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Most often, when people talk about which star is closest to Earth, they are referring to a star in a distant star system. In fact, the actual star closest to our planet is our own sun. The closest star to Earth after our sun is Proxima Centauri in the multiple-star system Alpha Centauri (in the southern hemisphere constellation of Centaurus - the Centaur), located approximately 38 trillion kms away. In contrast, our Sun is only about 149,000,000 kms away, and while light from the Alpha Centauri system takes a little more than four years to reach us, light from our Sun takes a mere 8.32 minutes.
The North American Space Agency (NASA) has just released images from the SolO (Solar Orbiter) spacecraft, a joint venture between NASA and the European Space Agency (ESA). This multi-instrument probe was launched in February of this year to study the sun. Through a series of elliptical orbits over the next 10 years, SolO will make 22 perihelion passes (its closest approach) around the sun. Already, while only halfway to its target, SolO has begun sending detailed pictures of the sun's outer atmosphere (referred to as the corona) and the sun's visible surface. These recently-received images, even at this early point in time, are providing solar scientists with a wealth of data about the sun, and the rest of us, with breath-taking, close-up pictures of our nearest star. Go to https://www.esa.int/ESA_Multimedia/Videos/2020/07/Closer_than_ever_Solar_Orbiter_s_first_views_of_the_Sun to look at these amazing photos; your concept of that bright ball of light in the daytime sky will be forever changed.
The sun is believed to have formed approximately five billion years ago from a vast cloud of nebulous dust and gas that existed in the early cosmos. As this cloud coalesced, it formed a spinning protostar, which, once it achieved sufficient mass, generated thermonuclear reactions within its core, shedding heat and light outward into the surrounding space. Eventually, planets formed from the remnants of the nebulous cloud disk that orbited around the newly-formed sun, resulting in our solar system. Fortunately for us, Planet Earth lies within the "Goldilock Zone" (remember your “Goldilocks and the Three Bears” bedtime story?), that region of space out from the sun which is neither too close (it would receive too much radiation, which would boil off any liquid water on the surface, thereby inhibiting the development of any potential lifeforms), nor too far (it wouldn't receive enough heat radiation to keep surface water in a liquid state, which most scientists deem a prerequisite for life, at least life as we currently know it).
A few interesting facts about our sun
So, the next time you are out under the sun, contemplate just how extraordinary a celestial object it is, and how lucky we are to be on the receiving end of its life-giving warmth and light; we owe our very existence to the sun. And remember, NEVER look directly at the sun, either with the naked-eye or, especially, with any optical instrument; even a few moments without the proper optical protection can result in significant and permanent eye damage, including the complete loss of sight. If you wish to see pictures of the sun, go online.
This week's sky
Jupiter (mag. -2.7) becomes visible in the late evening sky (shortly after 9 p.m.) about nine degrees above the southeast horizon. It is joined a short while later (around 9:30 p.m.) by Saturn (mag.+0.13) to its left. Both planets reach their highest points in the southern sky around midnight, before both disappear in the pre-dawn, south-west sky (Jupiter around 3:40 a.m., and Saturn around 4 a.m.). Mars (mag. -1.0) rises in the east shortly before midnight, reaching a height of 48 degrees above the southern horizon, before fading from sight as dawn breaks around 5:30 a.m. Venus (mag. -4.4) is visible in the pre-dawn, eastern sky around 2:40 a.m., reaching 26 degrees above the horizon before fading with the approaching dawn. Mercury (mag. -0.48) makes its appearance in the eastern, pre-dawn sky shortly after 4 a.m., reaching nine degrees above the horizon before fading from view around 5:20 a.m.
Keep watching for comet NEOWISE as it slides below the Big Dipper (in Ursa Major – the Great Bear) into the constellation of Coma Berenices in the north-west late evening sky in the coming week (use an on-line finder chart). Though fading in magnitude, the comet and its beautiful, long tail are readily visible in binoculars and scopes from a dark site away from city lights on any night the north-west sky is free of clouds. Try looking between 10-10:30 p.m. just as the sky darkens, and you can begin to see the stars. Make an effort to see this magnificent, once-in-a-lifetime comet, because it won't return for another 6,800 years.
Can't catch sight of any meteors? Watch overnight on July 28-29 as two meteor showers peak on the same night – the Delta Aquarids (radiant in Aquarius – the Water-Bearer) and the Alpha Capricornids (radiant in Capricornus – the Sea Goat). Go on-line to find out more about these two meteors showers. Also, keep an eye out for early Perseid meteors (radiant in Perseus - the Prince).
Until next week, clear skies.
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 firstname.lastname@example.org.