Hellagrams are great for terrestrial planets
There is an internet petition afoot to make "hella" the official SI prefix for 1027. In one sense, this seems silly- a hellameter is several times the size of the observable universe. But there is at least one application for which this suffix would be useful.
Currently, one of the most exciting areas in all of science is the discovery of smallish planets orbiting other stars. By smallish, I mean smaller than Neptune. But while there is a factor-of-fourteen mass gap in our own solar system between Uranus and Earth, in the rest of the galaxy this gap does not exist, and planets occupy most of that mass range.
Traditionally, most planets have had their mass compared to Jupiter. While this is fine for gas giants, there are a couple of problems when applying it to smaller planets. Firstly, you end up with lots of zeros in front of your number: 0.003 is a bit awkward. Secondly, nobody really has a good feel for how massive a planet is.
The hellagram solves both of these problems. Earth is a shade under 6 hellagrams. Neptune is a shade over 100. Jupiter, the big boy of our solar system, is about 1900. If we assume that Mars is just a bit too small to maintain active geologic processes up to the present day, then 1 hellagram becomes a good ballpark lower bound for active planets. It is also close to the detection limit for Kepler, the most sensitive planet hunting program now operating.
The hella- project is being run out of one of the University of California campuses. And the UC system is a world leader in exoplanetary detection and characterization. So if they get on board the hellabandwagon, the hellagram has a good shot at entering common scientific usage. And that would be hella cool.
The mass of known sub-Neptune planets, in various units:
| name | Hellagrams | Me | Mj |
|---|---|---|---|
| PSR 1257+12b | 0.133 | 0.02 | 0.00007 |
| Mercury | 0.330 | 0.06 | 0.00017 |
| Mars | 0.640 | 0.11 | 0.00034 |
| Venus | 4.87 | 0.82 | 0.00256 |
| Earth | 5.97 | 1.00 | 0.00314 |
| GI 581 e | 11.6 | 1.94 | 0.00610 |
| MOA2007-BLG-192-L-b | 19.0 | 3.18 | 0.0100 |
| PSR 1257+12d | 22.8 | 3.82 | 0.0120 |
| PSR 1257+12c | 24.7 | 4.14 | 0.0130 |
| HD156668b | 24.9 | 4.17 | 0.0131 |
| HD40307b | 25.1 | 4.20 | 0.0132 |
| CoRoT-7b | 28.7 | 4.80 | 0.0151 |
| 61 Vir b | 30.4 | 5.09 | 0.0160 |
| Gi 581 c | 32.0 | 5.36 | 0.0169 |
| HD215497b | 32.3 | 5.41 | 0.0170 |
| OGLE-05-390L-b | 32.3 | 5.41 | 0.0170 |
| GJ 1214b | 34.0 | 5.69 | 0.0179 |
| GJ 667C b | 34.4 | 5.76 | 0.0181 |
| GJ 433 b | 36.1 | 6.04 | 0.0190 |
| Giliese 876 d | 38.0 | 6.36 | 0.0200 |
| HD 40307 c | 41.0 | 6.87 | 0.0216 |
| Gl 581 d | 42.4 | 7.10 | 0.0223 |
| HD 181443 b | 45.2 | 7.57 | 0.0238 |
| HD 1461 b | 45.4 | 7.60 | 0.0239 |
| 55 Cnc e | 45.6 | 7.63 | 0.0240 |
| CoRoT-7 c | 50.1 | 8.40 | 0.0264 |
| HD 285968 b | 50.3 | 8.43 | 0.0265 |
| HD 40307 d | 54.7 | 9.16 | 0.0288 |
| HD 7924 b | 55.1 | 9.22 | 0.0290 |
| HD 69830 b | 62.7 | 10.5 | 0.0330 |
| HD 160691 c | 63.1 | 10.6 | 0.0332 |
| GJ 674 b | 70.3 | 11.8 | 0.0370 |
| HD 69830 c | 72.2 | 12.1 | 0.0380 |
| OGLE-05-169L b | 76.0 | 12.7 | 0.0400 |
| HD 4308 b | 76.9 | 12.9 | 0.0405 |
| BD-082823 b | 85.5 | 14.3 | 0.0450 |
| HD 125595 b | 85.5 | 14.3 | 0.0450 |
| Uranus | 86.8 | 14.5 | 0.0457 |
| Gl 581 b | 93.4 | 15.7 | 0.0492 |
| Neptune | 102 | 17.1 | 0.0537 |
2 comments:
Also, a mole is 6.023 x 10^23, so hella would be a good prefix for talking about the number of atoms or atomic mass units (AMU or Dalton) in macroscopic objects. A kilogram is a bit more than half a hella of AMU's.
As nanotechnology advances, we're gaining the ability to make kilograms of atomically precise nanostructures...
Chris
I'm convinced. I signed on.
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