NGC 7840

{{Short description|Galaxy in the constellation Pisces}}

{{Infobox galaxy

| name = NGC 7840

| image = File:Ngc7840.jpg

| caption = SDSS image of NGC 7840

| credit =

| epoch = J2000

| pronounce =

| constellation name = PiscesCelestial Atlas, [http://cseligman.com/text/atlas/ngc78.htm#7840 "NGC Object 7840"], Courtney Seligman, March 2010 (accessed 2010-10-27)WikiSky, [http://server1.wikisky.org/starview?object_type=2&object_id=67886 "NGC 7840"] (accessed 2010-10-17)

| ra = {{RA|00|07|08.79}}{{cite web|url=http://leda.univ-lyon1.fr/ledacat.cgi?o=NGC%207840|title=Search specification: NGC 7840|work=HyperLeda|publisher=Université Claude Bernard Lyon 1|accessdate=2021-02-12}}

| dec = {{DEC|+08|22|59.6}}

| z =

| h_radial_v =

| gal_v =

| group_cluster =

| type = S?

| mass_light_ratio =

| stars =

| appmag_v = 15

| absmag_v =

| size_v = 0.676{{prime}} × 0.457{{prime}}

| notes =

| names = {{odlist|PGC=1345780|2MASX=J00070878+0822598}}

| references =

}}

NGC 7840, the last numerical entry in the New General Catalogue, is an unbarred spiral galaxy in the constellation Pisces. Its velocity with respect to the cosmic microwave background is 10906 ± 49 km/s, which corresponds to a Hubble distance of 160.85 ± 11.30 Mpc (~524 million light-years), and its diameter is about 162,000 light-years.{{cite web

| title=NASA/IPAC Extragalactic Database

| work=Results for NGC 7840

| url=http://ned.ipac.caltech.edu/byname?objname=NGC+7840

| access-date=3 August 2024}} It was discovered by German astronomer Albert Marth on 29 November 1864.

For observing from Earth's surface, it has a magnitude of 15.5 in the early 21st century.{{Cite book|url=https://books.google.com/books?id=qEhpS7d5ZdAC&dq=NGC+7840&pg=PA345|title=1,001 Celestial Wonders to See Before You Die: The Best Sky Objects for Star Gazers|last=Bakich|first=Michael E.|date=2010-07-10|publisher=Springer Science & Business Media|isbn=9781441917775|language=en}} One observing guide recommended a telescope with a least 300mm aperture for observations.