This text refer to question.
Can a planet survive the death of its sun? Scientists find two that did.
Natalie Batalha has had plenty of experience fielding questions from both layfolk and other scientists over the past couple of years — and with good reason. Batalha is the deputy principal investigator for the spectacularly successful Kepler space telescope, which has found evidence of more than 2,000 planets orbiting distant stars so far — including, just last week, a world almost exactly the size of Earth.
But Kepler is giving astronomers all sorts of new information about stars as well, and that’s what an European TV correspondent wanted to know about during an interview last year. Was it true, she asked, that stars like the sun will eventually swell up and destroy their planets? It’s a common question, and Batalha recited the familiar answer, one that’s been in astronomy textbooks for at least half a century: Yes, it’s true. Five or six billion years from now, Earth will be burnt to a cinder. This old news was apparently quite new to the European correspondent, because when she reported her terrifying scoop, she added a soupçon of conspiracy theory to it: NASA, she suggested, was trying to downplay the story.
It was not a proud moment for science journalism, but unexpectedly, at about the same time the European correspondent was reporting her nonbulletin, Kepler scientists did discover a whole new wrinkle to the planet-eating-star scenario: it’s apparently possible for planets to be swallowed up by their suns and live to tell the tale. According to a paper just published in Nature, the Kepler probe has taken a closer look at a star called KOI 55 and identified it as a “B subdwarf”, the red-hot corpse of a sunlike star, one that already went through its deadly expansion. Around it are two planets, both a bit smaller than Earth — and both so close to their home star that even the tiniest solar expansion ought to have consumed them whole. And yet they seem, writes astronomer Eliza Kempton in a Nature commentary, “to be alive and well. Which begs the question, how did they survive?”
How indeed? A star like the sun takes about 10 billion years to use up the hydrogen supply. Once the hydrogen is gone, the star cools from white hot to red hot and swells dramatically: in the case of our solar system, the sun’s outer layers will reach all the way to Earth. Eventually, those outer layers will waft away to form what’s called a planetary nebula while the core shrinks back into an object just like KOI 55.
If a planet like Earth spent a billion years simmering in the outer layers of a star it would, says astronomer Betsy Green, “just evaporate. Only planets with masses very much larger than the Earth, like Jupiter or Saturn, could possibly survive.”
And yet these two worlds, known as KOI 55.01 and KOI 55.02, lived through the ordeal anyway. The key to this seeming impossibility, suggest the astronomers, is that the planets may have begun life as gas giants like Jupiter or Saturn, with rocky cores surrounded by vast, crushing atmospheres. As the star expanded, the gas giants would have spiraled inward until they dipped into the stellar surface itself. The plunge would have been enough to strip off their atmospheres, but their rocky interiors could have survived — leaving, eventually, the bleak tableau of the naked cores of two planets orbiting the naked core of an elderly star.
But Kepler is giving astronomers all sorts of new information about stars as well, and that’s what an European TV correspondent wanted to know about during an interview last year. Was it true, she asked, that stars like the sun will eventually swell up and destroy their planets? It’s a common question, and Batalha recited the familiar answer, one that’s been in astronomy textbooks for at least half a century: Yes, it’s true. Five or six billion years from now, Earth will be burnt to a cinder. This old news was apparently quite new to the European correspondent, because when she reported her terrifying scoop, she added a soupçon of conspiracy theory to it: NASA, she suggested, was trying to downplay the story.
It was not a proud moment for science journalism, but unexpectedly, at about the same time the European correspondent was reporting her nonbulletin, Kepler scientists did discover a whole new wrinkle to the planet-eating-star scenario: it’s apparently possible for planets to be swallowed up by their suns and live to tell the tale. According to a paper just published in Nature, the Kepler probe has taken a closer look at a star called KOI 55 and identified it as a “B subdwarf”, the red-hot corpse of a sunlike star, one that already went through its deadly expansion. Around it are two planets, both a bit smaller than Earth — and both so close to their home star that even the tiniest solar expansion ought to have consumed them whole. And yet they seem, writes astronomer Eliza Kempton in a Nature commentary, “to be alive and well. Which begs the question, how did they survive?”
How indeed? A star like the sun takes about 10 billion years to use up the hydrogen supply. Once the hydrogen is gone, the star cools from white hot to red hot and swells dramatically: in the case of our solar system, the sun’s outer layers will reach all the way to Earth. Eventually, those outer layers will waft away to form what’s called a planetary nebula while the core shrinks back into an object just like KOI 55.
If a planet like Earth spent a billion years simmering in the outer layers of a star it would, says astronomer Betsy Green, “just evaporate. Only planets with masses very much larger than the Earth, like Jupiter or Saturn, could possibly survive.”
And yet these two worlds, known as KOI 55.01 and KOI 55.02, lived through the ordeal anyway. The key to this seeming impossibility, suggest the astronomers, is that the planets may have begun life as gas giants like Jupiter or Saturn, with rocky cores surrounded by vast, crushing atmospheres. As the star expanded, the gas giants would have spiraled inward until they dipped into the stellar surface itself. The plunge would have been enough to strip off their atmospheres, but their rocky interiors could have survived — leaving, eventually, the bleak tableau of the naked cores of two planets orbiting the naked core of an elderly star.
Internet: <www.time.com> (adapted).
According to the text, judge if the item below about Natalie Batalha are right (C) or wrong (E).
Natalie Batalha is used to talking about her research to specialists and non-specialists alike.
