A recent study has revealed that all the seven כוכבי לכת in the stellar system of TRAPPIST-1 have similar densities and Earth-like composition.This is significant because it builds the knowledge-base for a model of understanding of Earth-like כוכבי לכת outside of solar system.
כוכבים in the galaxies have stellar systems comprising mainly of their כוכבי לכת and satellites. For example, our home stellar system viz. solar system has nine כוכבי לכת (of varying densities, sizes and compositions) and their satellites. Mercury, Venus, Earth and מַאְדִים, הארבעה כוכבי לכת closet to Sun have rocky surfaces hence are referred to as terrestrial planets. On the other hand, Jupiter, Saturn, Uranus, Neptune are made of gases. The כוכב לכת Earth in the stellar system of Sun is unique in supporting life.
The quest for habitable worlds beyond Earth means search for habitable כוכבי לכת in the stellar systems of other כוכבים. There could be trillions of planets outside of the solar system. Such כוכבי לכת נקראים כוכבי לכת. Does any of the innumerable כוכבי לכת support life? Any such כוכב לכת can only be terrestrial one with hard rocky surface like Earth. Study of terrestrial כוכבי לכת therefore, is a very interesting area of study. The כוכב לכת community is an active research community in pursuit of identifying potential life-bearing worlds in the stars outside of the solar system.
The dwarf כוכב TRAPPIST-1 was discovered in 1999. This ultra-cool star is situated at a distance of 40 light years. In 2016, three כוכבי לכת were reported in the stellar system of this כוכב which was revised to seven subsequently in 2017. Three of the exoplanets are thought to be in habitable zone (1) .
The knowledge about these כוכבי לכת in the stellar system of TRAPPIST-1 is growing continuously. The earlier studies had revealed that these planets are roughly the size and mass of the Earth. This meant these כוכבי לכת have rocky surfaces hence Earth-like terrestrial planets. And, these are closely located in מסלולים in close proximity to the star. The latest finding reported is that all the planets are of similar densities and made of similar materials.
שימוש שטח and ground-based telescopes, the scientists have done a precise measurement of the transit times (the time taken by the planets to transit the star measured indirectly by dips in the brightness of the star when the planets cross in front of it) which enabled them refine the mass ratios of the planets to the star. Following this, they carried out photodynamical analysis and derived the densities of the star and the planets. This revealed that all the seven כוכבי לכת have similar densities and Earth-like composition possibly due to little less iron content than the Earth (2,3).
הפיתוח האחרון בהבנת הצפיפות וההרכב של כוכבי לכת in the stellar system of TRAPPIST-1 is significant because it builds the knowledge-base for a model of understanding of Earth-like כוכבי לכת outside of solar system.
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מקורות:
- נאס"א 2017. חדשות - טלסקופ נאס"א חושף את המקבץ הגדול ביותר של כוכבי לכת בגודל כדור הארץ, באזורים ראויים למגורים סביב כוכב בודד. פורסם ב-21 בפברואר 2017. זמין באינטרנט ב https://exoplanets.nasa.gov/news/1419/nasa-telescope-reveals-largest-batch-of-earth-size-habitable-zone-planets-around-single-star/ נגיש ב-25 בינואר 2021.
- נאס"א 2021. חדשות JPL - EXOPLANETS - 7 כוכבי הלכת הרוקי TRAPPIST-1 עשויים להיות עשויים מחומר דומים. פורסם ב-22 בינואר 2021. https://www.jpl.nasa.gov/news/the-7-rocky-trappist-1-planets-may-be-made-of-similar-stuff/
- Agol E., Dorn C., et al 2021. חידוד תזמון המעבר והניתוח הפוטומטרי של TRAPPIST-1: מסות, רדיוסים, צפיפות, דינמיקה ואפמרידים. The Planetary Science Journal, כרך 2, מספר 1. פורסם ב-2021, 22 בינואר. DOI: https://doi.org/10.3847/PSJ/abd022
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