A gas giant planet orbiting the remains of a dead star has revealed to astronomers what our solar system might look like billions of years ago.
- Astronomers have found the first pair of star planet that looks like it will end our solar system
- In about 5 billion years, the Sun will inflate and swallow the inner planets
- The finding shows that Jupiter could survive the evolution of the Sun and turn it into a red giant star.
Detection is the first to detect a Jupiter-like planet orbiting a white dwarf at a distance we might expect when a star runs out of fuel and dies.
An international team of astronomers, including Joshua Blackman of the University of Tasmania, reports its celestial revelation in today’s Nature magazine.
“It was a very serendipitous discovery,” Dr. Blackman said.
Jonti Horner, an astronomer at the University of South Queensland who did not participate in the study, agreed.
“It shows us that when the Sun goes through this process, the giant planets are probably far enough away to survive.”
What is reserved for the Sun?
Astronomers do not know for sure how the Sun will behave over the next 10 billion years or so, but they have a good idea.
And it is a destination destined for the vast majority of stars in our galaxy, the Milky Way.
Right now, the Sun, which is a fairly typical “main sequence” star, is 4.6 billion years old. The heat and light it emits occurs as it fuses hydrogen with heavier elements.
But eventually, in about five hundred and six billion years, its hydrogen inventory will be depleted.
The Sun’s core will contract and collapse, and its outer layers will swell as they evolve into a red giant, Dr. Blackman said.
The surface of the inflated Sun will begin to slowly but inexorably invade the Solar System.
And it’s bad news for Earth.
“But Mars and the gas giants beyond will survive. This is the predicted general model of what will happen.”
After a few hundred million years or so, the Sun will drag the sparse envelope into space, leaving behind a dense, dead core: a white dwarf.
But the planets tilted to get out of the Sun. it is possible that the red giant phase is still there. They just won’t be that close.
Because its mass will be less than its peak when it burns hydrogen, the gravitational pull of the white dwarf will not be as strong and the remaining planets will orbit further than before.
And this is what Dr. Blackman and his colleagues found that they were passing for the first time in another solar system.
How to see ‘dark’ objects in space
Many distant stars cannot be “seen” by traditional telescopes, so they and other faint objects are detected by a technique called gravitational microlensation.
It is based on the idea that the gravitational field of an object (like a white dwarf) distorts the light shining from a star behind it, like a lens.
If the stars literally align with the Earth, astronomers see that the light from the farthest star intensifies and sinks into a curve, called the Einstein ring, as it bends around the white dwarf. .
When the stars move out of alignment, Einstein’s ring fades.
The white dwarf and its gas giant, which are about 6,500 light-years away, were first spied on in 2010 with a telescope at the Mount John Observatory in New Zealand, but it would be years before astronomers would find out exactly what they had found.
When Dr. Blackman joined the project in 2016, there were more telescopes that had observed the target event, including the much larger and more powerful Keck Telescope at Mauna Kea in Hawaii.
“We expected the star to be like our Sun, a main sequence star, which is what we normally see,” he said.
They also saw “bumps” in Einstein’s curved ring of light, he added: signs of a planet hitting the white dwarf, closer than Jupiter the Sun today, but at the expected distance of a gas giant who survived the death of his star.
A different kind of exoplanet
Gravitational microlensation has not found nearly as many exoplanets as other detection methods, only because it is based on the random alignment of stars.
Astronomers do not know when these events will occur, so they point their telescopes at space and wait for it to happen.
But gravitational microlensation can pick up exoplanets that other methods cannot, according to Professor Horner.
The transit method, in which telescopes capture moments, but regularly, in the luminosity of a star while a planet orbits blocking light, is good for finding bright stars with large planets orbiting nearby.
The radial velocity method is also skewed toward large planets orbiting its star, because it detects the ever-so-slight oscillation of a star caused by the gravitational pull of a planet.
Gravitational microlensation can capture dead stars that emit little light and the planets are sitting farther away.
“Think of it as a census and you’re trying to understand the breadth of humanity,” Professor Horner said.
“The traffic method is great for finding kids who are in kindergarten, the radial speed method is good for finding kids in elementary school.
More telescopes, more observations
It’s not the first time a Jupiter-like planet has been seen orbiting a white dwarf. A handful have been found, like the one reported last year, Dr. Blackman said.
“But none of this is similar to what we expect to happen.
“Most are very close to their host star, like a planet with a mass of Jupiter ten times closer than Mercury, while our planet is in line with the traditional expectation of what will happen to the solar system.”
He added that there will be more Jupiter-like planets whispering around the dead remains of his dead star.
The next Roman Space Telescope, destined for launch in mid-late 2020, will look for exoplanets using gravitational microlensation.
The Hubble Space Telescope and the upcoming launch of the James Webb Space Telescope could also be hired to help them, Dr. Blackman said.
“They can see the sky much deeper and we hope to be able to get a direct detection of the white dwarf in the future.”