More than 4,000 exoplanets are known to date, most of them orbiting single stars like our Sun. Now astrophysicist Dr Markus Mugrauer of Friedrich Schiller University Jena, Germany, has discovered and characterised many new multiple star systems that contain exoplanets. The findings confirm assumptions that the existence of several stars influences the process by which planets are formed and develop. The study by Mugrauer, of the Astrophysical Institute and University Observatory of the University of Jena, has now been published in the specialist journal Monthly Notices of the Royal Astronomical Society.

Space telescope provides precise data

“Multiple star systems are very common in our Milky Way,” explains Mugrauer. “If such systems include planets, they are of particular interest to Astrophysics, because the planetary systems in them can differ from our solar system in fundamental ways.” To find out more about these differences, Mugrauer searched more than 1,300 exoplanet host stars with exoplanets orbiting them to see whether they have companion stars. To this end, he accessed the precise observation data of the Gaia space telescope, which is operated by the European Space Agency (ESA).

In this way, he succeeded in demonstrating the existence of around 200 companion stars to planetary host stars that are up to 1,600 light years away from the Sun. With the help of the data, Mugrauer was also able to characterise the companion stars and their systems in more detail. He found that there are both tight systems with distances of only 20 astronomical units (au) — which in our solar system corresponds approximately to the distance between the Sun and Uranus — as well as systems with stars that are over 9,000 au from each other.

Red and white dwarfs

The companion stars also vary as to their mass, temperature and stage of evolution. The heaviest among them weigh 1.4 times more than our Sun, while the lightest have only 8 per cent of the Sun’s mass. Most of the companion stars are low-mass, cool dwarf stars that glow faintly red. However, eight white dwarfs were also identified among the faint stellar companions. A white dwarf is the burnt-out core of a sun-like star, which is only about as big as our Earth, but half as heavy as our Sun. These observations show that exoplanets can indeed survive the final evolutionary stage of a nearby sun-like star.

Double, triple and quadruple star systems with exoplanets

The majority of the star systems with exoplanets identified in the study have two stars. However, some two dozen hierarchical triple star systems and even a quadruple star system were detected. In the range of distances investigated, of between approximately 20 and 10,000 astronomical units, a total of 15 per cent of the stars studied have at least one companion star. This is only about half the frequency expected in general for solar-like stars. In addition, the companion stars detected show distances about five times greater than in ordinary systems.

“These two factors taken together could indicate that the influence of several stars in a star system disrupts the process of planet formation as well as the further development of their orbits,” says Mugrauer. The cause of this could be first the gravitational impact of a stellar companion on the gas and dust disc in which planets form around their host star. Later, the gravitation of the stellar companion influences the motion of the planets around their host star.

Markus Mugrauer would like to pursue the project further. In the future, too, the multiplicity of newly discovered planetary host stars would be studied using data from the Gaia mission and any companion stars detected would be precisely characterised. “In addition, we will combine the results with those of an international observational campaign, which we are currently conducting on the same topic at the Paranal Observatory of the European Southern Observatory in Chile,” added Mugrauer. “We will then be able to investigate the precise influence of stellar multiplicity on the formation and development of planets.”

In a study involving 1,369 children tracked from birth to 5 years of age, psychological scientists found that results of a standard blood test taken at birth could predict how teachers rated the children on emotion regulation, self-awareness, and interpersonal behavior 5 years later.

The results are published in Psychological Science, a journal of the Association for Psychological Science.

Researchers Erika M. Manczak of the University of Denver and Ian Gotlib of Stanford University were specifically interested in looking at the long-term implications of infants’ lipid profiles — a measurement of the amount of cholesterol and triglycerides in the blood. Triglycerides are fats that, at high levels, can increase the risk of stroke and heart disease.

Manczak and Gotlib used data from an ongoing study involving children born in the town of Bradford in the United Kingdom between March 2007 and December 2010. They looked at data involving 1,369 children from birth to 5 years of age. The babies were born to mothers of various ethnic backgrounds.

When the children reached age 3, the mothers were asked to rate their child’s health. And when the children were 4 to 5 years old, their teachers rated each of them on their psychological development, including self-confidence, emotional control, and interpersonal relationships. The teachers were asked to classify each child as below, at, or exceeding developmental expectations.

Manczak and Gotlib found that newborns’s whose cord blood showed high levels of high-density lipoprotein (HDL) — known as the “good cholesterol” because it removes fat from artery walls — were significantly more likely to later receive higher ratings on psychological development by their teachers. In contrast, newborns whose cord blood tested high for triglycerides and very-low-density lipoprotein — known as the bad cholesterol — were more likely to receive low teacher ratings on social and emotional development. The results were consistent across ethnic groups and gender.

Manczak and Gotlib acknowledge that their findings are correlational and don’t conclusively show that lipids in cord blood lead to psychological problems over time. But the results do introduce the possibility that lipids may be a new mechanism to consider when trying to understand the causes of mental health problems, they say.

“If this is replicated in other studies, it would suggest that lipid profiles at birth could play a role in identifying children who might be at heightened risk for psychological problems later, allowing health care providers to intervene early,” Manczak says. “It also introduces the possibility that lipids may be a new mechanism to consider when trying to understand what causes mental health problems.”

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Traditionally, zoos have focussed on more straightforward measures such as whether animals are eating, sleeping and breeding.

The new review, by the University of Exeter and the University of Winchester, says zoos have made vast improvements in recent years, but closer observation of animal behaviour — a method called Qualitative Behavioural Assessment, developed in livestock farming — could reveal even more about their psychological state.

An animal’s posture, facial movements and activity levels are among the things that might reveal whether it is excited, calm, interested, nervous, relaxed, etc.

“Zookeepers are dedicated and knowledgeable about their animals, and they will often recognise the psychological state of an animal by its behaviour and body language,” said Dr Paul Rose, of the University of Exeter.

“What we are suggesting is a more consistent version of this, carried out over time.

“Certain behaviours will indicate certain moods in a particular species, and we should build our knowledge of this for different species that live in zoos.

“For example, lions have a wide range of facial expressions, and research on these expressions could help zoos understand the animals’ state of mind.

“This information could then be used to improve welfare by adjusting enclosures, diets, feeding times or any number of other aspects of the way animals are kept.”

Dr Rose conducts much of his research at WWT Slimbridge Wetland Centre, and is currently examining how the swans there might reveal their psychological state via their behavioural expression.

“We’re looking at how much time they spend investigating and exploring their habitat, which could show that they’re feeling emotions like being bold or confident or interested,” he said.

“When they’re apprehensive or unsure, they appear to move less and be more vigilant, and keep their feathers compressed close to their bodies.”

The study evaluates existing research on Qualitative Behavioural Assessment, much of it from farming, and suggests research opportunities and practices that could be adopted by zoos.

“Animal welfare in zoos has improved dramatically in the last 10 or 20 years, and this method gives zoos another way to recognise and promote positive welfare,” Dr Rose said.

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