Astronomy Now Home
Home Magazine Resources Store

On Sale Now!

The October 2014 issue of Astronomy Now is on sale! Order direct from our store (free 1st class post & to UK addresses). Astronomy Now is the only astronomy magazine specially designed to be read on tablets and phones. Download the app from Google Play Store or the Apple App Store.

Top Stories

Earthshine used to test life detection method
...By imagining the Earth as an exoplanet, scientists observing our planet's reflected light on the Moon with ESO's Very Large Telescope have demonstrated a way to detect life on other worlds...

Solid buckyballs discovered in space
...Astronomers using NASA’s Spitzer Space Telescope have detected a particular type of molecule, given the nickname “buckyball”, in a solid form for the first time...

Steamy water-world gets the Hubble treatment
...Hubble Space Telescope observations of a 7 Earth-mass planet find an unusual water-rich world swathed in a thick, steamy atmosphere...

Fermi finds giant bubbles
in Milky Way

Posted: 11 November 2010

Bookmark and Share

A previously unseen structure spanning across 50,000 light years and possibly millions of years old has been discovered in the heart of our Galaxy.

The structure spans more than half the visible sky from the constellation of Virgo to Grus. Hints of the bubbles' edges were first observed in X-rays (blue) by ROSAT. The gamma rays mapped by Fermi (magenta) extend much farther from the Galaxy's plane. Image: NASA's Goddard Space Flight Center.

Although the source of the bubble is not confirmed, scientists speculate it could be the remnant of an eruption from the supermassive black hole that resides in the centre of our Milky Way Galaxy. “What we see are two gamma-ray-emitting bubbles that extend 25,000 light years north and south of the galactic centre,” describes Doug Finkbeiner of the Harvard-Smithsonian Center for Astrophysics.

Normally, the fog of gamma rays that permeates the sky (resulting from collisions of particles moving at nearly the speed of light with interstellar gas) would prevent detection of the bubble, but thanks to the sensitivity of Fermi's Large Area Telescope (LAT), the team were able to isolate this fog to reveal the giant bubbles.

The gamma-ray structure was uncovered by processing Fermi all-sky data at energies from 1 to 10 billion electron volts. Image: NASA/DOE/Fermi LAT/D. Finkbeiner et al.

The bubble emissions are much more energetic than the gamma-ray fog seen elsewhere in the Milky Way, and appear to have defined edges, suggesting it formed as a result of a large and rapid energy release. One possible culprit includes a particle jet from the supermassive black hole in the Galaxy's centre, a phenomena observed in other galaxies, too. But while there is no evidence for such a jet being active today, the bubble could represent an ancient jet. An alternative theory is that the bubbles were blown out from gas outflow during a burst of star formation, another process also seen in other galaxies.

“Whatever the energy source behind these huge bubbles may be, it is connected to many deep questions in astrophysics,” says David Spergel, a scientist at Princeton University in New Jersey.

The bubbles' presence had already been hinted at by Germany's Roentgen Satellite (ROSAT), which found subtle evidence for bubble 'edges' close to the galactic centre, and NASA's Wilkinson Microwave Anisotropy Probe (WMAP), which detected an excess of radio signals at the locations of the gamma-ray bubbles. The Fermi data provides the clearest picture yet of their presence.

The Planets
From tiny Mercury to distant Neptune and Pluto, The Planets profiles each of the Solar System's members in depth, featuring the latest imagery from space missions. The tallest mountains, the deepest canyons, the strongest winds, raging atmospheric storms, terrain studded with craters and vast worlds of ice are just some of the sights you'll see on this 100-page tour of the planets.

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.

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!


© 2014 Pole Star Publications Ltd.