Planets remarkably similar to Jupiter and Neptune found orbiting Sun-like star: ScienceAlert

When it comes to finding life on other planets, a hot, wet world bubbling with a complex soup of chemicals might not be enough. It could also pay to have the right kinds of planets in the neighborhood.

An intriguing pair of gas giants has been found orbiting a star so similar to the Sun that it could almost be its twin, and it could teach us a thing or two about solar systems like ours.

The star HIP 104045, located just 175 light-years away, appears to have at least two large worlds whizzing around it — one about half the mass of Jupiter in a 6.3-year orbit, and the other about 2.5 times Neptune’s mass in 316-day orbit.

This discovery, submitted to Monthly Notices of the Royal Astronomical Society and available on the preprint server arXiv, helps us understand the many different systems that may orbit sun-like stars, in the hope of finally finding another Earth.

As the only place in the universe known to develop a biosphere, Earth is our only blueprint for the conditions necessary for life. But Earth does not exist in isolation; it has an entire planetary system around it with seven other planets, countless asteroids and dwarf planets, and our star, the Sun.

Recent studies suggest that the architecture of a planetary system plays an important role in the habitability of a planet in Earth conditions. The presence of asteroids and comets that can supply certain ingredients to a planet is quite important.

Jupiter also seems to play a significant role: it protects the inner solar system from constant bombardment from small rocks that shepherd both the asteroid belt and the asteroids that share its orbit. But its enormous gravity can also disrupt the orbits of the smaller bodies and hurl them toward the inner solar system. Early in the system’s history, Jupiter was likely instrumental in helping these rocks reach Earth.

If we want to narrow down our options for where to look for life, we could do worse than looking for Jupiter-like planets for other reasons as well.

“Jupiter analogs preferentially form around stars with near-solar metallicities, and strikingly, potentially habitable low-mass planets can be common around stars that host a cold Jupiter,” writes an international team of astronomers led by Thiago Ferreira of the University of Sao Paulo in Brazil.

“Small Earth-sized planets are more common than giant planets. These factors set the precedent for the search for Earth-like planets around Sun-like stars by primarily looking for Jupiter-like planets.”

Since 2014, astronomers have been using the High Accuracy Radial Velocity Planet Searcher (HARPS) at the European Southern Observatory’s La Silla 3.6-meter telescope in Chile’s Atacama Desert to search for planets around stars similar to the Sun.

On paper, HIP 104045 is an almost perfect match. Its metal content is very similar to that of the Sun. It is about 4.5 billion years old; The Sun is 4.57 billion years old. HIP 104045 is only 1.03 times the mass of the Sun, 1.05 times the radius of the Sun and has 1.11 times the luminosity of the Sun.

When Ferreira and his colleagues analyzed the light from HIP 104045, they found evidence for not one world, but two.

The first world, at 0.498 times the mass of Jupiter, is what is known as a Jupiter analog: an exoplanet between 0.3 and 3 times the mass of Jupiter, with an orbit between 3 and 7 AU from the star, making it likely to play a dynamic role similar to that of Jupiter in our own solar system.

The second exoplanet is a super-Neptune. Where our own Neptune is 17 Earth masses, this discovery weighs in about 43 times the mass of Earth. Since the upper limit for rocky worlds is thought to be around 10 Earth masses, the planet is unlikely to be a terrestrial world like ours, but instead rather gaseous in nature.

But at least it’s in what’s known as the optimistic habitable zone. The habitable zone is the distance range from the host star that is within a temperature range for liquid water; the optimistic habitable zone is a wider range of distances where habitable temperatures are possible, but you might be pushing your luck a bit.

Just don’t get your hopes up. The planet does not pass between us and its star, so we currently have no way to analyze its atmosphere for biosignatures.

Could there still be a small, rocky world orbiting HIP 104045 filled with alien goo? While we might hope that the discovery of a Jupiter analog suggests that an Earth-like world is hiding nearby, super-Neptune orbiting relatively close to the star pours cold water on that idea.

The presence of super-Neptune, the team says, is just one more reason to believe that our own solar system is indeed atypical, with systems similar to ours occurring in perhaps 1 percent of sun-like stars.

Of course, we don’t even have close to enough information yet. There are many stars out there. So we just keep looking.

The team’s research has been submitted to Monthly Notices of the Royal Astronomical Societyand is available on arXiv.

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