We know that the planets in our solar system were born from a dusty disk surrounding the sun billions of years ago; wouldn’t it be amazing if we could see another star system going through the birthing throes of this protoplanetary phase?
Today, a team of astronomers using the awesome power of the twin 10-meter Keck Telescopes atop Mauna Kea, Hawaii, have announced just that.
For the first time they have directly imaged a baby world forming close to its parent star inside an empty track of a larger disk of dust. This makes it a record-breaker — the proto(exo?)planet is five-times younger than the youngest exoplanet discovered to date.
The baby world — called LkCa 15 b — orbits LkCa 15, a T Tauri star located 450 light-years from Earth that is already known to possess a dusty circumstellar disk.
T Tauri stars are very luminous, young, variable stars. In astronomical timescales, they’ve recently formed from a cloud of gas under gravitational collapse. The gravitational energy released is what provides the energy to power the star, a phase before nuclear fusion is ignited in their cores.
So, when we observe LkCa 15, we know we are looking at a star that’s just starting out, potentially with a whole system of worlds that might form from its protoplanetary disk.
And now we know that there will be at least one world, LkCa 15 b, that Keck can see slowly forming.
“LkCa 15 b is the youngest planet ever found, about 5 times younger than the previous record holder,” said astronomer Adam Kraus of the University of Hawaii’s Institute for Astronomy. “This young gas giant is being built out of the dust and gas. In the past, you couldn’t measure this kind of phenomenon because it’s happening so close to the star. But, for the first time, we’ve been able to directly measure the planet itself as well as the dusty matter around it.”
Using a clever trick, Kraus and co-investigator Michael Ireland, of Macquarie University and the Australian Astronomical Observatory, were able to tease out the light being emitted by the dust surrounding the newborn star. They combined the power of Keck’s Adaptive Optics with a technique called aperture mask interferometry to manipulate the starlight after it is received by the telescope.
“It’s like we have an array of small mirrors,” said Kraus. “We can manipulate the light and cancel out distortions.” By doing this, the bright light emitted by the star can be canceled out, resolving the faint disks and gaps therein where baby worlds may be hiding. In one of those gaps, LkCa 15 b resides.
The study has been accepted for publication in The Astrophysical Journal.
“We realized we had uncovered a super Jupiter-sized gas planet, but that we could also measure the dust and gas surrounding it. We’d found a planet, perhaps even a future solar system at its very beginning,” he adds.
Kraus and Ireland intend to continue surveying other nearby stars to see if similar worlds are forming in the ultimate hope of understanding the planetary formation processes that built our own solar system.
Image: The circumstellar disk surrounding the star LkCa 15 (left). Zoomed in, with the light from the star canceled out, the location of the protoplanet can be seen — the red and blue “blob” (right). Credit: Kraus & Ireland 2011