<p>The BBC's <a href="https://www.bbc.com/news/science-environment-51707927" rel="nofollow noreferrer">Huge 'space snowman' is two merging stars</a> says</p>
<blockquote>
<p><strong>Researchers have discovered a huge snowman-shaped star</strong> with an atmospheric composition never seen before.</p>
<p>It is more massive than our Sun but only two-thirds the Earth's diameter.</p>
<p>The object is thought to have resulted from the merger of two so-called white dwarf stars that often explode as powerful supernovas.</p>
<p>Dr Mark Hollands, of Warwick University, said the team's discovery could help scientists better understand how this process occurs.</p>
</blockquote>
<p>and later</p>
<blockquote>
<p>But this star, named WDJ0551+4135, has an atmosphere unusually rich in carbon. Dr Hollands said that initially these observations &quot;didn't make any sense. The only way you can explain it is if it was formed through a merger of two white dwarfs&quot;.</p>
</blockquote>
<p>I assume this means that it is suspected of being a <a href="https://en.wikipedia.org/wiki/Contact_binary" rel="nofollow noreferrer">contact binary</a></p>
<p><strong>Question:</strong> Is WDJ0551+4135 thought to be a contact binary only based on chemistry and evolution arguments? Wouldn't a light curve of this object alone be enough, and wouldn't the period be extremely short making this somewhat easier to do?</p>
<p><strong>update:</strong> C|NET's <a href="https://www.cnet.com/news/astronomers-find-a-bizarre-dying-star-that-didnt-make-any-sense/" rel="nofollow noreferrer">Astronomers find a bizarre, dying star that 'didn't make any sense'</a> suggests that the argument is indeed based on chemistry, and that asteroseismology may be required to back it up. It also links to Nature Astronomy <a href="https://www.nature.com/articles/s41550-020-1028-0" rel="nofollow noreferrer">An ultra-massive white dwarf with a mixed hydrogen–carbon atmosphere as a likely merger remnant</a>.</p>

CC BY-SA 4.0
2020-03-02T23:40:11.593Z
The paper only talks about it being the result of a merger of close binary system based on chemical abundances from spectra. No mention of the contact binary state or "snowman shape" being current
astrosnapper
CC BY-SA 4.0
2020-03-02T23:54:26.297Z
@astrosnapper I was afraid of that. I wonder if this is like the BBC's reference to [crashing large hadrons together](https://physics.stackexchange.com/q/454554/83380)? Maybe the artwork in this article would work there as well? ;-)
uhoh
CC BY-SA 4.0
2020-03-03T00:03:03.533Z
I fear this may be correct. Contact binary artwork presumably looks much "cooler" than a single white dwarf just sitting there...
astrosnapper
CC BY-SA 4.0
2020-03-03T00:14:57.600Z
@astrosnapper I've just asked [What is considered "contact" for contact binary stars, and very roughly how long can they stay that way before merging?](https://astronomy.stackexchange.com/q/35393/7982)
uhoh
CC BY-SA 4.0
2020-03-04T00:37:56.117Z
When hugely massive objects approach, they nullify each other's gravity, beginning at their most proximate points. On white dwarfs and neutron stars, this means that their gravity bound composition is nullified. It must be an exciting time. I wonder if it's possible to achieve some kind of stability instead of complete merger.
Howard Miller
CC BY-SA 4.0
2020-03-04T00:44:29.537Z
@HowardMiller the closer they get, the faster they spin.
uhoh
<binary-star><contact-binaries>
Why do they think that WDJ0551+4135 is "snowman shaped" i.e. a contact binary?
uhoh
# Why do they think that WDJ0551+4135 is "snowman shaped" i.e. a contact binary?

(Asked by: username_0 on 2020-03-02)

The BBC's [Huge 'space snowman' is two merging stars](https://www.bbc.com/news/science-environment-51707927) says

> **Researchers have discovered a huge snowman-shaped star** with an atmospheric composition never seen before.
>
> It is more massive than our Sun but only two-thirds the Earth's diameter.
>
> The object is thought to have resulted from the merger of two so-called white dwarf stars that often explode as powerful supernovas.
>
> Dr Mark Hollands, of Warwick University, said the team's discovery could help scientists better understand how this process occurs.

and later

> But this star, named WDJ0551+4135, has an atmosphere unusually rich in carbon. Dr Hollands said that initially these observations "didn't make any sense. The only way you can explain it is if it was formed through a merger of two white dwarfs".

I assume this means that it is suspected of being a [contact binary](https://en.wikipedia.org/wiki/Contact_binary)

**Question:** Is WDJ0551+4135 thought to be a contact binary only based on chemistry and evolution arguments? Wouldn't a light curve of this object alone be enough, and wouldn't the period be extremely short making this somewhat easier to do?

**update:** C|NET's [Astronomers find a bizarre, dying star that 'didn't make any sense'](https://www.cnet.com/news/astronomers-find-a-bizarre-dying-star-that-didnt-make-any-sense/) suggests that the argument is indeed based on chemistry, and that asteroseismology may be required to back it up. It also links to Nature Astronomy [An ultra-massive white dwarf with a mixed hydrogen–carbon atmosphere as a likely merger remnant](https://www.nature.com/articles/s41550-020-1028-0).

**Tags:** binary-star, contact-binaries

> **Comments:**
> **username_1**: The paper only talks about it being the result of a merger of close binary system based on chemical abundances from spectra. No mention of the contact binary state or "snowman shape" being current  
> **username_0**: @username_1 I was afraid of that. I wonder if this is like the BBC's reference to [crashing large hadrons together](https://physics.stackexchange.com/q/454554/83380)? Maybe the artwork in this article would work there as well? ;-)  
> **username_1**: I fear this may be correct. Contact binary artwork presumably looks much "cooler" than a single white dwarf just sitting there...  
> **username_0**: @username_1 I've just asked [What is considered "contact" for contact binary stars, and very roughly how long can they stay that way before merging?](https://astronomy.stackexchange.com/q/35393/7982)  
> **username_2**: When hugely massive objects approach, they nullify each other's gravity, beginning at their most proximate points. On white dwarfs and neutron stars, this means that their gravity bound composition is nullified. It must be an exciting time. I wonder if it's possible to achieve some kind of stability instead of complete merger.  
> **username_0**: @HowardMiller the closer they get, the faster they spin.  

---

## 0 answers

