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Aug 16, 2018, 03:24 PM
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Author Topic: NEWS ON SPACE AND OUR PLANETARY SYSTEM  (Read 346833 times)
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« Reply #1755 on: Aug 10, 2018, 04:31 AM »

Astronomers discover bizarre rogue planet glowing with auroras

Mike Wehner

When astronomers are searching the depths of space for new objects it’s typically easier to find undiscovered planets if they’re orbiting a star. That’s because spotting the dips in the star’s brightness as the planet passes in front of it gives away its presence. Finding a solitary planet — called a “rogue” planet — is more difficult, but researchers just managed to spot one using a radio telescope, and it’s a real weirdo.

The planet is known as… *inhales* …SIMP J01365663+0933473. It’s an absolutely massive alien world that is nearly big enough to be classified as a brown dwarf. Brown dwarf planets are sometimes called “failed stars” because they’re nearly large enough for fusion to begin taking place in their core, but that’s not even the most unique thing about this particular planet.

What’s really special about that planet with the big long name is that it has a magnetic field 200 times stronger than even the mighty Jupiter. That’s an incredible finding, and it suggests that there’s some very interesting things going on above the planet’s surface. One of those things is a strong aurora, often called “Northern Lights” here on Earth.

Auroras on Earth are created when charged particles from the Sun interact with Earth’s magnetic field. This newfound world has no star in the neighborhood, and researchers still aren’t sure how planets like this are able to seemingly create their own auroras.

Another cool discover about this huge planet is that it’s just a baby. It’s thought to be only around 200 million years old, which makes it an infant in planetary terms, and its surface is boiling hot. If you were to stand on it (not a good idea) you’d be subjected to temperatures in excess of 1,500 degrees Fahrenheit. You’d have a bad time.

The planet is only around 20 light years from Earth, but it’s not really doing much besides relaxing in the vastness of space. We’d likely never have a reason to go there, but it’s kind of cool that it exists at all.

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« Reply #1756 on: Aug 11, 2018, 04:34 AM »

Fastest human spacecraft to launch for the sun’s corona


On August 11, NASA will launch a super-fast space probe that will travel through the sun’s atmosphere. Thanks to sophisticated instruments and state-of-the-art thermal shielding, the spacecraft will be able to go where no other human-made machinery has gone before. Its mission is to answer some of the most pressing mysteries about the sun and stars in general.

The Parker Solar Probe will launch tomorrow, with a launch window starting at 3:33 a.m. EDT, aboard a United Launch Alliance Delta IV Heavy rocket that will light the sky above Cape Canaveral, Florida. The light-weight probe — no bigger than a compact vehicle — should become the fastest human spacecraft ever, a record currently held by the New Horizons probe launched in 2006. NASA estimates that the probe will reach a top speed of 692,000 kilometers per hour (430,000 miles per hour).

This breakneck speed won’t last long though, as NASA plans to slow Parker down so it can safely enter the sun’s orbit. Engineers plan to lower the probe’s velocity by making a gravity slingshot around Venus, which Parker will circle seven times, with each pass bringing it closer to the surface of the sun. Gravity slingshots are typically used to accelerate spacecraft by catching orbital momentum from the planet. However, the reverse process (approaching the planet in the opposite direction that it’s orbiting the Sun) will be used to slow down the craft.

During its closest approach to the sun, Parker will stand just 3.8 million miles away from the sun’s surface, where it will be exposed to temperatures of millions of degrees Celsius and 475-times the solar power an Earth-orbiting satellite experiences.

    “We’ve been studying the Sun for decades, and now we’re finally going to go where the action is,” said Alex Young, associate director for science in the Heliophysics Science Division at NASA’s Goddard Space Flight Center in Greenbelt, Maryland.

Watch: https://www.youtube.com/watch?v=i_z19KPvV1w

There’s a lot of things we don’t know about the hot ball of glowing plasma at the heart of our solar system. For one, the sun is dynamic, constantly belching magnetized material outward even as far as beyond Pluto’s orbit. The intensity and frequency of these ejections wax and wane according to a nearly periodical 11-year solar cycle. For instance, at the peak of the cycle, our star grows more sunspots and spews more solar flares, which can damage satellites in Earth’s orbit and even our electrical grids.

The influence of solar activity on Earth and other worlds is known as space weather. Now, scientists are looking to understand the sun and its weather activity by sending a probe to its surface, just like weather satellites in orbit that track Earth.

This mission has been in the making for the last 60 years, ever since physicist Eugene Parker published a groundbreaking scientific paper in 1958 theorizing the existence of the solar wind.

    “The Sun’s energy is always flowing past our world,” said Nicky Fox, Parker Solar Probe’s project scientist at the Johns Hopkins University Applied Physics Lab. “And even though the solar wind is invisible, we can see it encircling the poles as the aurora, which are beautiful – but reveal the enormous amount of energy and particles that cascade into our atmosphere. We don’t have a strong understanding of the mechanisms that drive that wind toward us, and that’s what we’re heading out to discover.”

For its mission, Parker carries a range of instruments that can study the sun both remotely and in situ (directly) — the kind of observations that might unravel some of the sun’s most well-kept secrets.

Of course, NASA has several specific questions it wants Parker to investigate. One of them has to do with the mystery of the acceleration of solar wind — the constant ejection of magnetized material from the sun. Somewhere, somehow, this solar wind is accelerated to supersonic speeds.

Parker will fly straight through the corona — the sun’s atmosphere that extends millions of kilometers into outer space. The corona is scorching hot, reaching temperatures in the range of millions of degrees Celsius. However, the sun’s surface has a temperature of only about 6,000 degrees Celsius. This makes no sense at first glance: how is it possible that the surface of the sun is so cold compared to its atmosphere? Well, scientists hope that Parker might come up with an answer to this counter-intuitive conundrum.

To answer these questions and more, Parker will rely on instruments such as the FIELDS suite which will capture the scale and shape of electric and magnetic fields in the Sun’s atmosphere. Of course, there will also be an imaging instrument — because how could a probe fly this close to the sun and not take awesome pictures? Called WISPR, short for Wide-Field Imager for Parker Solar Probe, the instrument is mainly designed to image coronal mass ejections (CMEs), jets and other solar ejecta.

The SWEAP suite of instruments, short for Solar Wind Electrons Alphas and Protons Investigation, will count the most abundant particles in the solar wind — electrons, protons, and helium ions — and measure such properties as velocity, density, and temperature to improve our understanding of the solar wind and coronal plasma. Finally,  ISʘIS suite – short for Integrated Science Investigation of the Sun, and including ‘ʘ’, the symbol for the Sun, in its acronym – measures particles across a wide range of energies in order to understand their life cycles — that is, where they came from, how they became accelerated, and how they move out from the Sun through interplanetary space.

The science that will enable Parker to survive the sun’s corona

But how will Parker keep its ‘wings’ from melting? During its closest flyby, Parker will be only 6.1 million kilometers (3.8 million miles) from the sun’s surface, where temperatures can reach millions of degrees Celsius. But there’s a catch — just because the corona is that hot, it doesn’t mean that the probe will ‘feel’ that temperature due to the phenomenon of heat transfer. Simply put, some mediums conduct heat (energy) better than others.

For instance, if you stand on a tile floor you’ll feel cold but if you stand on a carpet your feet feel comfortably warm. However, both kinds of surfaces have the same temperature because they’ve had time to reach a thermal equilibrium — it’s just that the tile floor is a good heat conductor, which will make your feet seem cold as heat passes from your feet into the tile. The carpet is a poor heat conductor and it would take ages for your feet to match its lower temperature.

Bearing this in mind, we can now understand how Parker won’t get obliterated — even though the corona has a very high temperature, the sun’s outer atmosphere has a very low density and, hence, is a poor heat conductor. According to NASA, Parker’s sun-facing side will be heated to only about 1,644 degrees Kelvin (1,370 C° or 2,500 F°).

Watch: https://www.youtube.com/watch?v=TN6rZF5dSRg

That’s still a lot, to be fair, which is why the Parker Solar Probe is equipped with a cutting-edge heat shield called the thermal protection system, or TPS. It’s a sandwich of carbon-carbon composite surrounding nearly 4.5 inches of carbon foam, which is about 97% air. Thanks to its lightweight materials, the TPS only weighs 72.5 kilograms (160 pounds) despite being nearly 2.4 meters (8 feet) in diameter. Anything behind the shield shouldn’t heat to more than 300 Kelvin (30 C° or 85 F°)! A cooling system that runs on pressurized deionized water will keep temperatures at manageable levels in the parts fully exposed to the sun.

The key is for the shield to be always facing the sun, but sometimes the probe will have to operate for long periods of time without being able to communicate with Earth. To solve this predicament, NASA engineers have designed a fault management system that self-corrects the probe’s course and direction facing the sun to ensure that the scientific instruments stay cool and functioning.

If for some reason Parker doesn’t launch by 23 August, it will have to wait until May 2019 for the next launch opportunity, when Earth and Venus will again be lined up correctly. Let’s keep our fingers crossed for a safe journey to the sun!

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« Reply #1757 on: Aug 12, 2018, 10:30 AM »

Parker Solar Probe Launches on NASA Voyage to ‘Touch the Sun’

By Kenneth Chang
Aug. 11, 2018

Atop three columns of flame at 3:31 a.m. Eastern time, NASA’s Parker Solar Probe lifted toward space on Sunday. The launch was the second attempt to carry the spacecraft, which NASA touts will “touch the sun” one day, into orbit after a scrub early on Saturday.

The probe — which will study the sun’s outer atmosphere as well as the stream of particles known as solar wind — was carried on top of a Delta IV Heavy rocket built and operated by United Launch Alliance, a joint venture between Boeing and Lockheed Martin. It is one of the most powerful rockets currently available. Its third stage gave the probe the extra kick it needs to escape Earth’s gravity at a high enough velocity to put it on course for Venus in November, and eventually the sun.

    3-2-1… and we have liftoff of Parker #SolarProbe atop @ULAlaunch’s #DeltaIV Heavy rocket. Tune in as we broadcast our mission to “touch” the Sun: https://t.co/T3F4bqeATB pic.twitter.com/Ah4023Vfvn
    — NASA (@NASA) August 12, 2018

The Parker Solar Probe is designed to expand our understanding of the sun, measuring electrical and magnetic fields, cataloging the ingredients of the solar wind and photographing the corona — the outer atmosphere that is millions of degrees hotter than the sun’s surface. Instruments on the spacecraft will be able to detect details that cannot be seen from farther away, and hopefully fill in many of the blanks in human understanding of our star.

The spacecraft will eventually pass within 4 million miles of the sun’s surface, close enough to skim through the star’s outer atmosphere. Four million miles is about one-tenth the distance between the sun and Mercury, the innermost planet of the solar system.

At its closest approach, the outside of the spacecraft will reach 2,500 degrees Fahrenheit, or about the melting temperature of steel. But a 8-foot-wide carbon composite shield will absorb the intense heat and keep the spacecraft and its instruments cool. The foam in the shield is so fluffy — 97 percent empty space — that it adds only 160 pounds of weight.

Solar wind is the stream of charged particles — primarily protons and electrons — that continuously flows outward from the sun through the solar system at a speed of about a million miles per hour. Earth’s magnetic field generates a bubble that deflects the solar wind around our planet and results in the beautiful aurora borealis, also known as the Northern and Southern lights, that flicker at night in the polar regions.

Understanding the solar wind is of importance to scientists and policymakers because of its potential to devastate civilization.

Occasionally, a huge explosion, called a coronal mass ejection, erupts from the sun, sending a larger-than-usual deluge of particles into space. In 1859, one of those explosions made a direct hit on Earth, disrupting telegraph wires in America and Europe. If the same thing happened today, it could cause continentwide blackouts, potentially requiring months to years to repair.

In 2012, one of NASA’s sun-watching spacecraft, Stereo-A, detected an explosion comparable to the 1859 explosion. Fortunately, it was not aimed in Earth’s direction.

During its first plunge to the sun, the probe will pass within about 15 million miles of the sun. That’s close enough for the instruments to collect some useful data, but the greater excitement will come later.

The probe will also zip close to Venus, using that planet’s gravity as a brake to sap energy from its motion and allow it to spiral inward, closer to the sun. After seven such course changes, the probe will be in an 88-day elliptical orbit of the sun, with a closest approach of about 3.8 million miles.

In total, the spacecraft will complete 24 orbits, and the mission is to end in 2025.

During its later orbits, the strong pull of the sun’s gravity will accelerate the probe to 430,000 miles per hour, which will be the fastest human-made object ever.

The spacecraft is named for Eugene N. Parker, a retired University of Chicago astrophysicist who was the first to predict the solar wind. It is the first time NASA has named a mission for a living person.

Dr. Parker, 91, who took in the launch from Florida on Sunday, expressed his enthusiasm about the scientific potential of the mission.

“All I can say is wow, here we go,” he said on a NASA broadcast after the liftoff. “We’re in for some learning over the next several years.”

WATCH: https://www.nytimes.com/video/science/100000006012333/nasa-parker-solar-probe.html?action=click&gtype=vhs&version=vhs-heading&module=vhs&region=title-area&cview=true&t=204

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« Reply #1758 on: Aug 13, 2018, 04:24 AM »

All this time, outer space was secretly much closer than we thought

Nothing changed with our atmosphere — just our calculations and assumptions have gotten better.
Horizon atmosphere.


A new research paper proposes that we are all one step closer to space than we assumed. If the calculations are proven correct, we might, in fact, be a full 12 miles closer. The exact altitude of this boundary — the plane where the laws that order airspace get superseded by those governing outer space — is an important piece of information in world politics, the authors note.
The recalculated frontier

    “The argument about where the atmosphere ends and space begins predates the launch of the first Sputnik,” wrote Jonathan McDowell, an astrophysicist at the Harvard-Smithsonian Center for Astrophysics, and sole author of the new paper. “The most widely accepted boundary is the so-called Karman Line, nowadays usually set to be 62 miles altitude.”

The boundary between atmosphere and space is known as the Kármán line after its discoverer, aerodynamics researcher, and engineer Theodore von Kármán. In 1963, when the line was proposed, von Kármán suggested that the speed needed to lift an object into the atmosphere is the same as the speed needed to keep it in orbit around the Earth. He also believed that the horizontal movement of the object on orbit would counteract the effects of gravity. According to McDowell, however, this just isn’t true. The position of the line was therefore calculated based on a faulty assumption and without any real means of testing — this was a time before real-life orbital readings could be performed.

For his study, McDowell drew on North American Aerospace Defense Command (NORAD) data detailing the orbital comings and goings of over 43,000 satellites. Most of these orbited far above the Karman line, so McDowell removed their paths from the study. About 50 satellites, however, were used in the calculations.

What set these 50 apart is that they all performed at least full rotations around the planet at low altitude (below 100km / 63 miles) as they re-entered the atmosphere at the end of their missions. The Soviet satellite Elektron-4, for example, performed ten full rotations around the planet at around 83 km (52 miles) before it burned up in the atmosphere in 1997. In other words, these cases revealed that satellites could still behave as if they were in outer space below the Karman line — which raises the possibility that the altitude line itself is overestimated.

McDowell used a mathematical model to find the altitude at which the orbits of these satellites finally started to degrade and they dropped back into the atmosphere — he found that these events occurred between 70 to 82 kilometers (41 to 55 miles) high. However, for most satellites, the 80-kilometer (50-mile) mark seems to be the lowest possible stable orbit. So McDowell proposes this altitude as the new accepted boundary between our atmosphere and outer space.

The suggestion may actually get some traction in the scientific community. The 80-kilometer mark fits with what we know of the atmosphere’s structure. The mesopause, stretching roughly between 83 and 100 kilometers high, is an area where the air’s chemical composition changes dramatically and charged particles become more abundant — which harkens more to the state of gases in outer space than those in our atmosphere. Below the lower edge of the mesopause, Earth’s atmosphere becomes a stronger force for airborne objects to reckon with, McDowell wrote.

    “It is noteworthy that meteors (traveling much more quickly) usually disintegrate in the 43 to 62 miles altitude range, adding to the evidence that this is the region where the atmosphere becomes important,” he adds.

While most outer space operations, such as rocket launches, should remain relatively unchanged if the new boundary is adopted, McDowell wrote, it could raise some important political and territorial issues

The airspace above each country is generally considered to be part of that country — but outer space isn’t owned by anyone. If the limit of space is set at 100 kilometers high, for example, and an unauthorized satellite passes at 80 kilometers high, it could be rightfully considered an act of military aggression between states. Seeing as satellites tend to sometimes wobble up and down along their orbits, a lower limit of the atmosphere might help ease tensions.

The paper “The edge of space: Revisiting the Karman Line” will be published in the October issue of the journal Acta Astronautica.

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« Reply #1759 on: Aug 14, 2018, 04:25 AM »

Unique 4.6-billion-year-old meteorite is a remnant of the early solar system


A never-before-seen space rock — older than Earth itself! — stands out among the 40,000 meteorites researchers have recovered so far. Scientists claim this is the oldest igneous meteorite found thus far and by studying it they hope to learn more about how the solar system formed and evolved.
Northwest Africa (NWA) 11119 is the oldest igneous meteorite recorded. Credit: University of New Mexico.

Northwest Africa (NWA) 11119 is the oldest igneous meteorite recorded. Credit: University of New Mexico.

About 4.6 billion years ago, a massive cloud of gas and dust collapsed under its own gravity, forming a spinning disk with a proto-sun at its center. Under the influence of gravity, material accreted into small chunks that got larger and larger, forming planetesimals. Many such objects likely broke back apart as they collided with each other, but others would have coalesced — eventually becoming planets and moons. However, the journey to building a planet was quite messy. One study published in Nature concluded that Earth lost nearly 40 percent of its mass as vapor during collisional growth.

The weird meteorite described by Carl Agee, the Director of the University of New Mexico’s Institute of Meteoritics, and colleagues provides chemical evidence that silica-rich crustal rocks were forming on planetesimals at least 10 million years before the assembly of the terrestrial planets.

At first, however, the space rock looked pretty unassuming. The researchers initially thought that the rock — called Northwest Africa 11119, as it was discovered in the sand dunes of Mauritania — was terrestrial in origin due to its light appearance and silica-rich content.

The rock, which was originally found by a nomad and later sourced by Agee via a meteorite dealer, was handed over to graduate student and lead author Poorna Srinivasan to study its mineralogy. Using an electron microprobe and a CT (computed tomography), Srinivasan started noticing unusual details in NWA 11119 and concluded it is extraterrestrial in origin, judging from its oxygen isotopes. What’s more, the silica-rich achondrite meteorite contains information involving the range of volcanic rock compositions (their ‘recipes’) within the first 3.5 million years of solar system creation.

    “The age of this meteorite is the oldest, igneous meteorite ever recorded,” Agee said in a statement. “Not only is this just an extremely unusual rock type, it’s telling us that not all asteroids look the same. Some of them look almost like the crust of the Earth because they’re so light colored and full of SiO2. These not only exist, but it occurred during one of the very first volcanic events to take place in the solar system.”

Watch: https://www.youtube.com/watch?v=LAp8aTdeNn8

According to Srinivasan, the mineralogy of the rock is unlike anything the researchers have worked on before. One of its most striking characteristics is that large silica crystals of tridymite — which are similar to quartz — comprise about 30 percent of the total meteorite. This kind of composition is unheard of in meteorites — which typically have ‘basaltic’ compositions with much lower abundances of silica — and can only be found in certain volcanic rocks from Earth.

Subsequent investigations using inductively coupled plasma mass spectrometry determined the precise formation age of the meteorite: 4.565 billion years.

But where exactly NWA 11119 formed is still a mystery.

    “Based on oxygen isotopes, we know it’s from an extraterrestrial source somewhere in the solar system, but we can’t actually pinpoint it to a known body that has been viewed with a telescope,” said Srinivasan. “However, through the measured isotopic values, we were able to possibly link it to two other unusual meteorites (Northwest Africa 7235 and Almahata Sitta) suggesting that they all are from the same parent body – perhaps a large, geologically complex body that formed in the early solar system.”

It’s possible that this larger parent body was torn to pieces through the collision with some other asteroid or planetesimal, ejecting fragments that would eventually hit Earth at a yet unknown time in the past.

    “The meteorite studied is unlike any other known meteorite,” says co-author and ASU School of Earth and Space Exploration graduate student Daniel Dunlap. “It has the highest abundance of silica and the most ancient age (4.565 billion years old) of any known igneous meteorite. Meteorites like this were the precursors to planet formation and represent a critical step in the evolution of rocky bodies in our solar system.”

The findings published in the journal Nature Communications are important because they help scientists piece together how the building blocks of planets formed in the early solar system. Specifically, this “missing part of the puzzle that we’ve now found that tells us these igneous processes act like little blast furnaces that are melting rock and processing all of the solar system solids,” Agee said.

    “Ultimately, this is how planets are forged,” he added.

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« Reply #1760 on: Aug 15, 2018, 04:39 AM »

The universe’s rate of expansion is in dispute – and we may need new physics to solve it


Next time you eat a blueberry (or chocolate chip) muffin consider what happened to the blueberries in the batter as it was baked. The blueberries started off all squished together, but as the muffin expanded they started to move away from each other. If you could sit on one blueberry you would see all the others moving away from you, but the same would be true for any blueberry you chose. In this sense galaxies are a lot like blueberries.

Since the Big Bang, the universe has been expanding. The strange fact is that there is no single place from which the universe is expanding, but rather all galaxies are (on average) moving away from all the others. From our perspective in the Milky Way galaxy, it seems as though most galaxies are moving away from us – as if we are the centre of our muffin-like universe. But it would look exactly the same from any other galaxy – everything is moving away from everything else.

To make matters even more confusing, new observations suggest that the rate of this expansion in the universe may be different depending on how far away you look back in time. This new data, published in the Astrophysical Journal, indicates that it may time to revise our understanding of the cosmos.

Hubble’s challenge

Cosmologists characterise the universe’s expansion in a simple law known as Hubble’s Law (named after Edwin Hubble – although in fact many other people preempted Hubble’s discovery). Hubble’s Law is the observation that more distant galaxies are moving away at a faster rate. This means that galaxies that are close by are moving away relatively slowly by comparison.

The relationship between the speed and the distance of a galaxy is set by “Hubble’s Constant”, which is about 44 miles (70km) per second per Mega Parsec (a unit of length in astronomy). What this means is that a galaxy gains about 50,000 miles per hour for every million light years it is away from us. In the time it takes you to read this sentence a galaxy at one million light years’ distance moves away by about an extra 100 miles.

This expansion of the universe, with nearby galaxies moving away more slowly than distant galaxies, is what one expects for a uniformly expanding cosmos with dark energy (an invisible force that causes the universe’s expansion to accelerate ) and dark matter (an unknown and invisible form of matter that is five times more common than normal matter). This is what one would also observe of blueberries in an expanding muffin.

The history of the measurement of Hubble’s Constant has been fraught with difficulty and unexpected revelations. In 1929, Hubble himself thought the value must be about 342,000 miles per hour per million light years – about ten times larger than what we measure now. Precision measurements of Hubble’s Constant over the years is actually what led to the inadvertent discovery of dark energy. The quest to find out more about this mysterious type of energy, which makes up 70% of the energy of the universe, has inspired the launch of the world’s (currently) best space telescope, named after Hubble.

Cosmic showstopper

Now it seems that this difficulty may be continuing as a result of two highly precise measurements that don’t agree with each other. Just as cosmological measurements have became so precise that the value of the Hubble constant was expected to be known once and for all, it has been found instead that things don’t make sense. Instead of one we now have two showstopping results.

On the one side we have the new very precise measurements of the Cosmic Microwave Background – the afterglow of the Big Bang – from the Planck mission, that has measured the Hubble Constant to be about 46,200 miles per hour per million light years (or using cosmologists’ units 67.4 km/s/Mpc).

On the other side we have new measurements of pulsating stars in local galaxies, also extremely precise, that has measured the Hubble Constant to be 50,400 miles per hour per million light years (or using cosmologists units 73.4 km/s/Mpc). These are closer to us in time.

Both these measurements claim their result is correct and very precise. The measurements’ uncertainties are only about 300 miles per hour per million light years, so it really seems like there is a significant difference in movement. Cosmologists refer to this disagreement as “tension” between the two measurements – they are both statistically pulling results in different directions, and something has to snap.

New physics?

So what’s going to snap? At the moment the jury is out. It could be that our cosmological model is wrong. What is being seen is that the universe is expanding faster nearby than we would expect based on more distant measurements. The Cosmic Microwave Background measurements don’t measure the local expansion directly, but rather infer this via a model – our cosmological model. This has been tremendously successful at predicting and describing many observational data in the universe.

So while this model could be wrong, nobody has come up with a simple convincing model that can explain this and, at the same time, explain everything else we observe. For example we could try and explain this with a new theory of gravity, but then other observations don’t fit. Or we could try and explain it with a new theory of dark matter or dark energy, but then further observations don’t fit – and so on. So if the tension is due to new physics, it must be complex and unknown.

A less exciting explanation could be that there are “unknown unknowns” in the data caused by systematic effects, and that a more careful analysis may one day reveal a subtle effect that has been overlooked. Or it could just be statistical fluke, that will go away when more data is gathered.

It is presently unclear what combination of new physics, systematic effects or new data will resolve this tension, but something has to give. The expanding muffin picture of the universe may not work anymore, and cosmologists are in a race to win a “great cosmic bake-off” to explain this result. If new physics is required to explain these new measurements, then the result will be a showstopping change of our picture of the cosmos.

Thomas Kitching, Reader in Astrophysics, UCL

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« Reply #1761 on: Today at 04:15 AM »

The Milky Way once had a large sister galaxy — but Andromeda devoured it


Billions of years ago, the Milky Way once had a huge sister galaxy, according to a surprising new study. Astronomers found that this long-lost sibling was devoured by the Andromeda galaxy, the largest galaxy in the Local Group and our closest galactic neighbor — and we’re next!

    “Astronomers have been studying the Local Group — the Milky Way, Andromeda and their companions — for so long,” study co-author Eric Bell, a professor of astronomy at the University of Michigan (UM), said in a statement. “It was shocking to realize that the Milky Way had a large sibling, and we never knew about it.”

Androdema, also known as M32, is considered to be the largest galaxy in a group of 54 galaxies, which astronomers refer to as the Local Group. However, a recent study published this year, which used a new tool to measure the galaxy, suggests that Andromeda is about the same size as the Milky Way, which is traditionally seen as the second largest in the galaxy group.

In any event, Andromeda is huge — and it didn’t reach its king-sized status by accident. Astronomers think that during its rich history, Andromeda has collided, shredded, and appropriated hundreds of smaller galaxies.

It’s almost impossible to discern what happened to each of these lost galaxies. However, Bell and colleagues were lucky — they found that a faint halo of stars in the outer reaches of Andromeda mostly got there as a result of the shredding of a single large galaxy. Simulations that backtrack the collision in time suggest that about two billion years ago Andromeda must have merged with the onetime third-biggest member of the Local Group. The timing seems right too — a team of French researchers independently determined earlier this year that Andromeda likely underwent an important merger between 1.8 billion and 3 billion years ago.

    “It was a ‘eureka’ moment. We realized we could use this information of Andromeda’s outer stellar halo to infer the properties of the largest of these shredded galaxies,” said lead author Richard D’Souza, a postdoctoral researcher at UM.

This galaxy, called M32p, which was shredded by the Andromeda galaxy, was at least 20 times larger than any galaxy which merged with the Milky Way over the course of its lifetime. M32p must have been massive, possibly once being at some point the third largest galaxy in the Local Group after the Andromeda and the Milky Way galaxies.

The devoured galaxy, called M32p, isn’t entirely gone. Instead, the astronomers think that Andromeda’s enigmatic M32 satellite galaxy is actually the surviving center of the Milky Way’s long-lost sibling — the remnants of a galactic corpse. Previously, scientists had no clue how M32, with its many contradictory features, could have surfaced. M32 is the smallest galaxy in the Messier catalog: just 6,500 light years across, with ~3 billion solar masses of material.

    “M32 is a weirdo,” Bell continued. “While it looks like a compact example of an old, elliptical galaxy, it actually has lots of young stars. It’s one of the most compact galaxies in the universe. There isn’t another galaxy like it.”

The findings will help scientists improve their basic understanding of how galaxies form and evolve. For instance, it was previously thought that huge, dramatic crashes destroy the disks of spiral galaxies, turning them into the boring elliptical variety. However, Andromeda still retains its spiral shape, showing that this assertion is no rule.

    “The Andromeda Galaxy, with a spectacular burst of star formation, would have looked so different 2 billion years ago,” Bell said. “When I was at graduate school, I was told that understanding how the Andromeda Galaxy and its satellite galaxy M32 formed would go a long way towards unraveling the mysteries of galaxy formation.”

Perhaps most importantly, the Andromeda-M32p collision will teach us what to expect from the galactic cannibal when it will have a taste of its largest meal yet — the Milky Way. The two galaxies will likely collide four billion years from now in an epic clash of the titans that will light the sky in other worlds that are far away enough from the mayhem.

The findings were reported in the journal Nature Astronomy.

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