एलआईएसए मिशन: अंतरिक्ष-आधारित गुरुत्वाकर्षण तरंग डिटेक्टर को ईएसए की मंजूरी मिल गई है 

The Laser Interferometer अंतरिक्ष Antenna (LISA) mission has received the go ahead of European अंतरिक्ष Agency (ESA). This paves the way for developing the instruments and spacecrafts commencing January 2025. The mission is led by ESA and is a result of collaboration between ESA, its Member State अंतरिक्ष एजेंसियों, नासा, and an international consortium of scientists.   

Scheduled to be launched in 2035, LISA will be the first अंतरिक्षआधारित गुरुत्वाकर्षण तरंग observatory dedicated to detection and study of millihertz ripples caused by distortions in the fabric of अंतरिक्ष-समय (गुरुत्वाकर्षण लहरों) के आर - पार ब्रम्हांड.  

Unlike the ground based गुरुत्वाकर्षण तरंग detectors (LIGO, VIRGO, KAGRA, and LIGO India) which detect गुरुत्वाकर्षण लहरों in frequency range of 10 Hz to 1000 Hz, LISA will be designed to detect गुरुत्वाकर्षण लहरों of much longer wavelengths in the low frequency range between 0.1 mHz and 1 Hz.  

अल्ट्रा-लो-फ़्रीक्वेंसी (10^-9- 10^-8 हर्ट्ज) गुरुत्वाकर्षण लहरों (GWs) with wavelengths from weeks to years from supermassive binary काला छेद can be detected using ground-based पल्सर टाइमिंग एरेज़ (पीटीए)). However, low frequency गुरुत्वाकर्षण लहरों (GWs) with frequency between 0.1 mHz and 1 Hz can neither be detected by LIGO nor by Pulsar Timing Arrays (PTAs) – the wavelength of these GWs is too long for LIGO and too short for PTAs to detect. Hence, the need for अंतरिक्ष-based GW detector.  

LISA will be a constellation of three spacecrafts in accurate equilateral triangle formation in space. Each side of the triangle will be 2.5 million km long. This formation (of the three spacecrafts) will कक्षा Sun in an Earth-trailing heliocentric कक्षा between 50 and 65 million km from Earth while maintaining a mean inter-spacecraft separation distance of 2.5 million km. This space-based configuration makes LISA an extremely large detector to study low frequency गुरुत्वाकर्षण लहरों that ground-based detectors can not.  

For detection of GWs, LISA will use pairs of test masses (solid gold-platinum cubes) free-floating in special chambers at the heart of each spacecraft. गुरुत्वीय ripples will make extremely small changes in the distances between test masses in the spacecrafts which will be measured through laser interferometry. As demonstrated by LISA Pathfinder mission, this technology is capable of measuring changes in distances to a few billionths of a millimetre. 

LISA will detect GWs caused by merger of supermassive काला छेद at the centre of galaxies thus will shed light on evolution of galaxies. The mission should also detect the predicted gravitational 'बजना' formed in the initial moments of the ब्रम्हांड in the first seconds after the big bang.  

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सन्दर्भ:  

1. ईएसए. समाचार-अंतरिक्ष समय की तरंगों को कैद करना: LISA को मंजूरी मिल गई। 25 जनवरी 2024 को पोस्ट किया गया। यहां उपलब्ध है https://www.esa.int/Science_Exploration/Space_Science/Capturing_the_ripples_of_spacetime_LISA_gets_go-ahead 

2. नासा. लिसा। उपलब्ध है https://lisa.nasa.gov/ 

3. Pau Amaro-Seoane et al. 2017. Laser Interferometer अंतरिक्ष Antenna. Preprint arXiv. DOI: https://doi.org/10.48550/arXiv.1702.00786  

4. Baker et al. 2019. The Laser Interferometer अंतरिक्ष Antenna: Unveiling the Millihertz Gravitational Wave Sky. Preprint arXiv. DOI: https://doi.org/10.48550/arXiv.1907.06482 

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