Exploration of the Solar System

Exploration of the Solar System

Our robotic probes of other planets have changed the way we see Earth. For the first time in our history we possess information about other planets that has enabled us to develop general theories about how our own planet works. Planetary exploration has revealed many “laws” of planetary science. One of the most important of these laws is that a planet`s geologic evolution is determined by its size and composition.

Large planets are more differentiated than smaller ones, which heavier elements such as iron concentrated in their cores and lighter elements on their surfaces. This differentiation concentrates  heat-generating radioactive elements, which help drive volcanism, in their outer layers. Furthemore, large planets have more volume for their surface area and so they cool slowly, retaining some of the initial heat from the accretion process. Thus, we think that a planet`s size and composition determine the lifespan of the geologic heat engine on the planet.

Astronomy compels the soul to look upwards and leads us from this world to another. (Plato). Illustration: © Elena

Volcanism ended early on the smaller planets like Mars and Mercury, and on the Moon.  These smaller bodies have lost virtually all of their heat, and their surfaces have not appreciably changed in billions of years.  In contrast, Earth`s dynamic tectonic processes continually recreate the face of the planet. Most of Earth`s surface is younger than the surfaces of the Moon, Mars and Mercury.

But Earth is the only example we have for comparing large, dynamic planets with small, dead ones. If we are to develop theories about how Earth operates, we need more than one example. And that`s where our sister planet Venus comes in. Venus`s large size and high density, as well as its position in the solar system, suggest that it should be similar to Earth. Why, then, did Venus evolve so differently, with a thick blistering atmosphere and no oceans? Were the Earth and Venus more alike earlier in the history of the solar system? Could Earth become like Venus in the future?

We are getting to know our long separated twin sister planet a lot better recently. Spacecraft like Magellan and Galileo are teaching us more about Earth’s siblings and so about ourselves. Everyone should actively advocate the continuing exploration of the solar system.

Starstuff

Starstuff

According to the laws of nature two stars of roughly the same mass will evolve in parallel. A more massif star will spend however its nuclear fuel faster and become then a red giant sooner than the other one.

As it is the first to enter the final white dwarf decline. There should therefore be many cases of binary stars at least in our galaxy, one component a red giant, the other a white dwarf, as it is the case!

Some such pairs are very close to each other. The glowing stellar atmosphere flows from the distended red giant to the compact white dwarf. The hydrogen accumulates in this case compressed to higher and higher temperatures and pressures by the intense gravity of the white dwarf, until the stolen atmosphere of the red giant undergoes thermonuclear reactions.

Don’t worry, you’ll stay alive till the end of the days, because you are made of starstuff (quotation and image: © Elena

Then the white dwarf briefly flares into brilliance. Such a binary is called a nova. It has quite a different origin from a supernova, because novae occur only in binary systems and are powered by hydrogen fusion. Supernovae occur in single stars and are powered by silicon fusion.

Red giants find their outer atmospheres blowing away into space as atoms synthesized in the interiors of stars return to the interstellar gas. Thus planetary neubulae are the final stages of Sunlike stars blowing their tops.

Finally, supernovae violently eject much of their stellar mass into space. Hydrogen fuses into helium, helium into carbon, carbon into oxygen and thereafter, in massive stars, by the successive addition of further helium nuclei, neon, magnesium, silicon, sulfur, and so on. Fusion of silicon also generates iron, a pair of silicon atoms, each with twenty-eight protons and neutrons, joining, at a temperature of billions of degrees, to make an atom of iron with fifty-six protons and neutrons.

These are all familiar chemical elements. But stellar nuclear reactions do not readily generate erbium, dysprosium, hafnium, praseodymium or yttrium.

Let’s say that all the elements of the Earth except hydrogen and some helium have been cooked by a kind of stellar alchemy billions of years ago in stars, some of which are today inconspicuous white dwarfs on the other side of the Milky Way Galaxy.

The nitrogen of our DNA, the calcium in our teeth, the iron in our blood, the carbon in our apple pies were made in the interiors of collapsing stars. We are made of starstuff!

Wonders of the World

Wonders of the World

The age and the size of the Cosmos are beyond ordinary human understanding and our tiny planet Earth is lost somewhere between eternity and immensity of the universe. And yet the humans, this young species, are brave and curious. They show much promise and in the last few millennia they have made the most astonishing and unexpected discoveries about the world and their place within it, explorations that are exhilarating to consider.

Only recently the human civilization has waded a little out to the Cosmic Sea, enough to dampen the toes or, at most, wet the ankles. The universe seems inviting and calls. The Earth is just a place. It is by no means the only place.

Special Powers. Out of our lineage, minds will spring, that will reach back to us in our littleness to know us better than we know ourselves. A day will come, one day in the unending succession of days, when beings, beings who are now latent in our thoughts and hidden in our loins, shall stand upon the earth as one stands upon a footstool, and shall laugh and reach our their hands amidst the stars (Herbert George Wells, The Discovery of the Future, Nature 65, 326, 1902.) Illustration: Elena

Humans have evolved to wonder. They have understood that knowledge is prerequisite to survival and understanding is a joy. They look back through countless years and see the great will to live struggling out of the intertidal slime, struggling from shape to shape and from power to power, crawling and then walking confidently upon the land, struggling generation after generation to master the air, creeping down into the darkness of the deep… Their future depends on how well they know this Cosmos.

Some part of human conscience knows that the Cosmos is from where we all came. And that is why we long to return. We are expanding, elaborating ourselves, pursuing our relentless inconceivable purpose, until at last it reaches us and its being beats through our brains and arteries.

We know we are approaching the greatest of mysteries.

Out of our lineage, minds will spring, that will reach back to us in our littleness to know us better than we know ourselves. A day will come, one day in the unending succession of days, when beings, beings who are now latent in our thoughts and hidden in our loins, shall stand upon the earth as one stands upon a footstool, and shall laugh and reach our their hands amidst the stars (Herbert George Wells, The Discovery of the Future, Nature 65, 326, 1902.)

In a cosmic perspective, our concerns seem insignificant, even petty, but imagination will carry humans to worlds that never were. Without imagination, humans go nowhere. Image : © Megan Jorgensen.

All that the human mind has ever accomplished is but the dream before the awakening. Image: © Elena.

The known is finite, the unknown is infinite. Intellectually we stand on an islet in the midst of an illimitable ocean of inexplicability. Our business in every generation is to reclaim a little more land (T.H. Huxley, 1887). Photo © Elena.

A mythical old man thinking about life and death. Skepticism enables humans to distinguish fancy from fact and to test speculations. Source of the image: Elena.

We are a local embodiment of a Cosmos grown to self-awareness. Our loyalties are to the species of the Earth and we speak for this planet. Photo : © Elena.

Our obligation to survive is owed not just to ourselves but also to that Cosmos, ancient and vast, from which we spring. Image: ©  Elena.

All the past is but the beginning of a beginning, and all that is and has been is but the twilight of the dawn. Photo: © Elena.

August's Meteor Showers

August’s Meteor Showers

The Fireworks of Heaven

August’s beautiful meteor showers are free for the watching – and you don’t even need binoculars

If you happen to be out away from city lights during the second week of August, look up one night and watch a multitude of meteors streak across the sky.

Each year between August 8th and 16th as many as 50 or 60 bright “falling stars” an hour appear to shoot from the constellation Perseus. These Perseid meteors, as they’re called, tend to be long and brilliant – like planets or brilliant stars streaking half-way across the sky in a matter of seconds.

The meteors are utterly silent – and eerie. But they provide one of the most beautiful shows the night sky stages for us, right on schedule each year and visible to everyone in all areas of the North America.

Fireworks of Heaven. The Perseides. Photo in public domain

In spite of its name, a falling star is not really a star, like our Sun, dropping from its positions in the heavens. It is actually a terrestrial phenomenon produced when a sandlike grain of interplanetary dust speeds into our atmosphere at 10 to 30 miles a second and incinerates from the heat of friction with the air 50 miles above us.

The Perseid meteor shower is a whole collection of these dust grains floating in an orbit around the Sun that astronomers believe to be the debris left behind by a disintegrated comet. The orbit of this interplanetary matter intercepts the orbit of the Earth in one place – the place where the Earth happens to be each August.

Of course, these few days in August are not the only time of year when you can see falling stars. Particles of interplanetary dust are bombarding the atmosphere all year long, which is why you can see a sporadic meteor almost every night.

However, the Perseid meteors are travelling together in a concentrated stream, and during the second week of August when the Earth is passing through that stream, you can suddenly see 10 times the usual number of falling stars each hour.

And unlike the sporadic meteors which whiz from every direction, the Perseids seem to be radiating from one small area of the sky. By locating the constellation Perseus – using the Big Dipper and the Milky Way, as guides, – you can spot them easily.

The very best time to watch for meteors is from around midnight to 2 a.m. The Perseids shower reaches its peak when the Earth is right in the middle of the stream of particles, and on that night the meteors fly at their thickest and fastest. If it happens to be cloudy, the show should still be good for about four nights both before and after – especially after, when the Moon is approaching last quarter.

You don’t need binoculars or any other special equipment to watch a meteor shower – only a clear, dark sky and a little watchful patience. If you’re vacationing in the mountains or at the beach, – or anywhere else away from lights and smog, – you are all set. Find a clearing away from tall trees and buildings for an unobstructed view of the starry sky. Set up a beach chair or lie back on a blanket and just wait a few minutes.

You won’t see a meteor every minute. In fact, you’ll probably see nothing for the first several minutes, then a burst of three or four in quick succession. Many will be short and faint. But chances are that just as your mind begins to wander, a brilliant yellowish flash will streak across the sky, leaving behind a faint train of smoke. Once in a while a meteor will silently explode at the end of its path in a display of celestial fireworks that never fails to win exclamations of delight.

If you’re something of a shutterbug and you would like to capture the meteor shower on video, nothing could be simpler. Lay the camera on the ground or on a rock shaded from the moonlight, set the shutter, lock it open and forget about it for half an hour or so.

Between meteors, you’ll find that identifying the constellations or simply stargazing is a peaceful and enjoyable activity.

Other objects in the sky that you might enjoy trying to spot are Mercury, Venus and Mars, which will be very low on the western horizon and setting shortly after the Sun. Jupiter, in the constellation Taurus, just south of Perseus, will rise late in the evening and will be the single brightest starlike point of light in the sky.

So invite your friends, wake up your kids – enjoy a moonlit midnight supper, lie back with a thermos of coffee and watch the fireworks of heaven.

A Grand Summer Meteor Shower

A Grand Summer Meteor Shower

Streaks of light will brighten the night sky around mid-august in North America, as one of the best and most dependable meteor showers reaches its peak. The Perseid meteors, so called because they appear to radiate from a point in the constellation Perseus, are at their peak in mid-august and viewing is especially good when the Moon’s phase is New or almost New.

It’s best to watch the Perseids (or any other meteor shower, for that matter) from a location far from interfering city lights. And be sure to arrive at your viewing site well ahead of time because it can take your eyes half an hour to fully adjust to the darkness. If you have sufficiently dark skies, you can expect to see about sixty meteors per hour after midnight, although they won’t necessarily be evenly distributed.

Comet Brorsen-Metcalf Displays a Multi-Component Tail. Photo: Public domain

The Perseids hold a special place in the history of meteor shower observations. In 1866 astronomers determined that the Perseids share their orbit with Comet 1862 III, which completes one pass around the Sun approximately every 120 years. This discovery led astronomers to conclude that the Perseid meteors are in fact tiny dust particles that have broken free of the comet, a “dirty snowball” of frozen gas and dust that leaves a trail of debris in its wake.

As Earth intersects the comet’s orbit each summer it is bombarded by countless comet particles, most of which are no larger than a grain of sand. When they strike Earth’s atmosphere at the astounding speed of 37 miles per second – nearly 135,000 miles per hour – the cometary particles vaporize, producing a brilliant streak of light across the night sky.