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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.


Post 8878

What is palm oil?


Post 8877

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.


Post 8876

Monstrous ‘murder hornets’ have reached the US