Category: astrofisica

Multi-planet System Found Through Crowdsourc…

Multi-planet System Found Through Crowdsourcing

A system of at least five exoplanets has been discovered by citizen scientists through a project called Exoplanet Explorers, part of the online platform Zooniverse, using data from NASA’s Kepler space telescope. This is the first multi-planet system discovered entirely through crowdsourcing.

Thousands of citizen scientists got to work on Kepler data in 2017 when Exoplanet Explorers launched. It was featured on a program called Stargazing Live on the Australia Broadcasting Corporation (ABC). On the final night of the three-day program, researchers announced the discovery of a four-planet system. Since then, they have named it K2-138 and determined that it has a fifth planet – and perhaps even a sixth, according to the new paper.

Another batch of 2017 Kepler data was recently uploaded to Exoplanet Explorers for citizen scientists to peer through. Astronomers have not yet searched through most of it for planets.

source: nasa.gov

images of the Sun captured during the first ye…

images of the Sun captured during the first year of NASA’s Solar Dynamics Observatory (SDO) mission.

Credit: NASA/SDO

This simulation shows a star getting torn apar…

This simulation shows a star getting torn apart by the gravitational tides of a supermassive black hole. The star gets “spaghettified” and after several orbits creates an accretion disc. Scientists believe that the superluminous ASASSN-15lh event originated in this way. The view on the right is from the side and that at the left face on.

Credit: ESO, ESA/Hubble, N. Stone, K. Hayasaki

The W. M. Keck Observatory is a two-telescop…

The W. M. Keck Observatory is a two-telescope astronomical observatory at an elevation of 4,145 meters (13,600 ft) near the summit of Mauna Kea in the U.S. state of Hawaii. Both telescopes feature 10 m (33 ft) primary mirrors, currently among the largest astronomical telescopes in use.

images: Keck ObservatorySarah ElliottVadim Kurland 

Black holes

A black hole is a region of spacetime exhibiting such strong gravitational effects that nothing—not even particles and electromagnetic radiation such as light—can escape from inside it. The theory of general relativity predicts that a sufficiently compact mass can deform spacetime to form a black hole. The boundary of the region from which no escape is possible is called the event horizon. Although the event horizon has an enormous effect on the fate and circumstances of an object crossing it, no locally detectable features appear to be observed. In many ways a black hole acts like an ideal black body, as it reflects no light.  

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The idea of a body so massive that even light could not escape was briefly proposed by astronomical pioneer and English clergyman John Michell in a letter published in November 1784. Michell’s simplistic calculations assumed that such a body might have the same density as the Sun, and concluded that such a body would form when a star’s diameter exceeds the Sun’s by a factor of 500, and the surface escape velocity exceeds the usual speed of light.

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At the center of a black hole, as described by general relativity, lies a gravitational singularity, a region where the spacetime curvature becomes infinite. For a non-rotating black hole, this region takes the shape of a single point and for a rotating black hole, it is smeared out to form a ring singularity that lies in the plane of rotation. In both cases, the singular region has zero volume. It can also be shown that the singular region contains all the mass of the black hole solution. The singular region can thus be thought of as having infinite density. 

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How Do Black Holes Form?

Scientists think the smallest black holes formed when the universe began.

Stellar black holes are made when the center of a very big star falls in upon itself, or collapses. When this happens, it causes a supernova. A supernova is an exploding star that blasts part of the star into space.

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Scientists think supermassive black holes were made at the same time as the galaxy they are in.

Supermassive black holes, which can have a mass equivalent to billions of suns, likely exist in the centers of most galaxies, including our own galaxy, the Milky Way. We don’t know exactly how supermassive black holes form, but it’s likely that they’re a byproduct of galaxy formation. Because of their location in the centers of galaxies, close to many tightly packed stars and gas clouds, supermassive black holes continue to grow on a steady diet of matter.

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If Black Holes Are “Black,” How Do Scientists Know They Are There?

A black hole can not be seen because strong gravity pulls all of the light into the middle of the black hole. But scientists can see how the strong gravity affects the stars and gas around the black hole. 

Scientists can study stars to find out if they are flying around, or orbiting, a black hole.

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When a black hole and a star are close together, high-energy light is made. This kind of light can not be seen with human eyes. Scientists use satellites and telescopes in space to see the high-energy light.

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On 11 February 2016, the LIGO collaboration announced the first observation of gravitational waves; because these waves were generated from a black hole merger it was the first ever direct detection of a binary black hole merger. On 15 June 2016, a second detection of a gravitational wave event from colliding black holes was announced. 

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Simulation of gravitational lensing by a black hole, which distorts the image of a galaxy in the background 

Animated simulation of gravitational lensing caused by a black hole going past a background galaxy. A secondary image of the galaxy can be seen within the black hole Einstein ring on the opposite direction of that of the galaxy. The secondary image grows (remaining within the Einstein ring) as the primary image approaches the black hole. The surface brightness of the two images remains constant, but their angular size varies, hence producing an amplification of the galaxy luminosity as seen from a distant observer. The maximum amplification occurs when the background galaxy (or in the present case a bright part of it) is exactly behind the black hole.

Could a Black Hole Destroy Earth?

Black holes do not go around in space eating stars, moons and planets. Earth will not fall into a black hole because no black hole is close enough to the solar system for Earth to do that.

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Even if a black hole the same mass as the sun were to take the place of the sun, Earth still would not fall in. The black hole would have the same gravity as the sun. Earth and the other planets would orbit the black hole as they orbit the sun now.

The sun will never turn into a black hole. The sun is not a big enough star to make a black hole.

Do you have any fun facts about magnetars?

Do you have any fun facts about magnetars?

  • A magnetar is a type of neutron star with an extremely powerful magnetic field. 
  • The theory regarding these objects was proposed by Robert Duncan and Christopher Thompson in 1992, but the first recorded burst of gamma rays thought to have been from a magnetar had been detected on March 5, 1979. During the following decade, the magnetar hypothesis became widely accepted as a likely explanation for soft gamma repeaters (SGRs) and anomalous X-ray pulsars (AXPs).

  • The magnetic field decay powers the emission of high-energyelectromagnetic radiation, particularly X-rays and gamma rays.

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  • Like other neutron stars, magnetars are around 20 kilometres (12 mi) in diameter and have a mass 2–3 times that of the Sun. 

  • Magnetars are differentiated from other neutron stars by having even stronger magnetic fields, and rotating comparatively slowly, with most magnetars completing a rotation once every one to ten seconds, compared to less than one second for a typical neutron star. This magnetic field gives rise to very strong and characteristic bursts of X-rays and gamma rays.

    The active life of a magnetar is short. Their strong magnetic fields decay after about 10,000 years, after which activity and strong X-ray emission cease. Given the number of magnetars observable today, one estimate puts the number of inactive magnetars in the Milky Way at 30 million or more.

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  • Magnetars are characterized by their extremely powerful magnetic fields of 108 to 1011 tesla. These magnetic fields are hundreds of millions of times stronger than any man-made magnet, and quadrillions of times more powerful than the field surrounding Earth. Earth has a geomagnetic field of 30–60 microteslas, and a neodymium-based, rare-earth magnet has a field of about 1.25 tesla, with a magnetic energy density of 4.0×105 J/m3. A magnetar’s 1010 tesla field, by contrast, has an energy density of 4.0×1025 J/m3, with an E/c2 mass density >104 times that of lead. The magnetic field of a magnetar would be lethal even at a distance of 1000 km due to the strong magnetic field distorting the electron clouds of the subject’s constituent atoms, rendering the chemistry of life impossible. At a distance of halfway from Earth to the moon, a magnetar could strip information from the magnetic stripes of all credit cards on Earth. As of 2010, they are the most powerful magnetic objects detected throughout the universe.

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As of March 2016, 23 magnetars are known, with six more candidates awaiting confirmation.

Images:

ESA/ATG medialab

A pulsar is a rapidly spinning and highly magn…

A pulsar is a rapidly spinning and highly magnetized neutron star, the crushed core left behind when a massive sun explodes. Most were found through their pulses at radio wavelengths, which are thought to be caused by narrow, lighthouse-like beams emanating from the star’s magnetic poles.

When it comes to gamma-rays, pulsars are no longer lighthouses. A new class of gamma-ray-only pulsars shows that the gamma rays must form in a broader region than the lighthouse-like radio beam. Astronomers now believe the pulsed gamma rays arise far above the neutron star.

Credits:

Meteor shower Geminid above the radio telescop…

Meteor shower Geminid above the radio telescope MUSER

Image Credit: Yin Hao apod

China’s FAST identifies 3 new pulsars …

China’s FAST identifies 3 new pulsars

The China-based FAST, the world’s largest single-dish radio telescope, has discovered three new pulsars, the National Astronomical Observatories of China (NAOC) said Tuesday.

So far, FAST has identified a total of nine pulsars since its trial operations began in September 2016.

According to Zhang Shuxin, deputy chief of the NAOC’s Guizhou branch, the discovery of more pulsars will be common for FAST in the future.

Li Di, chief scientist of the NAOC radio astronomy division, in an earlier interview predicted that when FAST starts formal operations in 2019, it will find more than 100 pulsars each year.

Pulsar observation is very important as it can be used to confirm the existence of gravitational radiation and black holes and help solve many other major questions in physics.

Located in a naturally deep and round karst depression in southwest China’s Guizhou Province, FAST stands for Five-hundred-meter Aperture Spherical Radio Telescope. It has a receiving area equivalent to about 30 football fields.

FAST’s key tasks include observation of pulsars as well as exploration of interstellar molecules and interstellar communication signals.

X-ray binary (black hole devouring a star) X-…

X-ray binary (black hole devouring a star)

X-ray binaries are a class of binary stars that are luminous in X-rays. The X-rays are produced by matter falling from one component, called the donor (usually a relatively normal star), to the other component, called the accretor, which is very compact: a neutron star or black hole. The infalling matter releases gravitational potential energy, up to several tenths of its rest mass, as X-rays. (Hydrogen fusion releases only about 0.7 percent of rest mass.) The lifetime and the mass-transfer rate in an X-ray binary depends on the evolutionary status of the donor star, the mass ratio between the stellar components, and their orbital separation.

An estimated 1041 positrons escape per second from a typical low-mass X-ray binary.