Kepler sees a mini-planet die as Earth-like planets wait to be born
Researchers using NASA’s rebooted Kepler spacecraft, now known as the K2 mission, have discovered evidence of a small, rocky object being torn apart as it spirals around a white dwarf star. The finding supports a long-held theory that white dwarfs can vaporize possible remnant planets that have survived in its planetary system.
“We are for the first time witnessing a miniature “planet” ripped apart by intense gravity, being vaporized by starlight and raining rocky material onto its star,” said Andrew Vanderburg, a graduate student from the Harvard-Smithsonian Center for Astrophysics in Cambridge, Massachusetts, and lead author of the paper published in Nature.
As stars similar to the Sun age, they expand into red giants and then begin to gradually nearly half of their mass, shrinking down to roughly the size of the Earth, approximately 1/100th of their original size. This dense, dead remnant of a star is called a white dwarf.
The diagram depicts a model of light curve shapes. The red line indicates the symmetric shape of a hypothetical Earth-size planet transit while the blue line is the asymmetric shape of the tiny disintegrating planet and its comet-like trailing dusty tail. The black dots are measurements recorded by the K2 mission of WD 1145+017. Image Credit: CfA /A. Vanderburg
The small planetary remnant is about the size of a large asteroid. It is the first planetary object to be confirmed transiting a white dwarf. The tiny planet orbits its white dwarf, WD 1145+017, once every 4.5 hours. This brief orbital period indicates that it is passing very close to the white dwarf and subject to searing heat and shearing gravitational force.
The scientific team led by Vanderburg found an unusual pattern in the light traces as the small planet transited WD 1145+017. Instead of the normal U-shaped pattern, there was an elongated, asymmetrical shape indicating that the tiny planet was leaving a trail of debris much like the trail of a comet.
“The eureka moment of discovery came on the last night of observation with a sudden realization of what was going around the white dwarf. The shape and changing depth of the transit were undeniable signatures,” said Vanderburg.
Another group of scientists using data from Kepler and the Hubble Space Telescope (HST) have released a theoretical study on the formation of potentially habitable planets. Observations made by Hubble indicate that the universe was making stars at a fast rate 10 billion years ago, but the amount of the universe’s hydrogen and helium used was very low. The current rate of star formation is much slower, but the amount of gas available indications that this process will continue far into the future.
The team’s findings suggest that when the Solar System formed 4.6 billion years ago, only eight percent of the Earth-like planets that will ever form had existed. The remaining 92 percent still wait to be born.
“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-like planets in a star’s habitable zone are very common in our galaxy. There may be as many as 1 billion Earth-sized planets in the Milky Way galaxy alone, and many of them are presumed to be rocky. The total number of Earth-like planets could be far greater considering that there are another 100 billion galaxies in the observable universe.
There is plenty of time for more Earth-like planets in the habitable zone to form in the future. The last star isn’t expected to burn out for 100 trillion years.
The researchers say that future Earth-like planets are mostly likely to form inside giant galaxy clusters and also in dwarf galaxies, which have yet to use up all of their gas for the formation of stars and their accompanying planets. The Milky Way galaxy, on the other hand, has used up much more of the gas available for future star formation.
Artist’s impression of innumerable Earth-like planets that have yet to be born over the next trillion years in the evolving universe. Image Credit: NASA, ESA, and G. Bacon (STScI)
Jim Sharkey
Jim Sharkey is a lab assistant, writer and general science enthusiast who grew up in Enid, Oklahoma, the hometown of Skylab and Shuttle astronaut Owen K. Garriott. As a young Star Trek fan he participated in the letter-writing campaign which resulted in the space shuttle prototype being named Enterprise. While his academic studies have ranged from psychology and archaeology to biology, he has never lost his passion for space exploration. Jim began blogging about science, science fiction and futurism in 2004. Jim resides in the San Francisco Bay area and has attended NASA Socials for the Mars Science Laboratory Curiosity rover landing and the NASA LADEE lunar orbiter launch.
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