Scientists using the European Southern Observatory’s HARPS planet hunter in Chile, are excited to report that they have identified a rare planet orbiting a star so similar to Earth’s sun that it has been called its “solar twin.” The planet joins the ranks of only a few others that have been found to be orbiting stars so similar to the sun, and is believed to be among the first to do so within a cluster.
The newly discovered planet was identified as one of three planets orbiting stars in a cluster of about 500 stars known as M67, located about 2,500 light-years from Earth. The cluster is one of the oldest known, about the same age as the Earth and sun at about 4 billion years. It is likely that the cluster was once home to many more stars but that some have dissipated over time, with the remaining stars continuing on as a result of the density of M67.
The planet of particular interest is orbiting a star called YPB-1194 that is of nearly identical size, temperature and age to the Earth’s sun, thus the dubbing as a “solar twin.”
While the sun and the newly discovered planet’s star may be quite similar, the planet itself does not appear to have much in common with the Earth. It is about 100 times larger than the Earth and is about 87 million miles closer to its star than Earth is to the sun. It is even closer to its star than the planet Mercury is to the sun, meaning that if it has a surface (it may just be a “gas giant), it is extremely hot and could not sustain life-giving water.
The important part of this discovery isn’t whether the newly discovered planet is similar to Earth or if it could sustain life, it is simply that it exists. Planets in star clusters are extremely rare. The finding indicates to scientists that stars that are virtual twins of the sun can form orbiting planets and that they can do so in a cluster. It raises the additional question of whether the sun may have been a part of a cluster at one time.
M67 is a popular area of study among astronomers. If all of the stars in the cluster were formed at around the same time and from the same material, as scientists believe is likely, then they can be compared directly. As a result the newly identified planet is likely to be thoroughly studied as well.
The two other planets identified in the cluster are also likely to be highly studied. One was determined to be orbiting an old red giant star, and the other is orbiting a star that is believed to be a bit smaller and cooler than the sun. Like the planet orbiting the sun’s twin, both are located much closer to their stars than Earth, again making any possibility of the existence of life quite unlikely.
The newly identified planets in M67 were the result of the careful monitoring of 88 stars in the cluster over a period of six years. The rare orbiting planets were identified through the observation of the stars’ “nearly imperceptible movements towards and away from Earth.”
By Michele Wessel