Space and astronomy news
In the beginning, the Universe was all primordial gas. Somehow, some of it was swept up into supermassive black holes (SMBHs), the gargantuan singularities that reside at the heart of galaxies. The details of how that happened and how SMBHs accumulate mass are some of astrophysics’ biggest questions.
Continue reading “Black Holes Dominate Large Regions of Space, But They’re Mysterious”
There’s no perfect way of doing anything, including searching for exoplanets. Every planet-hunting method has some type of bias. We’ve found most exoplanets using the transit method, which is biased toward larger planets. Larger planets closer to their stars block more light, meaning we detect large planets transiting in front of their stars more readily than we detect small ones.
That’s a problem because some research says that life-supporting planets are more likely to be small, like Earth. It’s all because of moons and streaming instability.
Continue reading “If We Want To Find Life-Supporting Worlds, We Should Focus on Small Planets With Large Moons”
At the heart of large galaxies like our Milky Way, there resides a supermassive black hole (SMBH.) These behemoths draw stars, gas, and dust toward them with their irresistible gravitational pull. When they consume this material, there’s a bright flare of energy, the brightest of which are quasars.
While astrophysicists think that SMBHs eat too slowly to cause a particular type of quasar, new research suggests otherwise.
Continue reading “Gluttonous Black Holes Eat Faster Than Thought. Does That Explain Quasars?”
When you think of a black hole, you might think its defining feature is its event horizon. That point of no return not even light can escape. While it’s true that all black holes have an event horizon, a more critical feature is the disk of hot gas and dust circling it, known as the accretion disk. And a team of astronomers have made the first direct measure of one.
Continue reading “Astronomers Precisely Measure a Black Hole's Accretion Disk”
Did humanity miss the party? Are SETI, the Drake Equation, and the Fermi Paradox all just artifacts of our ignorance about Advanced Life in the Universe? And if we are wrong, how would we know?
A new study focusing on black holes and their powerful effect on star formation suggests that we, as advanced life, might be relics from a bygone age in the Universe.
Continue reading “Advanced Life Should Have Already Peaked Billions of Years Ago”
Have you heard of LU Camelopardalis, QZ Serpentis, V1007 Herculis and BK Lyncis? No, they’re not members of a boy band in ancient Rome. They’re Cataclysmic Variables, binary stars that are so close together one star draws material from its sibling. This causes the pair to vary wildly in brightness.
Can planets exist in this chaotic environment? Can we spot them? A new study answers yes to both.
Continue reading “Astronomers Have a New Way to Find Exoplanets in Cataclysmic Binary Systems”
When it comes to observing protoplanetary disks, the Atacama Large Millimetre/sub-millimetre Array (ALMA) is probably the champion. ALMA was the first telescope to peer inside the almost inscrutable protoplanetary disks surrounding young stars and watch planets forming. ALMA advanced our understanding of the planet-forming process, though our knowledge of the entire process is still in its infancy.
According to new observations, it looks like chaos and disorder are part of the process. Astronomers using ALMA have watched as a star got too close to one of these planet-forming disks, tearing a chunk away and distorting the disk’s shape.
What effect will it have on planetary formation?
Continue reading “A Star Passed too Close and Tore Out a Chunk of a Protoplanetary Disk”
Black holes are one of the most awesome and mysterious forces in the Universe. Originally predicted by Einstein’s Theory of General Relativity, these points in spacetime are formed when massive stars undergo gravitational collapse at the end of their lives. Despite decades of study and observation, there is still much we don’t know about this phenomenon.
For example, scientists are still largely in the dark about how the matter that falls into orbit around a black hole and is gradually fed onto it (accretion disks) behave. Thanks to a recent study, where an international team of researchers conducted the most detailed simulations of a black hole to date, a number of theoretical predictions regarding accretion disks have finally been validated.
Continue reading “Black Hole Simulation Solves a Mystery About Their Accretion Disks”
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Polar jets are often found around objects with spinning accretion disks – anything from newly forming stars to ageing neutron stars. And some of the most powerful polar jets arise from accretion disks around black holes, be they of stellar or supermassive size. In the latter case, jets emerging from active galaxies such as quasars, with their jets roughly orientated towards Earth, are called blazars.
The physics underlying the production of polar jets at any scale is not completely understood. It is likely that twisting magnetic lines of force, generated within a spinning accretion disk, channel plasma from the compressed centre of the accretion disk into the narrow jets we observe. But exactly what energy transfer process gives the jet material the escape velocity required to be thrown clear is still subject to debate.
In the extreme cases of black hole accretion disks, jet material acquires escape velocities close to the speed of light – which is needed if the material is to escape from the vicinity of a black hole. Polar jets thrown out at such speeds are usually called relativistic jets.
Relativistic jets from blazars broadcast energetically across the electromagnetic spectrum – where ground based radio telescopes can pick up their low frequency radiation, while space-based telescopes, like Fermi or Chandra, can pick up high frequency radiation. As you can see from the lead image of this story, Hubble can pick up optical light from one of M87‘s jets – although ground-based optical observations of a ‘curious straight ray’ from M87 were recorded as early as 1918.
A recent review of high resolution data obtained from Very Long Baseline Interferometry (VLBI) – involving integrating data inputs from geographically distant radio telescope dishes into a giant virtual telescope array – is providing a bit more insight (although only a bit) into the structure and dynamics of jets from active galaxies.
The radiation from such jets is largely non-thermal (i.e. not a direct result of the temperature of the jet material). Radio emission probably results from synchrotron effects – where electrons spun rapidly within a magnetic field emit radiation across the whole electromagnetic spectrum, but generally with a peak in radio wavelengths. The inverse Compton effect, where a photon collision with a rapidly moving particle imparts more energy and hence a higher frequency to that photon, may also contribute to the higher frequency radiation.
Anyhow, VLBI observations suggest that blazar jets form within a distance of between 10 or 100 times the radius of the supermassive black hole – and whatever forces work to accelerate them to relativistic velocities may only operate over the distance of 1000 times that radius. The jets may then beam out over light year distances, as a result of that initial momentum push.
Shock fronts can be found near the base of the jets, which may represent points at which magnetically driven flow (Poynting flux) fades to kinetic mass flow – although magnetohydrodynamic forces continue operating to keep the jet collimated (i.e. contained within a narrow beam) over light year distances.
That was about as much as I managed to glean from this interesting, though at times jargon-dense, paper.
Further reading: Lobanov, A. Physical properties of blazar jets from VLBI observations.
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Excellent teamwork by astronomers working in two different wavebands – x-ray and optical – has led to the discovery of a binary quasar being created by a pair of merging galaxies.
“This is really the first case in which you see two separate galaxies, both with quasars, that are clearly interacting,” says Carnegie astronomer John Mulchaey who made observations crucial to understanding the galaxy merger.
“The model verifies the merger origin for this binary quasar system,” Thomas Cox, now a fellow at the Carnegie Observatories, says, referring to computer simulations of the merging galaxies he produced. When Cox’s model galaxies merged, they showed features remarkably similar to what Mulchaey observed in the Magellan images. “It also hints that this kind of galaxy interaction is a key component of the growth of black holes and production of quasars throughout our universe,” Cox added.
“Just because you see two galaxies that are close to each other in the sky doesn’t mean they are merging,” says Mulchaey. “But from the Magellan images we can actually see tidal tails, one from each galaxy, which suggests that the galaxies are in fact interacting and are in the process of merging.”
As Universe Today readers know, quasars are the extremely bright centers of galaxies surrounding supermassive black holes, and binary quasars are pairs of quasars bound together by the mutual gravitation of the two host galaxies’ nuclei. Binary quasars, like other quasars, are thought to be the product of galaxy mergers. Until now, however, binary quasars have not been seen in galaxies that are unambiguously in the act of merging. But images of a new binary quasar from the Carnegie Institution’s Magellan telescope in Chile show two distinct galaxies with tails produced by tidal forces from their mutual gravitational attraction.
Supermassive black holes are to be found in the nuclei of most, if not all, large galaxies, such as our galaxy the Milky Way. Because galaxies regularly interact and merge, astronomers have concluded that binary supermassive black holes have been common in the Universe, especially during its early history (when galaxy mergers were far more common). Supermassive black holes can only be detected as quasars – which are one kind of highly luminous active galactic nucleus (AGN) – when they are actively accreting matter, a process that releases vast amounts of energy across the entire electromagnetic spectrum. A leading theory of ordinary AGNs is that galaxy mergers trigger accretion, creating quasars in both galaxies (AGNs in the hearts of the giant elliptical galaxies in rich clusters are thought to be fueled by a different mechanism, cooling flow). Because most such mergers would have happened in the distant past, binary quasars and their associated galaxies are very far away and therefore difficult for most telescopes to resolve.
The binary quasar, named SDSS J1254+0846, was initially detected by the Sloan Digital Sky Survey, a multi-year, large scale astronomical survey of galaxies and quasars. Further observations by Paul Green of the Harvard-Smithsonian Center for Astrophysics and colleagues using NASA’s Chandra’s X-ray Observatory and telescopes at Kitt Peak National Observatory in Arizona and Palomar Observatory in California strongly suggest that the object was likely a binary quasar in the midst of a galaxy merger. Carnegie’s Mulchaey then used the 6.5 meter Baade-Magellan telescope at the Las Campanas observatory in Chile to obtain deeper images and more detailed spectroscopy of the merging galaxies.
The Astrophysical Journal paper on this object is: “SDSS J1254+0846: A Binary Quasar Caught in the Act of Merging” (Paul J. Green et al 2010 ApJ 710 1578-1588; arXiv:1001.1738 is the preprint).
Source: Carnegie Institution for Science