How Many Loose Planets in the Milky Way?

Sky & Telescope ^ | February 29, 2012 | Monica Young

[SunkenCiv]

Researchers at the Kavli Institute for Particle Astrophysics and Cosmology (KIPAC) at Stanford University estimate that "nomad" planets, ejected from their home stellar system and now free-floating through the Milky Way, could outnumber stars by as many as 100,000 to 1. Earlier estimates were more like a handful to 1, though previous studies have only counted unbound planets more massive than Jupiter.

To estimate the number of unbound planets as small as Pluto that could be roaming the galaxy, Louis Strigari (KIPAC), lead author of the study, began with a basic rule of nature: where a few big objects are found, there are many more small, just like a few boulders may be surrounded by thousands of pebbles. Strigari and colleagues calculated the number of unbound planets by extrapolating from the small number detected so far by direct imaging and by gravitational microlensing.

Direct imaging has severe limits because planets are so faint. Microlensing offers more promise. It looks for the characteristic brightening and fading of a background star when an object, even one as wimpy as Pluto, passes nearly in front of it and bends its light slightly by gravity. So far, 24 planet-mass objects have been detected by microlensing -- 14 bound to their parent stars, 10 apparently not. Microlensing offers hope for detection of loose objects large and small even if they are completely dark, and even at great distances across the galaxy.

[mountainlion]

I was taught there were only 9 planets and that one found in another solar system would be called something else besides a planet. A planet used to be a large body orbiting around our sun. Who changed the rules?

[BipolarBob]

Loose women on loose planets? Ask Laz.

[bigheadfred]

And that’s another thing. 400 billion stars in the galaxy times 100,000 means that commute is going to be a BITCH.

That is a number so big it doesn’t have a name?

10,000 trillion?

[Wuli]

I realize the issue itself results from a statistical hypothesis which relies on a hypothesis - as yet unproven by empirical evidence, that presumes a material similarity (on average statisically) in the formation of solar systems.

I am frankly concerned that as much as I think there is room for federal funding of basic science (scientific questions far from deriving a profitable enterprise therefrom) that there is an excess of funding of the purely speculative science that is not only far distant from any pracitcal application or use but just as far distant from any practical, empirical proof (”string theory” for instance).

I think true scientific breakthroughs that have served humanity were at the time actual baby steps built on questions posed by previous steps that had already obtained proof, even though to most people at the time the result seemed like a great leap. But now, in my humble opinion, we have many public and privately funded scientists paid for pursing not “next steps” in science, but great leaps of imagination. Just my humble opinion.

[Mad Dawgg]

"How Many Loose Planets in the Milky Way?"

Word is Venus is one "Slutty Ho'" and is always trying to hook-up with Uranus...

[null and void]

10 quadrillion.

[alpo]

KIPAC? Is that near K-PAX?

[Oceander]

On a planet larger than Earth the combination of heat from internal nuclear processes such as fission and gravitational pressure could very well be sufficient to keep a planet warm enough to maintain a non-solid atmosphere. After all, stellar objects, from the Sun down to brown dwarfs, manage to maintain an atmosphere even though they're in the cold depths of space without a larger star to keep them heated. And the mass of interstellar bodies is more of a continuum with a not-so-bright-line division between planets and stars (bodies formed by accretion and bodies formed by collapse of interstellar gas). Further, theory discusses so-called "cold gas giants" which can radiate more heat than they receive from their host stars.

It is therefore not outside the realm of possibility for there to be bodies in interstellar space that are not "stars" properly speaking but which do generate sufficient internal heat to maintain a gaseous atmosphere.

[henkster]

I also wondered of the “loose planets” where another means of accounting for dark matter, and that’s why they came up with the 100,000:1 ratio.

I’ve never been comfortable with the theory of “Dark Matter.” I have a nagging suspicion that it’s a hypothesis created to patch a hole in a flawed underlying theory.

But, I’m not an astrophysicist, so I can nurse my ignorant prejudices all I want.

[Windflier]

To us accretionist’s the concept of a loose planet is heresy.

Why hasn't the asteroid belt accreted into a planet yet? I've been puzzling over that since I was a kid.

Not having studied it (at all), my working theory is that it once was a planet that was busted up by impact. The accretion process should be ongoing now.

[bert]

-——Why hasn’t the asteroid belt accreted into a planet yet——

Patience Grasshopper....... be patient

[Windflier]

Patience Grasshopper....... be patient

Well, I did say that my theory is that it's re-forming into a planet even now. Of course, that'll take a few billion years or so, but what the hey. I'm in no hurry.

[Mmogamer]

True I was just saying a rocky type like Earth probably couldn’t however.

[bigheadfred]

I'm in no hurry.

Good thing, too. Do you know how many Chinese asteroid miners that would put out of work?

[Oceander]

True I was just saying a rocky type like Earth probably couldn’t however.

Fair enough. On that point I think you're almost certainly correct; anything that was large enough, and radioactive enough, to keep itself heated wouldn't have a rocky surface; it might have some sort of a surface, but there would almost certainly have to be a lot more interchange between the atmosphere and the underlying, heated, materials than there is on a rocky body on a par with Earth.

[bert]

To get a feeling for current events and your seemingly correct thoughts on asteroids, bing “asteroid 2011”. They are here now!

Precisely where they are vectored we do not know......

eventually, though it is the Sun

[PapaBear3625]

Why hasn't the asteroid belt accreted into a planet yet? I've been puzzling over that since I was a kid.

Jupiter keeps disturbing the process.

[bigheadfred]

To get a feeling for current events

2011 was so yesterday. Bing "asteroid 2013". We got one headed our way NOW.

[bigheadfred]

UPCOMING CLOSE APPROACHES TO EARTH

1 AU = ~150 million kilometers
1 LD = Lunar Distance = ~384,000 kilometers

Object Name	Close Approach Date	Miss Distance (AU)	Miss Distance (LD)	Estimated Diameter*	H (mag)	Relative Velocity (km/s)
(2012 DP32)	2012-Mar-10	0.0362	14.1	36 m - 80 m	24.4	8.84
(2012 DH54)	2012-Mar-10	0.0085	3.3	7.6 m - 17 m	27.7	4.79
(2012 DF31)	2012-Mar-10	0.0546	21.3	34 m - 77 m	24.4	13.72
(2012 EJ1)	2012-Mar-10	0.0294	11.5	27 m - 60 m	25.0	9.67
(2011 UU106)	2012-Mar-11	0.1737	67.6	500 m - 1.1 km	18.6	8.81
(2012 DN14)	2012-Mar-12	0.0698	27.2	30 m - 68 m	24.7	4.33
(2012 EN3)	2012-Mar-12	0.0504	19.6	40 m - 90 m	24.1	9.06
(2012 DW60)	2012-Mar-12	0.0064	2.5	14 m - 31 m	26.4	5.64
(2012 BK11)	2012-Mar-12	0.1750	68.1	72 m - 160 m	22.8	3.03
(2010 SV3)	2012-Mar-12	0.0577	22.5	190 m - 430 m	20.7	15.34
(2010 XA11)	2012-Mar-12	0.1676	65.2	16 m - 36 m	26.1	7.87
(2010 CO1)	2012-Mar-12	0.1132	44.1	130 m - 290 m	21.5	13.73
192642 (1999 RD32)	2012-Mar-14	0.1488	57.9	1.5 km - 3.3 km	16.3	18.80
(2012 ER3)	2012-Mar-14	0.0575	22.4	34 m - 76 m	24.5	12.63
(2008 EY5)	2012-Mar-14	0.0882	34.3	250 m - 570 m	20.1	11.99
(2012 BB14)	2012-Mar-15	0.0483	18.8	27 m - 60 m	25.0	2.10
(2011 YU62)	2012-Mar-16	0.1885	73.4	830 m - 1.8 km	17.5	17.85
(2010 FN)	2012-Mar-19	0.1438	56.0	13 m - 28 m	26.6	11.18
(2012 BT23)	2012-Mar-20	0.1239	48.2	420 m - 940 m	19.0	13.11
(2012 DO8)	2012-Mar-20	0.1755	68.3	96 m - 210 m	22.2	7.26
(2012 DH4)	2012-Mar-21	0.0606	23.6	190 m - 420 m	20.7	15.55
(2011 SY120)	2012-Mar-21	0.0517	20.1	65 m - 150 m	23.1	17.55
(2001 QJ142)	2012-Mar-22	0.1909	74.3	55 m - 120 m	23.4	8.46
(2010 FR9)	2012-Mar-22	0.0479	18.6	16 m - 35 m	26.1	8.66
(2012 EB2)	2012-Mar-23	0.0395	15.4	32 m - 72 m	24.6	5.85
(2012 BS23)	2012-Mar-23	0.1580	61.5	140 m - 310 m	21.4	11.05
(2012 DW30)	2012-Mar-24	0.1191	46.3	77 m - 170 m	22.7	5.02
(2012 EC)	2012-Mar-24	0.1963	76.4	50 m - 110 m	23.6	2.95
(2012 DO)	2012-Mar-25	0.1061	41.3	240 m - 540 m	20.2	7.60
152754 (1999 GS6)	2012-Mar-26	0.1118	43.5	340 m - 760 m	19.5	11.71
(2011 GB55)	2012-Mar-27	0.1114	43.4	130 m - 280 m	21.6	16.14
(2002 EW8)	2012-Mar-28	0.1996	77.7	53 m - 120 m	23.5	13.67
(2012 CA55)	2012-Mar-30	0.0566	22.0	120 m - 270 m	21.7	9.26
(2008 GD)	2012-Mar-30	0.1687	65.6	300 m - 670 m	19.7	32.35
(2009 TP)	2012-Mar-31	0.1157	45.0	52 m - 120 m	23.5	3.72
(2008 CH70)	2012-Apr-01	0.0872	33.9	34 m - 77 m	24.4	9.06
(2011 FQ6)	2012-Apr-03	0.1784	69.4	7.5 m - 17 m	27.7	6.89
(2010 GD35)	2012-Apr-03	0.0630	24.5	33 m - 73 m	24.5	10.64
(2012 AA11)	2012-Apr-03	0.0729	28.4	270 m - 610 m	20.0	8.51
(2010 GE30)	2012-Apr-05	0.1353	52.7	49 m - 110 m	23.7	4.65
(2004 TB10)	2012-Apr-05	0.0967	37.6	150 m - 330 m	21.2	12.42
(2007 WU3)	2012-Apr-06	0.1831	71.3	56 m - 120 m	23.4	6.28
(2012 DX75)	2012-Apr-06	0.0603	23.5	210 m - 480 m	20.5	12.86
(2003 UD22)	2012-Apr-06	0.1711	66.6	320 m - 720 m	19.6	12.91
(1995 DW1)	2012-Apr-07	0.1712	66.6	160 m - 360 m	21.1	12.85
(2008 GG2)	2012-Apr-10	0.1445	56.2	78 m - 170 m	22.7	7.16
(2007 HC)	2012-Apr-10	0.1813	70.6	24 m - 53 m	25.2	11.34
(2009 HE60)	2012-Apr-10	0.1096	42.7	20 m - 44 m	25.7	4.71
(2004 FG11)	2012-Apr-10	0.0574	22.3	170 m - 390 m	20.9	25.09
(2006 UE17)	2012-Apr-12	0.1375	53.5	110 m - 250 m	21.9	8.99
(2004 RQ252)	2012-Apr-12	0.0441	17.2	90 m - 200 m	22.3	10.71
(2007 DK)	2012-Apr-13	0.1735	67.5	370 m - 840 m	19.3	12.73
(2003 GQ22)	2012-Apr-14	0.1179	45.9	170 m - 380 m	21.0	10.48
(2009 WD106)	2012-Apr-15	0.1927	75.0	500 m - 1.1 km	18.6	25.20
297274 (1996 SK)	2012-Apr-18	0.1726	67.2	1.0 km - 2.2 km	17.1	19.26
(2007 HV4)	2012-Apr-19	0.0122	4.8	4.9 m - 11 m	28.7	8.98
(2010 HW20)	2012-Apr-19	0.1549	60.3	16 m - 36 m	26.1	6.74
(2008 AF3)	2012-Apr-19	0.1957	76.2	14 m - 31 m	26.4	1.72
141018 (2001 WC47)	2012-Apr-19	0.1013	39.4	510 m - 1.1 km	18.6	3.80
(2011 UP63)	2012-Apr-20	0.1283	49.9	48 m - 110 m	23.7	5.83
(2010 WR7)	2012-Apr-21	0.1834	71.4	52 m - 120 m	23.5	6.52
(2009 HU44)	2012-Apr-21	0.0872	33.9	84 m - 190 m	22.5	21.17
(2011 UD21)	2012-Apr-22	0.0547	21.3	5.3 m - 12 m	28.5	1.46
(2008 TZ3)	2012-Apr-23	0.1673	65.1	230 m - 510 m	20.3	13.31
(2003 WH166)	2012-Apr-23	0.0509	19.8	110 m - 250 m	21.9	13.49
(2006 VQ13)	2012-Apr-24	0.1395	54.3	260 m - 580 m	20.0	15.47
(2012 AP10)	2012-Apr-24	0.1481	57.6	14 m - 31 m	26.4	2.08
(2009 UW18)	2012-Apr-28	0.1355	52.7	320 m - 720 m	19.6	14.22
(2011 WV134)	2012-Apr-28	0.0992	38.6	1.1 km - 2.4 km	17.0	12.12
(2008 UC202)	2012-Apr-29	0.0263	10.2	6.0 m - 13 m	28.2	4.55
(2009 TP)	2012-Apr-30	0.1177	45.8	52 m - 120 m	23.5	3.13
(2004 MD)	2012-Apr-30	0.1679	65.3	250 m - 560 m	20.1	10.24
(1992 JD)	2012-May-02	0.0243	9.5	26 m - 59 m	25.0	6.98
(2001 SZ269)	2012-May-03	0.0713	27.8	380 m - 860 m	19.2	18.07
(2010 KX7)	2012-May-04	0.0390	15.2	110 m - 260 m	21.8	11.42
(2011 JN5)	2012-May-05	0.1107	43.1	25 m - 55 m	25.2	17.81
(1998 HE3)	2012-May-10	0.0319	12.4	120 m - 270 m	21.7	11.93
(2005 SQ9)	2012-May-11	0.0852	33.2	68 m - 150 m	22.9	10.21
141432 (2002 CQ11)	2012-May-12	0.1022	39.8	280 m - 630 m	19.9	16.26
(2008 CB6)	2012-May-13	0.1103	42.9	10 m - 23 m	27.1	10.85

* Diameter estimates based on the object's absolute magnitude.

NASA NEO

[Windflier]

Do you know how many Chinese asteroid miners that would put out of work?

:-)