Science and Nature

At 11.2 billion years old, it is the oldest star with Earth-sized planets ever found and proves that such planets have formed throughout the history of the Universe.

The discovery, announced on 28 January (AEDT) in the Astrophysical Journal, used observations made by NASA's Kepler satellite. The scientific collaboration was led by the University of Birmingham and contributed to by the University of Sydney.

The star, named Kepler-444, hosts five planets smaller than Earth, with sizes varying between those of Mercury and Venus.

"We've never seen anything like this -- it is such an old star and the large number of small planets make it very special," said Dr Daniel Huber from the University's School of Physics and an author on the paper.

"It is extraordinary that such an ancient system of terrestrial-sized planets formed when the universe was just starting out, at a fifth its current age. Kepler-444 is two and a half times older than our solar system, which is only a youthful 4.5 billion years old.

"This tells us that planets this size have formed for most of the history of the universe and we are much better placed to understand exactly when this began happening."

Dr Tiago Campante, the research leader from the University of Birmingham said, "We now know that Earth-sized planets have formed throughout most of the Universe's 13.8-billion-year history, which could provide scope for the existence of ancient life in the Galaxy."

Together with their international colleagues the University's astronomy team used asteroseismology to determine the age of the star and planets. This technique measures oscillations -- the natural resonances of the host star caused by sound waves trapped within it.

They lead to miniscule changes or pulses in the star's brightness and allow researchers to measure its diameter, mass, and age. The presence and size of the planets is detected by the dimming that occurs when the planets pass across the face of the star. This fading in the intensity of the light received from the star enables scientists to accurately measure the sizes of the planets relative to the size of the star.

"When asteroseismology emerged about two decades ago we could only use it on the Sun and a few bright stars, but thanks to Kepler we can now apply the technique to literally thousands of stars. Asteroseismology allows us to precisely measure the radius of Kepler-444 and hence the sizes of its planets. For the smallest planet in the Kepler-444 system, which is slightly larger than Mercury, we measured its size with an uncertainty of only 100km," Dr Huber said.

"It was clear early on that we had discovered something very unusual because we had five planets orbiting a very bright star -- one of the brightest Kepler has observed. It is fantastic that we can use asteroseismology to date the star and determine just how old it is.

"In the case of Kepler-444 the planets orbit their parent star in less than 10 days, at less than one-tenth the Earth's distance from the Sun. Their closeness to their host star means they are uninhabitable because of the lack of liquid water and high levels of radiation. Nevertheless, discoveries like Kepler-444 provide important clues on whether a planet that is more truly comparable to Earth may exist. "We're another step closer towards finding the astronomers' holy grail -- an Earth-sized planet with a one year orbit around a star similar to our Sun."
A/c NASA, Astronomers using data from NASA's Kepler mission have discovered a planetary system of five small planets dating back to when the Milky Way galaxy was a youthful two billion years old.

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The above story is based on materials provided by University of Sydney.

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Evidence of Earth's first continents — 4.3-billion-year-old "diamonds" — are actually just fragments of polishing grit, a new study finds.

In 2007, an international team first reported discovering the tiny gems, which hid in pockets insidezircon crystals from Western Australia's Jack Hills, in the journal Nature. But it turns out that the gems weren't actually diamonds, but polishing paste, smushed into hairs'-width cracks when the zircons were prepared for laboratory tests, according to a study published online in the Feb. 1, 2014, edition of the journal Earth and Planetary Science Letters.

Scientists at the University of California, Riverside (UCR) found the mistake by snapping pictures of the disputed diamonds with a powerful transmission electron microscope, along with other techniques. Instead of bumpy real diamonds, they discovered sharp-cornedsynthetic diamonds embedded in polishing compound.

"There can be no doubt of the images we show," said Harry Green, a UCR research geophysicist and study co-author. "Polishing the specimens with grinding compound that was made of diamonds was a terrible mistake."

The original authors, who provided their samples for analysis by Green and lead study author Larissa Dobrzhinetskaya, also agree with the conclusions.

"Back then, we were convinced that the diamonds are real due to apparently clear evidence," said Thorsten Geisler-Wierwille, co-author of the 2007 study. "We agree with the final conclusion of Dobrzhinetskaya and co-workers."

Zircons are the oldest evidence of rocks on Earth's surface — tiny but tough survivors of the planet's hellish early years. In the 1980s, scientists discovered Jack Hills zircon crystals as old as 4.4 billion years within 3-billion-year-old conglomerates, a sedimentary rock similar to pebbly stream deposits. Because the zircons are much, much older than the conglomerate, the minerals must have washed into the conglomerate, eroded out of Earth's oldest rocks. [Have There Always Been Continents?]

So it was a big deal when the international team, led by German geochemist Martina Menneken, reported discovering diamonds inside Jack Hills zircons. The findings, published Aug. 23, 2007, in the journal Nature, reported bits of diamonds ranging from 4.3 billion to 3.1 billion years old within individual zircons. Most diamonds were just a few times wider than a human hair.

The presence of diamonds meant the young Earth was cool enough to make relatively thick continental crust. Many modelers have suggested that Earth was covered by a roiling lava sea for its first 500 million years — an era called the Hadean, for its hellishly hot temperatures. But diamond means that the surface was cold enough to crystallize miles-thick chunks of rock, under which diamonds form. The findings also supported the idea that plate tectonics was in motion, with plates of crust skidding about and colliding, creating the pressures that form diamonds.

But some scientists, including Dobrzhinetskaya, were suspicious of the findings, because Menneken and her colleagues polished the zircons with diamond paste. They also found it hard to believe that a single zircon could have diamonds that ranged in age across more than 1 billion years.

"The story was extraordinarily difficult to buy," Green said.

Contamination from diamond-polishing paste is a common problem for a different group of diamond experts — those who specialize in studying ultra-high-pressure rocks. These are some of the most extreme rocks on Earth, forged at great pressures in tectonic collision zones and then brought to the surface. Diamonds are a key clue to hunting down these ultra-high-pressure zones.

Dobrzhinetskaya is an expert in ultra-high-pressure diamonds, with a suite of high-tech equipment specially tuned for analyzing these minerals. Several years ago, she asked the German researchers to let her test the Jack Hills zircons, and the team willingly agreed.

"We were also interested in [transmission electron microscope, or TEM] results and, at that time, had no possibility to perform TEM investigations by ourselves," Geisler-Wierwille told LiveScience in an email interview.

The UCR scientists discovered the size and shape of the diamond crystals were more similar to those seen on angular synthetic diamonds. Instead of growing in place, with interlocking fingers grasping the zircon, the diamonds simply sat in their voidlike homes. The diamonds were also surrounded by flecks of minerals that matched the composition of the polishing compound and epoxy resin used in the German lab that prepped the zircons. [Oops! The 5 Greatest Scientific Blunders]

"These things are diamond paste," Green said. But the collaboration broke down when it came time to publish the results. While both groups agree that polishing paste got inside the Jack Hills zircons, Geisler-Wierwille thinks that there still could be early-Earth diamonds embedded more deeply, in the core of the zircon crystals, which are only about as wide as mechanical-pencil lead (0.3 millimeters).

Green strongly disagrees. "They can go back to their cache of Jack Hill zircons and make new specimens," Green said. "If you're a betting person, I'll make you a bet that they won't find it. There have been an enormous amount of [Jack Hills] zircons analyzed in a bunch of different ways, and no one has ever found diamonds."

Indeed, the German team went back and picked through about 1,000 zircons in search for more diamonds from their samples and didn't find a single microscopic gem. (They do report finding graphitelike carbon, but that's another story in itself.)

Based on the TEM images, both groups agree the "diamonds" cited in the 2007 Nature paper come from polishing-paste diamonds. But because of the disagreement over whether diamonds could be found in other zircons, Geisler-Wierwille's group declined to add their names as co-authors on the study by Dobrzhinetskaya and Green. Instead, the German-led team wrote their own paper, using similar methods.

But both studies were rejected when submitted for publication in scientific journals. Dobrzhinetskaya's was rebuffed by Nature and Geisler-Wierwille's (with Martina Menneken as first author) by the journal American Mineralogist.

Nature declined to comment on the rejection. However, Green said reviewers agreed with Geisler-Wierwille — there was a possibility that some zircons held real diamonds. (Outside experts review studies for research journals and provide their opinion on whether it is worthy of publication.)

But at Earth and Planetary Science Letters, reviewers agreed there was no wiggle room, said Mark Harrison, a geochemist at the University of California, Los Angeles who serves on the journal's editorial board and accepted the paper for publication.

"I had three people review Larissa [Dobrzhinetskaya]'s paper, and nobody could see any way out of it," Harrison told LiveScience. Harrison is also an expert on Jack Hills zircons, and he said he has analyzed thousands of the zircons without ever finding a diamond.

Because the Jack Hills diamonds have been used to support models for early Earth cooling, Harrison hopes the new study corrects the record. "It's important that people stop wasting their time," Harrison said. "The early Earth was called Hadean for a reason. Personally, I disagree with that because I think we've found legitimate [zircon] inclusions of other low-temperature minerals, but I don't think we've found diamonds."

A group of scientists discovered the mimic octopus off the coast of Sulawesi, Indonesia in 1998. The species was thought to only inhabit the islands of Indonesia until Darren Coker spotted one was spotted near the Great Barrier Reef in 2010. This octopus was on a shallow sand flat near Lizard Island (1). The mimic octopus lives in nutrient-rich estuarine bays of Indonesia and Malaysia primarily in shallow warm waters about 15 meters deep in the Indo-West Pacific. It prefers obscuring murky and muddy sea floors to blend in with its natural brown, beige color.

The mimic octopus grows to an average length of 60cm (2 feet) and its tentacles grow to be 62 cm (25 in long). The natural colour is light brown/beige, but the octopus may adopt a striped white and brown pattern to scare off predators by appearing to be poisonous. It is unknown if it is poisonous to predators. It is assumed that if it is not considering that it is poisonous, there would be no need to camouflage themselves as all the other poisonous sea animals (1). 

Most octopuses can use pigment sacs (chromatophores) to change their skin colour and texture to blend in with their surrounding background, such as algae-encrusted rock and nearby coral. The mimic octopus can blend in with backgrounds and can mimic the shape of objects, such as coral and rock, and some animals (1). It is the only known aquatic species that impersonates an array of different sea animals via changes in behaviour, coloration and body posture, depending on what predator it is trying to elude (2). It uses mimicry as a primary defense and is reputed to mimic up to 15 species of other local marine organisms. When motionless, it assumes body patterns and postures resembling small sponges, tube-worm tubes or colonial tunicates in an open sand habitat. The barren homelands provided the impetus to evolve mimicry (4). The octopus is intelligent enough to discern which dangerous sea creature to impersonate that will present the greatest threat to its current possible predator. When an octopus was attacked by territorial damselfishes, it mimicked the black-and-yellow banded sea snake, a predator of damselfishes (3).

Most of the animals it mimics are poisonous. Its shape shifting is probably a deliberate survival strategy. The animals it mimics include:

1. Lionfish: This poisonous fish has brown and white stripes and spines that trail behind it on all sides. When the octopus changes its colour and shapes its eight legs to look like spines, it seems to be a highly venomous creature that should be avoided.

2. Sea snake: If under attack, the octopus may hide in a hole except for two of its legs, which it sticks out in opposite directions. What remains in view is a long thin object with white and black bands running across the elongated body. Many predators avoid tangling with the highly venomous sea snake and swim away, leaving the octopus unharmed.

3. Flatfish: The octopus mimicsa flatfish by pulling its arms together on one side and flattening out its body while moving forward along the ocean floor. It mimics the shape, swimming actions, speed, duration and sometimes the colour of swimming flounders. During flounder mimicry, it is actively moving and conspicuous; immediately before and after flounder mimicry, it is camouflaged and motionless (sitting or very slowly crawling). It uses flounder mimicry when its movement would give away camouflage in an open habitat. 

4. Jellyfish – The octopus may act as a Jellyfish to frighten and discourage predators. It puffs up its head and siphon and lets its arms trail behind it. It mimics the motions of a jellyfish swimming by going to the surface and slowly sinking with its arms spread evenly around its body.

Mimic Octopus is capable of an incredible 15 impersonations.The mimic octopus can be classified as a hunter or a forager. It is thought to be a hunter, as it can stalk prey and hunt down small fish and catch them. More often, however, it forages for food by using a jet of water through its siphon (funnel) to glide over the sand, while searching for prey, and using its slender tentacles to reach into crevices in coral and holes in the sand, using its suction cups to grab small crustaceans and eat them. As it prefers to live in shallow, murky waters, it is believed that it feeds almost exclusively on small fish, crabs and worms, which are the only two animals that are common to those conditions that the octopus can survive on. The octopus isnot known to eat any type of plant or vegetation.(1). It may use aggressive mimicry to approach wary prey, such as mimicking a crab as an apparent mate, only to devour its deceived suitor. It prefers river mouths and estuaries to reefs, which give more shelter to other types of octopus. This is because it can impersonate poisonous fish and hides out in the open.

Males die within a few months after mating. A fertilized female lays about 200,000 eggs, which she hangs these eggs in strings from the ceiling of her lair or individually attaches them to the substratum. She cares for the eggs, guarding them against predators and gently blowing currents of water over them so they get enough oxygen. She does not eat for about a month while she takes care of the unhatched eggs. She dies at around the time the eggs hatch (5). The mimic octopus is not thought to be at risk of extinction.


References : Norman, Finn & Tregenza. 2001. Proc Biol Sci 268: 1755-1758.
                  Mimic Octopuses, Thaumoctopus mimicus