为什么类木巨行星都位于太阳系外侧,而岩石行星集中在内侧?
Why do the gas giants all orbit beyond the inner solar system while rocky planets cluster inside it?
这源于原行星盘中的温度梯度:距离年轻太阳较近的区域温度高,只有金属和硅酸盐等耐熔物质能凝结成核,故形成了体积较小、密度较高的水星、金星、地球与火星。在雪线以外温度足够低,水冰、甲烷、氨等挥发物得以大量凝结,固体表面密度显著提高,使核心迅速增长到足以捕获氢氦包层的质量,最终演化为木星、土星、天王星与海王星这类气态或冰质巨行星。开普勒望远镜对系外行星系统的统计也表明,这一分布规律在其他恒星周围并非普遍成立,提示行星迁移过程同样重要。
It follows from the temperature gradient in the protoplanetary disk: close to the young Sun only refractory metals and silicates could condense into solid seeds, producing small dense worlds like Mercury, Venus, Earth, and Mars. Beyond the snow line, water, methane, and ammonia froze out in abundance, raising the surface density enough for cores to rapidly reach masses capable of capturing hydrogen-helium envelopes, yielding Jupiter, Saturn, Uranus, and Neptune. Exoplanet statistics from Kepler show this pattern is not universal around other stars, hinting that planetary migration also matters.
难度 进阶 · 适合 初中(12-15)
CC BY 4.0 · 已核验 · Verified 2026-08-23 · 2 条独立证据
来源 · Source
Carroll & Ostlie,《An Introduction to Modern Astrophysics》第2版,Cambridge University Press,2017
B. W. Carroll and D. A. Ostlie, An Introduction to Modern Astrophysics, 2nd ed., Cambridge University Press, 2017
独立核验依据 · Independent verification: 核验依据 2 ISBN 978-1-108-42216-1 (2nd ed., Cambridge Univ. Press)
#雪线 #原行星盘
太阳系行星为什么都大致在同一平面上、朝同一方向公转?
Why do the planets of the Solar System all orbit roughly in one plane and in the same direction?
约46亿年前,一团分子云坍缩形成原太阳,角动量守恒使周围物质摊成一个旋转的原行星盘。行星在这个盘中由尘埃与气体聚集而成,自然继承了盘的平面和旋转方向。金星逆向自转和天王星侧躺等例外,一般归因于后期大碰撞或潮汐作用,而非盘本身的性质。
About 4.6 billion years ago a molecular cloud collapsed to form the proto-Sun, and conservation of angular momentum spread the surrounding material into a rotating protoplanetary disk. The planets grew from dust and gas within this disk, so they inherited its plane and sense of rotation. Exceptions like Venus's retrograde spin and Uranus's tilted axis are usually attributed to later giant impacts or tidal effects rather than to the disk itself.
难度 进阶 · 适合 大众
CC BY 4.0 · 已核验 · Verified 2026-08-23 · 2 条独立证据
来源 · Source
苏宜,《天文学新概论》第5版,科学出版社
Su Yi, Introduction to Astronomy, 5th ed., Science Press
独立核验依据 · Independent verification: 核验依据 2 ISBN 9787030620477（豆瓣书目条目: 天文学新概论）
#太阳系形成 #原行星盘
太阳系大致是如何形成的？
How did the solar system roughly form?
约 46 亿年前一片分子云在引力下坍缩，中心形成太阳，周围盘中的尘埃和气体逐渐吸积成行星、卫星和小天体，这就是星云假说。
About 4.6 billion years ago a molecular cloud collapsed under gravity, forming the Sun at its center while dust and gas in the surrounding disk accreted into planets, moons, and small bodies—the nebular hypothesis.
难度 进阶 · 适合 大众
CC BY 4.0 · 已核验 · Verified 2026-08-23 · 2 条独立证据
来源 · Source
苏宜,《天文学新概论》第5版,科学出版社
Su Yi, Introduction to Astronomy, 5th ed., Science Press
独立核验依据 · Independent verification: 核验依据 2 ISBN 9787030620477（豆瓣书目条目: 天文学新概论）
#太阳系 #形成 #星云