Question

What method might you use to determine the distance to an elliptical galaxy in our local group?

the Tully-Fisher relation

spectroscopic parallax

variable stars

Hubble's law

Answer 1

Ans)

1)The Tully-Fisher relation, which correlates the width of the 21-cm line of hydrogen in a spiral galaxy with its luminosity, can also be used for determining distance

The Tully- Fisher relation method that can be used for elliptical galaxies is the fundamental plane, which relates the galaxy’s size to its surface brightness distribution and to the motions of its stars.

2)Spectroscopic parallax is an astronomical method for measuring the distances to stars. Despite its name, it does not rely on the apparent change in the position of the star. This technique can be applied to any main sequence star for which a spectrum can be recorded

3)Variable stars are stars that change brightness. The brightness changes of thesestars can range from a thousandth of a magnitude to as much as twenty magnitudes over periods of a fraction of a second to years,

All stars appear to twinkle due to our ever-turbulent atmosphere. But some truly do rise and fall in brightness. These so-called variable stars

A star is called a variable star if its apparent brightness as seen from Earth changes over time. 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.

.4)The Hubble law relates the redshifts of remote galaxies to their distances from the Earth

The Hubble law is v = H₀d

So finally the Tully-Fisher relation method is used to determine the distance

To an elliptical galaxy in our local group.