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Very Large Telescope: Powerful Eyes on the Sky

 

In 2004, a team of European and American astronomers studying the TW Hydrae Association, a group of very young stars and other objects, spotted a red speck of light near one of the association’s brown dwarfs. The object was more than 100 times fainter than its parent star. Further observations confirmed that it was an exoplanet orbiting its star at 55 times the Earth-sun distance.

“Our new images show convincingly that this really is a planet, the first planet that has ever been imaged outside of our solar system,” ESO astronomer Gael Chauvin said in a statement.

In 2008, a team of scientists used the VLT to discover and image an object near the star Beta Pictoris. Most directly imaged exoplanets lie far from their stars, past where Neptune would orbit, where stellar light is dimmer. In contrast, the planet Beta Pictoris b lies much closer, where Saturn would orbit.

“Direct imaging of extrasolar planets is necessary to test the various models of formation and evolution of planetary systems,” researcher Daniel Rouan said in a statement. “But such observations are only beginning. Limited today to giant planets around young stars, they will in the future extend to the detection of cooler and older planets, with the forthcoming instruments on the VLT and on the next generation of optical telescopes.”

Spin class

Researchers also used the VLT to determine how fast Beta Pictoris b is spinning, clocking the massive planet almost 62,000 mph (100,000 km/h) at its equator. In comparison, Earth’s equator spins at only 1,056 mph (1,700 km/h), while Jupiter travels at about 29,000 mph (47,000 km/h). This was the first time an exoplanet’s rotation rate had been determined.

ESO/Stéphane Guisard

The sky appears to rotate above ESO’s Very Large Telescope in this long exposure. The star trails curve away from the celestial equator in the middle of the photo, where the stars seem to move in a straight line.

“It is not known why some planets spin fast and others more slowly,” researcher Remco de Kok said in a statement. “But this first measurement of an exoplanet’s rotation shows that the trend seen in the solar system, where the more massive planets spin faster, also holds true for exoplanets. This must be some universal consequence of the way planets form.”

The private organization Breakthrough Initiatives has enlisted the help of the VLT to hunt for planets around Earth’s closest star, Proxima Centauri. After helping to fund an upgrade to an existing instrument on the VLT, Breakthrough Initiatives will receive time for a “careful search” of the Proxima Centauri system for new planets. The improvement in the VLT Imager and Spectrometer for Mid Infrared instrument will equip it with a coronagraph, which blocks much of the light from a star, as well as an adaptive optics system to correct for distortions in starlight caused by Earth’s atmosphere. The upgrade is scheduled to be completed in 2019.


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In his famous 1687 treatise “Philosophiae naturalis principia mathematica,” Newton described what is now called his law of universal gravitation. It is usually written as:

Fg = G (m1 ∙ m2) / r2

Where F is the force of gravity, m1 and m2 are the masses of two objects and r is the distance between them. G, the gravitational constant, is a fundamental constant whose value has to be discovered through experiment.

Newton’s Law of Universal Gravitation says that the force of gravity is directly proportional to the product of their masses and inversely proportional to the square of the distance between them.  (Image credit: marekuliasz Shutterstock)

Gravity is powerful, but not that powerful

Gravity is the weakest of the fundamental forces. A bar magnet will electromagnetically pull a paper clip upward, overcoming the gravitational force of the entire Earth on the piece of office equipment. Physicists have calculated that gravity is 10^40 (that’s the number 1 followed by 40 zeros) times weaker than electromagnetism, according to PBS’s Nova.

While gravity’s effects can clearly be seen on the scale of things like planets, stars and galaxies, the force of gravity between everyday objects is extremely difficult to measure. In 1798, British physicist Henry Cavendish conducted one of the world’s first high precision experiments to try to precisely determine the value of G, the gravitational constant, as reported in the Proceedings of the National Academy of Science’s Front Matter.

Cavendish built what’s known as a torsion balance, attaching two small lead balls to the ends of a beam suspended horizontally by a thin wire. Near each of the small balls, he placed a large, spherical lead weight. The small lead balls were gravitationally attracted to the heavy lead weights, causing the wire to twist just a tiny bit and allowing him to calculate G.

Remarkably, Cavendish’s estimation for G was only 1% off from its modern-day accepted value of 6.674 × 10^−11 m^3/kg^1 * s^2. Most other universal constants are known to far higher precision but because gravity is so weak, scientists must design incredibly sensitive equipment to try to measure its effects. Thus far, a more precise value of G has eluded their instrumentation.

The German-American physicist Albert Einstein brought about the next revolution in our understanding of gravity. His theory of general relativity showed that gravity arises from the curvature of space-time, meaning that even rays of light, which must follow this curvature, are  bent by extremely massive objects.

Einstein’s theories were used to speculate about the existence of black holes — celestial entities with so much mass that not even light can escape from their surfaces. In the vicinity of a black hole, Newton’s law of universal gravitation no longer accurately describes how objects move, but rather Einstein’s tensor field equations take precedence.

Astronomers have since discovered real-life black holes out in space, even managing to snap a detailed photo of the colossal one that lives at the center of our galaxy. Other telescopes have seen black holes’ effects all over the universe.

The application of Newton’s gravitational law to extremely light objects, like people, cells and atoms, remains a bit of an unstudied frontier, according to Minute Physics. Researchers assume that such entities attract one another using the same gravitational rules as planets and stars, but because gravity is so weak, it is difficult to know for sure.

Perhaps, atoms attract one another gravitationally at a rate of one over their distance cubed instead of squared — our current instruments have no way of telling. Novel hidden aspects of reality might be accessible if only we could measure such minute gravitational forces.

A perpetual force of mystery

Gravity perplexes scientists in other ways, too. The Standard Model of particle physics, which describes the actions of almost all known particles and forces, leaves out gravity. While light is carried by a particle called a photon, physicists have no idea if there is an equivalent particle for gravity, which would be called a graviton.

Bringing gravity together in a theoretical framework with quantum mechanics, the other major discovery of the 20th-century physics community, remains an unfinished task. Such a theory of everything, as it’s known, might never be realized.

But gravity has still been used to uncover monumental findings. In the 1960s and 70s, astronomers Vera Rubin and Kent Ford showed that stars at the edges of galaxies were orbiting faster than should be possible. It was almost as if some unseen mass was tugging on them gravitationally, bringing to light a material that we now call dark matter.

In recent years, scientists have also managed to capture another consequence of Einstein’s relativity — gravitational waves emitted when massive objects like neutron stars and black holes rotate around one another. Since 2017, the Laser Interferometer Gravitational-Wave Observatory (LIGO) has opened up a new window to the universe by detecting the exceedingly faint signal of such events.

‘Dancing’ star’s weird, spirograph orbit proves Einstein right (again)


 

 

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‘Dancing’ star’s weird, spirograph orbit proves Einstein right (again)

The 12 Strangest Objects in the Universe


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The 12 Strangest Objects in the Universe

A Moon with a Moon

moon triptych

(Image credit: NASA/JPL/Space Science Institute)

What’s better than a moon? A moon orbiting a moon, which the internet has dubbed a moonmoon. Also known as submoons, moonitos, grandmoons, moonettes and moooons, moonmoons are still only theoretical, but recent calculations suggest that there’s nothing impossible about their formation. Perhaps astronomers may one day discover one.

Dark-Matter-Less Galaxy?

ngc1052-df2

(Image credit: NASA, ESA, and P. van Dokkum (Yale University))

Dark matter — the unknown substance comprising 85 percent of all matter in the universe — is strange. But researchers are at least sure about one thing: Dark matter is everywhere. So team members were scratching their heads over a peculiar galaxy they spotted in March 2018 that seemed to contain hardly any dark matter. Subsequent work suggested that the celestial oddity did in fact contain dark matter, though the finding paradoxically lent credence to an alternative theory positing that dark matter doesn’t exist at all. Get it together, astronomers!

The Most Bizarre Star

Artist's Illustration of Tabby's Star2852

(Image credit: NASA/JPL-Caltech)

When astronomer Tabetha Boyajian of Louisiana State University and her colleagues first saw the star known as KIC 846285, they were flummoxed. Nicknamed Tabby’s star, the object would dip in brightness at irregular intervals and for odd lengths of time, sometimes by as much as 22 percent. Different theories were invoked, including the possibility of an alien megastructure, but nowadays, most researchers believe the star to be surrounded by an abnormal ring of dust that’s causing the darkening.

Highly Electric Hyperion

Cassini image of Saturn.

(Image credit: NASA/JPL-Caltech/Space Science Institute)

The title of weirdest moon in the solar system could go to many celestial objects — Jupiter’s overly volcanic Io, Neptune’s geyser-spewing Triton. But one of the strangest looking is Saturn’s Hyperion, a pumice-stone-like irregular rock pockmarked with numerous craters. NASA’s Cassini spacecraft, which visited the Saturn system between 2004 and 2017, also found that Hyperion was charged with a “particle beam” of static electricity flowing out into space.

A Guiding Neutrino

An artist's illustration shows the supermassive black hole at the center of a blazar galaxy emitting its stream of energetic particles toward Earth.

(Image credit: DESY, Science Communication Lab)

The single, high-energy neutrino that struck Earth on Sept. 22, 2017, wasn’t, on its own, all that extraordinary. Physicists at the IceCube Neutrino Observatory in Antarctica see neutrinos of similar energy levels at least once a month. But this one was special because it was the first to arrive with enough information about its origin for astronomers to point telescopes in the direction it came from. They figured out that it had been flung at Earth 4 billion years ago by a flaring blazar, a supermassive black hole at the center of a galaxy that had been consuming surrounding material.

The Living Fossil Galaxy

DGSAT I (left) is an ultra-diffuse galaxy that doesn’t have a lot of stars like normal spiral galaxies (right).

(Image credit: A. Romanowsky/UCO/D. Martinez-Delgado/ARI)

DGSAT I is an ultradiffuse galaxy (UDG), meaning it is as big as a galaxy like the Milky Way but its stars are spread out so thinly that it is nearly invisible. But when scientists saw the ghostly DGSAT 1 in 2016, they noticed that it was sitting all alone, quite unlike other UDGs, which are typically found in clusters. Its characteristics suggest that the faint object formed during a very different era in the universe, back just 1 billion or so years after the Big Bang, making DGSAT 1 a living fossil.

Double Quasar Image

quasars

(Image credit: NASA Hubble Space Telescope, Tommaso Treu/UCLA, and Birrer et al)

Massive objects curve light, enough so that they can distort the image of things behind them. When researchers used the Hubble Space Telescope to spot a quasar from the early universe, they used it to estimate the universe’s expansion rate and found that it is expanding faster today than it was back then — a finding that disagrees with other measurements. Now physicists need to figure out if their theories are wrong or if something else strange is going on.

Infrared Stream from Space

(Image credit: ESA/N. Tr’Ehnl (Pennsylvania State University)/NASA)

Neutron stars are extremely dense objects formed after the death of a regular star. Normally, they emit radio waves or higher-energy radiation such as X-rays, but in September 2018, astronomers found a long stream of infrared light coming from a neutron star 800 light-years away from Earth — something never before observed. The researchers proposed that a disk of dust surrounding the neutron star could be generating the signal, but the ultimate explanation has yet to be found.

Rogue Planet with Auroras

Newly described brown dwarf

(Image credit: Chuck Carter; NRAO/AUI/NSF/Caltech)

Drifting through the galaxy are rogue planets, which have been flung away from their parent star by gravitational forces. One particular peculiarity in this class is known as SIMP J01365663+0933473, a planet-size object 200 light-years away whose magnetic field is more than 200 times stronger than Jupiter’s. This is strong enough to generate flashing auroras in its atmosphere, which can be seen with radio telescopes.

 

This is the most violent object in the solar system


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This is the most violent object in the solar system

The Universe May Be Flooded with a Cobweb Network of Invisible Strings


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The Universe May Be Flooded with a Cobweb Network of Invisible Strings

By Paul Sutter – Astrophysicist January 02, 2020

We may soon find out whether we live in an axiverse.

an abstract image of axion strings

(Image: © Shutterstock)

What if I told you that our universe was flooded with hundreds of kinds of nearly invisible particles and that, long ago, these particles formed a network of universe-spanning strings?

It sounds both trippy and awesome, but it’s actually a prediction of string theory, our best (but frustratingly incomplete) attempt at a theory of everything. These bizarre, albeit hypothetical, little particles are known as axions, and if they can be found, that would mean we all live in a vast “axiverse.”

The best part of this theory is that it’s not just some physicist’s armchair hypothesis, with no possibility of testing. This incomprehensibly huge network of strings may be detectable in the near future with microwave telescopes that are actually being built.

Related: The Biggest Unsolved Mysteries in Physics

If found, the axiverse would give us a major step up in figuring out the puzzle of … well, all of physics.

A symphony of strings

OK, let’s get down to business. First, we need to get to know the axion a little better. The axion, named by physicist (and, later, Nobel laureate) Frank Wilczek in 1978, gets its name because it’s hypothesized to exist from a certain kind of symmetry-breaking. I know, I know — more jargon. Hold on. Physicists love symmetries — when certain patterns appear in mathematics.

There’s one kind of symmetry, called the CP symmetry, that says that matter and antimatter should behave the same when their coordinates are reversed. But this symmetry doesn’t seem to fit naturally into the theory of the strong nuclear force. One solution to this puzzle is to introduce another symmetry in the universe that “corrects” for this misbehavior. However, this new symmetry only appears at extremely high energies. At everyday low energies, this symmetry disappears, and to account for that, and out pops a new particle — the axion.

Now, we need to turn to string theory, which is our attempt (and has been our main attempt for 50-odd years now) to unify all of the forces of nature, especially gravity, in a single theoretical framework. It’s proven to be an especially thorny problem to solve, due to a variety of factors, not the least of which is that, for string theory to work (in other words, for the mathematics to even have a hope of working out), our universe must have more than the usual three dimensions of space and one of time; there have to be extra spatial dimensions.

These spatial dimensions aren’t visible to the naked eye, of course; otherwise, we would’ve noticed that sort of thing. So the extra dimensions have to be teensy-tiny and curled up on themselves at scales so small that they evade normal efforts to spot them.

What makes this hard is that we’re not exactly sure how these extra dimensions curl up on themselves, and there’s somewhere around 10^200 possible ways to do it.

But what these dimensional arrangements appear to have in common is the existence of axions, which, in string theory, are particles that wind themselves around some of the curled-up dimensions and get stuck.

What’s more, string theory doesn’t predict just one axion but potentially hundreds of different kinds, at a variety of masses, including the axion that might appear in the theoretical predictions of the strong nuclear force.

Silly strings

So, we have lots of new kinds of particles with all sorts of masses. Great! Could axions make up dark matter, which seems to be responsible for giving galaxies most of their mass but can’t be detected by ordinary telescopes? Perhaps; it’s an open question. But axions-as-dark-matter have to face some challenging observational tests, so some researchers instead focus on the lighter end of the axion families, exploring ways to find them.

And when those researchers start digging into the predicted behavior of these featherweight axions in the early universe, they find something truly remarkable. In the earliest moments of the history of our cosmos, the universe went through phase transitions, changing its entire character from exotic, high-energy states to regular low-energy states.

During one of these phase transitions (which happened when the universe was less than a second old), the axions of string theory didn’t appear as particles. Instead, they looked like loops and lines — a network of lightweight, nearly invisible strings crisscrossing the cosmos.

This hypothetical axiverse, filled with a variety of lightweight axion strings, is predicted by no other theory of physics but string theory. So, if we determine that we live in an axiverse, it would be a major boon for string theory.

A shift in the light

How can we search for these axion strings? Models predict that axion strings have very low mass, so light won’t bump into an axion and bend, or axions likely wouldn’t mingle with other particles. There could be millions of axion strings floating through the Milky Way right now, and we wouldn’t see them.

But the universe is old and big, and we can use that to our advantage, especially once we recognize that the universe is also backlit.

The cosmic microwave background (CMB) is the oldest light in the universe, emitted when it was just a baby — about 380,000 years old. This light has soaked the universe for all these billions of years, filtering through the cosmos until it finally hits something, like our microwave telescopes.

So, when we look at the CMB, we see it through billions of light-years’ worth of universe. It’s like looking at a flashlight”s glow through a series of cobwebs: If there is a network of axion strings threaded through the cosmos, we could potentially spot them.

In a recent study, published in the arXiv database on Dec. 5, a trio of researchers calculated the effect an axiverse would have on CMB light. They found that, depending on how a bit of light passes near a particular axion string, the polarization of that light could shift. That’s because the CMB light (and all light) is made of waves of electric and magnetic fields, and the polarization of light tells us how the electric fields are oriented — something that changes when the CMB light encounters an axion. We can measure the polarization of the CMB light by passing the signal through specialized filters, allowing us to pick out this effect.

The researchers found that the total effect on the CMB from a universe full of strings introduced a shift in polarization amounting to around 1%, which is right on the verge of what we can detect today. But future CMB mappers, such as the Cosmic Origins Explorer, Lite (Light) satellite for the studies of B-mode polarization and Inflation from cosmic background Radiation Detection (LiteBIRD), and the Primordial Inflation Explorer (PIXIE) , are currently being designed. These futuristic telescopes would be capable of sniffing out an axiverse. And once those mappers come online, we’ll either find that we live in an axiverse or rule out this particular prediction of string theory.

Either way, there’s a lot to untangle.

Paul M. Sutter is an astrophysicist at The Ohio State University, host of Ask a Spaceman and Space Radio, and author of Your Place in the Universe.

Originally published on Live Science.

China’s Lunar Rover Just Found Something Weird on the Far Side of the Moon


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China’s Lunar Rover Just Found Something Weird on the Far Side of the Moon

By Andrew Jones September 03, 2019

Tracks made by Yutu-2 while navigating hazards during lunar day 8, which occurred during late July and early August 2019.

Tracks made by Yutu-2 while navigating hazards during lunar day 8, which occurred during late July and early August 2019.
(Image: © China Lunar Exploration Project)

China’s Chang’e-4 lunar rover has discovered an unusually colored, ‘gel-like’ substance during its exploration activities on the far side of the moon.

The mission’s rover, Yutu-2, stumbled on that surprise during lunar day 8. The discovery prompted scientists on the mission to postpone other driving plans for the rover, and instead focus its instruments on trying to figure out what the strange material is.

Day 8 started on July 25; Yutu-2 began navigating a path through an area littered with various small impact craters, with the help and planning of drivers at the Beijing Aerospace Control Center, according to a Yutu-2 ‘drive diary’ published on Aug. 17 by the government-sanctioned Chinese-language publication Our Space, which focuses on space and science communication.

Related: Chang’e 4 in Pictures: China’s Mission to the Moon’s Far Side

The drive team, excited by the discovery, called in their lunar scientists. Together, the teams decided to postpone Yutu-2’s plans to continue west and instead ordered the rover to check out the strange material.

Yutu-2 found a strangely-colored substance in a crater on the far side of the moon.

Yutu-2 found a strangely-colored substance in a crater on the far side of the moon. (Image credit: China Lunar Exploration Project)

With the help of obstacle-avoidance cameras, Yutu-2 carefully approached the crater and then targeted the unusually colored material and its surroundings. The rover examined both areas with its Visible and Near-Infrared Spectrometer (VNIS), which detects light that is scattered or reflected off materials to reveal their makeup.

VNIS is the same instrument that detected tantalizing evidence of material originating from the lunar mantle in the regolith of Von Kármán crater, a discovery Chinese scientists announced in May.

Tracks showing Yutu-2's approach to the crater for analysis of the gel-like substance.

Tracks showing Yutu-2’s approach to the crater for analysis of the gel-like substance. (Image credit: China Lunar Exploration Project)

So far, mission scientists haven’t offered any indication as to the nature of the colored substance and have said only that it is “gel-like” and has an “unusual color.” One possible explanation, outside researchers suggested, is that the substance is melt glass created from meteorites striking the surface of the moon.

Yutu-2’s discovery isn’t scientists’ first lunar surprise, however. Apollo 17 astronaut and geologist Harrison Schmitt discovered orange-colored soil near the mission’s Taurus-Littrow landing site in 1972, prompting excitement from both Schmitt and his moonwalk colleague, Gene Cernan. Lunar geologists eventually concluded that the orange soil was created during an explosive volcanic eruption 3.64 billion years ago.

Strange orange soil was discovered on the moon by the Apollo 17 mission in 1972.

Strange orange soil was discovered on the moon by the Apollo 17 mission in 1972. (Image credit: China Lunar Exploration Project)

Chang’e-4 launched in early December 2018, and made the first-ever soft landing on the far side of the moon on Jan. 3. The Yutu-2 rover had covered a total of 890 feet (271 meters) by the end of lunar day 8.

Watch: China’s Historic Moon Landing Captured by Probe’s Camera

A stitched image from Yutu-2 looking back toward the Chang'e-4 lander during lunar day 7, in late June and early July 2019.

A stitched image from Yutu-2 looking back toward the Chang’e-4 lander during lunar day 7, in late June and early July 2019. (Image credit: China Lunar Exploration Project)

The Chang’e-4 lander and Yutu-2 rover powered down for the end of lunar day 8 on Aug. 7, and began their ninth lunar day over the weekend. The Yutu-2 rover woke up at 8:42 p.m. EDT on Aug. 23 (00:42 GMT Aug. 24), and the lander followed the next day, at 8:10 p.m. (00:10 GMT).

During lunar day 9, Yutu-2 will continue its journey west, take a precautionary six-day nap around local noontime, and power down for a ninth lunar night around Sept. 5, about 24 hours hours ahead of local sunset.

Follow Andrew Jones at @AJ_FI. Follow us on Twitter @Spacedotcom and on Facebook