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A world is a huge object that orbits a star. To be a planet, things must be huge enough for heaviness to have squeezed it right into a spherical, or round, shape,. It must likewise be big enough for gravity to have actually swept up any type of rocky or icy objects native its path, or orbit, approximately the star.Scientists think planets start to type when a thick cloud the dust and gas, referred to as a nebula, spins around a newly created star. Gradually, gravity causes the bits of issue in the nebula to clump together. Slowly, these clumps accumulate and grow. Eventually, these clumps end up being planets.Earth is one of eight planets the circle the star we call the sun. Together, the sun, the planets, and smaller objects such together moons make up our solar system.The 4 planets closest come the sun—Mercury, Venus, Earth, and also Mars—are dubbed terrestrial planets. These planets are solid and also rocky like earth (terra means “earth” in Latin). Earth is the biggest of the 4 terrestrial planets, and Mercury is the smallest. All room surrounded through a class of gas, or atmosphere. Their settings vary in thickness from Mercury’s very thin environment to Venus’, which is thick with clouds the sulfuric acid.The 4 planets the are much more distant from the sun—Jupiter, Saturn, Uranus, and Neptune—are dubbed gas giants. Gas giants are substantial compared with Earth, and they perform not have actually solid surfaces. They are big balls that gas. Jupiter and also Saturn are composed largely of hydrogen and helium. Uranus and Neptune have higher proportions that water vapor, ammonia, and also methane. Each of the four gas giants also has a ring system. A planet’s rings are made that ice, dust, and little rocks. Saturn’s ring mechanism is the largest.Every planet other than Mercury and Venus contends least one organic satellite, or moon. A planet’s moon orbits it together it revolves around the sun. Jupiter, Saturn, and Uranus each have actually dozens the moons.In addition to orbiting a star, planets likewise rotate, or spin, roughly an axis. An axis is one invisible line that runs through the facility of a planet. One complete rotation is referred to as a day. A day on earth is about 24 hours. A day on Jupiter takes just 9.8 hours. Venus has actually the longest day of any kind of planet in our solar system. That takes 243 planet days because that Venus to make a finish turn on its axis.Unlike stars, planets execute not endure nuclear fusion, the process of combining tiny particles dubbed atoms to relax energy. Nuclear combination creates radiation (heat and light) and makes stars glow. Due to the fact that planets do not have nuclear fusion, they do not develop their own light. Instead, lock shine through light reflect from a star. As soon as we watch planets in the night sky, such together Venus, the so-called "Evening Star," we"re seeing reflected sunlight.

You are watching: Objects revolving around and reflecting light from the sun

Exoplanets

Because there room trillions of stars in the universe, there are an extremely likely billions the planets. Yet until the beforehand 1990s, the only well-known planets were in ours solar system. Because then, however, scientists have discovered much more than 400 planets orbiting other stars. These are referred to as extrasolar planets, or exoplanets.Exoplanets appear to be fairly small native our approach on Earth. Telescopes normally cannot watch exoplanets directly, so astronomers have had to come up with techniques to recognize them. One an approach astronomers usage is to look because that a slim wobble in a star’s movement. This wobble is the an outcome of the gravitational traction of a surrounding planet. Many of the exoplanets found so far are gas giants.


Vocabulary

Term part of Speech an interpretation

accumulate

verb

to gather or collect.

ammonia

noun

a gas (NH3) crucial to food production.

ancient

adjective

very old.

astronomer

noun

person that studies an are and the universe past Earth"s atmosphere.

atmosphere

noun

layers that gases surrounding a world or various other celestial body.

atom

noun

the straightforward unit of an element, written of three significant parts: electrons, protons, and neutrons.

axis

noun

an invisible line around which an item spins.

billion

noun

1,000,000,000

day

noun

time it takes because that a world to finish a single rotation approximately its axis.

dense

adjective

having parts or molecules that space packed carefully together.

detect

verb

to notice.

distant

adjective

far away.

dozen

noun

a team of 12.

dust

noun

microscopic particles of rocks or minerals drifting in space. Additionally called cosmic dust or room dust.

dwarf planet

noun

celestial body the is virtually spherical however does not fulfill other definitions for a planet.

Earth

noun

our planet, the third from the Sun. The planet is the only location in the well-known universe the supports life.

earth

noun

soil or dirt.

energy

noun

capacity to execute work.

eventually

adverb

at some suggest in the future.

exoplanet

noun

planet exterior the solar system, orbiting a star various other than the sun. Likewise called one extrasolar planet.

extrasolar planet

noun

planet external the solar system, orbiting a star various other than the sun. Also called an exoplanet.

gas

noun

state of issue with no fixed shape that will certainly fill any kind of container uniformly. Gas molecules space in constant, random motion.

gas giant

noun

one the the four enormous outermost planets in the solar system (Jupiter, Saturn, Neptune, Uranus), composed mainly of gases rather of rock. Additionally called a Jovian planet.

gradually

adverb

slowly, or at a measure up pace.

gravitational pull

noun

physical attraction between two substantial objects.

gravity

noun

physical force through which objects attract, or traction toward, every other.

helium

noun

a light, colorless gas with the chemical symbol He.

hydrogen

noun

chemical aspect with the price H, who most typical isotope consists of a single electron and also a solitary proton.

International huge Union

noun

organization promoting and also safeguarding the scientific research of astronomy through international cooperation.

Jupiter

noun

largest planet in the solar system, the fifth planet native the Sun.

Latin

noun

language of old Rome and the roman inn Empire.

Mars

noun

fourth earth from the sun, between Earth and Jupiter.

matter

noun

material that provides up a substance.

Mercury

noun

smallest planet in the solar system, and also closest come the sun.

methane

noun

chemical compound the is the basic ingredient of organic gas.

Moon

noun

Earth"s only organic satellite.

moon

noun

natural satellite of a planet.

natural satellite

noun

moon, or a celestial body that orbits an additional celestial body (its primary).

nebula

noun

cloud of gas and dust in space.

Neptune

noun

eighth earth from the sun in ours solar system.

nuclear fusion

noun

process where the nuclei of one element, usually hydrogen, fuse through each other to kind the nuclei of an additional element, commonly helium.

orbit

verb

to move in a circular pattern roughly a an ext massive object.

planet

noun

large, spherical celestial human body that on regular basis rotates about a star.

Pluto

noun

dwarf world in ours solar system.

proportion

noun

amount.

radiation

noun

energy, emitted as waves or particles, radiating external from a source.

reflect

verb

to cant or return light from a surface.

revolve

verb

to orbit or spin around something.

ring system

noun

thin one of dust, gas, and rocks the orbit a planet.

rotate

verb

to turn roughly a center allude or axis.

Saturn

noun

sixth planet from the sun.

solar orbit

noun

revolution of an object around the sun.

solar system

noun

the sun and the planets, asteroids, comets, and also other bodies that orbit approximately it.

spherical

adjective

rounded and also three-dimensional.

star

noun

large round of gas and also plasma the radiates energy through nuclear fusion, such together the sun.

sulfuric acid

noun

toxic chemistry made the hydrogen, sulfur, and also oxygen.

sun

noun

star in ~ the center of our solar system.

telescope

noun

scientific tool that supplies mirrors come view distant objects.

See more: What Is The Half Life Of A Radioisotope If 25.0 Grams Of An Original 200 9

terrestrial planet

noun

one of the 4 planets closest to the sun: Mercury, Venus, Earth, or Mars.