Brian Koberlein, Author at Universe Today

October 17, 2020October 17, 2020 by Brian Koberlein

We actually don’t know how fast the Milky Way’s supermassive black hole is spinning but there might be a way to find out

This illustration depicts a gas halo surrounding a quasar in the early Universe. The quasar, in orange, has two powerful jets and a supermassive black hole at its centre, which is surrounded by a dusty disc. The gas halo of glowing hydrogen gas is represented in blue. A team of astronomers surveyed 31 distant quasars, seeing them as they were more than 12.5 billion years ago, at a time when the Universe was still an infant, only about 870 million years old. They found that 12 quasars were surrounded by enormous gas reservoirs: halos of cool, dense hydrogen gas extending 100 000 light years from the central black holes and with billions of times the mass of the Sun. These gas stashes provide the perfect food source to sustain the growth of supermassive black holes in the early Universe.

Unless Einstein is wrong, a black hole is defined by three properties: mass, spin, and electric charge. The charge of a black hole should be nearly zero since the matter captured by a black hole is electrically neutral. The mass of a black hole determines the size of its event horizon, and can be measured in several ways, from the brightness of the material around it to the orbital motion of nearby stars. The spin of a black hole is much more difficult to study.

October 13, 2020October 13, 2020 by Brian Koberlein

Astronomers Watch a Star Get Spaghettified by a Black Hole

A star gets spaghettified as it is consumed by a black hole. Credit: ESO/M. Kornmesser

The gravitational dance between massive bodies, tidal forces occur because the pull of gravity from an object depends upon your distance from it. So, for example, the side of Earth near the Moon is pulled a bit more than the side opposite the Moon. As a result, the Earth stretches and flattens a bit. On Earth, this effect is subtle but strong enough to give the oceans high and low tides. Near a black hole, however, tidal forces can be much stronger, creating an effect known as spaghettification.

October 12, 2020October 12, 2020 by Brian Koberlein

Black Holes Make Complex Gravitational-Wave Chirps as They Merge

Simulated merger of two black holes. Credit: NASA's Goddard Space Flight Center

Gravitational waves are produced by all moving masses, from the Earth’s wobble around the Sun to your motion as you go about your daily life. But at the moment, those gravitational waves are too small to be observed. Gravitational observatories such as LIGO and VIRGO can only see the strong gravitational waves produced by merging stellar-mass black holes.

The chirp of a gravitational merger is clear. Credit: LIGO/Caltech/MIT/University of Chicago (Ben Farr)

October 8, 2020October 8, 2020 by Brian Koberlein

Gravitational-Wave Lensing is Possible, but it’s Going to be Incredibly Difficult to Detect

This diagram shows how Hubble is able to observe a quasar, a glowing disc of matter around a distant black hole, even though the black hole would ordinarily be too far away to see clearly. Credit: NASA and ESA

Gravity is a strange thing. In our everyday lives, we think of it as a force. It pulls us to the Earth and holds planets in orbits around their stars. But gravity isn’t a force. It is a warping of space and time that bends the trajectory of objects. Throw a ball in deep space, and it moves in a straight line following Newton’s First Law of Motion. Throw the same ball near the Earth’s surface, and it follows a parabolic trajectory caused by Earth’s warping of spacetime around it.

October 3, 2020October 3, 2020 by Brian Koberlein

Einstein. Right again

Simulation of M87 black hole showing the motion of plasma as it swirls around the black hole. Credit: L. Medeiros; C. Chan; D. Psaltis; F. Özel; University of Arizona; Institute for Advanced Study

Most of what we know about black holes is based upon indirect evidence. General relativity predicts the structure of a black hole and how matter moves around it, and computer simulations based on relativity are compared with what we observe, from the accretion disks that swirl around a black hole to the immense jets of material they cast off at relativistic speeds. Then in 2019, radio astronomers captured the first direct image of the supermassive black hole in M87. This allows us to test the limits of relativity in a new and exciting way.

September 27, 2020September 27, 2020 by Brian Koberlein

Time Travel, Without the Pesky Paradoxes

A time machine connects to the past. Credit: David Revoy / Blender Foundation (CC BY 3.0)

Time travel is a staple of science fiction, and not without reason. Who wouldn’t want to go back in time to explore history, or save the world from catastrophe. Time travel has also been deeply studied within the context of theoretical physics because it tests the limits of our scientific theories. If time travel is possible, it has implications for everything from the origin of the universe to the existence of free will. One of the central problems of time travel theory is that it gives rise to logical paradoxes. But a couple of researchers think they have solved the pesky paradox problem.

September 25, 2020September 25, 2020 by Brian Koberlein

The Shadow from M87’s Supermassive Black Hole has Been Observed Wobbling Around the Galaxy for Years

The history of the EHT and the images they captured. Credit: M. Wielgus, D. Pesce & the EHT Collaboration

In April 2019, the Event Horizon Telescope (EHT) released the first direct image of a black hole. It was a radio image of the supermassive black hole in the galaxy M87. Much of the image resulted from radio light gravitationally focused toward us, but there was also some light emitted by gas and dust near the black hole. By itself, the image is a somewhat unimpressive blurry ring, but the data behind the image tells a more detailed story.

September 22, 2020September 22, 2020 by Brian Koberlein

The Destruction of Dark Matter isn’t Causing Extra Radiation at the Core of the Milky Way

Artist rendering of possible dark matter emissions from the Milky Way. Credit: Christopher Dessert, Nicholas L. Rodd, Benjamin R. Safdi, Zosia Rostomian (Berkeley Lab)

There are times when it feels like dark matter is just toying with us. Just as we gather evidence that hints at one of its properties, new evidence suggests otherwise. So it is with a recent work looking at how dark matter might behave in the center of our galaxy.

September 17, 2020September 17, 2020 by Brian Koberlein

Colliding Neutron Stars Don’t Make Enough Gold to Explain What We See in the Universe

gamma-ray burst from neutron star merger — Artist rendering of colliding neutron stars. Credit: Robin Dienel/Carnegie Institution for Science

In the beginning, the universe created three elements: hydrogen, helium, and lithium. There isn’t much you can do with these simple elements, other than to let gravity collapse them into stars, galaxies, and black holes. But stars have the power of alchemy. Within their hearts, they can fuse these elements into new ones. Carbon, nitrogen, oxygen, and others, all up to the heavy element of iron. When these first stars exploded, they scattered the new elements across the cosmos, creating planets, new stars, and even us.

September 14, 2020September 14, 2020 by Brian Koberlein

Small Amounts of Dark Matter are Creating Much Stronger Gravitational Distortions than Anyone Expected to See

A mosaic of telescopic images showing the galaxies of the Virgo Supercluster. Credit: NASA/Rogelio Bernal Andreo

Dark matter is difficult for astronomers to study, but that doesn’t keep them from trying. And with skill and determination, they continue to find exciting things about the invisible stuff.