Sunday, 24 March 2019

A small solar storm is heading toward Earth, but don't expect a big light show.


March 22, 2019 by The Associated Press

X-rays stream off the sun in this image showing observations from by NASA's Nuclear Spectroscopic Telescope Array, or NuSTAR, overlaid on a picture taken by NASA's Solar Dynamics Observatory (SDO). Credit: NASA
Space weather forecaster Jonathan Lash says a  that left the sun this week is due to arrive at Earth around 2 p.m. EDT Saturday.
The National Oceanic and Atmospheric Administration scientist says the flare is too weak and any light show would be limited to Alaska, Canada, Iceland, Norway and other far northern spots.
Lash says the event is unusual but not rare. That's because it is happening during the quiet four-year solar minimum. It's unlikely to cause power or  on Earth, nor will many people get a chance to see shimmering auroras.
credits: phys.org

Wednesday, 20 March 2019

83 supermassive black holes discovered in early universe

These findings, published in The Astrophysical Journal, increases the number of black holes known at that epoch considerably.

Published: 19th March 2019 12:30 PM
Image result for blackhole
credits:wireduk



WASHINGTON: Astronomers have discovered 83 quasars powered by supermassive black holes 13 billion light-years away from the Earth, from a time when the universe was less than 10 per cent of its present age.
"It is remarkable that such massive dense objects were able to form so soon after the Big Bang," said Michael Strauss, a professor at Princeton University in the US.
"Understanding how black holes can form in the early universe, and just how common they are, is a challenge for our cosmological models," Strauss said in a statement.
These findings, published in The Astrophysical Journal, increases the number of black holes known at that epoch considerably, and reveals, for the first time, how common they are early in the universe's history.

In addition, it provides new insight into the effect of black holes on the physical state of gas in the early universe in its first billion years.
Supermassive black holes, found at the centres of galaxies, can be millions or even billions of times more massive than the Sun.
While they are prevalent today, it is unclear when they first formed, and how many existed in the distant early universe.
A supermassive black hole becomes visible when gas accretes onto it, causing it to shine as a "quasar."
Previous studies have been sensitive only to the very rare, most luminous quasars, and thus the most massive black holes.
The new discoveries probe the population of fainter quasars, powered by black holes with masses comparable to most black holes seen in the present-day universe.
The team used data taken with "Hyper Suprime-Cam" (HSC) instrument, mounted on the Subaru Telescope of the National Astronomical Observatory of Japan, which is located on the summit of Maunakea in Hawaii.
The researchers selected distant quasar candidates from the sensitive HSC survey data.
They then carried out an intensive observational campaign to obtain spectra of those candidates, using three telescopes: the Subaru Telescope; the Gran Telescopio Canarias on the island of La Palma in the Canaries, Spain; and the Gemini South Telescope in Chile.
The survey revealed 83 previously unknown very distant quasars.
Together with 17 quasars already known in the survey region, the researchers found that there is roughly one supermassive black hole per cubic giga-light-year.
The sample of quasars in this study are about 13 billion light-years away from the Earth.
In other words, we are seeing them as they existed 13 billion years ago.
As the Big Bang took place 13.8 billion years ago, we are effectively looking back in time, seeing these quasars and supermassive black holes as they appeared only about 800 million years after the creation of the universe.

source:newindianexpress

Sunday, 17 March 2019

Mercury, not Venus, is the closest planet to Earth

Which planet is closest to the Earth? The answer is not Venus.
Until now, we have read in our science books or even if searching on Google, the answer suggests that Venus is the closest neighbor to Earth. But, now, scientists have made some shocking revelations suggesting that Mercury is indeed the closest planet to the Earth.
Presenting their outcomes in magazine Physics today, scientists from NASA, Los Alamos National Lab, and the U.S. Army, proposed a new model of the planets’ orbit shuffles things around, calculating that Earth’s closest neighbor, on average, is actually Mercury. In fact, it says that every other planet in the solar system’s nearest neighbor is Mercury as well.
Normally, we calculate the average distance from the planet to the Sun. The Earth’s average distance is 1 astronomical unit (AU), while Venus’ is around 0.72 AU. If you subtract one from the other, you calculate the average distance from Earth to Venus as 0.28 AU, the smallest distance for any pair of planets.
But a trio of scientists realized that this isn’t an accurate way to calculate the distances to planets. After all, Earth spends just as much time on the opposite side of its orbit from Venus, placing it 1.72 AU away. One must instead average the distance between every point along one planet’s orbit and every point along the other planet’s orbit.
The scientists ran a simulation based on two assumptions:
  1. the planets’ orbits were approximately circular.
  2. their orbits weren’t at an angle relative to one another.
In the commentary, the researchers devised a new mathematical technique, called the point-circle method, to measure the distances between planets. This method averages the distance between a bunch of points on each planet’s orbit, thereby taking time into consideration.
A simulation of an Earth year’s worth of orbits by the terrestrial planets begins to reveal that Mercury (gray in orbital animation) has the smallest average distance from Earth (blue) and is most frequently Earth’s nearest neighbor. A longer run of the simulation can be seen on YouTube. In addition, planetary geoscientist David Rothery ran a solar system simulation for the BBC radio program More or Less and came up with similar results.
When measured that way, Mercury was closest to Earth most of the time. Not only that, but Mercury was also the closest planet to Saturn, and Neptune, and all of the other planets. The researchers checked their findings by mapping out where the planets were in their orbits every 24 hours for 10,000 years.
Steven Beckwith, the director of the Space Science Laboratory and professor of astronomy at UC Berkeley, who was not part of the commentary said, “Suppose you live in a house where the people who live next door to you spend half the year someplace, maybe you live in Wisconsin and your nearest neighbors spend seven months of the long winters in Florida. During the winter, the people in the next house over would be closer to you.”

Tuesday, 12 March 2019

Indian scientists discover new way of powering radio sources in universe

This discovery, according to the team, could open up avenues for further studies regarding an alternate theory suggesting radio sources to be powered outside the power law.


universe, radio waves, astronomers, radio galaxies, radio frequencies, emissions, cambridge university, pune news, indian express news
Radio galaxies are a small subset of galaxies that emit exceptionally powerful emissions at radio frequencies.

In a first, a team of Indian astronomers has discovered some sources in the universe capable of emitting radio waves in a never-before-known mechanism, using the Giant Metrewave Radio Telescope (GMRT) located at Khodad in Junnar, about 80 km from Pune.
The team, led by TIFR-National Centre for Radio Astronomy (NCRA), which operates the GMRT, said they found a rare source named ‘Extremely Inverted Spectrum Extragalactic Radio Sources’. This discovery, according to the team, could open up avenues for further studies regarding an alternate theory suggesting radio sources to be powered outside the power law.
“In case of special cluster sources, the magnetic flux drops to low frequencies and capturing this sudden fall is extremely challenging. This was possible only due to the high sensitivity of the GMRT and its low range feature. We took accurate measurements as such emissions were captured at frequencies around 150 MHz (megahertz),” senior NCRA scientist Ishwar Chandra told The Indian Express.
Radio galaxies are a small subset of galaxies that emit exceptionally powerful emissions at radio frequencies. Up until now, astronomers believed that all these sources emitted radio waves due according to the power law. But a section of scientists, including astronomer Mark Henry from Cambridge University in 1967, had proposed that not all sources were powered as per this law. “So, if a radio spectrum was found declining at a speed larger than +2.5, it was ruled out under the power law. But now, there is an alternate theory and it will begin to emerge as we can confirm that not all sources need to be classified under the power law. However, the number of such sources is still small,” said Chandra.
The NCRA team, comprising Gopal Krishna from Aryabhatta Research Institute of Observational Science; Mukul Mhaskey, Surajit Paul and Sameer Salunke from Savitribai Phule Pune University; Pratik Dhabadhe from Inter University Centre for Astronomy and Astrophysics; Sandeep Sirothia from Square Kilometre Array, South Africa, and former scientist at NCRA, is presently involved in an advanced study in tracing more such sources using the upgraded GMRT (uGMRT).


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