Connect with us

Space

Black hole gobbles up neutron star, causing ripples in space and time

In the same decade when gravitational waves and a neutron star merger have been observed, astronomers have now observed what they believe to be the first detection of a black hole swallowing a neutron star.

Last Wednesday, gravitational wave detectors in Italy and the US, called LIGO and Virgo, detected telltale ripples in space and time, traced to an event that happened 8,550 million trillion kilometers away from Earth.

Astronomers are analyzing the data from the detection to confirm the size of the two objects that came together to form such cataclysmic ripples, but the event is likely a black hole eating a neutron star.

“About 900 million years ago, this black hole ate a very dense star, known as a neutron star, like Pac-man — possibly snuffing out the star instantly,” said Susan Scott, leader of the General Relativity Theory and Data Analysis Group at Australian National University and chief investigator with the ARC Centre of Excellence for Gravitational Wave Discovery. “The ANU SkyMapper Telescope responded to the detection alert and scanned the entire likely region of space where the event occurred, but we’ve not found any visual confirmation.”

Essentially, black holes and neutron stars are the leftovers after stars die.

Neutron stars are the smallest in the universe, the remnants of supernovae. Their diameters are comparable to the size of a city like Chicago or Atlanta, but they are incredibly dense, with masses bigger than that of our sun.

When massive stars collapse at the end of their lives, they form an area of accelerating gravity so strong that nothing, including light, can escape it.

Like the other groundbreaking detections this decade, this new detection could provide more crucial evidence for previously unseen events that occur in space.

“We have always thought that there should be binary systems of a black hole and a neutron star circling each other out in space, so if this event is confirmed, it would be the first evidence that such systems do actually exist, and that some of them are spiraling closer and closer and eventually smashing together,” Scott said.

If the neutron star is not much smaller in mass than the black hole, the astronomers would expect more orbits to bring them closer together. This would shred the neutron star, creating electromagnetic signals that can be detected, Scott said. The signal would tell the astronomers about the properties of the star, hinting at their mysterious composition.

But if the masses of the two objects differ, the neutron star would likely be swallowed whole and not emit radiation. Because there hasn’t been a signal in the area where the event occurred, the researchers believe this is the scenario that occurred.

Astronomers want to learn the masses of the two objects. An object greater than five times the mass of the sun is considered a black hole. If it’s less than three times the mass of the sun, it’s a neutron star.

One potential small possibility is that the smaller object could be a very light black hole, Scott said, which would still be an exciting consolation prize.

“We are not aware of any black holes in the universe with masses less than about five solar masses,” Scott said. “This would raise many new questions such as, ‘how does such a light black hole form?’”

If the detection of the black hole swallowing the neutron star is confirmed, that would complete the detectors’ trifecta this decade, including gravitational waves and neutron star collisions.

Gravitational waves are ripples in space and time. Neutron star collisions release gravitational waves, light and heavy elements like gold.

Earlier this year after the gravitational wave detectors were turned on in April, scientists believe they may have detected the never-before-seen collision of a neutron star and a black hole, a collision between two neutron stars and three potential black hole mergers. The detectors’ observations are being regarded as candidates until further data can confirm them.

If this trifecta is complete, the researchers want to detect more systems, including black holes and neutron stars merging.

“We can better estimate the population size of these systems in the universe and also better understand how these systems ‘get together’ in the first place,” Scott said. “On the extended wish list we would soon hope to have a supernova which goes off somewhere close so that we can capture the expected gravitational waves from this type of event and better model the supernova process.”

The detection teams are also working on a way to detect the result of two neutron stars that briefly create a bigger neutron star when they collide. It’s possible that this bigger neutron star would be short-lived, but any detection from it could inform the astronomers about the collision process for neutron stars and their structure.

Source edition.cnn.com

Advertisement
Comments

Space

Visiting interstellar comet is caught on camera

Image Credit: Gemini Observatory / NSF / AURA

A two-color composite image of the visiting comet. 

Astronomers have revealed that comet 2I/Borisov is remarkably similar to comets from our own solar system.

First observed on August 30th, the comet, which is the second confirmed interstellar visitor to our solar system, was announced last month by the Minor Planet Center (MPC) at Harvard University.

The first, an object known as ‘Oumuamua, was discovered back in 2017.

Perhaps the most remarkable thing about 2I/Borisov however is just how unremarkable it actually is.

“This is the first comet known to science that arrived from outside the solar system, and it is completely similar to those we see inside the solar system,” said astronomer Michal Drahus.

Its discovery suggests that there are several nearby solar systems very much like our own and that comets like those we find in our local neighborhood are not uncommon elsewhere in the universe.

Observations using the William Herschel Telescope on La Palma, Spain and the Gemini North telescope on Mauna Kea, Hawaii have shown that 2I/Borisov has a distinctive and familiar coma (a billowing cloud of gas and dust) as well as a short, fat tail.

Its nucleus is thought to be 2km wide .

“This appears to be a completely unremarkable comet on a very remarkable orbit,” said astronomer Colin Snodgrass from Edinburgh University.

“It’s very interesting that this interstellar comet looks like our own ones.”

“It implies that some of the formation processes we are trying to figure out with detailed observation of comets and asteroids, or space missions like Rosetta, are common between stars.”

Source: Guardian

Continue Reading

Space

Study Reveals Six Galaxies Undergoing Sudden, Dramatic Transitions

Galaxies come in a wide variety of shapes, sizes and brightnesses, ranging from humdrum ordinary galaxies to luminous active galaxies. While an ordinary galaxy is visible mainly because of the light from its stars, an active galaxy shines brightest at its center, or nucleus, where a supermassive black hole emits a steady blast of bright light as it voraciously consumes nearby gas and dust.

Sitting somewhere on the spectrum between ordinary and active galaxies is another class, known as low-ionization nuclear emission-line region (LINER) galaxies. While LINERs are relatively common, accounting for roughly one-third of all nearby galaxies, astronomers have fiercely debated the main source of light emission from LINERs. Some argue that weakly active galactic nuclei are responsible, while others maintain that star-forming regions outside the galactic nucleus produce the most light.

A team of astronomers observed six mild-mannered LINER galaxies suddenly and surprisingly transforming into ravenous quasars–home to the brightest of all active galactic nuclei. The team reported their observations, which could help demystify the nature of both LINERs and quasars while answering some burning questions about galactic evolution, in the Astrophysical Journal on September 18, 2019. Based on their analysis, the researchers suggest they have discovered an entirely new type of black hole activity at the centers of these six LINER galaxies.

“For one of the six objects, we first thought we had observed a tidal disruption event, which happens when a star passes too close to a supermassive black hole and gets shredded,” said Sara Frederick, a graduate student in the University of Maryland Department of Astronomy and the lead author of the research paper. “But we later found it was a previously dormant black hole undergoing a transition that astronomers call a ‘changing look,’ resulting in a bright quasar. Observing six of these transitions, all in relatively quiet LINER galaxies, suggests that we’ve identified a totally new class of active galactic nucleus.”

All six of the surprising transitions were observed during the first nine months of the Zwicky Transient Facility (ZTF), an automated sky survey project based at Caltech’s Palomar Observatory near San Diego, California, which began observations in March 2018. UMD is a partner in the ZTF effort, facilitated by the Joint Space-Science Institute (JSI), a partnership between UMD and NASA’s Goddard Space Flight Center.

Changing look transitions have been documented in other galaxies–most commonly in a class of active galaxies known as Seyfert galaxies. By definition, Seyfert galaxies all have a bright, active galactic nucleus, but Type 1 and Type 2 Seyfert galaxies differ in the amount of light they emit at specific wavelengths. According to Frederick, many astronomers suspect that the difference results from the angle at which astronomers view the galaxies.

Type 1 Seyfert galaxies are thought to face Earth head-on, giving an unobstructed view of their nuclei, while Type 2 Seyfert galaxies are tilted at an oblique angle, such that their nuclei are partially obscured by a donut-shaped ring of dense, dusty gas clouds. Thus, changing look transitions between these two classes present a puzzle for astronomers, since a galaxy’s orientation towards Earth is not expected to change.

Frederick and her colleagues’ new observations may call these assumptions into question.

© R. Buta (University of Alabama/Image enhancement: Jean-Baptiste Faur Spiral Seyfert Galaxy NGC 3081: Seyfert galaxies are one of the two largest groups of active galaxies, along with quasars. They have quasar-like nuclei with very high surface brightnesses whose spectra reveal strong, high-ionisation emission lines, but unlike quasars, their host galaxies are clearly detectable.

© R. Buta (University of Alabama/Image enhancement: Jean-Baptiste Faur
Spiral Seyfert Galaxy NGC 3081: Seyfert galaxies are one of the two largest groups of active galaxies, along with quasars. They have quasar-like nuclei with very high surface brightnesses whose spectra reveal strong, high-ionisation emission lines, but unlike quasars, their host galaxies are clearly detectable.

“We started out trying to understand changing look transformations in Seyfert galaxies. But instead, we found a whole new class of active galactic nucleus capable of transforming a wimpy galaxy to a luminous quasar,” said Suvi Gezari, an associate professor of astronomy at UMD, a co-director of JSI and a co-author of the research paper. “Theory suggests that a quasar should take thousands of years to turn on, but these observations suggest that it can happen very quickly. It tells us that the theory is all wrong. We thought that Seyfert transformation was the major puzzle. But now we have a bigger issue to solve.”

Frederick and her colleagues want to understand how a previously quiet galaxy with a calm nucleus can suddenly transition to a bright beacon of galactic radiation. To learn more, they performed follow-up observations on the objects with the Discovery Channel Telescope, which is operated by the Lowell Observatory in partnership with UMD, Boston University, the University of Toledo and Northern Arizona University. These observations helped to clarify aspects of the transitions, including how the rapidly transforming galactic nuclei interacted with their host galaxies.

“Our findings confirm that LINERs can, in fact, host active supermassive black holes at their centers,” Frederick said. “But these six transitions were so sudden and dramatic, it tells us that there is something altogether different going on in these galaxies. We want to know how such massive amounts of gas and dust can suddenly start falling into a black hole. Because we caught these transitions in the act, it opens up a lot of opportunities to compare what the nuclei looked like before and after the transformation.”

Unlike most quasars, which light up the surrounding clouds of gas and dust far beyond the galactic nucleus, the researchers found that only the gas and dust closest to the nucleus had been turned on. Frederick, Gezari and their collaborators suspect that this activity gradually spreads from the galactic nucleus–and may provide the opportunity to map the development of a newborn quasar.

“It’s surprising that any galaxy can change its look on human time scales. These changes are taking place much more quickly than we can explain with current quasar theory,” Frederick said. “It will take some work to understand what can disrupt a galaxy’s accretion structure and cause these changes on such short order. The forces at play must be very extreme and very dramatic.”

In addition to Frederick and Gezari, UMD-affiliated co-authors of the research paper include Adjunct Associate Professor of Astronomy Bradley Cenko, former Neil Gehrels Prize Postdoctoral Fellow Erin Kara and astronomy graduate student Charlotte Ward.

More information: Sara Frederick et al, A New Class of Changing-look LINERs, The Astrophysical Journal (2019). DOI: 10.3847/1538-4357/ab3a38

Eureka Alert
Headline Image: © (Left; infrared & visible light imagery): ESA/Hubble, NASA and S. Smartt (Queen’s University Belfast); (Right; artist’s concept): NASA/JPL-Caltech

Source link

Continue Reading

Space

Giant black hole at centre of Milky Way exploded ‘recently’ – and blast was felt 200,000 light-years away

THE SUPERMASSIVE black hole at the centre of the Milky Way exploded 3.5million years ago, according to astronomers.

This is considered to be ‘astonishingly recent’ in galactic terms and is changing what scientists thought they knew about our galaxy.

This artist’s impression shows the huge bursts of radiation exploding from the centre of the Milky Way and reaching the Magellanic Stream

Professor Lisa Kewley, who worked on the study, said: “This is a dramatic event that happened a few million years ago in the Milky Way’s history.

“A massive blast of energy and radiation came right out of the galactic centre and into the surrounding material.

“This shows that the centre of the Milky Way is a much more dynamic place than we had previously thought. It is lucky we’re not residing there!”

The cataclysmic blast ripped through our galaxy and was likely felt 200,00 light years away in the Magellanic Stream.

The diameter of the Milky Way itself is thought to be up to 200,000 light years in size

It is considered to be a recent event because when it happened the dinosaurs had already been wiped out for 63million years and human ancestors were already walking on Earth.

This black hole blast phenomenon is known as a Seyfert flare.

The astronomers think it would have created two enormous ‘ionisation cones’ that would have sliced through the Milky Way.

They think it was caused by nuclear activity in the gigantic black hole, known as Sagittarius A.

It is estimated to have lasted for around 300,000 years, which is extremely short in galactic terms.

Co-author Magda Guglielmo from the University of Sydney said: “These results dramatically change our understanding of the Milky Way.

“We always thought about our Galaxy as an inactive galaxy, with a not so bright centre.

“These new results instead open the possibility of a complete reinterpretation of its evolution and nature.

“The flare event that occurred three million years ago was so powerful that it had consequences on the surrounding of our Galaxy.

“We are the witness to the awakening of the sleeping beauty.”

The research was led by by Professor Joss Bland-Hawthorn from Australia’s ARC Centre of Excellence for All Sky Astrophysics in 3 Dimensions (ASTRO 3D).

During the study, data was gathered by the Hubble Space Telescope and used to calculate when and how the explosion took place.

It will soon be published in The Astrophysical Journal.

What is a black hole? The key facts

Here’s what you need to know…

What is a black hole?

  • A black hole is a region of space where absolutely nothing can escape
  • That’s because they have extremely strong gravitational effects, which means once something goes into a black hole, it can’t come back out
  • They get their name because even light can’t escape once it’s been sucked in – which is why a black hole is completely dark

What is an event horizon?

  • There has to be a point at which you’re so close to a black hole you can’t escape
  • Otherwise literally everything in the universe would have been sucked into one
  • The point at which you can no longer escape from a black hole’s gravitational pull is called the event horizon
  • The event horizon varies between different black holes, depending on their mass and size

What is a singularity?

  • The gravitational singularity is the very centre of a black hole
  • It’s a one-dimensional point that contains an incredibly large mass in an infinitely small space
  • At the singularity, space-time curves infinitely and the gravitational pull is infinitely strong
  • Conventional laws of physics stop applying at this point

How are black holes created?

  • Most black holes are made when a supergiant star dies
  • This happens when stars run out of fuel – like hydrogen – to burn, causing the star to collapse
  • When this happens, gravity pulls the centre of the star inwards quickly, and collapses into a tiny ball
  • It expands and contracts until one final collapse, causing part of the star to collapse inward thanks to gravity, and the rest of the star to explode outwards
  • The remaining central ball is extremely dense, and if it’s especially dense, you get a black hole

Source newsamed.com

Continue Reading

Trending