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One of the most pressing questions in astronomy concerns black holes. We know that massive stars that explode as supernovae can leave stellar mass black holes as remnants. And astrophysicists understand that process. But what about the supermassive black holes (SMBHs) like Sagittarius A-star (Sgr A*,) at the heart of the Milky Way?

SMBHs can have a billion solar masses. How do they get so big?

A group of scientists at the Harvard Center for Astrophysics are trying to shed some light on that question. They’ve created a simulation as part of the Black Hole Initiative (BHI), an interdisciplinary effort at Harvard to advance the understanding of black holes.

Astronomers announced the discovery of a ghostly, almost perfectly circular, arc of ultraviolet emission centered on the handle of the Big Dipper and stretching 30 degrees across the Northern sky. If the arc were extended, it would completely encircle the Big Dipper with a diameter of 60 degrees.

This unique object was discovered by Andrea Bracco, an astronomer at the Ruđer Bošković Institute in Zagreb, Croatia, Marta Alves, an astronomer at Radboud University in the Netherlands, and Robert Benjamin, a professor of physics and astronomy at the University of Wisconsin-Whitewater in the United States. Benjamin, who contributed to the analysis of the structure, presented the team’s newest results at an on-line meeting of American Astronomical Society on June 2. A report on the discovery has been published in the April volume of Astronomy & Astrophysics Letters.

The arc, stretching beyond the constellation Ursa Major, is 30 degrees long, a fraction of a degree thick, and made of compressed, energized interstellar gas. The source of the energy and the arc shape indicate an advancing shock wave from a stellar explosion or supernova which occurred 60 degrees above the plane of the Milky Way Galaxy. The distance and age of the explosion which created the shock wave is highly uncertain. The team estimates that the explosion occurred more than 100,000 years ago at a distance of approximately 600 light years.

For more than six decades, the quest to understand the formation of hot (about 20,000−30,000 K) extreme horizontal branch (EHB) stars in Galactic globular clusters has remained one of the most elusive in stellar evolutionary theory. Here we report on two discoveries that challenge the idea of the stable luminosity of EHB stars. The first mode of EHB variability is periodic and cannot be ascribed to either binary evolution or pulsation. Instead, we attribute it here to the presence of magnetic spots: superficial chemical inhomogeneities whose projected rotation induces the variability. The second mode of EHB variability is aperiodic and manifests itself on timescales of years. In two cases, six-year-long light curves display superflare events that are several million times more energetic than solar analogues. We advocate a scenario in which the two EHB variability phenomena are different manifestations of diffuse, dynamo-generated, weak magnetic fields. Magnetism is therefore a key player driving the formation and evolution of EHB clusters stars and, likewise, operating in the Galactic field counterparts. Our conclusions bridge similar variability/magnetism phenomena in all radiative-enveloped hot-stars: young main-sequence stars, old EHBs and defunct white dwarfs.

More than three-quarters of the baryonic content of the Universe resides in a highly diffuse state that is difficult to detect, with only a small fraction directly observed in galaxies and galaxy clusters^1,2. Censuses of the nearby Universe have used absorption line spectroscopy^3,4 to observe the ‘invisible’ baryons, but these measurements rely on large and uncertain corrections and are insensitive to most of the Universe’s volume and probably most of its mass. In particular, quasar spectroscopy is sensitive either to the very small amounts of hydrogen that exist in the atomic state, or to highly ionized and enriched gas^4,5,6 in denser regions near galaxies⁷. Other techniques to observe these invisible baryons also have limitations; Sunyaev–Zel’dovich analyses^8,9 can provide evidence from gas within filamentary structures, and studies of X-ray emission are most sensitive to gas near galaxy clusters^9,10. Here we report a measurement of the baryon content of the Universe using the dispersion of a sample of localized fast radio bursts; this technique determines the electron column density along each line of sight and accounts for every ionized baryon^11,12,13. We augment the sample of reported arcsecond-localized^{14,15,16,17,18} fast radio bursts with four new localizations in host galaxies that have measured redshifts of 0.291, 0.118, 0.378 and 0.522. This completes a sample sufficiently large to account for dispersion variations along the lines of sight and in the host-galaxy environments¹¹, and we derive a cosmic baryon density of \({\varOmega }_{{\rm{b}}}={0.051}_{-0.025}^{+0.021}{h}_{70}^{-1}\) (95 per cent confidence; h₇₀ = H₀/(70 km s⁻¹ Mpc⁻¹) and H₀ is Hubble’s constant). This independent measurement is consistent with values derived from the cosmic microwave background and from Big Bang nucleosynthesis^19,20.

Physicists are figuring out how close you can get to a black hole before you are unlikely to escape. That threshold is called the innermost stable circular orbit (ISCO).

Black holes, regions in space with such an intense gravitational field that no matter or radiation can escape from them, are among the most mysterious and fascinating cosmological phenomena. Over the past five years or so, astrophysicists collected the first observations of the strong gravitational forces around black holes.

The LIGO-Virgo collaboration was able to detect gravitational waves around these celestial objects using some of the most advanced gravitational-wave detectors in the world. Meanwhile, the Event Horizon Telescope research group captured the very first image of a black hole shadow.

While both these observations are highly promising and captivating, neither of them is likely to unveil the event horizon, the boundary defining the specific region in space around a black hole from which nothing can escape. Nonetheless, they should contain a signature pointing to a neighboring region just outside of the event horizon, wherein light is bent so strongly that its path closes over itself and forms circular orbits known as light rings.

Could the mysterious particle be our window into studying dark matter?

The Dark matter engine is the key to the extreme acceleration capabilities of the modern space ship. Invented by Professor Hubert J. Farnsworth, the engines on the Planet Express ship harness the power created by burning dark matter in large furnaces, channels it through an afterburner that gives 200% fuel efficiency and propelles the ship through space fast enough to cover the whole universe in a matter of days.

How it works Edit

Let’s look at the real universe example of Rigel, a star in Orion’s Belt approximately 900 light-years away from Earth. This means that even traveling at the speed of light (300,000 km/s) it would take 900 years to get there. Traveling at 9 times the speed of light (2,700,000 km/s) it would take 100 years to get there and at 100 times the speed of light (30,000,000 km/s) it would take nine years. Albert Einstein’s famous statements that it would be mathematically impossible to travel faster than light seem to have held up through out the 3rd millennia and although in 2208 the scientific community allegedly raised the speed of light so that they could go faster, the problem that one cannot go faster than the speed of light remains.

Einstein’s equations describe three canonical configurations of space-time. Now one of these three — important in the study of quantum gravity — has been shown to be inherently unstable.