House Hunting In The Galaxy

House hunting is daunting, whether looking for a new home on Earth or searching for a new planet to call home in the galaxy. Just like searching for a new house on Earth, searching for a habitable planet in the universe requires careful consideration of various factors, from location and size to atmosphere and the potential for life. But unlike house hunting on Earth, the stakes are much higher when searching for a new planet to call home. Not only are the distances involved astronomical, but the conditions that make a planet habitable are much more restrictive.

Let us explore factors that make a planet 'habitable.'

1. Distance from the host star: The planet must be at the proper distance from its host star to allow liquid water to exist on its surface. This is known as the "habitable zone" or "Goldilocks zone," It is the region around a star where temperatures are just right for liquid water to exist. This is the Sun in our case, and we are two planets away from the Sun.
2. Composition of the atmosphere: A planet's atmosphere plays a critical role in regulating its temperature and protecting it from harmful radiation. The presence of an atmosphere similar to Earth's (with a balance of gases such as oxygen, nitrogen, and carbon dioxide) would make the planet more likely to be habitable.
3. Size and mass: The size and mass of a planet also play a role in determining its habitability. A planet that is too small or too large would not be able to support life as we know it.
4. Geology: A planet with active geology and geophysics is likelier to have the right conditions for life. A planet with active plate tectonics, volcanic activity, weather patterns, and a magnetic field to protect its surface from harmful radiation is essential for habitability.
5. Presence of water: The presence of liquid water on the surface of a planet is considered a key factor for habitability. Water is necessary for life as we know it and plays a critical role in regulating a planet's temperature and atmosphere.
6. The presence of light: A planet in the "habitable zone" but too far from its host star to receive enough sunlight for photosynthesis would not be able to support life as we know it.
7. The presence of life: The presence of microbial life, or even the biosignatures that indicate the presence of life, on a planet would be the strongest indication of habitability.
8. The orbit's stability: A planet's orbit should be stable for a long time so that the conditions on the planet are not too affected. A planet's rotation determines the length of its day and night and the distribution of sunlight across its surface.

Let's use these factors to search for 'habitable' planets, but we will first search for potential planets in our solar system.

One of the most promising candidates is Mars. The planet has a similar rotation period to Earth, and its surface features, such as mountains and valleys, are identical. Additionally, recent discoveries of water on Mars have sparked excitement about the possibility of supporting human life on the planet. NASA has plans to send astronauts to Mars soon, and scientists are currently researching ways to terraform the planet to make it more habitable.

While Mars shares some similarities with Earth, such as its rocky terrain, it presents challenges for potential habitation. The planet’s gravity is weaker than Earth’s, and its atmosphere is extremely thin, likely due to a weaker magnetic field that couldn’t protect it from solar flares over time. — Science Sensei

Another planet that is being studied is Venus. Despite its thick atmosphere, which would be hostile to humans, scientists are looking into the possibility of living in floating cities in the planet's upper atmosphere. This would allow for protection from extreme temperatures and pressure on the surface while still being able to harness the planet's resources.

NASA's Mars rover on Mars; Source: NASA

Beyond our solar system, there are exoplanets, planets orbiting other stars, that scientists are studying for their potential to support human life. These exoplanets are located in what is known as the "habitable zone," where conditions are just right for liquid water to exist on the planet's surface. This is considered one of the most critical requirements for life as we know it. Here are three of my favourite habitable planets outside our solar system (Exoplanets).

Kepler-452b

• Alternative names: KOI-7016.01
• Planet Type: Super Earth; Terrestial, Rocky planet
• Star: G-type
• Mass: 3.29 Earths
• Orbital Periods: 384.8 days
• Distance to Earth: 1799 light years
• Temperature: Teq: 265 K (−8 °C; 17 °F)‎

Kepler-442b

• Planet type: Super Earth
• Star: (K-type), 40% less massive than our Sun.
• Temperature: Teq: 233 K (−40 °C; −40 °F)‎
• Mass: 2.36 Earths
• Distance to Earth: 1,115 light years
• Orbital period: 112 days
• Surface gravity: 30% stronger than Earth

Kepler-22b

• Planet type: Ocean-like planet
• It has visible jet streams and large groups of clouds
• The first exoplanet confirmed by Kepler to orbit in the habitable zone of its star
• Orbital period: 290 days
• Distance from Earth: 620 light-years
• Temperature: 262 K (−11 °C; 12 °F)
• Star: G-star class sun like our sun, but a little bit smaller and colder

*reference: Wikipedia, NASA.