Tag: Cosmology

Why Is The Sky Dark At Night?

That question is not as simple as it may sound. You might think that space appears dark at night because that is when our side of Earth faces away from the Sun as our planet rotates on its axis every 24 hours.

But what about all those other far away suns that appear as stars in the night sky? Our own Milky Way galaxy contains over 200 billion stars, and the entire universe probably contains over 100 billion galaxies.

You might suppose that that many stars would light up the night like daytime!

Until the 20th century, astronomers didn’t think it was even possible to count all the stars in the universe. They thought the universe went on forever. In other words, they thought the universe was infinite.

Besides being very hard to imagine, the trouble with an infinite universe is that no matter where you look in the

night sky, you should see a star.

Stars should overlap each other in the sky like tree trunks in the middle of a very thick forest.

But, if this were the case, the sky would be blazing with light. This problem greatly troubled astronomers and became known as “Olbers’ Paradox.” A paradox is a statement that seems to disagree with itself.

To try to explain the paradox, some 19th century scientists thought that dust clouds between the stars must be absorbing a lot of the starlight so it wouldn’t shine through to us.




But later scientists realized that the dust itself would absorb so much energy from the starlight that eventually it would glow as hot and bright as the stars themselves.

Astronomers now realize that the universe is not infinite. A finite universe—that is, a universe of limited size—even one with trillions and trillions of stars, just wouldn’t have enough stars to light up all of space.

Although the idea of a finite universe explains why Earth’s sky is dark at night, other causes work to make it even darker.

Not only is the universe finite in size, it is also finite in age. That is, it had a beginning, just as you and I did.

The universe was born about 15 billion years ago in a fantastic explosion called the Big Bang. It began at a single point and has been expanding ever since.

Because the universe is still expanding, the distant stars and galaxies are getting farther away all the time. Although nothing travels faster than light, it still takes time for light to cross any distance.

So, when astronomers look at a galaxy a million light years away, they are seeing the galaxy as it looked a million years ago.

The light that leaves that galaxy today will have much farther to travel to our eyes than the light that left it a million years ago or even one year ago, because the distance between that galaxy and us constantly increases.

That means the amount of light energy reaching us from distant stars dwindles all the time. And the farther away the star, the less bright it will look to us.

The universe, both finite in size and finite in age, is full of wonderful sights.

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Pass it on: Popular Science

Our bodies Are Made Of Remnants Of Stars And Massive Explosions In The Galaxies

galaxy

It seems natural to assume that the matter from which the Milky Way is made was formed within the galaxy itself, but a series of new supercomputer simulations suggests that up to half of this material could actually be derived from any number of other distant galaxies.

This phenomenon, described in a paper by group of astrophysicists from Northwestern University in the US who refer to it as “intergalactic transfer”, is expected to open up a new line of research into the scientific understanding of galaxy formation.




Led by Daniel Anglés-Alcázar, the astrophysicists reached this intriguing conclusion by implementing sophisticated numerical simulations which produced realistic 3D models of galaxies and followed their formation from shortly after the Big Bang to the present day.

The researchers then employed state-of-the-art algorithms to mine this sea of data for information related to the matter acquisition patterns of galaxies.

Through their analysis of the simulated flows of matter, Anglés-Alcázar and his colleagues found that supernova explosions eject large amounts of gas from galaxies, which causes atoms to be conveyed from one system to the next via galactic winds.

galaxy

In addition, the researchers note that this flow of material tends to move from smaller systems to larger ones and can contribute to up to 50 percent of the matter in some galaxies.

Anglés-Alcázar and his colleagues use this evidence, which is published in Monthly Notices of the Royal Astronomical Society, to suggest that the origin of matter in our own galaxy including the matter that makes up the Sun, the Earth, and even the people who live on it may be far less local than traditionally believed.

galaxy

“It is likely that much of the Milky Way’s matter was in other galaxies before it was kicked out by a powerful wind, traveled across intergalactic space and eventually found its new home in the Milky Way,” Anglés-Alcázar says.

The team of astrophysicists now hopes to test the predictions made by their simulations using real-world evidence collected by the Hubble Space Telescope and other ground-based observatories.

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Stephen Hawking’s Final Paper Proposes Way To Detect The ‘Multiverse’

Stephen Hawking’s final research paper could help astronomers find evidence that our universe is just one among many in a larger “multiverse,” according to media reports.

The famed cosmologist, who died last week at the age of 76, is lead author of a study called “A Smooth Exit from Eternal Inflation?” which was originally submitted to an unnamed journal last July.

On March 4 — just 10 days before Hawking’s death — his co-author, Thomas Hertog, a professor of theoretical physics at KU Leuven University in Belgium, submitted a revised version of the manuscript for further review, according to British newspaper The Sunday Times.




The inflation referenced in the paper’s title is the incredible expansion of space-time theorized to have occurred in the first few moments after the Big Bang, which created the universe.

Many physicists believe that this dramatic ballooning wasn’t limited to our neck of the cosmic woods but rather happened repeatedly, spawning multiple universes — perhaps an infinite number of them.

Not everyone is so enthusiastic about the paper’s potential.

For example, Neil Turok, the director of the Perimeter Institute for Theoretical Physics in Canada, told The Sunday Times, “I remain puzzled as to why [Hawking] found this picture interesting.

However it’s ultimately received, the manuscript — which you can read for free at the online preprint site arXiv.org — is a reminder that Hawking was a deep thinker committed to tackling some of the universe’s biggest mysteries.

He will be missed a great deal, by his colleagues and the general public alike.

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Looks Like The Universe Isn’t As Special As We Thought

There are a few ideas being tossed around perplexing to know what competence be function around these incomparable galaxies. Some of a theories concentration on a thought of tidal army in a formless blank of space.

If we have communication between dual bigger galaxies, afterwards in this communication there will be some bridges or tidal bridges [between a galaxies],” Müller says.

The sobriety of a incomparable star will usually slice out stars and gas identical to a sobriety of a moon, that creates a tides on a Earth.

The ensuing dwarf galaxies would circuit a incomparable ones in a craft and along a same direction, identical to what Müller and colleagues observed.

But researchers have no thought how prolonged these tidal dwarf galaxies would final after a collision, and that does have implications for cosmology.




The thing about tidal dwarf galaxies is that we don’t know how prolonged they live. Can they be stable? This is in contrariety to a customary model, where we consider that a dwarf galaxies are a building blocks of a universe.

“They are a initial galaxies that are combined and they combine [to form incomparable galaxies], so they are a oldest objects. But with tidal dwarf galaxies, they would be a youngest objects,” Müller says.

Going from building retard to afterthought is a lot to reconcile.

People consider we have rescued dark matter, though dim matter is usually a hypothesis,” Müller says. “We are still looking for it.

Dark matter is a vicious member of a customary model, assisting to explain a gravitational lift between objects in a universe, that can’t be explained by a manifest matter in a universe.

This investigate isn’t a genocide knell for a customary cosmological model, that can explain what happened in a star moments after a Big Bang, calculate a series of atoms that were benefaction in a star mins after it started, explain a participation of vast credentials radiation, and explain how matter is distributed in a star today.

It’s a biggest hits list that’s tough to beat.

How to determine a observations with a theory? More calculations, some-more thinking, and some-more data.

For this study, Muller and colleagues looked during a velocities of a satellite galaxies in propinquity to a viewpoint here on Earth to extrapolate some-more fact about their transformation around Centaurus A.

“We’re means to magnitude a velocities of these galaxies along a lines of sight, though we’re not means to magnitude a quickness of a star perpendicular to a line of sight,” Boylan-Kolchin says.

So we don’t know if they’re rotating in planes or if they demeanour like they’re rotating in planes.

There are ways to answer that question. The arriving James Webb Space Telescope, in further to a brave Hubble, could assistance astrophysicists investigate some-more galaxies and their satellites.

By comparing images of a same star taken months or years apart, Boylan-Kolchin says, researchers competence be means to get a improved clarity of how dwarf galaxies are orbiting their hosts, generally if researchers wish to take a demeanour during a circuitously Andromeda.

But it won’t be easy.

It’s like perplexing to magnitude hair expansion on a moon—from Earth. It’s really slow, really excellent measurements, though it should be possible,” Boylan-Kolchin says.

At a really least, these new observations will let people take a closer demeanour during how a galaxies formed.

I consider now people have to take it seriously, some-more severely than before.Müller says.

Before, there was always this guess that we are atypical, we are usually a special box in a universe, that routinely it works.

“But now we have shown that another star organisation circuitously also has this feature, so a village has to figure out how we can make such structures some-more frequently.

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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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Half Of The Universe’s Missing Matter Has Been Found

Scientists have just found half of the universe’s missing matter in a landmark discovery.

Separate teams at the Institute of Space Astrophysics in Orsay, France, and the University of Edinburgh have finally discovered the missing links between galaxies after years of speculation.

The missing matter is made of particles called baryons which link galaxies together through filaments of hot, diffuse gas.




Previous observations in space had not picked the matter up because the gas is tenuous and not hot enough for X-ray telescopes.

But scientists believed there should be more normal matter out there than had been previously been discovered and set about to show the threads of gas actually exist.

Both groups found confirmation that the gas in the areas they were studying were dense enough to form filaments, ‘definitive’ evidence they existed between the galaxies.

Hideki Tanimura, leader of one of the groups in France said that the missing baryon problem had been solved.

Ralph Kraft at the Harvard-Smithsonian Center for Astrophysics in Massachusetts, added: “Everybody sort of knows that it has to be there, but this is the first time that somebody has come up with a definitive detection.

This goes a long way toward showing that many of our ideas of how galaxies form and how structures form over the history of the universe are pretty much correct.”

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Speedy White Dwarf Fragment Might Have Survived A Partial Supernova

Astronomers have discovered a star like none seen before. They think it may be the remnant of an incomplete supernova explosion, something that would explain one mystery, but create enough new ones to keep them happily hunting for a long time.

LP 40-365 is a 15th magnitude star, making it far too faint to see with the naked eye, but much brighter than the vast majority of objects recorded in sky maps.




Catalogs of stars registered the fact that it appears to be traveling very rapidly compared to the rest of the galaxy, and interested by such speedster stars, Professor Lilia Ferrario of the Australian National University and some fellow astronomers decided to check it out.

What they found, Ferrario told IFLScience, was more fascinating than anyone expected. LP 40-365’s light spectrum clearly marks it as a white dwarf, but one smaller than any we have seen before – just 0.14 times the mass of the Sun.

White dwarfs are extremely compact stars, where gravitational collapse is prevented by the pressure exerted by a gas of degenerate electrons. A teaspoon of white dwarf material would weigh many tonnes on Earth,” Ferrario said in a statement.

White dwarfs are the remnants of medium to large stars that have run out of fuel. They are called dwarfs because they are very compact, but, even with all the material they have lost, their masses are close to that of the Sun.

LP 40-365 “must have interacted with something to end up the way it is,” Ferrario told IFLScience.

The explanation Ferrario and her colleagues have presented in Science is that LP 40-365 is the result of what is called a Iax supernova.

Type Ia supernovas are thought to occur when a white dwarf star that is part of a binary system with another star draws gas away from its companion until it has so much it explodes, although a subclass is triggered by the collision of two white dwarfs.

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Pass it on: New Scientist