Question

In what direction do comet tails point? A) toward the Sun B) away from the Sun C) toward Earth D) away from the Oort Cloud

Short answer

B) away from the Sun

Step-by-step solution

Understanding the Nature of Comet Tails

Comets have two types of tails: the ion tail and the dust tail. These tails are formed due to the influence of the solar wind and radiation pressure from the Sun.

Solar Wind and Ion Tails

The solar wind is composed of charged particles emitted by the Sun. These particles exert a force on the comet's ion tail, pushing it directly away from the Sun.

Radiation Pressure and Dust Tails

Radiation from the Sun exerts pressure on the dust particles of the comet, also causing the dust tail to point away from the Sun.

Analyzing Options Based on Physics

Considering the effects of solar wind and radiation pressure, the tails of a comet always point away from the Sun, due to the pushing effect of both the solar wind and radiation.

Key concepts

Solar Wind

The solar wind is a stream of charged particles released from the upper atmosphere of the Sun, known as the corona. These charged particles are primarily electrons and protons. The solar wind travels throughout the solar system at high speeds, usually around 400 kilometers per second. This gusty solar breeze plays a crucial role in shaping the tails of comets.
The solar wind originated from the Sun's corona carries magnetic fields. When it interacts with a comet, it influences its ion tail by ionizing the gases in the comet's coma. This ionization process removes electrons from atoms, turning them into ions. The solar wind then sweeps these ions into space, forming a tail that always points directly away from the Sun.

• Composed of charged particles
• Originates from the Sun's corona
• Travels at speeds of about 400 km/s
• Shapes the ion tail of comets

Radiation Pressure

Radiation pressure is the force exerted by electromagnetic radiation from the Sun on objects in space, including comets. When the Sun shines, its light carries energy and momentum. Upon hitting the tiny dust particles in the comet's coma, the light transfers this momentum, pushing the particles away from the Sun.
This gentle but constant pressure creates the dust tail of the comet, which points away from the Sun, though it may be slightly curved because the grains of dust are ejected with different speeds and experiences the Sun’s gravity. Solar radiation pressure is unique because, unlike the solar wind, the force it exerts is a direct result of the photons from sunlight.

• Exerts force through electromagnetic radiation
• Affects tiny dust particles in the comet
• Causes dust tail to point away from the Sun
• Usually results in a slightly curved tail

Ion Tail

The ion tail of a comet is formed when the solar wind encounters and ionizes gases in the comet's coma. These ionized particles are extremely light and very sensitive to the Sun's magnetic field carried by the solar wind.
As the solar wind flows outward from the Sun, it carries these ionized particles with it, creating a long, straight tail of ionized gas that extends far into space. This tail will always be directed away from the Sun, often appearing as a bluish streak in the sky.

• Composed of ionized gases
• Straight and elongated in appearance
• Points directly away from the Sun
• Driven by the solar wind

Dust Tail

The dust tail of a comet is formed when solar radiation pressure pushes on the small particles of dust ejected from the comet's nucleus. These particles are not ionized like those in the ion tail.
The dust tail shimmers in sunlight, often showing a yellowish color because of its reflection of sunlight. Unlike the ion tail, the dust tail is broader and more curved due to the mixture of particle sizes and directions of ejection. Over time, the dust particles slowly drift away, following the comet's orbit around the Sun.

• Made of dust particles reflecting sunlight
• Broader and more curved than the ion tail
• Points generally away from the Sun
• Appears yellowish due to sunlight reflection