White Dwarfs hold the key to detecting Life on other Planets

Because it has no source of energy, a dead star—known as a white dwarf—will eventually cool down and fade away but circumstantial evidence suggests that white dwarfs can still support habitable planets, says Prof. Dan Maoz of Tel Aviv University's School of Physics and Astronomy.

Now Prof. Maoz and Prof. Avi Loeb, Director of Harvard University's Institute for Theory and Computation and a Sackler Professor by Special Appointment at TAU, have shown that, using advanced technology to become available within the next decade, it should be possible to detect biomarkers surrounding these planets—including oxygen and methane—that indicate the presence of life.

Dan Maoz

Published in the Monthly Notices of the Royal Astronomical Society, the researchers' "simulated spectrum" demonstrates that the James Webb Space Telescope (JWST), set to be launched by NASA in 2018, will be capable of detecting oxygen and water in the atmosphere of an Earth-like planet orbiting a white dwarf after only a few hours of observation time—much more easily than for an Earth-like planet orbiting a sun-like star.

Their collaboration is made possible by the Harvard TAU Astronomy Initiative, recently endowed by Dr. Raymond and Beverly Sackler.

Faint light, clear signals
"In the quest for extraterrestrial biological signatures, the first stars we study should be white dwarfs," said Prof. Loeb.

Prof. Loeb

Prof. Maoz agrees, noting that if "all the conditions are right, we'll be able to detect signs of life" on planets orbiting white dwarf stars using the much-anticipated JWST.

An abundance of heavy elements already observed on the surface of white dwarfs suggest rocky planets orbit a significant fraction of them.

The researchers estimate that a survey of 500 of the closest white dwarfs could spot one or more habitable planets.

The unique characteristics of white dwarfs could make these planets easier to spot than planets orbiting normal stars, the researchers have shown.

Their atmospheres can be detected and analyzed when a star dims as an orbiting planet crosses in front of it.

James Watt Space Telescope - JWST

As the background starlight shines through the planet's atmosphere, elements in the atmosphere will absorb some of the starlight, leaving chemical clues of their presence—clues that can then be detected from the JWST.

When an Earth-like planet orbits a normal star, "the difficulty lies in the extreme faintness of the signal, which is hidden in the glare of the 'parent' star," Prof. Maoz says.

"The novelty of our idea is that, if the parent star is a white dwarf, whose size is comparable to that of an Earth-sized planet, that glare is greatly reduced, and we can now realistically contemplate seeing the oxygen biomarker."

In order to estimate the kind of data that the JWST will be able to see, the researchers created a "synthetic spectrum," which replicates that of an inhabited planet similar to Earth orbiting a white dwarf.

They demonstrated that the telescope should be able to pick up signs of oxygen and water, if they exist on the planet.

Detecting land mines with sound

Detecting land mines with sound

The researchers built a prototype detector and tested it at the Cold Regions Research and Engineering Laboratory Army Corps of Engineers land-mine facility in New Hampshire. They were able to detect both metal and plastic mines but said that the system will have to get a major boost in acoustic power before minefield searchers can use it safely.

Robert W. Haupt, a technical staff member at Lincoln Lab, explores innovative ways to find and reduce the large number of land mines abandoned in war-torn countries. An estimated 26,000 people are killed or maimed every year by 60 to 70 million undetected land mines in 70 countries. Those casualties include military troops but most are civilians--half of them children under age 16--who step on uncleared minefields after a war.

Many existing prototype mine detection systems can detect only metal, have limited range or are impractical in the field. "Reliable methods that quickly and accurately locate land mines made of metal and plastic, unexploded ordnance and other mine-like targets are desperately needed," Haupt said.

Haupt and fellow Lincoln Lab staff member Ken Rolt developed a high-powered sound transmitter that looks like a stop sign studded with 35mm film canisters or prescription pill containers. This is called a parametric acoustic array, and Haupt and Rolt have built one of the most powerful ones around.

The array is made up of ceramic transducers--devices that emit a powerful narrow acoustic beam at ultrasonic frequencies. One meter away, the ultrasonic pressure level measures 155 decibels--more acoustic power than a jet engine. Immediately outside the beam, the acoustic intensity dies away to almost nothing.

By a process know as self-demodulation, the air in front of the acoustic beam converts the ultrasound to much lower frequency audible tones that sound like extremely loud tuning forks. Unlike ultrasound, the low-frequency sound can penetrate the ground, causing detectable vibrations in the mine's plungers and membranes.

"The use of ultrasound allows us to make a very narrow and highly directional beam, like a sound flashlight," Haupt said. It would take a huge number of conventional loudspeakers to do the same trick, and they would weigh too much, take up too much space and use too much power to be practical, he said. Plus, they would deafen anyone within earshot. "Using a narrow sound beam, we can put sound just where we want it, and we can minimize sound levels outside the beam to avoid harming the operators or people nearby," he said.

NASA: WISE Telescope Detecting Near Earth Asteroids

NASA's Wide-field Infrared Survey Explorer, or WISE, has spotted its first never-before-seen near-Earth asteroid, the first of hundreds it is expected to find during its mission to map the whole sky in infrared light.

The near-Earth object, designated 2010 AB78, was discovered by WISE Jan. 12. After the mission's sophisticated software picked out the moving object against a background of stationary stars, researchers followed up and confirmed the discovery with the University of Hawaii's 2.2-meter (88-inch) visible-light telescope near the summit of Mauna Kea.

The asteroid is currently about 158 million kilometers (98 million miles) from Earth. It is estimated to be roughly 1 kilometer (0.6 miles) in diameter and circles the sun in an elliptical orbit tilted to the plane of our solar system. The object comes as close to the sun as Earth, but because of its tilted orbit, it is not thought to pass near our planet. This asteroid does not pose any foreseeable impact threat to Earth, but scientists will continue to monitor it.

WISE, which began its all-sky survey on Jan. 14, is expected to find about 100-thousand previously undiscovered asteroids in the Main Belt between Mars and Jupiter, and hundreds of new near-Earth asteroids. It will also spot millions of new stars and galaxies.