Group V Luminous Objects

Luminous Objects are objects that give off their own light. To be able to glow, the object must have its own source of energy. For example a torch shines because it has power produced by the batteries. Whereas all stars shine using energy created by nuclear fusion in their cores. Both a torch and a star are considered to be luminous objects.

In order for us to see an object that is non-luminous, it must reflect some of the light it receives from a luminous source, such as the Sun. Most of the objects we see, such as cars, clouds or even the Moon, are not luminous; it is just that they reflect sunlight.


Luminous objects are measured in luminosity. The luminosity is how much energy is coming from the object per second. The units are watts (W). Astronomers often use another measure, absolute magnitude.

The luminosity of a star is a measure of its brightness. That's it. Simple. Astronomers measure a star's brightness by examining the amount of energy given off every second. The more energy given off, the higher the brightness. Scientists use Watts (W)to measure energy. Since our Sun is so close, scientists have measured about 390,000,000,000,000,000,000,000,000 Watts being given off all of the time. We need to remind you that not all of that energy is sent to Earth. Most of it is just sent out into space as heat and other EM radiation.

the moon refects light produced by the sun , because the moon is NOT a luminous object whereas the sun is. Luminous objects are responsible for our vision.
In complete darkness we cannot see/distinguish the different objects around us.
Human eye perceives the light reflecting from different objects to cause the sensation of vision.
In order to reflect (bounce back, come back) from different objects, we must make the light to fall on the objects.
Light is generated/emitted/produced/comes from only luminous objects. Thus luminous objects are responsible for our vision.
Example - Example: Lighted candle, torch bulb, the sun and stars.
In order to emit light, the object must have its own source of energy. A torch shines because of the chemical energy stored in its batteries, whereas all stars shine using energy created by nuclear fusion
Sun also emits light as a result of fusion of Hydrogen atoms. Hence they are considered as Luminous objects.

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