Tag: Stars

There Might Be More Big Stars In The Universe Than We Thought

A new series of observations suggests that we have underestimated the number of large stars that form in starburst events. If this finding is more than just an exception to the rule, there could be consequences for many astronomical theories.

As reported in Science, an international group of astronomers has studied the stars within 30 Doradus, also known as the Tarantula Nebula, a starburst region in the Large Magellanic Cloud.

The team managed to characterize the properties of 452 stars in 30 Doradus and, out of all of them, 247 were more massive than 15 times our Sun.




There are about 25 to 50 more heavy stars than theoretical predictions, known as the initial mass function (IMF), would expect.

The IMF describes the distribution of masses for any population of stars when it formed. It’s an empirical distribution and is very important. The mass of stars determines their evolution and how they’re going to end their life.

For example, more massive stars mean more supernovae, which leads to more black holes and neutron stars. It also influences the evolution of the stars’ host galaxies as a whole.

And since galaxies have up to 100 billion stars, the IMF is very useful for providing statistics.

Nevertheless, this doesn’t mean that the IMF is perfect. Since its proposal in 1955 by Edwin Salpeter, the IMF has been tweaked to better characterize the low-mass end of star mass distribution.

It turns out that there are a lot more small stars than predicted, and the new study suggests that some tweaking might be necessary for certain environments, even at the high end of mass distribution.

The study raises several questions that will require more observation. Is the excess of massive stars connected to advantageous conditions in the gas clouds?

Is it common during starburst events? Are there other mechanisms at work?

What remains interesting is the presence of some of the most massive stars ever observed, with some weighing over 200 times the mass of the Sun.

The researchers estimate that bigger stars might still exist in the core of the nebular, which was not resolved.

The Tarantula Nebula is the most active and largest (over 600 light-years) starburst region in the local group of galaxies.

Supernova 1987A, the closest supernova observed since the invention of the telescope, occurred on the outskirts of this nebula.

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Pass it on: New Scientist

Sky Watching Tips And Tricks For Cold Northern Nights

For much of the contiguous United States this winter has been marked by perpetual ice, snow as well as the now infamous polar vortex.

Such conditions might make even the most committed stargazer think twice before venturing outdoors.

Stepping outside to enjoy a view of the constellation Orion, Jupiter or even just the waxing moon these frosty nights takes only a minute or two, but if you plan to stay outside longer, remember that enjoying the starry winter sky requires protection against the cold temperatures.




The best garments are a hooded ski parka and ski pants, both of which are lightweight and provide excellent insulation. And remember your feet.

Two pairs of warm socks in loose-fitting shoes are quite adequate; for protracted observing on bitter-cold nights wear insulated boots.

Reach for the binoculars

In weather like this, one quickly will realize the advantage of using a pair of good binoculars over a telescope.

A person who attempts to set even a so-called “portable” scope up in bitter temperatures or blustery winds might give up even before he or she got started.

But binoculars can be hand-held and will produce some quickly magnified images of celestial objects before rushing back inside to escape the frigidity.

Transparency

In their handy observing guide, “The Stars” (Golden Press, N.Y.), authors Herbert Zim and Robert Baker write that “the sky is never clearer than on cold, sparkling winter nights.

“It is at these times that the fainter stars are seen in great profusion. Then the careful observer can pick out dim borderline stars and nebulae that cannot be seen when the sky is less clear.

What Zim and Baker were referring to is sky transparency, which is always at its best during the winter season. That’s because Earth’s atmosphere is not as hazy because it is less moisture laden.

Cold air has less capacity to hold moisture, therefore the air is drier and thus much clearer as opposed to the summer months when the sky appears hazier.

But this clarity can also come at a price.

Seeing through the twinkles

If you step outside on one of those “cold, sparkling nights” you might notice the stars twinkling vibrantly.

This is referred to as scintillation, and to the casual observer looking skyward, they might think of such a backdrop as the perfect night for an astronomer, but it isn’t.

This is because when looking skyward, skywatchers are trying to see the sky through various layers of a turbulent atmosphere.

Were we to train a telescope on a star, or a bright planet like Mars, what we would end up with is a distorted image that either seems to shake or quiver or simply “boils” to the extent that you really can’t see very much in terms of any detail.

Forecasting sky conditions

If you own a telescope, you don’t need to wait for balmy summer nights to get good views. Usually, a few days after a big storm or frontal passage, the center of a dome of high pressure will build in to bring clear skies and less wind.

And while the sky might not seem quite as “crisp” or “pristine” as it was a few days earlier, the calming effect of less winds will afford you a view of less turbulent and clearer images through your telescope.

More comfortable nights ahead

If you plan on heading out on a cold winter’s night — and if you’re doing it while under a dome of high pressure — the fact that there is less wind means not only potentially good seeing, but also more comfort viewing conditions.

The end of winter is in sight though. The Northern Hemisphere is officially halfway through the winter season and milder, more comfortable nights are within reach.

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Pass it on: Popular Science

 

Mysterious Dark Matter May Not Always Have Been Dark

The nature of dark matter is currently one of the greatest mysteries in science. The invisible substance — which is detectable via its gravitational influence on “normal” matter — is thought to make up five-sixths of all matter in the universe.

Astronomers began suspecting the existence of dark matter when they noticed the cosmos seemed to possess more mass than stars could account for.

For example, stars circle the center of the Milky Way so fast that they should overcome the gravitational pull of the galaxy’s core and zoom into the intergalactic void.

Most scientists think dark matter provides the gravity that helps hold these stars back.




Scientists have mostly ruled out all known ordinary materials as candidates for dark matter. The consensus so far is that this missing mass is made up of new species of particles that interact only very weakly with ordinary matter.

One potential clue about the nature of dark matte rhas to do with the fact that it’s five times more abundant than normal matter, researchers said.

This may seem a lot, and it is, but if dark and ordinary matter were generated in a completely independent way, then this number is puzzling,” said study co-author Pavlos Vranas, a particle physicist at Lawrence Livermore National Laboratory in Livermore, California.

Instead of five, it could have been a million or a billion. Why five?

The researchers suggest a possible solution to this puzzle: Dark matter particles once interacted often with normal matter, even though they barely do so now.

The protons and neutrons making up atomic nuclei are themselves each made up of a trio of particles known as quarks.

The researchers suggest dark matter is also made of a composite “stealth” particle, which is composed of a quartet of component particles and is difficult to detect.

The scientists’ supercomputer simulations suggest these composite particles may have masses ranging up to more than 200 billion electron-volts, which is about 213 times a proton’s mass.

Quarks each possess fractional electrical charges of positive or negative one-third or two-thirds. In protons, these add up to a positive charge, while in neutrons, the result is a neutral charge.

Quarks are confined within protons and neutrons by the so-called “strong interaction.

The researchers suggest that the component particles making up stealth dark matter particles each have a fractional charge of positive or negative one-half, held together by a “dark form” of the strong interaction.

Stealth dark matter particles themselves would only have a neutral charge, leading them to interact very weakly at best with ordinary matter, light, electric fields and magnetic fields.

The researchers suggest that at the extremely high temperatures seen in the newborn universe, the electrically charged components of stealth dark matter particles could have interacted with ordinary matter.

However, once the universe cooled, a new, powerful and as yet unknown force might have bound these component particles together tightly to form electrically neutral composites.

Stealth dark matter particles should be stable — not decaying over eons, if at all, much like protons.

However, the researchers suggest the components making up stealth dark matter particles can form different unstable composites that decay shortly after their creation.

These unstable particles might have masses of about 100 billion electron-volts or more, and could be created by particle accelerators such as the Large Hadron Collider (LHC) beneath the France-Switzerland border. They could also have an electric charge and be visible to particle detectors, Vranas said.

Experiments at the LHC, or sensors designed to spot rare instances of dark matter colliding with ordinary matter, “may soon find evidence of, or rule out, this new stealth dark matter theory,” Vranas said in a statement.

If stealth dark matter exists, future research can investigate whether there are any effects it might have on the cosmos.

The scientists, the Lattice Strong Dynamics Collaboration, will detail their findings in an upcoming issue of the journal Physical Review Letters.

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First Earth-Size Planet That Could Support Life Found

For the first time, scientists have discovered an Earth-size alien planet in the habitable zone of its host star, an “Earth cousin” that just might have liquid water and the right conditions for life.

The newfound planet, called Kepler-186f, was first spotted by NASA’s Kepler space telescope and circles a dim red dwarf star about 490 light-years from Earth.

While the host star is dimmer than Earth’s sun and the planet is slightly bigger than Earth, the positioning of the alien world coupled with its size suggests that Kepler-186f could have water on its surface, scientists say.




One of the things we’ve been looking for is maybe an Earth twin, which is an Earth-size planet in the habitable zone of a sunlike star,” Tom Barclay, Kepler scientist and co-author of the new exoplanet research said.

This [Kepler-186f] is an Earth-size planet in the habitable zone of a cooler star. So, while it’s not an Earth twin, it is perhaps an Earth cousin. It has similar characteristics, but a different parent.

Scientists think that Kepler-186f — the outermost of five planets found to be orbiting the star Kepler-186 orbits at a distance of 32.5 million miles, theoretically within the habitable zone for a red dwarf.

Earth orbits the sun from an average distance of about 93 million miles, but the sun is larger and brighter than the Kepler-186 star, meaning that the sun’s habitable zone begins farther out from the star by comparison to Kepler-186.

Other planets of various sizes have been found in the habitable zones of their stars.

However, Kepler-186f is the first alien planet this close to Earth in size found orbiting in that potentially life-supporting area of an extrasolar system, according to exoplanet scientists.

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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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‘The Strangest Supernova We’ve Ever Seen’: A Star That Keeps Exploding — And Surviving!

A supernova signals a star’s death throes. Having exhausted its fuel for nuclear fusion, the star collapses, producing a gigantic explosion of matter and energy that can be seen from 10 billion light-years away.

The supernova shines for a few months, then fades. All that remains after the cosmic light show is either a dense, smoldering core, called a neutron star, or a gaping black hole.

At least, that is what’s supposed to happen.

Some 500 million light-years away, in a galaxy so distant it looks like little more than a smudge, a star exploded five times over the course of nearly two years, spewing the contents of 50 Jupiters and emitting as much energy as 10 quintillion suns.

This isn’t even the first time this star has gone supernova: Astronomers believe this same body was seen exploding 60 years ago.




Somehow, this “zombie” star has managed to survive one of the most powerful, destructive events known to science — multiple times.

It should make us question, researchers wrote Wednesday in the journal Nature, how much we really know about supernovas.

The discovery was made by scientists working on the Intermediate Palomar Transient Factory, which uses a telescope near San Diego to survey the night sky for ephemeral events like supernovas.

Iair Arcavi, an astrophysicist at the University of California at Santa Barbara and Las Cumbres Observatory who worked on the project, was mainly interested in stars in the early stages of explosion.

So, in September 2014, when the survey captured a fading supernova near the constellation Ursa Major, he didn’t give it much thought. The event looked like a garden variety star well on its way toward oblivion.

Five months later, an intern who had been assigned to look over old data asked Arcavi to look at something weird.

The intern pulled up a plot of the supernova’s emissions over the past 137 days — bizarrely, the explosion was getting brighter.

Figuring that this must be a fluke — maybe just a star in our galaxy twinkling weirdly — Arcavi broke the light from the explosion into its component wavelengths. This “spectrum” contained all the signatures of a supernova.

Even stranger, it looked like a nova that was only 30 days old — though the scientists had concrete proof that it had in fact been going on for months.

The event, dubbed iPTF14hls, was put on 24/7 watch.

The eyes of the Las Cumbres Observatory — a robotic network of telescopes positioned all over the world — followed the supernova as it brightened, then faded, then brightened again.

The nova hit five peaks of brightness before finally seeming to dwindle in summer 2016. But at 600 days old, it was already the longest-lived supernova ever observed.

In an analysis for Nature, Stan Woosley of the University of California at Santa Cruz, who was not involved in the research, wrote that a better understanding of iPTF14hls could lead to revelations about the evolution of massive stars.

The emergence of extremely bright supernovas and, maybe, the origins of the kind of black holes we’ve detected with gravitational waves.

For now,” he concluded, “the supernova offers astronomers their greatest thrill: something they do not understand.

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Pass it on: Popular Science

What Is Solar Wind?

The solar wind streams plasma and particles from the sun out into space. Though the wind is constant, its properties aren’t. What causes this stream, and how does it affect the Earth?

Windy star

The corona, the sun’s outer layer, reaches temperatures of up to 2 million degrees Fahrenheit (1.1 million Celsius). At this level, the sun’s gravity can’t hold on to the rapidly moving particles, and it streams away from the star.

The sun’s activity shifts over the course of its 11-year cycle, with sun spot numbers, radiation levels, and ejected material changing over time.

These alterations affect the properties of the solar wind, including its magnetic field properties, velocity, temperature and density.

The wind also differs based on where on the sun it comes from and how quickly that portion is rotating. The velocity of the solar wind is higher over coronal holes, reaching speeds of up to 500 miles (800 kilometers) per second.




The temperature and density over coronal holes are low, and the magnetic field is weak, so the field lines are open to space.  These holes occur at the poles and low latitudes, and reach their largest when activity on the sun is at its minimum.

Temperatures in the fast wind can reach up to 1 million degrees F (800,000 C). At the coronal streamer belt around the equator, the solar wind travels more slowly, at around 200 miles (300 km) per second.

Temperatures in the slow wind reach up to 2.9 million F (1.6 million C).

Affecting Earth

As the wind travels off the sun, it carries charged particles and magnetic clouds. Emitted in all directions, some of the solar wind is constantly buffeting our planet, with interesting effects.

If the material carried by the solar wind reached a planet’s surface, its radiation would do severe damage to any life that might exist. Earth’s magnetic field serves as a shield, redirecting the material around the planet so that it streams beyond it.

The force of the wind stretches out the magnetic field so that it is smooshed inward on the sun-side and stretched out on the night side.

Sometimes the sun spits out large bursts of plasma known as coronal mass ejections (CMEs), or solar storms. More common during the active period of the cycle known as the solar maximum, CMEs have a stronger effect than the standard solar wind.

When the solar wind carries CMEs and other powerful bursts of radiation into a planet’s magnetic field, it can cause the magnetic field on the back side to press together, a process known as magnetic reconnection.

Charged particles then stream back toward the planet’s magnetic poles, causing beautiful displays known as the aurora borealis in the upper atmosphere.

Though some bodies are shielded by a magnetic field, others lack their protection. Earth’s moon has nothing to protect it, so takes the full brunt.

Mercury, the closest planet, has a magnetic field that shields it from the regular standard wind, but it takes the full force of more powerful outbursts such as CMEs.

When the high- and low-speed streams interact with one another, they create dense regions known as co-rotating interaction regions (CIRs) that trigger geomagnetic storms when they interact with Earth’s atmosphere.

Studying the solar wind

NASA’s Ulysses mission launched on Oct. 6, 1990, and studied the sun at various latitudes. It measured the various properties of the solar wind over the course of more than a dozen years.

The Advanced Composition Explorer (ACE) satellite orbits at one of the special points between Earth and the sun known as the Lagrange point.

In this area, gravity from the sun and the planet pull equally, keeping the satellite in a stable orbit. Launched in 1997, ACE measures the solar wind and provides real-time measurements of the constant flow of particles.

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Scientists Detect Gravitational Waves Caused By Two Black Holes Colliding 1.3 Billion Years Ago In Historic Experiment Proving The Theory Of General Relativity

Professor Stephen Hawking said the detection marked a moment in scientific history.

Gravitational waves provide a completely new way at looking at the universe,” he told the BBC. ‘The ability to detect them has the potential to revolutionize astronomy.

This discovery is the first detection of a black hole binary system and the first observation of black holes merging.

The gravitational wave found in this study is believed to be the product of a collision between two massive black holes, 1.3 billion light years away — a remarkably extreme event that has not been observed until now.

The colliding black holes that produced these gravitational waves created a violent storm in the fabric of space and time, a storm in which time speeded up, and slowed down, and sped up again, a storm in which the shape of space was bent in this way and that way,” Caltech physicist Kip Thorne said.

Based on the physics of this particular event, LIGO scientists estimate that the two black holes in this event were about 29 and 36 times the mass of the sun, and that the event took place 1.3 billion years ago.




About three times the mass of the sun was converted into gravitational waves in a fraction of a second – with a peak power output about 50 times that of the whole visible universe. LIGO observed these gravitational waves.

The researchers detected the signal with two Laser Interferometer Gravitational-wave Observatories (LIGO) in Louisiana and Washington.

These are twin detectors carefully constructed to detect incredibly tiny vibrations from passing gravitational waves.

Once the researchers spotted a gravitational signal, they converted it into audio waves and listened to the sound of two black holes spiraling together, then merging into a larger single black hole.

We’re actually hearing them go thump in the night,” says Matthew Evans, an assistant professor of physics at MIT.

According to General Relativity, a pair of black holes orbiting around each other lose energy through the emission of gravitational waves, causing them to gradually approach each other over billions of years, and then much more quickly in the final minutes.

During the final fraction of a second, the two black holes collide into each other at nearly one-half the speed of light and form a single more massive black hole, converting a portion of the combined black holes’ mass to energy according to Einstein’s formula E=mc2.

This energy is emitted as a final strong burst of gravitational radiation.

These waves then rippled through the universe, effectively warping the fabric of space-time, before passing through Earth more than a billion years later as faint traces of their former, violent origins.

This is the holy grail of science,” said Rochester Institute of Technology astrophysicist Carlos Lousto.

The last time anything like this happened was in 1888 when Heinrich Hertz detected the radio waves that had been predicted by James Clerk Maxwell’s field-equations of electromagnetism in 1865,” added Durham University physicist Tom McLeish.

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According To Stephen Hawking, We Have Less Than 100 Years To Save The Human Race

The human race is entering the most dangerous 100 years in its history and faces a looming existential battle, Stephen Hawking has warned.

The theoretical physicist identified artificial intelligence (AI), nuclear war and genetically-engineered viruses as just some of the man-made problems that pose an imminent threat to humanity.

And the 74-year-old said that as we rapidly advance in these fields, there will be “new ways things can go wrong”.

We are at a point in history where we are “trapped” by our own advances, with humanity increasingly at risk from man-made threats but without technology sophisticated enough to escape from Earth in the event of a cataclysm.




He warned: “Although the chance of a disaster to planet Earth in a given year may be quite low, it adds up over time, and becomes a near certainty in the next thousand or ten thousand years.

By that time we should have spread out into space, and to other stars, so a disaster on Earth would not mean the end of the human race.

However, we will not establish self-sustaining colonies in space for at least the next hundred years, so we have to be very careful in this period.

He added that humans do have a knack of “saving the day” just in time, and urged fellow scientists to continue trying to make advances in their respective fields.

Prof Hawking said: “We are not going to stop making progress, or reverse it, so we have to recognise the dangers and control them. I’m an optimist, and I believe we can.

It’s important to ensure that these changes are heading in the right directions. In a democratic society, this means that everyone needs to have a basic understanding of science to make informed decisions about the future.

So communicate plainly what you are trying to do in science, and who knows, you might even end up understanding it yourself.

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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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