弾丸と小惑星の衝突によるダークマターのない銀河の痕跡
Pieter van Dokkum1, Zili Shen2, Michael A Keim2
1Department of Astronomy, Yale University, New Haven, CT, USA. pieter.vandokkum@yale.edu.
Nature
|May 18, 2022
まとめ
超拡散銀河DF2とDF4は おそらく80億年前の 単一の宇宙衝突で形成されました このイベントはダークマターのない銀河の軌跡を生み出し 銀河の形成の洞察を与えてくれます
科学分野:
- 銀河天文学
- 銀河の進化
- 宇宙学
背景:
- 超拡散銀河DF2とDF4は特異な特徴を示しています:大きな大きさ,豊富な超光球群,最小限の暗黒物質です.
- 過去の理論では 弾丸星団のような ガスに富んだ銀河の 高速衝突が 形成メカニズムとして提案されていました
研究 の 目的:
- 超拡散銀河DF2とDF4の形成仮説を調査する.
- これらの銀河が 単一の宇宙衝突で 誕生したかどうかを 判断するためです
主な方法:
- DF2とDF4の視界距離と放射速度の分析
- 関連する低明るさのオブジェクトの空間的分布と特性の検討.
主要な成果:
- 観測されたDF2とDF4の距離と速度は,およそ80億年前の"弾丸と小惑星"の衝突による共同形成を支持している.
- DF2とDF4は7〜11個の物体の線形構造の一部であり,2メガパーセックを超えるダークマターフリー銀河の軌跡を示唆しています.
- 軌道の先端にある 祖先の銀河のダークマター支配の残骸の 暫定的な特定
結論:
- DF2,DF4,および関連する銀河の形成の合理的な説明は,単一の"弾丸-矮星"衝突イベントです.
- この現象は 暗黒物質のない銀河の 独特の軌跡を生み出し 従来の銀河形成モデルに 異議を唱えました
- この発見は高エネルギー宇宙衝突によって 銀河の形成に関する新しい見方を示しています
関連する概念動画
01:10Detection of Black Holes
2.3K
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...
2.3K
01:21Schwarzschild Radius and Event Horizon
2.2K
No object with a finite mass can travel faster than the speed of light in a vacuum. This fact has an interesting consequence in the domain of extremely high gravitational fields.
The minimum speed required to launch a projectile from the surface of an object to which it is gravitationally bound so that it eventually escapes the object’s gravitational field is called the escape velocity. The escape velocity is independent of the mass of the object. Merging the idea of escape...
The minimum speed required to launch a projectile from the surface of an object to which it is gravitationally bound so that it eventually escapes the object’s gravitational field is called the escape velocity. The escape velocity is independent of the mass of the object. Merging the idea of escape...
2.2K
01:12Reduced Mass Coordinates: Isolated Two-body Problem
1.5K
In classical mechanics, the two-body problem is one of the fundamental problems describing the motion of two interacting bodies under gravity or any other central force. When considering the motion of two bodies, one of the most important concepts is the reduced mass coordinates, a quantity that allows the two-body problem to be solved like a single-body problem. In these circumstances, it is assumed that a single body with reduced mass revolves around another body fixed in a position with an...
1.5K
01:05Collisions in Multiple Dimensions: Introduction
5.6K
It is far more common for collisions to occur in two dimensions; that is, the initial velocity vectors are neither parallel nor antiparallel to each other. Let's see what complications arise from this. The first idea is that momentum is a vector. Like all vectors, it can be expressed as a sum of perpendicular components (usually, though not always, an x-component and a y-component, and a z-component if necessary). Thus, when the statement of conservation of momentum is written for a...
5.6K
01:15Elastic Collisions: Case Study
14.4K
Elastic collision of a system demands conservation of both momentum and kinetic energy. To solve problems involving one-dimensional elastic collisions between two objects, the equations for conservation of momentum and conservation of internal kinetic energy can be used. For the two objects, the sum of momentum before the collision equals the total momentum after the collision. An elastic collision conserves internal kinetic energy, and so the sum of kinetic energies before the collision equals...
14.4K
01:00Elastic Collisions: Introduction
13.2K
An elastic collision is one that conserves both internal kinetic energy and momentum. Internal kinetic energy is the sum of the kinetic energies of the objects in a system. Truly elastic collisions can only be achieved with subatomic particles, such as electrons striking nuclei. Macroscopic collisions can be very nearly, but not quite, elastic, as some kinetic energy is always converted into other forms of energy such as heat transfer due to friction and sound. An example of a nearly...
13.2K