ikenbot:

Brilliant Geminid Meteor Shower Peaks Tonight

ikenbot:

OB Association Stars

OB associations are groups of O and B stars that have dispersed to the extent that their mutual gravity no longer holds them together. Although they may be far apart, stars in an association share a common motion in space because they were formed from the same gas cloud. This allows astronomers to easily determine OB association membership stars.

Class O stars are very hot and extremely luminous, being bluish in color; in fact, most of their output is in the ultraviolet range. These are the rarest of all main-sequence stars. About 1 in 3,000,000 (0.00003%) of the main-sequence stars in the solar neighborhood are Class O stars.] Some of the most massive stars lie within this spectral class. Type-O stars are so hot as to have complicated surroundings which make measurement of their spectra difficult.

Class B stars are very luminous and blue. Their spectra have neutral helium, which are most prominent at the B2 subclass, and moderate hydrogen lines. Ionized metal lines include Mg II and Si II. As O and B stars are so powerful, they only live for a relatively short time, and thus they do not stray far from the area in which they were formed.

ikenbot:

Aurora Australis Between the Ocean & Star trails

Southern lights or the Aurora Australis above the ocean and under the trails of stars, as photographed from Mornington Peninsula, not far from Melbourne, Australia. — Alex Cherney

ikenbot:

Messier 20 - The Trifid Nebula

ikenbot:

Golden Tree Star Trails

A clear winter night in the valley of Alamut in northern Iran. Far from major cities the sky above this historic valley has kept its natural darkness and beauties.

inothernews:

Except for the rings of Saturn, the Ring Nebula (M57) is probably the most famous celestial band. Its classic appearance is understood to be due to perspective - our view from planet Earth looks down the center of a roughly barrel-shaped cloud of glowing gas. But expansive looping structures are seen to extend far beyond the Ring Nebula’s familiar central regions in this intriguing composite of ground based and Hubble Space Telescope images with narrowband image data from Subaru. Of course, in this well-studied example of a planetary nebula, the glowing material does not come from planets. Instead, the gaseous shroud represents outer layers expelled from the dying, once sun-like star at the nebula’s center. Intense ultraviolet light from the hot central star ionizes atoms in the gas. Ionized oxygen atoms produce the characteristic greenish glow and ionized hydrogen the prominent red emission. The central ring of the Ring Nebula is about one light-year across and 2,000 light-years away.  (Photo and caption via NASA APOD)

the-star-stuff:

Spectacular Wide-Field View of Eagle Nebula in High-Res

The fascinating Eagle Nebula is a dust filled stellar nursery filled with dust and lit up by bright infant stars. This image, captured by the MPG/ESO 2.2-meter Telescope at La Silla, Chile, is one of the widest high-resolution shots of the nebula ever taken.

thescienceofreality:

Heavy Elements Key for Planet Formation, Study Suggests

19 April 2012 

“Planets form more commonly in star systems with relatively high concentrations of elements heavier than hydrogen and helium, a new study suggests.

Such heavier elements are necessary to form the dust grains and planetesimals that build planetary cores, according to the study, which was carried out by researchers Jarrett Johnson and Hui Li of Los Alamos National Laboratory in New Mexico.

Additionally, evidence suggests that the disks of dust that surround young stars don’t survive as long when the stars have lower concentrations of heavy elements, or lower “metallicities” in astronomers’ jargon. The most likely reason for this shorter lifespan is that light from the star causes clouds of dust to evaporate.

“Our calculation is an estimate of the minimum amount of heavy elements that must be present in circumstellar disks before planets can form,” Johnson said. “Because these heavy elements must be produced by the first stars in the universe, the first planets could only form around later generations of stars.”

Understanding how the first planets formed provides crucial information about the early universe. Additionally, a better understanding of early planetary formation impacts many facets of astronomy, including the search for life elsewhere, researchers say.”

Continue.

ikenbot:

Has Our Galaxy’s Dark Matter Gone Missing?

If a new study is true, then the search for dark matter just got a lot weirder. Our little corner of the Milky Way contains no observable concentration of the mysterious stuff whose gravity binds the galaxy, claims one team of astronomers.

That finding would present a major problem for models of how galaxies form and may undermine the whole notion of dark matter, the researchers claim. But some scientists doubt the reliability of the team’s method for measuring the elusive substance.

“This is not just some piddling little detail,” says Frederic Hessman, an astronomer at the University of Göttingen in Germany who was not involved in the work. “If this is right, it turns everything totally upside-down.” But that’s a big if, says Julio Navarro, an astrophysicist at the University of Victoria in Canada: “The argument is provocative, but it remains inconclusive, in my opinion.”

According to standard cosmology, we should be swimming in dark matter. Measurements of the afterglow of the big bang—the so-called cosmic microwave background—and of the distribution of the galaxies suggest that 85% of all matter in the universe is dark matter. What’s more, decades of astronomical observations show that the stars within galaxies swirl about faster than they could if only the gravity of the others stars were holding them in. In fact, the speed with which the sun goes around the center of our galaxy suggests that dark matter ought to be about as abundant as ordinary matter at our distance from the galactic center, about 27,000 light-years.

But that’s not what Christian Moni Bidin, an astronomer at the University of Concepción in Chile, and colleagues find. Using data gathered with several telescopes, they studied old stars called red giants in a cylindrical region a couple of light-years wide and extending 13,000 light-years above the plane of the galaxy.

Treating the stars a bit like atoms in a gas, researchers assumed that they were trapped in the gravitational “well” of the galaxy. So by studying distributions of the stars’ speeds in three dimensions, they could deduce the well’s shape and hence the total distribution of mass from both dark and ordinary matter along the cylinder. Subtracting the distribution of ordinary matter as determined from star counts would then reveal the distribution of dark matter.

Continue..

quantumaniac:

The Case of the Missing Dark Matter

A survey of the galactic region around our solar system by the European Southern Observatory (ESO) has turned up a surprising lack of dark matter, making its alleged existence even more of a mystery.

Dark matter is an invisible substance that is suspected to exist in large quantity around galaxies, lending mass but emitting no radiation. The only evidence for it comes from its gravitational effect on the material around it… up to now, dark matter itself has not been directly detected. Regardless, it has been estimated to make up 80% of all the mass in the Universe.

A team of astronomers at ESO’s La Silla Observatory in Chile has mapped the region around over 400 stars near the Sun, some of which were over 13,000 light-years distant. What they found was a quantity of material that coincided with what was observable: stars, gas, and dust… but no dark matter.

“The amount of mass that we derive matches very well with what we see — stars, dust and gas — in the region around the Sun,” said team leader Christian Moni Bidin of the Universidad de Concepción in Chile. “But this leaves no room for the extra material — dark matter — that we were expecting. Our calculations show that it should have shown up very clearly in our measurements. But it was just not there!”

Based on the team’s results, the dark matter halos thought to envelop galaxies would have to have “unusual” shapes — making their actual existence highly improbable.

Still, something is causing matter and radiation in the Universe to behave in a way that belies its visible mass. If it’s not dark matter, then what is it?

“Despite the new results, the Milky Way certainly rotates much faster than the visible matter alone can account for,” Bidin said. “So, if dark matter is not present where we expected it, a new solution for the missing mass problem must be found.

“Our results contradict the currently accepted models. The mystery of dark matter has just became even more mysterious.”

expose-the-light:

We officially have no idea what causes ultra-powerful cosmic rays

Cosmic rays generate the most energetic particles in the universe, utterly dwarfing anything we can generate in particle accelerators. Astrophysicists thought these cosmic rays were created in powerful gamma-ray bursts. Turns out they were completely, utterly wrong. So now what?

(via expose-the-light)

ikenbot:

Moonrise at Temple of Poseidon

by Chris Kotsiopoulos

A last quarter moonrise as seen from the temple of Poseidon at Sounion, Greece.

GUYS!

It’s

Actually

That

Big

!!!