#comets : the Dirty Snowballs of #space

Comets are leftovers from the dawn of our solar system around 4.6 billion years ago, and consist mostly of ice coated with dark organic material. They have been referred to as "dirty snowballs." They may yield important clues about the formation of our solar system. Comets may have brought water and organic compounds, the building blocks of life, to the early Earth and other parts of the solar system.
According to NASA, the current number of known comets is: 3,743

WHERE DO COMETS COME FROM?
Comets obey the same laws of motion as the planets do, which means they travel around the Sun in elliptical orbits. The difference is that while the ellipses followed by the planets are roughly circular, the orbits of comets are far more elongated. As a consequence, while their closest approach to the Sun – called perihelion – may lie here in the inner Solar System, their most distant extreme, or aphelion, is much further away.
Unsurprisingly, the further out a comet’s aphelion is, the longer it takes to complete a single orbit around the Sun.
Among the well-studied comets, the one with the shortest period is Comet 2P/Encke, which completes an orbit in just under 3.3 years. It has its perihelion at 0.34 AU – where one AU, or astronomical unit, is the distance between Earth and the Sun – and an aphelion at 4.09 AU.
A more typical cometary orbit is that of Halley’s Comet. With a period of around 75 years, this has an aphelion of just over 35 AU, which is beyond the orbit of Neptune. This puts it in a region of the Solar System known as the Kuiper Belt, which is filled with small, icy comet-like objects – though only a minority of them have orbits that bring them anywhere near Earth.

#धूमकेतु या #पुच्छल तारे

धूमकेतु लगभग 4.6 अरब साल पहले हमारे सौर मंडल के निर्माण के दौरान के बचे हुए अंश हैं और ज्यादातर बर्फ से ढके काले कार्बनिक पदार्थों के रूप में पाए जाते हैं। उन्हें "डर्टी स्नोबॉल" के नाम से भी जाना जाता है। वे हमारे सौर मंडल के गठन के बारे में महत्वपूर्ण सुराग दे सकते हैं। हो सकता है कि धूमकेतु ही जीवन के निर्माण खंड पानी और कार्बनिक यौगिकों को पुरातन धरती पर लेकर आए होंगे।

#नासा के अनुसार, ज्ञात धूमकेतुओं की वर्तमान संख्या है: 3,743

धूमकेतु कहाँ से आते हैं?
धूमकेतु गति के उन्हीं नियमों का पालन करते हैं जिनसे कि सौर मंडल के तमाम ग्रह संचालित होते हैं, यानि वे भी अण्डाकार कक्षाओं में सूर्य की परिक्रमा करते हैं। अंतर यह है कि ग्रहों की दीर्घवृत्ताकार कक्षाएं मोटे तौर पर गोलाकार होती हैं, जबकि धूमकेतु की कक्षाएँ कहीं अधिक अण्डाकार होती हैं।

विजुअल जीके, विजुअलजीके, विजुअल जनरल नॉलेज
visual gk, VisualGK, visual general knowledge
www.visualgk.com

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