A newly-detected planetary system is making astronomers question how giant planets are formed, particularly around young stars, reports Science Daily.
The star in question is CI Tau, a very young celestial body located about 500 light-years from Earth in a highly prolific star-birth region of the Milky Way known as Taurus Auriga. At just 2-million-years-old — a mere “toddler” in cosmic terms — CI Tau already hosts its own planetary system made up of giants that rival in size the largest planets in our own solar system, Jupiter and Saturn.
In 2016, CI Tau made headlines after astronomers discovered that the star was orbited by a gas giant 11.3 times more massive than Jupiter, Sci-News reported at the time. Subsequently dubbed CI Tau b, the gargantuan exoplanet goes around its parent star once every nine days and is known as a “hot Jupiter” — the very first one to ever be detected around such a young star.
As the Inquisitr previously reported, hot Jupiters are giant exoplanets with masses in the range of Jupiter that orbit extremely close to their parent star. Since these exoplanets are tidally locked — meaning that one side always faces the star — their day-side is constantly pummeled with radiation and reaches scorching surface temperatures of up to 3,600 degrees Fahrenheit (2,000 Celsius).
But it seems that CI Tau b is not the only planet to orbit this young star. According to a study recently published in The Astrophysical Journal Letters, the neighborhood around CI Tau is much more crowded than originally believed.
And Then There Were Four
A separate team of astronomers took a peek at CI Tau with the Atacama Large Millimeter/submillimeter Array (ALMA) in Chile. The scientists were stumped to discover that the young star is orbited, not by one, but by four massive planets.
Just like most young stars, CI Tau is still surrounded by a giant cloud of dust, ice, and gas called a protoplanetary disk and from which new planets are churned out. The ALMA observations revealed that the star’s protoplanetary disk hides three additional gas giants — one the size of Jupiter and the other two, the size of Saturn.
This is “the first time that so many massive planets have been detected in such a young system,” notes the University of Cambridge in the U.K., which led the investigation into CI Tau’s system.
A Very Unusual Planetary System
As if this wasn’t remarkable in itself, the team also uncovered that these gas giants circle the young star at strikingly different ranges, exhibiting “the most extreme range of orbits” ever detected in a planetary system.
The closest planet to CI Tau is the hot Jupiter CI Tau b. While this innermost exoplanet circles the star within the same distance as Mercury orbits the sun, the outermost planet of the system — a Saturn-sized gas giant — sits three times farther away from CI Tau than Neptune is to the sun.
This means that the exoplanet “is more than a thousand times further from the star” than the hot Jupiter discovered two years ahead of its siblings, explains the University of Cambridge.
This unusual planetary system presents astronomers with a new puzzle, namely to figure out how these enormous planets managed to take shape in such a short time given the young age of their parent star.
The Enigma Around CI Tau
While about 1 percent of stars are known to host a hot Jupiter, most of them are hundreds of times older than CI Tau.
“It is currently impossible to say whether the extreme planetary architecture seen in CI Tau is common in hot Jupiter systems because the way that these sibling planets were detected — through their effect on the protoplanetary disk — would not work in older systems which no longer have a protoplanetary disk,” said study lead author Cathie Clarke, a professor at Cambridge’s Institute of Astronomy.
But the biggest question concerns the system’s outermost planets — both Saturn-sized — and how they were able to form at all.
“Saturn mass planets are supposed to form by first accumulating a solid core and then pulling in a layer of gas on top, but these processes are supposed to be very slow at large distances from the star.”
Going forward, astronomers plan to study CI Tau and its mystifying planets with other telescopes and observe the system at multiple wavelengths in order to learn more about the star’s protoplanetary disk and its properties.