Recent Posts

Pages: 1 ... 3 4 [5] 6 7 ... 10

Universe Sandbox Â² | Discussion / Brown Giants

« Last post by Gregory on December 03, 2023, 07:29:01 PM »

I was experimenting on a sim of the largest known stars, and when some of them collided, they lost enough mass to the point of having the properties of brown dwarves, but still maintaining giant star sizes.
This most likely opened up a hypothetical concept of the existence of brown giants.

I even realized not only can you make one with supernovae or hypernovae, but also by simply reducing the mass to less than that of true stellar mass while keeping its size large.

If we ever found any, it would most likely be a history-changing discovery changing the way we study stars and their formation.

So far, we've only seen this happen on US2, so such a discovery of these in reality would be a game changer.

Universe Sandbox Â² | Updates / UY Scuti should be fixed & Stephenson 2-18 to be removed until further notice

« Last post by Gregory on November 19, 2023, 01:22:46 PM »

Recently, UY Scuti had an analysis update by GAIA EDR3 using noiseless data.
It was found to be at a distance of roughly 1.8 kiloparsecs (~5,870.81 ly) from the Sun, which's much closer than previously thought, though no radius value regarding that was published.
https://iopscience.iop.org/article/10.3847/1538-3881/abd806

Furthermore, Stephenson 2-18 has been given various results from different methods about its luminosity, with the first method calculating only 90,000 x the Sun's luminosity, while another method calculated it to be nearly 440,000 x the Sun's luminosity, leading to the 2,150 solar radius estimate, and another method calculated it to be 630,000 x the Sun's luminosity, which leads to another different radius value.
https://academic.oup.com/pasj/article/62/2/391/1459840?login=false
https://iopscience.iop.org/article/10.1088/0004-637X/760/1/65
https://iopscience.iop.org/article/10.3847/1538-3881/abab15

It's the same problem with NML Cygni as different measurements have given it highly various results of its luminosity calculations, including a value of 200,000, 270,000, and a parallax measurement from GAIA DR2 of 1.5259 +/- 0.5677 mas (milliarcseconds), all corresponding to radii values between 1,183, 1,640, and 2,770 solar radii.
https://www.aanda.org/articles/aa/pdf/2012/08/aa19587-12.pdf
https://ui.adsabs.harvard.edu/abs/2010A%26A...523A..18D/abstract
https://iopscience.iop.org/article/10.3847/1538-4357/ab0e83

Yet HV 888 also has too much uncertainty in its calculations.
https://iopscience.iop.org/article/10.3847/1538-4357/ac6dcf
https://arxiv.org/abs/astro-ph/0504379
https://iopscience.iop.org/article/10.3847/1538-4357/aca665
With radius estimates as much as 762, 1,353, 1,374, 1,584, and 1,765 solar radii, the variations in the estimates is chaotic.

They should be replaced with Westerlund 1-26 and WOH G64 in an update, as those stars (despite WOH G64 being farther away) have been calculated by measurements with apparently better certainty and reliability until better measurements give us more-reliable calculations of UY Scuti and Stephenson 2-18.

Westerlund 1-26 and WOH G64 to be added to the bodies folder until future updates in US2.