Massive Planet Found 'Dancing' With Dwarf Star, Sun-like Star

A planet that is about eight times Jupiter's mass, with a really eccentric, or non-circular, orbit, has been found "dancing" with a Sun-like star and a dwarf star.

Could it be the do-si-do?

It is near the already-known star HD 7449, and researchers learned about the presence of the dwarf star from looking at the eccentric path of the very large planet (which was discovered in 2011 in HD 7449's orbit). Clearly, something was influencing the big planet's movements, they thought, according to a release.

The team of researchers from Carnegie Institution for Science used the Magellan adaptive optics (MagAO) instrument suite, which lets astronomers take very high-resolution pictures and gives them a sharp view of the night sky.

Right away, they saw the small star, which is essentially miniscule and has a mass that is 20 percent of the Sun's. It is located near HD 7449A, the primary star. It is about 18 astronomical units (AU) from that star, which can be compared with Neptune's distance of 30 AU from the Sun, according to a statement.

In the recent past, astronomers believed that two co-orbiting stars (binaries) were unable to host planets, but the number of circumbinary planets found in the night sky has been growing. Still, there are very few systems that consist of a star that is like a Sun, a dwarf star and a gas giant planet between them, all set close together.

The planet 7449Ab is also significantly larger than those in other cases, and has the most eccentric orbit. In their report in The Astrophysical Journal, the authors said they think the dwarf star and the planet have been influencing each other with gravity for millions of years.

"It's difficult to visualize what happens to the planet over time, but you could say that it's ‘dancing' between the two stars," lead author Timothy Rodigas said in the statement.

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