The world of astronomy and the search for extraterrestrial life is mourning the recent passing of Frank Drake, the creator of the Drake Equation for estimating the number of technically advanced planets in the Milky Way, but that hasn’t stopped those same astronomers and scientists from conducting their own searches and estimates. In fact, two such planets may have been identified recently no more than a mere 100 light years away – Earth-like orbs orbiting small stars in their habitable ‘Goldilocks’ zones, making them strong contenders for hosting extraterrestrial life. Meanwhile, another group of scientists using the latest data from our most advanced space telescopes have gone far beyond Drake’s equation for the Milky Way and have calculated that the universe has the potential to hold 50,000,000,000,000,000,000,000 other habitable planets – that’s 50 sextillion -- like Earth. Do you suddenly feel both excited and a little crowded?
“An international team of scientists, led by Laetitia Delrez, astrophysicist at the University of Liège, has just announced the discovery of two 'super-Earth' type planets orbiting LP 890-9. Also known as TOI-4306 or SPECULOOS-2, this small, cool star located about 100 light-years from our Earth is the second coolest star around which planets have been detected, after the famous TRAPPIST-1.”
A press release from the University of Liège announced the discovery of two so-called “super-Earth planets -- with a mass higher than Earth's but still much lower than Uranus or Neptune – by astronomers from the school. Laetitia Delrez, FNRS Postdoctoral Researcher in the Astrobiology and STAR (Faculty of Sciences) research units at ULiège and lead author of an article outlining the discover in the journal Astronomy & Astrophysics, explains the team actually discovered two exoplanets orbiting LP 890-9, a red dwarf star in the constellation Eridanus in the southern celestial hemisphere. The first was found using NASA’s TESS (Transiting Exoplanet Survey Satellite) space telescope. While confirming its existence using the SPECULOOS (Search for habitable Planets EClipsing ULtra-cOOl Stars) observatories, they discovered the second planet – they were given the names LP 890-9b and LP 890-9c.
"Although this planet orbits very close to its star, at a distance about 10 times shorter than that of Mercury around our Sun, the amount of stellar irradiation it receives is still low, and could allow the presence of liquid water on the planet's surface, provided it has a sufficient atmosphere."
While both LP 890-9b and LP 890-9c are rocky planets like Earth, Francisco J. Pozuelos, a researcher at the Institute of Astrophysics of Andalusia, a former postdoctoral researcher in the Astrobiology and STAR research units at ULiège and another co-author of the paper, describes how LP 890-9c is a strong candidate for hosting life forms. Its star is about 6.5 times smaller than the Sun, which reduces the amount of radiation it spews, and its low temperature (half the surface temperature of the Sun) means the surface of LP 890-9c won’t be extra-crispy and not suitable for life. If it has surface water and/or atmospheric water vapor, it would make LP 890-9c the second most likely potentially habitable terrestrial planet currently known, behind only the three or four exoplanets in the Goldilocks zone around TRAPPIST-1 – another ultra-cool red dwarf 40.7 light-years away in the constellation Aquarius.
“This gives us a license to observe more and find out whether the planet has an atmosphere, and if so, to study its content and assess its habitability.”
Amaury Triaud, an astrophysicist at the University of Birmingham and a SPECULOOS working group leader, said in a university press release that the strong possibility of water and the proper temperature on a rocky planet make SPECULOOS-2c/LP 890-9c a good candidate for study by the superstar telescope of the moment – the James Webb Space Telescope. However, that line is getting longer fast as researchers led by astronomer Charles Cadieux of the University of Montreal revealed in a paper published recently in The Astronomical Journal that they have discovered exoplanet TOI-1452b 100 light-years from Earth which appears to have the size and mass consistent with a global liquid ocean. TOI-1452b orbits one of a close binary pair of small, dim red dwarfs, separated by just 97 astronomical units, making them look like one star. Also discovered using TESS, the only way to confirm the existence of water on TOI-1452b, making it another candidate for life form, is with the James Webb Space Telescope.
That’s two Earth-like, life-possible exoplanets discovered in the span of a few weeks. Frank Drake used his own equation to estimate the average number of planets with the ability to host intelligent life in the Milky Way at 10,000. With telescopes like the James Webb searching beyond the Milky Way, it seems like it is time to expand the estimates to the universe.
Astronomers agree. The Daily Star reminds us this week that astronomers from the University of Auckland in New Zealand in 2013 estimated that there are more than 10 billion Earth-like planets in the Milky Way galaxy that could host life forms. That was an update from the 17 billion Earth-like planets estimate made previously by the Harvard-Smithsonian Center for Astrophysics using data from the Kepler space observatory. The University of Auckland’s astronomers used gravitational microlensing to find Earth-size planets that orbit at twice the Sun-Earth distance that are cooler than Earth but still habitable, making their estimate considerably higher. From there, pure arithmetic takes over. if the Milky Way contains 100 billion Earth-like planets, and there are approximately 500 billion galaxies, that puts the total number of habitable planets in the universe at a zero-filled 50 sextillion. Throw in the possibility that life could form on a planet that is not Earth-like and that estimate becomes mind-boggling.
Of course, while that 50 sextillion habitable planets estimate blows Frank Drake’s estimate out of the water, it brings Enrico Fermi’s paradox into play. If there are so many planets with the potential to harbor life … where are the aliens? Are we humans a one-in-50-sextillion accident or the product of a real creation story? Will James Webb find what Drake, Fermi, Kepler and others couldn’t – life on another planet … in another solar system or galaxy?
It is truly an exciting time to be an astronomer.