ATLANTIC SKY: Our strange solar system (part 1): the strange planet


As in any family, there are always a few quirky parents who somehow just don’t fit in or, for some reason, parade to the beat of a different drum. This is also the case with our solar system family members; while most, at least at first glance, appear to be fairly normal (apart from the usual family variations in size, shape and orientation), but, on closer inspection, reveal some very interesting deviations from the family line.

Let’s start with the Earth, our home planet, which, with justifiable prejudices, we consider to be the perfect planet. Located just the right distance (golden loop) from the Sun (1 AU or 150 million kilometers), it has abundant liquid water in the form of many oceans, lakes and rivers, and an atmosphere made up of just the correct percentages of oxygen, hydrogen, helium, etc. to support life. Its stable and slightly elliptical orbit around the Sun allows the seasons which, with variable weather cycles, enrich the globe with abundant flora and fauna.

Mercury, the smallest member of our solar system, is the closest planet to the Sun (an average of 0.4 AU or 58 million kilometers). However, despite daytime surface temperatures approaching 430 ° C, Mercury actually has areas of surface and subterranean ice (water ice) hidden in perpetually shaded portions of craters at its north and south poles. NASA’s MESSENGER probe, using its spectrometer, discovered ice, estimated in places to be several meters thick, and totaling around 100 billion to 1,000 billion tonnes. This water ice is believed to have arrived on Mercury (and other planets in the inner solar system, including Earth), via water-rich comets and asteroids. Venus, the second planet from the Sun, is sometimes referred to as the evening star (if in the western sky) or the morning star (if in the eastern sky) due to its extreme brightness, which varies between -3.8 and -4.8 magnitude (bright enough to cast shadows), due to the high reflectivity of the planet’s thick cloud cover. It is the hottest planet in our solar system, with temperatures exceeding 470 ° C, again due to the thick clouds (carbon dioxide with small amounts of sulfuric acid) that cover the entire planet. and trap all heat. Venus is the odd family member who dances to her own tune, turning backwards (retrograde) towards the other planets. It also spins very slowly, with 1 Venusian day equaling 243 Earth days (which is longer than the 225 days it takes for Venus to orbit the Sun).

It is believed that Mars, the red planet, also once had an atmosphere and surface temperatures that allowed for abundant surface water. The loss of the planet’s magnetic field, coupled with the Sun’s removal of lighter forms of hydrogen from the atmosphere, caused the planet’s atmosphere to dissipate into space over a period of billions of years. ‘years. With the loss of its atmosphere, the waters of the planet quickly evaporated, leaving the arid world we see now. However, like Mercury, recent space probes have revealed the presence of patches of water ice on the surface and below the surface in the polar regions. Mars has the distinction of having the highest volcano (25 kilometers) and the largest (a diameter equal to that of the state of Arizona) – Olympus Mons – of all the planets in the solar system. In addition, it has the deepest (up to 7 kilometers) and longest (comprising 20% ​​of the diameter of Mars) canyon – Valles Marineris – of all the planets in our solar system. Next week, we’ll take a look at the largest and most distant planets in our solar system – the gas giants Jupiter and Saturn, and the ice giants Uranus and Neptune. We’ll even take a look at Pluto, our ancient ninth planet.

Mercury (mag. -0.8, in Virgo – Virgo) is visible in the dawn sky around 6:20 a.m. ADT (6:50 a.m. NDT), reaching 10 degrees above the eastern horizon before disappearing as dawn breaks around 7:30 a.m. ADT (8 a.m. NDT). Venus (mag -4.4, to Ophiuchus – the serpent bearer) becomes visible around 6:20 p.m. ADT (6:50 p.m. NDT), 10 degrees above the southwest horizon as night falls , before sinking towards the horizon and setting shortly after 8 p.m. ADT (8:30 p.m. NDT). Mars, too close to the Sun, is not visible. Jupiter (mag. -2.5, in Capricorn – the Sea Goat) is visible in the evening twilight, 23 degrees above the southeast horizon around 6:20 p.m. ADT (6:50 p.m. NDT), reaching an altitude of 28 degrees above the south horizon at around 8:10 p.m. ADT (8:40 p.m. NDT) and remaining visible until about 12:10 a.m. ADT (12:40 a.m. NDT), when it descends below 7 degrees above above the southwest horizon. Saturn (mag +0.6, in Capricorn) becomes visible in the southern sky in the early evening around 6:35 p.m. ADT (7:05 p.m. NDT), 24 degrees above the horizon, remaining visible until approximately 10:20 p.m. ADT (10:50 p.m. NDT), when descending below 10 degrees above the southwest horizon.

Correction: Last week’s article contained a typo: 1 AU equals 150 million kilometers, not 1,500 million kilometers. My excuses.

Until next week, clear skies.


  • November 3: Mercury south of the Moon
  • November 4: New Moon
  • November 4-5: Moon at perigee (closest to Earth)
  • – South Taurid meteor shower peak (after midnight)

(Glenn K. Roberts lives in Stratford, PEI, and has been an avid amateur astronomer since he was little. He appreciates comments from readers of [email protected].)

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