Scientists have discovered the closest black hole yet, a mere 1, 600 light years from Earth. At the peak of its X-ray output, V 4641 Sgr was the brightest X-ray emitter in the sky. Astronomers call this type of system an X-ray nova because it suddenly becomes a bright source of X-rays, but this object shows characteristics never seen in an X-ray nova. Smith worked on data from this object with MIT principal research scientist Ronald Re millard and NRAO astronomer Robert Hjellming. Black holes harbor enormous gravitational force that can literally rip the gas away from a nearby star.
Both orbiting X-ray telescopes and ground-based radio and optical telescopes saw the outburst of V 4641 Sgr. The radio observations revealed the presence of a jet escaping from the system at mind-boggling speeds. Micro quasar activity is thought to arise when the black hole in the binary system draws material away from its companion star. The material surrounding the black hole forms a rapidly spinning disk called an accretion disk. Kato forwarded the message to Smith, a member of the All-Sky Monitor (ASM) team using the Rossi X-ray Timing Explorer (RXTE) satellite. Subsequent observations showed the rapid rise and fall of the object’s X-ray brightness.
Other radio telescopes observing the object were NRAO’s Green Bank Interferometer in West Virginia; the Australia Telescope Compact Array; the Molonglo Observatory Synthesis Telescope, also in Australia; the MERLIN array in Britain; the Ratan 600-meter radio telescope in Russia; and radio telescopes at the Owens Valley Radio Observatory in California. The radio observations also provided the distance measurement for the binary system. The dramatic X-ray flare on Sept. 15 was not the only time V 4641 Sgr exploded into activity. In addition to the flares seen by the ASM, they found a third rapid flare that peaked two hours after the brightest flare, reaching a peak intensity about half that of the brightest flare. The RXTE Proportional Counter Array (PCA), a very large X-ray telescope, was rapidly reoriented to observe V 4641 Sgr about 4.
The Essay on Television and Radio
Isn’t it amazing that people who lived two hundred years ago didn’t have radios or televisions? Today it is difficult to imagine life without these two forms of communication. These technological wonders have many similar characteristics. As you will see, they are also quite different. To start with, both radios and televisions need a source of power in order to run. If you have no electric socket ...
5 hours after the brightest flare.
