Advertisements

Scientists Weighed All The Mass In The Milky Way Galaxy It’s Mind Boggling

Something weird is happening in our galaxy: It’s spinning fast enough that stars ought to be flying off, but there’s something holding them together.

The substance that acts as a gravitational glue is dark matter. Yet it’s incredibly mysterious: Because it doesn’t emit light, no one has ever directly seen it. And no one knows what it’s made of, though there are plenty of wild hypotheses.

For our galaxy — and most others — to remain stable, physicists believe there’s much, much more dark matter in the universe than regular matter. But how much?

Recently astronomers using the Hubble Space Telescope and the European Space Agency’s Gaia star map attempted to calculate the mass of the entire Milky Way galaxy.

It’s not an easy thing to do. For one, it’s difficult to measure the mass of something we’re inside of. The Milky Way galaxy measures some 258,000 light-years across. (Recall that one light-year equals 5.88 trillion miles. Yes, the galaxy is enormous.) And an abundance of stars and gas obscures our view of the galactic center. The team of astronomers essentially measured the speed of some objects moving in our galaxy and deduced the mass from there (the more massive the galaxy, the faster the objects should move.)

Their answer: The galaxy weighs around 1.5 trillion solar masses. This number helps put in perspective how very small we are.

Take, for instance, where stars in the Milky Way fit in.

If you’re lucky enough to get a completely dark, clear sky for stargazing, it’s possible to behold as many as 9,000 stars above you. That’s how many are visible to the naked eye. But another 100 billion stars (or more) are out there just in our own Milky Way galaxy — yet they’re just 4 percent of all the stuff, or matter, in the galaxy.

Another 12 percent of the mass in the universe is gas (planets, you, me, asteroids, all of that is negligible mass in the grand accounting of the galaxy). The remaining 84 percent of the matter in the galaxy is the dark matter, Laura Watkins, a research fellow at the European Southern Observatory, and a collaborator on the project, explains.

The enormity of the galaxy, and the enormity of the mystery of what it’s made of, is really hard to think through. So, here, using the recent ESA-Hubble findings, we’ve tried to visualize the scale of the galaxy and the scale of the dark matter mystery at the heart of it.

As a visual metaphor, we’ve constructed a tower of mass. You’ll see that all the stars in the galaxy just represent a searchlight at the top of the building. The vast majorities of the floors, well, no one knows what goes on in there.

The mass of the Milky Way, visualized

To visualize the mass of 1.5 trillion suns, let’s start small. This is the Earth. It has a mass of 5.972 × 10^24 kilograms.

This is the Earth compared to the sun. The sun is 333,000 times more massive than Earth.

Now let’s try to imagine the mass of the 100 billion stars (or more) stars in the Milky Way galaxy.

That’s enormous.

Another 12 percent** of the mass in the galaxy is just gas floating between stars (mostly hydrogen and helium).

Here’s what the gas looks like using this same visual scale.

What about black holes? “It’s a bit harder to put an exact number of how much they contribute to the total mass, as we don’t know how many there are, but it will be a very, very very small fraction,” Watkins explains. “The supermassive black hole at the center of the Milky Way is around 6 million solar masses,” which is really tiny on the scale of the entire mass of the galaxy.

And it’s tiny on the scale of the most abundant, mysterious matter in the galaxy: the dark stuff. Again: 84 percent of the galaxy is made up of dark matter.

Dark matter doesn’t seem to interact with normal matter at all, and it’s invisible. But our galaxy, and universe, would fall apart without it.

Scientists hypothesized its existence when they realized that galaxies spin too quickly to hold themselves together with the mass of stars alone. Think of a carnival ride that spins people around. If it spun fast enough, those riders would be ripped off the ride.

Accounting for “dark matter,” and the gravity it generates, made their models of galaxies stable again. There’s some other evidence for dark matter, too: It seems to produce the same gravitational lensing effect (meaning that it warps the fabric of spacetime) as regular matter.

Now let’s try to visualize the mass of dark matter, compared to the mass of stars and gas.

And remember: This is just our galaxy. There are some hundreds of billions of galaxies in the universe.

Also remember that dark matter isn’t even the biggest mystery in the universe, in terms of scale. Some 27 percent of the universe is dark matter, and a mere 5 percent is the matter and energy you and I see and interact with.

The remaining 68 percent of all the matter and energy in the universe is dark energy (which is accelerating the expansion of the universe). While dark matter keeps individual galaxies together, dark energy propels all the galaxies in the universe apart from one another.

What you can see in the night sky might seem enormous: the thousands of stars, and solar systems, to potentially explore. But it’s just a teeny-tiny slice of what’s really out there.

**(Clarification: Ari Maller, a physics professor at New York City College of Technology, wrote in, pointing out that the proportions in our graphic —4 percent of the matter in the galaxy being stars, 12 percent gas, and 84 percent dark matter — are a bit off. They do, he says, represent the overall proportions of each in the universe. But, he writes “we don’t live in an average place,” clarifying that instead ”the gas in the Milky Way is only about 10 percent of its mass.”)

By

Source: Scientists weighed all the mass in the Milky Way galaxy. It’s mind-boggling.

Read more: http://www.newscientist.com/article/m… The latest weigh-in of our home galaxy shows much less mass from dark matter, which means we may live in a cosmic oddball

Advertisements

An Asteroid That Could Have Wiped Out A City Narrowly Missed Earth, Catching Scientists By Surprise

Topline: An asteroid that could have destroyed an entire city passed by Earth earlier this week—and scientists didn’t notice until it was just a day away from closely passing Earth.

  • The rock—named Asteroid 2019 OK—was 187 to 427 feet (or 57 to 130 meters) wide. It wasn’t big enough to cause dinosaur-level extinction, but scientists have referred to it as a “city killer” that could have leveled an entire city.
  • At its closest, it flew 45,000 miles (73,000 kilometers) from Earth. To put that into perspective, that’s less than one-fifth the distance to the moon, according to The Washington Post.
  • The asteroid caught scientists by surprise, with astronomy teams in Brazil and the U.S. only detecting the asteroid on Wednesday, just a day before it flew close to Earth.
                                          

Asteroid 2019 OK was able to evade observers because it’s relatively small compared to other major asteroids. And it was traveling fast at about 54,000 miles per hour. Plus, it only reflects enough light to be picked up by a telescope when it’s a few days out from Earth, and even then astronomers have to be looking at the right spot at the right time.

Michael Brown, an associate astronomy professor at Monash University in Australia, noted that just three days before that it passed Earth, Asteroid 2019 OK was 1,000 times fainter, making it harder to spot.

Brown added that for the past month, the asteroid has been relatively close to the sun, so it has only been visible around twilight.

NASA is already detecting larger asteroids than Asteroid 2019 OK. In 2005, Congress directed the space agency to find at least 90% of potentially dangerous asteroids larger than 140 meters by the end of 2020 (Asteroid 2019 OK was only 130 meters wide). But it has only identified about a third of those so far, according to Gizmodo.

Asteroid 2019 has already passed Earth, so it isn’t a threat right now, but others like it could be.

Follow me on Twitter. Send me a secure tip.

I’m a San Francisco-based reporter covering breaking news at Forbes. Previously, I’ve reported for USA Today, Business Insider, The San Francisco Business Times and San Jose Inside. I studied journalism at Syracuse University’s S.I. Newhouse School of Public Communications and was an editor at The Daily Orange, the university’s independent student newspaper. Follow me on Twitter @rachsandl or shoot me an email rsandler@forbes.com.

Source: An Asteroid That Could Have Wiped Out A City Narrowly Missed Earth, Catching Scientists By Surprise

Today’s New Moon May End Ramadan And Sets Up Eclipse Of The Sun And ‘Half-Blood Thunder Moon Eclipse’

A passenger jet crosses in front of the crescent moon as seen from Leavenworth, Kan at dusk Sunday, May 28, 2017. (AP Photo/Charlie Riedel)

Today the Moon is not visible. It’s the moment of New Moon exactly as this post was published, the point in our satellite’s orbit when it’s roughly between the Earth and the Sun. The far side of the Moon, only, is illuminated, and it’s invisible to us. However, June’s New Moon is rather special.

For starters, it (almost) signals the end of Ramadan, the “moon-th” long fast between dawn and sunset observed by devout Muslims, which began on May 5, and the beginning of Eid al-Fitr, one of two holy days of the year for the Islamic world. However, it’s technically not until the sighting of the crescent Moon, perhaps today, Monday, June 3, 2019, at dusk, or perhaps tomorrow on Tuesday, June 4, 2019.

The exact time of New Moon is 10:01 Universal Time today on Monday, June 3, 2019, which translates to 11:01 a.m. in London, 06:01 a.m in New York City and 03:01 a.m. in Los Angeles.

However, June’s New Moon also sets up something incredible; a total solar eclipse and a lunar eclipse. In fact, the next time we have a New Moon it will be sitting plum in front of the Sun. By a cosmic coincidence, the Moon is 400 times smaller than the Sun, but the Sun is about 400 times further away.

What is the ecliptic?

The ecliptic is the path the Sun takes through the sky. The Moon, whose orbit is inclined slightly, intersects that line–essentially Earth’s orbital plane–twice each month. Occasionally that means a New Moon covers the Sun exactly, or that a Full Moon drifts into the Earth’s shadow. As such, it’s normal for two or more eclipses to come in succession. That’s what’s about to happen.

A total solar eclipse is seen above the Bald Knob Cross of Peace Monday, Aug. 21, 2017, in Alto Pass, Ill. More than 700 people visited the over 100 foot cross for the event. (AP Photo/Charles Rex Arbogast)

A total solar eclipse is seen above the Bald Knob Cross of Peace Monday, Aug. 21, 2017, in Alto Pass, Ill. More than 700 people visited the over 100 foot cross for the event. (AP Photo/Charles Rex Arbogast)

When is the Total Solar Eclipse?

On July 2, 2019, the New Moon will exactly fit across the Sun as seen from a narrow strip of the Earth’s surface. The path of totality is narrow, around 100km wide, and is mostly over the South Pacific. In fact, only the final few minutes of the event will be visible over land. Eclipse-chasers are heading inland from La Serena in Chile, and Bella Vista in Argentina, to witness the rare event that last happened on August 21, 2017 across the USA.

Earth's shadow moves across the moon late Saturday, Aug. 16, 2008, during a partial lunar eclipse seen from Budaiya, Bahrain, in the Persian Gulf. (AP Photo/Hasan Jamali)

Earth’s shadow moves across the moon late Saturday, Aug. 16, 2008, during a partial lunar eclipse seen from Budaiya, Bahrain, in the Persian Gulf. (AP Photo/Hasan Jamali)

ASSOCIATED PRESS

When is the ‘Half-Blood Thunder Moon’ Partial Lunar Eclipse?

On July 16, 2019, a Full “Thunder” Moon will drift into the Earth’s outer shadow. It won’t enter the central shadow, so the Moon won’t go completely “blood red,” but about 65% of it will turn rosy. It will be visible from South America, Europe, Africa, Asia, and Australia, but not North America. This “Half-Blood Thunder Moon Eclipse” promises to be a special event, especially in London, where a “smiley face” half-red moon will rise in the east.

For eclipse-chasers and eclipse-photographers, July can’t come soon enough.

Wishing you clear skies and wide eyes

Follow me on Twitter @jamieacarter@TheNextEclipse or read my other Forbes articles via my profile page.

I’m an experienced science, technology and travel journalist interested in space exploration, moon-gazing, exploring the night sky, solar and lunar eclipses

Source: Today’s New Moon May End Ramadan And Sets Up Eclipse Of The Sun And ‘Half-Blood Thunder Moon Eclipse’

The 8-Dimensional Space That Must Be Searched For Alien Life – Emerging Technology from the arXiv

1.jpg

A new mathematical model suggests that signs of extraterrestrial intelligence could be common, for all we know—we’ve barely begun investigating the vastness where they might lie. The Fermi paradox is the contrast between the likelihood of life existing elsewhere in the universe and the lack if evidence for it. This is a significant conundrum. On the one hand, there is a strong sense that the conditions on Earth that led to the emergence of life cannot be unique. This makes it seem likely that life must be common…..

Read More : https://www.technologyreview.com/s/612232/the-8-dimensional-space-that-must-be-searched-for-alien-life/

 

 

 

Your kindly Donations would be so effective in order to fulfill our future research and endeavors – Thank you

 

When Neil Armstrong Went to the Moon, He Brought Souvenirs of the Wright Brothers’ Flight. Now They’re for Sale — TIME

In July of 1969, as Neil Armstrong and his crew headed toward the moon, the pioneering astronaut carried with him a very special souvenir, as an homage to another set of pioneers who paved his way. Armstrong had with him remnants of fabric and the propeller of the Wright Flyer, the craft flown by Armstrong’s…

via When Neil Armstrong Went to the Moon, He Brought Souvenirs of the Wright Brothers’ Flight. Now They’re for Sale — TIME

 

 

 

Your kindly Donations would be so effective in order to fulfill our future research and endeavors – Thank you

 

The Simplest Solution To The Expanding Universe’s Biggest Controversy -Ethan Siegel

1.jpg

In 1915, Einstein’s theory of General Relativity gave us a brand new theory of gravity, based on the geometrical concept of curved spacetime. Matter and energy told space how to curve; curved space told matter and energy how to move. By 1922, scientists had discovered that if you fill the Universe uniformly with matter and energy, it won’t remain static, but will either expand or contract. By the end of the 1920s, led by the observations of Edwin Hubble, we had discovered our Universe was expanding, and had our first measurement of the expansion rate.

The journey to pin down exactly what that rate is has now hit a snag, with two different measurement techniques yielding inconsistent results. It could be an indicator of new physics. But there could be an even simpler solution, and nobody wants to talk about it.

Standard candles (L) and standard rulers (R) are two different techniques astronomers use to measure the expansion of space at various times/distances in the past. Based on how quantities like luminosity or angular size change with distance, we can infer the expansion history of the Universe.NASA / JPL-Caltech

The controversy is as follows: when we see a distant galaxy, we’re seeing it as it was in the past. But it isn’t simply that you look at light that took a billion years to arrive and conclude that the galaxy is a billion light years away. Instead, the galaxy will actually be more distant than that.

Why’s that? Because the space that makes up our Universe itself is expanding. This prediction of Einstein’s General Relativity, first recognized in the 1920s and then observationally validated by Edwin Hubble several years later, has been one of the cornerstones of modern cosmology.

A plot of the apparent expansion rate (y-axis) vs. distance (x-axis) is consistent with a Universe that expanded faster in the past, but where distant galaxies are accelerating in their recession today. This is a modern version of, extending thousands of times farther than, Hubble’s original work. Note the fact that the points do not form a straight line, indicating the expansion rate’s change over time.Ned Wright, based on the latest data from Betoule et al. (2014)

The big question is how to measure it. How do we measure how the Universe is expanding? All methods invariably rely on the same general rules:

This could be from a wide variety of methods, ranging from observations of the nearby Universe to objects billions of light years away.

The Planck satellite’s data, combined with the other complementary data suites, gives us very tight constraints on the allowed values of cosmological parameters. The Hubble expansion rate today, in particular, is tightly constrained to be between 67 and 68 km/s/Mpc, with very little wiggle-room. The measurements from the Cosmic Distance Ladder method (Riess et al., 2018) are not consistent with this result.PLANCK 2018 RESULTS. VI. COSMOLOGICAL PARAMETERS; PLANCK COLLABORATION (2018)

For many years now, there’s been a controversy brewing. Two different measurement methods — one using the cosmic distance ladder and one using the first observable light in the Universe — give results that are mutually inconsistent. The tension has enormous implications that something may be wrong with how we conceive of the Universe.

There is another explanation, however, that’s much simpler than the idea that either something is wrong with the Universe or that some new physics is required. Instead, it’s possible that one (or more) method has a systematic error associated with it: an inherent flaw to the method that hasn’t been identified yet that’s biasing its results. Either method (or even both methods) could be at fault. Here’s the story of how.

The Variable Star RS Puppis, with its light echoes shining through the interstellar clouds. Variable stars come in many varieties; one of them, Cepheid variables, can be measured both within our own galaxy and in galaxies up to 50-60 million light years away. This enables us to extrapolate distances from our own galaxy to far more distant ones in the Universe.NASA, ESA, and the Hubble Heritage Team

The cosmic distance ladder is the oldest method we have to compute the distances to faraway objects. You start by measuring something close by: the distance to the Sun, for example. Then you use direct measurements of distant stars using the motion of the Earth around the Sun — known as parallax — to calculate the distance to nearby stars. Some of these nearby stars will include variable stars like Cepheids, which can be measured accurately in nearby and distant galaxies, and some of those galaxies will contain events like type Ia supernovae, which are some of the most distant objects of all.

Make all of these measurements, and you can derive distances to galaxies many billions of light years away. Put it all together with easily-measurable redshifts, and you’ll arrive at a measurement for the rate of expansion of the Universe.

The construction of the cosmic distance ladder involves going from our Solar System to the stars to nearby galaxies to distant ones. Each “step” carries along its own uncertainties, especially the Cepheid variable and supernovae steps; it also would be biased towards higher or lower values if we lived in an underdense or overdense region.NASA, ESA, A. FEILD (STSCI), AND A. RIESS (STSCI/JHU)

This is how dark energy was first discovered, and our best methods of the cosmic distance ladder give us an expansion rate of 73.2 km/s/Mpc, with an uncertainty of less than 3%.

However.

If there’s one error at any stage of this process, it propagates to all higher rungs. We can be pretty confident that we’ve measured the Earth-Sun distance correctly, but parallax measurements are currently being revised by the Gaia mission, with substantial uncertainties. Cepheids may have additional variables in them, skewing the results. And type Ia supernovae have recently been shown to vary by quite a bit — perhaps 5% — from what was previously thought. The possibility that there is an error is the most terrifying possibility to many scientists who work on the cosmic distance ladder.

Universal light-curve properties for Type Ia supernovae. This result, first obtained in the late 1990s, has recently been called into question; supernovae may not. in fact, have light curves that are as universal as previously thought.S. Blondin and Max Stritzinger

On the other hand, we have measurements of the Universe’s composition and expansion rate from the earliest available picture of it: the Cosmic Microwave Background. The minuscule, 1-part-in-30,000 temperature fluctuations display a very specific pattern on all scales, from the largest all-sky ones down to 0.07° or so, where its resolution is limited by the fundamental astrophysics of the Universe itself.

The final results from the Planck collaboration show an extraordinary agreement between the predictions of a dark energy/dark matter-rich cosmology (blue line) with the data (red points, black error bars) from the Planck team. All 7 acoustic peaks fit the data extraordinarily well.PLANCK 2018 RESULTS. VI. COSMOLOGICAL PARAMETERS; PLANCK COLLABORATION (2018)

Based on the full suite of data from Planck, we have exquisite measurements for what the Universe is made of and how it’s expanded over its history. The Universe is 31.5% matter (where 4.9% is normal matter and the rest is dark matter), 68.5% dark energy, and just 0.01% radiation. The Hubble expansion rate, today, is determined to be 67.4 km/s/Mpc, with an uncertainty of only around 1%. This creates an enormous tension with the cosmic distance ladder results.

An illustration of clustering patterns due to Baryon Acoustic Oscillations, where the likelihood of finding a galaxy at a certain distance from any other galaxy is governed by the relationship between dark matter and normal matter. As the Universe expands, this characteristic distance expands as well, allowing us to measure the Hubble constant, the dark matter density, and even the scalar spectral index. The results agree with the CMB data.ZOSIA ROSTOMIAN

In addition, we have another measurement from the distant Universe that gives another measurement, based on the way that galaxies cluster together on large scales. When you have a galaxy, you can ask a simple-sounding question: what is the probability of finding another galaxy a specific distance away?

Based on what we know about dark matter and normal matter, there’s an enhanced probability of finding a galaxy 500 million light years distant from another versus 400 million or 600 million. This is for today, and so as the Universe was smaller in the past, the distance scale corresponding to this probability enhancement changes as the Universe expands. This method is known as the inverse distance ladder, and gives a third method to measure the expanding Universe. It also gives an expansion rate of around 67 km/s/Mpc, again with a small uncertainty.

Modern measurement tensions from the distance ladder (red) with CMB (green) and BAO (blue) data. The red points are from the distance ladder method; the green and blue are from ‘leftover relic’ methods. Note that the errors on red vs. green/blue measurements do not overlap.AUBOURG, ÉRIC ET AL. PHYS.REV. D92 (2015) NO.12, 123516.

Now, it’s possible that both of these measurements have a flaw in them, too. In particular, many of these parameters are related, meaning that if you try and increase one, you have to decrease-or-increase others. While the data from Planck indicates a Hubble expansion rate of 67.4 km/s/Mpc, that rate could be higher, like 72 km/s/Mpc. If it were, that would simply mean we needed a smaller amount of matter (26% instead of 31.5%), a larger amount of dark energy (74% instead of 68.5%), and a larger scalar spectral index (ns) to characterize the density fluctuations (0.99 instead of 0.96).

This is deemed highly unlikely, but it illustrates how one small flaw, if we overlooked something, could keep these independent measurements from aligning.

Before Planck, the best-fit to the data indicated a Hubble parameter of approximately 71 km/s/Mpc, but a value of approximately 70 or above would now be too great for both the dark matter density (x-axis) we’ve seen via other means and the scalar spectral index (right side of the y-axis) that we require for the large-scale structure of the Universe to make sense.P.A.R. ADE ET AL. AND THE PLANCK COLLABORATION (2015)

There are a lot of problems that arise for cosmology if the teams measuring the Cosmic Microwave Background and the inverse distance ladder are wrong. The Universe, from the measurements we have today, should not have the low dark matter density or the high scalar spectral index that a large Hubble constant would imply. If the value truly is closer to 73 km/s/Mpc, we may be headed for a cosmic revolution.

Correlations between certain aspects of the magnitude of temperature fluctuations (y-axis) as a function of decreasing angular scale (x-axis) show a Universe that is consistent with a scalar spectral index of 0.96 or 0.97, but not 0.99 or 1.00.P.A.R. ADE ET AL. AND THE PLANCK COLLABORATION

On the other hand, if the cosmic distance ladder team is wrong, owing to a fault in any rung on the distance ladder, the crisis is completely evaded. There was one overlooked systematic, and once it’s resolved, every piece of the cosmic puzzle falls perfectly into place. Perhaps the value of the Hubble expansion rate really is somewhere between 66.5 and 68 km/s/Mpc, and all we had to do was identify one astronomical flaw to get there.

The fluctuations in the CMB, the formation and correlations between large-scale structure, and modern observations of gravitational lensing, among many others, all point towards the same picture: an accelerating Universe, containing and full of dark matter and dark energy.Chris Blake and Sam Moorfield

The possibility of needing to overhaul many of the most compelling conclusions we’ve reached over the past two decades is fascinating, and is worth investigating to the fullest. Both groups may be right, and there may be a physical reason why the nearby measurements are skewed relative to the more distant ones. Both groups may be wrong; they may both have erred.

But this controversy could end with the astronomical equivalent of a loose OPERA cable. The distance ladder group could have a flaw, and our large-scale cosmological measurements could be as good as gold. That would be the simplest solution to this fascinating saga. But until the critical data comes in, we simply don’t know. Meanwhile, our scientific curiosity demands that we investigate. No less than the entire Universe is at stake.

Your kindly Donations would be so effective in order to fulfill our future research and endeavors – Thank you
https://www.paypal.me/ahamidian

Share this:

Like this:

Like Loading...

From Earth To Obseravable Universe — Astrogirl

Is universe infinite? Or Does it have an end? Then What lies beyond it? Exploring universe…….. From our home planet earth to moon at a distance to 3,84,400 km. Next, to mars distance 22.5 crore km then crossing our solar system having a diameter of 9.09 billion km. Moving ahead to NASA’s satellite Voyager 1 […]

via FROM EARTH TO OBSERVABLE UNIVERSE — Astrogirl

 

Your kindly Donations would be so effective in order to fulfill our future research and endeavors – Thank you
https://www.paypal.me/ahamidian

 

%d bloggers like this:
Skip to toolbar