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.

Ceres: The First Asteroid

Ceres: The First Asteroid

The nineteenth century began with an astronomical bang: the discovery of an apparent planet between the orbits of Mars and Jupiter. However, the “planet” discovered on January 1, 1801, wasn’t really a planet at all. Instead, it was the largest example of a new class of object – an asteroid. The new-found object was later named Ceres.

Giuseppe Piazzi, a Sicilian priest and astronomer, discovered Ceres accidentally while mapping a section of the sky. Over a period of several nights Piazzi watched as this new object, which he originally believed to be a comet, moved steadily against the background of stars. When it reversed directions, as all planets do periodically, it seemed that the astronomer had found a “missing” planet.

Thanks to a simple mathematical relationship called Bode’s Law, astronomers of the day believed that a planet must exist in the wide gap between the orbits of Mars and Jupiter. Until Piazzi’s discovery, though, no one could find it.

Ceres. The history of astronomy is a history of receding horizons. (Edwin Powell Hubble). Photo of Ceres: Public domain

Piazzi became ill shortly after discovering the mysterious object. And by the time word of his findings reached other astronomers, Ceres had moved too near the Sun for anyone to observe it.

Meanwhile, a young German mathematician, Karl Friedrich Gauss, used Piazzi’s observations to calculate the object’s orbit. Gausse correctly predicted when and where the object would re-emerge from the Sun’s glare, and the “planet” was rediscovered on December 31, 1801. It was later named Ceres after the Roman goddess of agriculture.

And there, Piazzi and other astronomers thought, the story would end. It did not. In March 1802, a second body was discovered in an orbit similar to Ceres’. Thousands of others have been found since.

The Cosmos. Illustration by Elena.

Is It a Planet or a Star?

Is It a Planet or a Star?

The question is often asked “What is the difference between a planet and a star?” The answer will be obvious when we have gained a little knowledge of both types of celestial objects.

Looking up at the sky on any clear night we see apparently countless stars ranging in brightness from those at the limit of our vision to ones which are outstandingly brilliant. Some nights we notice that the stars are twinkling, but there may be one or two among the brighter ones that do not twinkle. Note the positions of these with reference to the pattern of surrounding stars, and watch them carefully for a week or more. It may surprise you to find that, unlike the so-called “fixed” stars, these non-twinklers have moved from the positions first noted. These are the planets.

All the stars which we see on any clear night are members of that vast organization called the Milky Way. The sun is an average member of this group, but as the dominating body in our solar system, is of great importance to us. The Earth and the other planets all move in definite paths about the Sun and consequently the planets move in relation to the background of stars.

Grass and Cactus. Grass on Earth. Illustration: Megan

Let us outline briefly some other characteristics of the planets and stars to see where they differ, for we shall find that in practically no characteristics are they alike. The stars – like the Sun – are known to be enormous spheres of gaseous material, so hot that they radiate their own light. On the other hand the planets are small, they are cool, and shine only because they reflect some of the sunlight falling upon them. To make a comparison of size, Jupiter, the largest planet, has a diameter of 88,700 miles, while an average star – our sun – has a diameter almost 10 times that amount.

Some of the stars are so enormous that were they hollow, the four inner planets could easily revolve in their paths within one of these giants. Considering temperatures, it is known that the planets nearest the Sun would be uncomfortably hot for us, while the more distant ones would be much too cold. Jupiter, for instance, is about -150 degrees C. However, on stellar standards all the planets are chilly, for a “cool” star like the sun has a surface temperature of about 5,500 degrees C, while “hot” stars have temperatures 9 or 10 times that amount, and perhaps even higher.

Experience has shown that regardless of the telescope used, stars appear as pin points of light, while planets show a sizeable disc. The reason for this is difference in their distances. Pluto, at a mean distance from the Sun of 3, 664, 000, 000 miles, is the most remote solid corps in Solar system, but stellar distances range from 26, 000, 000, 000, 000 miles to many thousands of times that distance. The yardstick used for that measurement is usually the light-year rather than the mile, and on this scale the nearest star is 4, 3 light-years away. A light-year is a distance traveled by light in a year, at the rate of 186, 300 miles per second.

Summing up the main points indicated above we find that:

• Planets do not twinkle – Stars twinkle
• Planets move among the stars – Stars appear to be “fixed”
• Planets revolve about the Sun – Stars do not revolve about the Sun
• Planets are relatively small – Stars in general are very large
• Planets are “cool” – Stars are extremely “hot”
• Planets shine by reflective sunlight – Stars shine by their own light
• Planets appear as discs – Stars appear as points of light
• Planets are near to us – Stars are very far away.

Stars and Planets are part of our Univers. Illustration: Megan Jorgensen.

Neutrinos

Neutrinos

As you look up at the Sun for a second, a billion neutrinos pass through your eyeball, as nuclear fusion is eating the stars from inside and they irradiate flux of light and neutrinos.

Neutrinos, like photons, weigh nothing and travel at the speed of light.

The conversion of hydrogen into helium in the center of the stars accounts for their brightness in visible light. But this conversion also produces neutrinos, a radiance of mysterious and ghostly kind which make any star glow faintly…

Neutrinos are not a kind of light, thus they are not photons. Matter is transparent to neutrinos, which pass effortlessly through the Earth and through the stars. These elements, like protons, electrons and neutrons, carry an intrinsic angular momentum, or spin, while protons have no spin at all. Only a tiny fraction of neutrinos is stopped by the intervening matter.

Frozen. The Earth is as transparent to neutrinos as a pane of clear glass is to visible light. Image: © Elena

Of course, when neutrino reaches you eyeball, it is not stopped at the retina as ordinary photons but it continues unmolested through the back of your head.

The curious part is that if at night you look down at the ground, toward the place where the Sun would be seen if the Earth were not in the way, the same number of solar neutrinos pass through your eyeball, pouring through an interposed Earth which is as transparent to neutrinos as a pane of clear glass is to visible light.

We understand the nuclear physics enough to calculate with fair accuracy the number of solar neutrinos which pass through a given area in a given unit of time. Experimental confirmation of the calculation is however much more difficult. Indeed, since neutrinos pass through the Earth without noticing it, we cannot catch a neutrino.

For a very vast number of neutrinos, however, a very small fraction of them will interact with matter. In the appropriate circumstances they might be detected. They can also on rare occasion convert protons and neutrons.

A few experiments using chlorine, a cleaning fluid, have been performed to neutrinos, as to detect the predicted solar neutrino flux, you need chlorine (American physicists have poured a huge quantity of chlorine into the Homestake Mine in Lead, South Dakota for their experiments). The chlorine is micro-chemically swept for the newly produced argon. The more argon found, the more neutrinos inferred.

These experiments have proved that the Sun is dimmer in neutrinos than the calculations predict. If this is true (and it seems it is true), there is a real and unsolved mystery here.

This low solar neutrino flux does not put our view of stellar nucleo-synthesis in jeopardy. Proposed explanations range from the hypothesis that the nuclear fires in the solar interior are temporarily banked, sunlight being generated partly by slow gravitational contraction, to the idea that neutrinos fall to pieces during their passage between the Sun and the Earth.

Neutrino astronomy is very new. For the moment we stand amazed at having created a tool that can peer directly into the blazing heart of the Sun. As the sensitivity of the neutrino telescope improves, it may become possible for the Humans to prove nuclear fusion in the deep interiors of the nearby stars.

What Are the Stars

What Are the Stars?

About five hundred years ago humans answered the question that had so excited Carl Sagan as a boy growing up in Brooklyn: What are the stars?

The answer is that the stars are mighty suns, light away from the Earth in the vastness of interstellar space. When the Humans completed their first project to map the starry skies, they found apparently equal numbers of stars in all directions in the plane or band of the Milky Way. From this great picture, reasonably enough, the Earthlings deduced that they might not be alone in the Universe.

This is true. Intelligent life has been extended far beyond the realm of the stars. The great legacy of the Ancestors is this: neither the human civilization nor their planet enjoys a privileged position in Nature.

On the countless other planets that cercle other suns, there is life. Sometimes, it is based on the same organic molecules as life on Earth. Some other times, it is very different. Beyond Horizons.

You must have the courage to admit that the solar system is in the outskirts and not near the core of your galaxy. You live some 30,000 light-years from the Milky Way galactic core, on the fringes of a spiral arm, where the local density of stars is relatively sparse. Near the center of the Milky Way, however, millions of brilliant stars would be visible to the naked eye, compared to your paltry few thousand.

There are those who live on a planet that orbits a central star in globular clusters, and one located in the core of the galaxy. Those beings pity the Earth for your handful of naked-eye stars, because their skies are ablaze with them. Their Sun or suns might set, but the night would never come.

A great star cloud in the constellation Caelum looking toward the center of the Aeretis Galaxy.

The obscuring lanes of dust contain organic molecules: some of the contain stars in the earliest stages of formation.

In this photograph made by a professional photographer from Galaxy, there are about two million stars. According to the estimates of the savants, two of them are the suns of a civilisation more advanced than the Earth.

Fast interstellar spaceflight – with the ship velocity approaching the speed of light – is an objective for a thousand or ten thousand years for Humanity. But it is in principle possible. A kind of interstellar ramjet has been proposed by R. W. Bussard which scoops up the diffuse matter, mostly hydrogen atoms, that floats between the stars, accelerates it into a fusion engine and ejects it out the back.

A portion of the Hercules cluster of galaxies, with about four hundred members, retreating from our region of the Cosmos at some 10,000 kilometers per second.

If the Hercules cluster is not flying apart, there must be five times more mass there, gravitationally gluing the cluster together, than we see in the galaxies. Such missing mass, if common in intergalactic space, would make a major contribution to closing the universe.

Here there are more galaxies (in excess of 300 million-light years distant) than there are foreground stars in the Milky Way Galaxy.

Major recent collisions from Saturn to Venus were alleged in a popular book, Worlds in Collision, published in 1950 by a psychiatrist named Immanuel Velikovsky. He proposed that an object of planetary mass, which he called a comet, was somehow generated in the Jupiter system. Some 3,500 years ago, it careered in toward the inner solar system and made repeated encounters with the Earth and Mars, having as incidental consequences the parting of the Red Sea, allowing Moses and the Israleites to escape from Pharaoh, and the stopping of the Earth from Rotating on Joshua’s command. It also caused, he said, extensive vulcanism and floods. Velikovsky imagined the comet, after a complicated game of interplanetary billiards, to settle down into a stable, nearly circular orbit, becoming the planet Venus – which he claimed never existed before then.

Asteroids may represent debris prevented by the gravity of a planet (such as Saturn with its belt) from accreting into a nearby moon, or they may be the remains of a moon that wandered too close and was torn apart by the gravitational tides. Alternatively, they may be the steady state equilibrium between material ejected from a moon of a planet (for Saturn it could be its moon Titan), and material falling into the atmosphere of the planet.

The unknown. Illustration by Elena.