ホワイト・ダワーフ・ステージ以前の恒星の角運動量喪失の地震的証拠
S Charpinet1, G Fontaine, P Brassard
1Laboratoire d'Astrophysique de Toulouse-Tarbes, Université de Toulouse, CNRS, 14 avenue E. Belin, 31400 Toulouse, France.
Nature
|September 26, 2009
まとめ
ほとんどの恒星の最終段階である白矮星は,急速に回転すると予想されていた. しかし,この研究では,白矮星が均一に回転することを発見し,これは恒星の進化の間に重要な角度運動量損失を示しています.
科学分野:
- 星の天体物理学 星の天体物理学
- ホワイト・ダワーフ進化
- アステロシズモロジーの地震学
背景:
- 白い矮星は,恒星の進化の95%の最終産物である.
- 理論的なモデルは,保存された角運動量による白矮星の急速な回転を予測しています.
- 観測データによると,白矮星は予想よりはるかにゆっくりと回転し,周期は数時間から数年に及ぶ.
研究 の 目的:
- 白い矮星の内部回転プロフィールを決定する.
- 白い矮星が内部に角度運動を蓄積できるかどうかを調査する.
- 恒星の進化過程における角運動量移転と損失の理論を検証する.
主な方法:
- 振動する白矮星 (PG 1159-035) の内部を探査するためにアステロ地震学を使用しました.
- 白い矮星の脈動モードを分析して,内部構造と回転を推論した.
主要な成果:
- 白い矮星PG 1159-035は,その質量の97.5%以上を占める固体体回転を示しています.
- 決定された回転周期は比較的長い: 33.61 +/- 0.59時間.
- これは,初期角運動量のほぼ完全な損失を示しています.
結論:
- 白い矮星は,形成前にまたは形成中に,本質的にすべての角度運動量を失います.
- この発見は,白矮星以前の進化段階における重要な角度運動量移転と損失を提唱する理論を支持する.
- 白い矮星の内部回転は,表面回転よりも著しく速くありません.
関連する概念動画
Conservation of Angular Momentum: Application
A system's total angular momentum remains constant if the net external torque acting on the system is zero. Examples of such systems include a freely spinning bicycle tire that slows over time due to torque arising from friction, or the slowing of Earth's rotation over millions of years due to frictional forces exerted on tidal deformations. However in the absence of a net external torque, the angular momentum remains conserved. The conservation of angular momentum principle requires a change...
Conservation of Angular Momentum
A system's total angular momentum remains constant if the net external torque acting on the system is zero. Considering a system that consists of n tiny particles, the angular momentum of any tiny particle may change, but the system's total angular momentum would remain constant. The principle of conservation of angular momentum only considers the net external torque acting on the system. While there are internal forces exerted by different particles within the system that also produce internal...
Angular Momentum
Angular momentum characterizes an object's rotational motion and is defined as the moment of its linear momentum about a specified point O. When a particle moves along a curved path in the x-y plane, the scalar formulation calculates the magnitude of its angular momentum, utilizing the moment arm (d), representing the perpendicular distance from point O to the line of action of the linear momentum. Despite being scalar in formulation, angular momentum is inherently a vector quantity. Its...
Detection of Black Holes
Although black holes were theoretically postulated in the 1920s, they remained outside the domain of observational astronomy until the 1970s.
Their closest cousins are neutron stars, which are composed almost entirely of neutrons packed against each other, making them extremely dense. A neutron star has the same mass as the Sun but its diameter is only a few kilometers. Therefore, the escape velocity from their surface is close to the speed of light.
Not until the 1960s, when the first neutron...
Their closest cousins are neutron stars, which are composed almost entirely of neutrons packed against each other, making them extremely dense. A neutron star has the same mass as the Sun but its diameter is only a few kilometers. Therefore, the escape velocity from their surface is close to the speed of light.
Not until the 1960s, when the first neutron...
Gyroscope: Precession
Precession can be demonstrated effectively through a spinning top. If a spinning top is placed on a flat surface near the surface of the Earth at a vertical angle and is not spinning, it will fall over due to the force of gravity producing a torque acting on its center of mass. However, if the top is spinning on its axis, it precesses about the vertical direction, rather than topple over due to this torque. Precessional motion is a combination of a steady circular motion of the axis and the...
Atomic Nuclei: Larmor Precession Frequency
The earth's gravitational field produces a 'twisting force' perpendicular to the angular momentum of a spinning mass (such as a spinning top) that causes the mass to 'wobble' around the gravitational field axis in a phenomenon called precession. Similarly, the magnetic moment (μ) of a spinning nucleus precesses due to an external magnetic field directed along the z-axis. The precession of the magnetic moment vector about the magnetic field is called Larmor precession, and the angular frequency...


