What does the spectral class letters mean?
The spectral class of a star is a short code primarily summarizing the ionization state, giving an objective measure of the photosphere's temperature. Most stars are currently classified under the Morgan–Keenan (MK) system using the letters O, B, A, F, G, K, and M, a sequence from the hottest (O type) to the coolest (M type).
Which spectral class does the Sun belong to?
The full spectral class for the Sun is then G2V, indicating a main-sequence star with a surface temperature around 5,800 K. The conventional colour description takes into account only the peak of the stellar spectrum. In actuality, however, stars radiate in all parts of the spectrum.
Which spectral class does a red giant star belong to?
The outer atmosphere is inflated and tenuous, making the radius large and the surface temperature around 5,000 K (4,700 °C; 8,500 °F) or lower. The appearance of the red giant is from yellow-orange to red, including the spectral types K and M, but also class S stars and most carbon stars . Red giants vary in the way by which they generate energy:
What are the spectral classes of Spica?
The classifications group stars into classes as follows:
- Class I: white and blue stars with broad heavy hydrogen lines, such as Vega and Altair. ...
- Class II: yellow stars - hydrogen less strong, but evident metallic lines, such as Arcturus and Capella. ...
- Class III: orange to red stars with complex band spectra, such as Betelgeuse and Antares. ...
What does spectral class depend on?
The spectrum given out by a star depends on the elements in its atmosphere and its temperature. Astronomers have grouped similar stellar spectra into spectral classes. A spectral class is the star's position in a temperature classification scheme based on the appearance of absorption lines in its spectrum.
What is meant by spectral class?
spectral class noun. any of various groups into which stars are classified according to characteristic spectral lines and bands. The most important classification (Harvard classification) has a series of classes O, B, A, F, G, K, M, the series also being a scale of diminishing surface temperature.
How do you determine the spectral class of a star?
2:287:04Classification of Stars: Spectral Analysis and the H-R DiagramYouTubeStart of suggested clipEnd of suggested clipBut this happens to correlate with color and size as well hotter objects like o and B stars are blueMoreBut this happens to correlate with color and size as well hotter objects like o and B stars are blue and cooler objects like K and M stars are. Red also hotter stars tend to be larger.
What does spectral class mean in astronomy?
spectral class, in astronomy, a classification of the stars by their spectrum and luminosity.
What is the most common spectral class?
O stars are the least common and M are the most common found in the main sequence of stars.
How are the three types of spectra defined?
The first spectrum is a continuous collection of wavelengths from the radiation of a heated body. The second is a brightline emission spectrum illustrating the wavelengths a particular gas emits. The third is a darkline absorption spectrum showing the wavelengths that would be aborbed if the gas above were cooled.
What determines a star's type?
They can be categorized according to their mass, and temperature. Stars are also classified by their spectra (the elements that they absorb). Along with their brightness (apparent magnitude), the spectral class of a star can tell astronomers a lot about it. There are seven main types of stars.
What basic property of a star determines its color and thus its spectral type )?
Based on this, what basic property of a star determines its color (and thus its spectral type)? Temperature.
What are the different types of spectral classes?
Harvard spectral classificationClassEffective temperatureMain-sequence mass (solar masses)B10,000–30,000 K2.1–16 M ☉A7,500–10,000 K1.4–2.1 M ☉F6,000–7,500 K1.04–1.4 M ☉G5,200–6,000 K0.8–1.04 M ☉3 more rows
What does a spectral type tells us about the star quizlet?
We use both spectral type and luminosity class to completely classify stars; the spectral type tells us the star's temperature while the luminosity class tells us its radius.
What important property of a star do we learn from its spectral class?
What important property of a star do we learn from its spectral class? The temperature of a star determines at what wavelengths its atmosphere absorbs photons.
What does OH a fine girl kiss me mean?
Every student in introductory astronomy learns the mnemonic “Oh Be a Fine Girl/Guy, Kiss Me”, which is a way to remember the spectral classification of stars. Here's how it works: the color of a star is determined by its temperature, as I outlined previously.
What does the spectral class mean in HR diagram?
The Hertzsprung-Russell (HR) diagram is a useful tool that plots stars' luminosities against spectral classes. Spectral class indicates the relative abundance of the different elements in stars and correlates with temperature, so O and B stars are hotter than K and M stars.
What are the different types of spectral classes?
Harvard spectral classificationClassEffective temperatureMain-sequence mass (solar masses)B10,000–30,000 K2.1–16 M ☉A7,500–10,000 K1.4–2.1 M ☉F6,000–7,500 K1.04–1.4 M ☉G5,200–6,000 K0.8–1.04 M ☉3 more rows
What are the 7 spectral types?
The 7 Main Spectral Types of Stars:O (Blue) (10 Lacerta)B (Blue) (Rigel)A (Blue) (Sirius)F (Blue/White) (Procyon)G (White/Yellow) (Sun)K (Orange/Red) (Arcturus)M (Red) (Betelgeuse)
What spectral class is our Sun?
class G starThe Sun is a class G star; these are yellow, with surface temperatures of 5,000–6,000 K. Class K stars are yellow to orange, at about 3,500–5,000 K, and M stars are red, at about 3,000 K, with titanium oxide prominent in their spectra.
How many subdivisions are there in spectral class?
The basic system of a letter to denote spectral class is further refined by adding a number from 0 to 9 following it. Each spectral class is thus broken down into ten subdivisions so that, for example, an F2 star is hotter than an F7 star.
When was the spectral classification system adopted?
The system now used was adopted in 1910 following detailed and extensive work by Annie Cannon and her team at Harvard Observatory. It has been refined since then but in essence is still the same. To see how this spectral classification scheme works study the sequence of spectra shown below.
What are the lines in the 0-class spectrum?
If you study the spectra above you will notice some trends. The 0-class spectrum has relatively weak lines but lines for ionised He + are present. The B, A and F stars have a similar pattern of lines that are strongest in the A star. These are the H Balmer series for neutral hydrogen. F and G stars have lines corresponding to ionised Ca +. The K and M stars have many more lines visible but the Balmer series is very weak. These lines correspond to Fe, other neutral metals and molecules. TiO lines are visible in the spectrum of M stars.
Why are there no lines in the spectrum of stars?
In most stars the temperature is too cool for helium to ionise so no such lines can form in the spectrum. Even though spectral lines due to helium are not found in cool stars it does not mean that helium is missing from the star. In fact helium is the second most abundant element in the Universe and in stars.
Why do stars have different spectral lines?
The variations in spectral lines for different stars are due primarily to the difference in temperature of the outer layers of gas in the star. In very hot stars, helium can be ionised so we can expect to see spectral lines due to absorption by helium ions.
What are the different types of stars?
Some stars exhibit spectral anomalies resulting in them being given special classifications: 1 R -class stars have the same temperature as K-class stars but have high abundances of carbon and carbon molecules. 2 N -class stars are carbon-rich stars with the same temperature as M-class stars. 3 S -class stars are similar temperature to M stars but have bands of zirconium oxide and lanthanum oxide. 4 WN and WC are two types of Wolf-Rayet stars, the same temperature as O-class stars but showing strong broad emission lines of carbon and nitrogen respectively.
How to compare stellar spectra?
Another way of comparing stellar spectra is by studying their intensity plots. The sequence below is for main sequence stars from about the middle of each spectral class. It shows the spectrum for a small region of the visible waveband from 390 - 450 nm.
What are the spectral types of stars?
Most stars are grouped into a small number of spectral types. The Henry Draper Catalogue and the Bright Star Catalogue list spectral types from the hottest to the coolest stars ( see stellar classification ). These types are designated, in order of decreasing temperature, by the letters O, B, A, F, G, K, and M.
What are the metals in the spectra of cool stars?
In the case of cool stars of type M, the spectra indicate the presence of familiar metals, including iron, calcium, magnesium, and also titanium oxide molecules ( TiO), particularly in the red and green parts of the spectrum. In the somewhat hotter K-type stars, the TiO features disappear, and the spectrum exhibits a wealth of metallic lines. A few especially stable fragments of molecules such as cyanogen (CN) and the hydroxyl radical (OH) persist in these stars and even in G-type stars such as the Sun. The spectra of G-type stars are dominated by the characteristic lines of metals, particularly those of iron, calcium, sodium, magnesium, and titanium.
What are the elements that make up the spectral lines of G-type stars?
The spectra of G-type stars are dominated by the characteristic lines of metals, particularly those of iron, calcium, sodium, magnesium, and titanium.
What type of stars are carbon?
This group is supplemented by R- and N-type stars (today often referred to as carbon, or C-type, stars) and S-type stars. The R-, N-, and S-type stars differ from the others in chemical composition; also, they are invariably giant or supergiant stars. With the discovery of brown dwarfs —objects that form like stars but do not shine ...
What are the lines of helium in hot B stars?
Thereafter, these absorption lines gradually fade as the hydrogen becomes ionized. The hot B-type stars, such as Epsilon Orionis, are characterized by lines of helium and of singly ionized oxygen, nitrogen, and neon. In very hot O-type stars, lines of ionized helium appear.
What is the luminosity class of a star?
Keenan, who introduced it), luminosity class is assigned to the star along with the Draper spectral type. For example, the star Alpha Persei is classified as F5 Ib , which means that it falls about halfway ...
Which type of star has hydrogen lines?
In stars of spectral type F, the lines of neutral atoms are weak relative to those of ionized atoms. The hydrogen lines are stronger, attaining their maximum intensities in A-type stars, in which the surface temperature is about 9,000 K. Thereafter, these absorption lines gradually fade as the hydrogen becomes ionized.
Spectral types: O-B-A-F-G-K-M
OBAFGKM is an acronym for the seven main spectral types of stars. The table below shows the effective temperature range, chromaticity, mass, radius, and luminosity of stars in each class, as well as their average life span.
Luminosity classes
The Morgan-Keenan system of classifying stellar spectra kept the spectral classes introduced in the Harvard classification system, but added luminosity classes to distinguish between different types of stars. A Roman numeral is used to distinguish between different luminosity classes. These are:
Evolutionary stages
Stars are also divided based on their evolutionary stages, which are similar to luminosity classes. Throughout its life cycle, a star will be a protostar, a pre-main-sequence star, a main sequence star, and possibly a giant or supergiant. Depending on its initial mass, it will end its life as a white dwarf, a neutron star, or a black hole.
Stellar mass
The life cycle of a star is determined primarily by the star’s mass. The more massive a star is, the faster it will burn through its supply of hydrogen fuel. When hydrogen fusion stops, the star evolves away from the main sequence to become a giant. Astronomers divide stars into several groups based on mass:
Hertzsprung-Russell diagram
The Hertzsprung-Russell diagram (HR diagram) is a diagram that shows the relationship between the stars’ luminosities (absolute magnitudes) and their effective temperatures or spectral classes. It was named after the Danish astronomer Ejnar Hertzsprung and American astronomer Henry Norris Russell, who created it independently in the 1910s.
1. Young stellar objects (YSOs)
Protostars are newly formed stars that are still gathering material from the surrounding molecular cloud. They are formed when a fragment of the parent molecular cloud collapses under the force of its own gravity and a core forms within the fragment.
2. Main sequence stars
Main sequence stars, or dwarfs, are stars that generate energy through nuclear fusion of hydrogen into helium in their cores. They are the most numerous stars in the universe (not including substellar objects). The energy that they generate in the core is carried to the surface and radiated away at the photosphere.
