Glossary term: धूमकेतूचे वातावरण (कोमा)

Description: धूमकेतू सूर्याजवळ येताच धूमकेतूच्या बर्फाळ केंद्रकात बांधलेल्या घन पदार्थांचा काही भाग वायूमध्ये बदलतो. या वायूमध्ये मुख्यतः पाण्याचा समावेश असतो परंतु त्यामध्ये कार्बन मोनोऑक्साइड, कार्बन डायऑक्साइड, अमोनिया, मिथेन आणि मिथेनॉल यांसारखी इतर रसायने तसेच धुळीचे कण देखील असतात. हा वायू एका अस्पष्ट, गोलाकार ढगाप्रमाणे केंद्रकाभोवती असतो, ज्याला धूमकेतूचे वातावरण, किंवा कोमा म्हणतात. जसजसा धूमकेतू सूर्याच्या जवळ येतो, तसतसे अधिकाधिक रेणू सूर्याच्या अल्ट्राव्हायोलेट फोटॉन्सद्वारे विभाजित होतात, कोमा गरम करतात आणि त्याचे बाह्य भाग विस्तृत होतात. कालांतराने, बाहेरील आवरण आयनीकृत होतात, ज्यामुळे धूमकेतूची आयन शेपटी तयार होते.

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Term and definition status: The original definition of this term in English have been approved by a research astronomer and a teacher
The translation of this term and its definition is still awaiting approval

The OAE Multilingual Glossary is a project of the IAU Office of Astronomy for Education (OAE) in collaboration with the IAU Office of Astronomy Outreach (OAO). The terms and definitions were chosen, written and reviewed by a collective effort from the OAE, the OAE Centers and Nodes, the OAE National Astronomy Education Coordinators (NAECs) and other volunteers. You can find a full list of credits here. All glossary terms and their definitions are released under a Creative Commons CC BY-4.0 license and should be credited to "IAU OAE".

Related Media

A comet with two tails, one is yellowish and gradually spreading away from the nucleus, the other is blue and compact

Comet C/2020F3 (Neowise) with separate dust and ion gas tails and a green glowing coma, by Dietmar Gutermuth, Germany

Caption: Second place in the 2021 IAU OAE Astrophotography Contest, category Comets. Comets have a very interesting structure comprising of four main parts: the nucleus, composed of rock, dust and frozen gases, typically spanning a few kilometres, although bigger ones have been observed; a small atmosphere of gas surrounding the nucleus (only present when the comet approaches its closest point to the Sun), called coma; and the two distinctive cometary tails (there is at times third tail). The green colour of the coma is due to carbon and nitrogen present in the coma reacting with the Sun’s ultraviolet radiation. The tail that we are mostly used to observing – dust tail and is composed of micron sized dust particles, the second tail composed of charged particles – ion or gas tail. The tails are released only when the comet approaches the Sun at a distance where the heat and radiation emanating from our star is intense enough to vaporize the frozen gases. The dust tail is curved, while the gas tail is straight and always points away from the Sun as this is carried by the solar wind - flow of charged particles emitted by the Sun. As comets are formed by leftover material, they carry with them important information about the early stages of the Solar System’s formation. This beautiful image shows the comet C/2020 F3 (Neowise), as seen from Germany in July 2020, with three of the four structures clearly visible – coma, gas, and dust tail.
Credit: Dietmar Gutermuth/IAU OAE

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