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Science Square (Issue 101)
Sep 1, 2014

Planet with the longest orbit discovered

Astronomers have discovered a planet with the longest known orbital period. Exoplanet Kepler-421b has been identified through the Kepler observatory, a space-based telescope. It circles its star once every 704 days. More than 1800 exoplanets have been discovered so far, but compared to Kepler-421b, those had much shorter orbital periods, like a few weeks or even a few days. The host star for Kepler-421b is much like the sun, but it is little bit smaller and relatively cooler. With an orbital distance of 177 million kilometers, Kepler-421b gets about one-fourth the light from the host star as the Earth receives from the sun, which makes the exoplanet as cold as -100 °C. The unusual orbit places Kepler-421b beyond the "snow line," which is accepted as the dividing line between rocky and gaseous planets. Outside of the snow line, water condenses into ice grains that stick together to build planets known as "gas giants." Since gas giant planets are very close to their stars, theorists believe that many exoplanets migrate inward early in their history. However, Kepler-421b is the first example of why such migration may not be necessary.

Sunflowers' internal clock

Plants are known to grow toward the sun to maximize the amount of energy they absorb. Sunflowers (Helianthus annuus) show the most fascinating behavior during summer, when they follow the sun as it rises in the east every morning and sets in the west every evening. In a recent study, scientists challenged the obvious explanation for this plant's behavior: are flowers solely responding to sunlight or are there other unknown mechanisms at work? They designed a clever yet simple experiment where they grew sunflowers in chambers with a fixed overhead light that was continuously on. Surprisingly, for several days, the sunflowers under constant light kept moving as if the sun were rising in the east and setting in the west. This unexpected result suggests that sunflowers were not responding only to the direction of the light but also to an internal biological clock. Furthermore, they discovered that sunflowers bend when one side of the stem grows faster than the other. For example, the west side of the stem seems to grow faster to bend the plant towards the east in the morning. Scientists now hope to understand how an internal biological clock in sunflowers has the opposite effects on opposite sides of the stem. Sunflowers are not the only plants performing this diurnal dance; other agriculturally important crops such as soybeans and cotton exhibit the very same behavior. Solar tracking is known to boost plant yield and discovering the mechanisms of how plants track the sunlight might have important implications for improving global agricultural yields.

Friends linked by genes

It is a common observation that close friends look alike. Even centuries ago, Plato noted the tendency that good friends usually have similar appearances. Recently, a group of geneticists took this idea even further and suggest that people on average tend to choose friends who are genetically similar. The study provided convincing evidence that we have more DNA sequences in common with the people we pick as friends than we do with strangers in the same population. Researchers performed a genome-wide analysis of approximately 1.5 million markers of gene variations from 1,932 subjects of the Framingham Heart Study, which is one of the most comprehensive genetic databases. They identified 1300 pairs of non-relative friends and compared their genetic information to each other. The analyses showed that friends share similar genetic variations (around 1% genomewide), to the degree that it is as if they have the same great-great-great-grandparent – in other words, as if they were fourth cousins. Notably, friend pairs seem to have the greatest similarity in the genes that are responsible for a sense of smell and they show the most difference in immunity-related genes. Friendship entails spending a lot of time together and looking out for each other. Odors are strong behavioral cues in human psychology and people with similar olfactory preferences might like to prefer living or hanging out in similar environments. Likewise, it is potentially a big advantage that friends don't get infected from the same microbes at the same times, so that one of them can take care of the other. As much as these anthropological implications are merely speculations with many caveats – and despite there being many obvious social, ethnical, and cultural factors that help determine friendships – the genetic basis of friendship and other social interactions may hold answers to at least some of the mysteries of human behavior.