L.L. syzygia • Gk. syzygia "yoke, pair, union of two, conjunction" • syzygein "yoke together"
Recent events with interesting connections to other things got my attention. See if you agree. |
This is a diary about the connection between a radio telescope near my home and the recent findings about a black hole. The first piece of this syzygy is in the center of this picture. It is a 25 meter diameter radio telescope. It is nearly in my backyard 4 miles away. It's part of the
VLBA Very Long Baseline Array and is operated by the
U of Iowa Dept. of Physics and Astronomy.
The Very Long Baseline Array (VLBA) comprises ten radio telescopes spanning 5,351 miles. It's the world's largest, sharpest dedicated telescope array. With an eye this sharp, you could be in Los Angeles and clearly read a street sign in New York City. The VLBA is a critical tool for astronomy, where knowing distances is the basis for figuring out mass, makeup, and movement of cosmic objects.
LPeft: zoomed view of the photo above. Right: webcam view last Sunday. A few years ago I got a tour of the telescope with a group of physics teachers when it was shut down. It was pointed straight up. We climbed up the stairs and ladders and emerged through a small trap-door hatch. Standing in the 82 foot parabola with nothing in view but the sky above was a thrill.
The array extends from the
Virgin Islands to Hawaii in the linked map. The 10 telescopes observe the sames objects all at the same time such as blazars, quasars, black holes, dying stars, pulsars, exoplanets, and masers. What these objects have in common is the emission of radio frequency waves. Atomic clocks at each telescope are synchronized. The timing of the reception of the radio signals is then combined to produce a synthesized telescope with a 5,351 miles aperture.
In astronomy, the wider the aperture, the finer the detail that can be resolved.
For more specific information on radio interferometry,
follow this link.
The subject of interest for this syzygy diary is a particular Black Hole in the news last week. This amazing animation from the story depicted what looked like a Cosmic Black Hole fart.
There was a reference to the Black Hole story in this diary by Neon Vincent over the weekend. Because of this close-to-home backyard connection for me, I wanted to expound on it. Join me below for details about the second piece of this syzygy.
Black Hole Accretion Disks and Gas Jets |
In mid-2009, there was an outburst of a binary system known as
H1743–322, located about 28,000 light-years away toward the constellation Scorpius. The system has a normal star and a black hole orbiting each other in a matter of days.
In close arrangements like that, the black hole pulls a stream of matter into it from the star. The flowing gas forms a flattened accretion disk millions of miles across around the black hole. The disk is compressed and heated to tens of millions of degrees and emits X-rays. Some of the matter gets redirected and is emitted as jets streaming away from the black hole following twisted magnetic field lines along the axis of spin. Click on the image for an animation of the process. Dial-up users, you may not want to do that. It is a large file.
The jets normally are a steady flow of particles. Sometimes, they have huge outbursts that throw large gas blobs at significant fractions of the speed of light. The image at the right is the jet directed toward the upper right from object m87. There are some blobs, or knots, of gas seen along the path of the jet.
In early June 2009, H1743–322 underwent a transition ourburst and emitted blobs of gas out in opposite directions while astronomers were watching...
...with RXTE, the VLBA, the Very Large Array near Socorro, N.M., and the Australia Telescope Compact Array (ATCA) near Narrabri in New South Wales. The observatories captured changes in the system's X-ray and radio emissions as the transformation occurred.
From May 28 to June 2, the system's X-ray and radio emissions were fairly steady. RXTE data show that cyclic X-ray variations, known as quasi-periodic oscillations or QPOs, gradually increased in frequency over the same period. On June 4, ATCA measurements showed that the radio emission had faded significantly.
RXTE is the
Rossi X-ray Timing Explorer satellite that observed the high-energy worlds of black holes, neutron stars, X-ray pulsars and bursts of X-rays. After 16 years of amazing discoveries, the RXTE mission was decommissioned on January 5, 2012.
How The Observations Fit Together |
The RXTE spacecraft had observed in the H1743–322 system a 'tell-tale heart', or heartbeat, of x-ray emissions.
The unique feature of this system was how the frequency of the heartbeat had been increasing steadily from May to June 2, 2009. By June 4, 2009, the x-ray feature had stopped.
The heartbeat stopped.
At the same time, astronomers with the VLBA were observing the radio emissions of H1743-322. They were amazed to see the event unfold before their telescopes' eyes.
The same day that the radio emission increased, an extremely detailed VLBA image revealed a bright, radio-emitting bullet of gas moving outward from the system in the direction of one of the jets. On June 6, a second blob, moving away in the opposite direction, was seen.
As you watch the video above the squiggle, the animation shows the circulating material in the accretion disk increasing in frequency as evidenced by the RXTE data. It is followed by the massive ejection of two blobs of gas in opposite directions as evidenced in the VLBA data. For the first time, astronomers have witnessed this kind of event in detail.
Below is a graphic of the final days of the event showing the observations of VLBA across top and RXTE data across the middle on the same dates. The disappearance of the QPOs after June 2 coincides with the formation of the radio emitting blobs detected by VLBA. The third row is the corresponding part of the above video animation. The graphic is small and hard to read. Click on it to see the full sized big jpg from NASA.
Rarely do astronomers get to have multiple instruments trained on the same short duration event. This one played out well. And, it is a significant syzygy for me because it's as if it happened right in my own backyard. I hope you enjoyed it, too.