Special relativity aces time trial
'Time dilation' predicted by Einstein confirmed by lithium ion experiment.
Physicists have verified a key prediction of Albert Einstein’s special theory of relativity with unprecedented accuracy. Experiments at a particle accelerator in Germany confirm that time moves slower for a moving clock than for a stationary one.
The work is the most stringent test yet of this ‘time-dilation’ effect, which Einstein predicted. One of the consequences of this effect is that a person travelling in a high-speed rocket would age more slowly than people back on Earth.
The history of the Milky Way has a new wrinkle.
Scientists used radio telescopes like the Atacama Large Millimeter/submillimeter Array — a vast array of receivers in Chile — used to probe galaxies within 40 million to 600 million light-years from Earth. After observing dozens of merging galaxies, astrophysics found that many galactic collisions will create disc galaxies similar to the Milky Way, a surprising finding.
Their observations of carbon monoxide in 37 colliding galaxies showed pancake-shaped zones of molecular gas, similar to the shape that disc galaxies — which include spiral galaxies and lenticular galaxies — would assume.
"This is a large and unexpected step towards understanding the mystery of the birth of disc galaxies," lead researcher on the study Junko Ueda, a postdoctoral fellow at the Japan Society for the Promotion of Science, said in a European Southern Observatory statement.
Before, astronomers thought that only elliptical galaxies could arise from mergers. Simulations from the 1970s, however, concluded that elliptical galaxies should be the most popular type of galaxy in the universe. Yet these odd-shaped entities comprise less than 30 percent of galaxies. The new study could help explain why scientists see so many spiral galaxies like the Milky Way in the universe, according to ESO.
The astronomers’ work is the biggest molecular gas study so far, but they said they plan more work to follow up on their research. Astronomers emphasized more observations of older galaxies are required to see if mergers behaved similarly in the young universe.
"We have to start focusing on the formation of stars in these gas discs. Furthermore, we need to look farther out in the more distant universe," Ueda said. "We know that the majority of galaxies in the more distant universe also have discs. We, however do not yet know whether galaxy mergers are also responsible for these, or whether they are formed by cold gas gradually falling into the galaxy. Maybe we have found a general mechanism that applies throughout the history of the universe."
The research was published in the Astrophysical Journal Supplement.
There’s a gas giant located about 330 light-years from here that’s not only unusually large, it’s also orbiting its host star at an incredibly close distance. According to a new study, this combination of factors is wreaking havoc on the star’s innards.
The exoplanet is named WASP-18b and it’s about 10 times heavier than Jupiter. So this thing is absolutely huge. Not only that, it’s so close to its parent star, WASP-18, that it completes one single orbit in less than 23 hours. It’s one of the most extreme examples of a hot Jupiter that scientists have ever seen.
A team led by Ignazio Pillitteri of the Istituto Nazionale di Astrofisica (INAF)-Osservatorio Astronomico di Palermo in Italy dated WASP-18 between 500 million and 2 billion years old. That’s young by cosmological standards. By comparison, our sun, which is at its mid-life, is about 5 billion years old.
But here’s the thing: Younger stars tend to be more active, spewing out stronger magnetic fields, larger flares, and more intense X-ray emissions than their older counterparts. That’s why things are weird with WASP-18. The Chandra X-Ray Observatory explains:
Magnetic activity, flaring, and X-ray emission are linked to the star’s rotation, which generally declines with age. However, when astronomers took a long look with Chandra at WASP-18 they didn’t detect any X-rays. Using established relations between the magnetic activity and X-ray emission of stars, as well as its actual age, researchers determined WASP-18 is about 100 times less active than it should be.
"We think the planet is aging the star by wreaking havoc on its innards," said co-author Scott Wolk of the Harvard-Smithsonian Center for Astrophysics in Cambridge, Massachusetts.
The researchers argue that tidal forces created by the gravitational pull of the massive planet – similar to those the moon has on Earth’s tides, but on a much larger scale – may have disrupted the magnetic field of the star. [emphasis added]
The strength of the magnetic field depends on the amount of convection in the star, or how intensely hot gas stirs the interior of the star.
"The planet’s gravity may cause motions of gas in the interior of the star that weaken the convection," said co-author Salvatore Sciortino also of INAF-Osservatorio Astronomico di Palermo in Italy. "This has a domino effect that results in the magnetic field becoming weaker and the star to age prematurely."
WASP-18 is particularly vulnerable to the impact of tidal forces owing to its convection zone, which is narrower than most stars.
Read the entire study at the pre-print journal arXiv: “No X-rays from WASP-18. Implications for its age, activity, and the influence of its massive hot Jupiter”.
Image: X-ray: NASA/CXC/SAO/I.Pillitteri et al; Optical: DSS; Illustration: NASA/CXC/M.Weiss
the center holds
|—||Richard Feynman (via galaxyclusters)|
Hubble Helps Astronomers Find Smallest Known Galaxy With Supermassive Black Hole
Astronomers using the NASA/ESA Hubble Space Telescope have found a monster lurking in a very unlikely place.
New observations of the ultracompact dwarf galaxy M60-UCD1 have revealed a supermassive black hole at its heart, making this tiny galaxy the smallest ever found to host a supermassive black hole.
This suggests that there may be many more supermassive black holes that we have missed, and tells us more about the formation of these incredibly dense galaxies. The results will be published in the journal Nature on 18 September 2014.
Lying about 50 million light-years away, M60-UCD1 is a tiny galaxy with a diameter of 300 light-years — just 1/500th of the diameter of the Milky Way. Despite its size it is pretty crowded, containing some 140 million stars. While this is characteristic of an ultracompact dwarf galaxy (UCD) like M60-UCD1, this particular UCD happens to be the densest ever seen.
Despite their huge numbers of stars, UCDs always seem to be heavier than they should be. Now, an international team of astronomers has made a new discovery that may explain why — at the heart of M60-UCD1 lurks a supermassive black hole with the mass of 20 million Suns.
"We’ve known for some time that many UCDs are a bit overweight. They just appear to be too heavy for the luminosity of their stars," says co-author Steffen Mieske of the European Southern Observatory in Chile. "We had already published a study that suggested this additional weight could come from the presence of supermassive black holes, but it was only a theory. Now, by studying the movement of the stars within M60-UCD1, we have detected the effects of such a black hole at its centre. This is a very exciting result and we want to know how many more UCDs may harbour such extremely massive objects."
The supermassive black hole at the centre of M60-UCD1 makes up a huge 15 percent of the galaxy’s total mass, and weighs five times that of the black hole at the centre of the Milky Way. “That is pretty amazing, given that the Milky Way is 500 times larger and more than 1000 times heavier than M60-UCD1,” explains Anil Seth of the University of Utah, USA, lead author of the international study. “In fact, even though the black hole at the centre of our Milky Way galaxy has the mass of 4 million Suns it is still less than 0.01 percent of the Milky Way’s total mass, which makes you realise how significant M60-UCD1’s black hole really is.”
A Black Hole Doesn’t Die — It Does Something A Lot Weirder
Black holes are basically “game over, man,” for anything that gets too close to them, but they aren’t invincible. In fact, they’re always in the process of self-destructing. We’ll look at how they fizzle out, and see if we can help them do it faster.
The Event Horizon
Realistically speaking, you are dead as soon as you get anywhere near a black hole. You’ll be snapped like a rubber band by the differences in the gravitational pull on your top and bottom half, or you’ll be fried by radiation (more on that later). No one in the foreseeable future (even if we try to foresee multiple millennia into the future) will get close to a black hole. Pass the event horizon, however, and you don’t even have an unforeseeable future. Once material gets beyond the event horizon, it’s being pulled into the black hole with such force that it doesn’t escape. Not even light gets out. Once something has gone beyond the event horizon, it no longer really “counts” as part of the universe anymore.