"Because this microquasar happened to be relatively close to the Earth, we were able to track its motion with the VLBA even though it's normally faint," said Mirabel. "Now, we want to find more of these ancient black holes. There must be hundreds of thousands swirling around in our Galaxy."
The astronomers used the VLBA to observe XTE J1118+480 in May and July of 2000, using the VLBA's great resolving power, or ability to see fine detail, to precisely measure the object's movement against the backdrop of more-distant celestial bodies.
"With the VLBA, we could start observing soon after this object was discovered and get extremely precise information on its position. Then, we were able to use the digitized data from the Palomar surveys to extend backward the time span of our information. This is a great example of applying multiple tools of modern astronomy — telescopes covering different wavelengths and digital databases — to a single problem," said Dhawan.
In addition to Mirabel and Dhawan, the research was performed by Roberto Mignani of the European Southern Observatory; Irapuan Rodrigues, who is a fellow of the Brazilian National Research Council at the French Atomic Energy Commission; and Fabrizia Guglielmetti of the Space Telescope Science Institute in Baltimore, MD.
The National Radio Astronomy Observatory is a facility of the National Science Foundation, operated under cooperative agreement by Associated Universities, Inc.