The Milky Way

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Heres a Galaxy Thread

Does our galaxy have a HALO? Nasa spots massive million light year wide gas cloud around our nearest neighbour - and says the Milky Way might also have one

Scientists using NASA's Hubble Space Telescope have discovered our nearest galaxy is surrounded by an immense 'halo;

The halo of gas enveloping the Andromeda galaxy, our nearest massive galactic neighbour, is six times larger and 1,000 times more massive than previously measured.

The dark, nearly invisible halo stretches about a million light-years from its host galaxy, halfway to our own Milky Way galaxy.

This finding promises to tell astronomers more about the evolution and structure of majestic giant spirals, one of the most common types of galaxies in the universe.
'Halos are the gaseous atmospheres of galaxies,' said lead investigator Nicolas Lehner of the University of Notre Dame, Indiana.
The properties of these gaseous halos control the rate at which stars form in galaxies according to models of galaxy formation,' explained the.
The Andromeda galaxy lies 2.5 million light-years away and looks like a faint spindle, about 6 times the diameter of the full moon. It is considered a near-twin to the Milky Way galaxy.
Because the gas in Andromeda's halo is dark, the team looked at bright background objects through the gas and observed how the light changed.
This is a bit like looking at a glowing light at the bottom of a pool at night, they say.
The ideal background 'lights' for such a study are quasars, which are very distant bright cores of active galaxies powered by black holes.
The team used 18 quasars residing far behind Andromeda to probe how material is distributed well beyond the visible disk of the galaxy.

Their findings were published in the May 4, 2015 edition of the Astrophysical Journal.

Earlier research from Hubble Cosmic Origins Spectrograph (COS)-Halos program studied 44 distant galaxies and found halos like Andromeda's, but never before has such a massive halo been seen in a neighboring galaxy.

Because the previously studied galaxies were much farther away, they appeared much smaller on the sky.

Only one quasar could be detected behind each faraway galaxy, providing only one light anchor point to map their halo size and structure.

With its close proximity to Earth and its correspondingly large footprint on the sky, Andromeda provides a far more extensive sampling of a lot of background quasars.

WHERE DID IT COME FROM?
But where did the giant halo come from? Large-scale simulations of galaxies suggest that the halo formed at the same time as the rest of Andromeda.
The team also determined that it is enriched in elements much heavier than hydrogen and helium, and the only way to get these heavy elements is from exploding stars called supernovae.
As the light from the quasars travels toward Hubble, the halo's gas will absorb some of that light and make the quasar appear a little darker in just a very small wavelength range,' explains co-investigator J. Christopher Howk, also of Notre Dame.
'By measuring the dip in brightness in that range, we can tell how much gas there is between us and that quasar.'
The scientists used Hubble's unique capability to study the ultraviolet light from the quasars. Ultraviolet light is absorbed by Earth's atmosphere, which makes it difficult to observe with a ground-based telescope.
But where did the giant halo come from? Large-scale simulations of galaxies suggest that the halo formed at the same time as the rest of Andromeda.
The team also determined that it is enriched in elements much heavier than hydrogen and helium, and the only way to get these heavy elements is from exploding stars called supernovae.
The supernovae erupt in Andromeda's star-filled disk and violently blow these heavier elements far out into space.
Over Andromeda's lifetime, nearly half of all the heavy elements made by its stars have been expelled far beyond the galaxy's 200,000 light-year diameter stellar disk. Because we live inside the Milky Way, scientists cannot determine whether or not such an equally massive and extended halo exists around our galaxy, the team say.

It's a case of not being able to see the forest for the trees.

If the Milky Way does possess a similarly huge halo, the two galaxies' halos may be nearly touching already and quiescently merging long before the two massive galaxies collide.

Hubble observations indicate that the Andromeda and Milky Way galaxies will merge to form a giant elliptical galaxy beginning about 4 billion years from now.

Millions of missing galaxies found hiding in plain sight

'When our universe was young, there were lots of compact, elliptical-shaped galaxies containing trillions of stars,' explained Swinburne University of Technology's Professor Alister Graham.
'Due to the time it takes for light to travel across the vastness of space, we see these distant galaxies as they were in our young universe.
'However in the present-day universe very few such spheroidal stellar systems have been observed.'

In 2005, astronomers found a strange excess of compact spherical galaxies in the early, distant universe.
The galaxies were about a third the size of similarly shaped ones in our own cosmic neighbourhood 11 billion years ago, but almost extinct today.
The most popular theory had been that over time, galaxy mergers might have led to their destruction and transformation into larger elliptical galaxies.
However there have not been enough galactic collisions to account for the reduction in the number of these compact spheroids.



A closer look at images revealed that 21 galaxies that originally looked like big 3D clouds of stars were flat 2D disc galaxies with bulges at the centre. Pictured is one of the galaxy's involved in the study, NG 5419

'They were hiding in plain sight,' Dr Bililign Dullo, co-author of the research, said. 'The spheroids are cloaked by discs of stars that were likely built from the accumulation of hydrogen gas and smaller galaxies over the intervening eons.' A closer look at images revealed that 21 galaxies that originally looked like big 3D clouds of stars were flat 2D disc galaxies with bulges at the centre.

The number of such hidden systems roughly matches the number of compact massive galaxies in the early universe. 'Unlike the massive dinosaurs that existed when the Earth was much younger, the galactic dinosaurs of our universe are not extinct,' Professor Graham said. 'They are simply embedded in large, relatively thin, discs of stars.'

The findings suggest there are 1,000 times more of these galaxies-within-galaxies in the local universe than previously thought, according to the New Scientist.

Due to the enormity of modern galaxy surveys, it had become common practice to treat individual galaxies as single component entities. But by carefully disentangling each galaxy's components, namely their inner spheroid and outer disc, the researchers uncovered the missing population.

'While the inner component is compact and massive, the full galaxy sizes are not compact,' Ms Giulia Savorgnan, a PhD student involved in the discovery, said.

'This explains why they had been missed; we simply needed to better dissect the galaxies rather than consider them as single objects.'

Professor Graham believes that at least part of our own galaxy's central bulge may once have been one of these compact galaxies.

New Scientist.

Someone elses galaxy......the Sombrero galaxy, Messier 104 (M104).

Powerful new radio telescope array searches the entire sky 24/7

Owens Valley Long Wavelength Array

An aerial view of the array. The array's station consists of 250 low-cost antennas, each about 3ft (1 metre) in size, spread out in the Owens Valley

Every night, our sky pulses with radio light waves, most of which go unseen. A new array of radio antennas in California, called the Owens Valley Long Wavelength Array, is now gearing up to catch some of this action. By scanning the entire sky at once, the array aims to pick up signals from flaring stars, flashing planets and potentially even alien life.

'Our new telescope lets us see the entire sky all at once, and we can image everything instantaneously,' said Gregg Hallinan, an assistant professor of astronomy at the California Institute of Technology in Pasadena.

The array has produced a new video of the radio sky, showing how it flickers and morphs over 24 hours.

One of the key goals of the project is to monitor extrasolar space weather — the interaction between nearby stars and their orbiting planets. Our Sun flares with radiation and hurtles particles and magnetic fields outward. Spectacular light displays, or auroras, are produced on the planets in our Solar System when those particles interact with chemical elements in the planets’ atmospheres. The same is true for stars beyond our Sun, and, if those stars have planets, they too would, in theory, have auroras.

Measurements of these interactions in other star systems could reveal new information about the strength of planets’ magnetic fields — and thus their potential for harbouring life. Magnetic fields were a critical factor in the development of life on Earth, offering protection from dangerous radiation and particles.

The radio antennas, which combine to form a powerful radio telescope, are based at Caltech’s Owens Valley Radio Observatory, near Big Pine, California. Other partners include: NASA’s Jet Propulsion Laboratory, Pasadena, California; Harvard University, Cambridge, Massachusetts; the University of New Mexico, Albuquerque; Virginia Tech, Blacksburg; and the U.S. Naval Research Laboratory, headquartered in Washington.

The array’s station consists of 250 low-cost antennas, each about 3 feet (1 metre) in size, spread out in the Owens Valley. Future plans include thousands of additional antennas; the more antennas in the array, the greater the image sensitivity. The small size of the antennas has benefits as well, leading to a huge field of view in the same way that binoculars can see a large patch of sky. The array covers the entire viewable sky all at once.

“Just as the antenna of your car radio can detect local radio stations no matter where they are around the car, these antennas can detect signals anywhere in the sky,” said Joseph Lazio, an astronomer on the project from JPL.

The Owens Valley Long Wavelength Array might also be able to gather traces of radio light from the very first stars and galaxies.

“The biggest challenge is that this weak radiation from the early universe is obscured by the radio emission from our own Milky Way galaxy, which is about a million times brighter than the signal itself, so you have to have very carefully calibrated data to see it,” said Hallinan. “That’s one of the primary goals of our collaboration — to try to get the first statistical measure of that weak signal from our cosmic dawn.”

Lazio said the array will help in the design of future space missions. Some radio wavelengths are blocked or reflected off Earth’s atmosphere, but in space the whole radio spectrum can be observed.

“Ultimately, we will likely need to construct a similar array of simple antennas and put it in space, or on the Moon,” he said.

http://astronomynow.com/tag/california-institute-of-technology/