Tucked inside a quiet solar system, in the area of sky outlined by the constellation Aquarius, orbits a planet named TRAPPIST-1d, the third of seven planets in a system positioned 41 light years from our vantage point. TRAPPIST-1d is a rocky, Earth-like planet, meaning that it is roughly the same size and mass as our home.
TRAPPIST-1d has a radius that is about three quarters the size of Earth, and a comparable mass just a little heavier. Planets like this are of intense interest to astronomers because they are so like our own. In many respects, this planet is the most habitable exoplanet found so far. It is not large enough to retain light gasses like hydrogen and helium, which could destroy nascent life and it is comfortably situated in the star’s habitable zone.
All of the TRAPPIST-1 planets are close to its star; the entire system can fit inside the orbit of Mercury. All of these planets are racing around their home star and TRAPPIST-1d has a year that is a mere 4 Earth days.
Yet, TRAPPIST-1d’s proximity to its host star, merely 2.2 million kilometers, would initially hint that it is a world bathed in lethal radiation. Orbiting a red dwarf star can be dangerous for any life that might be trying to make it on the surface. While these stars’ lifetimes are measured in the trillions of years - which is a good thing because it gives life a long time to evolve if its there - their early life is defined by huge stellar activity and raging eruptions that could bake anything living on the surface.
However, later on, things settle down and due to being a relatively cool star compared to ours, the light and heat it receives becomes benign, only 4.3% of that which reaches our Earth from our more boisterous Sun.
This serendipitous combination of distance, host star, and proportion places TRAPPIST-1d in an inintriguing position. At this point in the star’s life its light might heat its surface just enough to sustain liquid water. But any life trying to make it there must overcome one more obstacle.
The close proximity ot TRAPPIST-1d may put the star in a state of tidal locking, this is a condition where the planet’s daily rotation matches its revolution around the star, placing one side always facing the star whilst the other is cloacked in darkness – a stark, perpetual contrast. Astronomers believe that tidally locked planets may harbor life at the terminator zone of the surface, the line denominating constant darkness with continual heat and radiation.
In this canvas of cosmic chaos and order, TRAPPIST-1d is a tantalizing world. It forces us to abandon our assumptions and welcome the plausibility of life’s existence in corners of the universe we previously dismissed as devoid or hostile. We wait anxiously for more observations.
In the apparent silence of the cosmos, TRAPPIST-1d resounds loudly in the ears of our curiosity, a cosmic chant luring us to explore beyond the confines of our own world. In the cosmic theater, 41 light years is a mere stride. As we gaze on these alien lands upon the cosmic horizon, the symphony of the stars resonates within us, a celestial music reminding us of both our insignificance and potential within this infinite cosmic orchestra.