Sunday, June 5, 2016

HUMANS IN MARS - Elon Musk Is Sending Humans To Mars In 2024

Elon Musk Is Sending Humans To Mars In 2024:



Elon Musk has announced ambitious plans to send humans to Mars by 2024. Image: Artist's drawing of the Dragon capsule at Mars. SpaceX.


Do you get the feeling that Elon Musk likes making bold announcements?



Every space enthusiast's favorite billionaire-turned-space-entrepreneur has just announced that he hopes his company, SpaceX, will send humans to Mars in 2024. If this sounds outrageous, you're not keeping up with developments in commercial space. If this sounds a little bit ambitious, you're probably right. But ambition is what Musk is all about.



“I think, if things go according to plan, we should be able to launch people probably in 2024, with arrival in 2025,” Musk said.



Musk, of course, is the Paypal co-founder who went on to start the Tesla electric car company, and SpaceX, the private space company. SpaceX has achieved a lot in its short time, including developing the Falcon re-usable rocket and the Dragon delivery and re-supply craft. With an even more powerful rocket in development, the Falcon Heavy, it's fair to say that Musk has a track record of delivering on ambitious projects.



Musk's announcement, at the Code Conference 2016 in Los Angeles, is definitely exciting news. It comes on the heels of an announcement earlier this spring stating that SpaceX will send a Dragon capsule to Mars in 2018, albeit one with no personnel on board. Musk founded SpaceX in 2002 with the goal of advancing the technologies required to establish a human colony on Mars, so everything seems to be going according to plan.



But a colony needs supplies, and with that in mind Musk also announced the intention of sending a craft to Mars every two years, in order to establish a supply line.



“The basic game plan is we’re going to send a mission to Mars with every Mars opportunity from 2018 onwards,” Musk said Wednesday night. “They occur approximately every 26 months. We’re establishing cargo flights to Mars that people can count on for cargo.”



“That’s what’s necessary to create a self-sustaining, or a growing, city on Mars,” he added.



Of course, there's lots of work to be done yet. Currently, there is no rocket powerful enough for a mission like this. The most powerful rocket ever built was the Saturn V, used to get the Apollo mission to the Moon. That was 50 years ago.







NASA's Space Launch System will have the power for a Mars mission, but that's a ways away, and they probably won't be giving SpaceX one. SpaceX has developed the Falcon rocket, and are working on the Falcon Heavy, but it won't be enough to establish and maintain a presence on Mars. Still, this obstacle is anything but insurmountable, even though there has been no announcement on the building of this required rocket.



This whole endeavour will be enormously expensive, of course. But with a growing customer base for SpaceX, including the US military, NASA, and commercial communications customers, it seems like the money will be there.



As for the timeline, Musk acknowledges that it is a fairly aggressive one. “When I cite a schedule, it’s actually a schedule I think is true,” Musk said. “It’s not some fake schedule I don’t think is true. I may be delusional. That is entirely possible, and maybe it’s happened from time to time, but it’s never some knowingly fake deadline ever.”



The announcement itself sounds so simple. But Musk knows, as does everyone else involved in planning these kinds of missions, that there is an enormous amount of complex detail behind it all. The food required, the energy needed, and all of the other things that a sustained human presence on Mars will require in order to succeed, are all waiting to be addressed. Musk plans to address some of these details in September at the International Astronautical Congress in Guadalajara, Mexico.







Musk generates a lot of headlines when he makes these announcements. That's as it should be. But there are other plans to reach Mars, too.



NASA is planning to get to Mars, but they're going about it differently. They plan on using their SLS and the Orion to explore what's called cis-lunar space, near the Moon, to test deep space operations, life support systems, solar-electric thrusters, and habitats. All of this activity could start as soon as 2021, and would support an eventual round-trip mission to Mars in the 2030s.



For a long time, it seemed that a mission to Mars was out of reach, off the table, and nobody was really talking about it. Now, we have two separate programs aiming toward an eventual mission to Mars.



Could this be the new space race? But instead of capitalism versus communism, as in the original space race, it's government versus private?



In the end, it won't really matter. We just want someone to get there. And we want an established presence. A colony.



Our survival may depend on it.









The post Elon Musk Is Sending Humans To Mars In 2024 appeared first on Universe Today.

JUPITER PLANET - Take A Look Beneath Jupiter’s Clouds

Take A Look Beneath Jupiter’s Clouds:



This radio image of Jupiter was captured by the VLA in New Mexico. The three colors in the picture correspond to three different radio wavelengths: 2 cm in blue, 3 cm in gold, and 6 cm in red. Synchrotron radiation produces the pink glow around the planet. Image: Imke de Pater, Michael H. Wong (UC Berkeley), Robert J. Sault (Univ. Melbourne).


[embed]https://www.youtube.com/watch?v=Sxndu3hVg2o[/embed]Jupiter's Great Red Spot is easily one of the most iconic images in our Solar System, next to Saturn's rings. The Great Red Spot and the cloud bands that surround it are easily seen with a backyard telescope. But much of what goes on behind the scenes on Jupiter has remained hidden.



When the Juno spacecraft arrives at Jupiter in about a month from now, we will be gifted some spectacular images from the cameras aboard that craft. To whet our appetites until then, astronomers using the Karl G. Jansky Very Large Array in New Mexico have created a detailed radio map of the gas giant. By using the 'scope to peer 100 km past the cloud tops, the team has brought into view a mostly unexplored region of Jupiter's atmosphere.



The team of researchers from UC Berkeley used the updated capabilities of the VLA to do this work. The VLA had its sensitivity improved by a factor of ten. “These Jupiter maps really show the power of the upgrades to the VLA,” said Bryan Butler, a member of the team and staff astronomer at the National Radio Astronomy Observatory in Socorro, New Mexico.



In the video below, two overlaid maps alternate back and forth. One is optical and the other is a radio image. Together, the two show some of the atmospheric activity that takes place under the cloud tops.



[embed]https://www.youtube.com/watch?v=AWz2cn0j25Y[/embed]



The team measured Jupiter's radio emissions in wavelengths that pass through clouds. That allowed them to see 100 km (60 miles) deep into the atmosphere. This allowed them to not only determine the quantity and depth of ammonia in the atmosphere, but also to learn something about how Jupiter's internal heat source drives global circulation and cloud formation.



“We in essence created a three-dimensional picture of ammonia gas in Jupiter’s atmosphere, which reveals upward and downward motions within the turbulent atmosphere,” said principal author Imke de Pater, a UC Berkeley professor of astronomy.



These results will also help shed light on how other gas giants behave. Not just for Saturn, Uranus, and Neptune, but for all the gas giant exoplanets that have been discovered. de Pater said that the map bears a striking resemblance to visible-light images taken by amateur astronomers and the Hubble Space Telescope.







In the radio map, ammonia-rich gases are shown rising and forming into the upper cloud layers. The clouds are easily seen from Earth-bound telescopes. Ammonia-poor air is also shown sinking into the planet's atmosphere. Hotspots, which appear bright in radio and thermal images of Jupiter, are regions of less ammonia that encircle the planet north of the equator. In between those hotspots, rich upwellings deliver ammonia from deeper in the atmosphere.



“With radio, we can peer through the clouds and see that those hotspots are interleaved with plumes of ammonia rising from deep in the planet, tracing the vertical undulations of an equatorial wave system,” said UC Berkeley research astronomer Michael Wong. Very nice.



“We now see high ammonia levels like those detected by Galileo from over 100 kilometers deep, where the pressure is about eight times Earth’s atmospheric pressure, all the way up to the cloud condensation levels,” de Pater said.







This is fascinating stuff, and not just because it's visually stunning. What this team is doing with the improved VLA dovetails nicely with what Juno will be doing when it gets set up in its orbit around Jupiter. One of Juno's aims is to use microwaves to measure the water content in the atmosphere, in the same way that the VLA was used to measure ammonia.



In fact, the team will be pointing the VLA at Jupiter again, at the same time as Juno is detecting water. “Maps like ours can help put their data into the bigger picture of what’s happening in Jupiter’s atmosphere,” de Pater said.



The team was able to model the atmosphere by observing it over the entire frequency range between 4 and 18 gigahertz (1.7 – 7 centimeter wavelength), which enabled them to carefully model the atmosphere, according to David DeBoer, a research astronomer with UC Berkeley’s Radio Astronomy Laboratory.



“We now see fine structure in the 12 to 18 gigahertz band, much like we see in the visible, especially near the Great Red Spot, where we see a lot of little curly features,” Wong said. “Those trace really complex upwelling and downwelling motions there.”



The detailed observations the team obtained also help resolve a discrepancy in ammonia measurements in Jupiter's atmosphere. In 1995, the Galileo probe measured ammonia at 4.5 times greater than the Sun, when it plunged through the atmosphere. VLA measurements prior to 2004 showed much less ammonia than that.



Study co-author Robert Sault, of the University of Melbourne in Australia, explained how this latest imaging solved that mystery. "“Jupiter’s rotation once every 10 hours usually blurs radio maps, because these maps take many hours to observe. But we have developed a technique to prevent this and so avoid confusing together the upwelling and downwelling ammonia flows, which had led to the earlier underestimate.”



Overall, it's exciting times for studying Jupiter. The Juno mission promises to be as full of surprises as New Horizons was (we hope.)



Universe Today has covered the Juno mission, including an interview with the Principal Investigator, Scott Bolton.



The team's paper is published in the journal Science, here.



The post Take A Look Beneath Jupiter’s Clouds appeared first on Universe Today.

NASA IMAGE - Cat s Eye Wide and Deep

Cat s Eye Wide and Deep:

Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.

2016 May 28


See Explanation. Clicking on the picture will download the highest resolution version available.


Cat's Eye Wide and Deep

Image Credit & Copyright: Josh Smith


Explanation: The Cat's Eye Nebula (NGC 6543) is one of the best known planetary nebulae in the sky. Its more familiar outlines are seen in the brighter central region of the nebula in this impressive wide-angle view. But the composite image combines many short and long exposures to also reveal an extremely faint outer halo. At an estimated distance of 3,000 light-years, the faint outer halo is over 5 light-years across. Planetary nebulae have long been appreciated as a final phase in the life of a sun-like star. More recently, some planetary nebulae are found to have halos like this one, likely formed of material shrugged off during earlier episodes in the star's evolution. While the planetary nebula phase is thought to last for around 10,000 years, astronomers estimate the age of the outer filamentary portions of this halo to be 50,000 to 90,000 years. Visible on the left, some 50 million light-years beyond the watchful planetary nebula, lies spiral galaxy NGC 6552.

Tomorrow's picture: mars approaches



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Authors & editors: Robert Nemiroff (MTU) & Jerry Bonnell (UMCP)
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& Michigan Tech. U.

MARS PLANET - Valles Marineris: The Grand Canyon of Mars

Valles Marineris: The Grand Canyon of Mars:

Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.

2016 May 29


See Explanation. Clicking on the picture will download the highest resolution version available.


Valles Marineris: The Grand Canyon of Mars

Image Credit: Viking Project, USGS, NASA


Explanation: Mars will look good in Earth's skies over the next few days -- but not this good. To get a view this amazing, a spacecraft had to actually visit the red planet. Running across the image center, though, is one the largest canyons in the Solar System. Named Valles Marineris, the grand valley extends over 3,000 kilometers long, spans as much as 600 kilometers across, and delves as much as 8 kilometers deep. By comparison, the Earth's Grand Canyon in Arizona, USA is 800 kilometers long, 30 kilometers across, and 1.8 kilometers deep. The origin of the Valles Marineris remains unknown, although a leading hypothesis holds that it started as a crack billions of years ago as the planet cooled. Several geologic processes have been identified in the canyon. The featured mosaic was created from over 100 images of Mars taken by Viking Orbiters in the 1970s. Tomorrow, Mars and Earth will pass the closest in 11 years, resulting in the red planet being quite noticeable toward the southeast after sunset.

Tomorrow's picture: watch the universe evolve



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Authors & editors: Robert Nemiroff (MTU) & Jerry Bonnell (UMCP)
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NASA Web Privacy Policy and Important Notices
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NASA IMAGE - Stars and Gas of the Running Chicken Nebula

Stars and Gas of the Running Chicken Nebula:

Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.

2016 May 31


See Explanation. Clicking on the picture will download the highest resolution version available.


Stars and Gas of the Running Chicken Nebula

Image Credit & Copyright: Andrew Campbell


Explanation: To some, it looks like a giant chicken running across the sky. To others, it looks like a gaseous nebula where star formation takes place. Cataloged as IC 2944, the Running Chicken Nebula spans about 100 light years and lies about 6,000 light years away toward the constellation of the Centaur (Centaurus). The featured image, shown in scientifically assigned colors, was captured recently in an 11-hour exposure from a backyard near Melbourne, Australia. Two star clusters are visible: the Pearl Cluster seen on the far left, and Collinder 249 embedded in the nebula's glowing gas. Although difficult to discern here, several dark molecular clouds with distinct shapes can be found inside the nebula.

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Tomorrow's picture: star puff



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Authors & editors: Robert Nemiroff (MTU) & Jerry Bonnell (UMCP)
NASA Official: Phillip Newman Specific rights apply.
NASA Web Privacy Policy and Important Notices
A service of: ASD at NASA / GSFC
& Michigan Tech. U.

NASA IMAGE - Three Planets from Pic du Midi

Three Planets from Pic du Midi:

Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.

2016 June 2


See Explanation. Clicking on the picture will download the highest resolution version available.
Explanation: Seen any planets lately? All three planets now shining brightly in the night sky are imaged in these panels, captured last week with the 1 meter telescope at Pic du Midi Observatory in the French Pyrenees. Near opposition and closest to Earth on May 30, Mars is presently offering the best ground-based photo-ops in the last decade. The sharp image finds clouds above the Red Planet's north pole (top) and towering volcanos near its right limb. Saturn reaches its own opposition tonight, its bright rings and gaps clearly revealed in the telescopic portrait. Jupiter is currently highest during the evening twilight and shows off its planet-girdling cloud bands and Great Red Spot in this scene. Of course close-up images of the ruling gas giant will follow the July arrival of the solar-powered Juno spacecraft and JunoCam.

NASA IMAGE - NGC 4631: The Whale Galaxy

NGC 4631: The Whale Galaxy:

Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.

2016 June 3


See Explanation. Clicking on the picture will download the highest resolution version available.
Explanation: NGC 4631 is a big beautiful spiral galaxy. Seen edge-on, it lies only 25 million light-years away in the well-trained northern constellation Canes Venatici. The galaxy's slightly distorted wedge shape suggests to some a cosmic herring and to others its popular moniker, The Whale Galaxy. Either way, it is similar in size to our own Milky Way. In this sharp color image, the galaxy's yellowish core, dark dust clouds, bright blue star clusters, and red star forming regions are easy to spot. A companion galaxy, the small elliptical NGC 4627 is just above the Whale Galaxy. Faint star streams seen in deep images are the remnants of small companion galaxies disrupted by repeated encounters with the Whale in the distant past. The Whale Galaxy is also known to have spouted a halo of hot gas glowing in X-rays.

NASA IMAGE -The Little Fox and the Giant Stars

The Little Fox and the Giant Stars: New stars are the lifeblood of our galaxy, and there is enough material revealed by this Herschel infrared image to build stars for millions of years to come.


Original enclosures:


NASA IMAGE -The Dark Side of Pluto

The Dark Side of Pluto: NASA’s New Horizons spacecraft took this stunning image of Pluto only a few minutes after closest approach on July 14, 2015. The image was obtained at a high phase angle –that is, with the sun on the other side of Pluto, as viewed by New Horizons. Seen here, sunlight filters through and illuminates Pluto’s complex atmospheric haze layers.


Original enclosures:


NASA IMAGE - Hubble Rocks with a Heavy-Metal Home

Hubble Rocks with a Heavy-Metal Home: This 10.5-billion-year-old globular cluster, NGC 6496, is home to heavy-metal stars of a celestial kind! The stars comprising this spectacular spherical cluster are enriched with much higher proportions of metals — elements heavier than hydrogen and helium are curiously known as metals in astronomy — than stars found in similar clusters.


Original enclosures:


Thursday, June 2, 2016

EINSTEIN RING - New ‘Einstein Ring’ Discovered By Dark Energy Camera

New ‘Einstein Ring’ Discovered By Dark Energy Camera:



The "Canarias Einstein Ring." The green-blue ring is the source galaxy, the red one in the middle is the lens galaxy. The lens galaxy has such strong gravity, that it distorts the light from the source galaxy into a ring. Because the two galaxies are aligned, the source galaxy appears almost circular. Image: This composite image is made up from several images taken with the DECam camera on the Blanco 4m telescope at the Cerro Tololo Observatory in Chile.


A rare object called an Einstein Ring has been discovered by a team in the Stellar Populations group at the Instituto de Astrofísica de Canarias (IAC) in Spain. An Einstein Ring is a specific type of gravitational lensing.



Einstein's Theory of General Relativity predicted the phenomena of gravitational lensing. Gravitational lensing tells us that instead of travelling in a straight line, light from a source can be bent by a massive object, like a black hole or a galaxy, which itself bends space time.



Einstein's General Relativity was published in 1915, but a few years before that, in 1912, Einstein predicted the bending of light. Russian physicist Orest Chwolson was the first to mention the ring effect in scientific literature in 1924, which is why the rings are also called Einstein-Chwolson rings.



Gravitational lensing is fairly well-known, and many gravitational lenses have been observed. Einstein rings are rarer, because the observer, source, and lens all have to be aligned. Einstein himself thought that one would never be observed at all. "Of course, there is no hope of observing this phenomenon directly," Einstein wrote in 1936.



[embed]https://www.youtube.com/watch?v=H1bZcdE9zP0[/embed]



The team behind the recent discovery was led by PhD student Margherita Bettinelli at the University of La Laguna, and Antonio Aparicio and Sebastian Hidalgo of the Stellar Populations group at the Instituto de Astrofísica de Canarias (IAC) in Spain. Because of the rarity of these objects, and the strong scientific interest in them, this one was given a name: The Canarias Einstein Ring.



There are three components to an Einstein Ring. The first is the observer, which in this case means telescopes here on Earth. The second is the lens galaxy, a massive galaxy with enormous gravity. This gravity warps space-time so that not only are objects drawn to it, but light itself is forced to travel along a curved path. The lens lies between Earth and the third component, the source galaxy. The light from the source galaxy is bent into a ring form by the power of the lens galaxy.



When all three components are aligned precisely, which is very rare, the light from the source galaxy is formed into a circle with the lens galaxy right in the centre. The circle won't be perfect; it will have irregularities that reflect irregularities in the gravitational force of the lens galaxy.







The objects are more than just pretty artifacts of nature. They can tell scientists things about the nature of the lens galaxy. Antonio Aparicio, one of the IAC astrophysicists involved in the research said, "Studying these phenomena gives us especially relevant information about the composition of the source galaxy, and also about the structure of the gravitational field and of the dark matter in the lens galaxy."



Looking at these objects is like looking back in time, too. The source galaxy is 10 billion light years from Earth. Expansion of the Universe means that the light has taken 8.5 billion light years to reach us. That's why the ring is blue; that long ago, the source galaxy was young, full of hot blue stars.



The lens itself is much closer to us, but still very distant. It's 6 billion light years away. Star formation in that galaxy likely came to a halt, and its stellar population is now old.



The discovery of the Canarias Einstein Ring was a happy accident. Bettinelli was pouring over data from what's known as the Dark Energy Camera (DECam) of the 4m Blanco Telescope at the Cerro Tololo Observatory, in Chile. She was studying the stellar population of the Sculptor dwarf galaxy for her PhD when the Einstein Ring caught her attention. Other members of the Stellar Population Group then used OSIRIS spectrograph on the Gran Telescopio CANARIAS (GTC) to observe and analyze it further.

















The post New ‘Einstein Ring’ Discovered By Dark Energy Camera appeared first on Universe Today.

METEORITE BLADE - -Tutankhamun’s Meteorite Blade

Tutankhamun’s Meteorite Blade:



The Egyptian Pyramids; instantly recognizable to almost anyone. Image: Armstrong White, CC BY 2.0


The spread of metallurgy in different civilizations is a keen point of interest for historians and archaeologists. It helps chart the rise and fall of different cultures. There are even names for the different ages corresponding to increasingly sophisticated metallurgical technologies: the Stone Age, the Bronze Age, and the Iron Age.



But sometimes, a piece of evidence surfaces that doesn't fit our understanding of a civilization.



[embed]https://www.youtube.com/watch? Probably the most iconic ancient civilization in all of history is ancient Egypt. Its pyramids are instantly recognizable to almost anyone. When King Tutankhamun's almost intact tomb was discovered in 1922, it was a treasure trove of artifacts. And though the tomb, and King Tut, are most well-known for the golden death mask, it's another, little-known artifact that has perhaps the most intriguing story: King Tut's iron dagger.







King Tut's iron-bladed dagger wasn't discovered until 1925, three years after the tomb was discovered. It was hidden in the wrappings surrounding Tut's mummy. It's mere existence was a puzzle, because King Tut reigned in 1332–1323 BC, 600 years before the Egyptians developed iron smelting technology.







It was long thought, but never proven, that the blade may be made of meteorite iron. In the past, tests have produced inconclusive results. But according to a new study led by Daniela Comelli, of the Polytechnic University of Milan, and published in the Journal of Meteoritics and Planetary Science, there is no doubt that a meteorite was the source of iron for the blade.



The team of scientists behind the study used a technique called x-ray fluorescence spectrometry to determine the chemical composition of the blade. This technique aims x-rays at an artifact, then determines its composition by the spectrum of colors given off. Those results were then compared with 11 other meteorites.



In the dagger's case, the results indicated Fe plus 10.8 wt% Ni and 0.58 wt% Co. This couldn't be a coincidence, since iron meteorites are mostly made of Fe (Iron) and Ni (Nickel), with minor quantities of Co (Cobalt), P (Phosphorus), S (Sulphur), and C (Carbon). Iron found in the Earth's crust has almost no Ni content.



Testing of Egyptian artifacts is a tricky business. Egypt is highly protective of their archaeological resources. This study was possible only because of advances in portable x-ray fluorescence spectrometry, which meant the dagger didn't have to be taken to a lab and could be tested at the Egyptian Museum of Cairo.



Iron objects were rare in Egypt at that time, and were considered more valuable than gold. They were mostly decorative, probably because ancient Egyptians found iron very difficult to work. It requires a very high heat to work with, which was not possible in ancient Egypt.







Even without the ability to heat and work iron, a great deal of craftsmanship went into the blade. The dagger itself had to be hammered into shape, and it features a decorated golden handle and a rounded rock crystal knob. It's golden sheath is decorated with a jackal's head and a pattern of feathers and lilies.



Ancient Egyptians probably new what they were working with. They called meteorite iron from the sky in one hieroglyph. Whether they knew with absolute certainty that their iron meteorites came from the sky, and what that might have meant, they did value the iron. As the authors of the study say, "...our study confirms that ancient Egyptians attributed great value to meteoritic iron for the production of precious objects."



The authors go on to say, "Moreover, the high manufacturing quality of Tutankhamun's dagger blade, in comparison with other simple-shaped meteoritic iron artifacts, suggests a significant mastery of ironworking in Tutankhamun's time."





The post Tutankhamun’s Meteorite Blade appeared first on Universe Today.

MOON'S WATER - Scientists Identify the Source of the Moon’s Water

Scientists Identify the Source of the Moon’s Water:



New research finds that asteroids delivered as much 80 percent of the Moon's water. Credit: LPI/David A. Kring


Over the course of the past few decades, our ongoing exploration the Solar System has revealed some surprising discoveries. For example, while we have yet to find life beyond our planet, we have discovered that the elements necessary for life (i.e organic molecules, volatile elements, and water) are a lot more plentiful than previously thought. In the 1960's, it was theorized that water ice could exist on the Moon; and by the next decade, sample return missions and probes were confirming this.

Since that time, a great deal more water has been discovered, which has led to a debate within the scientific community as to where it all came from. Was it the result of in-situ production, or was it delivered to the surface by water-bearing comets, asteroids and meteorites? According to a recent study produced by a team of scientists from the UK, US and France, the majority of the Moon's water appears to have come from meteorites that delivered water to Earth and the Moon billions of years ago.

For the sake of their study, which appeared recently in Nature Communications, the international research team examined the samples of lunar rock and soil that were returned by the Apollo missions. When these samples were originally examined upon their return to Earth, it was assumed that the trace of amounts of water they contained were the result of contamination from Earth's atmosphere since the containers in which the Moon rocks were brought home weren't airtight. The Moon, it was widely believed, was bone dry.

However, a 2008 study revealed that the samples of volcanic glass beads contained water molecules (46 parts per million), as well as various volatile elements (chlorine, fluoride and sulfur) that could not have been the result of contamination. This was followed up by the deployment of the Lunar Reconnaissance Orbiter (LRO) and the Lunar Crater Observation and Sensing Satellite (LCROSS) in 2009, which discovered abundant supplies of water around the southern polar region,

However, that which was discovered on the surface paled in comparison the water that was discovered beneath it. Evidence of water in the interior was first revealed by the ISRO's Chandrayaan-1 lunar orbiter - which carried the NASA's Moon Mineralogy Mapper (M3) and delivered it to the surface. Analysis of this and other data has showed that water in the Moon's interior is up to a million times more abundant than what's on the surface.

The presence of so much water beneath the surface has begged the question, where did it all come from? Whereas water that exists on the Moon's surface in lunar regolith appears to be the result of interaction with solar wind, this cannot account for the abundant sources deep underground. A previous study suggested that it came from Earth, as the leading theory for the Moon's formation is that a large Mars-sized body impacted our nascent planet about 4.5 billion years ago, and the resulting debris formed the Moon. The similarity between water isotopes on both bodies seems to support that theory.

However, according to Dr. David A. Kring, a member of the research team that was led by Jessica Barnes from Open University, this explanation can only account for about a quarter of the water inside the moon. This, apparently, is due to the fact that most of the water would not have survived the processes involved in the formation of the Moon, and keep the same ratio of hydrogen isotopes.

Instead, Kring and his colleagues examined the possibility that water-bearing meteorites delivered water to both (hence the similar isotopes) after the Moon had formed. As Dr. Kring told Universe Today via email:

"The current study utilized analyses of lunar samples that had been collected by the Apollo astronauts, because those samples provide the best measure of the water inside the Moon. We compared those analyses with analyses of meteoritic samples from asteroids and spacecraft analyses of comets."
By comparing the ratios of hydrogen to deuterium (aka. "heavy hydrogen") from the Apollo samples and known comets, they determined that a combination of primitive meteorites (carbonaceous chondrite-type) were responsible for the majority of water to be found in the Moon's interior today. In addition, they concluded that these types of comets played an important role when it comes to the origins of water in the inner Solar System.



For some time, scientists have argued that the abundance of water on Earth may be due in part to impacts from comets, trans-Neptunian objects or water-rich meteoroids. Here too, this was based on the fact that the ratio of the hydrogen isotopes (deuterium and protium) in asteroids like 67P/Churyumov-Gerasimenko revealed a similar percentage of impurities to carbon-rich chondrites that were found in the Earth's coeans.

But how much of Earth's water was delivered, how much was produced indigenously, and whether or not the Moon was formed with its water already there, have remained the subject of much scholarly debate. Thank to this latest study, we may now have a better idea of how and when meteorites delivered water to both bodies, thus giving us a better understanding of the origins of water in the inner Solar System.

"Some meteoritic samples of asteroids contain up to 20% water," said Kring. "That reservoir of material – that is asteroids – are closer to the Earth-Moon system and, logically, have always been a good candidate source for the water in the Earth-Moon system. The current study shows that to be true. That water was apparently delivered 4.5 to 4.3 billion years ago."

The existence of water on the Moon has always been a source of excitement, particularly to those who hope to see a lunar base established there someday. By knowing the source of that water, we can also come to know more about the history of the Solar System and how it came to be. It will also come in handy when it comes time to search for other sources of water, which will always be a factor when trying to establishing outposts and even colonies throughout the Solar System.
Further Reading: Nature Communications

The post Scientists Identify the Source of the Moon’s Water appeared first on Universe Today.

SOLAR SYSTEM - What Are Planetary Transits?

What Are Planetary Transits?:

Thanks to Ptolemy and his cronies, everyone used to think that the Earth was the center of the Solar System, with the Sun, planets and even the stars orbiting around it on a series of concentric crystal spheres. It was a clever idea, and explained the motions of the planets… sort of.

Then Copernicus figured out in 1543, that the Earth isn’t the centre of the Solar System. In fact, it’s just one planet in a vast Solar System, with objects whirling and whirling around the Sun.

With the structure of the Solar System figured out, and the crystal sphere idea in the garbage, astronomers still had a big unknown: how big is the Solar System?

Was it a few million kilometers across, or hundreds of millions. How big is the Sun? How far away is Venus?

Astronomers needed some kind of cosmic yardstick to measure everything against. Figure out one piece of the puzzle, and then you could measure everything else in relation.

In 1627, Johannes Kepler figured out that the motion of Venus was predictable, and that Venus would pass in front of the Sun in 1631, probably in the afternoon.

A timelapse of Mercury transiting across the face of the Sun. Credit: NASA
A timelapse of Mercury transiting across the face of the Sun. Credit: NASA
This is known as a “transit” of Venus.

The first crude measurements of Venus’ motion across the Sun were made in 1639 by Jeremiah Horrocks and William Crabtree from two different spots in England. And with these two observations, they were able to calculate the geometry between the Earth, Venus and the Sun.

If you recall all those memories you’re repressing from your high school geometry, once you’ve got an angle and a side of a triangle, you can work out all the other parts of the triangle. Horrocks and Crabtree worked out the distance from the Earth to the Sun within about 2/3rd accuracy. Not bad, considering the fact that astronomers literally had no idea before this point.

Following on from this observation, astronomers returned to their telescopes with each transit of Venus, better refining their calculations, and eventually settling on the current distance of about 150 million kilometers.

The 1882 transit of Venus.
The 1882 transit of Venus.
From here on Earth, we can see a few objects pass in front of the Sun: Venus, Mercury and the Moon.

Venus transits are the most rare, happening two times every 108 years or so. Mercury transits happen more often, about a dozen times a century. And a transit of the Moon, also known as a solar eclipse, happens a few times a year, on average.

It’s all a matter of perspective. If you’re standing on the Moon, you might see the Earth pass in front of the Sun. We’d call that a lunar eclipse, while the lunatics would call it an Earth transit.

We can also see transits in other parts of the Solar System, like when moons pass in front of planets. For example, if you have a small telescope, you can see when Jupiter’s larger moons pass in front of the planet from our perspective.

One of the questions you might have, though, is why don’t these transits happen more often. Why don’t we see a Mercury or Venus transit every time they line up with us and the Sun.

This is because the planets aren’t exactly lined up at the same angle towards the Sun. All of the planets are inclined at an angle that takes them above or below the Sun at various points of their orbit.

For example, Venus’ orbit is inclined 3 degrees off the Sun’s equator, while the Earth is inclined 7 degrees. This means that most of the time that Venus and Earth are lined up, Venus is either above or below the Sun.

Are you an ageless vampire, or planning to live a long time in multiple robot bodies, then you’re in luck. In the year 69,163, there’ll be a double transit on the surface of Sun with both Mercury and Venus at the same time. Enjoy that while you contemplate the horror of your existence.

Once we become a true Solar System civilization, there will be even more opportunities for transits. People living on Mars will be able to see Mercury, Venus and even transits of Earth passing in front of the Sun. Neptunians will be bored they can see them so often.

The transit method is one of the ways that astronomers discover planets orbiting other stars. Using a space telescope like Kepler, they survey a portion of the night sky, watching the brightness of thousands of stars. When a planet perfectly passes directly in between us and a star, Kepler detects a drop in brightness.

Since its deployment in 2007, Kepler has confirmed the existence of over 2000 extra-solar planets. Credit: NASA
Since its deployment in 2007, Kepler has confirmed the existence of over 2000 extra-solar planets. Credit: NASA
When you think of the geometries involved, it’s amazing this even happens at all. But the Universe is a vast place. Even if only a tiny percentage of star systems are perfectly lined up with us, there are enough to help us discover thousands and thousands of planets.

Kepler has turned up Earth-sized worlds orbiting other stars, some of which are even orbiting in their planet’s habitable zone.

Watching planetary transits is more than just a fun astronomy event, they’re how astronomers figured out the size of the Solar System itself. And now they help us find other planets orbiting other stars.

So, let’s agree to meet up in 2117 to catch the next transit of Venus, and celebrate this amazing event.

The post What Are Planetary Transits? appeared first on Universe Today.

ALIEN MINDS - Part III: The Octopus’s Garden and the Country of the Blind

Alien Minds Part III: The Octopus’s Garden and the Country of the Blind:



METI logo


In our galaxy, there may be, at least, tens of billions of habitable planets, with conditions suitable for liquid water on their surfaces. There may be habitable moons as well. On an unknown number of those worlds, life may have arisen. On an unknown fraction of life-bearing worlds, life may have evolved into complex multicellular, sexually reproducing forms.



During its habitable period, a world with complex life might produce hundreds of millions of evolutionary lineages. One or a few of them might fortuitously encounter special circumstances that triggered runaway growth of their intelligence. These favored few, if they exist, might have built technological civilizations capable of signaling their presence across interstellar distances, or detecting and deciphering a message we send their way. What might such alien minds be like? What senses might they use? How might we communicate with them?





The purposes of the newly created METI (Messaging to ExtraTerrestrial Intelligence) International include fostering multidisciplinary research in the design and transmission of interstellar messages, and building a global community of scholars from the natural sciences, social sciences, humanities, and arts concerned with the origin, distribution, and future of life in the universe.



On May 18 the organization sponsored a workshop which included presentations by biologists, psychologists, cognitive scientists, and linguists. This is the third and final installment of a series of articles about the workshop.



In previous installments, we’ve discussed some ideas about the evolution of intelligence that were featured at the workshop. Here we’ll see whether our Earthly experience can provide us with any clues about how we might communicate with aliens.



Many of the animals that we are most familiar with from daily life, like humans, cats, dogs, birds, fishes, and frogs are vertebrates, or animals with backbones. They are all descended from a common ancestor and share a nervous system organized according to the same basic plan.



Molluscs are another major group of animals that have been evolving separately from vertebrates for more than 600 million years. Although most molluscs, like slugs, snails, and shellfish, have fairly simple nervous systems, one group; the cephalopods, have evolved a much more sophisticated one.





Cephalopods include octopuses, squids, and cuttlefishes. They show cognitive and perceptual abilities rivaling those of our close vertebrate kin. Since this nervous system has a different evolutionary history than of the vertebrates, it is organized in a way completely different from our own. It can give us a glimpse of the similarities and differences we might expect between aliens and ourselves.



David Gire, an associate professor of psychology at the University of Washington, and researcher Dominic Sivitilli gave a presentation on cephalopods at the Puerto Rico workshop. Although these animals have a sophisticated brain, their nervous systems are much more decentralized than that of familiar animals. In the octopus, sensing and moving are controlled locally in the arms, which together contain as many nerve cells, or neurons, as the brain.



The animal’s eight arms are extraordinarily sensitive. Each containing hundreds of suckers, with thousands of sensory receptors on each one. By comparison, the human finger has only 241 sensory receptors per square centimeter. Many of these receptors sense chemicals, corresponding roughly to our senses of taste and smell. Much of this sensory information is processed locally in the arms. When an arm is severed from an octopus’s body, it continues to show simple behaviors on its own, and can even avoid threats. The octopus’s brain simply acts to coordinate the behaviors of its arms.



Cephalopods have acute vision. Although their eyes evolved separately from those of vertebrates, they nonetheless bear an eerie resemblance. They have a unique ability to change the pattern and color of their skin using pigment cells that are under direct control of their nervous systems. This provides them with the most sophisticated camouflage system of any animal on Earth, and is also used for social signaling.







Despite the sophisticated cognitive abilities it exhibits in the lab, the octopus is largely solitary.

Cephalopod groups exchange useful information by observing one another, but otherwise exhibit only limited social cooperation. Many current theories of the evolution of sophisticated intelligence, like Miller’s sapiosexual hypothesis, which was featured in the second installment, assume that social cooperation and competition play a central role in the evolution of complicated brains. Since cephalopods have evolved much more impressive cognitive abilities than other molluscs, their limited social behavior is surprising.



Maybe the limited social behavior of cephalopods really does set limits on their intelligence. However, Gire and Sivitilli speculate that perhaps “an intelligence capable of technological development could exist with minimum social acuity”, and the cephalopod ability to socially share information is enough. The individuals of such an alien collective, they suppose, might possess no sense of self or other.



Besides Gire and Sivitilli, Anna Dornhaus, whose ideas were featured in the first installment, also thinks that alien creatures might function together as a collective mind. Social insects, in some respects, actually do. She doubts, though, that such an entities could evolve human-like technological intelligence without something like Miller’s sapiosexuality to trigger a runaway explosion of intelligence.



But if non-sapiosexual alien technological civilizations do exist, we might find them impossible to comprehend. Given this possible gulf of incomprehension about social structure, Gire and Stivitilli suppose that the most we might aspire to accomplish in terms of interstellar communication is an exchange of mutually useful and comprehensible astronomical information.



Workshop presenter Alfred Kracher, a retired staff scientist at the Ames Laboratory of the University of Iowa, supposes that “the mental giants of the Milky Way are probably artificially intelligent machines… It would be interesting to find evidence of them, if they exist”, he writes, “but then what?” Kracher supposes that if they have emancipated themselves and evolved away from their makers, “they will have nothing in common with organic life forms, human or extraterrestrial. There is no chance of mutual understanding”. We will be able to understand aliens, he maintains, only if “it turns out that the evolution of extraterrestrial life forms is highly convergent with our own”.



Peter Todd, a professor of psychology from Indiana University, holds out hope that such convergence may actually occur. Earthly animals must solve a variety of basic problems that are presented by the physical and biological world that they inhabit.



They must effectively navigate through a world of surfaces, barriers and objects, finding food and shelter, and avoiding predators, parasites, toxins. Extraterrestrial organisms, if they evolve in an Earth-like environment, would face a generally similar set of problems. They may well arrive at similar solutions, just as the octopus evolved eyes similar to ours.



In evolution here on Earth, Todd notes, brain systems originally evolved to solve these basic physical and biological problems appear to have been re-purposed to solve new and more difficult problems, as some animals evolved to solve the problems of living and finding mates as members of societies, and then as one particular age species went on to evolve conceptual reasoning and language. For example, disgust at bad food, useful for avoiding disease, may have been become the foundation for sexual disgust to avoid bad mates, moral disgust to avoid bad clan mates, and intellectual disgust to avoid dubious ideas.



If alien brains evolved solutions similar to the ones our brains did for negotiating the physical and biological world, they they might also have been re-purposed in similar ways. Alien minds might not be wholly different from ours, and thus hope exists for a degree of mutual understanding.



In the early 1970’s the Pioneer 10 and 11 spacecraft were launched on the first exploratory missions to the planet Jupiter and beyond. When their missions were completed, these two probes became the first objects made by humans to escape the sun’s gravitational pull and hurtle into interstellar space.



Because of the remote possibility that the spacecraft might someday be found by extraterrestrials, a team of scientists and scholars lead by Carl Sagan emplaced a message on the vehicle, etched on a metal plaque. The message consisted, in part, of a line drawing of a man and a woman. Later, the Voyager 1 and 2 spacecraft carried a message that consisted, in part, of a series of 116 digital images encoded on a phonographic record.



The assumption that aliens would see and understand images seems reasonable, since the octopus evolved an eye so similar to our own. And that’s not all. The evolutionary biologists Luitfried Von Salvini-Plawen and Ernst Mayr showed that eyes, of various sorts, have evolved forty separate times on Earth, and vision is typically a dominant sense for large, land dwelling animals. Still, there are animals that function without it, and our earliest mammalian ancestors were nocturnal. Could it be that there are aliens that lack vision, and could not understand a message based on images?



In his short story, The Country of the Blind, the great science fiction writer H. G. Wells imagined an isolated mountain village whose inhabitants had been blind for fifteen generations after a disease destroyed their vision.



A lost mountain climber, finding the village, imagines that with his power of vision, he can easily become their king. But the villagers have adapted thoroughly to a life based on touch, hearing, and smell. Instead of being impressed by their visitor’s claim that he can ‘see’, they find it incomprehensible. They begin to believe he is insane. And when they seek to ‘cure’ him by removing two strange globular growths from the front of his head, he flees.



Could their really be an alien country of the blind whose inhabitants function without vision? Workshop presenter Dr. Sheri Wells-Jensen, an associate professor of Linguistics at Bowling Green State University, doesn’t need to imagine the country of the blind, because, in a sense, she lives there. She is blind, and believes that creatures without vision could achieve a level of technology sufficient to send interstellar messages. “Sighted people”, she writes, “tend to overestimate the amount and quality of information gathered by vision alone”.



Bats and dolphins image their dimly lit environments with a kind of naturally occurring sonar called echolocation. Blind human beings can also learn to echolocate, using tongue clicks or claps as emitted signals and analyzing the returning echoes by hearing. Some can do so well enough to ride a bicycle at a moderate pace through an unfamiliar neighborhood. A human can develop the touch sensitivity needed to read braille in four months. A blind marine biologist can proficiently distinguish the species of mollusc shells by touch.



Wells-Jensen posits a hypothetical civilization which she calls the Krikkits, who lack vision but possess sensory abilities otherwise similar to those of human beings. Could such beings build a technological society? Drawing on her knowledge of the blind community and a series of experiments, she thinks they could.



Finding food would present few special difficulties, since blind naturalists can identify many plant species by touch. Agriculture could be conducted as modern blind gardeners do it, by marking crops using stakes and piles of rock, and harvesting by feel. The combination of a stick used as a cane to probe the path ahead and echolocation make traveling by foot effective and safe. A loadstone compass would further aid navigational abilities. The Krikkits might use snares rather than spears or arrows to trap animals, making tools by touch.



Mathematics is vital to building a technological society. For most human beings, with our limited memory, a paper and pencil or a blackboard are essential for doing math. Krikkits would need to find other such aids, such as tactual symbols on clay tablets, abacus-like devices, or patterns sewn on hides or fabric.



Successful blind mathematicians often have prodigious memories, and can perform complex calculations in their heads. One of history’s greatest mathematicians, Leonard Euler, was blind for the last 17 years of his life, but remained mathematically productive through the use of his memory.



The obstacles to a blind society developing technology may not be insurmountable. Blind people are capable of handling fire and even working with molten glass. Krikkits might therefore use fire for cooking, warmth, to bake clay vessels, and smelt metal ores. Initially there only astronomical knowledge would be of the sun as a source of heat. Experiments with loadstones and metals would lead to a knowledge of electricity.



Eventually, the Krikkits might imitate their sonar with radio waves, inventing radar. If their planet possessed a moon or moons, radar reflections from them might provide their first knowledge of astronomical objects other than their sun. Radar would also enable them to learn for the first time that their planet is round.



The Krikkits might learn to detect other forms of radiation like X-rays and ‘light’. The ability to detect this second mysterious form of radiation might allow them to discover the existence of the stars and develop an interest in interstellar communication.



What sorts of messages might they send or understand? Well-Jensen believes that line drawings, like the drawing of the man and the woman on the Pioneer plaque, and other such pictorial representations might be an impenetrable mystery to them. On the other hand, she speculates that Krikkits might represent large data sets through sound, and that their counterpart to charts and graphs might be equally incomprehensible to us.



Images might pose a challenge for the Krikkits, but perhaps, Wells-Jensen concedes, not an impossible one. There is evidence that bats image their world using echolocation. Kikkits might be likely to evolve similar abilities, though Wells-Jensen believes they would not be essential for making tools or handling objects.



Perhaps humans and Krikkits could find common ground by transmitting instructions for three dimensional printed objects that could be explored tactually. Wells-Jensen thinks they might also understand mathematical or logical languages proposed for interstellar communication.



The diversity of cognition and perception that we find here on Earth teaches us that if extraterrestrial intelligence exists, it is likely to be much more alien than much of science fiction has prepared us to expect. In our attempt to communicate with aliens, the gulf of mutual incomprehension may yawn as wide as the gulf of interstellar space. Yet this is a gulf we must somehow cross, if we wish ever to become citizens of the galaxy.



For further reading:



Cain, F. (2008) Is Our Universe Ruled by Artificial Intelligence, Universe Today.



Kaufmann G. (2005) Spineless smarts, NOVA



Land, M. F., and Nilsson, D-E. (2002) Animal Eyes, Oxford University Press.



Mather, J. A. (2008) Cephalopod consciousness: Behavioral evidence, Cognition and Consciousness 17(1): 37-48.



Patton, P. E. (2016) Alien Minds I: Are Extraterrestrial Civilizations Likely to Evolve? Universe Today.



Patton, P. E. (2016) Alien Minds II: Do Aliens Think Big Brains are Sexy Too? Universe Today.



P. Patton (2014) Communicating across the cosmos, Part 1: Shouting into the darkness, Part 2: Petabytes from the Stars, Part 3: Bridging the Vast Gulf, Part 4: Quest for a Rosetta Stone, Universe Today.



Wells, H. G. (1904) The Country of the Blind, The literature network.

The post Alien Minds Part III: The Octopus’s Garden and the Country of the Blind appeared first on Universe Today.

Wednesday, June 1, 2016

NEW PLANETS - Student Discovers Four New Planets

Student Discovers Four New Planets:



The four new, but as yet unconfirmed, exoplanets. Image: University of British Columbia


A student at the University of British Columbia (UBC), Canada, has discovered four new exoplanets hidden in data from the Kepler spacecraft.



Michelle Kunimoto recently graduated from UBC with a Bachelor's degree in physics and astronomy. As part of her coursework, she spent a few months looking closely at Kepler data, trying to find planets that others had overlooked.



In the end, she discovered four planets, (or planet candidates until they are independently confirmed.) The first planet is the size of Mercury, two are roughly Earth-sized, and one is slightly larger than Neptune. According to Kunimoto, the largest of the four, called KOI (Kepler Object of Interest) 408.05, is the most interesting. That one is 3,200 light years away from Earth and occupies the habitable zone of its star.



“Like our own Neptune, it’s unlikely to have a rocky surface or oceans,” said Kunimoto, who graduates today from UBC. “The exciting part is that like the large planets in our solar system, it could have large moons and these moons could have liquid water oceans.”



Her astronomy professor, Jaymie Matthews, shares her enthusiasm. “Pandora in the movie Avatar was not a planet, but a moon of a giant planet,” he said. And we all know what lived there.



[embed]https://www.youtube.com/watch?v=YXIauLV90p8[/embed]



On its initial mission, Kepler looked at 150,000 stars in the Milky Way. Kepler looks for dips in the brightness of these stars, which can be caused by planets passing between us and the star. These dips are called light curves, and they can tell us quite a bit about an exoplanet.



“A star is just a pinpoint of light so I’m looking for subtle dips in a star’s brightness every time a planet passes in front of it,” said Kunimoto. “These dips are known as transits, and they’re the only way we can know the diameter of a planet outside the solar system.”







One of the limitations of the Kepler mission is that it's biased against planets that take a long time to orbit their star. That's because the longer the orbit is, the fewer transits can be witnessed in a given amount of time. The "warm Neptune" KOI 408.05 found by Kunimoto takes 637 days to orbit its sun.



This long orbit explains why the planet was not found initially, and also why Kunimoto is receiving recognition for her discovery. It took a substantial commitment and effort to uncover it. Kepler has discovered almost 5,000 planet and planet candidates, and of those, only 20 have longer orbits than KOI 408.05.



Kunimoto and Matthews have submitted the findings to the Astronomical Journal. They may be the first of many submissions for Kunimoto, as she is returning to UBC next year to earn a Master's Degree in physics and astronomy, when she will hunt for more planets and investigate their habitability.



The fun didn't end with her exoplanet discovery, however. As a Star Trek fan (who isn't one?) she was lucky enough to meet William Shatner at an event at the University, and to share her discovery with Captain James Tiberius Kirk.



It makes you wonder what other surprises might lie hidden in the Kepler data, and what else might be uncovered. Might a life-bearing planet or moon, maybe the only one, be found in Kepler's data at some future time?



You can read Kunimoto's paper here.

The post Student Discovers Four New Planets appeared first on Universe Today.

How Was the Solar System Formed?

How Was the Solar System Formed?:



Solar System Themed Products


Since time immemorial, humans have been searching for the answer of how the Universe came to be. However, it has only been within the past few centuries, with the Scientific Revolution, that the predominant theories have been empirical in nature. It was during this time, from the 16th to 18th centuries, that astronomers and physicists began to formulate evidence-based explanations of how our Sun, the planets, and the Universe began.



When it comes to the formation of our Solar System, the most widely accepted view is known as the Nebular Hypothesis. In essence, this theory states that the Sun, the planets, and all other objects in the Solar System formed from nebulous material billions of years ago. Originally proposed to explain the origin of the Solar System, this theory has gone on to become a widely accepted view of how all star systems came to be.



Nebular Hypothesis:

According to this theory, the Sun and all the planets of our Solar System began as a giant cloud of molecular gas and dust. Then, about 4.57 billion years ago, something happened that caused the cloud to collapse. This could have been the result of a passing star, or shock waves from a supernova, but the end result was a gravitational collapse at the center of the cloud.



https://youtu.be/gLzsnITQZaE



From this collapse, pockets of dust and gas began to collect into denser regions. As the denser regions pulled in more and more matter, conservation of momentum caused it to begin rotating, while increasing pressure caused it to heat up. Most of the material ended up in a ball at the center while the rest of the matter flattened out into disk that circled around it. While the ball at the center formed the Sun, the rest of the material would form into the protoplanetary disc.



The planets formed by accretion from this disc, in which dust and gas gravitated together and coalesced to form ever larger bodies. Due to their higher boiling points, only metals and silicates could exist in solid form closer to the Sun, and these would eventually form the terrestrial planets of Mercury, Venus, Earth, and Mars. Because metallic elements only comprised a very small fraction of the solar nebula, the terrestrial planets could not grow very large.



In contrast, the giant planets (Jupiter, Saturn, Uranus, and Neptune) formed beyond the point between the orbits of Mars and Jupiter where material is cool enough for volatile icy compounds to remain solid (i.e. the Frost Line). The ices that formed these planets were more plentiful than the metals and silicates that formed the terrestrial inner planets, allowing them to grow massive enough to capture large atmospheres of hydrogen and helium. Leftover debris that never became planets congregated in regions such as the Asteroid Belt, Kuiper Belt, and Oort Cloud.







Within 50 million years, the pressure and density of hydrogen in the center of the protostar became great enough for it to begin thermonuclear fusion. The temperature, reaction rate, pressure, and density increased until hydrostatic equilibrium was achieved. At this point, the Sun became a main-sequence star. Solar wind from the Sun created the heliosphere and swept away the remaining gas and dust from the protoplanetary disc into interstellar space, ending the planetary formation process.



History of the Nebular Hypothesis:

The idea that the Solar System originated from a nebula was first proposed in 1734 by Swedish scientist and theologian Emanual Swedenborg. Immanuel Kant, who was familiar with Swedenborg's work, developed the theory further and published it in his Universal Natural History and Theory of the Heavens (1755). In this treatise, he argued that gaseous clouds (nebulae) slowly rotate, gradually collapsing and flattening due to gravity and forming stars and planets.



A similar but smaller and more detailed model was proposed by Pierre-Simon Laplace in his treatise Exposition du system du monde (Exposition of the system of the world), which he released in 1796. Laplace theorized that the Sun originally had an extended hot atmosphere throughout the Solar System, and that this "protostar cloud" cooled and contracted. As the cloud spun more rapidly, it threw off material that eventually condensed to form the planets.







The Laplacian nebular model was widely accepted during the 19th century, but it had some rather pronounced difficulties. The main issue was angular momentum distribution between the Sun and planets, which the nebular model could not explain. In addition, Scottish scientist James Clerk Maxwell (1831 - 1879) asserted that different rotational velocities between the inner and outer parts of a ring could not allow for condensation of material.



It was also rejected by astronomer Sir David Brewster (1781 - 1868), who stated that:



"those who believe in the Nebular Theory consider it as certain that our Earth derived its solid matter and its atmosphere from a ring thrown from the Solar atmosphere, which afterwards contracted into a solid terraqueous sphere, from which the Moon was thrown off by the same process... [Under such a view] the Moon must necessarily have carried off water and air from the watery and aerial parts of the Earth and must have an atmosphere."
By the early 20th century, the Laplacian model had fallen out of favor, prompting scientists to seek out new theories. However, it was not until the 1970s that the modern and most widely accepted variant of the nebular hypothesis - the solar nebular disk model (SNDM) - emerged. Credit for this goes to Soviet astronomer Victor Safronov and his book Evolution of the protoplanetary cloud and formation of the Earth and the planets (1972). In this book, almost all major problems of the planetary formation process were formulated and many were solved.



https://upload.wikimedia.org/wikipedia/commons/transcoded/1/1e/Artist%E2%80%99s_impression_of_the_disc_and_gas_streams_around_HD_142527_%28Animation%29.ogg/Artist%E2%80%99s_impression_of_the_disc_and_gas_streams_around_HD_142527_%28Animation%29.ogg.480p.webm



For example, the SNDM model has been successful in explaining the appearance of accretion discs around young stellar objects. Various simulations have also demonstrated that the accretion of material in these discs leads to the formation of a few Earth-sized bodies. Thus the origin of terrestrial planets is now considered to be an almost solved problem.



While originally applied only to the Solar System, the SNDM was subsequently thought by theorists to be at work throughout the Universe, and has been used to explain the formation of many of the exoplanets that have been discovered throughout our galaxy.



Problems:

Although the nebular theory is widely accepted, there are still problems with it that astronomers have not been able to resolve. For example, there is the problem of tilted axes. According to the nebular theory, all planets around a star should be tilted the same way relative to the ecliptic. But as we have learned, the inner planets and outer planets have radically different axial tilts.



Whereas the inner planets range from almost 0 degree tilt, others (like Earth and Mars) are tilted significantly (23.4° and 25°, respectively), outer planets have tilts that range from Jupiter's minor tilt of 3.13°, to Saturn and Neptune's more pronounced tilts (26.73° and 28.32°), to Uranus' extreme tilt of 97.77°, in which its poles are consistently facing towards the Sun.







Also, the study of extrasolar planets have allowed scientists to notice irregularities that cast doubt on the nebular hypothesis. Some of these irregularities have to do with the existence of "hot Jupiters" that orbit closely to their stars with periods of just a few days. Astronomers have adjusted the nebular hypothesis to account for some of these problems, but have yet to address all outlying questions.



Alas, it seems that it questions that have to do with origins that are the toughest to answer. Just when we think we have a satisfactory explanation, there remain those troublesome issues it just can't account for. However, between our current models of star and planet formation, and the birth of our Universe, we have come a long way. As we learn more about neighboring star systems and explore more of the cosmos, our models are likely to mature further.



We have written many articles about the Solar System here at Universe Today. Here's The Solar System, Did our Solar System Start with a Little Bang?, and What was Here Before the Solar System?



For more information, be sure to check out the origin of the Solar System and how the Sun and planets formed.



Astronomy Cast also has an episode on the subject - Episode 12: Where do Baby Stars Come From?

The post How Was the Solar System Formed? appeared first on Universe Today.