Celestial Objects

Intra-Atmospheric Phenomena

Shooting Star / Solid body which has penetrated into the atmosphere and whose disintegration causes light trail. It can be a meteoroid, which is an asteroid or comet fragment or, more rarely, a piece of artificial satellite. Although it can reach several meters in diameter, a meteoroid is usually not bigger than a grain of sand. Light created by the friction of the material in the air is more due to the speed of this body, which is about ten kilometers per second, than its mass. Generally, the more massive the object is, the more its progress will be important and the more it will shine. If it emits intense light when it entered the atmosphere (less than magnitude -4), then it is called “meteor”. We talk about “meteorite” if it reaches the surface of the Earth without being completely disintegrated.

Polar Lights / Called northern lights (or aurora borealis) in the northern hemisphere and southern lights (aurora australis) in the southern hemisphere, a polar light is a luminous phenomenon characterized by its extrem color in the night sky (the green predominating) and caused by the interaction between the charged particles of the solar wind and the upper atmosphere. Polar lights occur mainly in areas near the magnetic poles in an annular areas called “auroral zones”.

Solar System

The Solar System objects visible from Earth with an amateur telescope are : The Sun, The Moon, Mercury, Venus, Mars, Jupiter, Saturn, Uranus, Neptune, Pluto and the comets.

SUN

The Sun is the star of the Solar System. In astronomical classification it is a yellow dwarf-type star, consisting mostly of hydrogen and of a small proportion of helium. Around it revolve Earth and the seven other planets, at least five dwarf planets, numerous asteroids, comets, and a dust cloud. The Sun represents 99.86% of the mass of the Solar System itself, Jupiter representing more than 2/3 of all the rest. It has an average diameter of 1 391 684 km. The photosphere is the opaque and extremely luminous layer that we see when we look at the Sun. Since the density drops very fast, the solar disk has a well sharp contour rather than fuzzy boundaries. The photosphere has a grainy appearance that changes in only few minutes. Other phenomena affect it more sporadically : the sunspots. They are small dark regions whose diameter varies between a few thousand and a hundred thousand miles and last a few days to several months. Having a slightly lower temperature than the rest of the photosphere, they emit less light than their neighborhood and appear dark in contrast.
It also observe bright areas, called faculae, which appear just before the spots and persist for several weeks after the disappearance of the latter. The photosphere is covered by another atmospheric layer called chromosphere. It has a very low density (one million times less than that of the photosphere), which makes it almost invisible except during total solar eclipses, where it appears as a thin reddish ring around the lunar disk. But we can also see it without waiting for an eclipse, by observing the Sun in a wavelength corresponding to a hydrogen line called H-alpha (through a filter). In this wavelength, the photosphere disappears and only the chromosphere is visible. This type of observation shows that the external border of the chromosphere is surmounted by a multitude of vertical peaks, called spicules. They are jets of gas ejected from the chromosphere and live about ten minutes.
Beyond the outer boundary of the chromosphere, the temperature suddenly starts to rise precipitously: we enter the solar corona. This region extends over millions of miles diluent in heterogeneously space. It is even less dense than the chromosphere of the order of one ten-billionth of the density of the photosphere. Its temperature can be up to several million degrees. It consists of highly ionized gas (or plasma) of extremely low density. Unfortunately, it is only observable in space. Finally, the prominences Solar is one of the most spectacular phenomena in the crown. This is a cloud consisting of hydrogen, calcium, and various metals in the form of incandescent gases, which arises in the chromosphere and extends in the crown sometimes hundreds of thousands of kilometers. Sometimes it is supported by a loop of the magnetic field and then takes a form of an arch, which can persist for several months. The protrusions are observable either beyond the solar disk, as long bright flames or on disk, they appear very dark in contrast to the shiny background: they are then called filaments (observable alpha H).

MOON

The Moon is the only natural satellite of the Earth and the fifth largest satellite in the Solar System, with a diameter of 3474 kilometers. It contains no water, has no atmosphere, its surface is made up of rock and dust. The average distance separating the Earth is 384 400 km and is to date the only non-terrestrial object visited by man. The Moon always presents us the same side on which we can observe reliefs called “lunar mountains”, many impact craters, and dark spots called “maria”. These are traces of gigantic meteorite impacts which revealed the basalt background of the moon, of different composition and darker than the rest of the surface. Because of their widespread, it seems from the Earth to see the sea on the surface of the satellite.

Lunar X and V

Also known as X Werner (this phenomenon occurring near the crater Werner), the lunar X is the result of sunlight skimming the region of Blanchinus craters, La Caille and Purbach, whose illuminated peaks form an X. This one-time phenomenon, observable with binoculars and a little beyond telescope *terminator, occurs twenty hours before the first quarter (but it is not observable at all first neighborhoods) and lasts for about 4 hours. In the vicinity of X is also visible lunar V formed by several craters including that of Ukert. (* Line of separation between the illuminated area and the dark area of a star).

PLANETS

All the planets of the Solar System are observable from Earth with a more or less powerful instrument. In order of distance from the Sun, we have Mercury, Venus, Mars, Jupiter, Saturn, Uranus and Neptune. The outer planets, that is to say, farther from the Sun than Earth, are gaseous planets.

Mercury

Being the closest planet to the sun, so it is difficult to observe. At best, Mercury layer 2 hours and 15 minutes before the Sun rises and 2 hours and 15 minutes before him. It is best observed when it is farthest: These dates are called “pulled”. We can also observe its phases or its passages front of the Sun, called “transits”.

Venus

Nicknamed evening star, Venus is the closest planet to Earth. It is also the most shining star in the sky after the Sun and the Moon. It can be seen at sunrise or sunset, or, unlike Mercury, sometimes even at night (She layer 4 hours before the sun rises and 4 hours before it). It has very little detail on its surface but its phases are easily observable with a small instrument. The orbit of Venus is also lower than that of the Earth, it also happens to pass by the sun. But his transits are much rarer than those of Mercury.

March

It is an outer planet, ie further from the Sun than Earth. Its ocher surface offers many details including dark spots, some white spots (polar ice caps and Hellas impact basin), but also orange sandstorms, sometimes covering the entire surface of the planet and giving it a look uniform. But beware, this planet is observable to the telescope every 2 years and 50 days, during 3 months, during the “Martian oppositions.” During these periods, Mars is closest to Earth and yet away from the Sun in relation to it. So there is an alignment Sun-Earth-Mars. In the months preceding and following the opposition, you can admire its phases that make it sometimes seem like the moon.

Jupiter

It is the largest planet in the Solar System. Unlike the previous three, there is a gas planet. The slightly flattened shape and atmosphere organized in ivory white and brown stripes are the result of its rapid rotation (it made a turn on itself in less than 10 minutes!). His numerous disturbances, including its white oval and its Great Red Spot offers a breathtaking spectacle. The latter is actually a giant storm that seems to last forever. Jupiter is easy to do with a small instrument and is observable 11 months a year.

Saturn

It is often considered by many as the most beautiful planet in the Solar System, and is in any case the only one ring is visible with a telescope amateur. Jupiter is very far from the Sun and takes almost 30 years to complete its revolution. Being also a gaseous planet, the centrifugal force due to rotation that the globe of Saturn is even flatter than that of Jupiter. Its atmosphere is divided into bands, but these are less marked. There is however a clear zone at the equator and darkening the geographic poles levels. Her ring is actually composed of thousands of concentric rings. But the telescope, it seems that it is divided into only two parts, about 1/3 in from the outside (Cassini division). The shadow of the ring projected onto the surface of Saturn, or even more, that of the globe on the ring accentuate the three-dimensional aspect of the object.

Uranus

It remains small apparent size, even in a powerful enough telescope. Moreover, its atmosphere has very little detail. However, its turquoise blue shade is particularly fascinating. It is also interesting to identify its major satellites.

Neptune

The last planet of the Solar System is even more difficult to observe because of its remoteness and its small apparent diameter. However, at high magnification and a large aperture (minimum 150 mm), it is not revealed as a simple point, but as a small blue disk.

Comets

Rocky body covered with a thick layer of ice and dust orbiting a star. Its name comes from the Greek coma meaning “tail” because when the body approaches the Sun, some of its material sublime and the star develops a dust tail and long gas millions of miles. This material, sometimes called hair reflected the sunlight that makes it visible from Earth. Comets were formed with the Solar System, in its cold regions, there is 4.6 billion years and can reach several tens of kilometers in diameter.