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THE Milky Way's neighbourhood may be teeming with invisible galaxies, one of which appears to be crashing into our own.
In 2008, a cloud of hydrogen with a mass then estimated at about 1 million suns was found to be colliding with our galaxy. Now it appears the object is massive enough to be a galaxy itself.
Called Smith's cloud, it has managed to avoid disintegrating during its smash-up with our own, much bigger galaxy. What's more, its trajectory suggests it punched through the disc of our galaxy once before, about 70 million years ago.
To have survived, it must contain much more
Originally posted by rattan1
did we have any mass extinction 70M years ago??????
Cretaceous–Tertiary extinction event (K-T extinction) - 65 Ma at the Cretaceous-Paleogene transition about 17% of all families and 50% of all genera went extinct. (75% species). It ended the reign of dinosaurs and opened the way for mammals and birds to become the dominant land vertebrates. In the seas it reduced the percentage of sessile animals to about 33%. The K-T extinction was rather uneven — some groups of organisms became extinct, some suffered heavy losses and some appear to have been only minimally affected.
A dark galaxy is a galaxy-sized object containing very few or no stars (hence 'dark'). Held together by dark matter, it may also contain gas and dust. No dark galaxy with a black hole as a center has yet been discovered.
Radio astronomers may have found the first ever galaxy that is made almost entirely of dark matter. The "dark galaxy", which lies in the Virgo cluster about 50 million light years away, rotates in the same way as an ordinary galaxy but does not contain any stars (R Minchin et al. 2005 Astrophys. J. 622 L21-L24).
Dark matter was originally proposed to explain why galaxies rotate much faster than can be explained by the amount of visible matter they contain. This mysterious form of matter does not emit or absorb electromagnetic radiation -- hence the name "dark" -- and can only be detected by its gravitational influence on ordinary matter. Overall the universe is thought to contain about 5% of ordinary matter, 25% of dark matter and 70% of dark energy. Although various types of new particle have been proposed to explain the dark matter, the nature of the dark energy remains a complete mystery.
Strong evidence for a massive galaxy totally devoid of stars has been found in the Virgo cluster, about 50 million light years away from Earth. If the existence of this "dark galaxy" is confirmed, it will vindicate the favoured theory of how galaxies form - and will present fresh puzzles to solve.
The new galaxy, which consists of a gigantic cloud of hydrogen gas and exotic dark matter, contains enough material to give birth to tens of millions of stars. Yet something is preventing this from happening. Such dark galaxies have been predicted, and could outnumber normal galaxies by as much as a hundred to one, but this is the first time anyone has confidently claimed to have seen one
n 2008, a cloud of hydrogen with a mass then estimated at about 1 million suns was found to be colliding with our galaxy. Now it appears the object is massive enough to be a galaxy itself.
Dark matter makes up about 23 percent of the universe's mass-energy budget. Normal matter, the stuff of stars, planets and people, contributes just 4 percent. The rest of the universe is driven by an even more mysterious thing called dark energy.
Originally posted by space cadet
reply to post by rattan1
Nice find! I wish the article was more explainitory, you know, for those like myself who don't understand why we can't just look up and see this happening, but, nonetheless, I enjoy knowing.
In the early universe, neutrinos would have been packed relatively tightly. Nowadays they are farther apart and so each has greater mass, the new theory suggests. As they move apart, a tension develops between them, like that in a stretched rubber band, said Ann Nelson, a physics professor at the University of Washington.
The increasing tension is the infamous dark energy, explained Neal Weiner, a physicist at the university and another member of the study team.
the gravitational effects of the encounter are enough to twist and distort galaxies beyond recognition
Originally posted by Happyfeet
Could this be what wiped out previous civilizations that made the pyramids and such. The old civilizations must have left clues.
Prior to this work, it was thought that dark matter forms in roughly spherical lumps called ‘halos’, one of which envelopes the Milky Way. But this ‘standard’ theory is based on supercomputer simulations that model the gravitational influence of the dark matter alone. The new work includes the gravitational influence of the stars and gas that also make up our Galaxy.
Stars and gas are thought to have settled into disks very early on in the life of the Universe and this affected how smaller dark matter halos formed. The team’s results suggest that most lumps of dark matter in our locality merged to form a halo around the Milky Way. But the largest lumps were preferentially dragged towards the galactic disk and were then torn apart, creating a disk of dark matter within the Galaxy.
April 2009: On April 6th, a strong eartquake hit the Abruzzo region where the XENON100 detector is located in the LNGS underground lab, causing the death of several hundred people and dramatic damages to many buildings.
However, we were lucky and no XENON member suffered serious injury. The detector is also fine and we are able to operate it almost as normal.