Talk:BPM 37093

Lucy in the Sky

Just can't resist... so when singing about this object, one should sing "Lucy in the sky's a diamond." *grins* - UtherSRG 20:44, 19 Jul 2004 (UTC)

Why not a diamond?

The article claims that the density means that the star can't be a diamond. Does anyone have a reference for that claim? Carbon doesn't have very many crystalline structures, after all, and diamond is much denser than graphite... --Andrew 03:36, Apr 13, 2005 (UTC)

Diamond isn't much more dense (3.5 vs. 2.3 g/cm^3). In both cases, ordinary covalent bonds are present. In a white dwarf star, the electrons stack up in degenerate shells (as you'd find in an atom, or somewhat like you'd find in a piece of metal), but the nuclei are free to move around. For a hot white dwarf, this gives you an ordinary gas of carbon nuclei inside the (arguably crystalline) degenerate gas of electrons. For a white dwarf that cools sufficiently, you'd get the nuclei arranging themselves in a close-pack lattice to maintain as large a separation as possible at a given density. Many terrestrial materials have this lattice structure, but diamond isn't one of them (covalently bonded crystals have a small number of neighbours per atom). At the very surface of the star, you might get something resembling terrestrial diamond, but that would only be a very thin crust (high surface gravity means pressure increases quickly enough with depth to give you close-packing and to force electrons to be shared as opposed to stuck in covalent bonds or atoms' core shells). --Christopher Thomas 04:44, 28 June 2006 (UTC)

Every quote from the astronomers refers to it as a diamond; the "five tonne" comment comes only from the BBC reporter. Perhaps that was just a flub on her part, much like CNN's FTL velocity for the Space Shuttle Columbia? —The preceding unsigned comment was added by 69.108.2.235 (talk • contribs) 00:48, 28 April 2005 (UTC)

I'm pretty sure it has a very high density. From what I've heard, white dwarves can have a density about a million times greater than our Sun. After all, it's a whole lot of material collapsed into a very small space in comparison to what it was. -- Northgrove 00:21, 6 January 2007 (UTC)

Density of diamond = 3.51 g/cm³ [1] [2] (or any basic mineralogy text).

Using the data from the Harvard press release and some simple calculations, the density of the carbon in the white dwarf "ash" works out to 2.7x10¹⁴ g/cm³. Now, is 3.51 equal to 270,000,000,000,000? Don't trust my calculations, grab a calculator and do your own (I may have goofed :-).

Astronomers do like to have fun and embellish the language a bit to grab the attention of reporters and the general public. After all - a diamond in the sky is a lot more newsworthy? or attention getting than super dense stellar carbon ash. I note the press release also states that the object "rings like a gigantic gong" - listen and you can hear it now from 50 light years away (and I just thought it was tinnitus).

The BBC reporter didn't "flub" as much as some gullible wikipedians are "flubbing", this is absurd. Vsmith 03:52, 15 May 2005 (UTC)

Er, it does in fact ring; that's how they measured its properties. --Andrew 17:09, May 16, 2005 (UTC)

Diamonds, like most solids, are compressible; given high enough pressure (which is the case here) the denisty will increase. Really the question is about the crystal structure of the carbon - is it bonded like a diamond, like graphite, or like nothing on earth? Because diamond is the densest at atmospheric pressure, it seems likely that a diamond crystal structure is the densest and hence the most stable at these enormous pressures. But I have no idea.

It may be the case that there is a qualitative difference between the degenerate matter making up a white dwarf and ordinary solid diamond, but I don't know enough condensed matter physics to understand. --Andrew 16:40, May 16, 2005 (UTC)

In fact, according to [3], written by Travis Metcalfe, the leader of the original team, the discovery is not that the star is mad of carbon, but that it is crystalline carbon. Now, of the possible crystal structures, diamond is the densest, and this is how the astronomers described it, so I'm inclined to believe that it really is diamond. Not much like ordinary diamond, of course, being incredibly dense, but it is specifically solid crystalline carbon. --Andrew 17:09, May 16, 2005 (UTC)

Even if you assume low temperature, diamond transforms into an structure called BC8 at about 1100 GPa (11 Mbar), and then to cubic at ~3000 GPa, this was discovered by Yin and Cohen in the 80's by doing density functional total energy calculations. Even at such high pressures, the structure (cubic) is far from being close packed. There are some technical difficulties in applying the same method to predict the next transition as pressure is increased. Saying that diamond is the densest form of carbon is for sure not true, there is always some structure with less volume (e.g. close packed) that becomes more stable at larger pressure. Existence of diamond in the interior is impossible (just because the pressure is for sure larger than 11Mbar), existence of the outer layer is also unlikely if it is true that crystallization happens inside-out in a white dwarf (as most articles say). The closest to crystals in white dwarf that I read was an article by Albison and Evans (Astro. and Space Sci. 1987) that considered the possibility of drops of liquid carbon expelled by radiation pressure and forming carbides.

--Alfredo, Dec 2007.  —Preceding unsigned comment added by 99.137.93.112 (talk) 13:55, 8 December 2007 (UTC) 

Remove "Artist's impression"

The image is not an accurate artist's impression. It would never look like that. That image was just meant as a metaphor. TheOtherSiguy 23:55, 30 January 2007 (UTC)

You mean it's not an emerald?

—The preceding unsigned comment was added by 198.133.178.130 (talk • contribs) 19:47, 12 February 2007 (UTC)

Carat Count

Given a mass of 1.1 times that of our sun, it's simple enough to calculate the (hypothetical) total carats: 10^34.

In short scale, that would be ten billion trillion trillion (as edited). In long scale, it would be one thousand billion trillion, so I suppose one could put the exponent in paranthesees to avoid confusion. If anyone feels like it.

JasonD99403 (talk) 03:13, 10 June 2009 (UTC)

Also, i would like to point out that, if anyone starts to get greedy, the speed of light is 669,600,000 mph and it takes 50 lightyears to reach. If that were the case, then it would take sound exactly 54863061797.75280898876404494382 years to reach. and our fastest jets can only beat that by about 10 times. —Preceding unsigned comment added by Gathon9951 (talk • contribs) 17:56, 3 June 2010 (UTC)

Rename article?

I suggest moving this article to V886 Centauri, which follows a wider-spread naming convention. Coments? Metebelis (talk) 22:03, 22 November 2010 (UTC)

You thought I'd never return :) I will rename it shortly. BPM 37093 will still link to the article, of course. Metebelis (talk) 22:51, 7 March 2012 (UTC)

I renamed it back, based on the fact that the subject is much more commonly known by its BPM designation, thus following WP:NCASTRO. StringTheory11 (t • c) 02:26, 18 November 2013 (UTC)

Mass and/or Radius are wrong

https://en.wikipedia.org/wiki/BPM_37093 says BPM 37093 has the following stated mass and radius: Mass of BPM 37093 = 1.1 * 2e30 kg or 2.2e30 kg or 2.2e33 grams and Radius of BPM 37093 = 0.0057 * 6.957e8 meters = 3966 km SO, using these two figures from Wiki, I get 8.42e6 grams per cm cubed density, which seems to be non-physical. I'm assuming Wiki is wrong unless I've erred but I've done this calculation too many times to doubt myself. I hope this issue can be resolved simply and that Wiki will rectify it. RFRules (talk) 22:26, 30 July 2023 (UTC)