Saturday, 14 July 2012

Astrophysics stuff from the week 9-15/7/12

'Dark galaxies of the early Universe spotted for the first time'
Cosmological theory comes up trumps again! Dark and dusty galaxies of the early universe were predicted by theory, and have now been observed.
Astronomers think that these, dusty, dark galaxies were 'feeder' galaxies for the later ones that produced the bright stars, of which our Sun is typical.
But, because they are dark, the old galaxies are difficult to detect. And this is where quasars come in.
The VLT (Very Large Telescope) was used to detect the faint glow of the dusty galaxies, illuminated by the ultraviolet radiation of a nearby quasar.
"The light from the quasar makes the dark galaxies light up in a process similar to how white clothes are illuminated by ultraviolet lamps in a night club."
"They used the FORS2 instrument to map a region of the sky around the bright quasar HE 0109-3518, looking for the ultraviolet light that is emitted by hydrogen gas when it is subjected to intense radiation. Because of the expansion of the Universe, this light is actually observed as a shade of violet by the time it reaches the VLT."

About 12 galaxies (pictured) were identified, and were analysed as having around 1 billion times as much gas in them as the Sun, and to have a star formation rate 100 times lower than typical, contemporary galaxies, because of the dust content.

Another investigation into galaxies of the early universe, this time into dwarf galaxies, has presented evidence as to how there are a small number that are darker than would be proportional for their size.
The Hubble Space Telescope was used to analyse 'fossil' galaxies, that have barely changed in 13 billion years. They contain very few stars, and are some of the tiniest, and most pristine in the universe.
Because they're all about the same age, it makes sense to think that the same mechanism stunted their development.
In the first billion years of the cosmic inflation, radiation from the first stars knocked electrons off the early, cool hydrogen, in a process called universal reionisation.
This same radiation extinguished the star-making activities in dwarf galaxies, which did not have the mass to survive, unlike their larger counterparts.
What little gas they had was stripped away as the flood of ultraviolet light rushed through them. Their gas supply depleted, the galaxies could not make new stars.

Pictures taken from the Chandra X-Ray Observatory, over the past couple of years, have identified a shockwave breaking through the cocoon of debris left after a star collapsed in on itself in a supernova event.

Using both ground and space telescopes, the black hole in galaxy PS1-10jh, which is about the same mass as the Milky Way's, has been observed tearing a star apart, and drawing stellar material into its gravitational grasp.
"A flare in ultraviolet and optical light revealed gas falling into the black hole as well as helium-rich gas that was expelled from the system."

Look outside your window, this weekend, and you won't even notice the biggest storm to happen this year - a solar storm.
'Solar storm barreling toward Earth this weekend'
"The storm began Thursday when the sun unleashed a massive flare that hurled a cloud of highly charged particles racing toward Earth at 3 million mph (4.8 million kph). It was the sixth time this year that such a powerful solar outburst has occurred. None of the previous storms caused major problems."
[video] 'The Sun blasts out an X1-Class solar flare'
"Flares are classified according to their strength. The smallest ones are B-class, followed by C, M and X, the largest.
Within each letter class, there is a finer scale from 1 to 9. Although X is the last letter, there are flares more than 10 times the power of an X1, so X-class flares can go higher than 9.
The most powerful flare on record was in 2003, during the last solar maximum. It was so powerful that it overloaded the sensors measuring it. They cut-out at X28."