martes, 3 de abril de 2012

We can't see the Milky Way's woods for its trees


New Scientist. Home | Opinion
  • 28 March 2012
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YOU might be forgiven for assuming that the Milky Way, our home galaxy, holds few mysteries. But you would be wrong. There is still a huge amount we don't understand about it, from its dense centre to its sparse outskirts (see "Mysteries of the Milky Way").
Strikingly, some of these mysteries arise precisely because they are situated right on our cosmic doorstep. For example, our location makes it hard to tell where the galaxy's spiral arms lie, or even how many of them there actually are. We know the forms of far-flung galaxies much better than we do our own.
We have been here before. Geographers had to undertake globe-trotting odysseys to establish the true shape of the Earth - a quest now handled by orbiting satellites. Satellites have also revealed geological structures and archaeological sites that are all but invisible to observers on the ground, to ...
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Mysteries of the Milky Way

(Image: Luis Argerich/Getty Images)

From its furthest dark-matter-spattered reaches to the black hole at its core, Stephen Battersby explores 11 enigmas of our galaxy
QUANTUM WORLD

Antimatter factory

Positron powerhouse <i>(Image: Visuals Unlimited/Carol & Mike Werner/Getty)</i>
Our galaxy produces 10 billion tonnes of antimatter every second. What could be pumping out so many positrons?
Read more
MAPPING

Our galaxy's shape

Our ticket's not valid <i>(Image: Samuel Arbesman/NTI Media Ltd/Rex Features)</i>
Our lowly viewpoint in the galactic disc means we struggle to trace the Milky Way's outline, but new mapping methods could finally reveal its true face
Read more
STRANGE OBJECTS

Five oddities of our galaxy

V838 Monocerotis and its light echo <i>(Image: NASA, ESA, and The Hubble Heritage Team (AURA/STScI))</i>
From a supermassive black hole to blue stragglers, we round up a quintet of our galaxy's most puzzling objects
Read more
NEIGHBOURS

Andromeda, our sibling rival

A pretty well-adjusted spiral <i>(Image: NASA/Swift/Stefan Immler (GSFC) and Erin Grand (UMCP))</i>
We used to think the Andromeda and the Milky Way were near-twins but it seems one is a golden child and the other an oddball
Read more
COSMIC DUST

Fast-moving clouds defy gravity

We thought the Magellanic clouds were part of our entourage, but they may just be two charismatic space tourists
Read more
DARK MATTER

Disappearing dwarf galaxies

This model of the Milky Way (blue) and orbiting stars (pink) from the Canis Major dwarf galaxy was produced by infrared data obtained by 2MASS (2-micron all-sky survey) in November 2003. The dwarf galaxy is the closest galaxy to the Milky Way, only 42,000 light years from its galactic centre (white, centre). The pink areas around the Milky Way are streams of stars being pulled away from the dwarf galaxy (white dot at lower left of the galactic centre) by the gravitational forces of the Milky Way <i>(Image: R. Ibata, Strasbourg Observatory, ULP/NASA/Science Photo Library)</i>
We know of 26 small galaxies orbiting the Milky Way, but theories of dark matter suggest we should have an army of them. So where are the lost legions?
Read more
STELLAR EXPLOSIONS

Where are all the supernovae?

Victoria's supernova? These are the expanding remains of G1.9+0.3, in an X-ray image from early 2007 (shown in orange) and a radio image from 1985 (in blue). The difference in size between the two images gives clear evidence for expansion, allowing the time since the original supernova explosion to be estimated <i>(Image: X-ray, NASA/CXC/NCSU/S.Reynolds and colleagues; radio, NSF/NRAO/VLA/Cambridge/D. Green and colleagues)</i>
The Milky Way should host about three stellar explosions per century, but in the past millennium and a bit we have seen only five or six. Read more