Credit: Karen L. Teramura, University of Hawaii Institute for Astronomy
Credit: Kraus and Ireland, 2011
SYDNEY: The first direct image of a young exoplanet forming around its parent star has been captured, researchers say, offering new insight into planet and solar system formation.
The hot protoplanet, named LkCa 15 b, is a gas giant forming inside a wide gap between its star and an outer disk of dust – about the distance from the Sun to Uranus.
“It’s exciting because we’ve never seen a planet this young before,” said co-author Michael Ireland, a lecturer in astrophotonics at Macquarie University in Sydney, whose findings were presented last week at NASA’s Goddard Space Flight Centre in the U.S. “This gives us the first hint that planets can form a long way out before they migrate inward.”
The images were captured using the 10-m Keck Telescopes in Hawaii, which are equipped with deformable mirrors to rapidly correct for atmospheric distortions to starlight.
Astronomers combined this technology with a precision optical technique called aperture mask interferometry. This involves placing a small mask with several holes in the path of the light, which is collected and amplified by the telescope.
“We can then manipulate the light and cancel out distortions,” explained co-author Adam Kraus, from the University of Hawaii’s Institute of Astronomy of the paper has been accepted for publication in The Astrophysical Journal.
“It’s enabled us to see inside disks of dust and gas around young stars closer than ever before. The gaps in those disks are the perfect zone for young planets in the process of formation.”
Extensive models prove planet
The researchers began searching for young planets through a survey of 150
young stars in star forming regions, but narrowed their search to a dozen stars known to have similar gaps in their outer disks.
Once they discovered LkCa 15 b, they knew they were onto something. “We knew it was more complex than a single companion object, so we collected data several times and at differing wavelengths over 12 months to get a clearer picture,” said Ireland.
“What emerged is that we had indeed captured a young gas giant in the process of formation. Theorists have made guesses about what this might look like, but to finally see it is a real milestone.”
The protoplanet, which appears as a blue dot in the reconstructed image, is estimated to be around 1,000 degrees Celsius.
The astronomers also observed material around the hot structure that was slightly cooler, around 500 degrees Celsius – which appears as a red glow in the image – which is either accreting onto the planet, or being ejected from it.
“It’s certainly dust and gas, but the question is, what’s the mechanism that makes it glow?” asks Ireland. He believes the best explanation, at present, is that these are shocks from the outer disk around the star, interacting with the material and heating it up.
The next step for Ireland and his colleagues is to look for the orbit of the planet to understand how it moves. Additional studies will be needed to confirm the planetary status of the structure.