August 10, 2013
Students Observe Quasar By Looking At Light Reflections
John P. Millis, Ph.D. for redOrbit.com - Your Universe Online
Part of the educational process for college students majoring in the sciences is to engage in research activities, helping them to experience the challenges and triumphs they will experience in their careers. Because of the learning curve for most research progress, as well as small windows of time in order to complete the projects, undergraduate research experiences are often less-than-exciting.
Occasionally, however, a group of students stumbles upon a true discovery. Recently, a team of three 3rd year students studying at the Niels Bohr Institute undertook a week long observation at the Nordic Optical Telescope (NOT) in La Palma, Spain. Their mission: to take deeper, follow-up observations of a puzzling object that had been recently discovered. “Just like ‘ordinary’ researchers, they then had to make an application for observation time at the Nordic Optical Telescope,” explains Professor Johan Fynbo, who was their supervisor for the summer course.
“We had three hours to observe and already after one hour we had the first spectrum. It was a new experience for us, but we could see immediately that it was a quasar. A typical characteristic of a quasar is that the light has broad emission lines from gas close to the black hole. We were very excited and moved on to the other ‘candidates’ from observation and later that night we found yet another light reflection of the quasar,” explains Thejs Brinckmann, one of the astrophysics students working on the project.
Quasars are distant supermassive black holes that are swallowing gas that surrounds the massive remnants in what scientists call accretion disks – essentially a torus of hot gaseous matter swirling through space. Near the black hole, the gas will reach temperatures measured in millions of degrees, emitting intense radiation detectible from Earth. In some cases, the black hole is quite active and can release more energy in one second than our Sun will emit in more than 200 million years.
“The light from this quasar has been traveling for more than 11 billion years en route to Earth. Between the quasar and Earth is a collection of hundreds of galaxies – a galaxy cluster. This galaxy cluster has so much gravity that it pulls the light from the quasar. So instead of radiating in straight lines from the quasar, the light is deflected in an arc around the galaxy cluster. In this way, one can observe not just one, but several images of the same quasar. This is called the gravitational lens effect,” explains Fynbo.
Excited about the results, Norwegian astronomer Håkon Dahle, who first discovered the quasar field, later took additional data that revealed three additional quasar reflections from gravitational lensing effects. “This is the first time that a quasar has observed whose light has been reflected or ‘lensed’ in six separate image,” explains Fynbo.
“It is amazing to be allowed to participate in something that is relevant to research so early in our education,” says Brinckmann.
Results of their research are published in the Astrophysical Journal.