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There's a microquasar in the neighborhood

The decades of the 1960s and 1970s produced some spectacular astronomical discoveries: in 1963 Dutch astronomer Maarten Schmidt discovered quasars; a year later, U.S. AT&T microwave researchers Arno Penzias and Robert Wilson discovered the Big Bangs cosmic background radiation signature; and in 1978 British astronomer David H. Clarks discovered the first microquasar dubbed SS433. This object is the source for some (not all) of the cosmic X-ray streams that can be detected on Earth.

The word quasar is a contraction of the term quasi-stellar object (or QSO). SS433 displays a lot of the characteristics of larger, more ancient quasars located billions of light years from Earth. SS443located in the constellation of Aquilais, 16,000 light years awaycan be seen as a 14th magnitude star from Earth.

SS433 lies within the region of a hazy supernova remnant; it is an X-ray binary star system consisting of either a black hole or a neutron star and a supergiant sun.

The black hole\Neutron star primary is what remains of the titanic stellar explosion that took place an estimated 10,000 years ago. Both primary and supergiant orbit each other at close range once every 164 days. The black hole\Neutron star emits a massive amount of lethal X-rays, so its of special interest to astronomers.

Why the unromantic name SS433? The microquasar ended up simply being number 433 in an international stellar registry maintained by American astronomers Nicholas Sanduleak and C. Bruce Stephenson (its more formerly called the Stephenson-Sanduleak Astronomical Catalog), The microquasar primary is currently consuming its supergiant companion star; the big sun is being sucked into an accretion disc formed around the microquasar. Spirals on the disk emit high-speed hydrogen gas and those deadly X-rays. The hydrogen/X-ray jets travel at 26 percent of the speed of light!

According to astronomer Bruce Margon of the University of Washington, This star is considered one of the weirdest, considering that the spectrum of the star is shifted not just by Doppler shifts but also by relativity: when the effects of doppler shift are subtracted there is a residual redshifting of 56 million miles per hour (90 million kilometers per hour); this apparent redshifting cannot be travel of the (binary) system since the system would have exited the Milky Way galaxy long ago. The apparent redshifting is then due to time dilation: very fast moving observed clocks in a time-dilated state appear to stationary outside-observers on Earth to be ticking more slowly, in this case the relativistic fast moving excited atoms of the jets appear to vibrate more slowly and are thus red shifted.

While SS433 is close to us by astronomical standards, theres an even closer microquasar, called V4641 Sagittarii; its a mere 1,500 light-years away.

Whats in the Sky: This weekend, look up in the east after sunset for the yellow-orange giant star Arcturus. You cant miss it. This is the brightest star in the night sky this time of year.

Lou Varricchio is a former NASA science writer. He is a member of the NASA/JPL Solar System Ambassador program in Vermont.

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