For the first time in the history of astronomy, experts have caught sight of a not-so-distant star consuming at least one planetary body.
Using X-Ray observations conducted at NASA's Chandra X-Ray Observatory, an international team of scientists led by astrophysicists at the Massachusetts Institute of Technology has made the first observations of a star swallowing two infant planets that collided into each other before falling into the young star's rotating disk.
Young Star Dimming Periodically
Four hundred fifty light-years from Earth is a curious star that has been perplexing astronomers for 80 years. The young star, named RW Aur A, sits in the constellation Taurus-Auriga, a peculiar group of stars peppered with a variability of newborn stars.
RW Aur A is part of a binary system, which means it circles another star, RW Aur B. Both stars are approximately as heavy as the Sun.
Since it was first discovered in 1937, RW Aur A has been regularly dimming in brightness for a month before brightening again. In recent years, the star has been observed dimming more frequently and for longer stretches of time.
In 2011, for instance, the star lost some of its brightness for half a year. This was followed by another instance of dimming that took place in mid-2014 until November 2016. In January last year, the star dimmed again, allowing the team at Chandra to collect X-ray evidence that can help explain the periodic dimming episodes.
Two Planets Crashed And Fell
In a new study published in the Astronomical Journal, the team of astrophysicists says the dimming of RW Aur A may be caused by two planets smashing into each other and then falling into the star. The team also includes experts from the Harvard-Smithsonian Center for Astrophysics and other researchers from Belgium and Germany.
The collision likely created a thick cloud of dust and gas that temporarily blocked the star's light. As the wreckage from the cosmic crash fell into the star's disk, it produced the blanket of dust and gas that has been causing the dimming.
Lead author Hans Moritz Guenther, research scientist at the Kavli Institute for Astrophysics and Space Research at MIT, says computer models have long predicted that young stars can devour planetary formations, although direct observations have not been made before.
"If our interpretation of the data is correct, this would be the first time that we directly observe a young star devouring a planet or planets," Guenther says.
The researchers say this could also explain the previous episodes of dimming too. If two planets or the remains of past collisions crashed into each other, it would create debris that could possibly go off on rogue orbits.
This would make it even more possible for a planet or the remnants of a crash to fall into the star's planetary disk.
How Dimming Happens
After analyzing 14 hours of X-ray data gathered from Chandra, the researchers found that the star contains far more iron than typical of its kind. This prompted the researchers to ask: where does all the iron come from?
There are two possible explanations. First, there could be a dust pressure trap, which is like a dead zone where small particles are gathered in the disk around the star. If RW Aur B moves close to RW Aur A, the gravitational forces from both stars could unleash the trapped particles, causing excess iron to fall into the star.
The second explanation, which is more plausible to the researchers, is that two planets collided, creating a thick cloud of particles. If one or two of these planets had a lot of iron, the collision would create an iron-rich cloud that is then consumed by the young star's disk. This is also the same cloud that dims the light of the star.
The researchers, however, have yet to confirm this hypothesis. If future observations show that the iron content in the star remains high after a year, it is very likely that the iron was generated by a collision of planets that were then swallowed by the star.
