Which type of star is responsible for why H II regions glow?
Which type of star is responsible for why H II regions glow?
The short-lived blue stars created in these regions emit copious amounts of ultraviolet light that ionize the surrounding gas.
Why do H II regions glow?
The Rosette is a prominent star formation region, glowing due to ultraviolet light from the young, hot, blue stars whose winds also cleared the central hole. Image Credit. In this case, the HII clouds (blue) are surrounding hot, young stars (yellow).
What is an emission nebula also known as an H II region?
H II region, also called diffuse nebula or emission nebula, interstellar matter consisting of ionized hydrogen atoms. The energy that is responsible for ionizing and heating the hydrogen in an emission nebula comes from a central star that has a surface temperature in excess of 20,000 K.
Where are emission nebulae H II regions found?
Some of the most beautiful extended objects that we can see are HII regions, or diffuse or emission nebulae. So-named because they contain mostly ionized hydrogen (H+ or HII), HII regions are found throughout the interstellar medium in the Galaxy and in other galaxies.
How do we observe HII regions?
Once you have a list of objects you think might be HII regions, use the Navigation Tool or the Object Explorer to see which ones really are. Look also at their spectra to see which ones have the hydrogen emission lines characteristic of HII regions. HII regions are generally found in the arms of spiral galaxies.
Where are emission nebulae H II regions found quizlet?
Emission Nebulae (HII regions): Most of the interstellar gas is in a neutral state but in some regions astronomers find what are called HII regions these regions are produced when a hot star (10,000 K or hotter) is located in a gas cloud.
What Colour are HII regions and why?
In SDSS images, HII regions appear light blue instead of pink.) Transitions from n = 4 to n = 2 and n = 5 to n = 2 levels also produce lines in the visible spectrum. HII regions also give off a lot of ultraviolet light due to photons from the transitions where electrons jump into the n = 1 energy level.
Do stars form in emission nebulae?
Most emission nebulae are the sites of recent star formation, where hot, energetic radiation streaming from the newborn stars sculpts a nebula’s bright and dark clouds into intriguing (and sometimes mystifying) shapes.
Why are emission nebulae popular locations for star formation?
These nebulae are strong indicators of current star formation since the O and B stars that ionise the gas live for only a very short time and were most likely born within the cloud they are now irradiating. One of the most famous emission nebulae is the Orion Nebula (M42) located just below Orion’s belt.
How do I find HII regions?
Look also at their spectra to see which ones have the hydrogen emission lines characteristic of HII regions. HII regions are generally found in the arms of spiral galaxies. For nearby galaxies that appear large, spiral arms are easy to identify.
Where are HII regions emission nebulae found quizlet?
These molecules are found in great interstellar clouds that are rich in dust. These great masses of material are called molecular clouds. Much of this material is concentrated in the spiral arms of the Galaxy. HII is a region of interstellar hydrogen that is ionized.
What is the space between stars called?
In astronomy, the interstellar medium (ISM) is the matter and radiation that exist in the space between the star systems in a galaxy. This matter includes gas in ionic, atomic, and molecular form, as well as dust and cosmic rays. It fills interstellar space and blends smoothly into the surrounding intergalactic space.
How do Stars travel through the HII region?
The winds and UV radiation emitted by the massive stars not only irradiate the gas in the HII region, but also work to carve out a cavity in the surrounding molecular cloud. The hot, ionised gas of the HII region expands into this cavity travelling faster than the speed of sound.
What is an HII region?
In our Galaxy, HII regions follow a distribution pattern similar to that of the molecular clouds from which stars are formed, and are similarly concentrated in the spiral arms of other galaxies. They are also found in association with newly formed stars throughout irregular galaxies making them highly visible tracers of active star formation.
What is the composition of the H II region?
Chemically, H II regions consist of about 90% hydrogen. The strongest hydrogen emission line, the H-alpha line at 656.3 nm, gives H II regions their characteristic red colour. (This emission line comes from excited un-ionized hydrogen.) Most of the rest of an H II region consists of helium, with trace amounts of heavier elements.
What are HII stars made of?
They are composed primarily of hydrogen, hence the name ( astronomers use the term HII to refer to ionised hydrogen, HI for neutral hydrogen ), and have temperatures of around 10,000 Kelvin. They can extend over several hundred light years or be so compact that they do not even stretch 1 light year across.
