November 29, 2012
Jets Seen From Distant Quasar Hint At Conditions In The Early Universe
April Flowers for redOrbit.com - Your Universe Online
NASA's Chandra X-ray Observatory has detected a jet of X-rays from a supermassive black hole 12.4 billion light years from Earth, making it the most distant X-ray jet ever observed. The jet gives astronomers a glimpse into the explosive activity associated with super massive black hole growth in the early universe.
"We're excited about this result, not just because it's a record holder, but because very few X-ray jets are known in the early universe," said Teddy Cheung of the National Academy of Sciences (National Academy of Sciences), resident at the Naval Research Laboratory in Washington DC.
Moving through a sea of background photons left behind after the Big Bang, the electrons in the jet fly away from the quasar. When a cosmic microwave background photon collides with a fast-moving electron, the photon's energy can be boosted into the X-ray band.
"Since the brightness of the jet in X-rays depends, among other things, on how fast the electrons are moving away from the black hole, discoveries like the jet in GB 1428 tell us something about the environment around supermassive black holes and their host galaxies not that long after the Big Bang," said Lukasz Stawarz from the Japan Aerospace Exploration Agency (JAXA).
The universe is at an age of about 1.3 billion years old when this quasar is seen, less than 10% of its current age, making the cosmic background radiation a thousand times more intense than it is now. The jet is therefore much brighter and compensates in part for the dimming due to distance.
"We're lucky that the universe gives us this natural amplifier and lets us detect this object with relatively short exposures," said Aneta Siemiginowska, of the Harvard-Smithsonian Center for Astrophysics. "Otherwise we might miss important physical processes happening at very large distances from Earth and as far away as GB 1428."
The authors acknowledge that there is another possible source of X-rays for the jet — radiation from electrons spiraling around magnetic field lines in the jet — they favor the idea that the cosmic background radiation is being boosted because the jet is so bright.
The most distant X-ray jet known previous to GB 1428's discovery was 12.2 billion light years away. A third is located at about 12 billion light years. The same team that conducted this current study discovered both of the closer jets. A radio wave jet similar in shape was also detected in GB 1428 with the NSF's Very Large Array (VLA).
These three extremely distant X-ray jets are produced by particle beams that appear to be moving slightly more slowly than jets from galaxies that are not as far away. One cause may be that the jets were less energetic when launched from the black hole, or perhaps they are slowed down more by their environment.
The team believes that the length of the jet in GB 1428 is at least 230,000 light years. This is about twice the diameter of the entire Milky Way galaxy. In the Chandra and VLA data, the jet is seen on only one side of the quasar. Combining this data with previously obtained evidence, the team believes this means the jet is pointed almost straight at us; a configuration that would boost the radio and X-ray signals for the observed jet. This configuration would diminish the radio and X-ray signals for a jet presumably pointed in the opposite direction.
A set of radio telescopes at different locations around the Earth also took observations of GB 1428, allowing details to be resolved on exceptionally small scales. This revealed the presence of a much smaller jet that points in a similar direction to the larger jet. This smaller jet is about 1,900 light years long.
The findings of this study were published in The Astrophysical Journal Letters.