Recent content by Maria76

Hi, Here is a weird question (I hope you don't mind). Let's say we have an alphabet with only 4 letters (A, B, C, D)? How many combinations of give us palindromes (i.e. they read the same way backwards and forwards)? I count 36 possible combinations - AAAA BAAB CAAC DAAD EAAE FAAF ABBA...

Hi, I'm trying to wrap my head around the different kinds of trajectories. Firstly, what kind of objects have hyperbolic trajectories? And how do we differentiate between a parabolic trajectory and a hyperbolic one? Thank you for any help. Maria

Hi Nan, I was also looking forward to the 2004 Venus transit, but unfortunately the weather conditions conspired against me :( In my question, I was really wanting to know how we can predict the lunar occultations of Regulus. I don't believe these events are rare (although I could be wrong...

Hi, I saw the occultation of the star Regulus by the Moon 2 years ago (June 2007). I wonder how often this event happens, and why? Thank you for your time. Maria

Let's say we have a star of 0.7 solar masses on the main sequence. Can somebody describe what happens to it when it comes off the main sequence? Thanks Maria

I found the following paper, which proposes that anti-stars can be distinguished from matter stars from the "polarization properties of their electromagnetic emissions" (see section 4.2). http://arxiv.org/PS_cache/astro-ph/pdf/0405/0405417v3.pdf

I heard about that. In an x-ray binary in which a black hole is believed to be the compact object, it has been suggested that the strength of an ultrasoft x-ray component is directly related to the black hole's spin. Check out section 8.2 of the following...

A photon is its own antiparticle, so it's logical to think that a star and an antistar would be observationally indistinguishable. But I read somewhere (can't remember where) that antistars may be distinguishable from anti-stars by the polarization of their photons. So the polarization of...

Hi, I was looking at information about the Horsehead nebula on wikipedia http://en.wikipedia.org/wiki/Horsehead_nebula and it says that its apparent dimensions are 8x6 arcmins. I'm not sure how to find the actual dimensions, say in light-years. Here's how I believe it should be, but...

Hi, When the core of a star shrinks during its evolution, does it always lead to the expansion of the star? If not, why? What cases would cause it to expand? Thanks in advance, Maria

Hi again, Just out of curiosity, given that the altitude of a star is its height above the horizon, how would I be able to determine the altitude of a star without a telescope? I'd probably need something like a sextant or an astrolabe? Or is there a more simple way? Thanks again. Maria

Hi Marty & Tiny-Tim. Let me see if I have this right. As Tiny-Tim says, declination of a star is the amount north or south of the celestial equator, and so is the same for all positions on the Earth. In that case, if I am standing at the Tropic of Cancer, the declination of the Sun is 0...

Hi Tiny-Tim, Thanks for your answer. Now I'm having a little trouble visualizing the situation ... If the Sun is overhead at midday at an equinox at the equator, it means that the solar altitude is 90 degrees. At the Tropics, which are at latitude 23.5 degrees, the solar altitude would be at...

Hi, This might sound like a simple question, but it's not for me. I'm standing at the Tropic of Cancer - what would be the declination of the Sun on the Spring equinox. I believe it should be zero degrees, but my brother says it's 23.5 degrees. Can anybody shed light? Thanks in advance...