Year: 2015

WASHINGTON (TIP): Bulk of potentially habitable planets – 92 per cent – are yet to be born in the universe, according to a new study that suggests there should at least be one billion Earth-sized worlds in the Milky Way at present.

When our solar system was born 4.6 billion years ago only eight per cent of the potentially habitable planets that will ever form in the universe existed, researchers said.

The bulk of those planets – 92 per cent – are yet to be born, according to the assessment of data collected by Nasa’s Hubble Space Telescope and the prolific planet-hunting Kepler space observatory.

“Our main motivation was understanding the Earth’s place in the context of the rest of the universe,” said study author Peter Behroozi of the Space Telescope Science Institute (STScI) in Baltimore, Maryland.

“Compared to all the planets that will ever form in the universe, the Earth is actually quite early,” said Behroozi.

Looking far away and far back in time, Hubble has given astronomers a “family album” of galaxy observations that chronicle the universe’s star formation history as galaxies grew.

The data show that the universe was making stars at a fast rate 10 billion years ago, but the fraction of the universe’s hydrogen and helium gas that was involved was very low.

Today, star birth is happening at a much slower rate than long ago, but there is so much leftover gas available that the universe will keep cooking up stars and planets for a very long time to come.

“There is enough remaining material [after the big bang] to produce even more planets in the future, in the Milky Way and beyond,” added co-investigator Molly Peeples of STScI.

Kepler’s planet survey indicates that Earth-sized planets in a star’s habitable zone, the perfect distance that could allow water to pool on the surface, are ubiquitous in our galaxy.

Based on the survey, scientists predict that there should be one billion Earth-sized worlds in the Milky Way galaxy at present, a good portion of them presumed to be rocky. That estimate skyrockets when you include the other 100 billion galaxies in the observable universe.

This leaves plenty of opportunity for untold more Earth-sized planets in the habitable zone to arise in the future.

The last star isn’t expected to burn out until 100 trillion years from now. That’s plenty of time for literally anything to happen on the planet landscape.

The researchers say that future Earths are more likely to appear inside giant galaxy clusters and also in dwarf galaxies, which have yet to use up all their gas for building stars and accompanying planetary systems.

By contrast, our Milky Way galaxy has used up much more of the gas available for future star formation.

Scientists have discovered two extremely hot and big stars locked in a death dance with a dramatic and violent end the only way out. They found the strange pair in the Tarantula Nebula, some 160,000 light years away.

The international team of scientists used the Very Large Telescope (VLT) located in Chile’s Atacama Desert to find this pair.

The VLT is managed by the multi-government European Southern Observatory (ESO) headquartered near Munich, Germany.

The two star system, called VFTS 352, is composed of two very hot, bright and massive stars that orbit each other in little more than a day. The centres of the stars are separated by just 12 million kilometers and their surfaces have started overlapping. The combined mass of the pair is about 57 times that of the Sun and its surface temperatures are above 40 000 degrees Celsius. This makes it the biggest and hottest ‘overcontact’ double star systems found.

Such a system is very rare because this phase in the life of the stars is short, making it difficult to catch them in the act. Because the stars are so close together, astronomers think that strong tidal forces lead to enhanced mixing of the material in the stellar interiors.

“The VFTS 352 is the best case yet found for a hot and massive double star that may show this kind of internal mixing,” explains lead author Leonardo A. Almeida of the University of Sao Paulo, Brazil. “As such it’s a fascinating and important discovery.”

Astronomers predict that VFTS 352 will face a cataclysmic fate in one of two ways. The first potential outcome is the merging of the two stars, which would likely produce a rapidly rotating, and possibly magnetic, gigantic single star. “If it keeps spinning rapidly it might end its life in one of the most energetic explosions in the Universe, known as a long-duration gamma-ray burst,” says the lead scientist of the project, Hugues Sana, of the University of Leuven in Belgium.

The second possibility is explained by the lead theoretical astrophysicist in the team, Selma de Mink of University of Amsterdam: “If the stars are mixed well enough, they both remain compact and the VFTS 352 system may avoid merging. The components would likely end their lives in supernova explosions, forming a close binary system of black holes. Such a remarkable object would be an intense source of gravitational waves.”

But, regardless of how VFTS 352 meets its demise, this system has already provided astronomers with valuable new insights into the poorly understood evolutionary processes of massive overcontact binary star systems.