Last week, scientists announced the discovery of an Earth-like planet orbiting Proxima Centauri — our closest star and source of life — which might support life. This exoplanet represents one of the nearest possible candidate planets for human habitation ever found so far.
But how close are we cosmically speaking? To answer that question, we analyzed data from Kepler telescope’s planet-hunter capabilities.
Proxima Centauri
Proxima Centauri, part of Alpha Centauri system and located 4.2 light years from Earth in Centaurus constellation, is our nearest star system. As a red dwarf it emits much less energy and its surface temperature reaches approximately 3000 degrees Celsius; additionally it may host a planet similar to Mercury with an equilibrium temperature close enough for water molecule existence on its surface. This planet was detected orbiting it by scientists back in 2016.
The planet, with a radius of approximately 1.07 Earth masses, likely features surfaces composed of iron and nickel and is suspected of possessing dense atmospheres composed of carbon dioxide and other gases. It was one of the greatest breakthroughs in astronomy; unfortunately it cannot be observed with current telescopes (largest on Earth can only detect objects with an resolution of about one arcsecond); additionally its system would need to align perfectly with a star in order to be detected.
Astronomers have discovered over 3500 planets orbiting other stars than our Sun. Most discoveries were made with the Kepler space telescope, which observes brightness dips on host stars to detect planets. Astronomers use these data to estimate size and location; additionally, planets may also be detected by tracking their host star’s motion to calculate mass and distance estimates from it.
At 0.05 AU (7.5 million km; 4.6 million miles), Proxima Centauri exoplanet orbits at an approximate distance of 0.05 AU, becoming one of the closest inhabitable planets to our solar system and approximately one fourth the size of Earth. One orbit around its parent star takes 11.2 days, suggesting this planet could potentially support an atmosphere. Regardless, extreme flares could potentially strip any current atmosphere.
Kepler-1649c
Kepler-1649c has recently been discovered 300 light years away, orbiting a dim star that produces very little heat, like camping next to an open fire. Due to this closeness with its host star, it falls within the habitable zone where bodies of water may form more likely forming hope for potential extraterrestrial life forms – though that won’t be easy and there remain numerous hurdles before that can happen!
Astronomers don’t yet understand much about this exoplanet that is similar in size and in the habitable zone of its star, though its habitability zone appears similar. Depending on its atmosphere, it could be warmer or cooler than Earth depending on whether it has thick layers that trap heat like Venus does or thin atmosphere that allows more exposure of UV radiation like Mars does – making this exoplanet one of the most promising exoplanets for life forms to inhabit.
Researchers have discovered an exoplanet that is both Earth-sized and in its host star’s habitable zone – making it the first planet ever discovered that fits this criteria. Furthermore, it boasts a relatively thin atmosphere that should protect it from flares from its red dwarf star and flare-ups from other stars in its system. They have not determined yet whether the planet is solid or liquid but have determined that its radius seems similar to Earth’s. Furthermore, its effective stellar flux (Seff) value matches up closely to Earth’s and thus opening up possibilities of life on this exoplanet.
The team that discovered an exoplanet used transit photometry to measure how its host star changed as it passed in front of it, then used this data as evidence that could identify it as an exoplanet. Although there can be some margin of error with this technique, they were confident enough to officially announce their discovery.
Kepler space telescope was decommissioned in 2018, having spent more than ten years searching for planets when it stopped operating in 2018. Astronomers employed a computer algorithm to sift through all this data and identify potential planets; however, due to the risk that something might slip past this software algorithm and miss something entirely, another team of scientists manually searched through rejected data manually before finally discovering Kepler-1649c as their candidate star system.
TRAPPIST-1
Scientists announced in February the discovery of TRAPPIST-1, an Earth-sized planet system orbiting within the habitable zone of a red dwarf star. While this discovery marks an important step in our search for life beyond Earth, its discovery also serves as a stark reminder that getting there would take us over 800,000 years given today’s technology.
TRAPPIST-1’s planets orbit their host star very close, and three are within its habitable zone, raising concerns among astronomers about whether liquid water could exist on their surfaces. TRAPPIST-1e may only be one-fifth as far away from its star as Earth from the Sun; therefore its days could likely be as bright as our evening twilight here on Earth.
As planets orbit their stars, they become tidally locked – meaning one side always faces towards its star while the other always points away – creating very different temperatures on both surfaces of each planet, and drastically limiting any chance for life on them.
The TRAPPIST-1 system boasts many other compelling qualities that make it an interesting research target, including being relatively dim with planets tidally locked to it; these conditions may lead to thin atmospheres which provide ideal environments for searching out water molecules; additionally, biosignatures (chemical signatures of life) could also be detected using this approach.
James Webb Space Telescope (JWST) will be used as the next step in studying TRAPPIST-1 planets’ atmospheres for any signs of life, detecting various chemical signatures like carbon dioxide and water that indicate whether life exists there or not. If life exists on these planets, they would likely release these chemicals as they rotate around their star. Astronomers hope this research will shed more light on what conditions must exist for life to exist elsewhere.
Wolf 1069
Astronomers have made an astounding discovery: Wolf 1069 b is a planet found 31 light-years away that may provide us with life. This incredible achievement was accomplished by scientists at the Max Planck Institute for Astronomy.
The team discovered an exoplanet by analyzing CARMENES spectrograph radial velocity data. Additionally, they assessed brightness and color data from nearby stars. Their work confirmed the existence of the planet while ascertaining its mass and orbital period; then compared this with computer simulations that revealed it as being composed mainly of water-rich terrain capable of supporting moderate temperatures and atmospheres.
Wolf 1069 b is thought to have an atmosphere, providing protection from high-energy electromagnetic radiation and particles from its host star as well as interstellar space. Additionally, an atmosphere would help keep water liquid on its surface. According to researchers at Yale, Wolf 1069 b may have originally been smaller and frozen planet that was gradually covered with an expanding accretion disk caused by heating by its host star before eventually expanding in size over time.
Wolf 1069 can be found in Cygnus constellation and contains 17% of the mass and 18% of its radius as our sun, located 31.2 light-years away from us. An exoplanet orbiting this star occurs approximately every 15.6 days at 0.0672 AU distance; therefore placing it into its habitable zone where liquid water could exist in its atmosphere.
This planet represents an exciting milestone: it marks the sixth Earth-mass exoplanet discovered to date and second closest rocky planet within its host star’s conservative habitable zone after Proxima Centauri b. Additionally, it joins other recently discovered life forms like TRAPPIST-1 e, LHS 475 b and GJ 1002 b and c as newly found inhabitable worlds.
Astronomers hope that future telescopes can be used to search for signs of life on other planets. Biosignatures – which indicate past or present life forms – should be detectable. But the search will likely take time.