Achi news desk-
Our Sun is our best friend and our worst enemy. On the one hand, we owe our existence to our star. The Earth and the other planets in the Solar System were formed from the same cloud of gas and dust as the Sun.
And without its light, there could be no life on this planet. On the other hand, there will come a day when the Sun will end all life on Earth and, ultimately, destroy the Earth itself.
The risks that stars can pose to their planets are highlighted by a new study published in Nature. The authors looked at stars similar to our Sun and found that at least one in every 12 stars exhibits traces of metals in its atmosphere. These are believed to be the scars of planets and asteroids that have been swallowed by the stars.
Planets should never get too comfortable as they orbit their parent star, as there are at least two ways their star can betray their trust and ensure their violent demise.
Tidal disruption
The first is through a process known as “tidal disruption”. As a planetary system forms, some planets will find themselves orbiting their star along paths that are either not perfectly circular or are slightly inclined in relation to the star’s plane of rotation. When that happens, the gravitational force exerted by the star on the planet will slowly correct the shape or alignment of the wayward planet’s orbit.
In extreme cases, the gravitational force applied by the star will destabilize the planet’s orbit, slowly pulling it closer and closer. If the unhappy planet wanders too close, it will be torn apart by the star’s gravity. This happens because the side of the planet facing the star is slightly closer than the side facing away (the difference is the diameter of the planet).
The strength of the gravitational pull exerted by the star depends on the distance between it and the planet, so that the side of the planet facing the star feels a slightly stronger pull than the side facing away.
On Earth, this difference in the strength of the gravitational force creates the daily ebb and flow of the tides. In essence, the Sun is trying to deform the Earth, but it is far enough away that it only manages to draw on the waters of its seas. But a planet dangerously close to its star will see its crust and core pulled apart by these tides.
If the planet is not too close to the star, its shape will be deformed into an egg shape. A little closer to the star, and the difference between the gravitational pull on its different sides will be enough to tear it apart completely, reducing it back to a cloud of gas and dust that spirals into the star and evaporating in her hellish fires.
The process of tidal disturbance was first suggested about 50 years ago. For the past few decades, astronomers—including my group—have seen dozens of bright tidal disruption flares caused by stars being torn apart by supermassive black holes at the center of galaxies.
NASA/JPL-Caltech
Last year, for the first time, a group of astronomers reported seeing a similar dimming flash consistent with a planet being disrupted and consumed by its star.
Tidal disruption of planets can be quite common, as shown by the new finding that at least 1 in 12 stars show signs of having ingested planetary material.
Other studies have found that between a quarter and a half of all white dwarfs – the remnants of stars up to twice as massive as our Sun – wear similar scars. As their name suggests, white dwarfs are white hot. With surface temperatures of tens of thousands of degrees, the hottest white dwarfs emit ultraviolet and X-ray light energetically enough to vaporize their orbiting planets.
The End of the Earth
Rest assured; The earth will not be destroyed by tidal disturbances. The end of our planet will come in about five billion years, when the Sun will transform into a red giant.
Stars are powered by a process called fusion, where two light elements are combined to make a heavier one. All stars begin their lives fusing the element hydrogen in their cores to the element helium. This fusion process both stabilizes them against implosion, due to the relentless pull of gravity, and creates the light that makes them shine. Our Sun has been fusing hydrogen into helium for about 4.5 billion years.
But 4.5 billion years from now, the hydrogen in the Sun’s core will run out. All fusion in the core will cease, and gravity, unopposed, will force the star to contract. As the core contracts, it will heat up until the temperature is high enough for helium to fuse into carbon.
Fusion will once again stabilize the star. In the meantime, however, the star’s outer envelopes will expand and cool, giving the massive star a redder color. As the red giant Sun expands, it will engulf Mercury, Venus and Earth – it may even reach all the way out into the orbit of Mars.
The Earth may have five billion years to go, but we will not be here to see its extinction. As the Sun burns through its hydrogen stores, it grows steadily brighter: every billion years, its luminosity increases by about 10%.
A billion years from now, the Sun will be bright enough to boil the Earth’s oceans. So, the next time you bask in the warm rays of the Sun, remember: it has come into us.
