Which of the following objects would be visible on Earth from the largest distance?

Question

..That is, which of these do you expect would be easiest to detect, even if it was more than a billion parsecs from Earth?

a G Main Sequence star

a neutron star

a Type Ia supernova

a planetary nebula

Answer 1

as 6 billion kilometers away, earth just visible as a dot, and reflected by our sun as a red color.

Answer 2

Supernova

Answer 3

A Hollywood star like Alec Baldwin or Halle Berry would be visible the farthest distance, because their egos are enormous.

(Do your own homework, kiddie)

Answer 4

a Type Ia supernova

Answer 5

A type 1a Supernovae.

Hundreds of years ago, a  supernova was seen (recorded) by the Chinese in 1054. The supernova explosion was witnessed in the area of Earth's sky where today we see an expanding gas cloud that we call Crab Nebula. The supernova was so bright it was visible in daylight.

The others, the G main sequence star and the planetary nebula can be seen with the naked eye - the star, depending on its luminosity, will look like the typical stars you see overhead at night.

The planetary nebula, will look like a faint "smudge" to the naked eye.

Now the neutron star cannot be seen with the naked eye, you would need special equipment to view it, such as an X-ray satellite, like NASA's Chandra.

Hope this helps you out.

Answer 6

While it is true, as has been pointed out, that Type Ia supernova are the brightest of the objects you listed, the hard part is the phrase "...more than a billion parsecs from Earth?"

This is an enormous distance, more than 3.25 billion light years. At that distance even single *galaxies* are very difficult to detect; we see galactic clusters. True, a supernova is as bright or brighter than its galaxy, but it is so short lived that spotting it would  be very difficult. Moreover, picking it out from a galactic cluster would aslo be very, very difficult.

So, theoretically the supernova wins, but in reality none of them are visible at the distance you have named.

HTH

Charles