[ad_1]
Posted on 3 Oct. 2018
"The SS 433 is an unusual star system and every year, something new has appeared," said Segev BenZvi, a physicist at the University of Rochester. "This new observation of high energy gamma rays relies on nearly 40 years of measurements of one of the strangest objects in the Milky Way. Each measurement gives us a different piece of the puzzle and we hope to use our knowledge to learn more about the quasar family as a whole. "
The night sky looks serene, but the telescopes tell us that the universe is filled with collisions and explosions. Long and violent events signal their presence by spitting light and particles in all directions. When these messengers reach Earth, scientists can use them to map the action-laden sky, helping to better understand the volatile processes taking place in the deepest space.
For the first time, an international collaboration of scientists has detected a highly energetic light coming from the outermost regions of an unusual star system in our own galaxy. The source is a microquasar – a black hole that engulfs objects from a nearby star and projects two powerful jets of material.
The very large network of the National Radio Astronomy Observatory (NRAO) has been observing such jets for many years. In some of these jets, we have seen that drops of material move at apparent speeds greater than those of light – a phenomenon called superluminal motion. The movement apparent faster than light is actually an illusion observed when a jet of material moves near the speed of light, but below it, and is directed towards the Earth.
The observations of the team, described in the October 4, 2018 issue of the journal Nature, strongly suggest that the electron acceleration and collisions at the ends of the jets of the microquasar produced powerful gamma rays. Scientists believe that studying the messengers of this microquasar can provide insight into the most extreme events occurring at the center of distant galaxies.
The team gathered data from the high-altitude gamma-ray observatory (HAWC), designed to examine the gamma-ray emission from astronomical objects such as supernova remnants, quasars and rotating dense stars called pulsars. The team has now studied one of the most well-known microquasars, SS 433 (shown at the top of the page), located about 15,000 light-years from Earth. Scientists have seen a dozen microquasars in our galaxy and only two of them seem to emit high energy gamma rays. Because of the proximity and orientation of SS 433 (below), scientists have a rare opportunity to observe extraordinary astrophysics.
The Cherenkov High Altitude Gamma Rays Observatory (HAWC) is a detector designed to examine the emission of gamma rays from astronomical objects such as supernova remnants, quasars and dense stars. rotary called pulsars. Located approximately 13,500 feet above sea level, near the Sierra Negra volcano in Mexico, the detector is comprised of more than 300 water tanks, each of about 24 feet in diameter. When particles reach the water, they produce a shock wave of blue light called Cherenkov radiation. Special cameras installed in the tanks detect this light, which allows scientists to determine the origin of incoming gamma rays. (Jordan Goodman / University of Maryland)
"The SS 433 is located in our neighborhood and, thanks to HAWC 's unique wide field of view, we have been able to solve both microquasar particle acceleration sites," said Jordan Goodman, Distinguished Professor at the. University of Maryland and lead spokesperson and US spokesperson for HAWC collaboration. "By combining our observations with multi-wavelength and multi-messenger data from other telescopes, we can improve our understanding of particle acceleration in the SS 433 and its extragalactic cousins." giants, called quasars. "
Quasars are massive black holes that suck material from the centers of galaxies, rather than feeding on a single star. They actively expel radiation, which can be seen from anywhere in the universe. But they are so far away that most known quasars have been detected because their jets are directed towards the Earth – as if a flashlight were directed directly to the eyes. In contrast, SS 433 jet aircraft are distant from the Earth and HAWC has detected light of similar energy from the microquasar side.
Regardless of their origin, gamma rays move in a straight line to their destination. Those who arrive on Earth collide with molecules in the atmosphere, creating new particles and lower energy gamma rays. Each new particle breaks into more things, creating a shower of particles as the signal moves to the ground.
HAWC, located about 13,500 feet above sea level near the Sierra Negra volcano in Mexico, is perfectly located to catch the rapidly moving particle rain. The detector is made up of more than 300 water tanks, each having a diameter of about 24 feet. When the particles reach the water, they move fast enough to produce a blue light shock wave called Cherenkov radiation. Special cameras installed in the tanks detect this light, allowing scientists to determine the origin of the gamma rays.
The HAWC collaboration examined 1,017 days of data and found that the gamma rays came from the ends of the jets of the microquasar, rather than from the central part of the star system. Based on their analysis, the researchers concluded that jet electrons reach energies about a thousand times greater than those achievable with earth-bound particle accelerators, such as the Large Hadron Collider 39, a city located along the Franco-Swiss border. The jet electrons collide with the low energy microwave background radiation that enters the space, causing gamma emission. This is a new mechanism for generating high energy gamma rays in this type of system. It is different from what scientists have observed when the jets of an object are directed towards the Earth.
Ke Fang, co-author of the study and former postdoctoral fellow of the Joint Space-Science Institute, a partnership between UMD and NASA's Goddard Space Flight Center, said that this new measure is essential for understand what is happening in the SS 433.
"Examining a single type of light from the SS 433, it's like seeing only the tail of an animal," said Fang, currently an Einstein Fellow from Stanford University. "Thus, we combine all its signals, from low-energy radio to X-rays, to new high-energy gamma-ray observations, to determine the type of beast SS 433."
Until now, the instruments had not observed the SS 433 emitting gamma rays as energetic. But HAWC is designed to be very sensitive to this extreme part of the light spectrum. The detector also has a wide field of vision that looks up at the sky all the time. The collaboration used these capabilities to solve the structural characteristics of the microquasar.
In the spring of 1994, Félix Mirabel of Saclay (France) and Luis Rodriguez of the National Autonomous University of Mexico observed an X-ray object called GRS 1915 + 105, which had just shown a radio show. This object was known to be about 40,000 light-years away, in our own Milky Way galaxy – in our own cosmic quarter. Their time series of VLA observations, visible in this image, showed that a pair of objects ejected from GRS 1915 + 105 were spreading at a seemingly superlumine speed. It was the first time that a supraluminal movement was detected in our own galaxy.
This surprising finding has shown that supermassive black holes in the center of galaxies – black holes millions of times larger than the Sun – have smaller counterparts capable of producing similar jet ejections. It is believed that GRS 1915 + 105 is a two-star system, one of whose components is a black hole or a neutron star that represents only a few times the mass of the Sun. The more massive object pulls the material from its stellar companion. The material surrounds the massive object in an accretion disk before being shot there. The friction in the accretion disk creates temperatures hot enough for the material to emit X-rays. Magnetic processes are thought to accelerate the material in the jets.
Since Mirabel and Rodriguez discovered the superluminal movement in GRS 1915 + 105, several other galactic "microquasars" have been discovered and studied with VLA and VLBA. In 1999, NRAO astronomer Robert Hjellming directed the VLA towards a bursting microquasar within 24 hours of the reported X-ray explosion. Working with X-ray observers Donald Smith and Ronald Remillard of MIT, Hellming discovered that this object is a microquasar at only 1,600 light-years away, making it the nearest black hole to Earth ever discovered .
The microquasars of our own galaxy, because they are closer and thus easier to study, have become invaluable "labs" for revealing the physical processes that produce super-fast material jets.
In the image above at the top left of the page: constant jet at the milliarcsec scale from the high mass Cyg ~ X-1 black hole Hole. Top right: transient radio jets from the supraluminal galactic reaction source GRS ~ 1915 + 105. Bottom left: radio jets from the first galactic source discovered. The binary orbit is almost peripheral; The precursor accretion disk of the SS ~ 433 forces its jets to draw a corkscrew in the sky every 162 days. Bottom right: fossil radio jets around the black hole of the galactic center in1E ~ 140,7-2942.
The Daily Galaxy via the University of Maryland and NRAO
Top 10 most viewed headlines in 2018
Southern European observatories in Chile.
"Espionage of the world's most awesome creatures" – Scientists are fishing unknown species of whales swimming under water since the Eocene
Ancient 6 to 9-billion-year-old stars in the Milky Way halo – "May Harbor Civil Civilizations"
"Point of No Return" – MIT scientist predicts horizon of events for Earth's sixth mass extinction
Artificial intelligence already exists and is billions of years old "(WATCH video)
The "ghost signals" of extraterrestrial civilizations haunt the milky way – Suggests the new Drake equation (WATCH video)
"Chances are there's never been any other civilization in the universe." One in ten billion billion "- Interview with Joe Rogan
"The mystery of the place where extraterrestrial life is hidden"
"We are entering an unexplored territory" – The exoplanet revolution could reveal that the rise of civilizations may not be unusual
"The big tear" – When matter and space-time are gradually torn apart by the expansion of the universe
"Humans are the first to arrive at the interstellar stage" – Physicist responds to Fermi paradox
[ad_2]
Source link
