Why We Haven't Found Any Earth-Like Planets
Cool Worlds・30 minutes read
NASA's Kepler mission aimed to find Earth-like planets orbiting Sun-like stars, predicting around 50 Earth-like planets based on simulations and peer-reviewed research. However, challenges such as instrumental effects and financial constraints cast doubt on the existence of Earth analogues, impacting future space missions seeking habitable planets.
Insights
- The Kepler mission, launched by NASA in 2009, aimed to find Earth-like planets orbiting stars similar to the Sun, with a primary goal of measuring the frequency of terrestrial planets in the galaxy to aid future space telescopes in searching for signs of life.
- Despite predictions and simulations suggesting the presence of around 50 Earth-like planets, none have been validated so far, casting doubt on the existence of Earth analogues and challenging estimates of their frequency, impacting the design and success of future space missions seeking habitable planets.
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Recent questions
How many Earth-like planets did the Kepler mission predict?
50 Earth-like planets.
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Summary
00:00
Kepler Mission: Predicting 50 Earth-like Planets
- The Johnson Space Center's Mark Caro from the Houston Chronicle inquired about the expectation of 45 or more Earth-like planets resulting from a study.
- The study's estimate of 50 Earth-sized planets was reached by assessing the mission's capabilities in terms of photon and length emission, along with the stars themselves.
- In 2009, NASA launched the Kepler mission, aiming to find Earth-like planets orbiting stars similar to the Sun.
- Kepler's primary objective was to measure the frequency of terrestrial planets in the galaxy, crucial for future space telescopes searching for signs of life.
- Kepler's results would influence the design of future space telescopes, like LUVOIR and HabEx, based on budget constraints and the number of stars surveyed.
- Kepler's prediction of around 50 Earth-like planets was based on simulations and peer-reviewed research, focusing on stars similar to the Sun.
- The NASA Exoplanet Archive lists 4724 planetary candidates, with only three potentially habitable Earth-sized planets around Sun-like stars.
- Among the three candidates, KOI 549901 and 7179 are challenging signals near the detectability threshold, with potential issues in their transit shapes.
- KOI 7235.01 was initially flagged as a false alarm due to its orbital period, potentially falling outside the Earth proxy zone.
- The prediction of 50 Earth-like planets by Kepler was based on extensive planning, simulations, and peer-reviewed research, aligning with the mission's goal to detect and count other Earths.
17:12
Challenges in Detecting Earth-Like Planets
- Astronomers Chris Burke and Fergul Malali argue in recent papers that long-period low signal transits, like those claimed to be high-confidence planets, can be caused by instrumental effects onboard spacecraft, not actual planets.
- Kepler's validated discoveries, Kepler-452b and Kepler-186f, were not confidently validated as Earth twins due to not meeting the 99% confidence level required, despite media attention.
- Kepler-186f orbits a red dwarf star, not a sun-like star, and Kepler-452b receives half the radiation Earth does, placing them in the red danger zone for being instrumental artifacts.
- Press releases about Earth-like planets are more popular than subsequent articles questioning their validity, leading to misinformation in the media and online.
- Planets like KOI-54901 and 71-7901, with low signals and few transits, have a 50% chance of being bogus, casting doubt on the existence of Earth analogues.
- Despite predictions of 43 detected Earth-like planets, none have been validated, leading to discrepancies in estimates of Earth-like planet frequency.
- Stellar noise levels observed by Kepler exceed pre-launch predictions, affecting the detection of Earth analogues and challenging initial expectations.
- Simulation results using actual noise values from Kepler show a significant drop in predicted Earth analogues, with only one likely detection among G-type stars.
- The ambiguity in Earth analogue detection data from Kepler hinders precise estimates of Earth-like planet frequency, impacting future space missions seeking habitable planets.
- The lack of consensus on Earth-like planet frequency poses challenges for future space missions aiming to find habitable planets, as current data does not provide clear constraints on the prevalence of Earth analogues.
34:30
"Hybrid Mission for Exoplanet Imaging Challenges NASA"
- The recent decadal survey in astronomy highlighted the recommendation for a hybrid mission combining elements of Levoir and Habex, aiming for a six-meter class design, with an estimated cost of $11 billion. This mission, focused on exoplanet imaging to find other Earths, provides leverage for future lobbying efforts, although concerns exist about potential cost overruns and the challenge of securing funding from NASA.
- The cost estimates for different versions of the mission, including an eight-meter design at $18 billion and a 15-meter design at $24 billion, raise doubts about NASA's ability to afford such projects. The precarious financial situation poses a risk to the mission's success, emphasizing the need for careful planning and consideration of unexpected challenges, as seen with the Kepler mission, to ensure the dream of exploring exoplanets is realized effectively.
