Where does the Moon come from? The leading hypothesis is the "Giant Impact Hypothesis" also known as the Big Splash or Big Whack (...with homage--vocabulary flash!--to the Big Bang.)
This theory says...
A large Mars-size molten object named Theia crashed into the young Earth at an oblique angle. The object sank within Earth's molten core. But the impact spun off debris that orbited the Earth for a short while and then coalesced into the a single object, the moon.
This coalescence may have taken less than a month but definitely no more than a century. PDQ in astronomical terms. (Pretty Darn Quick)
After the impact the Earth was spinning much faster than now, with an earth day only 5 hours long.
If your were alive back then and wanted a good night's sleep of about ten hours, you'd have to sleep through two nights. And two days...
...three days if you're a teenager. Of course after that you'd pull three all-nighters in a row to be awake for a normal 15 hours.
It seems there is still lots of debate over this hypothesis. There's some good evidence both fer and agin it...same for the other hypotheses.
Isotopic similarities between earth rocks and moon rocks brought back by Apollo astronauts gives some impetus to the Big Splash.
Sunday, June 28, 2009
Saturday, June 27, 2009
The Rings of Saturn...and Other Planets
The Rings of Saturn are not the only rings. All of the gas giant planets--Jupiter, Saturn, Uranus and Neptune--have rings. It's just Saturn's are the easiest to see.
Also, one moon might have a ring around it: Rhea, one of Saturn's larger moons. Wouldn't that be a ring that zings around another ring?
Scientists think that Phobos, one of Mars' moons, will eventually breakup and become a ring. Phobos' has a very low orbit around Mars and getting lower all the time until, eventually, it is broken into pieces by Mars' gravity. Or so they think!
And they assume Earth once had a ring. That was after Theia hit the Earth and created the moon. What's that??? I'll tell you next time......
PIA07712_-_F_ring_animation.gif
Also, one moon might have a ring around it: Rhea, one of Saturn's larger moons. Wouldn't that be a ring that zings around another ring?
Scientists think that Phobos, one of Mars' moons, will eventually breakup and become a ring. Phobos' has a very low orbit around Mars and getting lower all the time until, eventually, it is broken into pieces by Mars' gravity. Or so they think!
And they assume Earth once had a ring. That was after Theia hit the Earth and created the moon. What's that??? I'll tell you next time......
PIA07712_-_F_ring_animation.gif
Thursday, June 25, 2009
Salty Ocean on a Moon of Saturn?
Extraterrestrial life frozen into the Rings of Saturn??? An salty ocean teeming with extraterrestrial life spews geysers from under the crust of Enceladus, one of Saturn's moons???
Today an article in the science journal Nature said that salty water is shooting out of Enceladus, one of Saturn's moons. And that the conditions for life to exist might lie beneath that moon's surface. But another article published alongside it argues that the water isn't salty.
Whether the water jets spewing from Enceladus's south pole are salty or not seems to be a big deal. But I don't understand why, do you? It has something to do with whether there could be an ocean under Enceladus' surface and perhaps extraterrestrial life in that ocean. Can anyone explain why the salt is so important?
Aside from the salt issue, it is confirmed true that (1) There are huge plumes of water vapor and ice crystals being ejected from Enceladus' south pole and (2) One of the outermost rings around Saturn (the E Ring) is composed of ice particles that come mostly from this these plumes emanating (vocabulary flash!) from this moon. That was discovered just a few years ago by NASA's Cassini spacecraft.
So this obscure little moon--just one-seventh the diameter or Earth's moon and just one of 61 (or more) moons circling Saturn--has been blowing smoke rings for millennia trying to stand out and get noticed...and has finally succeeded!
One commenter on Scientific American's website lists the moons of Saturn (Titan and Enceladus) and moons of Jupiter (Callisto, Ganymede and Europa) that are spots where space exploration has found evidence that extraterrestrial life might possibly exist. I'll have to research this to see how accurate that is.
Today an article in the science journal Nature said that salty water is shooting out of Enceladus, one of Saturn's moons. And that the conditions for life to exist might lie beneath that moon's surface. But another article published alongside it argues that the water isn't salty.
Whether the water jets spewing from Enceladus's south pole are salty or not seems to be a big deal. But I don't understand why, do you? It has something to do with whether there could be an ocean under Enceladus' surface and perhaps extraterrestrial life in that ocean. Can anyone explain why the salt is so important?
Aside from the salt issue, it is confirmed true that (1) There are huge plumes of water vapor and ice crystals being ejected from Enceladus' south pole and (2) One of the outermost rings around Saturn (the E Ring) is composed of ice particles that come mostly from this these plumes emanating (vocabulary flash!) from this moon. That was discovered just a few years ago by NASA's Cassini spacecraft.
So this obscure little moon--just one-seventh the diameter or Earth's moon and just one of 61 (or more) moons circling Saturn--has been blowing smoke rings for millennia trying to stand out and get noticed...and has finally succeeded!
One commenter on Scientific American's website lists the moons of Saturn (Titan and Enceladus) and moons of Jupiter (Callisto, Ganymede and Europa) that are spots where space exploration has found evidence that extraterrestrial life might possibly exist. I'll have to research this to see how accurate that is.
Monday, June 22, 2009
Cool Planets #4: The Expanding Solar System
The solar system is expanding!
Not literally. What I mean is we keep learning that the Solar System stretches out further and further than we thought before. Starting from the center, here's what you will now find:
Sun
The 8 planets:
Not literally. What I mean is we keep learning that the Solar System stretches out further and further than we thought before. Starting from the center, here's what you will now find:
Sun
The 8 planets:
- Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune.
- Kuiper Belt (includes dwarf planets Pluto, Haumea and Makemake.)
- Scattered Disk (includes dwarf plant Eris)
- Detached Objects (includes Sedna, a likely dwarf planet)
- Oort Cloud (theoretical, not proven to exist)
- Chilly and dark out there. Very!
Wow! Now about this Oort Cloud...
- Supposedly where many comets stay most of the time.
- Extends out one-quarter of the way to Promixa Centauri, the nearest start to the sun.
- So far away that passing starts have more gravitational effect than the planets.
The Oort Cloud if it exists may be divided into:
- Hills Cloud, a disklike inner Oort Cloud.
- Outer Ort Cloud (OOC!) which is spherical.
I have decide there are two kinds of people in the world:
- Those that don't see why this is interesting.
- Those that think this is absolutely fascinating, like me, and clearly traveling in a more eccentric orbit!
Saturday, June 20, 2009
Cool Planets #3: New Asteroids
Centaurs and Trojans are zooming around the sun. (No joke!)
There are a whole lot of other blobs racing around the same orbit as Jupiter and traveling just as fast as it does. (I'm serious!)
The asteroids have been sprung loose from their old location in the gap between the orbits of Mars and Jupiter. (Well...kinda.)
Allow me to explain. Maybe you were taught that there are lots of asteroids--rocky, irregularly shaped objects--and these mostly reside in a band between the orbits of Mars and Jupiter. And that these asteroids are presumably debris that never coalesced into a planet or the result of a planet that fell apart.
Well it turns out that there are lots of asteroids and things like them all over the solar system and not just in the Mars-Jupiter gap. The ones that orbit beyond Jupiter (but inside of Neptune) are called Centaurs. They tend to be balls of frozen gas rather than rocks. Just as Jupiter and the planets beyond it are mostly made of liquid and frozen gases, while the planets inward from Jupiter are rocky.
Now a bunch of these Centaurs go around in the same orbit as Jupiter, and they are all either one-sixth of an orbit ahead of Jupiter or one-sixth of an orbit behind it. These are called Trojan Centaurs or Jupiter Trojans. Pretty darn strange if you ask me!
Why do they go around exactly 60 degrees (one-sixth of of an orbit) ahead of or behind Jupiter? Well that's called a Lagrangian Point and there are mathematics that make Lagrangian points special and help keep Trojans from getting absorbed by gravity into the main object in the orbit. Look it up if you want to know more.
These Trojans go around in a kind a swarm, where they stay generally in the same position relative to Jupiter, but move around in the swarm under continual "nudges" from the gravity of the individual Trojans and the planets.
Neptune is the other planet with known Trojans. Just six of them have been spotted. All are "ahead of" Neptune, none are in the trailing Langrangian point. But astronomers think Neptune may turn out to have ten times as many Trojans as Jupiter.
Some of Saturn's major moons have smaller Trojan moons that orbit with them. They cluster in the Lagrangian points of the major moon's orbit around Saturn (not the Lagrangian points in Saturn's orbit around the Sun).
Are there any Earth Trojans keeping us company in the Lagrangian points of our orbit around the Sun? Astronomers have looked but so far all they've found is some "Lagrangian dust".
I found all this cool new stuff out when I helped my daughter with her astronomy homework. The Solar System has "gotten" a lot more complex and mysterious since I studied it in elementary school.
It is "so last century" to think of of asteroids as an orderly procession of rocks that dutifully parade around the Sun in the gap between Mars and Jupiter. Now we know that there are lots of small rocky or icy objects orbiting everywhere from Mercury to way beyond Pluto.
And some of them do amazing stunts like "racing" Jupiter around its own orbit--all the while keeping a precise "mathematically safe distance" behind or ahead of their huge competitor. A competitor whose powerful gravity wants to suck them in and devour them in its thick soupy atmosphere.
Actually, the Jupiter Trojans are only temporarily safe, but that's another story.
There are a whole lot of other blobs racing around the same orbit as Jupiter and traveling just as fast as it does. (I'm serious!)
The asteroids have been sprung loose from their old location in the gap between the orbits of Mars and Jupiter. (Well...kinda.)
Allow me to explain. Maybe you were taught that there are lots of asteroids--rocky, irregularly shaped objects--and these mostly reside in a band between the orbits of Mars and Jupiter. And that these asteroids are presumably debris that never coalesced into a planet or the result of a planet that fell apart.
Well it turns out that there are lots of asteroids and things like them all over the solar system and not just in the Mars-Jupiter gap. The ones that orbit beyond Jupiter (but inside of Neptune) are called Centaurs. They tend to be balls of frozen gas rather than rocks. Just as Jupiter and the planets beyond it are mostly made of liquid and frozen gases, while the planets inward from Jupiter are rocky.
Now a bunch of these Centaurs go around in the same orbit as Jupiter, and they are all either one-sixth of an orbit ahead of Jupiter or one-sixth of an orbit behind it. These are called Trojan Centaurs or Jupiter Trojans. Pretty darn strange if you ask me!
Why do they go around exactly 60 degrees (one-sixth of of an orbit) ahead of or behind Jupiter? Well that's called a Lagrangian Point and there are mathematics that make Lagrangian points special and help keep Trojans from getting absorbed by gravity into the main object in the orbit. Look it up if you want to know more.
These Trojans go around in a kind a swarm, where they stay generally in the same position relative to Jupiter, but move around in the swarm under continual "nudges" from the gravity of the individual Trojans and the planets.
Neptune is the other planet with known Trojans. Just six of them have been spotted. All are "ahead of" Neptune, none are in the trailing Langrangian point. But astronomers think Neptune may turn out to have ten times as many Trojans as Jupiter.
Some of Saturn's major moons have smaller Trojan moons that orbit with them. They cluster in the Lagrangian points of the major moon's orbit around Saturn (not the Lagrangian points in Saturn's orbit around the Sun).
Are there any Earth Trojans keeping us company in the Lagrangian points of our orbit around the Sun? Astronomers have looked but so far all they've found is some "Lagrangian dust".
I found all this cool new stuff out when I helped my daughter with her astronomy homework. The Solar System has "gotten" a lot more complex and mysterious since I studied it in elementary school.
It is "so last century" to think of of asteroids as an orderly procession of rocks that dutifully parade around the Sun in the gap between Mars and Jupiter. Now we know that there are lots of small rocky or icy objects orbiting everywhere from Mercury to way beyond Pluto.
And some of them do amazing stunts like "racing" Jupiter around its own orbit--all the while keeping a precise "mathematically safe distance" behind or ahead of their huge competitor. A competitor whose powerful gravity wants to suck them in and devour them in its thick soupy atmosphere.
Actually, the Jupiter Trojans are only temporarily safe, but that's another story.
Sunday, June 14, 2009
Cool Planets #2: Watch the Moon Wiggle
I just found out the coolest thing yet about the planets and solar system! The moon rocks! Go ahead, click that link and see the video that shows it.
Or you might say the moon wiggles! This is called libration! Make that one of yourvocabulary flash cards list. Who says you can't have vocabulary learning fun?
Explanation: You already know that one side of the moon always faces the earth and the far side of the moon (erroneously called the dark side) always faces away. Well actually that's not one hundred percent accurate. Sometimes a little bit of the far side shows at the top, bottom, left or right or the moon. And of course a corresponding amount disappears temporarily on the opposide side of the moon as we look at it.
This side-to-side and top-to-bottom rocking looks like a wiggle as if the moon was hula hooping. If the moon had a ring, I bet it would spin like a hoola hoop. Moon fun. Fun moon.
Or you might say the moon wiggles! This is called libration! Make that one of your
Explanation: You already know that one side of the moon always faces the earth and the far side of the moon (erroneously called the dark side) always faces away. Well actually that's not one hundred percent accurate. Sometimes a little bit of the far side shows at the top, bottom, left or right or the moon. And of course a corresponding amount disappears temporarily on the opposide side of the moon as we look at it.
This side-to-side and top-to-bottom rocking looks like a wiggle as if the moon was hula hooping. If the moon had a ring, I bet it would spin like a hoola hoop. Moon fun. Fun moon.
Cool Planets #1: Dwarf Planets
When I was young in the early 1960s, I loved planets, the solar system, space exploration, astronautsand anything astronomy. I watched the Mercury, Gemini and Apollo space capsule launches, including the moon landings. But our knowledge was rudimentary then.
It seemed simple. There were nine planets. Jupiter had twelve moons, Saturn had nine. But none of that is true anymore, as this blog will gradually reveal. NOW...
This all wows me. How cool is it that they keep discovering new planetoids? And that there are whole bands or regions of the Solar System beyond Pluto that they are just discovering and naming?
This makes it fun for kids and kid-like objects (like myself). Never fear, there is plenty of stuff for us to discover when we grow up to be astronomers, amateur or professional.
In fact, a NASA probe is headed to meet Ceres in 2015. Stay tuned!
Learning science is fun! Science fun! Fun science!
It seemed simple. There were nine planets. Jupiter had twelve moons, Saturn had nine. But none of that is true anymore, as this blog will gradually reveal. NOW...
- There are eight planets and five dwarf planets.
- The eight planets are Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune.
- The five dwarf planets are Ceres, Pluto, Haumea, Makemake and Eris. Cool!
- Poor Pluto was recently demoted from planet to dwarf planet.
- To be a planet or dwarf, an object must orbit the Sun and be massive enough to have become rounded by the pull of its own gravity.
- To graduate from dwarf to planet, an object must have cleared its neighboring regions of small objects. (The dwarf planets still have debris in their orbital space.
- Ceres is in the asteroid belt (between the orbits of Mars and Jupiter). It has about one-third of the mass of the entire asteroid belt, just by itself. Yow!
- Pluto, Haumea and Makemake are in the area beyond the orbit of Neptune, in what is called the Kuiper Belt.
- Eris, the largest of the (current) dwarf planets orbits nearly three times the distance from the Sun as Pluto, Haumea and Makemake. This is beyond the Kuiper Belt in what is called the Scattered Disk.
This all wows me. How cool is it that they keep discovering new planetoids? And that there are whole bands or regions of the Solar System beyond Pluto that they are just discovering and naming?
This makes it fun for kids and kid-like objects (like myself). Never fear, there is plenty of stuff for us to discover when we grow up to be astronomers, amateur or professional.
In fact, a NASA probe is headed to meet Ceres in 2015. Stay tuned!
Learning science is fun! Science fun! Fun science!
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