The Sun : Our nearest star

dictate

to give orders, or tell someone exactly what they must do, with total authority:

The UN will dictate the terms of troop withdrawal from the region.

mass

a large amount of something that has no particular shape or arrangement:

comet

A ball of frozen dust and rock that orbits the sun and has a tail that glows

asteroid

one of many large rocks that circle the sun

Concentration

a large number or amount of something in the same place:

habitability

the ability of the physical environment to support life

accompany

(v) to go with

The course books are accompanied by four CDs.

gravitational force

an attractive force that acts between any two objects

hazard

A danger or risk.

The busy traffic entrance was a hazard to pedestrians.

hazardous

dangerous

radiation

(n) a form of energy that comes from a nuclear reaction and that can be very dangerous to health:

sporadic

(adj) happening sometimes; not regular or continuous:

sporadic and violent space weather

lurk

to wait or move in a secret way so that you cannot be seen, especially because you are about to attack someone or do something wrong:

Someone was lurking in the shadows.

deduce

to reach an answer or a decision by thinking carefully about the known facts:

We cannot deduce very much from these figures.

density

the number of people or things in a place in relation to the size of the place:

The area has a high population density.

terrestrial

(Adj) relating to the earth

hydrogen

the Sun's fuel

helium

He

nuclear fusion

The process by which two or more small nuclei fuse to make a bigger nucleus

repulsion

the force in physics that pushes two objects apart:

magnetic repulsion

astronomer

A scientist who studies the stars and other objects in the sky

sustain

to cause or allow something to continue for a period of time:

He seems to find it difficult to sustain relationships with women.

molecule

the simplest unit of a chemical substance, usually a group of two or more atoms

atom

the smallest unit of any chemical element, consisting of a positive nucleus surrounded by negative electrons. Atoms can combine to form a molecule:

sufficient

(adj) enough for a particular purpose:

It was thought that he'd committed the crime but there wasn't sufficient evidence to convict him.

nebula

a cloud of gas and dust in space

eruption

a volcanic explosion or large flow of lava