Questions about white dwarf Sirius B

[remcot]

Hello everyone ,i have some questions about white dwarf Sirius B.<br /><br />1 Sirius B is a blue dwarf ,not a white. Is that true?<br /><br />2 What happens with Earth and life when Sirius B is (hyphotetical) at the same distance away from us as the Moon (300.000) kilometers? Will it be icy cold or warm then?<br /><br />3 Will it be (theoretical) possible to get to the surface of Sirius B in a protected spaceship without danger? A friend of mine thinks that it can easely possible. <br /><br />Can somebody help me with this questions?<br /><br />Thank you.

 

[Saiph]

Sirius B is a white dwarf, though "white" merely means lots of light in all colors. The peak visible color is blue/purple however (meaning more of these wavelengths are emitted than the others).<br /><br />A "blue dwarf" however, is a class O mainsequence star. Sirius B isn't main sequence anymore (it's a stellar corpse) and Sirius A is a class A star, a cooler, smaller type of star than a type O.<br /><br />If Sirius B was that close....we'd have problems. Look up the temperature of a white dwarf, and use the equation for luminance of L=R^2*t^4<br /><br />To make comparison easy, divide the sun's radius by the white dwarfs, and the sun's temperature by the white dwarfs, then plug them into the equation. Your answer will be in comparison to the sun. So if you get L=2, we have an object twice as luminous as the sun.<br /><br /><br />As for landing...consider the conditions of matter upon the surface. The intense heat means no molecules will survive, they'll be shredded...and if a molecule can't stand the heat, no other material will either (so everything is turned into a gas of atoms). The intense gravity will also really mess with things, and crush anything that could possibly survive the surface. <div class="Discussion_UserSignature"> <p align="center"><font color="#c0c0c0"><br /></font></p><p align="center"><font color="#999999"><em><font size="1">--------</font></em></font><font color="#999999"><em><font size="1">--------</font></em></font><font color="#999999"><em><font size="1">----</font></em></font><font color="#666699">SaiphMOD@gmail.com </font><font color="#999999"><em><font size="1">-------------------</font></em></font></p><p><font color="#999999"><em><font size="1">"This is my Timey Wimey Detector.  Goes "bing" when there's stuff.  It also fries eggs at 30 paces, wether you want it to or not actually.  I've learned to stay away from hens: It's not pretty when they blow" -- </font></em></font><font size="1" color="#999999">The Tenth Doctor, "Blink"</font></p> </div>

 

[remcot]

I forgot 1 question,<br /><br />How big is Sirius B?

 

[djtt]

i gathered about 1.3-1.5 times jupiter's diameter

 

[doubletruncation]

It's smaller than that. Its radius is about ~6000 km which is roughly the size of the Earth. See for example: http://xxx.lanl.gov/abs/astro-ph/0507523 where they state a mass of 1.0 solar masses (that comes from watching it's position on the sky change as it orbits the Sirius A/B barycenter and from knowing its distance via parallax) and a spectroscopically determined surface gravity of log(g) = 8.528 (units are log10 of cm/s^2). From those two numbers you can calculate the radius. <br /><br />The radius can also be had from measuring the temperature and the flux using the spectrum and then using the blackbody radiation law and the parallax distance. A last, neat way, of getting the radius comes from measuring the gravitational redshift of the spectral absorption lines which is propotional to mass/radius. All these various methods yield consistent results, and it seems that the radius is known to about 1% precision. <div class="Discussion_UserSignature"> </div>

 

[nexium]

Sirius B would appear a bit more than twice the diameter of the moon, from moon distance. Because the surface temperature is hotter than the Sun, most of the photons are ultraviolet, so sunburn would be a big problem even if Sirius were a million kilometers away, which would be about the correct distance for liquid water on most Earth's surface. Neil

 

[alokmohan]

But it was the first white dwarf to studied by Eddington.Eddington wondered how seriusB can be 61000 times heavier than platinum?Eddington did not know the correct answer.Fowler broght degeneracy concept.And we start research and land upto black hole.

 

[search]

LINK<br /><br />Sirius B has a diameter of 7,500 miles (12,000 kilometres), less than the size of Earth, but is much denser. Its powerful gravitational field is 350,000 times greater than Earth's, meaning that a 150-pound (68 kilogram) person would weigh 50 million pounds standing on its surface.<br /><br />Sirius B has a mass that is 98 percent that of our own Sun.<br /><br />The Hubble observations have also refined the measurement of Sirius B's surface temperature to be 44,900 degrees Fahrenheit, or 25,200 degrees Kelvin.<br /><br />Sirius A and Sirius B (tiny spot on lower left)

 

[alokmohan]

It is 61000 times heavier than platinum.Arthur Eddington was first to did not knew degeneration of matter none knew it .S.Chandrasekhar studied white dwarfs in light of electron degeneration and was to first to propose what we now know as black hole.matter collapsing on itself to get black hole(he did not use the term.)Chandra found out that no white dwarf can have more than 1.4 times mass of sun.