Why do O stars have weak hydrogen absorption lines?
If the star is too hot or too cold, the hydrogen lines will be weak. If the temperature is too low, most of the hydrogen atoms will have their electrons starting out from the ground state. If the hydrogen atoms are heated to high temperatures, the atomic collisions can ionize the hydrogen atoms.
Why do stars of spectral types O and B show few absorption lines?
Why do stars of spectral types O and B show few absorption lines? Many atoms in these stars are ionized-have lost electrons-so can‘t absorb. Much of their absorption is in the ultraviolet. Two stars that look very different must be made of different kinds of elements.
Why do K and M type stars have weaker hydrogen absorption lines than a type stars?
So, the absorption lines become very weak because very few of the hydrogen atoms are participating. Hydrogen is not excited in cooler “K” and “M” stars, (the photons do not have enough energy to raise the electron to higher energy orbits).
Which spectral type has the strongest hydrogen absorption lines?
Hydrogen lines are strongest in A stars with atmospheric temperatures of about 10,000 K. Ionized metals provide the most conspicuous lines in stars with temperatures from 6000 to 7500 K (spectral type F). In the coolest M stars (below 3500 K), absorption bands of titanium oxide and other molecules are very strong.
Why do the coolest stars show weak Balmer lines?
The Balmer thermometer works because the Balmer lines are produced only by hydrogen atoms whose electrons are in the second energy level. If the surface of a star is as cool as the surface of the Sun (about 5800 K) or cooler, most of the atoms are in the ground state. So, cool stars have very weak Balmer lines.
Which color star is hottest?
Stars have different colors, which are indicators of temperature. The hottest stars tend to appear blue or blue–white, whereas the coolest stars are red.
What are the 7 spectral classes of stars?
Stars are classified by their spectra (the elements that they absorb) and their temperature. There are seven main types of stars. In order of decreasing temperature, O, B, A, F, G, K, and M.
What is our sun’s full spectral classification?
The full spectral class for the Sun is then G2V, indicating a main-sequence star with a surface temperature around 5,800 K.
Why do stars have dark lines in their spectra?
3. 9) Stars have dark spectral lines because gases in the star’s atmosphere absorb specific wavelengths (colors) of light from the full spectrum of light coming from it’s surface. The balance between these two processes determines the star’s size.
What color is the coolest star?
Red stars are the coolest. Yellow stars are hotter than red stars. White stars are hotter than red and yellow. Blue stars are the hottest stars of all.
What spectral class of stars is the coolest?
The spectral sequence is also a colour sequence: the O- and B-type stars are intrinsically the bluest and hottest; the M-, R-, N-, and S-type stars are the reddest and coolest.
Which star is the brightest white dwarf?
White dwarfs may be white and hot, but their small size means that nearly all are faint. But lucky for us, not too faint. The brightest and most familiar is Sirius B at magnitude +8.5. Even at its maximum separation of 11.5″ in 2025, this dwarf’s a tough nut because of the overwhelming glare of Sirius itself.
What is the hottest star type?
O stars are the hottest, with temperatures from about 20,000K up to more than 100,000K. These stars have few absorption lines, generally due to helium. These stars burn out in a few million years. B stars have temperatures between about 10,000 and 20,000K.
What is the distance to a star that has a parallax angle of 0.5 arc seconds?
What is the distance to a star that has a parallax angle of 0.5 arc seconds? Two parsecs.
Which star is the coldest?
In general, a star’s temperature determines its color, from red to blue-white. Spectral types are named with a letter. The seven main types are M, K, G, F, A, B and O. M stars are the coldest stars and O stars are the hottest.