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Posted: 05 Jan 2015 10:29 PM PST
Scientists theorize that asteroids, not comets, created Earth’s oceans with terrestrial water. Photo courtesy of NASA/Don Davis
Excerpt from newsok.com
Wayne Harris-Wyrick: Asteroid impacts that, today, could wipe out life on Earth, made it possible for life to flourish here in the first place by providing the precious water.
Water is rather ubiquitous, cosmically speaking, composed of hydrogen, the most common element in the universe, and oxygen, the third most common. In between is helium, a noble gas that doesn’t play well with other elements.Water was present in great quantity 4.6 billion years ago when the planets of our solar system took shape. Venus, Earth and Mars formed with copious amounts of water. But Venus’ 900-degree atmosphere boiled it away and broke it down into its constituent parts or combined it with sulfur dioxide gas to create the planet’s thick sulfuric acid cloud cover. Mars’ small size meant weak gravity, so its atmosphere leaked into space, and its water evaporated, which it does with no air pressure above it, and also leaked into space.
Strong, active volcanism, aided by massive asteroid impacts boiled into space most, if not all, of remaining water on all three planets. And yet, today, three quarters of Earth is covered with water. Where did it come from?
For years, astronomers assumed that comets, the most common water-bearing objects in our solar system, brought the water to Earth. But comets formed much farther from the sun than Earth did. The isotopic composition of water differs with distance from the sun.
Thanks to the Rosetta spacecraft, we now know that cometary water doesn’t match terrestrial water. But asteroid water does. Today, asteroids are quite parched, but 4.5 billion years ago, when many asteroids impacted the planets and moons of the inner solar system, water represented a much larger fraction of their mass. And, it appears, they are the source of Earth’s oceans.
It turns out that asteroid impacts that, today, could wipe out life on Earth, made it possible for life to flourish here in the first place by providing the precious water.
Posted: 05 Jan 2015 10:23 PM PST
We need not worry, however. According to study conducted by Dr. Coryn Bailer-Jones of the Max Planck Institute for Astronomy in Heidelberg, the binary star from the Hercules constellation will pass by our system at a distance of 0.04 parsecs.
Despite what Han Solo would have you believe, a parsec is a unit of distance and .04 parsecs translates to 8,000 times the distance between the Earth and the Sun.
If that is still too close for comfort, know that this astronomical drive-by won’t occur for at least another 240,000 years.
“Even though the galaxy contains very many stars the spaces between them are huge,” Bailor-Jones said. So even over the (long) life of our galaxy so far, the probability of any two stars have actually collided—as opposed to just coming close—is extremely small.”
The close encounter (on a universal scale, anyway) will be the first since a gas giant passed within 0.35-1.34 pc of our solar system over 3.8 million years ago, according to Bailor-Jones.
Posted: 05 Jan 2015 10:15 PM PST
Astronomers have proved that they can accurately tell the age of a star from how fast it is spinning.
For the first time, a US team has now measured the spin speed of stars that are more than one billion years old - and it matches what they predicted.
The finding resolves a long-standing challenge, allowing astronomers to estimate a star's age to within 10%.
The work was presented in Seattle at a meeting of the American Astronomical Society and also appears in the journal Nature.
Closing a gap
Establishing the age of stars is a central question in astronomy - much like dating fossils is crucial to studying evolution.
This method applies to "cool stars" - suns about the size of our own, or smaller. These are the most common stars in our galaxy and they also last for a long time.
"They act as lamp posts, lighting up even the oldest parts of our galaxy," said senior author Dr Soren Meibom from the Harvard-Smithsonian Center for Astrophysics.
Cool stars also host the vast majority of earth-like planets that we have spotted in the distance.
Most properties of a star like ours - like its size, mass, brightness and temperature - stay about the same throughout most of its life.
The solution of measuring spin was first proposed in the 1970s and was dubbed "gyrochronology" in 2003.
"A cool star spins very fast when it's young, but just like a top on a table it gets slower and slower as the star grows older," Dr Meibom said.
But it is difficult to see a star spinning. Astronomers use sun spots, travelling across the surface, and these only dim its brightness by much less than 1%.
Old stars are particularly problematic, because they have fewer and smaller spots.
Dr Meibom's team used images from the very sensitive Kepler space telescope, which has been trailing Earth around the Sun since 2009.
They managed to measure spin speeds for 30 stars in a specific cluster known to be 2.5 billion years old.
This cluster, known as NGC 6819, plugs what Dr Meibom called a "four-billion-year gap" in our knowledge of stellar spin.
Before the Kepler mission, we only had data from very cool stars in very young clusters, all less than 0.6 billion years old and all spinning fairly fast (about once a week).
In 2011, Dr Meibom's team used Kepler images to report on a different cluster, the one-billion-year-old NGC 6811. Its cool stars spin about once every 10 days.
But beyond that, the only star we knew both age and spin rate for was our own sun - 4.6 billion years old, with a spin period of 26 days.
"The construction of the cool star clock was on hold," Dr Meibom said.
Now, the clock is looking good. The sun-like stars in the freshly studied cluster sit squarely and satisfyingly in the gap, spinning about every 18 days.
Older stars, more like our own Sun, are trickier to assess because they have fewer and smaller spots
"These new data show, with real observations, that this is on solid ground," Dr Meibom told BBC News.
"We can get age as accurately as about 10% from this method."
He added that this is a big improvement on some other methods for guessing stars' age, where the margin of error for cool stars can reach 100%.
Ruth Angus, a PhD student researching gyrochronology at the University of Oxford, said the results were "a really big deal" for the field.
"More evidence has been slowly accumulating that lots of stars do seem to follow this pattern, but how reliably stars fall onto this relation is a bit of an unknown," Ms Angus told the BBC.
"This cluster will certainly help with our understanding of how good gyrochronology is as a method, and how valid it is.
"It shows that these stars are doing what they're expected to do, and everything's peachy."
Posted: 05 Jan 2015 10:09 PM PST
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Posted: 05 Jan 2015 10:01 PM PST
Excerpt from tinyhousetalk.com
So it’s no wonder that you’d be interested… But the question is, “how much?”
Question: So How Much Does it Cost to Build a Tiny House?
Answer: Usually Around $25,000 to $30,000This is for a relatively ‘high end’ tiny home on wheels with all of the amenities of home you’d be looking at around $25,000 to $30,000 in materials to build it yourself.
This figure normally includes buying a brand new trailer, professional construction plans, your appliances, and other materials brand new at the store.
Of course it’s always possible to do it for $13,173, $9,802, $21,204, or even $65,439 but this is just an estimation so you know what to expect and what I’ve believe to be most common but..
Here’s How You Can Do It For Less
Posted: 05 Jan 2015 09:50 PM PST
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Posted: 05 Jan 2015 09:38 PM PST
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