ESO: Hints of first signs of a weird quantum property of empty space

The latest report from ESO (European Southern Observatory:

First Signs of Weird Quantum Property of Empty Space?
VLT observations of neutron star may confirm
80-year-old prediction about the vacuum

By studying the light emitted from an extraordinarily dense and strongly magnetised neutron star using ESO’s Very Large Telescope, astronomers may have found the first observational indications of a strange quantum effect, first predicted in the 1930s. The polarisation of the observed light suggests that the empty space around the neutron star is subject to a quantum effect known as vacuum birefringence.

This artist’s view shows how the light coming from the surface of a strongly magnetic neutron star (left) becomes linearly polarised as it travels through the vacuum of space close to the star on its way to the observer on Earth (right). The polarisation of the observed light in the extremely strong magnetic field suggests that the empty space around the neutron star is subject to a quantum effect known as vacuum birefringence, a prediction of quantum electrodynamics (QED). This effect was predicted in the 1930s but has not been observed before. The magnetic and electric field directions of the light rays are shown by the red and blue lines. Model simulations by Roberto Taverna (University of Padua, Italy) and Denis Gonzalez Caniulef (UCL/MSSL, UK) show how these align along a preferred direction as the light passes through the region around the neutron star. As they become aligned the light becomes polarised, and this polarisation can be detected by sensitive instruments on Earth.
This artist’s view shows how the light coming from the surface of a strongly magnetic neutron star (left) becomes linearly polarised as it travels through the vacuum of space close to the star on its way to the observer on Earth (right). The polarisation of the observed light in the extremely strong magnetic field suggests that the empty space around the neutron star is subject to a quantum effect known as vacuum birefringence, a prediction of quantum electrodynamics (QED). This effect was predicted in the 1930s but has not been observed before. The magnetic and electric field directions of the light rays are shown by the red and blue lines. Model simulations by Roberto Taverna (University of Padua, Italy) and Denis Gonzalez Caniulef (UCL/MSSL, UK) show how these align along a preferred direction as the light passes through the region around the neutron star. As they become aligned the light becomes polarised, and this polarisation can be detected by sensitive instruments on Earth. [Larger images]
A team led by Roberto Mignani from INAF Milan (Italy) and from the University of Zielona Gora (Poland), used ESO’s Very Large Telescope (VLT) at the Paranal Observatory in Chile to observe the neutron star RX J1856.5-3754, about 400 light-years from Earth [1].

Despite being amongst the closest neutron stars, its extreme dimness meant the astronomers could only observe the star with visible light using the FORS2 instrument on the VLT, at the limits of current telescope technology.

This artist’s view shows how the light coming from the surface of a strongly magnetic neutron star (left) becomes linearly polarised as it travels through the vacuum of space close to the star on its way to the observer on Earth (right). The polarisation of the observed light in the extremely strong magnetic field suggests that the empty space around the neutron star is subject to a quantum effect known as vacuum birefringence, a prediction of quantum electrodynamics (QED). This effect was predicted in the 1930s but has not been observed before.

The magnetic and electric field directions of the light rays are shown by the red and blue lines. Model simulations by Roberto Taverna (University of Padua, Italy) and Denis Gonzalez Caniulef (UCL/MSSL, UK) show how these align along a preferred direction as the light passes through the region around the neutron star. As they become aligned the light becomes polarised, and this polarisation can be detected by sensitive instruments on Earth. CreditESO/L. Calçada

Neutron stars are the very dense remnant cores of massive stars — at least 10 times more massive than our Sun — that have exploded as supernovae at the ends of their lives. They also have extreme magnetic fields, billions of times stronger than that of the Sun, that permeate their outer surface and surroundings.

This wide field image shows the sky around the very faint neutron star RX J1856.5-3754 in the southern constellation of Corona Australis. This part of the sky also contains interesting regions of dark and bright nebulosity surrounding the variable star R Coronae Australis (upper left), as well as the globular star cluster NGC 6723. The neutron star itself is too faint to be seen here, but lies very close to the centre of the image.
This wide field image shows the sky around the very faint neutron star RX J1856.5-3754 in the southern constellation of Corona Australis. This part of the sky also contains interesting regions of dark and bright nebulosity surrounding the variable star R Coronae Australis (upper left), as well as the globular star cluster NGC 6723. The neutron star itself is too faint to be seen here, but lies very close to the centre of the image. [Larger images]
These fields are so strong that they even affect the properties of the empty space around the star. Normally a vacuum is thought of as completely empty, and light can travel through it without being changed. But in quantum electrodynamics (QED), the quantum theory describing the interaction between photons and charged particles such as electrons, space is full of virtual particles that appear and vanish all the time. Very strong magnetic fields can modify this space so that it affects the polarisation of light passing through it.

Mignani explains:

“According to QED, a highly magnetised vacuum behaves as a prism for the propagation of light, an effect known as vacuum birefringence.”

Among the many predictions of QED, however, vacuum birefringence so far lacked a direct experimental demonstration. Attempts to detect it in the laboratory have not yet succeeded in the 80 years since it was predicted in a paper by Werner Heisenberg (of uncertainty principle fame) and Hans Heinrich Euler.

“This effect can be detected only in the presence of enormously strong magnetic fields, such as those around neutron stars. This shows, once more, that neutron stars are invaluable laboratories in which to study the fundamental laws of nature.”

says Roberto Turolla (University of Padua, Italy).

eso1641c1
Colour composite photo of the sky field with the lonely neutron star RX J1856.5-3754 and the related cone-shaped nebula. It is based on a series of exposures obtained with the multi-mode FORS2 instrument at VLT KUEYEN through three different optical filters. The trail of an asteroid is seen in the field with intermittent blue, green and red colours. Credit: ESO [Larger images]
After careful analysis of the VLT data, Mignani and his team detected linear polarisation — at a significant degree of around 16% — that they say is likely due to the boosting effect of vacuum birefringence occurring in the area of empty space surrounding RX J1856.5-3754 [2].

“This is the faintest object for which polarisation has ever been measured. It required one of the largest and most efficient telescopes in the world, the VLT, and accurate data analysis techniques to enhance the signal from such a faint star.”

[- Vincenzo Testa (INAF, Rome, Italy) comments.]

“The high linear polarisation that we measured with the VLT can’t be easily explained by our models unless the vacuum birefringence effects predicted by QED are included,”

adds Mignani.

“This VLT study is the very first observational support for predictions of these kinds of QED effects arising in extremely strong magnetic fields,”

remarks Silvia Zane  (UCL/MSSL, UK).

Mignani is excited about further improvements to this area of study that could come about with more advanced telescopes:

“Polarisation measurements with the next generation of telescopes, such as ESO’s European Extremely Large Telescope, could play a crucial role in testing QED predictions of vacuum birefringence effects around many more neutron stars.”

[Adds Kinwah Wu (UCL/MSSL, UK): ]

“This measurement, made for the first time now in visible light, also paves the way to similar measurements to be carried out at X-ray wavelengths,”

This video sequence takes us from a broad view of the spectacular central regions of the Milky Way deep into the small constellation of Corona Australis. Here, as well as seeing clouds of glowing gas and dark regions of dust, we find the very faint neutron star RX J1856.5-3754. This extremely dense and magnetic object is the first place that indications of a strange quantum effect called vacuum birefringence may have been detected in new observations made using ESO’s Very Large Telescope. Credit: ESO/N. Risinger (skysurvey.org)/Digitized Sky Survey 2

Notes

[1] This object is part of the group of neutron stars known as the Magnificent Seven. They are known as isolated neutron stars (INS), which have no stellar companions, do not emit radio waves (like pulsars), and are not surrounded by progenitor supernova material.

[2] There are other processes that can polarise starlight as it travels through space. The team carefully reviewed other possibilities — for example polarisation created by scattering off dust grains — but consider it unlikely that they produced the polarisation signal observed.

Cassini takes a great shot of Mimas, Saturn and the rings

The Cassini spacecraft takes a wonderful image of the Saturn, its rings, and the small moon Mimas:

Tiny Mimas, Huge Rings

Saturn’s icy moon Mimas is dwarfed by the planet’s enormous rings.

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The moon Mimas is dwarfed by Saturn and its beautiful rings, which cast stripped shadows on the gas giant. (Larger image.)

Because Mimas (near lower left) appears tiny by comparison, it might seem that the rings would be far more massive, but this is not the case. Scientists think the rings are no more than a few times as massive as Mimas, or perhaps just a fraction of Mimas’ mass. Cassini is expected to determine the mass of Saturn’s rings to within just a few hundredths of Mimas’ mass as the mission winds down by tracking radio signals from the spacecraft as it flies close to the rings.

The rings, which are made of small, icy particles spread over a vast area, are extremely thin – generally no thicker than the height of a house. Thus, despite their giant proportions, the rings contain a surprisingly small amount of material.

Mimas is 246 miles (396 kilometers) wide.

This view looks toward the sunlit side of the rings from about 6 degrees above the ring plane. The image was taken in red light with the Cassini spacecraft wide-angle camera on July 21, 2016.

The view was obtained at a distance of approximately 564,000 miles (907,000 kilometers) from Saturn and at a Sun-Saturn-spacecraft, or phase, angle of 31 degrees. Image scale is 34 miles (54 kilometers) per pixel.

The Cassini mission is a cooperative project of NASA, ESA (the European Space Agency) and the Italian Space Agency. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the mission for NASA’s Science Mission Directorate, Washington. The Cassini orbiter and its two onboard cameras were designed, developed and assembled at JPL. The imaging operations center is based at the Space Science Institute in Boulder, Colorado.

For more information about the Cassini-Huygens mission visit saturn.jpl.nasa.gov and www.nasa.gov/cassini. The Cassini imaging team homepage is at ciclops.org.

Credit: NASA/JPL-Caltech/Space Science Institute

The Space Show this week – Nov.28.2016

The guests and topics of discussion on The Space Show this week:

1. Monday, Nov. 28, 2016: 2-3:30 PM PST (5-6:30 PM EST, 4-5:30 PM CST): No show as part of holiday weekend.

2. Tuesday, Nov. 29, 2016: 2016: 7-8:30 PM PST, 10-11:30 PM EST, 9-10:30 PM CST: We welcome back MARK WHITTINGTON regarding his new space policy and lunar ideas.

3. Friday, Dec. 2, 2016: 9:30-11AM PST; (12:30-2 PM EST; 11:30 AM – 1 PM CST) We welcome DR. SUSANNE PETERS from Germany to discuss innovative space debris solutions.

4. Sunday, Dec. 4, 2016: 12-1:30 PM PST (3-4:30 PM EST, 2-3:30 5PM CST): We welcome back BARRY LEVIN to continue our discussion of advanced manufacturing for space and the 4th industrial revolution. 3D printing is on the table for this program.

See also:
* The Space Show on Vimeo – webinar videos
* The Space Show’s Blog – summaries of interviews.
* The Space Show Classroom Blog – tutorial programs

The Space Show is a project of the One Giant Leap Foundation.

The Space Show - David Livingston
David Livingston

Radar study finds Mars ice deposit with water comparable to Lake Superior

A huge underground deposit of water has been detected on Mars:

Mars Ice Deposit Holds as Much Water as Lake Superior

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This vertically exaggerated view shows scalloped depressions in a part of Mars where such textures prompted researchers to check for buried ice, using ground-penetrating radar aboard NASA’s Mars Reconnaissance Orbiter. Image Credit: NASA/JPL-Caltech/Univ. of Arizona › Full image and caption

Frozen beneath a region of cracked and pitted plains on Mars lies about as much water as what’s in Lake Superior, largest of the Great Lakes, researchers using NASA’s Mars Reconnaissance Orbiter have determined.

Scientists examined part of Mars’ Utopia Planitia region, in the mid-northern latitudes, with the orbiter’s ground-penetrating Shallow Radar (SHARAD) instrument. Analyses of data from more than 600 overhead passes with the onboard radar instrument reveal a deposit more extensive in area than the state of New Mexico. The deposit ranges in thickness from about 260 feet (80 meters) to about 560 feet (170 meters), with a composition that’s 50 to 85 percent water ice, mixed with dust or larger rocky particles.


Fast Facts:

› Water ice makes up half or more of an underground layer in a large region of Mars about halfway from the equator to the north pole.

› The amount of water in this deposit is about as much as in Lake Superior. It was assessed using a radar aboard a NASA spacecraft orbiting Mars.

› This research advances understanding about Mars’ history and identifies a possible resource for future astronauts.


At the latitude of this deposit — about halfway from the equator to the pole — water ice cannot persist on the surface of Mars today. It sublimes into water vapor in the planet’s thin, dry atmosphere. The Utopia deposit is shielded from the atmosphere by a soil covering estimated to be about 3 to 33 feet (1 to 10 meters) thick.

“This deposit probably formed as snowfall accumulating into an ice sheet mixed with dust during a period in Mars history when the planet’s axis was more tilted than it is today,”

said Cassie Stuurman of the Institute for Geophysics at the University of Texas, Austin. She is the lead author of a report in the journal Geophysical Research Letters.

This vertically exaggerated view shows scalloped depressions in a part of Mars where such textures prompted researchers to check for buried ice, using ground-penetrating radar aboard NASA's Mars Reconnaissance Orbiter. Image Credit: NASA/JPL-Caltech/Univ. of Arizona
This vertically exaggerated view shows scalloped depressions in a part of Mars where such textures prompted researchers to check for buried ice, using ground-penetrating radar aboard NASA’s Mars Reconnaissance Orbiter. Image Credit: NASA/JPL-Caltech/Univ. of Arizona › Full image and caption

Mars today, with an axial tilt of 25 degrees, accumulates large amounts of water ice at the poles. In cycles lasting about 120,000 years, the tilt varies to nearly twice that much, heating the poles and driving ice to middle latitudes. Climate modeling and previous findings of buried, mid-latitude ice indicate that frozen water accumulates away from the poles during high-tilt periods.

Martian Water as a Future Resource

The name Utopia Planitia translates loosely as the “plains of paradise.” The newly surveyed ice deposit spans latitudes from 39 to 49 degrees within the plains. It represents less than one percent of all known water ice on Mars, but it more than doubles the volume of thick, buried ice sheets known in the northern plains. Ice deposits close to the surface are being considered as a resource for astronauts.

“This deposit is probably more accessible than most water ice on Mars, because it is at a relatively low latitude and it lies in a flat, smooth area where landing a spacecraft would be easier than at some of the other areas with buried ice,”

said Jack Holt of the University of Texas, a co-author of the Utopia paper who is a SHARAD co-investigator and has previously used radar to study Martian ice in buried glaciers and the polar caps.

The Utopian water is all frozen now. If there were a melted layer — which would be significant for the possibility of life on Mars — it would have been evident in the radar scans. However, some melting can’t be ruled out during different climate conditions when the planet’s axis was more tilted.

“Where water ice has been around for a long time, we just don’t know whether there could have been enough liquid water at some point for supporting microbial life,” Holt said.

Mars Ice Deposit Holds as Much Water as Lake Superior Subsurface Water-Ice Deposit in Utopia Planitia, MarsScalloped Terrain Led to Finding of Buried Ice on MarsRadargrams Indicating Ice-Rich Subsurface Deposit These two images show Shallow Radar (SHARAD) instrument data from two tracks in a part of Mars' Utopia Planitia region where the orbiting, ground-penetrating radar on NASA's Mars Reconnaissance Orbiter detected subsurface deposits rich in water ice. Image Credit: NASA/JPL-Caltech/Univ. of Rome/ASI/PSI
Mars Ice Deposit Holds as Much Water as Lake Superior Subsurface Water-Ice Deposit in Utopia Planitia, MarsScalloped Terrain Led to Finding of Buried Ice on MarsRadargrams Indicating Ice-Rich Subsurface Deposit These two images show Shallow Radar (SHARAD) instrument data from two tracks in a part of Mars’ Utopia Planitia region where the orbiting, ground-penetrating radar on NASA’s Mars Reconnaissance Orbiter detected subsurface deposits rich in water ice. Image Credit: NASA/JPL-Caltech/Univ. of Rome/ASI/PSI › Full image and caption

Utopia Planitia is a basin with a diameter of about 2,050 miles (3,300 kilometers), resulting from a major impact early in Mars’ history and subsequently filled. NASA sent the Viking 2 Lander to a site near the center of Utopia in 1976. The portion examined by Stuurman and colleagues lies southwest of that long-silent lander.

Use of the Italian-built SHARAD instrument for examining part of Utopia Planitia was prompted by Gordon Osinski at Western University in Ontario, Canada, a co-author of the study. For many years, he and other researchers have been intrigued by ground-surface patterns there such as polygonal cracking and rimless pits called scalloped depressions — “like someone took an ice-cream scoop to the ground,” said Stuurman, who started this project while a student at Western.

Clue from Canada

In the Canadian Arctic, similar landforms are indicative of ground ice, Osinski noted,

“but there was an outstanding question as to whether any ice was still present at the Martian Utopia or whether it had been lost over the millions of years since the formation of these polygons and depressions.”

The large volume of ice detected with SHARAD advances understanding about Mars’ history and identifies a possible resource for future use.

“It’s important to expand what we know about the distribution and quantity of Martian water,” said Mars Reconnaissance Orbiter Deputy Project Scientist Leslie Tamppari, of NASA’s Jet Propulsion Laboratory, Pasadena, California. “We know early Mars had enough liquid water on the surface for rivers and lakes. Where did it go? Much of it left the planet from the top of the atmosphere. Other missions have been examining that process. But there’s also a large quantity that is now underground ice, and we want to keep learning more about that.”

Joe Levy of the University of Texas, a co-author of the new study, said,

“The ice deposits in Utopia Planitia aren’t just an exploration resource, they’re also one of the most accessible climate change records on Mars. We don’t understand fully why ice has built up in some areas of the Martian surface and not in others. Sampling and using this ice with a future mission could help keep astronauts alive, while also helping them unlock the secrets of Martian ice ages.”

SHARAD is one of six science instruments on the Mars Reconnaissance Orbiter, which began its prime science phase 10 years ago this month. The mission’s longevity is enabling studies of features and active processes all around Mars, from subsurface to upper atmosphere. The Italian Space Agency provided the SHARAD instrument and Sapienza University of Rome leads its operations. The Planetary Science Institute, based in Tucson, Arizona, leads U.S. involvement in SHARAD. JPL, a division of Caltech in Pasadena, manages the orbiter mission for NASA’s Science Mission Directorate in Washington. Lockheed Martin Space Systems of Denver built the spacecraft and supports its operations.

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