1.CR
A transit observation method is used to observe planets. When a planet orbits a star, there is a brief period when it blocks the star from Earth's view. By calculating the duration of this period, the orbital speed of the planet can be determined. It has been found that almost all planets close to their stars orbit at very high speeds. However, in our solar system, the larger planets orbiting the Sun are farther away from it. Therefore, we can conclude that in the universe, it is rare for planets to orbit their stars slowly like the planets in our solar system.
Which of the following, if true, would most weaken the argument presented in the passage?
(A) The transit observation method is not suitable for detecting small, Earth-like planets.
(B) Planets orbiting distant stars have been found to have a wide range of orbital speeds.
(C) The composition of planets in other solar systems is vastly different from those in our solar system.
(D) The transit observation method has only been used to study a small fraction of the known stars in the universe.
(E) Larger planets are more likely to be detected by the transit observation method than smaller ones.
A recent study conducted by a team of astrobiologists suggests that the potential for life on other planets may be more diverse than previously thought. While carbon is often considered the most likely basis for extraterrestrial life due to its abundance and stability, the researchers propose that other elements, such as silicon, could also serve as the foundation for life under certain conditions. They argue that the presence of liquid water, a stable energy source, and a protective atmosphere are more critical factors in determining a planet's habitability than the abundance of any particular element. However, the study acknowledges that carbon-based life remains the most probable form of life in the universe, given its prevalence and versatility.
The findings of the study mentioned in the passage, if accurate, most strongly support which of the following conclusions?
(A) The search for extraterrestrial life should focus exclusively on planets with high concentrations of carbon.
(B) Silicon-based life is more likely to exist than carbon-based life on planets with specific environmental conditions.
(C) The abundance of an element is not the sole determining factor in the emergence of life on other planets.
(D) Liquid water is the single most important prerequisite for the development of life on any planet.
(E) The majority of habitable planets in the universe are likely to host only carbon-based life forms.
答案:
2.DI
The question of whether life exists beyond the confines of our pale blue dot has captivated the human imagination for centuries. As our understanding of the universe has exponentially grown, so too has our insatiable curiosity about the tantalizing possibility of extraterrestrial life thriving in the uncharted depths of the cosmos. The Fermi Paradox, a perplexing conundrum named after the brilliant physicist Enrico Fermi, encapsulates the puzzling dichotomy between the staggeringly high probability of alien life and the deafening silence of the universe. If the universe is indeed teeming with billions of stars and potentially habitable planets, why have we not yet detected any unequivocal signs of intelligent life beyond Earth?
The Drake Equation, a thought-provoking framework developed by the visionary astronomer Frank Drake in 1961, provides a tantalizing glimpse into the potential prevalence of communicative civilizations in our galaxy. This equation meticulously takes into account a myriad of factors, such as the rate of star formation, the proportion of stars harboring planetary systems, the number of habitable planets per system, and the probability of intelligent life not only emerging but also surviving long enough to develop advanced communication technologies. While the precise values for each parameter remain shrouded in uncertainty, even the most conservative estimates suggest that the Milky Way could potentially host millions, if not billions, of technologically advanced civilizations.
However, despite decades of diligent searching and the tireless efforts of countless scientists and enthusiasts, no conclusive evidence of extraterrestrial intelligence has been uncovered. This glaring discrepancy between the ostensibly high probability of alien life and the complete lack of tangible evidence for its existence lies at the very heart of the Fermi Paradox. A plethora of theories have been proposed to explain this perplexing contradiction, ranging from the rare Earth hypothesis, which posits that the intricate conditions necessary for life to evolve are exceedingly uncommon, to the intriguing notion that advanced civilizations may deliberately choose to remain hidden or isolated, either out of fear, indifference, or a desire to protect less advanced species from the potentially devastating consequences of contact.
One possible resolution to the Fermi Paradox is the mind-boggling scale of the universe and the inherent limitations of our current detection methods. The Milky Way galaxy, a majestic spiral of stars and cosmic dust, spans an awe-inspiring 100,000 light-years, while the observable universe extends an unfathomable billions of light-years beyond that. Given the immense distances involved and the finite speed of light, any signals or evidence of extraterrestrial life may simply have not yet traversed the vast expanses of space to reach our eager ears. Moreover, our search efforts have been relatively limited in both scope and duration, focusing primarily on a narrow range of frequencies and a minuscule fraction of the stars that populate the heavens.
Another critical factor to consider is the possibility that alien life may be fundamentally different from what we expect or can even comprehend. Our search for extraterrestrial intelligence (SETI) has largely been predicated on the assumption that alien civilizations would utilize radio waves or other electromagnetic signals for communication, mirroring our own technological development. However, it is entirely conceivable that advanced civilizations may have developed alternative technologies or communication methods that are currently beyond our understanding or detection capabilities. They may have transcended the need for physical communication altogether, or their signals may be so advanced that we simply lack the means to recognize or interpret them.
The ramifications of confirming the existence of extraterrestrial life are both profound and far-reaching, challenging our long-held assumptions about our place in the universe and the nature of life itself. The discovery of intelligent life beyond Earth would represent a watershed moment in human history, forcing us to reassess our understanding of the cosmos and our role within it. It could provide invaluable insights into the emergence and evolution of life, intelligence, and civilizations, opening up new avenues for scientific and philosophical exploration. The realization that we are not alone in the universe would fundamentally alter our perception of ourselves and our place in the grand tapestry of existence.
In recent years, the search for extraterrestrial life has intensified, with numerous scientific projects and initiatives dedicated to this monumental endeavor. The Breakthrough Listen project, for instance, is the most comprehensive and ambitious SETI program to date, employing cutting-edge telescopes and sophisticated data analysis techniques to survey a million nearby stars and a hundred nearby galaxies for signs of intelligent life. This groundbreaking project, backed by luminaries such as Stephen Hawking and funded by visionary entrepreneurs like Yuri Milner, represents a significant leap forward in our quest to answer the age-old question: Are we alone in the universe?
Other remarkable efforts, such as the Transiting Exoplanet Survey Satellite (TESS) and the James Webb Space Telescope (JWST), are revolutionizing our understanding of the cosmos and the potential for life beyond Earth. TESS, launched in 2018, is a state-of-the-art space telescope designed to identify and characterize potentially habitable exoplanets orbiting nearby stars. By observing the minute dips in a star's brightness as a planet transits across its face, TESS has already discovered thousands of exoplanets, some of which may harbor the necessary conditions for life to flourish. These tantalizing discoveries serve as prime targets for future SETI searches and more detailed observations by the JWST and other advanced telescopes.
The JWST, the long-awaited successor to the Hubble Space Telescope, promises to revolutionize our understanding of the universe and the search for extraterrestrial life. With its massive 6.5-meter primary mirror and suite of cutting-edge instruments, the JWST will be able to peer deeper into the cosmos than ever before, studying the atmospheres of distant exoplanets for signs of biosignatures – the telltale indicators of life. By analyzing the spectral fingerprints of these atmospheres, scientists hope to detect the presence of molecules such as oxygen, methane, and water vapor, which could suggest the presence of biological processes on these alien worlds. The JWST's unparalleled sensitivity and resolution will also allow it to study the formation and evolution of galaxies, stars, and planetary systems, providing crucial insights into the conditions that give rise to life in the universe.
As we continue to explore the cosmos and refine our search methods, the possibility of detecting extraterrestrial life grows ever more tantalizing. The next few decades promise to be a golden age of discovery, as new telescopes, space missions, and scientific collaborations push the boundaries of our knowledge and understanding. From the depths of our oceans to the furthest reaches of the universe, we are on the cusp of answering some of the most profound questions in the history of our species.
However, the search for extraterrestrial life is not without its challenges and controversies. Some scientists argue that the resources and funding allocated to SETI could be better spent on more pressing issues, such as climate change, poverty, and disease. Others contend that the potential risks of contact with alien civilizations, such as cultural contamination or even hostile invasion, outweigh the benefits of discovery. These concerns have led to heated debates within the scientific community and beyond, with some calling for strict protocols and safeguards to be put in place before any attempts at communication are made.
Despite these challenges, the allure of the unknown and the promise of discovery continue to drive the search for extraterrestrial life forward. The Fermi Paradox, with its perplexing contradiction between the high probability of alien life and the lack of evidence for its existence, serves as a constant reminder of the magnitude of the task before us. It is a challenge that will require the combined efforts of scientists, policymakers, and the public alike, as we grapple with the profound implications of our place in the universe.
As we stand on the threshold of a new era of cosmic exploration, it is important to remember that the search for extraterrestrial life is not just a scientific endeavor, but a deeply human one. It is a quest that speaks to our innate curiosity, our longing for connection, and our desire to understand our place in the grand scheme of things. Whether we are alone in the universe or part of a vast cosmic community, the answer to this question will undoubtedly shape the course of human history and our understanding of ourselves.
In the end, the Fermi Paradox and the search for extraterrestrial intelligence serve as a testament to the enduring human spirit of exploration and discovery. As we continue to peer into the depths of the cosmos, we do so with a sense of wonder, hope, and the unshakable belief that, somewhere out there, in the vast expanse of the universe, we may find the answers we seek. Whether we are alone or part of a cosmic community, the journey itself is one of the most profound and meaningful endeavors we can undertake.
As we embark on this grand adventure, we must remain open to the possibilities that lie ahead. We must be willing to challenge our assumptions, to embrace the unknown, and to adapt our theories and methods as new evidence emerges. The search for extraterrestrial life is not a destination, but a continuous process of learning, growth, and self-discovery.
It is a journey that will require patience, perseverance, and a deep commitment to the pursuit of knowledge. There will be setbacks and disappointments along the way, but each failure will bring us one step closer to the truth. We must not be discouraged by the vastness of the cosmos or the complexity of the task before us, but rather draw strength from the incredible progress we have already made and the limitless potential that lies ahead.
As we continue to search for signs of life beyond Earth, we must also reflect on the profound implications of our quest. The discovery of extraterrestrial intelligence would not only transform our understanding of the universe but also our understanding of ourselves. It would force us to reconsider our place in the cosmos, our relationship with other forms of life, and the very nature of existence itself.
Such a discovery would raise a host of new questions and challenges, from the practical concerns of communication and cultural exchange to the philosophical and ethical implications of contact. We must be prepared to grapple with these issues, to engage in open and honest dialogue, and to work together as a global community to navigate the uncharted waters ahead.
At the same time, we must also recognize that the search for extraterrestrial life is not just a scientific or technological endeavor, but a deeply human one. It is a reflection of our innate curiosity, our desire to explore and understand the world around us, and our longing for connection and meaning in an often uncertain and chaotic universe.
In this sense, the Fermi Paradox and the search for extraterrestrial intelligence are not just about finding life beyond Earth, but about understanding and appreciating the preciousness and fragility of life itself. They remind us of the incredible beauty and diversity of the universe, and the responsibility we have to protect and cherish it.
As we continue to explore the cosmos and push the boundaries of our knowledge, we must do so with a sense of humility, wonder, and respect for the mysteries that lie ahead. We must be willing to embrace the unknown, to learn from our mistakes, and to work together as a global community to build a better future for ourselves and for generations to come.
In the words of Carl Sagan, "The universe is a pretty big place. If it's just us, seems like an awful waste of space." The Fermi Paradox and the search for extraterrestrial intelligence remind us that we are part of something much greater than ourselves, a cosmic story that has been unfolding for billions of years and will continue to unfold long after we are gone.
It is a story that belongs to all of us, a legacy that we must cherish and protect. As we continue to search for signs of life beyond Earth, let us do so with a sense of purpose, compassion, and hope, knowing that the answers we seek may not only transform our understanding of the universe but also our understanding of ourselves and our place within it.
In the end, the Fermi Paradox and the search for extraterrestrial intelligence are a testament to the enduring human spirit of exploration, discovery, and the unquenchable thirst for knowledge. They remind us that, no matter how vast and mysterious the universe may be, we have the power to unlock its secrets and to shape our own destiny among the stars.
Questions:
1. The Fermi Paradox arises from the apparent contradiction between:
(A) The high probability of alien life and the lack of evidence for its existence
(B) The vast size of the universe and the limited scope of our search efforts
(C) The assumption that alien life would use radio waves for communication and the possibility of alternative technologies
(D) The rare Earth hypothesis and the idea that advanced civilizations may choose to remain hidden
2. The Drake Equation is used to estimate:
(A) The number of habitable planets in the universe
(B) The number of communicative civilizations in the galaxy
(C) The likelihood of intelligent life surviving long enough to develop advanced technologies
(D) All of the above
3. Which of the following is NOT a proposed solution to the Fermi Paradox?
(A) Alien civilizations may use communication methods beyond our current understanding
(B) Intelligent life may be extremely rare due to the specific conditions required for its emergence
(C) Advanced civilizations may deliberately choose to remain isolated or hidden
(D) The universe is too young for intelligent life to have evolved and spread across the cosmos
4. The Breakthrough Listen project is notable for:
(A) Being the most comprehensive SETI program to date
(B) Employing cutting-edge telescopes and data analysis techniques
(C) Surveying a million nearby stars and a hundred nearby galaxies for signs of intelligent life
(D) All of the above
5. The James Webb Space Telescope (JWST) is expected to revolutionize the search for extraterrestrial life by:
(A) Studying the atmospheres of distant exoplanets for signs of biosignatures
(B) Analyzing the spectral fingerprints of exoplanet atmospheres to detect molecules like oxygen and methane
(C) Providing insights into the conditions that give rise to life in the universe
(D) All of the above
6. Some scientists argue that the resources and funding allocated to SETI could be better spent on:
(A) Climate change research
(B) Poverty alleviation
(C) Disease prevention and treatment
(D) All of the above
7. The search for extraterrestrial life is driven by:
(A) Human curiosity and the desire to understand our place in the universe
(B) The potential for scientific and technological advancements
(C) The hope of finding new resources and habitable worlds
(D) All of the above
8. The discovery of extraterrestrial intelligence would likely:
(A) Transform our understanding of the universe and our place within it
(B) Raise new questions about communication, cultural exchange, and the ethics of contact
(C) Require global cooperation and dialogue to navigate the challenges and implications
(D) All of the above
9. The Fermi Paradox and the search for extraterrestrial intelligence remind us of:
(A) The incredible beauty, diversity, and mystery of the universe
(B) The responsibility we have to protect and cherish life in all its forms
(C) The potential for discovery and the importance of embracing the unknown
(D) All of the above
10. The enduring human spirit of exploration and discovery, as exemplified by the search for extraterrestrial life, is characterized by:
(A) A sense of wonder, purpose, and hope
(B) The willingness to challenge assumptions and adapt to new evidence
(C) The recognition that we are part of a greater cosmic story
(D) All of the above
3.RC
Mira variables, a subclass of asymptotic giant branch (AGB) stars, have long puzzled astronomers with their peculiar behavior and intricate evolutionary processes. Named after the prototype star Mira (omicron Ceti), these pulsating red giants exhibit a wide range of complex phenomena that challenge our understanding of stellar evolution. As stars enter the AGB phase, they undergo significant changes in their physical properties, pulsation periods, and mass-loss rates, providing a unique window into the final stages of a star's life.
One of the most striking features of Mira variables is their large-amplitude pulsations, which cause their brightness to vary by several magnitudes over periods ranging from 80 to more than 1,000 days. These pulsations are driven by the kappa-mechanism, a process in which the opacity of the star's outer layers varies due to the ionization and recombination of hydrogen and helium. As the star expands and cools, the opacity increases, trapping radiation and causing the star to pulsate. The pulsations can be so extreme that they cause the star's radius to change by up to 50% during each cycle, making Mira variables some of the largest and most dynamic stars in the universe.
The pulsations of Mira variables also play a crucial role in their mass-loss processes. As the star pulsates, shock waves propagate through its outer layers, lifting material from the surface and ejecting it into the surrounding space. This mass loss can be substantial, with rates ranging from 10^-7 to 10^-4 solar masses per year. Over time, the expelled material forms a circumstellar envelope around the star, which can extend to several hundred astronomical units and exhibit complex structures such as shells, arcs, and bipolar outflows. The interaction between the pulsations, mass loss, and circumstellar environment creates a fascinating feedback loop that shapes the evolution of these stars.
Another intriguing aspect of Mira variables is their chemical composition. As AGB stars, they have undergone significant nuclear processing, resulting in an enrichment of heavy elements such as carbon, oxygen, and s-process elements. The dredge-up processes, which occur during the thermal pulsing phase, bring these newly synthesized elements to the star's surface, altering its atmospheric composition and leading to the formation of molecules such as titanium oxide (TiO) and zirconium oxide (ZrO). These molecules are responsible for the deep absorption features observed in the spectra of Mira variables, providing valuable insights into the nucleosynthesis and chemical evolution of these stars.
The study of Mira variables has also revealed the existence of several subclasses with distinct properties. For example, the oxygen-rich Miras, characterized by the presence of oxygen-bearing molecules in their spectra, exhibit different pulsation characteristics and mass-loss rates compared to their carbon-rich counterparts. Similarly, the OH/IR stars, a subclass of oxygen-rich Miras with strong hydroxyl (OH) maser emission and infrared excess, are thought to represent a later evolutionary stage with even higher mass-loss rates. Understanding the diversity of Mira variables and their evolutionary connections is an ongoing challenge in stellar astrophysics.
The importance of Mira variables extends beyond their individual properties. As key contributors to the chemical enrichment of the interstellar medium, these stars play a vital role in the evolution of galaxies. The heavy elements expelled by Mira variables are incorporated into the next generation of stars and planets, shaping the composition of the universe over cosmic timescales. Moreover, the study of Mira variables has implications for our understanding of the late stages of stellar evolution, including the formation of planetary nebulae and the ultimate fate of low- and intermediate-mass stars.
Despite the significant progress made in understanding Mira variables, many questions remain unanswered. The complex interplay between pulsations, mass loss, and circumstellar environment is still not fully understood, and the mechanisms driving the observed diversity of Mira subclasses are the subject of ongoing research. The advent of new observational facilities, such as the James Webb Space Telescope (JWST) and the Atacama Large Millimeter/submillimeter Array (ALMA), promises to provide unprecedented insights into the physical processes governing these enigmatic stars.
1. The author's primary purpose in writing this passage is to:
(A) provide a comprehensive overview of the characteristics and evolutionary processes of Mira variables, highlighting their complexity and significance in stellar astrophysics
(B) argue for the importance of studying Mira variables in the context of galactic chemical evolution and the formation of planetary systems
(C) compare and contrast the properties of different subclasses of Mira variables, emphasizing the need for further research to understand their diversity
(D) critique the current state of knowledge about Mira variables and call for a revision of existing theories based on new observational evidence
(E) propose a novel hypothesis to explain the peculiar behavior of Mira variables and outline a research program to test this hypothesis
2. Based on the information provided in the passage, which of the following statements about the mass-loss processes in Mira variables can be inferred?
(A) The mass-loss rates of Mira variables are primarily determined by the star's initial mass and metallicity, with more massive and metal-rich stars experiencing higher rates of mass loss.
(B) The mass loss in Mira variables is a steady and continuous process, with material being ejected at a constant rate throughout the star's pulsation cycle.
(C) The circumstellar envelopes of Mira variables are composed mainly of hydrogen and helium, with only trace amounts of heavy elements produced by the star.
(D) The interaction between the star's pulsations, mass loss, and circumstellar environment likely creates a complex feedback loop that influences the star's evolution.
(E) The mass-loss processes in Mira variables are well-understood, with current models accurately predicting the observed mass-loss rates and circumstellar structures.
3. The passage suggests that the study of Mira variables is crucial for understanding which of the following aspects of stellar evolution?
(A) The formation and evolution of low-mass stars during their early stages on the main sequence
(B) The nucleosynthesis processes responsible for the production of light elements such as lithium and beryllium
(C) The mechanisms driving the high-energy phenomena observed in massive stars, such as stellar winds and supernova explosions
(D) The late stages of stellar evolution for low- and intermediate-mass stars, including the formation of planetary nebulae
(E) The processes governing the evolution of binary star systems and the exchange of mass between companion stars
4. Which of the following can be inferred about the chemical composition of Mira variables based on the information provided in the passage?
(A) Mira variables have chemical compositions similar to the Sun, with only minor enhancements in heavy elements.
(B) The chemical composition of Mira variables remains constant throughout their evolution, as the dredge-up processes do not significantly alter their surface abundances.
(C) Mira variables exhibit a wide range of chemical compositions, with some stars being highly enriched in carbon and others showing an overabundance of nitrogen.
(D) The atmospheric composition of Mira variables is characterized by the presence of molecules such as titanium oxide and zirconium oxide, which are formed as a result of the dredge-up of heavy elements.
(E) The chemical composition of Mira variables is dominated by the presence of radioactive elements, which are produced during the thermal pulsing phase and contribute to the star's high luminosity.
5. The passage implies that the pulsations of Mira variables play a significant role in:
(A) determining the star's surface temperature and luminosity variations
(B) triggering the nuclear fusion reactions responsible for the star's energy production
(C) the ejection of material from the star's surface and the formation of circumstellar envelopes
(D) the creation of magnetic fields and the generation of high-energy radiation
(E) the synchronization of the star's rotation and orbital periods in binary systems
6. According to the passage, which of the following observational facilities is expected to contribute significantly to our understanding of the physical processes governing Mira variables?
(A) The Hubble Space Telescope and the Chandra X-ray Observatory, which can provide high-resolution images and spectra of Mira variables across a wide range of wavelengths
(B) The James Webb Space Telescope and the Atacama Large Millimeter/submillimeter Array, which can probe the dusty circumstellar envelopes and molecular outflows of Mira variables
(C) The Sloan Digital Sky Survey and the Keck Telescope, which can conduct large-scale surveys of Mira variables and measure their distances and proper motions
(D) The European Southern Observatory's Very Large Telescope and the Gemini North Telescope, which can perform high-resolution spectroscopy and interferometry of Mira variables
(E) The Fermi Gamma-ray Space Telescope and the Swift Gamma-Ray Burst Explorer, which can detect the high-energy radiation emitted by Mira variables during their pulsation cycles
7. The passage suggests that the opacity variations in the outer layers of Mira variables are caused by:
(A) the ionization and recombination of heavy elements such as carbon, oxygen, and s-process elements
(B) the formation and dissociation of dust grains composed of silicates and graphite
(C) the absorption and emission of radiation by molecules such as titanium oxide and zirconium oxide
(D) the scattering and polarization of light by free electrons in the star's atmosphere
(E) the ionization and recombination of hydrogen and helium in the star's pulsating layers
8. Based on the information provided in the passage, which of the following statements about the evolutionary connections between different subclasses of Mira variables can be inferred?
(A) Oxygen-rich Miras evolve into carbon-rich Miras as a result of the dredge-up of newly synthesized carbon during the thermal pulsing phase.
(B) OH/IR stars represent a later evolutionary stage of oxygen-rich Miras, characterized by even higher mass-loss rates and more extended circumstellar envelopes.
(C) The evolutionary path of Mira variables is determined solely by their initial mass, with more massive stars evolving into carbon-rich Miras and less massive stars becoming oxygen-rich Miras.
(D) There is no clear evolutionary connection between different subclasses of Mira variables, as each subclass represents a distinct population of stars with unique properties.
(E) The evolutionary status of a Mira variable can be determined by the presence or absence of specific spectral features, such as the absorption lines of titanium oxide and zirconium oxide.
(A) The transit observation method is not suitable for detecting small, Earth-like planets.方法无关
(B) Planets orbiting distant stars have been found to have a wide range of orbital speeds.不确定是否有关
(C) The composition of planets in other solar systems is vastly different from those in our solar system. 不削弱，解释太阳系运转为什么满
(D) The transit observation method has only been used to study a small fraction of the known stars in the universe.削弱，攻击样本太少
(E) Larger planets are more likely to be detected by the transit observation method than smaller ones.无关
2C
Fact1: Silicon-based is possible
Fact2: Other factors are more critical in determining a planet's habitability than the abundance of any particular element.
Fact3: carbon-based life remains the most probable form of life in the universe
结论题
(A) The search for extraterrestrial life should focus exclusively on planets with high concentrations of carbon..不能推出
(B) Silicon-based life is more likely to exist than carbon-based life on planets with specific environmental conditions.不一定
(C) The abundance of an element is not the sole determining factor in the emergence of life on other planets.正确，Fact 2同义改写
(D) Liquid water is the single most important prerequisite for the development of life on any planet.跟Fact2冲突
(E) The majority of habitable planets in the universe are likely to host only carbon-based life forms.不能推出作者: fangjue987a 时间: 2024-6-24 22:15
1 A
2 D
3 D
4 D
5 C
6 B
7 E
8 B 作者: dreamer_11 时间: 2024-6-24 23:35
#lgg-cr-D156
1.B
削弱
P：所有行星都绕着恒星高速旋转，但在太阳系，围绕太阳转的大行星离太阳很远
C：在宇宙中，很少有行星像我们太阳系中的行星那样缓慢地围绕它们的恒星运行
C 被认为其他星球上的生物比过去认为的还要多。碳被认为是地外生物的基本因为其大量及稳定，研究人员提出其他的物质如硅也是生命在特定条件下的基础。认为液体水的存在是稳定的能量来源，以及一个保护性的大气是比任何元素更重要的因素在决定星球的可居性。然而，研究承认碳基生物保持最可能的生命形式在宇宙，其流行和多功能性