NGC 6822 Through a Veil of Galactic Cirrus
This image shows a deep view of Barnard’s Galaxy (NGC 6822), an irregular dwarf galaxy that is one of the nearest neighbours to our Milky Way.
This galaxy was discovered by astronomer Edward E. Barnard in 1884 and is located about 1.6 million light years away in the constellation Sagittarius. Despite boasting a meagre 10 million stars, and extending only one tenth the size of our Milky Way, NGC 6822 contains a full menagerie of hot red star forming HII regions, planetary nebulae, bright OB associations and dark clouds.
Oldest Spiral Galaxy in Universe Discovered
Illustration: An artist’s rendering of galaxy BX442, which is 10.7 billion light-years from Earth, and its companion dwarf galaxy. Credit: Dunlap Institute for Astronomy & Astrophysics/Joe Bergeron
Astronomers have discovered the universe’s most ancient spiral galaxy yet, a cosmic structure that dates back roughly 10.7 billion years, a new study reveals.
The galactic find, discovered by researchers using NASA’s Hubble Space Telescope, comes as something of a surprise. Other galaxies from such early epochs are clumpy and irregular, not strikingly symmetrical like the newfound spiral, which broadly resembles our own Milky Way.
“The fact that this galaxy exists is astounding,” study lead author David Law, of the University of Toronto, said in a statement. “Current wisdom holds that such ‘grand-design’ spiral galaxies simply didn’t exist at such an early time in the history of the universe.”
When Galaxies Collide: Beautiful Images of Cosmic Impacts
“As small galaxies merge, they make larger galaxies, and those will then merge to make still larger galaxies, and so on, up to and including the present-day galaxies,” said astronomer Kirk Borne of George Mason University.
Because of the vast distances between them, there’s a low probability that stars within galaxies will actually hit head-on. But gravitational forces can wrest stars from their previous orbits, scrambling the shape of the galaxies involved.
Friction between diffuse gas and dust inside each galaxy raises temperatures, and interstellar material often combines into huge molecular clouds. All this mass in one place triggers prodigious star formation, with stellar birth rates increasing by a hundredfold.
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On the following pages, Wired takes a look at some of the most amazing images ever taken of these cosmic pile-ups.
Mystery Wave in Milky Way Galaxy Suggests Recent Crash
A mysterious wave discovered in the Milky Way suggests our galaxy is still ringing like a bell from a galactic collision, a crash that possibly occured within the last 100 million years, scientists say.
Astronomers discovered that stars north and south of the midplane of the galaxy are distributed differently, suggesting that some recent event perturbed them. The most likely explanation is that a small satellite galaxy or clump of invisible dark matter plowed through the Milky Way, leaving behind the echoes that we see.
“Our part of the Milky Way is ringing like a bell,” Brian Yanny, of the Fermi National Accelerator Laboratory (Fermilab) in Batavia, Ill., said in a statement. “But we have not been able to identify the celestial object that passed through the Milky Way. It could have been one of the small satellite galaxies that move around the center of our galaxy, or an invisible structure such as a dark matter halo.”
Scientists discover that Milky Way was struck some 100 million years ago, still rings like a bell
The celestial object that passed through the Milky Way could have been one of the small satellite galaxies that moves around the center of our galaxy or an invisible structure such as a dark matter halo.— Published: July 2, 2012
M31
Distance: 2.5 million Light Years
M31 has played a pivotal historical role in astronomy. Early observers saw the soft, foggy patch of glowing light as just another spiral nebula but weren’t yet equipped with the knowledge to appreciate its nature.
The true nature of M31 began to became clear in 1923. In that year Edwin Hubble, using the just completed 100 inch telescope at the Mount Wilson observatory, made his monumental discovery of Cepheid Variable stars in M31 and in one stroke forever changed the astronomical paradigm of the universe as we know it.
Appropriately interpreting the cepheid data, Hubble was the first to appreciate the faint nebula in Andromeda as an “island universe”, an immense galaxy in its own right, similar to our Milky Way.
The Orion Deep Field - Adrift 1,500 light-years away in one of the night sky’s most recognizable constellations, the glowing Orion Nebula and the dark Horsehead Nebula are contrasting cosmic vistas. But even fainter filaments of glowing gas are easily traced throughout the region in this stunning composite image that includes exposures filtered to record emission from hydrogen atoms. The view reveals extensive nebulosities associated with the giant Orion Molecular Cloud complex, itself hundreds of light-years across. A magnificent emission region, the Orion Nebula (aka M42) lies at the upper right of the picture. Immediately to its left are a cluster of prominent bluish reflection nebulae sometimes called the Running Man. The Horsehead nebula appears as a dark cloud, a small silhouette notched against the long red glow left of center. Alnitak is the easternmost star in Orion’s belt and the brightest star to the left of the Horsehead. Below Alnitak is the Flame Nebula, with clouds of bright emission and dramatic dark dust lanes. Completing the trio of Orion’s belt stars, bluish Alnilam and Mintaka form a line with Alnitak, extending to the upper left. (via APOD)
‘Starry Night’
