A celestial body refers to any naturally occurring object within the observable universe, encompassing entities such as stars, planets, satellites, and comets.
The moon:
One prominent example is the moon, Earth’s sole natural satellite and closest cosmic companion, situated approximately 400,000 km away. Despite being significantly smaller, with Earth being 81 times its size, the moon boasts a landscape marked by craters and towering mountains, some rivaling Earth’s peaks in height.
Phases of the moon:
Additionally, lacking an atmosphere, the moon undergoes varying phases, showcasing different shapes each day, a phenomenon known as the phases of the moon.
- New Moon: On the day of the new moon, the sky remains devoid of any visible lunar presence.
- Waxing Crescent: A few days after the new moon, a slender crescent shape starts to emerge, marking the waxing crescent phase.
- First Quarter: Approximately a week after the new moon, the moon displays a semicircular shape known as the first quarter moon.
- Waxing Gibbous: Around ten days after the new moon, the moon takes on the form of a circle with a portion seemingly sliced off, known as the waxing gibbous phase.
- Full Moon: Roughly fifteen days after the new moon, the moon shines forth in its entirety, forming a perfect circle, signalling the arrival of the full moon.
- Waning Phase: Following the waxing phase, the moon enters its waning phase. During this period, the full moon gradually diminishes in size, transitioning through the waning gibbous, third quarter, and waning crescent phases. After about 29 days from the new moon, the lunar cycle resets with the advent of the next new moon.
Reason for Phases of Moon:
The moon spins around and goes around the Earth at the same speed. This means it takes the same amount of time for the moon to spin once and to travel around the Earth. That’s why we always see the same side of the moon from Earth.
The moon doesn’t make its own light, it just reflects sunlight. So, we see the part of the moon that the sun is shining on. When the moon, Earth, and sun are lined up with Earth in the middle, we see the full moon. But when the moon is between Earth and the sun, we see the new moon, which looks dark because the sun’s light is hitting the side of the moon we can’t see.
The Star :
Exploring the Universe: A star, a colossal celestial entity, radiates both heat and light owing to its composition of scorching gases. Our closest star, the Sun, sits at a mere 150,000,000 kilometres away. Further out lies Alpha Centauri, distant by approximately 40,000,000,000,000 kilometres.
Illuminating Distances:
In the vast expanse of interstellar and intergalactic spaces, kilometres fail to suffice. Thus, the light year emerges as a more practical unit, denoting the distance light traverses in one year. For instance, sunlight takes a brief 8 minutes to journey from the Sun to Earth, marking the Sun’s proximity at 8 light minutes. Meanwhile, Alpha Centauri extends its reach across 4.3 light years.
Astronomical Milestones:
An astronomical unit (AU) represents the space between the Sun and Earth, simplifying planetary distance measurements relative to our star.
Ever wonder why stars vanish in daylight? The Sun’s brilliance overshadows them, akin to the glare from a car’s headlights obscuring our vision.
Celestial Choreography:
Observing the sky’s panorama reveals a common directional dance—all celestial bodies seemingly drift from east to west. This illusion stems from Earth’s west-to-east rotation, akin to viewing platform scenery from a moving train.
Pole star :
Amongst this celestial ballet, the Pole Star stands resolute. Anchored to Earth’s axis, it remains fixed in the northern sky—a guiding beacon for generations of sailors and travellers navigating through the night.
Thus, as the stars traverse their nightly paths, the Pole Star stands as a steadfast guide, a testament to the enduring partnership between humanity and the cosmos.
Constellation:
A constellation is a gathering of stars that forms a distinct shape or pattern. Humans possess an inherent knack for recognising patterns, allowing them to identify shapes and even faces in seemingly shapeless entities such as clouds or smoke. This innate ability has led to the recognition of various constellations. These celestial configurations may bear different names across different cultures. Among the well-known constellations are the twelve signs of the zodiac: Aries, Taurus, Gemini, Cancer, Leo, Virgo, Libra, Scorpio, Sagittarius, Capricorn, Aquarius, and Pisces. Additionally, there exist numerous other recognisable constellations like the Great Bear, Cassiopeia, Ursa Minor, and Orion.
Great Bear:
The Great Bear, also referred to as Ursa Major or the Big Dipper, stands as one of the most recognisable constellations in the night sky. Its distinctive shape resembles that of a ladle, making it easily identifiable to stargazers worldwide. Picture the night canvas, and within it, envision four stars forming the corners of a quadrilateral, crafting the bowl of the celestial ladle. The remaining trio of stars extends outward, defining the handle. This stellar arrangement graces the northern hemisphere, captivating observers with its prominence.
Notably, within the Great Bear lies a celestial alignment that enhances its allure. The final two stars of the quadrilateral align perfectly with the pole star, also known as Polaris. This alignment lends the impression that the Great Bear, with its seemingly perpetual motion, gracefully orbits around Polaris. Such a sight invokes a sense of cosmic dance, as if the celestial bear is perpetually circling its guiding star.
Contrastingly, Orion, dubbed the Hunter, presents a distinct celestial narrative. Its defining feature lies in three prominent stars forming a conspicuous belt, symbolising the hunter’s attire. Beyond the belt, an intricate arrangement of stars paints the picture of a figure wielding a club and shield, encapsulating the essence of the mythological hunter. Unlike the Great Bear, Orion graces the southern sky, offering a spectacle that is particularly prominent during the summer months in regions like India.
Both constellations, while distinct in appearance and mythology, share a common thread of captivating the human imagination. They serve as celestial markers, guiding our gaze across the vast expanse of the night sky and inspiring wonder and curiosity about the cosmos.
