Could the Quadrillions of Nomad Planets in Milky Way Sustain Life? Astrobiologists Say "Yes"

 

                        

A recent study proposes the galaxy is crowded with nomad planets adrift in space. If this is the case, nomad planets may play a dynamic role in the universe. Titled "Nomads of the Galaxy," the authors proposed an upper limit to the number of nomad planets that might exist in the Milky Way Galaxy: 100,000 for every star. And because the Milky Way is estimated to have 200 to 400 billion stars, that could put the number of nomad planets in the quadrillions.

If this proposal is correct, it could be that nomad planets play a dynamic role in the universe. In particular, if life can exist without the warmth of a nearby sun, it raises the possibility that, along with sustaining life, nomad planets could be transporting it as well. While just an idea, it's one that becomes more intriguing when considering not only the number of nomad planets, but the behavior of galaxies.

"In the 20th century, many eminent scientists have entertained the speculation that life propagated either in a directed, random or malicious way throughout the galaxy," said Roger D. Blandford, A co-author of the recent study and director of the Kavli Institute for Particle Astrophysics and Cosmology (KIPAC) at Stanford University and the SLAC National Accelerator Laboratory.

"One thing that I think modern astronomy might add to that is clear evidence that many galaxies collide and spray material out into intergalactic space. So life can propagate between galaxies too, in principle."

I'm really curious about the exchange of planets between solar systems," said Louis E. Strigari, lead author of the study and research associate at KIPAC and the SLAC, " How often does it happen, and how far can a nomad planet travel? How many trips around our galaxy does it make? I think these are brand new, basic questions. And I think that's an exciting place to be."

"If you imagine the Earth as it is today becoming a nomad planet... life on Earth is not going to cease," said Dimitar D. Sasselov, Professor of Astronomy at Harvard University and the Harvard-Smithsonian Center for Astrophysics, and the Director of the Harvard Origins of Life Initiative. "That we know. It's not even speculation at this point. ...[Scientists] already have identified a large number of microbes and even two types of nematodes that survive entirely on the heat that comes from inside the Earth."

The image at the top of the page is an artistic rendition of a nomad object wandering the interstellar medium. The object is intentionally blurry to represent uncertainty about whether or not it has an atmosphere. A nomadic object may be an icy body akin to an object found in the outer Solar System, a more rocky material akin to asteroid, or even a gas giant similar in composition to the most massive Solar System planets and exoplanets. 

Journal reference: Monthly Notices of the Royal Astronomical Society  

The Daily Galaxy via The Kavli Foundation

Image credit: With  thanks to Greg Stewart/SLAC

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Comments

[ecurve]

Perhaps we have been looking for signs of intelligent (advanced) life under the wrong criteria. Instead of looking for Dyson Spheres, we should look at Nomad Planets. The RTV of the future.

[matt]

Not likely that life above the microbe level could survive w/o a star. If they are functioning as a carrier the life would have had to develop within a solar system, so we're not really making much progress here.

[Lolington Roflwraithe, esq.]

You've got to be careful with that 100.000 rogue planets per star figure - it's a potential upper bound that was thrown out by ONE group of researchers. Other groups speak of "nearly two" rogue planets per star. That's still a lot of rogue planets right there.

[MBcraft]

Does anyone have a link to the article that postulates there are 100.000 nomad planets for every star? That number just seems really out there to me. Going by what we have seen and detected so far, i would figure the estimate to be much more conservative.

[Bob Greenwade]

While not really on the same page as Matt, I'm at least in the same chapter.

I could see how some process could lead to the development of microbial life on a rogue planet. For example, if it has a moon, the moon could create tidal and tectonic forces in that planet to heat it up (or vice versa, the planet affecting the moon); or perhaps the rogue could drift close enough to a life-bearing star system to pick up some microbes.

But I think we're getting a little too excited over the possibility. I can see how a rogue planet's ecosystem could develop past microbes, especially if a primordial plant were to develop bioluminescence, but I'd also think that this would be extraordinarily rare.

In fact, I doubt that it would be common enough to warrant much attention, especially at this stage of our exploration, from anyone other than science-fiction writers. (Heck, I'd pick up on the idea myself if my stories had more to do with space, but they rely instead on travel between alternate quantum timelines.)

I don't think that Dr. Blandford, Dr. Strigari, and their colleagues are wasting their time; on the contrary, I think their research can help in other areas. But I do think this is less exciting than it's being made to sound.

[Greg]

I am also finding this 100,000 planets per star thing hard to imagine. So our solar system potentially produced 100,000 planets and only 8 decided to stick around? And 8 seams to be alot of planets in one solar system based on what we are learning of others. Seems like one hell of an extreme upper limit to me.

[Ins0mniac]

Greg, you're not taking into account that PAST solar systems would also have had the ability to create rogue planets still in existence. The total number of stars to have ever existed in the galaxy would be a lot greater than the CURRENT solar systems in existence.

[resonanz]

Wouldn’t a rogue planet experience a steadily decreasing heat environment? After a few 100 million years of drifting or of vastly extended orbital motion away from a central star (a direct heat source, or source of gravitational tidal forces on an internal metal core), it would have a mean temperature close to absolute zero?

[Lolington Roflwraithe, esq.]

Ins0mniac, you make a valid point, but it's not like our sun is a 100th generation star - according to our current understanding to solar formation, it's more likely to be in the 2nd or 3rd generation population. The number of rogue planets being orders of magnitude higher than the number of stars ever to have existed strikes me as odd.

Again, the 100.000 figure was an UPPER LIMIT thrown into the room by Strigari et al (Monthly Notices of the Royal Astronomical Society) after earlier, more conservative estimates by Sumi et al (Nature) had spoken of "nearly two" rogues per star.

The truth is likely to be somewhere in between.

[Robert Munafo]

The article is called "Nomads of the Galaxy"; authors are Louis E. Strigari, Matteo Barnabe, Philip J. Marshall, Roger D. Blandford. The abstract and full text are on arxiv.org, use those names plus the article identifier "1201.2687" in a search engine to find the abstract and full text.