Nomads of the galaxy

May 23, 2012
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. (Image by Greg Stewart/SLAC)

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.

Recently, a study was published in the proposing planets simply adrift in space may be something of a common phenomenon. Aptly titled "Nomads of the Galaxy," the authors proposed an upper limit to the number of nomad planets that might exist in the : 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

"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 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."

Said Louis E. Strigari, lead author of the study and research associate at KIPAC and the SLAC, "I'm really curious about the exchange of planets between solar systems. 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."

As for whether a nomad planet could actually sustain life, the proof may be here on Earth. "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 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."

Explore further: Millisecond pulsars clearly demonstrate that pulsars are neutron stars

More information: www.kavlifoundation.org/scienc… -kipac-nomads-galaxy

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LariAnn
3.7 / 5 (3) May 23, 2012
IMHO, if an advanced civilization developed on a planet before it went rogue, they may have the tech to sustain their civilization even without a Sun to warm them. In that way, their whole planet becomes an interstellar craft that, depending upon speed, their direction of travel, and the nearest neighboring system, could enable their distant descendants to visit another world.
Lex Talonis
3.4 / 5 (5) May 23, 2012
Time - in the galactic scale - is a LONG time......

It's not impossible, just highly improbable.
kevinrtrs
1.6 / 5 (7) May 24, 2012
100000 seems to be quite a high figure, even if it's the theoretical limit. It might have been better to give an estimate of the average number instead. As it now stands, people will jump on this number and give mind-boggling figures - just as was done in the next line!
]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.
PhotonX
3.7 / 5 (3) May 24, 2012
The object is intentionally blurry to represent uncertainty about whether or not it has an atmosphere.

Well, isn't anything floating around in the void far from any star going to be as cold as hell? Any atmosphere would solidify and drop down the the surface, no? Anyway that was one of the justifications for getting the Pluto Express mission off as soon as we did.
AngryMoose
2 / 5 (1) May 24, 2012
I wonder if these extra bodies make up the mass required to forget about the dark matter idea.
DarkHorse66
not rated yet May 24, 2012
I wonder if these extra bodies make up the mass required to forget about the dark matter idea.

Probably not. In fact considering that roughly(!)70% of all of the universe is made up of dark energy and ~25% dark matter, that only leaves about 5% for normal matter!
http://science.na...-energy/
http://science.ho...ergy.htm
http://en.wikiped...k_energy
If your hypothesis were true, then that would mean that ~95% of ALL matter would need to be nothing but nomadic planets. That would imply a rough ratio of nearly 100 nomads for each star plus every 'captive' planet! Somehow I don't think that we have the evidence to support that scenario... :) Cheers, DH66
antialias_physorg
4 / 5 (4) May 24, 2012
Well, isn't anything floating around in the void far from any star going to be as cold as hell?

You forget that stuff like the Earth is just 30km of rock sitting on 13000 km of molten slag (minus the iron core). That heat in there is not dependent on the piddly littel bit of solar radiation we are getting (it's residual heat from planet formation, pressure induced heating by gravity and also heat from radioactive decay of heavier elements.) The 30km Earth crust and the atmosphere are pretty good at isolating this heat against cooling off.

Also remember that cooling in space only happens via radiation - not convection, conduction or condensation. Radiation alone is a very slow/inefficient process (one reason why the ISS, for example, has a lot of problems getting rid of excess heat while in the sun).