New Super-Earth Detected Within the Habitable Zone of a Nearby Cool Star

New Super-Earth Detected Within the Habitable Zone of a Nearby Cool Star

  10:12:00 AM    Science Lover

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An international team of scientists led by Carnegie's Guillem Anglada-Escudé and Paul Butler has discovered a potentially habitable super-Earth orbiting a nearby star. The star is a member of a triple star system and has a different makeup than our Sun, being relatively lacking in metallic elements. This discovery demonstrates that habitable planets could form in a greater variety of environments than previously believed.

An artistic conception of the two planets reported on in this
paper: b and c. Planet c is the one that lies in the habitable
zone of the star. Planet b is too hot to be habitable. (Credit:
Images courtesy of Guillem Anglada-Escud)

Their work will be published in The Astrophysical Journal Letters.

The team used public data from the European Southern Observatory and analyzed it with a novel data analysis method. They also incorporated new measurements from the Keck Observatory's High Resolution Echelle Spectrograph and the new Carnegie Planet Finder Spectrograph at the Magellan II Telescope.

Their planet-finding technique involved measuring the small wobbles in a star's orbit in response to a planet's gravity. Anglada-Escudé and his team focused on an M-class dwarf star called GJ 667C, which is 22 light years away. It is a member of a triple-star system. The other two stars (GJ 667AB) are a pair of orange K dwarfs, with a concentration of heavy elements only 25% that of our Sun's. Such elements are the building blocks of terrestrial planets so it was thought to be unusual for metal-depleted star systems to have an abundance of low mass planets.

GJ 667C had previously been observed to have a super-Earth (GJ 667Cb) with a period of 7.2 days, although this finding was never published. This orbit is too tight, and thus hot, to support life. The new study started with the aim of obtaining the orbital parameters of this super-Earth.

But in addition to this first candidate, the research team found the clear signal of a new planet (GJ 667Cc) with an orbital period of 28.15 days and a minimum mass of 4.5 times that of Earth. The new planet receives 90% of the light that Earth receives. However, because most of its incoming light is in the infrared, a higher percentage of this incoming energy should be absorbed by the planet. When both these effects are taken into account, the planet is expected to absorb about the same amount of energy from its star that Earth absorbs from the Sun. This would allow surface temperatures similar to Earth and perhaps liquid water, but this extreme cannot be confirmed without further information on the planet's atmosphere.

"This planet is the new best candidate to support liquid water and, perhaps, life as we know it," Anglada-Escudé said.

The team notes that the system might also contain a gas-giant planet and an additional super-Earth with an orbital period of 75 days. However, further observations are needed to confirm these two possibilities. "With the advent of a new generation of instruments, researchers will be able to survey many M dwarf stars for similar planets and eventually look for spectroscopic signatures of life in one of these worlds."

Anglada-Escudé was with Carnegie when he conducted the research, but has since moved on to University of Gottingen. His co-authors are Carnegie's Butler, Jeffrey D. Crane, Stephen A. Shectman, and Ian B. Thompson; Pamela Arriagada and Dante Minniti of Pontificia Universidad Catolica de Chile; Steve Vogt and Eugenio J. Rivera of University of California's Lick Observatory; Nader Haghighipour of the Institute for Astronomy & NASA Astrobiology Institute at University of Hawaii-Monoa; Brad D. Carter of University of Southern Queensland; C. G. Tinney, Robert A. Wittenmyer, and Jeremy A. Bailey of the University of New South Wales; Simon J. O'Toole of the Australian Astronomical Observatory; Hugh R.A. Jones of the University of Hertfordshire; and James S. Jenkins of the Universidad de Chile, Camino El Observatorio.

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Living Dinosaurs in Space: Galaxies in Today's Universe Thought to Have Existed Only in Distant Past

Living Dinosaurs in Space: Galaxies in Today's Universe Thought to Have Existed Only in Distant Past

  10:09:00 AM    Science Lover

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Using Australian telescopes, Swinburne University astronomy student Andy Green has found 'living dinosaurs' in space: galaxies in today's Universe that were thought to have existed only in the distant past.

A simulation of a star forming galaxy similar to those observed. Cold gas (red) flowing onto a spiral galaxy feeds star formation. (Credit: Rob Crain, James Geach, the Virgo Consortium, Andy Green & Swinburne Astronomy Productions)

The report of his finding -- Green's first scientific paper -- appears on the cover of the Oct. 7 issue of Nature.

"We didn't think these galaxies existed. We've found they do, but they are extremely rare," said Professor Karl Glazebrook, Green's thesis supervisor and team leader.

The Swinburne researchers have likened the galaxies to the 'living dinosaurs' or Wollemi Pines of space -- galaxies you just wouldn't expect to find in today's world.

"Their existence has changed our ideas about how star formation is fuelled and understanding star formation is important. Just look at the Big Bang, which is how we all got here," Glazebrook said.

The galaxies in question look like disks, reminiscent of our own galaxy, but unlike the Milky Way they are physically turbulent and are forming many young stars.

"Such galaxies were thought to exist only in the distant past, ten billion years ago, when the Universe was less than half its present age," Glazebrook said.

"Stars form from gas, and astronomers had proposed that the extremely fast star formation in those ancient galaxies was fuelled by a special mechanism that could exist only in the early Universe -- cold streams of gas continually falling in."

But finding the same kind of galaxy in today's Universe means that that mechanism can't be the only way such rapid star formation is fuelled. Instead it seems that when young stars form, they create turbulence in their surrounding gas. The more stars are forming in a galaxy, the more turbulence it has.

"Turbulence affects how fast stars form, so we're seeing stars regulating their own formation," Green said.

"It's a bit like a little girl deciding how many siblings she should have." "We still don't know where the gas to make these stars comes from though," he said.

Understanding star formation is one of the most basic, unsolved problems of astronomy. Another significant aspect of the paper is that it was authored by a PhD student.

As Glazebrook pointed out, being first author of a Nature paper as a student is as rare as the galaxies they've discovered. This is an achievement not lost on the young scientist.

"Nature is one of the most prestigious journals in science. It was a pleasant surprise for our work to receive this kind of accolade," Green said.

The study was based on selected galaxies from the Sloan Digital Sky Survey, a kind of census of modern galaxies.

"We studied extreme galaxies to compare them with the ancient Universe," Green said.

He observed them using the Anglo-Australian Telescope (AAT) and the Australian National University's 2.3 metre telescope, both located at Siding Spring Observatory in New South Wales. Professor Matthew Colless, Director of the Australian Astronomical Observatory, which operates the AAT, said that the study highlighted the value of the instruments found at Australia's telescopes.

"They are ideal for studying in detail the nearby counterparts of galaxies seen in the distant Universe by the eight and 10 metre telescopes," he said.

For the next stage of his research, Green plans to use one of these 10 metre telescopes -- in fact the largest optical telescope in the world at the Keck Observatory -- to take an even closer look at the rare galaxies he has discovered.

Green admitted: "Really, we need a bigger telescope, the Giant Magellan Telescope, to understand star formation. But, until it's constructed, Keck is the best tool available."

Green's access to the Keck will be possible thanks to Swinburne's agreement with Caltech, which gives the Swinburne astronomers access to the Keck Observatory in Hawaii for up to 20 nights per year.

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Laws of Physics Vary Throughout the Universe, New Study Suggest

Laws of Physics Vary Throughout the Universe, New Study Suggest

  10:21:00 AM    Science Lover

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A team of astrophysicists based in Australia and England has uncovered evidence that the laws of physics are different in different parts of the universe.

Illustration of the dipolar variation in the fine-structure constant, alpha, across the sky, as seen by the two telescopes used in the work: the Keck telescope in Hawaii and the ESO Very Large Telescope in Chile. (Credit: Copyright Dr. Julian Berengut, UNSW, 2010)

The team -- from the University of New South Wales, Swinburne University of Technology and the University of Cambridge -- has submitted a report of the discovery for publication in the journal Physical Review Letters. A preliminary version of the paper is currently under peer review.

The report describes how one of the supposed fundamental constants of Nature appears not to be constant after all. Instead, this 'magic number' known as the fine-structure constant -- 'alpha' for short -- appears to vary throughout the universe.

"After measuring alpha in around 300 distant galaxies, a consistency emerged: this magic number, which tells us the strength of electromagnetism, is not the same everywhere as it is here on Earth, and seems to vary continuously along a preferred axis through the universe," Professor John Webb from the University of New South Wales said.

"The implications for our current understanding of science are profound. If the laws of physics turn out to be merely 'local by-laws', it might be that whilst our observable part of the universe favours the existence of life and human beings, other far more distant regions may exist where different laws preclude the formation of life, at least as we know it."

"If our results are correct, clearly we shall need new physical theories to satisfactorily describe them."

The researchers' conclusions are based on new measurements taken with the Very Large Telescope (VLT) in Chile, along with their previous measurements from the world's largest optical telescopes at the Keck Observatory in Hawaii.

Mr Julian King from the University of New South Wales explained how, after combining the two sets of measurements, the new result 'struck' them. "The Keck telescopes and the VLT are in different hemispheres -- they look in different directions through the universe. Looking to the north with Keck we see, on average, a smaller alpha in distant galaxies, but when looking south with the VLT we see a larger alpha."

"It varies by only a tiny amount -- about one part in 100,000 -- over most of the observable universe, but it's possible that much larger variations could occur beyond our observable horizon," Mr King said.

The discovery will force scientists to rethink their understanding of Nature's laws. "The fine structure constant, and other fundamental constants, are absolutely central to our current theory of physics. If they really do vary, we'll need a better, deeper theory," Dr Michael Murphy from Swinburne University said.

"While a 'varying constant' would shake our understanding of the world around us extraordinary claims require extraordinary evidence. What we're finding is extraordinary, no doubt about that."

"It's one of the biggest questions of modern science -- are the laws of physics the same everywhere in the universe and throughout its entire history? We're determined to answer this burning question one way or the other."

Other researchers involved in the research are Professor Victor Flambaum and PhD student Matthew Bainbridge from the University of New South Wales, and Professor Bob Carswell at the University of Cambridge (UK).

Story Source:
The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by Swinburne University of Technology.

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