Planets | Science for ACT PDF Download

Introduction

The journey began with a swirling mass of gas and dust. As the core of this cloud contracted, the Sun was born. Meanwhile, collisions among the surrounding matter gave rise to the formation of the eight planets. Among these, the inner planets, including Mercury, Venus, Earth, and Mars, are characterized by rocky surfaces. In contrast, the outer planets, known as gas giants, encompass Jupiter, Saturn, Uranus, and Neptune.

Mercury

• Mercury, lacking an atmosphere, appears heavily cratered, with a gray, rocky surface. Remarkably, a single day on Mercury is roughly equivalent to two Mercury years, completing two orbits around the Sun within one day.

Venus

• Venus, often referred to as the ‘morning star’ or ‘evening star,’ shines brightly in the night sky due to its dense cloud cover, which reflects a significant amount of sunlight. With an average temperature of 480°C, Venus experiences extreme heat, reaching levels where even lead would melt.

Earth

• Earth stands as the sole planet in the Solar System harboring liquid water on its surface, covering nearly three-quarters of its total area. Additionally, Earth's natural satellite, the Moon, influences tidal patterns and gradually slows the planet's rotation.

Mars

• Dubbed the ‘red planet’ due to its iron oxide-laden surface, Mars boasts Olympus Mons, the largest volcano in the Solar System, towering three times higher than Mount Everest.

Jupiter

• Jupiter, the largest planet in our system, dwarfs other celestial bodies with its massive size, capable of accommodating nearly 1,400 Earths within its boundaries. The Great Red Spot, a colossal storm system on Jupiter, has raged for over three centuries.

Saturn

• Saturn's captivating rings consist of spinning particles of rock and ice, some as large as houses. Interestingly, if a bathtub were colossal enough to hold the planets, Saturn would be the only one to float due to its low density.

Uranus

• Uranus possesses a unique characteristic of rotating on its side, potentially resulting from an ancient collision. Its distinct blue-green hue arises from the presence of methane in its atmosphere.

Neptune

• Neptune's atmospheric conditions foster the formation of diamonds, as methane-rich clouds can lead to diamond precipitation. Moreover, Neptune boasts the Solar System's swiftest winds, reaching speeds of up to 2,000 kilometers per hour.

The Pluto Predicament

• Pluto, discovered in 1930, has long intrigued astronomers as a peculiar member of our Solar System. Considerably smaller than traditional planets and even our Moon, Pluto follows an orbital path distinct from the eight major planets, periodically crossing above and below their plane.

The debate surrounding Pluto's planetary status gained momentum with the discovery of Trans-Neptunian Objects (TNOs) beyond Neptune's orbit. Notably, the detection of Eris, a TNO larger than Pluto and positioned farther from the Sun, spurred deliberations over Pluto's classification. In 2006, the International Astronomical Union (IAU) delineated specific criteria for planetary status, notably requiring a celestial object to orbit the Sun, exhibit spherical shape, and clear its orbital path of debris. Pluto failed to meet this last criterion, as it resides within the Kuiper Belt, teeming with other objects. Consequently, the IAU introduced the category of "dwarf planets," encompassing Pluto and others like Eris, Makemake, Haumea, and Ceres. These bodies share common traits with planets but have not entirely cleared their orbital vicinity. As the study of our Solar System continues, more dwarf planets may emerge, including Vesta and Pallas from the Asteroid Belt, and candidates like Varuna, Quaoar, Orcus, Ixion, and Sedna from the realm of TNOs.