Black Hole-Neutron Star Collisions Could Finally Settle the Different Measurements Over the Expansion Rate of the Universe

If you’ve been following developments in astronomy over the last few years, you may have heard about the so-called “crisis in cosmology,” which has astronomers wondering whether there might be something wrong with our current understanding of the Universe. This crisis revolves around the rate at which the Universe expands: measurements of the expansion rate in the present Universe don’t line up with measurements of the expansion rate during the early Universe. With no indication for why these measurements might disagree, astronomers are at a loss to explain the disparity.

The first step in solving this mystery is to try out new methods of measuring the expansion rate. In a paper published last week, researchers at University College London (UCL) suggested that we might be able to create a new, independent measure of the expansion rate of the Universe by observing black hole-neutron star collisions.

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Are we Seeing a Star That Just got Spaghettified?

Sometimes astronomers come up with awesome names for certain phenomena and then feel like they can’t use them in formal scientific contexts.  Tidal Disruption Events (TDEs) are one of those – colloquially they are known as “spaghettifications” where a star is pulled apart until its constituent matter looks like a string of spaghetti.  

Astronomers have long known of this process, which takes place when a star gets too close to a black hole, but most of that knowledge has come through studying radiation bursts emitted by the blackhole as it devoured the star.  Now, a team led by Giacomo Cannizzaro and Peter Jonker from SRON, the Netherlands Institute for Space Research, and Radboud University now think they have captured the first glimpses of a star actively being spaghettified around the pole of a black  hole.

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An Exotic Explanation for the Most Extreme Gravitational Wave Detected so far

In May of 2019, the gravitational wave observatories LIGO and Virgo detected the merger of two black holes. One had a mass of 85 Suns, while the other was 66 solar masses. The event was named GW190521 and was the largest merger yet observed. It produced a 142 solar mass black hole, making it the first gravitational wave observation of an intermediate mass black hole. But the event also raised several questions.

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A map of 25,000 Supermassive Black Holes Across the Universe

The Low-Frequency Array (LOFAR) is a different kind of radio telescope. Although radio light has the longest wavelengths and lowest frequencies of the electromagnetic spectrum, much of radio astronomy has focused on the higher frequency end. Observatories such as ALMA study radio light at frequencies of hundreds of Gigahertz, and the VLA studies the fifty Gigahertz range, LOFAR captures radio signals below 250 Megahertz, which is in the range of the lowest radio frequencies that can be seen from Earth.

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When Galaxies Collide, Black Holes Don’t Always Get the Feast They Were Hoping for

What happens when galaxies collide? Well, if any humans are around in about a billion years, they might find out. That’s when our Milky Way galaxy is scheduled to collide with our neighbour the Andromeda galaxy. That event will be an epic, titanic, collision. The supermassive black holes at the center of both galaxies will feast on new material and flare brightly as the collision brings more gas and dust within reach of their overwhelming gravitational pull. Where massive giant stars collide with each other, lighting up the skies and spraying deadly radiation everywhere. Right?

Maybe not. In fact, there might be no feasting at all, and hardly anything titanic about it.

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A New Idea to Harness Energy From Black Holes

Fifty years ago, English mathematical physicist and Nobel-prize winner Roger Penrose proposed that energy could be extracted from the space around a rotating black hole. Known as the ergosphere, this region lies just outside an event horizon, the boundary within which nothing can escape a black hole’s gravitational pull (even light). It is also here where infalling matter is accelerated to incredible speeds and emits all kinds of energy.

This became known as the Penrose Process, which many theorists have since expanded on. The latest comes from a study conducted by researchers from Columbia University and the Universidad Adolfo Ibáñez in Chile. With support from organizations like NASA, they demonstrated how a better understanding of the physics at work around spinning black holes could allow us to harness their energy someday.

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What Happens to Their Supermassive Black Holes When Galaxies Collide?

What’s better than two gigantic galaxies swirling into one another until they collide?  How about three galaxies swirling into one another until they collide – and they all have supermassive black holes at their core to boot!  Recently, a team led by Dr. Adi Foord of Stanford combed through data from the WISE mission and the Sloan Digital Sky Survey to search for instances of three galaxies colliding with one another. In all that data, they managed to find 7 separate systems that met those criteria.

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Hubble Sees Dark Shadows That Could Be Cast by a Supermassive Black Hole

We use the term ‘supermassive black hole’ with a kind of casual familiarity. But stop and think about what they really are: Monstrous, beguiling singularities where the understood laws of physics and cosmology are brought to their knees. A region where gravity is so powerful that it warps everything around it, drawing material in—even light itself—and sometimes spitting out jets of energy at near-light-speed.

It was only recently that we got our first image of one of these monstrosities. Now, the Hubble has captured an image of a supermassive black hole (SMBH), or what might be part of its shadow, anyway.

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Merging Black Holes and Neutron Stars. All the Gravitational Wave Events Seen So Far in One Picture

The Theory of Relativity predicted the existence of black holes and neutron stars. Einstein gets the credit for the theory because of his paper published in 1915, even though other scientists’ work helped it along. But regardless of the minds behind it, the theory predicted black holes, neutron stars, and the gravitational waves from their mergers.

It took about one hundred years, but scientists finally observed these mergers and their gravitational waves in 2015. Since then, the LIGO/Virgo collaboration has detected many of them. The collaboration has released a new catalogue of discoveries, along with a new infographic. The new infographic displays the black holes, neutron stars, mergers, and the other uncertain compact objects behind some of them.

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