The position of Wolf 1061. Photo: UNSW
"This changes the circumstances on the surface of the planet substantially. You have one very hot side and one very cool side."
However, Dr Wright said that atmospheric modelling shows that heat can circulate around such a planet, albeit producing very high winds across the permanent twilight zone between the two sides.
The three newly detected planets orbit the small, relatively cool and stable star about every five, 18 and 67 days. Their masses are at minimum 1.4, 4.3 and 5.2 times that of Earth, respectively.
Lead researcher Duncan Wright, UNSW astronomer.
Dr Wright's team used the "doppler wobble method" to detect the planets. As smaller objects (planets) orbit a larger object (the star) it causes the central mass to "wobble", or rotate around the centre of their combined masses. These small movements create a doppler shift in the light reaching Earth depending on whether the star is moving towards or away from us. This is similar to how we can tell whether an ambulance is moving towards us or away depending on the pitch of its siren: the doppler effect.
By measuring the nature of this wobble from the star's light, scientists are able to get a very accurate picture of what is causing this movement. They are able to tell the number of objects, their distance from the star, as well as their estimated mass and orbital period.
"With our current measurements we are able to get precision of the motion of the star down to a 'walking speed'," Dr Wright said. "The motion of the star is detected at about a one metre per second precision."
Dr Rob Wittenmyer.
Dr Wright and his team used observations of Wolf 1061 collected by the HARPS spectrograph at the European Southern Observatory's 3.6 metre telescope in La Silla, Chile.
The next step will be for telescopes to look at Wolf 1061 and search for "transits" of the planets in front of the star. The small dip in light caused by the planets passing in front of the star will allow scientists to find out more about this planetary system.
"The close proximity of the planets around Wolf 1061 means there is a good chance these planets may pass across the face of the star. If they do, then it may be possible to study the atmospheres of these planets in future to see whether they would be conducive to life," said team member Rob Wittenmyer.
Dr Wright is keen for this discovery to have some galactic perspective.
"There is somewhere in the vicinity of 100 billion stars in our galaxy," he said. "We know that half of those stars are red dwarf stars, like Wolf 1061. From observations made by the Kepler space telescope, we also know that half of those stars are expected to have multiple rocky planets orbiting them.
"So if you consider our find in that context we are talking about billions and billions of rocky planets in our galaxy alone. And of course we know of more than 100 billion galaxies in the universe."
That's a lot of planets to explore.
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