Earth’s nearest star Glenn Roberts Atlantic Skies
A number of my readers have sent me queries as to which is the closest star to Earth. Surprisingly, they didn’t seem to know or understand that our sun is, in fact, a star, and, as such, is the closest star to Earth. The actual term “sun” likely originated with the Old English word “sunne,” itself from old German. Since the light and heat of the sun is so important to life on Earth, it is not surprising that it was held in great reverence, and featured so prominently in the cultures of many ancient peoples throughout history, symbolizing the “circle of life and death” on a daily and annual basis. To the ancient Greeks, the sun was the god “Helios,” son of the Titan Hyperion and the Titaness Theia, who drove his flaming chariot, drawn by fire-breathing horses, across the heavens at the start of each day. Though Helios was associated by many with Apollo, the God of Light, most ancient Greeks saw them as separate deities. The Romans replaced the Greek name Helios with the Latin “Sol,” a word still used today. The term “solar system” is a direct link to our planetary system’s relationship to “Sol.” To the ancient Phoenicians, the sun was Melkarath, sun-god of spring and the harvest. The ancient Persians worshipped the sun as Mithras, their supreme deity. The Egyptians worshipped the sun by a variety of names, based on its numerous aspects — as Osiris (“the one who sees clearly”), represented by the setting sun; as Ra, the omnipotent god of the midday sun, who crossed the sky in a magnificent boat and who came to symbolize the power of Egypt’s noble pharaohs; and as Amum, personification of the sun after it had set and was hidden from view. The Meso-American empires of the Aztecs and Mayans associated the sun with kingship, with their rulers claiming divine right by direct descendancy from the sun. Native North American peoples included sun symbols in their artwork. As recently as the mid-1800s, the Plains tribes of the western United States annually celebrated the bond between man and the natural world through a Sun Dance. Though the sun is no longer formally worshipped by any established national religion, many people around the world still informally honour the sun’s return with midsummer festivals and summer solstice celebrations, the most famous of which takes place annually at Stonehenge in England. Prior to the late 16th century, the established belief was that the universe, including the sun, revolved around the Earth, a theory known as the “geocentric (Earth-centred) model,” primarily based on the writings and teachings of the ancient fourth-century Greeks Plato and Aristotle. It wasn’t until the 16th century that the astronomers Nicholas Copernicus, Johannes Kepler, and Galileo Galilei were able to disprove this theory and put forth the correct one, demonstrating that the planets revolve around the sun, known today as the “heliocentric (sun-centred) model.” Our sun is actually a rather mediocre star, classified as a G2, main-sequence star, at an average distance of approximately 148 million kilometres from Earth. Though it appears massive to us, it’s not a large star compared to other stars in the known universe, many of which are hundreds to thousands of times larger and more massive than our Sol. The sun is composed of approximately 74 per cent hydrogen, 24 per cent helium, one per cent oxygen and a one per cent mixture of carbon, nitrogen, silicon, magnesium, iron, sulphur and neon. It is believed to have formed approximately 4.6 billion years ago from a huge cloud of molecular gas and dust that gravitationally coalesced into a massive ball, where extreme pressure caused a nuclear fission reaction, converting hydrogen into helium and giving off large amounts of energy, which reaches our planet as heat and light. By all estimates, the sun’s fission reaction will continue for about another three billion to five billion years, after which time, when its hydrogen supply has been depleted, an imbalance of remaining elements, heat, gravity and radiation will cause the sun to swell in size to become a red giant star, encompassing the inner planets, including Earth, in the process, before eventually collapsing into a white dwarf star. We needn’t worry about it, though, for should humankind still exist, we will have, hopefully, moved on to another part of the universe long before the swelling star destroys planet Earth.
IN THE NIGHT SKY
Mercury (magnitude -0.6) should, weather permitting, still be visible low above the southwest horizon at dusk. Venus (magnitude -4.12) will be visible higher in the southwestern sky around 6 p.m., before disappearing below the western horizon around 9:30 p.m. Mars (magnitude -1.5) can be found in the pre-dawn southeastern sky by 4 a.m., before fading from view as the eastern sky lightens around 6:30 a.m. Jupiter (magnitude -1.9) is a late riser, not showing up in the pre-dawn southeastern sky until shortly after 5 a.m. Saturn just manages to peek above the southeastern horizon about an hour before sunrise. Until next time, clear skies. Feb. 23 — New Moon Glenn K. Roberts lives in Stratford, P.E.I., and has been an avid amateur astronomer since he was a small child. He welcomes comments from readers, and anyone who would like to do so is encouraged to email him at glennkroberts@gmail.com.