IC 1101, one of the largest known objects of its kind, is a:

IC 1101 is a supergiant elliptical galaxy and is often cited as one of the largest known galaxies in the universe.

Location:

• IC 1101 lies at the centre of the galaxy cluster Abell 2029, in the constellation Virgo.
• It is about one billion light-years away from the Earth.

Size:

Estimates of its size vary because its outer halo of stars fades gradually. Some estimates suggest that its diffuse halo stretches across millions of light-years.

For comparison, our own galaxy is about 1,00,000 light-years across.

It may contain about 100 trillion stars, compared with roughly 100 to 400 billion stars in our galaxy.

Nature of the galaxy:

• It is classified as a cD galaxy, a type of very large elliptical galaxy found at the centres of galaxy clusters.
• Such galaxies are believed to have grown by merging with and absorbing many smaller galaxies over billions of years.
• Most of its stars are old and reddish, and very few new stars are being formed.
• It is thought to host a very massive black hole at its centre, possibly among the largest known.
• "IC" stands for Index Catalogue, a well-known astronomical catalogue of deep-sky objects.

What a galaxy is:

• A galaxy is a huge system of stars, gas, dust and dark matter held together by gravity.
• Galaxies are classified by shape into spiral, elliptical and irregular galaxies, a scheme introduced by Edwin Hubble.
• The observable universe is estimated to contain hundreds of billions to about two trillion galaxies.

Our galaxy:

Our solar system lies in a barred spiral galaxy, about 26,000 light-years from its centre.

Why not the other options?

• ✗IC 1101 is not a single star; the largest known stars are red supergiants like UY Scuti and Stephenson 2-18.
• ✗It is not a black hole, although it may contain a supermassive one.
• ✗It is not a comet; comets are small icy bodies of the solar system.