How will the Solar System die? This is a very important question that many researchers have pondered, using our knowledge of physics to create complex theoretical models. We know that the Sun will eventually be a “Puting dwende”, A burnt remaining star whose dim light gradually disappeared into the darkness. This change will involve a violent process that will destroy an unknown number of its planets.
So which of the planets will survive the death of the Sun? One way to find the answer is to look at the fate of other similar planetary systems. This proved difficult, however. The weak radiation from the white dwarfs makes it difficult to see exoplanets (planets around stars other than our Sun) that have survived this stellar transformation – they are literally in the dark.
In fact, more 4,500 exoplanets currently known, very few white dwarves have been found around – and the location of these planets suggests that they got there after the star’s death.
This lack of data has painted an incomplete picture of our own destiny on the planet. Unfortunately, we are now filling in the gaps. In our new paper, published in Nature, we reported the discovery of the first known exoplanet to survive the death of its star without altering its orbit by other moving planets – around at a distance comparable between the planets of the Sun and the Solar System.
A planar Jupiter
The new exoplanet, which we discovered along with Keck Observatory in Hawaii, is particularly similar to Jupiter in both mass and orbital separation, and gives us an important snapshot of the planet’s survivors around dying stars. The transformation of a star into a white dwarf involves a violent stage in which it becomes a swollen “red giant”, also known as a “giant branch”Star, hundreds of times bigger than ever. We believe that this exoplanet has only survived: if at first it was closer to the parent star, it would be swallowed up by the expanding star.
When the Sun eventually becomes a red giant, its radius will reach outside the Earth’s current orbit. That means the Sun will (probably) swallow Mercury and Venus, and possibly Earth – but we’re not sure.
Jupiter, and its moons, are expected to survive, though previously we did not know for sure. But as we discover this new exoplanet, we will be more certain that Jupiter will actually capture it. Moreover, the margin of error in the position of this exoplanet could mean that it is almost half as close to the white dwarf as Jupiter that is currently on the Sun. If so, that is further evidence for the assumption that Jupiter, and Mars will capture it.
So can any life survive this change? A white dwarf can give life to moons or planets that end up being close to it (about one-tenth the distance between the Sun and Mercury) in the first few billion years. After that, there won’t be enough radiation to sustain anything.
Asteroids and white dwarfs
Although it’s hard to find planets orbiting white dwarves, what’s easier to see the asteroids separated near the surface of the white dwano. For exoasteroids to get close to a white dwarf, they need to have enough momentum given to them by the surviving exoplanets. Therefore, exoasteroids have long been assumed evidence that exoplanets are also present.
Our discovery finally provides confirmation of this. Although in the system discussed in the paper, current technology does not allow the detection of any exoasteroids, at least for now we have put together different parts of the fate puzzle by combining evidence from different white dwarf system.
The link between exoasteroids and exoplanets also applies to our own Solar System. Individual objects in the main asteroid belt and Kuiper belt (a disc in the outer Solar System) are likely to survive the Sun’s death, but some will be moved by the gravity of one of the remaining planets toward the white dwarf’s surface.
Prospects of future discovery
The new white dwarf exoplanet has been found in what is known as microlensing detection method. It looks at how much light bends due to a strong gravitational field, which occurs when a star is temporarily aligned with a more distant star, as seen from Earth.
Gravity from the front of the star amplifies the light from the star behind it. Any planets orbiting the star in front will bend and feather this magnified light, how can we find them. The white dwarf we are investigating is a quarter of the way to the center of the Milky Way galaxy, or about 6,500 light years away from our Solar System, and the more distant star is in the center of the galaxy.
A key feature of the microlensing technique is that it is sensitive to the planets which stars orbit at the Jupiter-Sun distance. Other known planets on which white dwarfs orbit are found have different techniques that are sensitive to different star-planet separations. Two examples relate to planets that survived the transformation of a star into a white dwarf and ended up closer to it than before. One was found by transit photometry – a technique to explore the planets as they pass in front of a white elf, which creates a dip in the light received by the Earth – and the rest is discovered by discovering evaporating atmosphere of the planet.
An additional discovery strategy – astrometry, which precisely measures the movement of white dwarfs in the sky – also predicted to yield results. In a few years, astrometry from Gaia Mission expected to find about a dozen planets orbiting white dwarfs. Perhaps it could offer better evidence about exactly how the Solar System will die.
These different discovery techniques are great for potential future discoveries, which could offer additional insight into the fate of our own planet. But for now, the newly discovered Jupiter -like exoplanet provides the clearest glimpse into our future.