Desmos, 22 bytes

r=\sqrt{\sin 2\theta }

Try it here! Desmos is a graphing tool. This plots the polar equation:

which draws a lemniscate shape.

J, 8 bytes

3 5$' o'

Like Conor's, prints:

 o o 
o o o
 o o 

$ is J's shape operator, so we are creating a 3 x 5 grid, using the fill chacters o. When fill runs out, $ repeats them cyclically by default.

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///, 13 bytes

/z/ o o
/zozz

Try it online! Outputs:

 o o
o o o
 o o

I think this is the smallest valid "lemniscate" allowed by the rules.

Python 2, 21 19 bytes

print"o o\nooo\n"*3

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This prints:

o o
ooo
o o
ooo
o o
ooo

It may not look like a lemnescate but it has two enclosed spaces (marked with x)

o o
ooo
oxo
ooo
oxo
ooo

And every o is connected to at least two other os. Thus despite not looking anything like what it is supposed to this fulfills the bare-minimum requirements.

Mathematica, 3 bytes

∞

I think this answer covers all the criteria

Mathematica, 17 bytes

Graphics@Text@∞

Mathematica - 49 bytes

ParametricPlot[{ReIm[Sin[t+I Sin[t]]]},{t,0,2Pi}]

Jelly,  8  7 bytes

8RKḊs5Y

As a full program prints:

 2 3 
4 5 6
 7 8

Which seems to adhere to the specification.

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How?

8RKḊs5Y - Main link: no arguments
8R      - range of 8 -> [1,2,3,4,5,6,7,8]
  K     - join with spaces -> [1,' ',2,' ',3,' ',4,' ',5,' ',6,' ',7,' ',8]
   Ḋ    - dequeue -> [' ',2,' ',3,' ',4,' ',5,' ',6,' ',7,' ',8]
    s5  - split into chunks of length 5 -> [[' ',2,' ',3,' '],[4,' ',5,' ',6],[' ',7,' ',8]]
      Y - join with newlines -> [' ',2,' ',3,' ',`\n`,4,' ',5,' ',6,'\n',' ',7,' ',8]
        - implicit print

Pyth, 16 bytes

K" o o"K++tKdeKK

Output:

 o o
o o o
 o o

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Pyth, 18 bytes

K"o "+d*K2*3K+d*K2

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Output:

 o o 
o o o 
 o o 

Charcoal, 1 byte

∞

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This just prints the ∞ character.

Charcoal, 7 bytes (ASCII-art version)

ＧＨX²o‖Ｂ

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The first part (ＧＨX²o) prints a hollow polygon of size 2 in the X direction using the o char as border, that results in this:

 o 
o o
 o 

Then I only have to reflect the canvas horizontally (skipping the middle column), to get this:

 o o
o o o
 o o

Link to the verbose version.