This evening, gloriously bruised skies created a twilight ponder. Twilight struck with realization most of us take her mesmerizing palette for granted. Far from a cosmic constant, twilight requires atmosphere to scatter rays of light in advance and conclusion of a visible Sun above the horizon.
Civil twilight falls when the sun is 6 degrees below the horizon. In the morning this is known as dawn, in the evening, dusk. This is the limit at which twilight illumination is sufficient, under good weather conditions, for terrestrial objects to be clearly distinguished; at the beginning of morning civil twilight, or end of evening civil twilight, the horizon is clearly defined and the brightest stars are visible under good atmospheric conditions in the absence of moonlight or other illumination. In the morning before the beginning of civil twilight and in the evening after the end of civil twilight, artificial illumination is normally required to carry on ordinary outdoor activities.
Nautical twilight begins when the Sun is 12 degrees below the horizon. At the beginning or end of nautical twilight, under good atmospheric conditions and in the absence of other illumination, general outlines of ground objects may be distinguishable, but detailed outdoor operations are not possible, and the horizon is indistinct.
Astronomical twilight defines a Sun 18 degrees below the horizon. Before the beginning of astronomical twilight in the morning and after the end of astronomical twilight in the evening the Sun does not contribute to sky illumination; for a considerable interval after the beginning of morning twilight and before the end of evening twilight, sky illumination is so faint that it is practically imperceptible.
Civil, nautical, astronomical, three clearly defined twilights that forgot to mention – twilight is also a colour, emotion and source of cosmic wonder unique to our planet.
Trust me when I say the International Astronomical Union (IAU) https://www.space.com/29696-international-astronomical-union.html rarely engages the public in astronomical matters. Truth is IAU arrogance rubs many a scientist the wrong way. IAU members have sole authority and discretion in naming astronomical objects and features, but for a stroke of IAU pen Pluto would still call itself planet. Cosmic nomenclature isn’t official until the IAU says so.
In summer 2018 science discovered twelve unknown moons of Jupiter, now the IAU wants help in naming five. Anyone can submit entries, but guidelines are strict. In keeping with Jovian propriety moons of Jupiter are named for characters in Greek or Roman mythology either descended from or lovers of Zeus. Ponder this before referencing ancient mythology – not all moons orbit Jupiter in the same direction. Those orbiting in the same direction (in this case 2 out of 5) require names ending in “a”, opposite rotation require names ending in “e”. Submissions can’t be similar to other cosmic bodies/features or be culturally offensive.
Anyone up for the challenge has until April 15, 2019 to submit nominations and explain why in a single tweet to @JupiterLunacy tagged #NameJupitersMoons.
Its been a while since space weather graced this blog, far too long if you ask me. With that in mind, ponder a Sunday night space weather update.
As I write solar wind blows at 354.8 km/second, 1,967 potentially hazardous asteroids are identified within 100 LD (lunar distance) from our planet and 2 observable fireballs have been recorded in the past 24 hours. Despite a lull in solar activity courtesy cyclical expectations of solar minimum, a behemoth Earth facing hole in the Sun’s surface catapults solar wind in our direction. Contact with Earth’s magnetic field is anticipated on February 19 or 20th. Aurora watchers can expect geomagnetic storms.
On Monday February 18, Sirius, the brightest star in our night sky will be eclipsed by asteroid 4388 Jurgenstock (https://en.wikipedia.org/wiki/4388_Jürgenstock)
In sharp contrast to February 2018 which came and went without a full moon, February 19, 2018 delivers a supermoon designated the closest full moon of the year.
Few people know what space weather is, let alone grasp how it impacts life on Earth. If you were a passenger on NetJets flight 795 from White Plains to Burbank last week, you received a radiation dose of x 68.4 that of radiation exposure at sea level. Space weather is real and it matters. Happy Sunday.
On February 12/13, 2019 comet Iwamoto makes a rare visit to our corner of the universe. Discovered in 2018 by amateur Japanese astronomer Massayuki Iwamoto, his namesake passes harmlessly at a distance of 45 million km. with astronomical magnitude of +6.5 – too faint for the human eye, easily observed by backyard telescopes. With a wonky elliptical orbit of 1,371 years, comet Iwamoto hasn’t said hello since 648 AD and won’t be back until the year 3390. Point your telescope toward constellation Leo around midnight on the 12th to catch a glimpse of Iwamoto.
Comet Iwamoto (C/2018 Y1) hails from beyond the Kuiper Belt. Officially this Extreme Trans-Neptunian Object (ETNOs) comes from a distance 5 times greater than that of Pluto to the Sun. Regarded as a “dirty snowball” –
“The most popular theory about the nature of comets was put forward by American astronomer Fred Whipple, often known as the “grandfather” of modern cometary science. Whipple believed they were like dirty snowballs – large chunks of water ice and dust mixed with ammonia, methane and carbon dioxide. As the snowball approached the Sun, its outer ices began to vapourise, releasing large amounts of dust and gas which formed the characteristic tails.
Today, largely thanks to data from Giotto and the Russian Vega spacecraft, we now know that Whipple’s model was fairly accurate. A comet nucleus resembles a fluffy snowball (usually only a few kilometres across) coated with a crust of black material and spouting jets of vaporised ice.”
Only a handful of keeners will witness Iwamoto’s passing. Seeing it matters less than knowing it’s out there and tipping your hat to cosmic wonder.
Tonight through August 13 the Perseid meteor shower promises to deliver peak sightings. According to science – “In 1835, Adolphe Quetelet identified the shower as emanating from the constellation Perseus. In 1866, after the perihelion passage of Swift-Tuttle in 1862, the Italian astronomer Giovanni Virginio Schiaparelli discovered the link between meteor showers and comets.“. Seems over zealous astronomers neglected to ask the church were Perseid originated.
Martyred Christian deacon Saint Lawrence was put to death August 10, 258 AD by Roman emperor Valerian. According to legend Lawrence was grilled to death over hot coals. Before succumbing to his death deacon Lawrence is said to have told his torturers he was “done” on one side and to turn him over. ( reason National Geographic claims made Lawrence the patron saint of chefs ) History documents Catholic observance of Saint Lawrence martyrdom on August 10 since the fourth century.
Somewhere in the annuals of early Catholic history Perseids became the fiery tears of Saint Lawrence. Clearly the only explanation for a annual event coinciding with grilling the patron saint of chefs.
A Perseid meteor crosses the night sky over a statue of Jesus Christ in a Belarusian village on August 13, 2016. https://www.nationalgeographic.com/science/2018/08/news-perseid-meteor-lawrence-christianity/
Go to https://www.space.com/32868-perseid-meteor-shower-guide.html for tips on watching Perseid.
Sunday night Hubble – no need for words….