HUBBLE FINDS THREE SURPRISINGLY DRY EXOPLANETS
From the News Desk of Jeanne Hambleton
Released: 24-Jul-2014 8:00 AM EDT
Source Newsroom: Space Telescope Science Institute (STScI)
Citations The Astrophysical Journal Letters, July-2014
Newswise — Astronomers using NASA’s Hubble Space Telescope have gone looking for water vapor in the atmospheres of three planets orbiting stars similar to the Sun — and have come up nearly dry.
The three planets, known as HD 189733b, HD 209458b, and WASP-12b, are between 60 and 900 light-years away from Earth and were thought to be ideal candidates for detecting water vapor in their atmospheres because of their high temperatures where water turns into a measurable vapor.
These so-called “hot Jupiters” are so close to their star they have temperatures between 1,500 and 4,000 degrees Fahrenheit, however, the planets were found to have only one-tenth to one one-thousandth the amount of water predicted by standard planet-formation theories.
“Our water measurement in one of the planets, HD 209458b, is the highest-precision measurement of any chemical compound in a planet outside our solar system, and we can now say with much greater certainty than ever before that we have found water in an exoplanet,” said Nikku Madhusudhan of the Institute of Astronomy at the University of Cambridge, England.
“However, the low water abundance we have found so far is quite astonishing.”
Madhusudhan, who led the research, said that this finding presents a major challenge to exoplanet theory.
“It basically opens a whole can of worms in planet formation. We expected all these planets to have lots of water in them. We have to revisit planet formation and migration models of giant planets, especially “hot Jupiters,” and investigate how they are formed.”
He emphasizes that these results may have major implications in the search for water in potentially habitable Earth-sized exoplanets.
Instruments on future space telescopes may need to be designed with a higher sensitivity if target planets are drier than predicted.
“We should be prepared for much lower water abundances than predicted when looking at super-Earths (rocky planets that are several times the mass of Earth),” Madhusudhan said.
Using near-infrared spectra of the planets observed with Hubble, Madhusudhan and his collaborators estimated the amount of water vapor in each of the planetary atmospheres that explains the data.
The planets were selected because they orbit relatively bright stars that provide enough radiation for an infrared-light spectrum to be taken.
Absorption features from the water vapor in the planet’s atmosphere are detected because they are superimposed on the small amount of starlight that glances through the planet’s atmosphere.
Detecting water is almost impossible for transiting planets from the ground because Earth’s atmosphere has a lot of water in it, which contaminates the observation.
“We really need the Hubble Space Telescope to make such observations,” said Nicolas Crouzet of the Dunlap Institute at the University of Toronto and co-author of the study.
The currently accepted theory on how giant planets in our solar system formed, known as core accretion, states a planet is formed around the young star in a protoplanetary disk made primarily of hydrogen, helium, and particles of ices and dust composed of other chemical elements. The dust particles stick to each other, eventually forming larger and larger grains.
The gravitational forces of the disk draw in these grains and larger particles until a solid core forms. This then leads to runaway accretion of both solids and gas to eventually form a giant planet.
This theory predicts that the proportions of the different elements in the planet are enhanced relative to those in its star, especially oxygen, which is supposed to be the most enhanced.
Once the giant planet forms, its atmospheric oxygen is expected to be largely encompassed within water molecules. The very low levels of water vapor found by this research raise a number of questions about the chemical ingredients that lead to planet formation.
“There are so many things we still do not know about exoplanets, so this opens up a new chapter in understanding how planets and solar systems form,” said Drake Deming of the University of Maryland, College Park, who led one of the precursor studies.
“The problem is that we are assuming the water to be as abundant as in our own solar system. What our study has shown is that water features could be a lot weaker than our expectations.”
The findings are published July 24 in The Astrophysical Journal Letters.
For images and more information about Hubble, visit: http://hubblesite.org/news/2014/36 and http://www.nasa.gov/hubble
The Hubble Space Telescope is a project of international cooperation between NASA and the European Space Agency. NASA’s Goddard Space Flight Center in Greenbelt, Maryland, manages the telescope. The Space Telescope Science Institute (STScI) in Baltimore, Maryland, conducts Hubble science operations. STScI is operated for NASA by the Association of Universities for Research in Astronomy, Inc., in Washington.
FLY-INSPIRED SOUND DETECTOR
New Device Based on a Fly’s Freakishly Acute Hearing May Find Applications in Futuristic Hearing Aids and Military Technology
From the News Desk of Jeanne Hambleton
Embargo expired: 22-Jul-2014 11:00 AM EDT
Source Newsroom: American Institute of Physics (AIP)
Citations Applied Physics Letters
Newswise — WASHINGTON D.C., June 22, 2014 – Even within a phylum so full of mean little creatures, the yellow-colored Ormia ochracea fly is distinguished among other arthropods for its cruelty — at least to crickets.
Native to the southeastern U.S. states and Central America, the fly is a most predatory sort of parasite. It swoops onto the back of a singing male cricket, deposits a smear of larvae, and leaves its wicked brood to invade, kill and consume the cricket from inside out.
None of this would be possible without the fly’s ability to find a cricket – the cornerstone of its parasitic lifestyle.
The fly can pinpoint the location of a chirping cricket with remarkable accuracy because of its freakishly acute hearing, which relies upon a sophisticated sound processing mechanism that really sets it apart from all other known insects.
Now a team of researchers at the University of Texas at Austin has developed a tiny prototype device that mimics the parasitic fly’s hearing mechanism, which may be useful for a new generation of hypersensitive hearing aids.
Described in the journal Applied Physics Letters, from AIP Publishing, the 2-millimeter-wide device uses piezoelectric materials, which turn mechanical strain into electric signals. The use of these materials means that the device requires very little power.
“Synthesizing the special mechanism with piezoelectric readout is a big step forward towards commercialization of the technology,” said Neal Hall, an assistant professor in the Cockrell School of Engineering at UT Austin. “Minimizing power consumption is always an important consideration in hearing-aid device technology.
There are military and defense applications as well, and Hall’s work was funded by the Defense Advanced Research Projects Agency (DARPA). In dark environments, for instance, where visual cues are not available, localizing events using sound may be critical.
Super Evolved Hearing
Humans and other mammals have the ability to pinpoint sound sources because of the finite speed of sound combined with the separation between our ears.
The spacing of several centimeters or more creates a slight difference in the time it takes sound waves to hit our ears, which the brain processes perceptually so that we can always experience our settings in surround sound.
Insects generally lack this ability because their bodies are so small that sound waves essentially hit both sides simultaneously. Many insects do detect sound vibrations, but they may rely instead on visual or chemical sensing to find their way through the fights, flights and forages of daily life.
O. ochracea is a notable exception. It can locate the direction of a cricket’s chirp even though its ears are less than 2 mm apart — a separation so slight that the time of arrival difference between its ears is only about four millionths of a second (0.000004 sec).
But the fly has evolved an unusual physiological mechanism to make the most of that tiny difference in time. What happens is in the four millionths of a second between when the sound goes in one ear and when it goes in the other, the sound phase shifts slightly.
The fly’s ear has a structure that resembles a tiny teeter-totter seesaw about 1.5 mm long.
Teeter-totters, by their very nature, vibrate such that opposing ends have 180-degree phase difference, so even very small phase differences in incident pressure waves force a mechanical motion that is 180 degrees out of phase with the other end. This effectively amplifies the four-millionths of a second time delay and allows the fly to locate its cricket prey with remarkable accuracy.
Such an ability is almost the equivalent of a human feeling an earthquake and being able to discern the direction of the epicenter by virtue of the difference in time between when the right and left foot first felt the tremor — except the fly’s hearing is even more sensitive than that, said Hall.
Mimicking the Mechanism
The pioneering work in discovering the fly’s unusual hearing mechanism was done by Ronald Miles at Binghamton University and colleagues Ronald Hoy and Daniel Robert, who first described the phase amplification mechanism the fly uses to achieve its directional hearing some 20 years ago.
In 2013, Miles, and his colleagues presented a microphone inspired by the fly’s ears. (See related release: http://newswise.com/articles/researchers-design-sensitive-new-microphone-modeled-on-fly-ear).
Inspired by Miles’s prior work, Hall and his graduate students Michael Kuntzman and Donghwan Kim built a miniature pressure-sensitive teeter-totter in silicon that has a flexible beam and integrated piezoelectric materials.
The use of piezoelectric materials was their original innovation and it allowed them to simultaneously measure the flexing and the rotation of the teeter-totter beam.
Simultaneously measuring these two vibration modes allowed them to replicate the fly’s special ability to detect sound direction in a device essentially the same size as the fly’s physiology.
This technology may be a boon for many people in the future, since 2 percent of Americans wear hearing aids, but perhaps 10 percent of the population could benefit from wearing one, Hall said.
“Many believe that the major reason for this gap is patient dissatisfaction, he added.
“Turning up the gain to hear someone across from you also amplifies all of the surrounding background noise – resembling the sound of a cocktail party.”
The new technology could enable a generation of hearing aids that have intelligent microphones that adaptively focus only on those conversations or sounds that are of interest to the wearer. But before the devices become part of the next generation of hearing aids or smartphones, more design and testing is needed.
“The delicate mechanism must be protected from consumer handling with surrounding packaging,” Hall said, “something the fly need not worry too much about.”
The article, “Sound source localization inspired by the ears of the Ormia ochracea,” is authored by Michael L. Kuntzman and Neal Hall. It will be published in the journal Applied Physics Letters on July 22, 2014.
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Applied Physics Letters features concise, rapid reports on significant new findings in applied physics. The journal covers new experimental and theoretical research on applications of physics phenomena related to all branches of science, engineering, and modern technology.
Now I know why a fly disappears as I approach him with a fly swot. He has heard me coming.