Posted on 03/09/2018 9:43:05 AM PST by Simon Green
Although planets surround stars in the galaxy, how they form remains a subject of debate. Despite the wealth of worlds in our own solar system, scientists still aren't certain how planets are built. Currently, two theories are duking it out for the role of champion.
The first and most widely accepted, core accretion, works well with the formation of the terrestrial planets but has problems with giant planets such as Uranus. The second, the disk instability method, may account for the creation of giant planets.
"What separates the ice giants from the gas giants is their formation history: during core growth, the former never exceeded [critical mass] in a full gas disk," wrote researchers Renata Frelikh and Ruth Murray-Clay in a research paper. The core accretion model
Approximately 4.6 billion years ago, the solar system was a cloud of dust and gas known as a solar nebula. Gravity collapsed the material in on itself as it began to spin, forming the sun in the center of the nebula.
With the rise of the sun, the remaining material began to clump together. Small particles drew together, bound by the force of gravity, into larger particles. The solar wind swept away lighter elements, such as hydrogen and helium, from the closer regions, leaving only heavy, rocky materials to create terrestrial worlds. But farther away, the solar winds had less impact on lighter elements, allowing them to coalesce into gas giants such as Uranus. In this way, asteroids, comets, planets, and moons were created.
(Excerpt) Read more at space.com ...
Just here for the jokes....
Our solar system is a late comer in a galaxy which had metal-rich systems billions of years earlier. Assuming life happens elsewhere, by whatever means, there were probably civilizations with billion-year histories already in place before the solar system formed. In that span of time the possible extent of technological development is virtually unlimited. For all we know, the solar system and our Earth-Moon habitat was artificially crafted from natural elements like a Japanese garden.
That scenario might be the only explanation for the Moon, which otherwise should not exist at all, especially where it is now.
Our built in asteroid/comet catcher.
The problem with that is the universe is just too small and way too young for for random chance to be a mechanism. DNA is based on a 22 “letter” code, and therefore cannot evolve. The math on these theories blew up 40 years ago. That’s why many microbiologists and organic chemist skirt the issue, (to protect their careers.) The nature of information as well as the mathematical study of randomness completely destroy the theory. Not to mention that it violates basic physical laws....just sayin.
With this title, 100+ posts are almost guaranteed...
The comic restraint so far is surprising.
About 1960-61. :>)
“Gustave Holst’s ‘The Planets’ has seven movements.
...
Uranus was characterized as “Uranus, the Magician”; boisterous, powerful and icy.”
Well if you want information on the subject let me get you an expert. Barry...........Barry Hussein! Get your lazy ass over here, someone wants you.
Fry: ... hey, as long as you don’t make me smell Uranus.
Leela: I don’t get it.
Professor Hubert Farnsworth: I’m sorry, Fry, but astronomers renamed Uranus in 2620 to end that stupid joke once and for all.
Fry: Oh. What’s it called now?
Professor Hubert Farnsworth: Urrectum. Here, let me locate it for you.
Fry: No, no, I, I think I’ll just smell around a bit over here.
I don’t know. How did yours?
Not to mention the source of our tides, which help keep the ocean healthy. I haven’t studied this aspect, but the Moon probably is beneficial from the standpoint of rotational stability, since it carries the vast majority of the angular momentum of the Earth-Moon system.
The far side would be an ideal location for all manner of telescopes, if we had access. Maybe Trump can make a deal.
I said nothing about the mechanism of origin of life, or evolution. We know very little about those subjects and most of what we do know is probably wrong.
Hi jennifer lawrence! *waves*
The answer is McDonalds, Burger King, Taco Bell...
Thanks Simon Green.
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It is? How do you know? Did you measure??
And more importantly, are there Klingons surrounding it?
Thanks Simon Green.
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Retrograde satellites lose momentum to the parent body and slowly spiral inward, which puts an upper limit (possibly not considered by these researchers) on the length of time the retrograde moons have spent as satellites, and obviously, will spend as satellites.Newfound Moons Tell Secrets of Solar SystemThe fact that most of the satellites' orbits are retrograde and eccentric speaks volumes about their origins: They had to have come from elsewhere, and been captured by the planets at some point. If they formed at the same time as the planets, from the spinning nebular disk, their orbits would be nearly circular and in the same direction as the planets' rotation, like the "regular" moons... In the case of the irregular satellites, they could not have shifted from an orbit around the Sun to an orbit around one of the giant planets without slowing down -- through friction in an atmosphere, perhaps; the influence of gravity; or a collision with another object... But there are two other possibilities for capture, Dr. Nesvorny said. One is that rapid growth of the core led to a corresponding increase in gravity, enough to pull down a nearby object. The other is that captured objects were a result of a collision between two planetesimals, the force of the collision being enough to dissipate the energy of at least one of them. Either of these two theories may be a more likely explanation for the satellites of Uranus and Neptune, which formed differently from Jupiter and Saturn, without the large amounts of gas.
by Henry Fountain
August 12, 2003
It's remarkable and ironic how using logic to proceed from invalid assumptions leads later people to surprises when actual observations are done in attempts to verify the old models.How Jupiter Got BigThe traditional view is that Jupiter first formed a rocky core, several times the size of Earth, which then attracted a still larger outer envelope of gas. This process is known as "accretion." But there are problems with this model. The major problem is that if the large, gaseous planet did form by the gradual accretion of material, it would have taken a very long time to develop. Current estimates range between 10 million and 1 billion years. However, recent observations of distant stars suggest that planets have at most a few million years or less to gather up as much dust and gas as they can before the protoplanetary disk that feeds them disappears.
by Leslie Mullen
June 2, 2002
Jupiter gave birth to Uranus and NeptuneNot too long ago, scientists regarded the orbits that the planets circle our Sun as being the ones they were born in. Now they are realising that this is not the case. Uranus and Neptune may have migrated outwards and Jupiter may have come in from the outer cold. Scientists have always been slightly puzzled by the positions of Uranus and Neptune because in their present locations it would have taken longer than the age of the Solar System for them to form. Scientists from Queen's University suggest that the four giant planets started out as rocky cores in the Jupiter-Saturn region, and that the cores of Uranus and Neptune were tossed out by Jupiter's and Saturn's gravity.
by Dr David Whitehouse
(circa 2001)Jupiter's Composition Throws Planet-formation Theories into DisarrayExamining four-year-old data, researchers have found significantly elevated levels of argon, krypton and xenon in Jupiter's atmosphere that may force a rethinking of theories about how the planet, and possibly the entire solar system, formed. Prevailing theories of planetary formation hold that the sun gathered itself together in the center of a pancake-shaped disk of gas and dust, then the planets begin to take shape by cleaning up the leftovers. In Jupiter's current orbit, 5 astronomical units from the sun, temperatures are too warm for the planetesimals to have trapped the noble gases. Only in the Kuiper belt -- a frigid region of the solar system more than 40 AU from the sun -- could planetesimals have trapped argon, krypton and xenon.
by Robert Roy Britt
Nov 17 1999
While lead researcher Tobias Owen does not put much stock in the idea that Jupiter might have migrated inward to its present position, other scientists on the team say the idea merits consideration. Owen expects the probes will find similarly high levels of noble gases in Saturn, Uranus and Neptune. Hints of these gases have even been found in the thick atmosphere of Venus, another planet now begging more study.Did Jupiter Bully Other Planets in Sibling Rivalry?One possible explanation, discussed in Thursday's issue of the journal Nature, is that Uranus and Neptune formed much closer to the center of the action than their current positions might indicate. In this scheme, Jupiter and Saturn were bullies of a protoplanetary playground, shoving the other two future giants out of the way.
by Robert Roy Britt
8 December 1999
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