Unit 1 - Science Literacy & Space
1.2 - Space
Day 5 - Due 10/3(A) & 10/4(B)
Introduction
Consider Earth, the Moon, and all the other planets and satellites in the solar system. The mass of all of those objects together accounts for only 0.2% of the total mass of the solar system. The rest, 99.8% of all the mass in the solar system, is the Sun!
The Sun (Figure below) is the center of the solar system and the largest object in the solar system. This nearby star provides light and heat and supports almost all life on Earth.
Consider Earth, the Moon, and all the other planets and satellites in the solar system. The mass of all of those objects together accounts for only 0.2% of the total mass of the solar system. The rest, 99.8% of all the mass in the solar system, is the Sun!
The Sun (Figure below) is the center of the solar system and the largest object in the solar system. This nearby star provides light and heat and supports almost all life on Earth.
Layers of the Sun
The Sun is a sphere, composed almost entirely of the elements hydrogen and helium. The Sun is not solid or a typical gas. Most atoms in the Sun exist as plasma, a fourth state of matter made up of superheated gas with a positive electrical charge.
Internal Structure
Because the Sun is not solid, it does not have a defined outer boundary. It does, however, have a definite internal structure with identifiable layers (Figure below). From inward to outward they are:
The Sun is a sphere, composed almost entirely of the elements hydrogen and helium. The Sun is not solid or a typical gas. Most atoms in the Sun exist as plasma, a fourth state of matter made up of superheated gas with a positive electrical charge.
Internal Structure
Because the Sun is not solid, it does not have a defined outer boundary. It does, however, have a definite internal structure with identifiable layers (Figure below). From inward to outward they are:
- The Sun’s central core is plasma with a temperature of around 27 millionoC. At such high temperatures hydrogen combines to form helium by nuclear fusion, a process that releases vast amounts of energy. This energy moves outward, towards the outer layers of the Sun.
- The radiative zone, just outside the core, has a temperature of about 7 millionoC. The energy released in the core travels extremely slowly through the radiative zone. A particle of light, called a photon, travels only a few millimeters before it hits another particle. The photon is absorbed and then released again. A photon may take as long as 50 million years to travel all the way through the radiative zone.
- In the convection zone, hot material from near the radiative zone rises, cools at the Sun’s surface, and then plunges back downward to the radiative zone. Convective movement helps to create solar flares and sunspots.
The Outer Layers
The next three layers make up the Sun’s atmosphere. Since there are no solid layers to any part of the Sun, these boundaries are fuzzy and indistinct.
- The photosphere is the visible surface of the Sun, the region that emits sunlight. The photosphere is relatively cool -- only about 6,700°C. The photosphere has several different colors; oranges, yellow and reds, giving it a grainy appearance.
- The chromosphere is a thin zone, about 2,000 km thick, that glows red as it is heated by energy from the photosphere (Figure below). Temperatures in the chromosphere range from about 4,000°C to about 10,000°C. Jets of gas fire up through the chromosphere at speeds up to 72,000 km per hour, reaching heights as high as 10,000 km
- The corona is the outermost plasma layer -- It is the Sun’s halo or ‘crown.’ The corona’s temperature of 2 to 5 million°C is much hotter than the photosphere (Figure below).
Surface Features
The Sun’s surface features are quite visible, but only with special equipment. For example, sunspots are only visible with special light-filtering lenses.
Sunspots
The most noticeable surface feature of the Sun are cooler, darker areas known as sunspots (Figure below). Sunspots are located where loops of the Sun’s magnetic field break through the surface and disrupt the smooth transfer of heat from lower layers of the Sun, making them cooler and darker and marked by intense magnetic activity. Sunspots usually occur in pairs. When a loop of the Sun’s magnetic field breaks through the surface, a sunspot is created where the loop comes out and where it goes back in again.
The Sun’s surface features are quite visible, but only with special equipment. For example, sunspots are only visible with special light-filtering lenses.
Sunspots
The most noticeable surface feature of the Sun are cooler, darker areas known as sunspots (Figure below). Sunspots are located where loops of the Sun’s magnetic field break through the surface and disrupt the smooth transfer of heat from lower layers of the Sun, making them cooler and darker and marked by intense magnetic activity. Sunspots usually occur in pairs. When a loop of the Sun’s magnetic field breaks through the surface, a sunspot is created where the loop comes out and where it goes back in again.
Solar Flares
There are other types of interruptions of the Sun's magnetic energy. If a loop of the sun's magnetic field snaps and breaks, it creates solar flares, which are violent explosions that release huge amounts of energy (Figure below).
There are other types of interruptions of the Sun's magnetic energy. If a loop of the sun's magnetic field snaps and breaks, it creates solar flares, which are violent explosions that release huge amounts of energy (Figure below).
A strong solar flare can turn into a coronal mass ejection (Figure below).
A solar flare or coronal mass ejection releases streams of highly energetic particles that make up the solar wind. The solar wind can be dangerous to spacecraft and astronauts because it sends out large amounts of radiation that can harm the human body. Solar flares have knocked out entire power grids and disturbed radio, satellite, and cell phone communications.
Solar Prominences
Another highly visible feature on the Sun is solar prominences. If plasma flows along a loop of the Sun’s magnetic field from sunspot to sunspot, it forms a glowing arch that reaches thousands of kilometers into the Sun’s atmosphere. Prominences can last for a day to several months. Prominences are also visible during a total solar eclipse.
Star Power
The Sun is Earth’s major source of energy, yet the planet only receives a small portion of its energy and the Sun is just an ordinary star. Many stars produce much more energy than the Sun. The energy source for all stars is nuclear fusion.
Nuclear Fusion
Stars are made mostly of hydrogen and helium, which are packed so densely in a star that in the star’s center the pressure is great enough to initiate nuclear fusion reactions. In a nuclear fusion reaction, the nuclei of two atoms combine to create a new atom. Most commonly, in the core of a star, two hydrogen atoms fuse to become a helium atom. Although nuclear fusion reactions require a lot of energy to get started, once they are going they produce enormous amounts of energy (Figure below).
Solar Prominences
Another highly visible feature on the Sun is solar prominences. If plasma flows along a loop of the Sun’s magnetic field from sunspot to sunspot, it forms a glowing arch that reaches thousands of kilometers into the Sun’s atmosphere. Prominences can last for a day to several months. Prominences are also visible during a total solar eclipse.
Star Power
The Sun is Earth’s major source of energy, yet the planet only receives a small portion of its energy and the Sun is just an ordinary star. Many stars produce much more energy than the Sun. The energy source for all stars is nuclear fusion.
Nuclear Fusion
Stars are made mostly of hydrogen and helium, which are packed so densely in a star that in the star’s center the pressure is great enough to initiate nuclear fusion reactions. In a nuclear fusion reaction, the nuclei of two atoms combine to create a new atom. Most commonly, in the core of a star, two hydrogen atoms fuse to become a helium atom. Although nuclear fusion reactions require a lot of energy to get started, once they are going they produce enormous amounts of energy (Figure below).
In a star, the energy from fusion reactions in the core pushes outward to balance the inward pull of gravity. This energy moves outward through the layers of the star until it finally reaches the star’s outer surface. The outer layer of the star glows brightly, sending the energy out into space as electromagnetic radiation, including visible light, heat, ultraviolet light, and radio waves (Figure below).
Questions:
1. In what way does the Sun support all life on Earth?
2. Which two elements make up the Sun almost in entirety?
3. Which process is the source of heat in the Sun and where does it take place?
4. What kind of reactions provide a star with energy?
5. Do you think fusion reactions in the Sun’s core will continue forever and go on with no end? Explain your answer.
6. Summarize the life cycle of a star (use the video from above)
1. In what way does the Sun support all life on Earth?
2. Which two elements make up the Sun almost in entirety?
3. Which process is the source of heat in the Sun and where does it take place?
4. What kind of reactions provide a star with energy?
5. Do you think fusion reactions in the Sun’s core will continue forever and go on with no end? Explain your answer.
6. Summarize the life cycle of a star (use the video from above)