The remnant of a dead star predicted to cannonball through the outskirts of the solar system won’t do such a thing anyway.
On reexamination a white dwarf star just now 36 light years from Earth named WD0810-353 turned out to be quite normal. It is the only claim to strangeness is the powerful magnetic fieldaccording to a team of astronomers led by John Landstreet of the Armagh Observatory & Planetarium in the UK.
It’s this magnetic field, the researchers say, that led scientists to misinterpret the star’s trajectory through the Milky Way galaxy. Their findings, accepted in The Astrophysical Journalare available on the preprint server arXiv.
Nevertheless, WD0810-353 is interesting in its own right and could help scientists better understand how white dwarf magnetic fields evolve as they cool.
The solar system does not exist on its own. It belongs to a vibrant and fascinating stellar community, with each object on its own orbit or path around the galactic center. Some of those paths could lead to encounters with other stars, including our sun.
If another star collides with our solar system, the results can be quite disruptive, so astronomers are eager to find out which stars are on such a trajectory.
a paper published earlier this yearwritten by astronomers Vadim Bobylev and Anisa Bajkova of the Russian Academy of Sciences in Russia, describes a handful of candidates for close encounters in the future.
The most interesting of these was a white dwarf called WD0810-353. Using data from the Gaia mission, Bobylev and Bajkova calculated that WD0810-353 is traveling at a blistering speed of 373.7 (232 miles) kilometers per second.
They also calculate that WD0810-353 will pass the Sun within 0.49 light-years in just 29,000 years. That’s a distance of just 31,000 astronomical units, which would bring the white dwarf into the Oort cloud — a population of small, icy bodies estimated to orbit near the solar system’s boundary — and send the frozen blocks inward as comets. solar system would scatter.
It’s definitely an intriguing prospect, and one that will have a major impact on the future of the system.
![](https://www.sciencealert.com/images/2023/06/oort-cloud.jpg)
However, there are some problems with this finding. The Gaia data has given us the most accurate, three-dimensional map of the Milky Way to date, but there are significant limitations when it comes to using that data to calculate the velocities of white dwarfs.
In fact, a follow-up study conducted by astronomers Raúl de la Fuente Marcos and Carlos de la Fuente Marcos of the Complutense University of Madrid in Spain found that, while the white dwarf appears to be heading toward the solar system, its speed is far away. Their recalculationbased on the alpha line of hydrogen in its spectrum, found that WD0810-353 was moving at an absolutely insane speed of over 4,200 kilometers (just over 2,600 miles) per second.
Space events are often violent, especially when stars reach the bottom of their fusion fuel reserves, resulting in explosions that kick the remaining nuclei across the galaxy at high speed.
White dwarfs are such leftover nuclei for stars less than about 8 times the mass of the Sun (more massive stars collapse into neutron stars and black holes), and are often chased across the galaxy at high speed by uneven explosions; but we’ve never seen a runaway star so fast.
![](https://www.sciencealert.com/images/2023/06/cannonball-pulsar-642x558.jpg)
But, the Spanish astronomers noted, there was another possibility. They compared WD0810-353 to other white dwarfs with similar spectra using non-Gaia data and found a much quieter speed of about 60 to 70 kilometers per second.
Both of these new speeds, fast and slow, would rule out a close encounter between our solar system and WD0810-353 – but which one is it?
This is where Landstreet and his colleagues, Eva Villaver of the Astrobiology Center in Spain and Stefano Bagnulo of Armagh Observatory & Planetarium, pick up the lead. It’s possible, they note, that a powerful magnetic field could distort a white dwarf’s spectrum, so they obtained new spectra and performed new analyzes to derive the magnetic field.
They found that hydrogen’s alpha line was heavily shifted toward the bluer part of the spectrum due to the powerful magnetic field of the white dwarf. This can make the star appear to be moving towards us, as this movement can cause the light wavelengths to appear to compress and shorten toward the blue range, a phenomenon known as blueshifting.
In this case, Landstreet and his colleagues found that the blueshift results in an illusion of motion. The star’s speed, they found, is closer to about 83 kilometers (52 miles) per second. That means it’s not a hypervelocity or runaway star; and it won’t encounter the Oort Cloud in 29,000 years, if at all.
“Nevertheless, WD0810-353 is an intrinsically very interesting star,” write the researchers.
“It is one of the closest strong magnetic white dwarfs to Earth. At almost 3 billion years old, it is entering the phase of its cooling life where very strong magnetic fields are coming to the surface of middle-aged white dwarfs . It appears to have quite a complex distribution of local field strength over the visible surface. It will certainly be worth further spectropolarimetric monitoring and more detailed modeling of this object.”
The team’s paper has been accepted The Astrophysical Journaland is available at arXiv.