June 6, 2020

Astro-Challenge: Spy a Microquasar.

So, you’ve seen everything the night sky has to offer? You say you’ve seen all breeds of eclipses and deep sky objects, and have grown tired of showing the neighbors Saturn and the Ring Nebula? Well, we’ve got a challenge for you. This week’s object will require dark skies, a good finder chart, and a generous aperture telescope.  About 4 degrees northwest of the 3rd magnitude star Delta Aquilae lies +14.1 magnitude SS 433.

At about the same brightness as Pluto, this star like point amid a star rich field belies its truly amazing nature. Discovered in 1977 by Sanduleak and Stephenson during a routine survey, something was immediately noticed as odd about the system; spectral shifts were alternately blue and red shifted, to a degree of about 16% the speed of light. The system was also embedded in the supernova remnant W50, and clearly located within our galaxy about an estimated 18,000 light years distant. The system is also the source of a copious amount of X-rays… just what could create a star that’s both coming and going? Astrophysicists believe that SS 433 is a microquasar, one of the first ever discovered. The pair consists an 11 solar mass type A star orbiting either a neutron star, or more than likely, a black hole. The simultaneous motion is due to alternating jets of matter streaming away and towards us from the poles. How can anything escape a black hole? Well, don’t forget that while the black hole may be collapsed to an infinitely small point, it still retains its signature mass; the Schwarzschild radius merely defines the region within which the escape velocity exceeds the speed of light… beyond those bounds, escape is still fair game. The polar jets are inclined about 79 degrees to our line of sight,   and the relativistic jets precess over a period of about 163 days. The system is a radio and x-ray eclipsing binary, and has been much studied by the Chandra and Arecibo telescopes due to its proximity compared to extra-galactic quasars. Of course, don’t expect SS 433 to look like anything more than a faint star; this is one of those challenges where knowing the true nature of what you’re looking at is part of the fun. The AAVSO has excellent finder charts and the position of SS 433 is;

R.A.: 19H 11’ 50”

Dec: +04 58’ 58”

Good Luck!

This week’s Astroword is, you guessed it, Microquasar. A microquasar shares the same characteristics of their more massive extragalactic cousins, namely a large accretion disk surrounding an ultra-compact massive object accompanied by relativistic radio and x-ray jets. But while traditional quasars house sources in the millions of solar mass variety and can be seen half way across our galaxy, microquasars contain black holes of the stellar mass variety and are known to exist within our galaxy. SS 433 was the first such beastie discovered, and other known microquasars included GRS 1915+105 and the infamous (cue Rush music) Cygnus X-1. Microquasars are sometimes also interchangeably known as radio-jet x-ray binaries.


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