土星のダイナミックなリングの進化した眺め.
J N Cuzzi1, J A Burns, S Charnoz
1Ames Research Center, NASA, Mail Stop 245-3, Moffett Field, CA 94035-1000, USA. jeffrey.cuzzi@nasa.gov
Science (New York, N.Y.)
|March 20, 2010
まとめ
カッシーニ宇宙船の観測により,土星の環は主に水氷で,謎の汚染物質が含まれていることが明らかになった. 彼らの複雑な構造と急速な変化は,現在のモデルに異議を唱え,太陽系と比較して彼らの年齢を疑問視しています.
科学分野:
- 惑星科学は惑星科学である.
- 天文学 天文学
- 天体物理学 天体物理学
背景:
- 土星の環は主に水氷と未確認の赤色の汚染物質で構成されています.
- リング構造は複数の空間スケールにまたがり,粒子の相互作用とムーンレットの影響を受けます.
- いくつかのリングの特徴は,数日の間に急速な変化を示します.
研究 の 目的:
- カッシーニミッションの広範なデータに基づいて,土星のリングに関する現在の理解をレビューする.
- 環構造と進化における説明できない現象と複雑さを強調する.
- 土星のリングの年齢に関する潜在的影響を調査する.
主な方法:
- カッシーニ宇宙船からの約6年間の観測データの分析.
- 様々な空間・時間スケールにおけるリング構造の調査.
- 理論モデルと観測されたリングダイナミクスの比較.
主要な成果:
- カッシーニのデータは,水氷の組成を確認しているが,説明がつかない赤色の汚染物質を明らかにしている.
- 粒子,自己重力,月小惑星の複雑な相互作用により,リング構造が形成されます.
- リングの特徴の急速な時間的な変化が観察され,一部の変化は数日で起こります.
結論:
- 土星の環の構造と進化の重要な側面は,未だに解明されていない.
- 観測されたダイナミックなプロセスは,リングの年齢に関する仮定に異議を唱える可能性があります.
- 土星のリングは,周周円盤を研究するための貴重なアナログを提供します.
関連する概念動画
01:30Dynamics of Circular Motion
An object undergoing circular motion, like a race car, is accelerating because it is changing the direction of its velocity. This centrally directed acceleration is called centripetal acceleration. This acceleration acts along the radius of the curved path (thus is also referred to as radial acceleration).
Any acceleration must be produced by some force. Therefore, any force or combination of forces can cause centripetal acceleration. A few examples include the tension in the rope on a...
Any acceleration must be produced by some force. Therefore, any force or combination of forces can cause centripetal acceleration. A few examples include the tension in the rope on a...
02:15The Contractile Ring
Contractile rings are composed of microfilaments and are responsible for separating the daughter cells during cytokinesis. Contractile ring assembly proceeds along with other cell cycle events; however, very few mechanistic details are known about the timing and coordination of the contractile rings with the cell cycle.
A small GTPase, RhoA, controls the function and assembly of the contractile ring. RhoA belongs to the Ras superfamily of proteins. The activation of formins by RhoA promotes...
A small GTPase, RhoA, controls the function and assembly of the contractile ring. RhoA belongs to the Ras superfamily of proteins. The activation of formins by RhoA promotes...
02:15The Contractile Ring
Contractile rings are composed of microfilaments and are responsible for separating the daughter cells during cytokinesis. Contractile ring assembly proceeds along with other cell cycle events; however, very few mechanistic details are known about the timing and coordination of the contractile rings with the cell cycle.
A small GTPase, RhoA, controls the function and assembly of the contractile ring. RhoA belongs to the Ras superfamily of proteins. The activation of formins by RhoA promotes...
A small GTPase, RhoA, controls the function and assembly of the contractile ring. RhoA belongs to the Ras superfamily of proteins. The activation of formins by RhoA promotes...
01:16Circular Orbits and Critical Velocity for Satellites
The Moon orbits around the Earth. In turn, the Earth (and other planets) orbit the Sun. The space directly above our atmosphere is filled with artificial satellites in orbit. One can examine the circular orbit, the simplest kind of orbit, to understand the relationship between the speed and the period of planets and satellites with respect to their positions and the bodies that they orbit.
Nicolaus Copernicus (1473-1543) first suggested that the Earth and all other planets orbit the Sun in...
Nicolaus Copernicus (1473-1543) first suggested that the Earth and all other planets orbit the Sun in...
01:17Dynamics Of Circular Motion: Applications
Suppose a car moves on flat ground and turns to the left. The centripetal force causing the car to turn in a circular path is due to friction between the tires and the road. For this, a minimum coefficient of friction is needed, or the car will move in a larger-radius curve and leave the roadway. Let's now consider banked curves, where the slope of the road helps in negotiating the curve. The greater the angle of the curve, the faster one can take the curve. It is common for race tracks for...
01:10Kepler's First Law of Planetary Motion
In the early 17th century, German astronomer and mathematician Johannes Kepler postulated three laws for the motion of planets in the solar system. He formulated his first two laws based on the observations of his forebears, Nikolaus Copernicus and Tycho Brahe.
Polish astronomer Nikolaus Copernicus put forth a theory that stated a heliocentric model for the solar system. According to this heliocentric theory, all the planets, including Earth, orbit the Sun in circular orbits.
On the other hand,...
Polish astronomer Nikolaus Copernicus put forth a theory that stated a heliocentric model for the solar system. According to this heliocentric theory, all the planets, including Earth, orbit the Sun in circular orbits.
On the other hand,...