The spacecraft Gaia has identified two giant new planets in the Milky Way

Tel Aviv University team who led the research say Gaia’s innovative technology is sparking a true revolution in the world of astronomy.

 Artist's impression of a gas giant planet forming in the disc around the young star HD 100546. (photo credit: ESO/L. Calçada/Flickr)
Artist's impression of a gas giant planet forming in the disc around the young star HD 100546.
(photo credit: ESO/L. Calçada/Flickr)

The European Space Agency’s (ESA) Gaia space observatory has for the first time identified two new, giant planets – named Gaia-1b and Gaia-2b – in remote solar systems.

The research was led by Prof. Shay Zucker, head of Tel Aviv University’s Porter School of the Environment and Earth Sciences and doctoral student Aviad Panahi from TAU’s Sackler School of Physics and Astronomy.

The study, conducted in cooperation with ESA and the Gaia space telescope’s research groups, was published in the scientific journal Astronomy & Astrophysics under the title “The detection of transiting exoplanets by Gaia.”

“The discovery of the two new planets was made in the wake of precise searches, using methods of artificial intelligence"

Prof. Shay Zucker

What is Gaia's mission?

Gaia – the Global Astrometric Interferometer for Astrophysics – is an ESA astronomical observatory mission whose goal is to create the largest, most precise three-dimensional map of the Milky Way by surveying about 1% of the galaxy’s 100 billion stars.

Gaia, which was launched on December 19, 2013 from French Guiana by a Russian Soyuz rocket, will detect and very accurately measure the motion of each star in its orbit around the center of the galaxy.

 The transit method.  (credit: Illustration: Aviad Panhi) The transit method. (credit: Illustration: Aviad Panhi)

Each of the one billion stars that Gaia studies will be observed an average of 70 times over five years to create a record of the brightness and the position of each star over time.

Until now, one of the mission’s most surprising discoveries was its ability to detect starquakes – tiny motions on the surface of a star – that change the shapes of stars, something the observatory was not originally built for.

Planets beyond our solar system

There are eight planets that orbit the sun in our solar system; less known are the hundreds of thousands of other planets in our galaxy, the Milky Way, which contains untold numbers of solar systems.

Planets in remote solar systems were first discovered in 1995 and have been an ongoing subject of astronomers’ research ever since, in the hope of using them to learn more about our own solar system.

“The planets were discovered thanks to the fact that they partially hide their suns every time they complete an orbit, and thus cause a cyclical drop in the intensity of the light reaching us from that distant sun,” explained Panahi. “To confirm that they are in fact planets, we performed tracking measurements with the American telescope called the Large Binocular Telescope, which is located in Arizona. This telescope is equipped with two giant mirrors, each with a diameter of 8.4 meters, making it one of the largest telescopes in the world today. This telescope makes it possible to track small fluctuations in a star’s movement, which are caused by the presence of an orbiting planet.”

 Aviad Panhi (credit: TEL AVIV UNIVERSITY) Aviad Panhi (credit: TEL AVIV UNIVERSITY)

To fulfill its mission, Gaia scans the heavens while rotating around an axis, tracking the locations of about two billion suns in our galaxy with a precision of up to a millionth of a degree. This level of precision is comparable to standing on Earth and identifying a ten shekel coin on the moon.

Discovery of the giant planets

While tracking the suns’ locations, Gaia also measures their brightness, which is an incomparably important feature in observational astronomy because it can provide much information about the physical characteristics of heavenly bodies. Changes documented in the brightness of the two remote suns were what led to the discovery of the planets.

Zucker has extensive experience in discovering planets, ever since his days as a student of the senior astronomer Prof. Tsevi Mazeh.

“The measurements we made with the telescope in the US confirmed that these were in fact two giant planets, similar in size to the planet Jupiter in our solar system, and located so close to their suns that they complete an orbit in less than four days, meaning that each Earth year is comparable to 90 years of that planet,” recalled Zucker.

“The discovery of the two new planets was made in the wake of precise searches, using methods of artificial intelligence. We have also published 40 more candidates that we detected with Gaia,” he explained. “The astronomical community will now have to try to corroborate their planetary nature, as we did for the first two candidates. The data continues to accumulate, and it is very likely that Gaia will discover many more planets with this method in the future.”

  Prof. Shay Zucker. (credit: TEL AVIV UNIVERSITY) Prof. Shay Zucker. (credit: TEL AVIV UNIVERSITY)

This discovery marks another milestone in the scientific contribution of the Gaia spaceship’s mission, which has already been credited with a true revolution in the world of astronomy.

The mission’s ability to discover planets using the partial occultation method, which generally requires continuous monitoring over a long period of time, has been doubted up to now.

The research team charged with this mission developed an algorithm specially adapted to Gaia’s characteristics and searched for years for these signals in the cumulative databases from the spaceship.

Commenting on the possibility of life on the surface of those remote new planets, Panahi concluded: “The new planets are very close to their suns so the temperature on them is extremely high – about 1,000 degrees Celsius – so there is no chance of life developing there. In the astronomy community, such a planet is called ‘Hot Jupiter’ because of its size and its proximity to its sun. Even though there is no real chance of life on the planets we found, I’m sure that there are countless others that do have life on them, and it’s reasonable to assume that in the next few years, we will discover signs of organic molecules in the atmospheres of remote planets. Most likely we will not get to visit those distant worlds any time soon, but we’re just starting the journey, and it’s very exciting to be part of the search.”