Friday April 26, 2019
Home Science & Technology Ultra-High En...

Ultra-High Energy Cosmic Rays Come From Outside The Milky Way

Travelling with a speed of lights, cosmic rays are atomic nuclei. Scientist says that high energy cosmic rays coming from outer space are hitting the earth.

0
//
Cosmic rays
Source: Pixaby

New York, September 24, 2017: Researchers have found that some ultra-high energy cosmic rays that occasionally hit Earth come from a distant source outside the Milky Way.

Cosmic rays are atomic nuclei that travel through space at speeds close to that of light. Low-energy cosmic rays come from the Sun or from our own galaxy, but the origin of the highest-energy particles has been the subject of debate ever since they were first discovered fifty years ago.

Do they come from our Galaxy or from distant extragalactic objects?

The study published in the journal Science demonstrated that those cosmic rays with energies a million times greater than that of the protons accelerated in the Large Hadron Collider – the world’s largest and most powerful particle accelerator – come from much further away than from our own galaxy.

They were detected from 2004 to 2016 at the largest cosmic ray observatory ever built, the Pierre Auger Observatory in Argentina.

“We are now considerably closer to solving the mystery of where and how these extraordinary particles are created — a question of great interest to astrophysicists,” said Karl-Heinz Kampert from University of Wuppertal in Germany.

“Our observation provides compelling evidence that the sites of acceleration are outside the Milky Way,” Kampert who is spokesperson for the Auger Collaboration, which involves more than 400 scientists from 18 countries, said.

Cosmic rays are the nuclei of elements from hydrogen to iron. The highest-energy cosmic rays, those of interest in this study, only strike about once per square kilometre per year — equivalent to hitting the area of a soccer field about once per century.

Such rare particles are detectable because they create showers of secondary particles — including electrons, photons and muons – as they interact with the nuclei in the atmosphere.

These cosmic ray showers spread out, sweeping through the atmosphere at the speed of light in a disc-like structure, like a dinner plate but several kilometres in diameter.

ALSO READ: NASA’s Asteroid-chasing Spacecraft Osiris-Rex Swinging by Earth on Way to Space Rock

At the Auger Observatory, the shower particles are detected through the light they produce in several of 1,600 detectors, spread over 3,000 square kilometres of western Argentina and each containing 12 tons of water.

Tracking these arrivals tells scientists the direction from which the cosmic rays came.

After racking up detections of more than 30,000 cosmic particles, the scientists found one section of the sky was producing significantly more than its share.

The probability of this happening by a random fluctuation is extremely small, the scientists said — a chance of about two in ten million.

“This result unequivocally establishes that ultra-high energy cosmic rays are not just random wanderers of our nearby universe,” Paolo Privitera of University of Chicago who heads the US groups participating in the project, said. (IANS)

Next Story

Astronomers Measure Mass of Milky Way Galaxy

The Milky Way, the galaxy which contains Earth's solar system, is home to up to 400 billion stars and an estimated 100 billion planets.

0
Milky way galaxy, scientists
The measurement includes all the stars and planets, dust and gas, as well as the four-million-solar-mass supermassive black hole at the center. Pixabay

Using data from NASA’s Hubble Space Telescope and the European Space Agency’s Gaia satellite, astronomers have come up with one of the most accurate measurements of mass of the Milky Way galaxy.

While previous research dating back several decades provided estimates for our galaxy’s mass, ranging between 500 billion to three trillion solar masses, according to the latest measurements, Milky Way weighs about 1.5 trillion solar masses (one solar mass is the mass of our Sun).

The measurement includes all the stars and planets, dust and gas, as well as the four-million-solar-mass supermassive black hole at the center.

“We want to know the mass of the Milky Way more accurately so that we can put it into a cosmological context and compare it to simulations of galaxies in the evolving universe,” said Roeland van der Marel of the Space Telescope Science Institute (STScI) in Baltimore, Maryland.

milky way galaxy, scientists
The more massive a galaxy, the faster its globular clusters move under the pull of gravity, according to a forthcoming paper in The Astrophysical Journal. Pixabay

To weigh the galaxy, the team augmented Gaia measurements for 34 globular clusters out to 65,000 light-years, with Hubble measurements of 12 clusters out to 130,000 light-years that were obtained from images taken over a 10-year period.

They also measured the three-dimensional movement of globular star clusters – isolated spherical islands each containing hundreds of thousands of stars each that orbit the center of our galaxy.

The more massive a galaxy, the faster its globular clusters move under the pull of gravity, according to a forthcoming paper in The Astrophysical Journal.

ALSO READ: SpaceX Crew Dragon Capsule Undocks from International Space Station

The new mass estimate puts our galaxy on the beefier side, compared to other galaxies in the universe. The lightest galaxies are around a billion solar masses, while the heaviest are 30 trillion, or 30,000 times more massive.

The Milky Way, the galaxy which contains Earth’s solar system, is home to up to 400 billion stars and an estimated 100 billion planets. (IANS)