First Hints of a Planet Orbiting in a White Dwarf's Habitable Zone

A distant white dwarf is surrounded by space rocks marching in perfect time. This observation offers hints of what may be the first planet we have detected in the habitable zone of one of these stellar corpses, suggesting that they might be just as good for life as bigger, younger stars. From a report: "A lot of people think of a white dwarf as a dead system or a dead end, but this tells us that there is a lot of stuff going on around white dwarfs," says Jay Farihi at University College London. He and his colleagues spotted these hints while observing a star called WD 1054-226, which lies about 118 light years away, using several powerful telescopes. They found that something appeared to be regularly passing in front of the star, causing dips in its light. The biggest dip happened every 23.1 minutes, in a pattern that repeated every 25 hours.The measurements indicate, the report says, that the star is surrounded by a ring of 65 comet-sized or moon-sized objects, remarkably evenly spaced in their orbits.

How so close?

[Klaxton]

From the article; "researchers calculated that the orbiting objects are about 2.6 million kilometres from the star – about 4 per cent of the distance between Mercury and the sun". And "the bits of cosmic debris are kept in order by the gravitational pull of a planet orbiting slightly further away from the star".

I'm wondering how things could be this close to the dwarf.

Not an expert, but it is my understanding that the typical stellar evolution that results in a white dwarf would have had the star puff

Those could be

[www.sorehands.com]

Those objects could be the missing StarLink satellites.

Re:

[Eunomion]

Rubble sounds more likely. And it could have migrated inward due to interaction with lingering dust, before reestablishing a stable resonance closer in.

Re:

[UnknowingFool]

1) Not all white dwarfs are the result of stars that have passed through a red giant star phase. Some stars never have enough mass to puff up. 2) Not all planets remain in the same orbits for the entirety of time. Many star systems have been discovered with gas giants very close to the star which could have never formed where they currently orbit. Those gas giants had to be formed further away from the star then get pulled in over time.

Re:

[Klaxton]

Do you have a reference for "Some stars never have enough mass to puff up"? It seems to me that any star with enough original mass to have become a white dwarf will have needed to expel all of its gas, which would have meant an extended gas envelope.

Re:How so close?

[UnknowingFool]

White Dwarfs: [wikipedia.org]

White dwarfs are thought to represent the end point of stellar evolution for main-sequence stars with masses from about 0.07 to 10 [solar masses]

Stellar Evolution [wikipedia.org]:

Recent astrophysical models suggest that red dwarfs of 0.1 [solar masses] may stay on the main sequence for some six to twelve trillion years, gradually increasing in both temperature and luminosity, and take several hundred billion years more to collapse, slowly, into a white dwarf. Such stars will not become red giants as the whole star is a convection zone and it will not develop a degenerate helium core with a shell burning hydrogen. Instead, hydrogen fusion will proceed until almost the whole star is helium.

Again not all stars follow the same path.

Re:

[Klaxton]

Thanks for the references, but what I am reading there is that only stars with between between 0.5 and 8 solar masses could become a white dwarf and they do expand and blow off their atmosphere. Smaller stars might eventually become dwarfs, but it would take far longer than the current age of the universe.

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[UnknowingFool]

Some stars do not become red giants which was the point. That is as far as modeling suggests. It is possible that it never happens in reality, but no one has lived long enough to observe a whole star's life cycle.

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[Forty Two Tenfold]

So it cannot be this type of white dwarf, because the Universe is too young.

Dyson Swarm?

[zarmanto]

I'm probably going out on a limb here... but in a crazy reality where science fiction and theory collide, we could possibly be observing what happens when a race becomes sufficiently advanced to terraform their home planet into a Dyson Swarm [wikipedia.org]. In a few hundred years, perhaps they'll even start the process of creating a Dyson Bubble.

I know, I know... probably too fantastical to be what we're really seeing, here. But an amusing thought, nonetheless.

Re:

[Waffle Iron]

Unfortunately, no matter how advanced they have become, they still need to continuously remind their citizens:

"Do NOT EVER look directly at the white dwarf!!"

JWST

[timeOday]

Is this something the JWST will be able to take a much closer look at very soon? I wonder if the astronomers who made this discovery can get time on JWST - or if not, what they will do because suddenly WWII breaks out and all you have is a Fokker biplane.

Re:

[UnknowingFool]

JWST is designed for infrared detection and the priority would be areas that are not observable due to dust like the center of the Milky Way. While JWST might be able to look at this, it is not likely a high priority.

Unlikely coincidence

[Klaxton]

The diameter of a typical white dwarf is thought to be about the same as Earth. Things orbiting it in a plane would have to be lined up with our viewpoint to a pretty high exactitude in order to actually transit the star at a distance of 2.6 million kilometers.

It seems like that would be very rare and unlikely to come across unless most or all white dwarf stars have objects in orbit and we just happened to spot one. Or maybe the shedding of the gas envelope disrupts anything that would have been orbiting in a plane, and the dwarf eventually winds up with a shell of orbiting objects. That would make it more likely to see transits.

Sure, but our ow moon is in the habitable zone too

[mark-t]

And I estimate it will be approximately as lifeless.

This star is dead. All that remains is the afterglow of its own heat, as it will slowly cools down to the ambient temperature of space, and over the course of billions of years the habitable zone will slowly shrink. I do not think this planet will be in the habitable zone of its parent long enough for life to emerge there.