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 Post subject: Re: Space Is Deep
PostPosted: Wed May 06, 2020 5:40 am 
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Astronomers find closest black hole to Earth, hiding in plain sight
https://www.sciencemag.org/news/2020/05/astronomers-find-closest-black-hole-earth-hiding-plain-sight

By Daniel Clery May. 6, 2020 , 8:00 AM

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The Milky Way galaxy is thought to contain hundreds of millions of black holes. But only a few dozen have revealed themselves—through the x-ray glow of hot gases that surround them. Now, astronomers have found a “dark” black hole only 1000 light years away from Earth—just down the road in galactic terms. It is the closest black hole to our planet ever found, in a star system that is visible to the naked eye. “They have good evidence,” says Todd Thompson, an astronomer at Ohio State University. “I believe them.”

The invisible nature of most black holes frustrates astronomers, who can learn about this final stage of stellar evolution only from the few dozen that have been found heating up an “accretion disk”--swirling gas that they gobble up. Recently, however, astronomers have found several naked, non-accreting candidates, using a technique borrowed from exoplanet searches. Exoplanet hunters look for periodic shifts in the frequency of the light from stars as it moves toward and away from Earth. This can be caused by the gravity of an invisible orbiting companion tugging on it. A small tug indicates a lightweight planet; a larger tug could be a sign of a black hole.

Thomas Rivinius, an astronomer with the European Southern Observatory (ESO), and his colleagues studied the unusual star system HR 6819 in this way using a 2.2-meter telescope in Chile, operated by ESO and the Max Planck Society. They thought it was a binary system but there was an extra wobble in the periodic light shifts of one of the stars that indicated something else was asserting its presence. It turned out to be a triple system, with one star in a fast 40-day orbit with an unseen companion and another star on a more distant, slow moving trajectory, they write today in Astronomy & Astrophysics. The invisible companion’s mass was large enough—four times the mass of the Sun—that, if it was a star, “we would have seen it,” Rivinius says.

To be sure that the companion is a black hole, the researchers will take a closer look at the system. The team has applied for time to use ESO’s optical interferometer, a device that combines the light of separate telescopes to achieve the resolution of a much larger one. “We wouldn’t see the black hole,” Rivinius says, but they should see one of the stars “orbit something else that’s not there.”

The team was lucky to stumble upon such a system, says astronomer Benjamin Giesers of Göttingen University in Germany. “You have to observe a lot of stars to find one.” He and his colleagues surveyed 25 globular clusters, hives of stars around the Milky Way that each contain hundreds of thousands of stars. In 2017, they found one black hole candidate, around 4.5 times the mass of the Sun, tugging on its companion star.

In 2019, Thompson and his colleagues also had lucky strike, after trawling through data culled from the Sloan Digital Sky Survey and using the All-Sky Automated Survey for Supernovae to whittle down the numbers. “We were looking for a star doing something that it shouldn’t be doing,” he says. They finally found a rapidly rotating giant star called 2MASS J05215658+4359220 which, from its wobbles, indicated a black hole companion of around 3.5 solar masses. Studying systems such as this and HR 6819 will help astronomers “understand how binaries work and how black holes form,” Thompson says. The new find “is very close and bright,” he says. “It will be well studied.”

He adds a note of caution since some black hole candidates haven’t survived closer examination. “I don’t think anything is ironclad. You have to be skeptical.” But the fact that non-accreting black holes are starting to show themselves in binary and triple systems suggests that there must be many more isolated ones out there, some even closer than HR 6819.

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 Post subject: Re: Space Is Deep
PostPosted: Sat May 09, 2020 10:24 am 
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Kiwi astronomers make groundbreaking shockwaves discovery in 'new' star
Samesh Mohanlall·05:00, May 10 2020

Image
Supplied/The-Timaru-Herald
An artist's portrayal of a classical nova explosion.

A team of New Zealand astronomers has played a part in a major astronomical breakthrough, observing for the first time a nova 13,000 light years from Earth.

The University of Canterbury team joined international astronomers in research that has shown “shock waves” from the nova explosion, rather than nuclear fusion, cause most of the brightness from these phenomena.

A nova, or stella nova — Latin for “new star” — is a sudden explosion on the surface of a white dwarf, which is the hot, burnt-out core of a star. It produces an incredible amount of energy and light, increasing the star’s brightness by thousands or even millions of times.

If a nova occurs relatively close to earth it can appear as a new star to the naked eye.

Team leader, associate professor in astronomy and director of the University of Canterbury Mt John Observatory, Karen Pollard, said novae are relatively common in the galaxy and understanding what makes them glow and what their energy source is, is important for understanding how stars evolve.

“It's a really good example of how observations from lots of different telescopes around the world and from telescopes in space — combining all those observations — can give us a real insight into what these stars actually are and how they're evolving.

“The common theory is these stars have big thermo-nuclear fusion explosions occurring on the surface of these white dwarf stars, but the observations that our collaborations took showed that a lot of the light is actually output by shockwaves that are occurring from the explosion.”

The team used NASA’s space-based telescopes and ground-based telescopes, including some at the Mt John Observatory in Tekapo, to observe the nova.

Image
SUPPLIED
Prof Karen Pollard at the Very Large Telescope (VLT), a telescope facility in the Atacama Desert of Chile in 2018.

Pollard said this discovery was important for an observatory like Mt John as the team was able to contribute its observations, and “they were important for deciding what was happening in the system”.

“It allows our researchers to collaborate with teams from all around the world and if there's any such observations we will certainly be contacted, and we can contribute to observations of similar types of objects.

“There's lots of objects that occur randomly in space like black hole mergers, supernovas (exploding star) and novas. If we had an observatory where we can start observing very quickly that makes our observatory very useful for studying these types of objects.”

The outburst originated from a star system discovered in March 2018 called V906 Carinae, which lies in the constellation Carina. The Tekapo-based team started observing the nova which actually happened 13,000 years ago, soon after its discovery was announced.

“It was a relatively bright nova in the constellation Carina and people would have been able to see it with their naked eyes if they knew which position in the sky to look,” Pollard said.

“13,000 light years does seem like a long way away but it was relatively bright so we could see it quite clearly, and that's why we got such good observations of it from Mt John because it was a long way south and relatively bright.”

Their results are documented in a new paper, co-authored by Pollard, called Direct evidence for shock-powered optical emission in a nova published in April in the international journal Nature Astronomy.

“The interesting thing was this nova was observed by lots of different telescopes so there was lots of ground based telescopes, including the ones at Mt John, but there were also several in space that observed this nova.

“They observed it at optical wavelengths and x-rays and gamma rays and from those observations we were able to obtain lots of information about what was happening in the star.”

Each nova explosion releases a total of 10,000 to 100,000 times the annual energy output of our sun.

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https://www.stuff.co.nz/technology/3000 ... n-new-star

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 Post subject: Re: Space Is Deep
PostPosted: Mon May 11, 2020 10:09 am 
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That time the Juno spacecraft got busted looking up Jupiter's skirt:
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 Post subject: Re: Space Is Deep
PostPosted: Wed May 13, 2020 2:48 am 
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Experts solve mystery of a giant X-shaped galaxy with monster black hole
Baerbel Koribalski·09:33, May 13th, 2020

Image
CSIRO/Supplied
ASKAP image of the giant X-shaped radio galaxy PKS 2014-55.

A team of US and South African researchers has published highly detailed images of the largest X-shaped “radio galaxy” ever discovered.

Notably, they’ve helped resolve ongoing confusion about the unusual shape of the galaxy called PKS 2014-55.

The spectacular new images were taken using the 64-antenna MeerKAT telescope in South Africa, by an international research team led by Bill Cotton of the US National Radio Astronomy Observatory.

Image
NASA Goddard Space Flight Centre
This image of the Centaurus A galaxy incorporates both optical and radio data. Every galaxy has a black hole at its centre, including the Milky Way.

ZOOMING IN ON A COSMIC GIANT

Our research team also took detailed images of galaxy PKS 2014-55 last year, as part of the Evolutionary Map of the Universe project led by astrophysicist Ray Norris. We used CSIRO’s Australian Square Kilometre Array Pathfinder (ASKAP) telescope in Western Australia, which just completed its first set of pilot astronomical surveys.

Thanks to its innovative “radio cameras”, ASKAP can rapidly map very large areas of the sky to catalogue millions of objects emitting radio waves, from nearby supernova remnants to distant galaxies.

The prominent X-shape of PKS 2014-55 is made up of two pairs of giant lobes consisting of hot jets of electrons. These jets spurt outwards from a supermassive black hole at the galaxy’s heart.

The lobes emit electromagnetic radiation in the form of radio waves, which can only be detected by radio telescopes like ASKAP. Humans can’t see radio waves. But if we could, from Earth PKS 2014-55 would look about the same size as the Moon.

Image
SARAO/Supplied
A MeerKAT image of the giant X-shaped radio galaxy PKS 2014-55.

WHAT MAKES A RADIO GALAXY?

Typically, radio galaxies have only one pair of lobes. One is a “jet” and the other a “counter-jet”.

These jets expand into the surrounding space at nearly the speed of light. They initially move in a straight line, but twist and bend into many marvellous shapes as they encounter their surroundings.

Centaurus A is an example of a giant elliptical galaxy with two prominent radio lobes.

Galaxy PKS 2014-55’s giant X-shape, with two pairs of lobes emerging at very different angles, is highly unusual.

WHAT MAKES THE LOBES?

To understand why having two pairs of lobes is unusual, we first need to understand what creates the lobes.

Nearly all big galaxies have a supermassive black hole at their centre.

Image
Supplied
The Australian Square Kilometre Array radio telescope, located in the Murchison Shire in Western Australia.

In an active galaxy, powerful jets of charged particles can emerge from the area around the supermassive black hole. Astronomers believe these are emitted from near the poles of the black hole, which is why there are two of them, and they usually point in opposite directions.

When the black hole’s activity stops, the jets stop growing and the material in them flows back towards the centre. Thus, what we see as one lobe of a radio galaxy is made up of both a jet spurting out, and the backflow material.

A MYSTERY SOLVED

In the past, there were two major theories for why PKS 2014-55 has two pairs of lobes.

The first suggested there were actually two massive active black holes at the galaxy’s centre, each emitting two powerful jets.

The second theory suggested the supermassive black hole had undergone a spin flip. This is when a rotating black hole’s spin axis has a sudden change in orientation, resulting in a second pair of jets at a different angle from the first pair.

Image
SARAO/SUPPLIED
The South African Radio Astronomy Observatory’s MeerKAT telescope array consists of 64 radio dishes.

But the recent observations from the South African MeerKAT telescope strongly suggest a third possibility: that the two larger lobes are the fast-moving particles zooming out from the black hole, while the two smaller lobes are the backflow looping around to fall back in.

The MeerKAT team achieved high-resolution images ten times more sensitive than our ASKAP pilot observations conducted in Australia last year.

A COSMIC WONDER

Using CSIRO’s ASKAP telescope, our team observed the “purple butterfly” of PKS 2014-55 to be an enormous cosmic structure. It spans at least five million light years – about 20 times the size of our own Milky Way galaxy.

PKS 2014-55 is located on the outskirts of a massive cluster of galaxies known as Abell 3667. It was discovered more than 60 years ago using the Mills Cross Telescope at CSIRO’s old Fleurs field station in New South Wales.

The galaxy’s first detailed radio picture was taken by Ron Ekers in 1969.

ASKAP

The ASKAP telescope we used to capture PKS 2014-55 is an array of 36 radio dishes laid out in a pattern six kilometres in diameter. Together, the dishes make up a large radio telescope that uses Earth’s rotation to produce sharp images of astronomical sources near and far.

Each dish is 12m wide and equipped with new technologies developed by CSIRO and industry partners. ASKAP is a fast survey machine, taking radio images over very wide areas of the sky. Several surveys of the entire sky are expected to start next year.

We acknowledge the Wajarri Yamatji as the traditional owners of the Murchison Radio-astronomy Observatory site. The Conversation

Baerbel Koribalski is a senior research scientist at CSIRO.

This article is republished from The Conversation under a Creative Commons licence. Read the original article.

https://www.stuff.co.nz/science/1214954 ... black-hole

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 Post subject: Re: Space Is Deep
PostPosted: Wed May 13, 2020 2:58 am 
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Earth-like planet discovered by New Zealand astronomers
15:46, May 11th, 2020

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Bryan Goff/Unsplash
University of Canterbury astronomers have discovered a "one in a million" Earth-like planet. (File photo)


The existence of a planet with rare similarities to Earth is a "one in a million" discovery uncovered by New Zealand astronomers.

University of Canterbury astronomers said the planet was one of only a handful with a similar size and mass to Earth.

However, the "Super-Earth" planet's orbit causes it to have a year lasting 617 days — almost double the length of Earth's.

It orbits a smaller host star about 10 per cent of the size of our sun.

Lead researcher Dr Antonio Herrera Martin said the discovery was one of the first events he had personally seen and was "extremely rare".

"This is a one in a million discovery due to the way the planet was discovered and the fact it is three to four times larger than the size of Earth," he said.

The planet was discovered using a technique called microlensing, where a star passes in front of another star, causing a temporary shedding of light that can reveal other undiscovered stars or planets.

Only one in a million stars in the galaxy are affected by microlensing at any one time, making the chance of such a discovery very rare.

"If the planet was any smaller, in another position or orbiting another way, it is highly unlikely we would have ever seen it," Martin said.

The discovery was the combination of good collaborative research work and "insanely lucky timing."

"I came across the planet almost by a mistake. That's how rare it was. The raw data showed nothing of note and it was only when I took a closer look that I saw a tiny bump, which turned out to be our newly discovered planet.

"It was certainly special and very satisfactory."

The event was first observed through two Chilean telescopes in 2018 and was named OGLE-2018-BLG-0677 after the date it was discovered and the makes of the telescopes that first observed it.

Since that first observation, University of Canterbury astronomers started analysing the data in January 2019 and spent nearly a full year to ensure the findings were accurate.

The discovery has been a collaborative effort between astronomers in Korea, Australia, Chile, South Africa and New Zealand, and their research has been published in the Astronomical Journal.

Stuff

https://www.stuff.co.nz/science/3000096 ... stronomers

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