Astronomers at the European Southern Observatory have found a companion to a star that is clearing out part of a dust cloud, the first time anyone has seen a planet in the process of formation.
The star is T Chamaleontis, or T Cha, about 350 light years from Earth. It can't be seen with the naked eye but is visible in a small telescope in the sky, south of the Southern Cross. The star itself is only a few million years old, and is otherwise much like the Sun was in its early stages, though about 50 percent heavier. Such stars are called T Tauri, and are surrounded by clouds of gas and dust. That gas and dust eventually coalesces into planets, but nobody has yet observed this actually happening before.
The astronomers studying T Cha may have found a smoking gun of planet formation. In T Cha's dust cloud they discovered a gap. Some of the disc material formed a narrow ring only about 20 million kilometers from T Cha, closer than Mercury is to our own sun. Beyond this inner disc, they found a region devoid of dust stretching out to regions about 1.1 billion kilometers from the star.
Looking more closely, they found an object located within the gap in the dust disc, about one billion kilometers from T Cha- slightly further out than Jupiter is within our Solar System and close to the outer edge of the gap. While small bodies have been detected in dusty discs around other stars, this is the first time anyone has confirmed the existence of such a body around a star this young.
In our own solar system, scientists theorize that big planets such as Jupiter did something similar. By looking at this kind of system in action the scientists can understand better how our own solar system formed.
Further observations will show whether the companion is a large, Jupiter-like planet or a brown dwarf, a massive object that is bigger than a planet but too small to ignite the nuclear fusion that makes stars shine. If confirmed it would the first time anyone has observed planets in the early stages of formation.
The planet-like body is no more than 80 times as massive as Jupiter, though that could change as more observations are done, said Johan Olofsson, of the max Planck Institute for Astronomy in Germany.
To see this object, Olofsson and another scientist, Nuria Huélamo of Spain's Center for Astrobiology, used an instrument called the Astronomical Multi-beam Combiner (AMBER) and the Very Large Telescope Interferometer (VLTI). The observations were done in infrared wavelengths, which show the heat given off by dust and gases that wouldn't ordinarily be visible. By combining the light from several telescopes, they were able to create a kind of virtual telescope much larger than any individual instrument.
The telescope was combined with another instrument attached to the European Southern Observatory's Very Large Telescope, called NACO. It can adapt its optics to counteract the interference from the atmosphere that blurs small, faint objects. At certain wavelengths it is better for picking up small faint objects, such as planets, near big bright objects like stars.
A cloud of material around a star will give off a certain amount of radiation because it gets heated by its parent star; if some of that radiation is missing then there is a gap in the material. Further, NACO found another body radiating at the right wavelengths for either a big planet or dusty brown dwarf.
Oloffson said future work will try to get a better picture of the structure of the outer ring and narrow down the characteristics of the planetary body.
This video takes us on a fly-through of the disc around the young star T Chameleontis. Using ESO’s Very Large Telescope this disc has been found to be in two parts, a narrow ring close to the star and the remainder of the disc material much further out. A companion object has been detected in the gap in the disc that may be either a large planet or a dusty brown dwarf.
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