An international team of scientists has observed four super-massive black holes at the center of galaxies, which may provide new information on how these central black hole systems operate.
Their findings are published in December’s first issue of the journal Astronomy and Astrophysics.
These super-massive black holes at the center of galaxies are called active galactic nuclei. For the first time, the team observed a quasar with an active galactic nucleus, as part of the group of four, which is located more than a billion light years from Earth. The scientists used the two Keck telescopes on top of Mauna Kea in Hawaii. These are the largest optical/infrared telescopes in the world.
The team also used the United Kingdom Infrared Telescope (UKIRT) to follow up the Keck observations, to obtain current near-infrared images of the target galaxies.
“Astronomers have been trying to see directly what exactly is going on in the vicinity of these accreting super-massive black holes,” said co-author Robert Antonucci, a UC Santa Barbara astrophysicist.
He explained that the nuclei of many galaxies show intense radiation from X-ray to optical, infrared, and radio, where the nucleus may exhibit a strong jet — a linear feature carrying particles and magnetic energy out from a central super-massive black hole. Scientists believe these active nuclei are powered by accreting super-massive black holes. The accreting gas and dust are especially bright in the optical and infrared regions of the electromagnetic spectrum.
Read more at: ScienceDaily
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Galaxies rotate. Each of them would fly apart and create a cosmic mess, were it not for the gravitational forces that bind together the many billions of stars and large quantities of dust and gas that constitute a typical galaxy like our Milky Way.
By applying Newton’s law of gravity to the observed mass distribution of the galaxies, we can predict the rotation curve for each galaxy. If we do this, and compare the derived rotation curves to the observed rotational velocities, it becomes apparent that galaxies rotate much faster than predicted based on the gravitational attraction from the visible mass. This means that the matter within a galaxy is bonded together much stronger than expected. These deviations are very significant. Detailed comparisons between observed and calculated rotation rates reveal that the bonding of matter in galaxies is about six times stronger than expected. This means that either Newton’s law of gravity fails dramatically at galactic distances, or that large quantities of some invisible (‘dark’) matter are present.
The physics community has predominantly opted for the latter conjecture. An easy way out that leaves Newton’s venerable theories intact. This, however, might start to change.
Read more at: Scientific Blogging | The Hammock Physicist
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{Photography © 2009 by Toscana Enterprises Corporation, all rights reserved}
MIT students build a high-altitude, photo-snapping balloon using off-the-shelf components
Scientists and students alike have previously launched low-budget balloons that rise to the upper reaches of Earth’s atmosphere, snapping unbelievable photos from near-space. But MIT’s Icarus team managed the same feat using only off-the-shelf items, and for a measly cost of $150. Here’s how they did it.
The MIT students list everything that they used to assemble the launch vehicle, including a prepaid Motorola i290 phone with GPS, a cell phone charger and disposable hand warmers to keep everything operable at the cold high altitudes. Basic materials such as newspaper, zip ties, duct tape and a Styrofoam beer cooler also came in handy.
“We bought a AA-battery cell phone charger to sustain the phone’s power over the duration of the flight, and we used Energizer lithium batteries (rated to operate at temperatures are low as -40F) to power both this charger as well as our camera,” the Icarus team wrote on their website.
Read more at: popsci.com
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{Photography by Hashmil}
