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Our Sun’s ‘Near’ Miss With A Passing Star

Stars jostling around the galaxy aren’t quite like a cosmic game of pool. But they do have occasional near misses as they speed past each other. Back when spears and stone points were the height of human technology, astronomers say, our solar system had a close encounter of the interstellar kind.

The brief visitor was Scholz’s star, and it might have grazed the outer edge of the solar system’s distant Oort Cloud about 70,000 years ago – carrying its companion, a likely brown dwarf, along for the ride.

It’s unclear whether the near miss was close enough to give objects in the Oort Cloud, our solar system’s halo of dormant comets, a gravitational nudge to fall toward the Sun. But the interstellar trespasser highlights a sometimes-forgotten reality: On long time scales, stars seem to fly around like sparks from a campfire, occasionally coming close enough to disturb each other’s cometary clouds.

Such close passes could have profound implications for exoplanets – planets orbiting other stars – and how they got where they are. At least some of the time, an interloper could become a thief, stripping a star of one or more planets – or vice versa.

Our solar system, too, might have been shaped and sculpted by stellar flybys.

A 2018 study showed that the orbital motions of some of our solar system’s small bodies appear still to bear the imprint of Scholz’s gravitational wake. And some planet-like objects in the Kuiper belt, the collection of rocky and icy bodies past the orbit of Neptune, could have been stolen from another star far earlier – in fact, soon after our Sun was born. Scholz’s flyby could just be the latest in a series.

The discovery of our star-crossed close encounter was almost as random as the event itself.

It started when astronomer Eric Mamajek, deputy program scientist for NASA’s Exoplanet Exploration program, was a professor at the University of Rochester. He took yearly excursions to Santiago, Chile, where he made observations with world-class telescopes.

On one such visit in 2013, a fellow astronomer, Valentin Ivanov, showed him a peculiar result: A newly discovered nearby star with a lengthy catalog designation (later nicknamed for its discoverer, Ralf-Dieter Scholz) seemed almost to be sitting still. Most stars move perceptibly across the sky over the course of a year, as measured in a unit called “arc seconds.” In terms of such “sideways” motion, this one hardly moved at all. Yet the star was only 22 light-years away – quite near to us by galactic standards.

Mamajek knew that could mean only one thing. Either the star was heading straight for us, or it was heading directly away. In this case, the astronomers had obtained measurements of the star’s Doppler shift – the reddening of light if a star is moving away, or a shift toward blue if it’s moving toward us.

“It was screaming away at 80 kilometers per second,” Mamajek recalled. And it didn’t take him long to do the math.

“In less than 15 minutes, we figured out that this star had passed within a light-year of the solar system, 70 or 80 thousand years ago,” he said.

The closest stars to our Sun today are the three in the Alpha Centauri system, about four light-years away. But if there were a star one light-year away, that could very well approach or even intersect with the outermost edge of the Oort Cloud.

Mamajek thinks that Scholz’s star, now known as the star that came closest to our solar system, could eventually lose that title. Extremely precise data from the European Space Agency’s new Gaia space probe will likely reveal more near misses, possibly closer ones. And in any case, another close pass by a star known as GJ 710 is due in about 1.3 million years.

For now, however, Scholz’s keeps its prize.

And might those rock-hammering, spear-shaping early humans have caught a glimpse as the star passed by? Turns out, not terribly likely. Scholz’s star is a red dwarf, the smallest and faintest kind of star we know. Even at its nearest point, about 55,000 astronomical units from our Sun (5.1 trillion miles), Scholz’s star would have been 100 times too dim to be seen with the naked eye.

Still, there’s a chance the visitor made itself known. Red dwarfs are known periodically to emit extremely bright flares.

If the star sent up a flare as it was cruising past our solar system, our cave-dwelling ancestors just might have seen it.

Pat Brennan
ExoPlanet Exploration
Headline Image:© Michael Osadciw/University of Rochester

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Space

Neutron star formed in front of astronomers

Astronomers fought their way through the dusty curtain to the newborn neutron star

Thirty-three years ago, astronomers recorded a supernova explosion, 1987A. And just recently they found a neutron star formed in this cataclysm. This is the youngest such object in the history of observations. For some time, scientists doubted that they were observing exactly a neutron star, but fresh scientific work has provided very convincing evidence of this.

On February 23, 1987, male astronomers (and also female astronomers) received a gift from the Universe. On this day, supernova 1987A was discovered, which exploded in the Large Magellanic Cloud – a nearby dwarf galaxy, a satellite of the Milky Way.

As you know, a star dying in a supernova explosion (or rather, what is left of it) turns either into a black hole or into a neutron star. Scientists were confident that in the case of 1987A, the second option was realized. This was indicated by the flux of neutrinos recorded by terrestrial detectors simultaneously with the light of the flash.

Recall that a neutron star is a celestial body with a diameter of only a few kilometers, which, at the same time, is comparable in mass to the Sun. Due to the monstrous density and the most powerful magnetic field, the matter inside such an object is in states that cannot be reproduced in terrestrial laboratories. Therefore, neutron stars are of great interest to physicists. And, of course, astronomers who seek to figure out the ins and outs of every object and process in the universe.

The 1987A explosion gave researchers the first chance to study the neutron star that formed before their eyes and understand what these celestial bodies are like immediately after birth. All other known neutron stars are much older.

So, the second place belongs to the recently discovered object , which is 240 years old, and even it is surprisingly young compared to its counterparts millions of years old.

Let us clarify that new supernova explosions are discovered regularly and in large numbers , but in galaxies that are too distant to make out the formed neutron star. And the 1987A flare occurred only 168 thousand light years from Earth. It was the closest supernova explosion seen since the invention of the telescope.

Supernova Remnant 1987A at different wavelengths. The inset shows the radiation of a hot central object.Illustration ALMA (ESO / NAOJ / NRAO), P. Cigan, R. Indebetouw; NRAO / AUI / NSF, B. Saxton; NASA / ESA.

Alas, by pointing telescopes at the site of the 1987A flare, astronomers saw only a dense cloud of dust formed during a supernova explosion. For more than thirty years, using increasingly powerful instruments, scientists have tried to discern at least some trace of the central body. And finally they succeeded.

In 2019, the ALMA radio telescope helped astronomers see the supernova remnant 1987A in unprecedented detail. Thanks to this, astronomers discovered that there is a compact and very hot object in the center of the dust cloud. Although the “heater” itself remains hidden behind the dust curtain, the telescope records the radiation of the dust heated by it.

“We were very surprised to see this hot ball formed in a thick cloud of dust in a supernova remnant,” says co-author Mikako Matsuura of Cardiff University. “There must be something in the cloud that heats the dust and makes it glow This is why we assumed there was a neutron star hiding inside the dust cloud.

However, the radiation power seemed suspicious to scientists. Could a neutron star be so hot? Or is there something else lurking in the center of the dust cloud?

“We thought that such a neutron star might be too bright to exist. But then Dani Page and his team published a study that showed that a neutron star could actually be so bright because it is so young,” Matsuura says.

Supernova Remnant 1987A. Imaging in radio waves, visible light and X-rays. Translated by Vesti.Ru.Illustration ALMA (ESO / NAOJ / NRAO), P. Cigan, R. Indebetouw; NRAO / AUI / NSF, B. Saxton; NASA / ESA.

The scientific article , published in the edition of the Astrophysical Journal by Dany Page of the National Autonomous University of Mexico and his colleagues, set the record straight. Experts have shown that the dust-heating object at the center of Supernova remnant 1987A not only could be a neutron star, but could hardly be anything else.

According to the calculations of Page and his co-authors, the temperature of a neutron star 30 years after its birth should be five million degrees. This is just enough to explain the observed heating of the dust.

In addition, the central object is located exactly where the neutron star should have been thrown by the explosion (by the way, at the time of the cataclysm, it was moving at a speed of hundreds of kilometers per second).

Finally, recall that the neutrinos recorded in 1987 indicate that a neutron star was formed during a supernova explosion, not a black hole.

However, theoretically, the central object can be a black hole, onto which a dense stream of matter falls. But this requires a fantastically accurate adjustment of its properties to observational data, which is extremely unlikely. So experts are confident that they have finally “groped” for a newborn neutron star.

We now see the 1987A supernova remnant as it was 33 years after the explosion. Perhaps, after a few more decades, the dust cloud dispersed a little and began to transmit the radiation from the central object. Scientists are looking forward to the moment when these rays will reach the Earth.

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Space

Scientists have confirmed that something else existed before our universe

American scientists, using mathematical tools, described the inhomogeneities of the cosmic relic radiation that arose immediately after the origin of the Universe. 

The authors believe that their results confirm the correctness of the Big Bounce hypothesis, according to which the emergence of our universe was the result of the collapse of some “previous” universe. The results are published in the journal Physical Review Letters.

While Einstein’s theory of general relativity explains a wide range of astrophysical and cosmological phenomena, some properties of the universe remain a mystery. In particular, it cannot explain the uneven distribution of galaxies and dark matter in space.

Since the 1980s, Pennsylvania State University researchers have been developing a cosmological paradigm based on the concept of loop quantum gravity. This paradigm, called loop quantum cosmology, describes all modern large structures in the Universe as quantum fluctuations of space-time that took place at the birth of the world.

According to the generally accepted theory of the Big Bang, it all started with a singularity – a state in which all matter and energy were compressed into one point. Then, in the first fraction of a second, during a period called inflation, space swelled to enormous proportions. But the Big Bang theory does not explain what happened before the singularity, so this state cannot be described in terms of the laws of physics and mathematics.

Scientists at Pennsylvania State University hold the alternative Big Bounce hypothesis, according to which the current expanding universe arose from the supercompressed mass of the universe of the previous phase. To describe this state, they use a universal mathematical apparatus that combines quantum mechanics and the theory of relativity.

The authors trace the origin of the structure of the Universe to the smallest inhomogeneities recorded against the background of microwave relict cosmic radiation, which was emitted when the Universe was only 380 thousand years old.

But this radiation itself has three mysterious anomalies that are difficult to explain using classical physics. These deviations are so serious that many physicists began to talk about a crisis in cosmology.

In a new study, scientists argue that, from a loop quantum cosmology perspective, describing inflation removes two major anomalies in the CMB distribution.

“Using quantum loop cosmology, we naturally resolved two of these anomalies, avoiding a potential crisis,” co-author Donghui Jeong, associate professor in the Department of Astronomy and Astrophysics, said in a university press release. anomalies suggests that we live in an exclusive universe.”

The authors believe that the inhomogeneities of the CMB are the result of inevitable quantum fluctuations in the early Universe. During the accelerated phase of expansion – inflation – these initially tiny fluctuations were stretched by gravity, reflected in the observed irregularities.

“The standard inflationary paradigm, based on general relativity, views spacetime as a smooth continuum,” says the first author, Professor Abhay Ashtekar, director of the Pennsylvania State Institute of Gravity and Space. but upon closer inspection, you can see that it is woven from densely packed one-dimensional strands. And quantum strands are woven into the fabric of spacetime. With these strands, loop quantum cosmology allows us to go beyond the continuum described by general relativity.”

Scientists hope that new satellite missions such as LiteBIRD and Cosmic Origins Explorer, aimed at detecting traces of primary gravitational waves in the background of the background radiation, will confirm their findings.

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Space

Comet NEOWISE from Earth’s orbit: a mesmerizing video from ISS

The video was created after combining 550 images taken from the International Space Station.

In the darkness of the orbital night of July 5, NASA astronaut Bob Benken clung to the porthole of the International Space Station in anticipation of an incredible sight. Soon, in the predawn sky above the Earth, the main object of observations of all amateur astronomers of this summer, Comet NEOWISE, appeared.

Benken and his colleagues with the ISS made hundreds of comet shots, which were then turned into a slow motion movie by British graphic designer Sean Doran, who regularly processes NASA shots.

“Take a cool drink, turn off the light, get more comfortable and place the video on the big screen,” Doran urged in the description of the video.

Initially, Doran shared a four-fold version of the video, but later uploaded the video in 4K. The video shows the passage of a comet in front of observers from the ISS in real time.

The sequence consists of 550 long exposure photographs taken in seven minutes. Usually this gives only 18 seconds of video, so Doran interpolated the images to fill the frames and smoothed the sequence for smooth playback. 

Comet C / 2020 F3 was first discovered on March 27, 2020 using the NEOWISE telescope (The Near Earth Object Wide-field Infrared Survey Explorer), which gave it a second name.

Comet can be observed in the Northern Hemisphere from the equator to the 60th parallel of northern latitude. The best conditions for observations will develop around July 20, when NEOWISE enters the constellation Ursa Major with a brilliance of +3 magnitude.

At a minimum distance from the Earth, the comet will pass on July 23. It will be 0.692 astronomical units, or 103.52 million kilometers.

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