily improving our ability to detect and study habitable exoplanets.
- Search for Biosignatures: Future missions aim to search for biosignatures like oxygen and methane, which could indicate life.
- Collaborative Efforts: International collaboration among space agencies and research institutions will be essential for future exoplanet exploration.
Closing and Participant Feedback
The session lasted approximately 1 hour and 10 minutes. Audience members expressed keen interest, asking open-ended questions about atmospheric analysis, the limits of current technology, and future exploration plans. Attendees appreciated Kaushik’s presentation but suggested a more research-oriented approach, indicating a desire for deeper insights into the scientific challenges and advancements in exoplanet studies.
The talk successfully fostered curiosity about habitable exoplanets, underscoring the importance of continued research and technological innovation in the search for life beyond Earth.
