Tag Archives: cosmology

A heavy metal exoplanet, a star with no iron

Two strangely related astronomy stories to start the day:

The first describes a weird planet so hot that metals are gas in the atmosphere:

A scorching planet, WASP-121b orbits precariously close to a star that is even hotter than our Sun. The intense radiation heats the planet’s upper atmosphere to a blazing 4,600 degrees Fahrenheit. Apparently, the lower atmosphere is still so hot that iron and magnesium remain in gaseous form and stream to the upper atmosphere, where they escape into space on the coattails of hydrogen and helium gas.

The sizzling planet is also so close to its star that it is on the cusp of being ripped apart by the star’s intense pull. This hugging distance means that the planet is stretched into a football shape due to gravitational tidal forces.

The presence of so much heavy elements suggests this planet and star formed relatively recently in the history of the universe, after many generations of star formation made possible the creation of those elements.

The second describes a star so devoid of iron that it hints of the first stars that ever formed.

The very first stars in the Universe are thought to have consisted of only hydrogen and helium, along with traces of lithium. These elements were created in the immediate aftermath of the Big Bang, while all heavier elements have emerged from the heat and pressure of cataclysmic supernovae – titanic explosions of stars. Stars like the Sun that are rich in heavy element therefore contain material from many generations of stars exploding as supernovae.

As none of the first stars have yet been found, their properties remain hypothetical. They were long expected to have been incredibly massive, perhaps hundreds of times more massive than the Sun, and to have exploded in incredibly energetic supernovae known as hypernovae.

The confirmation of the anaemic SMSS J160540.18–144323.1, although itself not one of the first stars, adds a powerful bit of evidence.

Dr Nordlander and colleagues suggest that the star was formed after one of the first stars exploded. That exploding star is found to have been rather unimpressive, just ten times more massive than the Sun, and to have exploded only feebly (by astronomical scales) so that most of the heavy elements created in the supernova fell back into the remnant neutron star left behind.

Only a small amount of newly forged iron escaped the remnant’s gravitational pull and went on, in concert with far larger amounts of lighter elements, to form a new star – one of the very first second generation stars, that has now been discovered.

All the the science and data with both stories is highly uncertain. Both however point to the complex and hardly understood process that made us possible.

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Dark energy might not exist

The uncertainty of science: A new model for the universe that omits dark energy produces a better fit to what is know than previous theories that included it.

The new theory, dubbed timescape cosmology, includes the known lumpiness of the universe, while the older traditional models that require dark energy do not.

Timescape cosmology has no dark energy. Instead, it includes variations in the effects of gravity caused by the lumpiness in the structure in the universe. Clocks carried by observers in galaxies differ from the clock that best describes average expansion once variations within the universe (known as “inhomogeneity” in the trade) becomes significant. Whether or not one infers accelerating expansion then depends crucially on the clock used. “Timescape cosmology gives a slightly better fit to the largest supernova data catalogue than Lambda Cold Dark Matter cosmology,” says Wiltshire.

He admits the statistical evidence is not yet strong enough to definitively rule in favour of one model over the other, and adds that future missions such as the European Space Agency’s Euclid spacecraft will have the power to distinguish between differing cosmology models.

Both models rely on a very weak data set, based on assumptions about Type 1a supernovae that are likely wrong. It is thus likely that neither explains anything, as neither really has a good picture of the actual universe.

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Gravitational wave/inflation discovery literally bites the dust

The uncertainty of science: The big discovery earlier this year of gravitational waves confirming the cosmological theory of inflation has now been found to be completely bogus. Instead of being caused by gravitational waves, the detection was caused by dust in the Milky Way.

Even while the mainstream press was going nuts touting the original announcement, I never even posted anything about it. To me, there were too many assumptions underlying the discovery, as well as too many data points with far too large margins of error, to trust the result. It was interesting, but hardly a certain discovery. Now we have found that the only thing certain about it was that it wasn’t the discovery the scientists thought.

Nor is this unusual for the field of cosmology. Because much of this sub-field of astronomy is dependent on large uncertainties and assumptions, its “facts” are often disproven or untrustworthy. And while the Big Bang theory itself unquestionably fits the known facts better than any other theory at this time, there remain too many uncertainties to believe in it without strong skepticism.

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Cosmologists, using new data, are now reconsidering their theories on the manner in which the universe began organizing itself after the Big Bang.

The uncertainty of science: Cosmologists, using new data, are now reconsidering their theories on the manner in which the universe began organizing itself after the Big Bang.

Scientists call it the epoch of reionization, the period in which a newborn universe went from darkness to light as the first stars, galaxies and black holes began forming and radiating energy.

In a paper published Thursday in Nature, researchers are challenging one long-held conception about how quickly the universe began warming during this transition period. Based on observations of X-ray emissions from binary star systems, as well as new mathematical models, cosmologists at Tel Aviv University and Harvard say that heating of the universe progressed much more slowly, and uniformly, than previously thought.

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Astronomers have found a dozen supernovae taking place closer to the Big Bang than ever detected.

Astronomers have found a dozen supernovae taking place only a few billion years after the Big Bang.

[The results suggest that these types of supernovae] were exploding about five times more frequently 10 billion years ago than they are today. These supernovas are a major source of iron in the universe, the main component of the Earth’s core and an essential ingredient of the blood in our bodies.

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The most distant quasar ever found

Astronomers have found the most distant quasar ever, and are baffled by its existence.

The light from the quasar started its journey toward us when the universe was only 6% of its present age, a mere 770 million years after the Big Bang, at a redshift of about 7.1 [3]. “This gives astronomers a headache,” says lead author Daniel Mortlock, from Imperial College London. “It’s difficult to understand how a black hole a billion times more massive than the Sun can have grown so early in the history of the universe. It’s like rolling a snowball down the hill and suddenly you find that it’s 20 feet across!”

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Are astronomers finally going to push for a replacement for Hubble?

Astronomers are considering the merger two space missions to create a new optical/ultraviolet space telescope. The mission would be designed to do both deep cosmology and exoplanet observations.

The two communities would both like to see a 4–8-metre telescope in space that would cost in excess of $5 billion. “Our interests are basically aligned,” says [Jim Kasting, a planetary scientist at Pennsylvania State University]. Such a mission would compete for top billing in the next decadal survey of astronomy by the US National Academy of Sciences, due in 2020.

This story is big news, as it indicates two things. First, the 2010 Decadal Survey, released in August 2010, is almost certainly a bust. The budget problems at NASA as well as a general lack of enthusiasm among astronomers and the public for its recommendations mean that the big space missions it proposed will almost certainly not be built.
» Read more

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Mature galaxy cluster found in young universe

A mature galaxy cluster has been found by astronomers at a time when the universe is thought to be only a quarter of its present age.

This discovery could be very significant, since astronomers think mature galaxy clusters need time to form, and shouldn’t exist in the early universe. “If further observations find many more [of these clusters] then this may mean that our understanding of the early Universe needs to be revised.”

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