August 14, 2010
'Dog Days' of Summer Have Celestial Origin
The "dog days" of summer officially came to an end this week, but few people know what the expression really means. The phrase actually has a celestial origin.
Some will say that summer's "dog days" signify hot sultry days "not fit for a dog," while others suggest it's the weather in which dogs go mad.
But the "dog days" are actually defined as the period from July 3 through Aug. 11 when the Dog Star, Sirius, rises in conjunction (or nearly so) with the sun.
As a result, some felt that the combination of the brightest luminary of the day (the sun) and the brightest star of night (Sirius) was responsible for the extreme heat that is experienced during the hieght of the summertime. Other effects, according to the ancients, included droughts, plagues and madness.
Some will say that summer's "dog days" signify hot sultry days "not fit for a dog," while others suggest it's the weather in which dogs go mad.
But the "dog days" are actually defined as the period from July 3 through Aug. 11 when the Dog Star, Sirius, rises in conjunction (or nearly so) with the sun.
As a result, some felt that the combination of the brightest luminary of the day (the sun) and the brightest star of night (Sirius) was responsible for the extreme heat that is experienced during the hieght of the summertime. Other effects, according to the ancients, included droughts, plagues and madness.
July 30, 2010
No Doomsday in 2012!
Apparently, the world is going to end on December 21st, 2012. Yes, you read correctly, in some way, shape or form, the Earth (or at least a large portion of humans on the planet) will cease to exist. Stop planning your careers, don't bother buying a house, and be sure to spend the last years of your life doing something you always wanted to do but never had the time. Now you have the time to enjoy yourselves before… the end ;).
So what is all this crazy talk? We've all heard these doomsday predictions before, we're still here, and the planet is still here, why is 2012 so important? Well, the Mayan calendar stops at the end of the year 2012, churning up all sorts of religious, scientific, astrological and historic reasons why this calendar foretells the end of life as we know it.
So what is all this crazy talk? We've all heard these doomsday predictions before, we're still here, and the planet is still here, why is 2012 so important? Well, the Mayan calendar stops at the end of the year 2012, churning up all sorts of religious, scientific, astrological and historic reasons why this calendar foretells the end of life as we know it.
July 23, 2010
RED GIANTS & white dwarfs
Life-cycle of the Sun; sizes are not drawn to scale.
Everything that has a beginning has an end. When the Oracle from The Matrix stated this famous line she wasn't kidding! Everything comes to an end, even stars...yes stars die! Most people are surprised to hear this, stars are after all gigantic celestial bodies which give off immense heat and light through nuclear fusion...something so powerful should last for eternity. However these massive, luminous balls of plasma held together by gravity run out of fuel just like a car and eventually "die".
Stellar evolution is the process by which a star undergoes a sequence of radical changes during its lifetime. Depending on the mass of the star, this lifetime ranges from only a few million years (for the most massive) to trillions of years (for the least massive, which is considerably more than the age of the universe itself!).
Let's start with the baby steps: stars, just like our Sun, are formed within large regions of gas and dust in the interstellar medium. These regions are called molecular clouds and consist mostly of hydrogen, with about 23–28% helium and a few percent heavier elements. One example of such a star-forming region is the Orion Nebula. The formation of a star begins with a gravitational instability inside a molecular cloud. As the cloud collapses the density increases, the gravitational energy is converted into heat and the temperature rises. A star is born!
Once formed, stars spend about 90% of their lifetime fusing hydrogen to produce helium in high-temperature and high-pressure reactions near the core. Such stars are said to be on the main sequence ( again just like our Sun). The duration that a star spends on the main sequence depends primarily on the amount of fuel it has to fuse and the rate at which it fuses that fuel, i.e. its initial mass and its luminosity. Large stars consume their fuel very rapidly and are short-lived. Small stars consume their fuel very slowly and last tens to hundreds of billions of years.
So after a few billion years the center of a star runs out of protons (nuclei of hydrogen atoms). What is left is a core or central region made of alphas (nuclei of helium atoms). The outer layers of the star still contain hydrogen, but they are not hot enough to fuse. Because it has run out of fuel, the star begins to cool, and contract. The outer layers of the star fall inwards under gravity, and as they fall they heat up. A shell surrounding the central core becomes hot enough to fuse protons into alphas. So the star gains a new source of energy. The core of the star is now hotter than it was during its normal life and this heat causes the outer parts of the star to swell. The star becomes a giant. The radiation from the fusing shell has grown weak by the time it reaches the surface of the star. Weak radiation is red, so the star becomes a red giant. In fact the Sun will run out of fuel and become a red giant in about 5 billion years.As a red giant, the Sun will have a maximum radius beyond the Earth's current orbit, 1 AU (1.5×1011 m), 250 times the present radius of the Sun. Our poor planet will most likely be incinerated from the immense heat of the swollen Sun! Global warming doesn't seem such a big problem now!:P
At the end, following the red giant phase, intense thermal pulsations will cause the Sun to throw off its outer layers, forming a planetary nebula. The only object that will remain after the outer layers are ejected is the extremely hot stellar core, which will slowly cool and fade as a white dwarf over many billions of years.
Rami B.
July 15, 2010
Amazing astronomy facts!
Earth weighs in at around 6.6 Sextillion Tons
Earth is hit by 6 tons of meteorites( small space rocks) a day, every day.
Earth,our beloved home, is said to have an atmosphere that is proportionally thinner than the skin of an apple.
Among the biggest known stars, Betelgeuse, in the constellation of Orion, is 425 light years away and 60,000 times brighter than our star the Sun. It is so big that if you replaced the Sun with Betelgeuse, Betelgeuse would fill our solar system out past the orbit of Jupiter.
Light from the sun takes 8 minutes to reach you, thus you see the sun as it was 8 minutes ago. It might have blown up 4 minutes ago and you wouldn't know about it!:P
When Galileo viewed Saturn for the first time through a telescope, he described the planet as having "ears". It was not until 1655 that Christian Huygens suggested the crazy theory that they might in fact be an enormous set of rings around the planet.
If you could put Saturn in an enormous bathtub, it would float. The planet is less dense than water.
Jupiter is heavier than all the other planets put together.
Even on the clearest night, the human eye can only see about 3,000 stars. There are an estimated 100,000,000,000 in our galaxy alone!
The tallest mountain in the solar system is Olympus Mons on Mars at a height of about 20 km!!!Three times the height of Mount Everest. It covers an area about half the size of Spain.
Temperatures on Venus are hot enough to melt iron!
Only one side of the moon ever faces Earth! We can never see the other side from Earth!!The moon's rotational period is exactly the same as its orbital period.
Its estimated that the number of stars in the universe is greater than the number of grains of sand on all the beaches in the world! On a clear night, we can see the equivalent of a handful of sand.
Every year the sun evaporates 100,000 cubic miles of water from Earth (which weighs about 400 trillion tonnes!)
Saturn is not the only planet with rings- Jupiter, Uranus and Neptune have their own ring system, much less bright than Saturn's though and invisble from Earth. The Earth had a ring system too but it vanished a long time ago.
Earth is hit by 6 tons of meteorites( small space rocks) a day, every day.
Earth,our beloved home, is said to have an atmosphere that is proportionally thinner than the skin of an apple.
Among the biggest known stars, Betelgeuse, in the constellation of Orion, is 425 light years away and 60,000 times brighter than our star the Sun. It is so big that if you replaced the Sun with Betelgeuse, Betelgeuse would fill our solar system out past the orbit of Jupiter.
Light from the sun takes 8 minutes to reach you, thus you see the sun as it was 8 minutes ago. It might have blown up 4 minutes ago and you wouldn't know about it!:P
When Galileo viewed Saturn for the first time through a telescope, he described the planet as having "ears". It was not until 1655 that Christian Huygens suggested the crazy theory that they might in fact be an enormous set of rings around the planet.
If you could put Saturn in an enormous bathtub, it would float. The planet is less dense than water.
Jupiter is heavier than all the other planets put together.
Even on the clearest night, the human eye can only see about 3,000 stars. There are an estimated 100,000,000,000 in our galaxy alone!
The tallest mountain in the solar system is Olympus Mons on Mars at a height of about 20 km!!!Three times the height of Mount Everest. It covers an area about half the size of Spain.
Temperatures on Venus are hot enough to melt iron!
Only one side of the moon ever faces Earth! We can never see the other side from Earth!!The moon's rotational period is exactly the same as its orbital period.
Its estimated that the number of stars in the universe is greater than the number of grains of sand on all the beaches in the world! On a clear night, we can see the equivalent of a handful of sand.
Every year the sun evaporates 100,000 cubic miles of water from Earth (which weighs about 400 trillion tonnes!)
Saturn is not the only planet with rings- Jupiter, Uranus and Neptune have their own ring system, much less bright than Saturn's though and invisble from Earth. The Earth had a ring system too but it vanished a long time ago.