A startling astronomical discovery was made in 2017 by astronomers. They discovered TRAPPIST-1, a red dwarf star with seven planets the size of Earth around it. That many planets are the most we have ever discovered circling a star other than the Sun.
Three factors made this finding important. First off, at only 40 light years away, the planetary system was close by. Second, like the inner planets in our solar system, all seven planets were rocky. Three of the planets were also in the habitable zone, which made them attractive candidates for the search for extraterrestrial life. Advanced telescopes, including the Hubble Space Telescope, were used to explore the extraordinary planetary system after the discovery sparked astronomers’ curiosity. These telescopes had drawbacks, though, and their results were limited by wavelength constraints. In order to concentrate on the TRAPPIST-1 system, scientists eagerly anticipated the launch of the James Webb Space Telescope. The telescope’s initial results have finally been obtained, but they are not encouraging.
What then did Webb find in one of the system’s planets? How was the composition of the planet circling TRAPPIST-1 determined? Last but not least, why are these results so crucial to astronomers? It is crucial to take into account the characteristics of the host star in order to completely grasp the relevance of Webb’s discoveries on TRAPPIST-1 b. An M-dwarf or extremely cool red dwarf star is TRAPPIST-1. Approximately 75% of all stars in our galaxy are M-dwarfs, making them the most prevalent form of star. With surface temperatures between 2400 and 3800 kelvin and masses between 0.08 and 0.6 solar masses, they are both smaller and cooler than the Sun.
For instance, TRAPPIST-1 has a mass of only 9% that of the Sun yet is 2.5 billion years older. M-dwarfs are twice as likely to host rocky planets than Sun-like stars, yet they pose a serious threat to planetary habitability. This is due to the fact that M-dwarf stars are quite active, frequently releasing massive amounts of energy and charged particles into space through flares and coronal mass ejections. Any nearby planet could be significantly impacted by these occurrences. A planet’s atmosphere can be stripped away by the powerful radiation and energetic particles emitted by M-dwarf stars, a process known as atmospheric escape, which also erodes the planet’s surface.
Planets in close orbits to the star may be particularly vulnerable to damage from this. This problem is made worse in the TRAPPIST-1 system by the close proximity of all seven planets’ orbits. These orbits are sufficiently similar that all of them may fit into Mercury’s orbit in our solar system. The closest planet, TRAPPIST-1 b, orbits the star every 36 hours and gets nearly four times as much radiation from the Sun per square meter of its surface as Earth does.
Despite all of these obstacles, astronomers decided to use the James Webb Space Telescope to study this planet. How astronomers can discern the characteristics of planets trillions of miles from Earth is one of the field’s most intriguing mysteries. The science of spectroscopy, which transformed astronomy more than a century ago, holds the key to the solution. Astronomers specifically rely on the idea of secondary eclipses to learn more about the temperature and composition of these far-off worlds. As seen from Earth, a planet blocks a little portion of brightness when it moves in front of its star.
Scientists can deduce the existence and orbit of an exoplanet by examining the dip in the star’s light curve. However, this arrangement only reveals details about the planet’s night side that faces us. Scientists need two more configurations, when the planet is on either side of its star or when it is behind the star as seen from Earth, to fully grasp the planet’s atmosphere. But given that we can’t even see the planet, why is the latter configuration so important?
The exoplanet’s infrared radiation provides the solution. Because TRAPPIST-1 b is tidally locked, only one side of it is ever illuminated by the star, leaving the other side in perpetual darkness. The dayside of the planet will be cooler if there is an atmosphere to circulate and redistribute heat. TRAPPIST-1 b emits an infrared glow while not being hot enough to produce visible light. The light that is produced when a planet passes in front of or on either side of a star is a mixture of light reflected from the star and the planet’s own infrared thermal emission.
The system appears brighter as a result. The planet, however, does not emit any infrared light during a secondary eclipse because it is not even visible. They were able to determine how much infrared light the planet was emitting by deducting the brightness of the star during the secondary eclipse from the brightness of the star and planet put together. Five secondary eclipses for TRAPPIST-1b were seen by the researchers, which is a significant accomplishment in and of itself. The brightness shift noticed by Webb is less than 0.1% because the star is over 1,000 times brighter than the planet. The conclusions are based on readings from Webb’s Mid-Infrared Instrument (MIRI), which found an infrared glow from the planet’s dayside, indicating a temperature of about 230 °C and indicating that TRAPPIST-1b is a stony, desolate planet with no discernible atmosphere.
A denser atmosphere could not be ruled out, but prior examinations with the Hubble and Spitzer space telescopes did not reveal any signs of a bloated atmosphere. Webb’s findings, on the other hand, are very compatible with a blackbody comprised of bare rock with no atmosphere to dissipate the heat. Additionally, there were no indications that carbon dioxide was absorbing light, which would be seen in these observations. With the help of this ground-breaking study, light from an exoplanet as tiny and chilly as the rocky planets in our own solar system has now been detected. It represents a substantial advance in our investigation of the viability of life on planets circling tiny, energetic stars like TRAPPIST-1. It also emphasizes Webb’s abilities to characterize temperate, Earth-sized exoplanets using its Mid-Infrared Instrument (MIRI).
The TRAPPIST-1 system was thoroughly characterized as part of the eight programs from Webb’s first year of science, one of which, Webb Guaranteed Time Observation program 1177, which this research was a part of. According to NASA, the team is presently conducting more secondary eclipse observations of TRAPPIST-1b with the aim of eventually capturing a complete phase curve illustrating the shift in brightness across the planet’s entire orbit. They will be able to learn more about the temperature of the globe and other important information as a result. Recently, astronomers discovered the first dark galaxy to have no visible light emitted from it. This might be able to resolve the issue of the missing satellite, one of astronomy’s biggest challenges.
