Cluster 70A Final Draft: The Significance of Proxima B PDF

Ivan Ocegueda T.A: Caitlyn Fick Cluster 70A Dis 1B 8 December 2023 The Significance of Proxima B [Introduction] An exoplanet is a planet that orbits a star outside of the solar system. In 1995, the announcement of a new exoplanet named 51 Pegasi b was discovered orbiting its star, 51 Pegasi (A...

Ivan Ocegueda T.A: Caitlyn Fick Cluster 70A Dis 1B 8 December 2023 The Significance of Proxima B [Introduction] An exoplanet is a planet that orbits a star outside of the solar system. In 1995, the announcement of a new exoplanet named 51 Pegasi b was discovered orbiting its star, 51 Pegasi (Akeson et al. 2013). The star is located in the constellation Pegasus, and it is about 48 light-years away from Earth. As clarification, a light-year is equivalent to about six trillion miles. Within the exoplanet field of astronomy, the discovery of this exoplanet piqued the field considering discoveries of new exoplanets continue to increase to this day. The findings have been so integral for astronomers that they have made the gathered information accessible to the quickly interested general public. There were exoplanets that had been discovered prior to 51 Pegasi b such as Gamma Cephei Ab in 1988 and PSR B1257+12 B in 1992 which orbit Gamma Cephei and PSR B1257+12, respectively; however, the discovery of 51 Pegasi b has raised the curiosity of astronomers regarding the possibility of a new Earth. Because of this, on August 25, 2016, an astronomer by the name of Guillem Anglada-Escudé, along with his colleagues, published an article named "A Terrestrial Planet Candidate in a Temperate Orbit Around Proxima Centauri." The article discussed the findings of a new exoplanet named Proxima b that is orbiting around Proxima Centauri, the closest star to Earth, which is currently sitting about 4.2 light-years away. The purpose of the article was to determine the parameters of Proxima b including its orbital period, its semi-major-axis distance, and other characteristics. Astronomers hear about new exoplanets similar to Earth nearly every week, and as a result of these hearings, mankind's excitement increases (Schulze-Makuch and Guinan, 2017). Although this transpires, the habitability of new exoplanets is perpetually questioned within the field due to these especially unknown territories having concerns regarding tidal locking, abrupt stellar winds, and asteroid impacts. As astronomers gather parameters of newly discovered exoplanets using discovery procedures trialed in Anglada-Escudé (2016) and look toward the future of technology, they also delve into the existence of Proxima b by questioning the habitability of the planet and by acknowledging the potential risks of life on distant exoplanets. [Proxima b's Origins] In Anglada-Escudé (2016), the data that was collected regarding Proxima b was observed using radial velocity instruments. Radial velocity is the velocity of an object between the observer and the object. In other words, it is the speed at which an object is moving toward or away from an observer. A redshift indicates positive radial velocity, which implies an object moving away from the observer. On the contrary, a blueshift indicates negative radial velocity, which implies an object moving toward the observer. The first radial velocity instrument that was used is called the High Accuracy Radial Velocity Planet Searcher, or HARPS for short. The second instrument is called the Ultraviolet and Visual Echelle Spectrograph, or UVES. HARPS measures radial velocities of stars which help detect planets, and UVES collects light from these planets to gain information regarding the temperature and physical properties of them (Endl and Kürster, 2008). Spectroscopy helps in measuring how much light is received at different wavelengths which can reveal physical properties such as the density, composition, and pressure of the exoplanet. The goals of many studies were to gather radial velocity data to detect signatures, also known as wavelengths, of low mass stars that are potentially present in their respective habitable zones. These zones, given the name HZ, are the areas in which a planet can keep an atmosphere and have water on its surface thanks to its star. HARPS had delivered more than 100 new habitable planet candidates (Pepe et al. 2011). In addition, data has shown that about 20% of all solar-type stars, such as the Sun, have Earth-sized planets orbiting their HZ (Wandel, 2017). However, there may be a reason as to why life on Earth is unique and why life on other planets will continue to be extremely rare. It is possible that life may only be allowed on Earth-like planets orbiting Sun-like stars, and as a result of this, only 10% of the many candidates will qualify as potentially habitable (Wandel, 2017). While 10% may seem disappointing, it is still a significant amount, and it is an important reason as to why life beyond Earth is still being explored. Using the instruments, astronomers determined that Proxima b was about 1.3 times the mass of Earth and orbits Proxima Centauri with a period of about 11.2 days. In Anglada-Escudé (2016), one figure at the beginning of the article showed waves of lines, and the peak for all three graphs was at around 11.2 days. This 11.2-day period refers to the detection of a Doppler signal, meaning that every 11.2 days, there was a signal that astronomers noticed. This signal was similar to that of a police siren as there were red and blue wavelength shifts. In another figure, there were measurements that were used to calculate the radial velocity of the planet, determining if the planet was moving closer to or farther from us. Because the 11.2-day period represents when the signal goes off, this means that the speed and signal are patterns (Anglada-Escudé et al. 2016). This signal thus led to the discovery of Proxima b. [The Questioning of the Habitability of Proxima b] Anglada-Escudé's team also found that Proxima b is in Proxima Centauri's HZ; however, while its discovery may seem exciting, Proxima b being in the livable area surrounding Proxima Centauri does not mean the planet itself is habitable. While tidal locking, where one side of a planet perpetually faces its star, has not been confirmed on Proxima b, life on the planet is still unknown considering there's a possibility that one side of the planet may experience extremely high temperatures compared to the other side. As a result, astronomers thus began to question its habitability after its initial discovery. To truly determine whether an object or an area is safe, professionals must compare said object or area to something similar. Because of this, comparing Proxima Centauri and Proxima b to the Sun and Earth would be beneficial as humans have resided on Earth since its origins. The effective temperature of the Sun is about 5,800 Kelvin while the effective temperature of Proxima Centauri is only about 3,050 Kelvin (Güdel et al. 2004). In addition, Proxima Centauri has a luminosity of 0.15% of the Sun and a mass of about 12% of the Sun. Moreover, Proxima b is 0.05 astronomical units away from Proxima Centauri. For reference, 1 AU (an astronomic unit) is about 150 million kilometers, which is the distance between Earth and the Sun. Proxima b would then only be 7.5 million kilometers away from Proxima Centauri. Proxima b is thus closer to its star, but its star is much smaller, cooler, and dimmer. As a result of this, Proxima Centauri will live longer than the Sun because of its smaller size and allows for humans to have a possibility to move from Earth to Proxima b if it is ever considered habitable. [The Worries with Exoplanets] Moreover, another way to potentially test an exoplanet's habitability is to determine the rate at which its atmosphere will weaken due to stellar winds as this would essentially be a way to test Proxima b's durability. Stellar winds are a flow of fast particles that come off a star and travel throughout each solar system. If a stellar wind were to interact with a planet's atmosphere, it could disrupt communications and satellites, causing radiation to spread. It was found that about 2% of the atmospheric oxygen on Earth had been lost over 3 billion years. It was also found that all of Proxima b's atmosphere could be depleted within 100,000,000 years (Dong et al. 2017). As a result, Proxima b's atmosphere may not be capable of living very long when stellar winds are high. However, the HZ of Proxima b may evolve over time, giving it a possibility to eventually strengthen its atmosphere. In addition to this, astronomers have considered the possibility of a debris belt being located near Proxima b that could result in asteroid impacts, and this can have a significant threat to life on Proxima b due to an increase in the possibility of extinction (Siraj and Loeb, 2020). However, it\'s essential to conduct more observations in the future to confirm whether the debris belt exists or not. [Conclusion] Overall, astronomers have been using radial velocity instruments to explore exoplanets and to ultimately bring Proxima b to life. In fact, these instruments originally trialed in Anglada-Escudé (2016) were so useful for discovering new planets that they were used in nearly every study. It is evident that mankind is excited for the new possibilities that a new Earth will bring, but unfortunately, it may be too early to look forward to a new planet as technology is not as advanced as it could one day be. In the near future, there will be improved spectrometers that can be expected to specifically improve exploration of exoplanets' atmospheres (Encrenaz, 2022). Thus, astronomers will continue to question whether Proxima b will be the next Earth for perpetually evolving humans. Bibliography Akeson, R. L., X. Chen, D. Ciardi, M. Crane, J. Good, M. Harbut, E. Jackson, et al. 2013. "The NASA Exoplanet Archive: Data and Tools for Exoplanet Research." *Publications of the Astronomical Society of the Pacific* 125 (930): 989. Anglada-Escudé, Guillem, Pedro J. Amado, John Barnes, Zaira M. Berdiñas, R. Paul Butler, Gavin A. L. Coleman, Ignacio de la Cueva, et al. 2016. "A Terrestrial Planet Candidate in a Temperate Orbit around Proxima Centauri." *Nature* 536 (7617): 437--40.. Dong, Chuanfei, Manasvi Lingam, Yingjuan Ma, and Ofer Cohen. 2017. "Is Proxima Centauri b Habitable? A Study of Atmospheric Loss." The Astrophysical Journal Letters 837 (2): L26.. Encrenaz, Therese. 2022. 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