The Milk Way’s Magnetic Field

The_magnetic_field_along_the_Galactic_plane_node_full_image_2This image looks like it was lifted from something by Van Gogh. The pastel tones and fine texture remind me of the brush strokes on one of the artist’s canvases. In fact, the picture is a visualization of data from ESA’s Planck satellite detailing the interaction between interstellar dust in the Milky Way and the structure of our Galaxy’s magnetic field.

Between 2009 and 2013, Planck scanned the sky to detect the Cosmic Microwave Background, the oldest light in the history of the Universe. It also detected significant foreground emission from diffuse material in our Galaxy which, although a nuisance for cosmological studies, is extremely important for studying the birth of stars and other phenomena in the Milky Way. One of the foreground sources at the wavelengths scanned is cosmic dust, a minor but crucial component of the interstellar medium that pervades the Galaxy. It’s mostly gas, and it is the raw material for stars to form.

These interstellar clouds of gas and dust are shepherded by the Galaxy’s magnetic field. The dust grains tend to align their longest axis at right angles to the direction of the field. As a result, the light emitted by dust grains is partly polarized. It vibrates in a preferred direction. From these and other similar observations, scientists found that filamentary interstellar clouds are preferentially aligned with the direction of the ambient magnetic field, suggesting a strong role played by magnetism in galaxy evolution.

The color scale of the image represents the total intensity of dust emission, revealing the structure of interstellar clouds in the Milky Way. The texture is based on measurements of the direction of the polarised light emitted by the dust, which in turn indicates the orientation of the magnetic field. The arrangement of the magnetic field is more orderly along the Galactic plane, where it follows the Galaxy’s spiral structure. Small clouds are seen just above and below the plane, where the magnetic field structure becomes less regular.

Image Credit: ESA / Planck Collaboration.
Acknowledgment: M.-A. Miville-Deschênes, CNRS – Institut d’Astrophysique Spatiale, Université Paris-XI, Orsay, France

NGC 4102

This is no supermodel spiralNGC 4102 lies in the northern constellation of Ursa Major (The Great Bear). It contains what is known as a LINER, or low-ionization nuclear emission-line region. That means its nucleus emits particular types of radiation, emission from weakly-ionised or neutral atoms of certain elements. That’s not very unusual. About one third of all nearby galaxies are thought to be LINER galaxies.

Many LINER galaxies also contain intense regions of star formation. This is thought to be intrinsically linked to their galactic centers, but the reason why is still a mystery. It may be that the starbursts pour fuel inwards to fuel the LINERs, or this active central region might trigger the starbursts. NGC 4102 does indeed contain a starburst region near its center where stars are being created at a more rapid rate than in a normal galaxy.

Image Credit: NASA / ESA

The Riddle of the Missing Stars

Directed by: Georgia Bladon
Visual design and editing: Martin Kornmesser
Written by: Georgia Bladon and Nicky Guttridge
Narration: Sara Mendes da Costa
Images: NASA, ESA/Hubble
Videos: NASA, ESA/Hubble
Animations: Martin Kornmesser, NASA, ESA/Hubble
Music: Jennifer Athena Galatis
Web and technical support: Mathias Andre and Raquel Yumi Shida
Executive producer: Lars Lindberg Christensen

NGC 986

A spiral in a furnaceNGC 986 is found in the constellation of Fornax (The Furnace), located in the southern sky. NGC 986 is around 56 million light-years away, and its golden center and barred swirling arms are clearly visible in this image assembled from data captured by Hubble’s Wide Field and Planetary Camera 2. (The stars in the upper right appear a little fuzzy because a gap in the Hubble data was filled in with images from ground-based telescopes. The view  is accurate, but the resolution is no match for Hubble.)

Barred spiral galaxies are spiral galaxies with stars forming a central bar-shaped structure. NGC 986 has the characteristic S-shaped structure of this type of galaxy. Young blue stars can be seen dotted through the galaxy’s arms, and the core is also alight with star formation.

Image Credit: NASA / ESA

Following the Bouncing Lander

OSIRIS_spots_PhilaeThis mosaic was assembled from a series of images captured by Rosetta’s OSIRIS camera taken over the half-hour spanning the first touchdown of the Philae lander Comet 67P/CG. The time of each of image is marked on the corresponding insets and is in UTC. A comparison of the touchdown area shortly before and after first contact with the surface is shown at the top.

The images were taken with the OSIRIS narrow-angle camera when the spacecraft was 17.5 km from the comet centre, or roughly 15.5 km from the surface. The enlarged insets cover a 17 x 17 m area.

From left to right, the images show Philae descending towards and across the comet before touchdown. The image taken after touchdown, at 15:43 GMT, confirms that the lander was moving east at a speed of about 0.5 m/s as it bounced across the surface of the comet.

Philae‘s actual final landing spot still hasn’t been found. After touching down and bouncing again at 17:25 UTC, it finally landed at 17:32. The mission imaging team believes that by combining the CONSERT ranging data with OSIRIS and navcam images from the orbiter and images from near the surface with data from Philae’s ROLIS and CIVA cameras they will be able to determine the lander’s whereabouts.

Image Credit: ESA

On the Surface of a Comet

Welcome_to_a_cometThe Rosetta mission lander is “safely” on the surface of its comet. One of Philae‘s feet can be seen at the bottom left of this picture of the surface of C67/P Churyumov-Gerasimenko. Philae bounced twice before settling and returning images from the surface, traveling a kilometer or so after ricocheting off of its desired target. A surface panorama suggests that the lander has come to rest tilted and near a shadowing wall. The lander’s solar panels are getting less illumination than if it had landed in the open. The science instruments are working as planned and data is being relayed when the main Rosetta spacecraft is above the lander’s new horizon. However, with good recharging from the solar array, the batteries will not last as long as had been hoped.

Image Credit: ESA