How will the Solar System end? This is a crucial question that scientists have been trying to answer. Researchers used their knowledge of physics and mathematics to develop complex theoretical models.
We know the Sun will eventually turn into a "white dwarf", which is a burned-out stellar remnant whose dimming light slowly fades into darkness. It will undergo a brutal transformation that will result in the destruction of uncounted planets.
Which planets will survive the demise of the Sun's sun? You can look at similar planetary systems to find out their fates.
However, this has been difficult. It is difficult to see exoplanets, which are planets orbiting stars other than our Sun, due to the weak radiation of white dwarfs.
Artist's impression showing the white dwarf system. (W. M. Keck Observatory/Adam Makarenko).
In fact, only a few of the more than 4,500 exoplanets currently known have been discovered around white dwarfs. The location of these planets suggests that they were there after the death star.
This is a partial picture of our planet's fate. We are filling in the blanks, however.
Our new Nature paper reports the discovery of an exoplanet that survived the death of its star. It is also the first exoplanet known to have its orbit modified by other planets. This distance is comparable to the distance between the Sun's and the Solar System planets.
Jupiter-like planet
The new exoplanet was discovered by the Keck Observatory in Hawaii. It is very similar to Jupiter in mass and orbital separation. This gives us a critical snapshot of planetary survivors around dying stars.
The violent phase during which a star transforms into a white dwarf is when it becomes a bloated red giant, also known as a "giant star branch", hundreds of times larger than before.
This exoplanet is believed to have survived. If it had been initially closer to its parent star it would have been engulfed in the star's expansion.
The Sun will eventually become a red giant and its radius will extend beyond Earth's current orbit. This means that the Sun will likely engulf Mercury, Venus, and possibly even the Earth. However, we aren't sure.
Although we didn't know for certain, Jupiter and its moons are expected to survive. We can be more certain that Jupiter will survive after the discovery of this new exoplanet.
The margin of error in this exoplanet's position could also mean that it is half as close to Jupiter as Jupiter is to the Sun. This is further evidence to support the assumption that Jupiter and Mars will succeed.
This transformation could not be reversed.
For the first few billion year, a white dwarf could power life on planets and moons that are very close to it (about one-tenth of the distance between Mercury and the Sun). There wouldn't be enough radiation for anything after that.
White dwarfs and asteroids
While planets orbiting white dwarfs are difficult to locate, it has been easier to spot asteroids that have broken up very close to the surface of white dwarfs.
Exoasteroids must have enough momentum from surviving exoplanets to be able to reach a white dwarf. Exoasteroids are therefore long believed to be evidence of exoplanets.
This is now confirmed by our discovery. While we cannot see any exoasteroids in the system discussed in this paper, our current technology allows us to piece together pieces of the puzzle that is planetary fate through the merging of evidence from various white dwarf systems.
Our Solar System is also affected by the exoasteroids/exoplanets link. The Sun will likely not destroy any of the objects in the Kuiper belt or asteroid main Belt. However, some objects may be moved towards the surface by gravity by one the remaining planets.
Future discovery prospects
Microlensing detection was used to find the new white dwarf exoplanet. This method examines how light bends when there is a strong gravitational force. This happens when a star aligns momentarily with another star.
The light from the star to the left magnifies the gravity of the foreground star. This magnified light will be bent and warped by any planets orbiting the star in front of it, which is how they can be detected.
We found that the white dwarf is about one-quarter the distance to the center of the Milky Way Galaxy. This is approximately 6,500 light years from our Solar System. The star further away is located in the middle of the galaxy.
The microlensing technique has a key characteristic: it is sensitive to the Jupiter-Sun distance orbiting stars. Other known white dwarf planets have been discovered using different techniques that are sensitive to different star separations.
Two examples concern planets that survived the transformation of a star into a white dwarf, and are now closer to it.
The first was detected by transit photometry, a technique to detect planets when they pass in front a white dwarf. The other was detected by the detection of the planet’s evaporating atmospheric.
Another detection technique, astrometry which measures precisely the movement of white dwarfs within the sky, is expected to also yield results.
Astrometry from Gaia will soon reveal about a dozen white dwarf planets. These could provide better evidence about how the Solar System will end.
These diverse discovery methods bode well for future discoveries, which could provide further insight into our planet's fate. The best glimpse into the future is provided by the recently discovered Jupiter-like exoplanet.
Dimitri Veras Associate Professor and STFC Ernest Rutherford Fellow of Astrophysics University of Warwick
This article was republished by The Conversation under Creative Commons. You can read the original article.
