“We’re seeing planet building happening right before our eyes,” said astronomer David Wilner of the Harvard-Smithsonian Center for Astrophysics (CfA), who along with other astronomers observed first stages of planet-building around nearby star called TW Hydrae, already in 2005.
“The foundation has been laid and now the building materials are coming together to make a new solar system.”
Located about 180 light-years away in the constellation Hydra the Water Snake, TW Hydrae consists of a 10 million-year-old star about four-fifths as massive as the Sun. The protoplanetary disk surrounding TW Hydrae contains about one-tenth as much material as the Sun — more than enough to form many Jupiter-sized worlds.
“TW Hydrae is unique,” said Wilner. “It’s nearby, and it’s just the right age to be forming planets. We’ll be studying it for decades to come.”
Now, another group of astronomers carefully observe this amazing, massive TW Hydrae, using the European Space Agency’s Herschel Space Telescope, a mission in which NASA is a participant,
In addition to revealing the peculiar state of the star, the findings also demonstrate a new, more precise method for weighing planet-forming disks. Previous techniques for assessing the mass were indirect and uncertain. The new method can directly probe the gas that typically goes into making planets.
Planets are born out of material swirling around young stars, and the mass of this material is a key factor controlling their formation. Astronomers did not know before the new study whether the disk around TW Hydrae contained enough material to form new planets similar to our own.
Click on image to enlargeMisty Star in the Sea Serpent
“Before, we had to use a proxy to guess the gas quantity in the planet-forming disks,” said Paul Goldsmith, the NASA project scientist for Herschel at NASA’s Jet Propulsion Laboratory in Pasadena, Calif. “This is another example of Herschel’s versatility and sensitivity yielding important new results about star and planet formation.”
Using Herschel, scientists were able to take a fresh look at the disk with the space telescope to analyze light coming from TW Hydrae and pick out the spectral signature of a gas called hydrogen deuteride, which is a heavier version of hydrogen, emitting light at longer, far-infrared wavelengths that Herschel is equipped to see.
Astronomers measured the levels of hydrogen deuteride and obtain the weight of the disk with the highest precision yet.
“Knowing the mass of a planet-forming disk is crucial to understanding how and when planets take shape around other stars,” said Glenn Wahlgren, Herschel program scientist at NASA Headquarters in Washington.
Whether TW Hydrae’s large disk will lead to an exotic planetary system with larger and more numerous planets than ours remains to be seen, but the new information helps define the range of possible planet scenarios.
“The new results are another important step in understanding the diversity of planetary systems in our universe,” said Bergin. “We are now observing systems with massive Jupiters, super-Earths, and many Neptune-like worlds. By weighing systems at their birth, we gain insight into how our own solar system formed with just one of many possible planetary configurations.”