A Dwarf Galaxy

A messy star factoryThis is the blue compact dwarf galaxy known as Markarian 209. Because galaxies of this type are rich in gas and poor in heavy elements, astronomers use them to study star formation. Such conditions are believed to be similar to those existing in the early Universe. Markarian 209 has been studied extensively. It is filled with diffuse gas and peppered with star-forming regions towards its core. The lighter blue cloudy region towards the top right of the galaxy is filled with very young and hot newborn stars.

It was initially thought to be a young galaxy undergoing its initial period of star formation. However, research showed that Markarian 209 is actually very old. It is thought to have never had a dormant period with no stars forming that lasted for longer than 100 million years. Most of stars in Markarian 209 are quite young, under 3 million years old. Our Sun is around 4.6 billion years old.

A scattering of other bright galaxies can be seen across the frame of this Hubble image, including the bright golden oval that could be mistaken as part of Markarian 209 but is in fact a background galaxy.

Image Credit: ESA / NASA
Acknowledgement: Nick Rose

A Comet in Color …

ESA_Rosetta_OSIRIS_Color… but not a very much color. Rosetta’s OSIRIS team have produced a color image of Comet 67P/Churyumov-Gerasimenko as it would be seen by the human eye. The comet turns out to be very grey indeed, with only subtle color variations across its surface.

This picture was assembled from three images taken with the Narrow Angle Camera (NAC) of the scientific imaging system OSIRIS in red (744 nm wavelength), green (536 nm), and blue (481 nm) filters on 6 August 2014, from a distance of 120 kilometres. The image area is roughly 4 km square.

Image Credit: ESA


The star cluster Messier 47This picture of the star cluster Messier 47 was taken using the Wide Field Imager camera, installed on the MPG/ESO 2.2-metre telescope at ESO’s La Silla Observatory in Chile. The young open cluster is dominated by a sprinkling of brilliant blue stars but also contains a few contrasting red giant stars.

Image Credit: ESO

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