How many exoplanets exist? Habitable zones, life, and what we are really discovering
We are not alone… but we still don’t know how much
In recent years, astronomy has gone from knowing no planets beyond our Solar System to discovering thousands. Today we know that exoplanets are not the exception—they are the rule in the Universe.
But the big question remains the same: how many of those worlds could resemble Earth?
If you want to explore a specific example, you can read about Gliese 12 b, one of the most interesting exoplanets discovered recently.
🔭 How many exoplanets have been discovered?
As of 2026, more than 5,500 exoplanets have been confirmed, distributed across thousands of planetary systems.
And the most fascinating part: these are only the ones we have been able to detect with current technology. Estimates suggest there could be hundreds of billions of planets in our galaxy alone.
In other words, almost every star we see in the sky likely has its own planetary system.
🚀 Which telescope has discovered the most exoplanets?
The main protagonist in exoplanet detection has been NASA’s Kepler space telescope.
Kepler revolutionized astronomy by systematically using the transit method, continuously observing more than 150,000 stars.
Why has it been so effective?
- Continuous observation over several years
- Wide field of view
- High photometric precision
Today, its successor, TESS, continues this work by searching for exoplanets closer to Earth, ideal for detailed studies.
🌍 How many are in the habitable zone?
Of the thousands of exoplanets discovered, only a small fraction lies within the so-called habitable zone.
It is estimated that there are between 50 and 70 potentially habitable exoplanets, although this number is constantly evolving with new discoveries.
However, being in the habitable zone does not necessarily mean that a planet is truly habitable.
☀️ What exactly is the habitable zone?
The habitable zone is the region around a star where a planet could have liquid water on its surface, a condition considered essential for life as we know it.
But many additional factors come into play:
- Presence of an atmosphere
- Chemical composition
- Stellar activity
- Magnetic field
For example, Venus lies close to the habitable zone… and yet it is an extremely hostile planet, with temperatures above 400°C and a dense, corrosive atmosphere incompatible with life.
🧬 What is the probability of life?
This is where we enter one of the biggest questions in science.
We know that planets exist, and that some are located in habitable zones… but we do not know how many actually develop life.
To address this question, scientists use a theoretical model known as the Drake Equation.
📊 The Drake Equation
Proposed in 1961 by astronomer Frank Drake, this equation attempts to estimate the number of technologically advanced civilizations in our galaxy.
It considers factors such as:
- The rate of star formation
- The number of planets per star
- The fraction of habitable planets
- The probability of life emerging
- The evolution toward intelligent life
The challenge is that many of these values are still unknown.
However, thanks to the discovery of thousands of exoplanets, we can now better constrain some of these terms.
🌌 La Palma and the search for other worlds
Detecting exoplanets is only the first step. The next is understanding them.
In this context, the telescopes at the Observatorio del Roque de los Muchachos play a key role in characterizing atmospheres and monitoring planetary systems.
From La Palma, astronomers study stars, analyze spectra, and contribute to answering one of humanity’s deepest questions:
Are we alone in the Universe?
✨ Looking at the sky from a new perspective
When we observe the night sky today, we no longer see just stars—we imagine other worlds.
We see planetary systems, potentially habitable worlds, and environments where life very different from ours could exist.
The discovery of exoplanets has not only changed astronomy. It has changed the way we understand our place in the Universe. However, even if we know these worlds exist, reaching them—or communicating with possible life—remains far beyond our current capabilities.