## What are examples of variable stars?

The Cepheids and RR Lyrae stars are typical examples of such variables. The explosive (or eruptive) variables include novas, supernovas, and similar stars that undergo sudden outbursts of radiant energy, which results in rapid brightening.

### How many types of variable stars are there?

two
There are two basic types of variable stars: intrinsic variables, whose luminosity actually changes, and extrinsic variables, whose apparent changes in brightness are due to changes in the amount of their light that can reach Earth. A star could be an intrinsic variable because it periodically swells and shrinks.

#### What type of star is a Cepheid variable?

A Cepheid variable (/ˈsɛfi. ɪd, ˈsiːfi-/) is a type of star that pulsates radially, varying in both diameter and temperature and producing changes in brightness with a well-defined stable period and amplitude.

How do you know if a star is a variable?

Divide the difference between the two stars (in this case magnitude 0.4) into a fraction, and place the variable’s brightness in it. The fraction you choose is thirds, and you see that T Cephei is one third fainter than 101 and therefore two thirds brighter than 105. You write 101(1) v (2)105 (‘v’ being the variable).

Is Sun a variable star?

Our own sun is a variable star; its energy output varies by approximately 0.1 percent, or one-thousandth of its magnitude, over an 11-year solar cycle.

## Do brown dwarfs have fusion?

In addition, many brown dwarfs undergo no fusion; even those at the high end of the mass range (over 60 M J) cool quickly enough that after 10 million years they no longer undergo fusion.

### Is Betelgeuse a Cepheid variable?

One of the best-known Semiregular Variables is Betelgeuse. Irregular pulsating variables have also been identified. These are usually red supergiants, but very little study has been done on them. When it comes to changing astronomers’ perception of the universe, the Cepheid variable V1 played one of the pivotal roles.

#### Why do Cepheids pulsate?

A Cepheid pulsates in a regular and predictable cycle. It is thought that Helium is involved in its cycle. Doubly ionized Helium is more opaque than singly ionized helium, meaning it lets little light through. At the dimmest part of the cycle, doubly ionized Helium makes up the outer layers of the star.

Are Cepheids red giants?

cepheids. Classical Cepheid stars are supergiants of greater than 2-3 solar masses, that at the end of main-sequence H burning move across the HR diagram to become red giants, crossing the Cepheid instability strip. The type-II Cepheids are low-mass, high-luminosity pulsators, with periods from 1-40 days.

Who first calibrated the Cepheid variable?

The pattern was first noticed in 1784 in the constellation Cepheus in the northern sky, so these stars became known as “Cepheid variables.” Cepheid variables went from interesting to completely indispensable in the early 1900s thanks to the work by astronomer Henrietta Leavitt.

## Will the Sun become a variable star?

### What happens when a star dims?

The star is also a semi-regular variable, meaning that its brightness waxes and wanes in cycles. Eventually, red supergiants run out of fuel and die in a spectacular explosion, a supernova. Some who were watching the dimming wondered if this was a sign of its impending death.