The region surrounding the reflection nebula Messier 78

This image of the region surrounding the reflection nebula Messier 78, just to the north of Orion’s belt, shows clouds of cosmic dust threaded through the nebula like a string of pearls.

The submillimeter-wavelength observations, made with the Atacama Pathfinder Experiment (APEX) telescope and shown here in orange, use the heat glow of interstellar dust grains to show astronomers where new stars are being formed.

They are overlaid on a view of the region in visible light.

Image: ESO/APEX (MPIfR/ESO/OSO)/T. Stanke et al./Igor Chekalin/Digitized Sky Survey 2

NPL to make reflected light measurements

A researcher from NIST (National Institute of Standards and Technology), the national measurement institute of the USA, recently visited the UK to utilise NPL's world-leading facilities for measuring the optical properties of materials, and specifically for measuring reflectance of samples in the infrared.

Out of all the measurement institutes around the world, NPL is capable of making these measurements over the widest range of infrared wavelengths.

In the USA, NIST is developing a fibre-coupled cryogenic radiometer that links optical fibre power measurements directly to fundamental electrical units at the 10 nW power level.

Such a device could have a role in telecommunications, medical devices and other industries that require ultra low power calibrations.

Cryogenic radiometry was first developed at NPL. It works by absorbing optical power which causes a temperature rise in the absorber.

The amount of electrical power needed to induce the same temperature rise is then measured. To make the most accurate measurements, the device needs to employ a surface that absorbs the largest amount of optical energy possible, and reflects the least.

A coating of carbon nanotubes, arranged so that they stand vertically on the surface like a forest of trees, provide this surface.

The arrangement forms the lowest reflective, or darkest, surface known to man and only NPL's facilities are capable of making the required measurements of reflected infrared light to test it.

Two facilities were used at NPL: the first, based on a grating spectrometer and integrating sphere, covers the range of the electromagnetic spectrum from visible light to a wavelength of 2.5 µm; and the second facility uses a Fourier transform spectrometer and reflecting hemisphere to cover the range from 2.5 µm to 50 µm.

The measurements made during this project represent the first ever reflectance measurements of materials with reflectance less than 1% in the 15–50 µm region and confirm that the NIST carbon nanotube coatings have the lowest known reflectance in the infrared region.

NPL and NIST have collaborated since 2003 to assess the benefits to the performance of thermal detectors obtained by using carbon nanotube coatings, and half a dozen papers have been jointly authored reporting those findings.

The current work has expanded NPL's collaboration with NIST and is described in a paper submitted for publication in a peer-reviewed journal.

More on NPL's work on Optical Radiation and Photonics

More on NPL's work on Reflected Light

For further information, please contact Christopher Chunnilall or Theo Theocharous

Alien World is Blacker than Coal

Astronomers have discovered the darkest known exoplanet – a distant, Jupiter-sized gas giant known as TrES-2b. Their measurements show that TrES-2b reflects less than one percent of the sunlight falling on it, making it blacker than coal or any planet or moon in our solar system.

“TrES-2b is considerably less reflective than black acrylic paint, so it’s truly an alien world,” said astronomer David Kipping of the Harvard-Smithsonian Center for Astrophysics (CfA), lead author on the paper reporting the research.

In our solar system, Jupiter is swathed in bright clouds of ammonia that reflect more than a third of the sunlight reaching it. In contrast, TrES-2b (which was discovered in 2006 by the Trans-Atlantic Exoplanet Survey, or TrES) lacks reflective clouds due to its high temperature.

TrES-2b orbits its star at a distance of only three million miles. The star’s intense light heats TrES-2b to a temperature of more than 1,800° Fahrenheit – much too hot for ammonia clouds.

Instead, its exotic atmosphere contains light-absorbing chemicals like vaporized sodium and potassium, or gaseous titanium oxide. Yet none of these chemicals fully explain the extreme blackness of TrES-2b.

“It’s not clear what is responsible for making this planet so extraordinarily dark,” stated co-author David Spiegel of Princeton University. “However, it’s not completely pitch black. It’s so hot that it emits a faint red glow, much like a burning ember or the coils on an electric stove.”

Kipping and Spiegel determined the reflectivity of TrES-2b using data from NASA’s Kepler spacecraft. Kepler is designed to measure the brightnesses of distant stars with extreme precision.

The team monitored the brightness of the TrES-2 system as the planet orbited its star. They detected a subtle dimming and brightening due to the planet’s changing phase.

TrES-2b is believed to be tidally locked like our moon, so one side of the planet always faces the star and like our moon, the planet shows changing phases as it orbits its star.

This causes the total brightness of the star plus planet to vary slightly.

“By combining the impressive precision from Kepler with observations of over 50 orbits, we detected the smallest-ever change in brightness from an exoplanet: just 6 parts per million,” said Kipping. “In other words, Kepler was able to directly detect visible light coming from the planet itself.”

The extremely small fluctuations proved that TrES-2b is incredibly dark. A more reflective world would have shown larger brightness variations as its phase changed.

Kepler has located more than 1,200 planetary candidates in its field of view. Additional analysis will reveal whether any other unusually dark planets lurk in that data.

TrES-2b orbits the star GSC 03549-02811, which is located about 750 light-years away in the direction of the constellation Draco. (One light-year is about 6 trillion miles.)

This research has been accepted for publication in the Monthly Notices of the Royal Astronomical Society .

For more information on NASA’s Kepler mission, visit: http://www.nasa.gov/kepler.

On Reflection, A Bigger Brain

“We introspect when we think about our own thoughts, feelings, or the decisions we have made,” says Steve Fleming, joint first author of the study and a researcher at University College London. “It’s something we do all the time, but some people are better at it than others. Even if we don’t get feedback when we make a choice, we often know intuitively if it’s a good or a bad decision.”

Full story at Futurity.

ESA Astronaut Fugelsang reflection in Olivas's Visor

ON Reflection

European Space Agency (ESA) astronaut Christer Fuglesang is visible in the reflection of NASA astronaut Danny Olivas's helmet visor during this, the STS-128 mission's third and final spacewalk.

Olivas and Fuglesang deployed the Payload Attachment System, replaced the Rate Gyro Assembly #2, installed two GPS antennae and worked to prepare for the installation of Node 3 next year.

Reflecting on Earthshine

The moon will be full Thursday, which means we'll see it in all its illuminated glory. But when the moon is just a sliver, we sometimes see our own reflection shining back at us from the moon's shrouded side, in a phenomenon called "earthshine."

Now scientists say the difference in light reflection from the Earth's land masses vs. the oceans can be seen on the moon. By tracking changes in earthshine as Earth rotates, scientists measured brightness variations that correspond to the brilliant, mirror-like reflections from oceans compared to the dimmer reflections from land.

Earthshine was first proposed by Leonardo da Vinci, who suggested that sunlight could bounce off our planet and be reflected back to us by the moon. This light is only visible when there is little sunlight reflecting directly off the moon, which would otherwise drown out the much dimmer earthshine. Thus, Earth's reflection is only visible to the naked eye on the darker portion of thin crescent moons, and not full moons.

The phenomenon can sometimes be seen by the naked eye as a ghostly glow, and is easily visible with a telescope. It is best seen once a month when the crescent moon hangs just above the western horizon right after sunset.