Unfortunate Misconceptions (Trivia) about Astronomy

This class is Astronomy, not Astrology.  They had the same roots.  Each talks about planets and zodiac constellations, but their interpretations are totally different.  Astrology might as well talk about some fictitious planet, so their “Mars” would not be confused with the real Mars.

The seasons are caused by Earth’s orbit and the tilt of its axis , not by varying distance.  The result is that we have longer days and more direct sunlight in summer, and vice versa in winter.

Our Sun is an ordinary star like all the other billions of stars in our Galaxy and all the other billions of galaxies  -  it is only much closer than any other star.  All stars (including our Sun) function on the same principles: nuclear fusion produces energy, which is given off into space as radiation, they have an absorption spectrum, they are between 0.3 and 50 million miles in diameter and they have a mass between 0.1 and 40 sun masses.

Many stars are as bright, most are fainter and a few are brighter than our Sun.  But all appear much fainter because they are so far away.  The closest star is 90 million away (our Sun), the next ones are 30 trillion miles away (i.e. 300,000 times farther), a typical distance between neighboring stars.

Stars do not twinkle.  Instead our Earth’s own atmosphere “smears” their images, so that a twinkling effect occurs.

The planets in our solar system orbit our Sun, because they are gravitationally bound, and they reflect our Sun’s light.  Their moons too are gravitationally bound to them, orbit their planets, and reflect our Sun’s light.

Most likely other stars have planets too  -  but they are outshone by their own suns.  Using indirect methods, some planets have been discovered only recently (since fall of 1995).  The latest summaries appeared in the August 1996 issue of Sky & Telescope (www.skypub.com), respectively Extrasolar Planets (Other Worlds, Distant Suns) (http://www.astronautica.com/owds.html).

Our Moon orbits the Earth and reflects our Sun’s light, too.  Its phases depend on the angle we view it in relation to our Sun.  Our Moon’s phases have nothing to do with its own, Earth’s, or anybody else’s shadow.  But eclipses do.

Our Moon is not a night object.  After all, since it orbits Earth, it must appear half of the time in the day time sky.  So don’t be surprised to see our Moon during the day.
Our Moon only appears to be a night object for two reasons: first, if it’s in the sky at night it’s the brightest object, second, it shows a rather gibbous or full phase.  During the day our Moon is lost in the blazing blue sky and it usually exhibits a rather crescent (sliver) phase.

Our Moon’s “far side” has been completely mapped by Apollo, Luna, and Clementine spacecraft.  It’s not dark, since it receives just as much sunlight as the near side.  Since our Moon “wobbles” east and west, we can see actually 60% of our Moon’s surface from Earth.

Tides are caused by our Moon’s and our Sun’s (“differential”) gravitational force, the latter’s effect being only half as strong.

And last, not least, our Moon has gravity - because everything with mass exerts gravitation.  After all, those Astronauts from the Apollo program aren't floating around but - at 1/6 g - are down to Moon.

Mercury, Venus, (Mars), Jupiter, (Saturn) are often brighter than any stars  -  simply because they are much closer to Earth.  That’s why most people have probably seen them already, even without knowing it.  I admit that Mercury is very hard to see because it’s so close to our Sun.  Good binoculars or a small telescope can show Saturn’s rings, Jupiter’s moons and Venus’ phases.

The so-called morning and evening star is one and the same planet:  Venus.

Falling or shooting stars aren’t stars either, they are rocky meteors, and in most cases they’re just dust particles evaporated from comets.

A comet’s tails consist of dust and (ionized) gases which were evaporated by sunlight and are always pushed away from our Sun because of the outward streaming solar wind.

The North Star (called Polaris; in the constellation Ursa Minor = Little Bear = Little Dipper) is not a bright star (it ranks 48th), but is special because it’s always in the same place because Earth’s axis points directly at it.

All other stars seemingly move (just like Sun, Moon, and planets do) as the Earth rotates on its axis.

Astronomers don’t believe that aliens are visiting Earth, because we know the technological and realize the rational odds of somebody visiting us.
However, most of us do believe that intelligent life elsewhere in the universe exists  - we don’t know where though and we haven’t got any signals at all.  And if we knew, we had to wait for perhaps tens of thousands of years for answers  - being hampered by the finite speed of communication (speed of light).  On the other hand, we would be rather happy if somebody would visit us.  Until then we abstain from any UFO speculation.  We do not give credit to accounts of sightings as extraordinary claims require extraordinary proof (meaning that verbal accounts and fuzzy pictures are not sufficient).

Magnification is not the most important property of a telescope, light-gathering power and resolution are.  A larger telescope (that means the diameter of its objective) detects fainter objects and produces sharper images.

Start with binoculars, do not buy a cheap telescope.  Cheap telescopes aren’t worth the $200 they cost and will collect dust in your attic.

Some labels in Astronomy are unfortunate, because they’re misleading or sound mysteriously:  falling star, evening star, planetary nebula, dark matter, antimatter, black hole, Andromeda Nebula, Milky Way, ...

Some labels are right on the money:  neutron star, white dwarf, red giant, black hole ...

Astronomy is stuck with seemingly nonscientific nomenclature:  A reverse magnitude system, spectral classification, names of constellations, non-metric units, ...

To my WNCC Astronomy home page .