India’s space telescope, AstroSat, has achieved a significant milestone by measuring X-ray polarization from the Cygnus X-1 black hole. This accomplishment, reported in a scientific article in Astrophysical Journal Letters, marks the first time such measurements have been made, providing new insights into the study of the black hole’s environment.
Significance of X-ray Polarization
Normal X-ray measurements typically reveal the energy or intensity of radiations. However, the polarization characteristics of X-rays, indicating the orientation of the oscillating electric field, offer valuable clues about the geometry and other properties of the black hole.
Challenging Task and Collaborative Efforts
Lead author Dr. Tanmoy Chattopadhyay from Stanford University describes the measurement as an extremely challenging task, with contributions from multiple Indian institutes. The Cadmium Zinc Telluride Imager (CZTI), one of the five scientific instruments on AstroSat, played a crucial role in making these measurements.
Mechanism of Radiation Production
The CZTI measurements bring scientists closer to unraveling the mechanism of radiation production in black holes. The study connects hard X-ray radiation to the black hole jet, addressing an open question in the astrophysics community regarding the emissions of high-energy X-rays from a black hole jet.
Polarization and Photon Properties
Prof Gulab Dewangan from Inter-University Centre for Astronomy and Astrophysics (IUCAA) emphasizes the importance of polarization as one of the properties that a photon carries. It provides information about the orientation of the oscillating electric field, revealing details about the accelerating charged particle emitting the light.
Decade-long Effort and Development
Scientists invested nearly 10-12 years in developing the necessary tools to use data from AstroSat and measure the polarization of Cygnus X-1 in X-rays. The launch of AstroSat by the Indian Space Research Organisation (ISRO) in September 2015 marked a crucial step in this scientific endeavor.
High Polarization Measurement
Dr. Chattopadhyay explains that the measurements show high polarization in the 100-380 keV energy range, suggesting that radiation above 100 keV likely originated from the black hole jet.
Cygnus X-1 Background
Cygnus X-1, discovered over four decades ago, is one of the first confirmed black hole systems in our galaxy. It is located at a distance approximately 400 times greater than the distance between Earth and the Sun. The black hole is twenty times heavier than the Sun and forms a binary system with a companion supergiant star.
Multiple Choice Questions (MCQs):
1. What is the significance of measuring X-ray polarization from the Cygnus X-1 black hole?
a. Revealing the distance from Earth
b. Providing insights into the black hole’s environment
c. Determining the age of the black hole
d. Identifying the color of X-ray radiation
Answer: b. Providing insights into the black hole’s environment
2. Which instrument on AstroSat played a crucial role in making the X-ray polarization measurements?
a. Ultraviolet Spectrometer
b. Cadmium Zinc Telluride Imager (CZTI)
c. Soft X-ray Telescope
d. Large Area X-ray Proportional Counter (LAXPC)
Answer: b. Cadmium Zinc Telluride Imager (CZTI)
3. What information does polarization of light in X-ray wavelengths provide?
a. Distance from Earth
b. Acceleration of charged particles
c. Orientation of the oscillating electric field
d. Temperature of the black hole
Answer: c. Orientation of the oscillating electric field
4. How long did scientists invest in developing tools to measure X-ray polarization from Cygnus X-1?
a. 5-7 years
b. 8-10 years
c. 12-15 years
d. 20 years
Answer: b. 8-10 years