# BookRiff

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## What determines the brightness of stars?

However, the brightness of a star depends on its composition and how far it is from the planet. Astronomers define star brightness in terms of apparent magnitude — how bright the star appears from Earth — and absolute magnitude — how bright the star appears at a standard distance of 32.6 light-years, or 10 parsecs.

What spectral class of stars is the brightest?

The most widely used system of star classification divides stars of a given spectral class into six categories called luminosity classes. These luminosity classes are denoted by Roman numbers as follows: Ia: Brightest supergiants. Ib: Less luminous supergiants.

### What 3 factors determine a star’s brightness?

The intrinsic properties of stars include brightness, color, temperature, mass, and size. Three factors control the brightness of a star as seen from Earth: how big it is, how hot it is, and how far away it is. Magnitude is the measure of a star’s brightness.

How do you find the apparent brightness of a star?

The apparent brightness of a star is the rate at which energy (in the form of light) reaches your telescope, divided by the area of your telescope’s mirror or lens.

#### What are the 2 methods for measuring brightness of stars?

To measure the Luminosity of a star you need 2 measurements: the Apparent Brightness (flux) measured via photometry, and. the Distance to the star measured in some way.

What are the two ways of measuring the brightness of stars?

Hence we can say that there are two ways to measure the brightness of a star; the apparent magnitude of the brightness of the star is the brightness seen from the earth and absolute magnitude of the brightness of the star which is the brightness of a star seen from the standard distance of 32.6 light years or 10 …

## What are the 7 spectral classes of stars?

The stars are divided into 7 classes designated by the letters O, B, A, F, G, K, and M; the hottest stars (O and B) are blue-white in color, while the coolest (M) are red.

Which factor most affects the brightness of a star?

As the size of a star increases, luminosity increases. If you think about it, a larger star has more surface area. That increased surface area allows more light and energy to be given off. Temperature also affects a star’s luminosity.

### What is a star that explosively increases in brightness?

neutron star. a star of extremely high density composed entirely of neutrons. nova. a star that explosively increases in brightness.

How do you calculate brightness?

The brightness depends on only two things: the luminosity of the light-bulb, and the distance from the bulb to the screen. Here the denominator is just the area of a sphere of radius D. All that this formula says is that brightness is the luminosity divided by the area which is illuminated.

#### How many times does the brightness of a star differ?

Since the difference is 2.5 times for each “step” of magnitude, the total difference in brightness is 2.5 × 2.5 = 6.25 times. Here are a few rules of thumb that might help those new to this system. If two stars differ by 0.75 magnitudes, they differ by a factor of about 2 in brightness.

How are spectral characteristics used to classify stars?

Spectral characteristics offer a way to classify stars which gives information about temperature in a different way – particular absorption lines can be observed only for a certain range of temperatures because only in that range are the involved atomic energy levels populated. The standard classes are: Temperature O 30,000 – 60,000 K

## What kind of spectra do blue stars have?

Included are blue stars with surface temperatures of 20,000 to 35,000K. The thermal energyis so great at these temperatures that most surface hydrogen is completely ionized so hydrogen (HI) lines are weak. Unionized helium (HeI) is visible but the stronger spectra are of mulitple ionized atoms (HeII, CIII, NIII,OIII,SiV).

Who was the first person to measure the brightness of the stars?

The process of measuring the apparent brightness of stars is called photometry (from the Greek photo meaning “light” and – metry meaning “to measure”). As we saw Observing the Sky: The Birth of Astronomy, astronomical photometry began with Hipparchus. Around 150 B.C.E., he erected an observatory on the island of Rhodes in the Mediterranean.