HR 8799 c

3. 궤도

HR 8799 c는 HR 8799에서 두 번째로 멀리 떨어진 행성이다. 궤도 긴반지름은 약 38AU 또는 42.9AU로, 태양계의 명왕성 궤도와 유사하다. 공전 주기는 약 224.9년 또는 231.7년으로, 현재까지 발견된 외계 행성 중 매우 긴 편에 속한다. HR 8799 b, c, HR 8799 d 행성은 4:2:1의 궤도 공명 관계를 가지고 있을 것으로 추정된다.^[20]

3. 1. 궤도 요소

4. 물리적 특성

HR 8799 c는 목성과 비교하여 직경은 1.2배에서 1.3배이지만, 질량은 7배에서 13배나 된다.^[19] 질량 상한은 갈색 왜성의 하한인 13배에 해당하며, 이로 인해 평균 밀도는 7.2g/cm³에 달한다.

HR 8799 c는 중심별인 HR 8799에서 멀리 떨어져 있지만, HR 8799가 태양보다 4.92배 밝고 행성계의 나이가 2000만 년에서 5000만 년^[21]으로 젊기 때문에^[18] 표면 온도는 약 820°C로 높다.^[19] 이 온도로 인해 적외선을 방출하며, 그 광도는 태양의 1만 분의 1 정도^[19], 약 7.7×10²¹W에 달한다. 하지만 겉보기 등급은 HR 8799의 10만 분의 1 이하로, 겉보기에는 어두운 적색을 띠는 것으로 추정된다.^[18]

초대형 망원경 VLT로 촬영된 HR 8799 c의 스펙트럼선은

4. 1. 대기 조성

참조

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_[2] 간행물 Images of a fourth planet orbiting HR 8799 2010
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_[40] 문서 시차로부터 계산한 것임: $\backslash scriptstyle\; \backslash mathrm\{distance\backslash \; in\backslash \; parsecs\}=\backslash frac\{1000\}\{\backslash mathrm\{parallax\backslash \; in\backslash \; milliarcseconds\}\}$
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_[44] 문서 Value given assuming the planet's orbit is circular and is being observed face-on.
_[45] SIMBAD SIMBAD 질의 결과.
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_[47] 뉴스 Gemini Releases Historic Discovery Image of Planetary First Family http://www.gemini.ed[...] Gemini Observatory 2008-11-13
_[48] 뉴스 Scientists Publish First Direct Images of Extrasolar Planets http://www.washingto[...] The Washington Post Company 2008-11-13
_[49] 저널 Stability of the directly imaged multiplanet system HR 8799: resonance and masses 2008-12-01