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Bulging galaxy baffles
DR EMILY BALDWIN
ASTRONOMY NOW
Posted: November 18, 2009


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A recent Hubble image capturing edge-on galaxy NGC 4710 reveals a curious box-shape bulge with a faint, ethereal X-shaped structure pouring from its middle.

A faint X-shape structure is seen emanating from the boxy bulge of spiral galaxy NGC 4710. Image: NASA & ESA.

The Hubble image is part of a survey being conducted by astronomers to learn more about the evolution of galactic bulges, an ample component to most spiral galaxies. Edge-on galaxies are prime targets, since this configuration allows their bulges to be easily distinguished from the surrounding disc of material.

This extraordinarily detailed image of NGC 4710 was captured by Hubble's Advanced Camera for Surveys (ACS) and clearly reveals the galaxy's bulge and its disc, a luminous elongated white plane running through the galaxy. Both disc and bulge are pockmarked with ghostly dust lanes.

A delicate X-shaped structure can be seen emanating from the galaxy's core. Astronomers call this feature a boxy or peanut-shaped bulge, and appears due to the vertical motion of stars in the galaxy's bar. This phenomenon is only visible in edge-on galaxies and is a common occurrence in spiral galaxies with small bulges and open arms. NGC 4710, however, has spiral arms wrapped tightly around its prominent bulge.

The tuning fork diagram provides a simple way of classifying galaxies. Image: NASA.

In the standard 'tuning fork' diagram derived by Edwin Hubble to classify galaxies according to structure, NGC 4710 is an S0 or lenticular type galaxy, displaying traits common to both spiral and elliptical galaxies. Astronomers are keen to study this population of galaxy to determine how many globular clusters they host, since globular clusters may represent the processes that build bulges.

There are two contending processes for the formation of the bulges characteristic to spiral galaxies: either they formed rapidly in the early Universe, before the spiral disc and arms formed, or they built up from material accumulating from the disc during a prolonged evolution. Researchers have not seen very many globular clusters associated with NGC 4710's bulge, suggesting that its assembly mainly involved relatively slow processes.

NGC 4710 is a member of the Virgo Cluster of galaxies and lies 60 million light years from Earth in the northern constellation of Coma Berenices.

2010 Yearbook
Our latest 132-page Astronomy Now special edition is an extravaganza of astronomy for the year ahead, with a complete 30-page guide to observing the planets, moon, meteor showers, two solar eclipses, and the deep sky in 2010.
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Hubble Reborn
Hubble Reborn takes the reader on a journey through the Universe with spectacular full-colour pictures of galaxies, nebulae, planets and stars as seen through Hubble's eyes, along the way telling the dramatic story of the space telescope, including interviews with key scientists and astronauts.
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3D Universe
Witness the most awesome sights of the Universe as they were meant to be seen in this 100-page extravaganza of planets, galaxies and star-scapes, all in 3D!
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Infinity Rising
This special publication features the photography of British astro-imager Nik Szymanek and covers a range of photographic methods from basic to advanced. Beautiful pictures of the night sky can be obtained with a simple camera and tripod before tackling more difficult projects, such as guided astrophotography through the telescope and CCD imaging.
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Starry Night
Explore the Universe with these new versions of the award-winning Starry Night Software. Available now from the Astronomy Now Store.
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Exploring Mars
Astronomy Now is pleased to announce the publication of Exploring Mars. The very best images of Mars taken by orbiting spacecraft and NASA's Spirit and Opportunity rovers fill up the 98 glossy pages of this special edition!
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Mars rover poster
This new poster features some of the best pictures from NASA's amazing Mars Exploration Rovers Spirit and Opportunity.
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