This exoplanet is too hot to be habitable

Anger, emotional distress may up stroke risk: Study Known as GJ 367b, the newly found exoplanet which is apparently smaller than Earth, was possibly a giant planet with a vast, gaseous envelope, like Neptune, researchers say

Aglobal study co-led by NUI Galway into causes of stroke has found that one in 11 survivors experienced a period of anger or upset in the one hour leading up to it.

The suspected triggers have been identified as part of the global INTERSTROKE study – the largest research project of its kind, which analysed 13,462 cases of acute stroke, involving patients with a range of ethnic backgrounds in 32 countries, including Ireland.

Stroke is a leading global cause of death or disability.

Professor Andrew Smyth, Professor of Clinical Epidemiology at NUI Galway, Director of the HRB-Clinical Research Facility Galway and a Consultant Nephrologist at Galway University Hospitals, was one of the lead researchers.

He said: “Stroke prevention is a priority for physicians, and despite advances, it remains difficult to predict when a stroke will occur. Many studies have focused on medium to longterm exposures, such as hypertension, obesity or smoking. Our study aimed to look at acute exposures that may act as triggers.”

AKeele (UK)

s our solar system formed 4.6 billion years ago, small grains of dust and ice swirled around, left over from the formation of the Sun. Through time, they collided and stuck to each other. As they grew in size, gravity helped them clump together. One such rock grew into the Earth on which we live.

We now believe that most of the stars in the night sky are also orbited by their own planets. Astronomers have already found more than a thousand gas-giant planets – large, gaseous bodies similar in size to Jupiter. The focus now is on looking for rocky, Earth-sized planets. We expect that these will be similarly abundant but, being much smaller, they’re harder to find.

A new paper published in the journal Science documents the latest discovery of a small planet, assigned the catalogue number GJ 367b. This exoplanet was found by a team, of which Coel Hellier, Professor of Astrophysics, Keele University, was also a member, led by Dr Kristine Lam of the Institute of Planetary Research at the German

Aerospace Center.

Members of the team noticed the first signs of GJ 367b in data from Nasa's Transiting Exoplanet Survey Satellite, or Tess. Among the millions of stars being monitored by this satellite, one showed a tiny but recurrent dip in its brightness.

This is the tell-tale sign of a planet passing in front of its star every orbit (called a “transit”), blocking some of the star's light. The dip was only 0.03% deep, so shallow that it's near the limit of what can be detected. That means the planet must be small, comparable to Earth.

Lam also wanted to learn about the planet's mass. To do that, her team set about observing the host star at every opportunity with what's called the High Accuracy Radial Velocity Planet Searcher, or Harps. This is an instrument attached to a 3.6-metre telescope at the European Southern Observatory in Chile. It was specially designed to find planets by detecting the slight shift in the wavelength of the host star's light, caused by the gravitational pull of the planet. It took more than 100 observations to detect that shift, meaning that GJ 367b, besides being small, must also have a low mass.

Eventually, as observations with Harps accumulated, the researchers tied down the numbers: GJ 367b has a radius of 72% of Earth’s radius (to an accuracy of 7%), and a mass of 55% of Earth's mass (to an accuracy of 14%). The measurements tell us this planet is denser than Earth. Whereas Earth has a core of iron surrounded by a rocky mantle, this planet is so dense that it must be nearly all iron, making it similar to Mercury.

Mercury orbits the Sun every 88 days. Blasted by fierce sunlight, the “daytime” side is bare rock heated to 430?. GJ 367b is even more extreme. The recurrent transit dips tell us that it orbits its star in only eight hours. Being so close, the daytime side will be a furnace heated to 1,400?, such that even rock would be molten.

So how did it come to be? It’s possible that GJ 367b was once a giant planet with a vast, gaseous envelope, like Neptune. Over time, that gaseous envelope would have boiled off, leaving only the bare core that we see today. Or perhaps, as it formed, collisions with other proto-planets (planets in the process of forming) stripped off a mantle of rock, leaving only the iron core.

GJ 367b is, of course, way too hot to be habitable. But it’s one of very few rocky, Earth-sized planets astronomers have found so far. Its discovery shows that we can both find Earth-sized planets around other stars and measure their properties. The task now is to find them further from their star, in the “habitable zone”, where the surface temperature would allow water to exist as a liquid.