~Taigne Hammock
PART ONE: The Perseids Meteor Shower

This week the Perseids meteor shower is projected to peak the night of August 12 and early morning August 13, displaying at a rate of up to 50-60 meteors per hour. Although the waning “super” moon will be bright and prominent in the night sky, observers should still be able to spot some meteors. Best to find a spot away from ground light to help with visibility.

The Perseid meteor shower occurs as the Earth passes through the debris left by the comet Swift-Tuttle, which orbits the Sun roughly once every 133 years; the comet’s last perihelion was in December 1992, and is projected to complete its orbit again in July of 2126. Predicting a meteor’s exact return can be tricky, due to the high eccentricity of orbit and very long orbit period. Prior to its approach in 1992, comet Swift-Tuttle had been predicted to have an orbit period of roughly 120 years; its return in 1992 was nearly ten years later than predicted!

Speaking of comets, this past week (August 6) the European Space Agency’s Rosetta spacecraft made final maneuvers to put it in-line with reaching comet 67P/Churyumov-Gerasimenko in November of this year. The mission has taken more than ten years, and within just a few months, scientists will begin to gather and analyze detailed data revealing the chemical makeup of the comet. In 2009, NASA announced discovery of glycine in the vapor analyzed from the Stardust mission. “Glycine is an amino acid used by living organisms to make proteins, and this is the first time an amino acid has been found in a comet,” said Dr. Jamie Elsila of NASA’s Goddard Space Flight Center in Greenbelt, Md. [1]

The discovery of glycine, coupled with the water makeup of comets, has led to speculation that these deep-space objects could have brought with them the very seeds of life on Earth. Billions of years ago, the numerous icy objects would have slammed into the Archaean Earth, forming the early oceans and atmosphere, and helping to seed the Earth with amino acids, the building-blocks of life.

So as you gaze up in the early morning hours this week, consider the potential cosmological significance of those bright streaks across the dark sky.

PART TWO: Venus and Jupiter In Conjunction

If skies are clear in your area, it will be easy to spot the conjunction of Venus and Jupiter in the pre-dawn hours of August 18: they are the two brightest planets in the night sky. The visual magnitude for Venus will be ~3.91 while Jupiter will be ~1.8; this is roughly the equivalent of viewing a 100W incandescent light bulb from just over 3 miles (5km) away, and one from 8 miles (13km) away, respectively [2,3]. Venus will be 149.7 million miles away from Earth, or about 13 light minutes, and Jupiter will be 579 million miles, or about 52 light minutes.

If you’re observing through a telescope or astronomy binoculars, you’ll also be able to see all four Galilean moons, Ganymede and Callisto in oncoming orbit, and Io and Europa receding [4].

Volcanoes are a dominant feature of the surface of Venus, and until recently, thought to be extinct or inactive. However, data from the ESA Venus Express mission indicate that volcanic activity could have occurred as recently as last year!

Jupiter’s innermost Galilean moon Io is also known for volcanic activity, the source of which is the enormous force of gravity exerted upon the moon by its host planet. Io orbits Jupiter at ~350,000 km above the planet’s surface; by comparison, the Earth’s moon orbits at roughly 378,000 km above the Earth’s surface. Our moon’s gravitational tug is enough to cause the ocean tides on Earth; imagine the effect Jupiter has on Io: Jupiter is 25,839 times the mass of the Earth’s moon!

Io is tidally locked in orbit around Jupiter, and as it moves from perigee to apogee through an eccentric orbit, the gravitational forces pulling upon the moon vary, causing Io to deform as its surface flexes; this gravitational stretching can create a bulge as high as 300 feet [5], and generates a tremendous amount of internal heat that dissipates through volcanic eruptions that can eject material as high as 300 miles above the moon’s surface.

Just something to think about while gazing up at these two brightest planets as they line-up in the early morning sky.


[1] “NASA Researchers Make First Discovery of Life’s Building Block in Comet” — Bill Steigerwald, NASA Goddard Space Flight Center 2009-08-17

[2] Wolfram Alpha calculates visual magnitude of Venus on August 18 2014

[3] Wolfram Alpha calculates visual magnitude of Jupiter on August 18 2014

[4] Javascript Jupiter

[5] : “Volcanology of Io”

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