Tag: Milky way

Puzzling Cosmic Glow Is Caused by Diamond Dust Glamming Up Stars

Diamond dust is responsible for a mysterious glow emanating from certain regions of the Milky Way galaxy, a new study reports.

Astronomers have long known that some type of very small, rapidly spinning particle is throwing off this faint light, which is known as anomalous microwave emission (AME). But they couldn’t identify the exact culprit — until now.

In the new study, researchers used the Green Bank Telescope in West Virginia and the Australia Telescope Compact Array to search for AME light in 14 newborn star systems across the Milky Way.

They spotted the emissions in three of these systems, coming from the planet-forming disks of dust and gas swirling around the stars.

This is the first clear detection of anomalous microwave emission coming from protoplanetary disks,” study co-author David Frayer, an astronomer with the Green Bank Observatory, said in a statement.




The study team also detected the unique infrared-light signatures of nanodiamonds — carbon crystals far smaller than a grain of sand — in these same three systems, and nowhere else.

In fact, these [signatures] are so rare, no other young stars have the confirmed infrared imprint,” study lead author Jane Greaves, an astronomer at Cardiff University in Wales, said in the same statement.

The researchers don’t think this is a coincidence.

One to 2 percent of the total carbon in these protoplanetary disks has been incorporated into nanodiamonds, according to the team’s estimates.

Another leading AME-source candidate, a family of organic molecules known as polycyclic aromatic hydrocarbons (PAHs), doesn’t hold up under scrutiny, the researchers said.

The infrared signature of PAHs has been identified in multiple young star systems that lack an AME glow, they noted.

The new results could help astronomers better understand the universe’s early days, study team members said.

Scientists think the universe expanded far faster than the speed of light shortly after the Big Bang, in a brief period of “cosmic inflation.

If this did indeed happen, it should have left a potentially detectable imprint — an odd polarization of the cosmic microwave background, the ancient light left over from the Big Bang.

The new study provides “good news for those who study polarization of the cosmic microwave background, since the signal from spinning nanodiamonds would be weakly polarized at best,” said co-author Brian Mason, an astronomer at the National Radio Astronomy Observatory in Charlottesville, Virgina.

This means that astronomers can now make better models of the foreground microwave light from our galaxy, which must be removed to study the distant afterglow of the Big Bang,” Mason added.

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Pass it on: Popular Science

 

From Pancakes To Soccer Balls, New Study Shows How Galaxies Change Shape As They Age

A selection of SAMI galaxies imaged with the Hyper Suprime Cam on the Subaru Telescope in Hawaii. National Astronomical Observatory of Japan (NAOJ), Caroline Foster (The University of Sydney) and Dan Taranu (University of Western Australia)

Galaxies are a fundamental part of the 13.7 billion-year-old universe. Understanding how a system as complex and striking as our own Milky Way galaxy formed after the Big Bang is one of the great themes of modern astronomy.

Our research, published today in Nature Astronomy, has identified a surprising connection between the age of a galaxy and its three-dimensional shape.

As galaxies get older they get rounder, and fall victim to the middle-aged spread that catches many of us humans here on Earth.

We’ve known for a long time that shape and age are linked in very extreme galaxies – that is, very flat ones and very round ones.

But this is the first time we have shown this is true for all kinds of galaxies – all shapes, all ages, all masses.




Unveiling the true face of a galaxy

In this study we calculated both the age and shape of galaxies using different techniques.

Assigning an age to a galaxy is tricky. They don’t have a single birth date for when they suddenly popped into existence.

We assessed the average age of the stars in a galaxy as a measure of the galaxy’s age. Young galaxies have a large fraction of recently formed hot blue stars, whereas old galaxies mostly contain colder red stars formed shortly after the Big Bang.

Spectroscopy — splitting the light from a galaxy into many different colours — allows us to measure the average age of stars in a galaxy.

This technique gives a much higher precision than simply using blue or red images as is typically done.

To measure a galaxy’s true three-dimensional shape and ellipticity, you have to measure how its stars move around.

Ellipticity is simply a measure of how squashed a galaxy is with respect to a perfect sphere. An ellipticity of zero means a galaxy is a perfect sphere like a soccer ball.

But as the measured ellipticity increases from zero towards one, the galaxy becomes more and more squashed – from a roundish pumpkin shape to a thin disk like a pancake.

We see galaxies as two-dimensional images projected onto the sky, but that doesn’t tell us what they really look like in three dimensions.

If we can also measure how the stars in a galaxy are moving we can infer their true, three-dimensional shape.

Spectroscopy lets us do this via the Doppler effect. We can measure shifts in the wavelength of light emitted by stars, which depend on whether those stars are moving towards us or away from us, and so measure their motions.

We did this using SAMI, the Sydney-Australian-Astronomical-Observatory Multi-object Integral-Field Spectrograph, on the 3.9-metre Anglo-Australian Telescope at Siding Spring Observatory.

The SAMI instrument provides 13 optical fibre units that can “dissect” galaxies using spectroscopy, providing unique 3D data.

Over the past couple of years, the SAMI Galaxy Survey team has gathered 3D measurements for more than a thousand galaxies of all kinds, and with a hundred-fold range in mass.

Closer to home

If we look at our own Milky Way galaxy, which is more than 10 billion years old, we can see examples of this story.

The youngest part of the Milky Way, where stars are still being formed, is the thin disk, which has a very squashed, pancake-like shape.

The Milky Way also contains rounder and older components, a thick disk and a bulge, but their origin is still mostly unknown.

We know that eventually the Milky Way will merge with our galactic neighbour, the Andromeda galaxy. Predictions are that this will result in a very round, very old giant elliptical galaxy.

So, by studying the processes that shape other nearby galaxies, we can learn a lot about the past, and the fate of our own.

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Pass it on: Popular Science

Mysterious Radio Signals May Come From A Death Star Lurking Near A Supermassive Black Hole

After five years, scientists might have figured out what’s going on with blasts of mysterious radio waves coming from outside the Milky Way: they’re coming from a zombie star in an extreme environment.

In a new study, astronomers suggest this might explain these bizarre intergalactic radio waves, known as fast radio bursts. And it may be the best explanation we have yet for what’s causing them.

Fast radio bursts, or FRBs, have been one of the biggest enigmas for astronomers since 2007. These intense blasts of radio waves come from beyond our galaxy, lasting for only milliseconds at a time.

No one knows exactly what’s causing them, and studying them is incredibly difficult since they’re so brief.




It’s thought that one FRB is being produced in the Universe every second, but only 20 have been detected from Earth over the last decade.

Fortunately, one of those FRBs, called FRB 121102, is different from the rest: it’s the only one known to repeat. After it was found in 2012, astronomers have been able to observe this event as it burps up waves over and over again.

And they found that the waves coming from this FRB are actually twisted — a sign that they’ve passed through some highly magnetized material before reaching our planet.

A good place to find material like that? The nucleus of a galaxy.

If you think about the type of regions that have properties like this in our galaxy, the only region is around the center of the galaxy where there’s a supermassive black hole,” Jason Hessels, an astronomer at the University of Amsterdam and lead author of a Nature study on this discovery said.

Of course, there are other ways to pass through some other highly magnetized material, and Hessels and his team are open to others’ interpretations.

Figuring out what the environment is like around the place where this FRB originated will get scientists closer to understanding what these radio waves are in the first place.

Scientists have floated a number of ideas for what might be causing FRBs. Perhaps these waves are produced during cataclysmic events, like when two dense black holes slam into one another.

Or perhaps they’re caused when something collapses into a black hole and gets ripped apart.

But these scenarios don’t quite explain FRB 121102; whatever is producing the waves can’t be destroyed. “If the source is repeating it needs to continue producing such bursts,” says Hessels.

That’s why astronomers think the waves from FRB 121102 might be coming from a stellar corpse known as a neutron star — the dense leftover core of star after it’s collapsed.

Special kinds of neutron stars can periodically send out flashes of radiation, which may explain the repeating waves.

But the waves we’ve seen from FRB 121102 are incredibly bright and more powerful than a neutron star could produce from so far away.

Astronomers think the waves are coming from a galaxy 3 billion light-years away, which means they have to be super intense to fit what we’ve seen.

To learn more about the source, Hessels and his team used the Arecibo Observatory in Puerto Rico and the Green Bank Telescope in West Virginia to observe the radio blasts coming from this galaxy, ultimately measuring 16 bursts in 2016 and 2017.

When analyzing their data, they found a distortion in the radio waves. Normally, a natural burst of radio waves will have wavelengths moving in multiple directions.

But the waves coming from FRB 121102 all seemed to move in one similar direction, an effect known as polarization.

It’s like how sunglasses reduce glare from reflections off the snow. They’re only sensitive to a certain direction of light,” says Hessels. “And this light has a preferred direction.

Hopefully, more and more FRBs will be discovered in the years ahead to help scientists unravel the mystery. Powerful new radio telescopes are about to come online, which should be able to pick up FRBs more frequently.

And as we find more of these radio bursts, we might be able to learn more about them — especially if we find another one that repeats.

We expect to find many dozens, if not hundreds, of these sources over the next few years,” says Hessels. “And it may not be long before we find the next repeating source.

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Could Our Milky Way’s Many Brown And White Dwarf Stars Be Home To Alien Life?

The dead and failed stars known as white dwarfs and brown dwarfs can give off heat that can warm up worlds, but their cooling natures and harsh light make them unlikely to host life, researchers say.

Stars generally burn hydrogen to give off light and heat up nearby worlds.

However, there are other bodies in space that can shine light as well, such as the failed stars known as brown dwarfs and the dead stars known as white dwarfs.

White dwarfs are remnants of normal stars that have burned all the hydrogen in their cores. Still, they can remain hot enough to warm nearby planets for billions of years.

Planets around white dwarfs might include the rocky cores of worlds that were in orbit before the star that became the white dwarf perished; new planets might also emerge from envelopes of gas and dust around white dwarfs.

Brown dwarfs are gaseous bodies that are larger than the heaviest planets but smaller than the lightest stars.




This means they are too low in mass for their cores to squeeze hydrogen with enough pressure to support nuclear fusion like regular stars.

Still, the gravitational energy from their contractions does get converted to heat, meaning they can warm their surroundings.

NASA’s WISE spacecraft and other telescopes have recently discovered hundreds of brown dwarfs, raising the possibility of detecting exoplanets circling them; scientists have already observed protoplanetary disks around a few of them.

White dwarfs and brown dwarfs are bright enough to support habitable zones — regions around them warm enough for planets to sustain liquid water on their surfaces.

As such, worlds orbiting them might be able support alien life as we know it, as there is life virtually everywhere there is water on Earth.

An added benefit of looking for exoplanets around these dwarfs is that they might be easier to detect than ones around regular stars.

These dwarfs are relatively small and faint, meaning any worlds that pass in front of them would dim them more noticeably than planets crossing in front of normal stars.

However, unlike regular stars, white dwarfs and brown dwarfs cool as they age, meaning their habitable zones will move inward over time.

The most obvious peril of a shifting habitable zone is that it could result in a planet getting so cold all the liquid water on its surface freezes solid.

There are other dangers, however — as white dwarfs and brown dwarfs cool, the light they give off would change as well, possibly meaning they would end up sterilizing worlds with dangerous, high-energy radiation.

To be specific, extreme ultraviolet rays would break a planet’s water apart into hydrogen and oxygen. The hydrogen can escape into space, and without hydrogen to bond with oxygen, the world has no water and is not habitable.

Such exoplanets would resemble Venus, with dry atmospheres dominated by carbon dioxide.

In addition, because white dwarfs and brown dwarfs are so dim, their habitable zones already start off very near them.

About one-hundredth the distance between the sun and Earth, which is about one-thirtieth the distance between the sun and Mercury.

White dwarfs should tidally heat planets more than brown dwarfs, since white dwarfs are so massive, the researchers noted.

White dwarfs are only about the size of the Earth, but they are remarkably dense, with masses nearly two-thirds that of the sun.

All in all, the scientists found it unlikely that planets orbiting white dwarfs would ever be truly habitable.

When they are young, white dwarfs would blast planets in their habitable zones with ultraviolet rays that would strip the worlds of water.

When they grow older, their habitable zones would shift closer to them, and the amount of tidal heating might also end up desiccating any planets residing in those zones.

Although the chances for life around white dwarfs and brown dwarfs might look slim, they are not zero, the scientists cautioned.

For instance, a planet might drift into the habitable zone of a white dwarf from a more distant orbit long after the formation of that dead star.

It would still have to contend with tidal heating, but it would have avoided radiation that likely would have sterilized its surface.

More research is needed to understand how planets orbiting white dwarfs and brown dwarfs form, and “particularly the amount of water they form with,” Barnes said,  a planetary scientist and astrobiologist at the University of Washington at Seattle

We also need to understand how the high-energy radiation of brown dwarfs evolves with time. This is the energy that can remove water, but we don’t have any idea how strong it can be, and how long it lasts.”

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Pass it on: New Scientist

Twins! Distant Galaxy Looks Like Our Own Milky Way

Almost like a postcard from across the universe, astronomers have photographed a spiral galaxy that could be a twin of our own Milky Way.

The distant galaxy, called NGC 6744, was imaged by the Wide Field Imager on the MPG/ESO 2.2-metre telescope at the European Southern Observatory’s La Silla Observatory in Chile.

The pinwheel lies 30 million light-years away in the southern constellation of Pavo (The Peacock).

We are lucky to have a bird’s-eye view of the spiral galaxybecause of its orientation, face-on, as seen from Earth. It’s a dead ringer for our own home in the cosmos, scientists say.




If we had the technology to escape the Milky Way and could look down on it from intergalactic space, this view is close to the one we would see — striking spiral arms wrapping around a dense, elongated nucleus and a dusty disc,” according to an ESO statement.

There is even a distorted companion galaxy — NGC 6744A, seen here as a smudge to the lower right of NGC 6744, which is reminiscent of one of the Milky Way’s neighboring Magellanic Clouds.

The main difference between NGC 6744 and the Milky Way is the two galaxies’ size. While our galaxy is roughly 100,000 light-years across, our “twin” galaxy extends to almost twice that diameter, researchers said.

The photogenic object is one of the largest and nearest spiral galaxies to Earth.

It’s about as bright as 60 billion suns, and its light spreads across a large area in the sky about two-thirds the width of the full moon making the galaxy visible as a hazy glow through a small telescope.

The reddish spots along the spiral arms in NGC 6744 represent regions where new stars are being born.

The picture was created by combining four exposures taken through different filters that collected blue, yellow-green and red light and the glow coming from hydrogen gas.

These are shown in the new picture as blue, green, orange and red, respectively.

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Newly Forming Stars Have Been Located By Astronomers On The Side Of The Milky Way

For the first time ever, astronomers have pinpointed the location of a luminous light source on the opposite side of the Milky Way Galaxy, far beyond the galactic center.

The source — a region of space where massive stars are being born — is located in a distant spiral arm, one of the large tentacles of gas that swirl around the middle of our galaxy.

Knowing its location has allowed astronomers to trace the arm as it wraps around the center of the Milky Way, telling us more about the structure of the galaxy we live in.

It’s a significant discovery, since locating distant objects in our galaxy is an incredibly difficult process. The Milky Way is filled with interstellar dust that makes it nearly impossible to see any visible light coming from faraway sources.

And our galaxy is incredibly big, stretching 100,000 light-years across. That means it takes a thousand centuries for light to cross from one end of the Milky Way to the other.




Any radio waves coming from remote locations across the galaxy weaken considerably as they cross the vast distances on the way to Earth.

That’s why astronomers use special measurement techniques to figure out where things are in our galaxy.

To find this specific star-forming region, scientists leveraged the Earth’s orbit around the Sun, observing the source’s radio waves from different vantage points as the Earth travels through the Solar System.

Such a technique can help astronomers accurately measure the distance of a far-off object — it’s been used to do so many times before — but a galactic object this far away has never been measured before.

This is certainly the first source we’ve ever measured a distance that far by a factor of two,” Mark Reid, a senior radio astronomer at Harvard and author of a study in Science detailing this discovery said.

So it’s twice as far away as the previous record holder.”

For their mapping campaign, the astronomers have relied on a telescope known as the Very Long Baseline Array, run by the National Radio Astronomy Observatory.

The array consists of 10 big radio telescopes located across parts of the Northern Hemisphere, from Hawaii to New England.The team has been using these telescopes to pick up emissions of water vapor and methanol from distant sources.

The team has been using these telescopes to pick up emissions of water vapor and methanol from distant sources. Regions where stars form create a lot of these gases, which give off incredibly strong radio waves that we can observe from Earth.

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Scientists Catch A White Dwarf Star In The Act Of Exploding Into A Nova

It’s not every day you get to see a star go nova. Scientists at Warsaw University Observatory in Poland have managed to catch a binary star system both before and after its explosive flash.

The findings, described in the journal Nature, confirm a long-held theory about novae known as the hibernation hypothesis – and could potentially help scientists better understand when such stellar outbursts occur.

Novae are typically caused by a gravitationally locked pair of stars, called a binary system, consisting of one white dwarf and a companion star.




A white dwarf is an aging star that has already shed much of its mass, leaving behind a small but massive core.

Like a gravitational vampire, the white dwarf siphons off material from its stellar companion – and every so often, the system becomes so unstable that the white dwarf erupts, producing a cataclysmic explosion that causes it to flare brightly in the night sky.

The most spectacular eruptions, with a ten-thousandfold increase in brightness, occur in classical novae and are caused by a thermonuclear runaway on the surface of the white dwarf,” the study authors wrote.

Such eruptions are thought to recur on time scales of ten thousand to a million years.”

Such explosions might actually have seeded the universe with some elements and radioactive isotopes, such as lithium, said lead author Przemek Mroz, an astronomer at the observatory.

About 50 novae go off every year in the Milky Way, but only five to 10 are actually observed because most of them are shrouded by interstellar gas and dust, Mroz said in an email.

The closest and brightest, however, can potentially be picked out with the naked eye.

But though novae can be seen once they go off, scientists don’t often get the chance to study them in depth before they explode.

Researchers have long had a theory about the cycle that causes these novae: When the mass transfer is low, the accretion grows unstable; every so often, the white dwarf experiences what the authors called “dwarf nova outbursts.”

Dwarf nova outbursts occur when material from the accretion disk is dumped onto the star’s surface, Mroz said; the dramatic classical nova event occurs on the surface of the white dwarf when there is enough gas to ignite thermonuclear reactions.

This is the first time [that] we observed a dwarf nova that transformed into a classical nova,” Mroz said of his team’s findings.

When the classical nova explosion finally occurs, it actually boosts the mass-transfer rate for centuries, keeping the system more stable until it dwindles and begins to approach the “hibernation” period, thus repeating the process.

But scientists couldn’t say what was really happening until the nova V1213 Cen flashed in 2009 and was caught by the university’s Optical Gravitational Lensing Experiment.

“This discovery would be impossible without long-term observations by the OGLE survey,” Mroz wrote in an email.

The survey started almost 25 years ago and for 20 years we have had a dedicated 1.3-meter telescope at Las Campanas Observatory in Chile. This is another case when OGLE data are crucial for studying unique, extremely rare phenomena.

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Astronomers Discover The Biggest Object in The Universe So Far

universe

Astronomers have recently announced the discovery of the BOSS Great Wall, a group of superclusters that span roughly 1 billion light-years across and represents the largest structure ever found in space.

The BOSS Great Wall, which sounds aptly named for its size but actually stands for the Baryon Oscillation Spectroscopic Survey, is a string of superclusters connected by gases lying roughly 4.5 to 6.5 billion light-years away from Earth.




Thanks to gravity, these superclusters stay connected and swirl together through the void of space. The megastructure discovered by a team from the Canary Islands Institute of Astrophysics is composed of 830 separate galaxies and has a mass 10,000 times greater than the Milky Way.

To put the scale of this structure into perspective, we orbit one single star, the Sun. Our galaxy, the Milky Way, has over 200 billion stars, just like our Sun, in it alone with an unknown amount of planets orbiting them.

galaxy

Now, multiply that insane thought by 10,000 and you have the BOSS Great Wall. To our limited scope, it is effectively infinite.

However, not everyone agrees that the super structure should even be considered a structure at all. The argument is that these superclusters are not actually connected.

galaxy

Instead, they have dips and gaps between them that are sort of linked by clouds of gas and dust. This loose connection causes a debate every time ‘great wall-like’ structures are found.

In the end, the arguments seem to boil down to personal definitions of what constitutes a single structure with most researchers agreeing that they are one.

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