Talk:RX J1856.5−3754

Contradictory
The article mentions that it is commonly held that this is unlikely to be a quark star as there is lack of supporting evidence. Yet 80% of the articles content, claims that there is.

Eg. Chandra observations of RX J1856.5-3754 and the pulsar in 3C58 suggest that the matter in these collapsed stars is even denser than nuclear matter, the most dense matter found on Earth. This raises the possibility that these stars are composed of free quarks or crystals of sub-nuclear particles, rather than neutrons.

Is this supporting evidence or isn't it? At minimum need to say why these observations are considered bad/unlikely rather then presenting them as likely possibility. —Preceding unsigned comment added by 121.45.59.166 (talk) 04:59, 14 June 2010 (UTC)

Unlikely to be a quark star
I added a ref from ADSABS which suggests:

"We discuss recent Chandra and XMM-Newton observations of the bright isolated neutron star RXJ1856.5-3754 and suggest that the absence of any line features is due to effects of a high magnetic field strength (~1013G). Using different models for the temperature distribution across the neutron star surface and assuming blackbody emission to fit the optical and X-ray spectrum, we derive a conservative lower limit of the "apparent" neutron star radius of 16.5 km × (d/117 pc). This corresponds to the radius for the "true" (de-redshifted) radius of 14 km for a 1.4 Msolar neutron star, indicating a stiff equation of state at high densities. A comparison of the result with mass-radius diagrams shows that quark stars and neutron stars with quark matter cores can be ruled out with high confidence."

The last sentence is the key. I understand that a "soft" EOS is required for a quark star. Puzl bustr (talk) 17:14, 31 October 2009 (UTC)


 * I have corrected the text respectively, and provided additional references. It is certainly NOT a quark star. Potekhin (talk) 08:24, 14 January 2011 (UTC)

Neutrality?
Portions of this article read more like a press release than a encyclopedic discussion. The line "One exciting possibility ..." seems to stand out the most. 68.84.64.106 (talk) 03:10, 29 September 2010 (UTC)

Starbox
The starbox template is inserting R_sun as units for the radius, so that we end up with "km R_sun." I took a quick look at the template, but did not any easy way to fix this. --Amble (talk) 06:33, 27 August 2012 (UTC)

Diameter
Is the diameter 17km or less (4km) as in the box ? Perhaps the box should be modified. I'm not sure enough about those data to do it myself.--Io Herodotus (talk) 12:08, 16 February 2015 (UTC)

Meaning of young?
"RX J1856 is one of the Magnificent Seven, a group of young neutron star........"

IGR J11014-6103 is about 10 - 20,000 years old in present images. Thats young. — Preceding unsigned comment added by 173.56.18.42 (talk) 18:19, 7 February 2016 (UTC)

Vacuum birefringence section largely incorrect
The author of this section appears to have misunderstood reference. Vacuum birefringence is a well-known consequence of QED and does not violate Lorentz symmetry. The apparent violation of Lorentz symmetry is explained by the presence of a strong magnetic field. At the end of the original research article, they state "The [Polarization degree] that we derive is large enough to support the presence of vacuum birefringence, as predicted by QED." . I have removed this section. — Preceding unsigned comment added by ETHJILA (talk • contribs) 03:54, 17 August 2017 (UTC)

Size of RX J1856.5−3754
The text indicates that the size of this neutron star is "about 14 km" diameter, yet the box-out at right says "19–41 km" radius (which would be 38–82 km diameter). The box-out looks way out of the range of possible neutron star sizes to my layman's eye, and more like a white dwarf.NelC (talk) 16:43, 8 April 2020 (UTC)

Video
The zooming video is neat, but at the end it's not really clear which star it's supposed to be. 2600:8800:7000:33:0:0:0:144 (talk) 04:37, 24 April 2021 (UTC)