# Most distant object in space visible with the naked eye? **URL:** \ **Category:** Factual Questions\ **Created:** [November 26, 2003, 5:52pm UTC](https://boards.straightdope.com/t/most-distant-object-in-space-visible-with-the-naked-eye/215421 "2003-11-26T17:52:16Z")\ **Posts on this page:** 20\ **Page:** 1
**Author:** ![plnnr](https://avatars.discourse-cdn.com/v4/letter/p/7ea924/32.png) [@plnnr](https://boards.straightdope.com/u/plnnr)\ **Post date:** [November 26, 2003, 5:52pm UTC](https://boards.straightdope.com/t/most-distant-object-in-space-visible-with-the-naked-eye/215421/1 "2003-11-26T17:52:16Z")
While laying back in the hot tub the other night and sipping very dry martinis, my wife and I were looking up at the stars and commenting on how the light has travelled such a great distance, and how we were essentially looking back in time. She asked me, and I’m asking you, the masses: What is the most distance object that can be seen from the Earth with the naked eye and when did the light that we’re just now seeing leave the object? In other words, how far back in time are we able to see? ---
**Author:** ![Q.E.D](https://avatars.discourse-cdn.com/v4/letter/q/51bf81/32.png) [@Q.E.D](https://boards.straightdope.com/u/Q.E.D)\ **Post date:** [November 26, 2003, 6:00pm UTC](https://boards.straightdope.com/t/most-distant-object-in-space-visible-with-the-naked-eye/215421/2 "2003-11-26T18:00:38Z")
The Andromeda galaxy is about 2 million light-years distant. That’s the farthest object I can think of off the top of my head. I’m sure there’s other, more distant galaxies that are naked eye objects. ---
**Author:** ![Q.E.D](https://avatars.discourse-cdn.com/v4/letter/q/51bf81/32.png) [@Q.E.D](https://boards.straightdope.com/u/Q.E.D)\ **Post date:** [November 26, 2003, 6:03pm UTC](https://boards.straightdope.com/t/most-distant-object-in-space-visible-with-the-naked-eye/215421/3 "2003-11-26T18:03:10Z")
And according to [this](http://www.ipinc.net/~paullund/distant.htm) I was correct. ---
**Author:** ![Squink](https://avatars.discourse-cdn.com/v4/letter/s/b5e925/32.png) [@Squink](https://boards.straightdope.com/u/Squink)\ **Post date:** [November 26, 2003, 6:05pm UTC](https://boards.straightdope.com/t/most-distant-object-in-space-visible-with-the-naked-eye/215421/4 "2003-11-26T18:05:29Z")
> [@](#): > > \*Originally posted by Q.E.D. \* > I’m sure there’s other, more distant galaxies that are naked eye objects. Or incorrect. Either way, it’s the galaxt in Andromeda. ---
**Author:** ![Q.E.D](https://avatars.discourse-cdn.com/v4/letter/q/51bf81/32.png) [@Q.E.D](https://boards.straightdope.com/u/Q.E.D)\ **Post date:** [November 26, 2003, 6:07pm UTC](https://boards.straightdope.com/t/most-distant-object-in-space-visible-with-the-naked-eye/215421/5 "2003-11-26T18:07:59Z")
😛 ---
**Author:** ![Napier](https://avatars.discourse-cdn.com/v4/letter/n/ce73a5/32.png) [@Napier](https://boards.straightdope.com/u/Napier)\ **Post date:** [November 26, 2003, 6:32pm UTC](https://boards.straightdope.com/t/most-distant-object-in-space-visible-with-the-naked-eye/215421/6 "2003-11-26T18:32:19Z")
There’s a galaxy in Triangulum that’s further than the Andromeda galaxy. Some people can see it with the naked eye, but not everybody can. ---
**Author:** ![Q.E.D](https://avatars.discourse-cdn.com/v4/letter/q/51bf81/32.png) [@Q.E.D](https://boards.straightdope.com/u/Q.E.D)\ **Post date:** [November 26, 2003, 6:56pm UTC](https://boards.straightdope.com/t/most-distant-object-in-space-visible-with-the-naked-eye/215421/7 "2003-11-26T18:56:19Z")
> [@](#): > > \*Originally posted by Napier \* > \*\*There’s a galaxy in Triangulum that’s further than the Andromeda galaxy. Some people can see it with the naked eye, but not everybody can. \*\* That would be [M-33](http://www.astro.univie.ac.at/~exgalak/koprolin/Photo/Gal/M33_APO.html), which is 2.4 million light-years from us. I know _I_ can’t see it as a naked eye object. ---
**Author:** ![Polycarp](https://avatars.discourse-cdn.com/v4/letter/p/82dd89/32.png) [@Polycarp](https://boards.straightdope.com/u/Polycarp)\ **Post date:** [November 26, 2003, 7:31pm UTC](https://boards.straightdope.com/t/most-distant-object-in-space-visible-with-the-naked-eye/215421/8 "2003-11-26T19:31:44Z")
M33 is naked-eye visible on nights with ideal seeing for people with perfect vision, according to what I read. M31 is the farthest the rest of us can see. As I understand it, visible to the naked eye under ideal seeing conditions (\* indicates at the edge of visibility) are: 1. Six major planets (Mercury, Venus, Mars, Jupiter, Saturn, Uranus\*) 2. One minor planet/large asteroid: Vesta\* 3. One satellite: the Moon 4. ~6,000 stars, all supergiants, giants, or relatively nearby main sequence stars of K and up spectra. 5. Several nebulae, number unknown to me. 6. One globular cluster: Omega Centauri\* 7. Four galaxies: the Magellanic Clouds, M31 in Andromeda, and M33 in Triangulum\*. Everything else requires a telescope ---
**Author:** ![rsa](https://avatars.discourse-cdn.com/v4/letter/r/839c29/32.png) [@rsa](https://boards.straightdope.com/u/rsa)\ **Post date:** [November 26, 2003, 7:48pm UTC](https://boards.straightdope.com/t/most-distant-object-in-space-visible-with-the-naked-eye/215421/9 "2003-11-26T19:48:30Z")
> [@](#): > > \*Originally posted by plnnr \* > What is the most distance object that can be seen from the Earth with the naked eye and when did the light that we’re just now seeing leave the object? In other words, how far back in time are we able to see? Although 2.3 million light-years is often quoted as the distance to the Andromeda Galaxy, I believe that more recent observations suggest a distance of more like 2.9 million light-years. The Andromeda Galaxy has a “peculiar” velocity of 100km/s towards the Milky Way. If I used the Google calculator correctly that would mean that Andromeda was a bit more distant when the light we see left it (but just by about 1000 light-years). ---
**Author:** ![bughunter](https://avatars.discourse-cdn.com/v4/letter/b/aeb1de/32.png) [@bughunter](https://boards.straightdope.com/u/bughunter)\ **Post date:** [November 26, 2003, 7:58pm UTC](https://boards.straightdope.com/t/most-distant-object-in-space-visible-with-the-naked-eye/215421/10 "2003-11-26T19:58:32Z")
> [@](#): > > \*Originally posted by Polycarp \* > **4. ~6,000 stars, all supergiants, giants, or relatively nearby main sequence stars of K and up spectra.** Only about six thousand? Gee, I thought it was billions and billions. Or was Carl Sagan on drugs? Oh. :smack: Never mind. Carry on. ---
**Author:** ![vd](https://avatars.discourse-cdn.com/v4/letter/v/b19c9b/32.png) [@vd](https://boards.straightdope.com/u/vd)\ **Post date:** [November 26, 2003, 8:05pm UTC](https://boards.straightdope.com/t/most-distant-object-in-space-visible-with-the-naked-eye/215421/11 "2003-11-26T20:05:45Z")
> [@](#): > > 1. One satellite: the Moon One _natural_ satellite anyway. > [@](#): > > 1. Four galaxies: the Magellanic Clouds, M31 in Andromeda, and M33 in Triangulum\*. And the Milky Way:D ---
**Author:** ![PetW](https://avatars.discourse-cdn.com/v4/letter/p/d2c977/32.png) [@PetW](https://boards.straightdope.com/u/PetW)\ **Post date:** [November 26, 2003, 8:15pm UTC](https://boards.straightdope.com/t/most-distant-object-in-space-visible-with-the-naked-eye/215421/12 "2003-11-26T20:15:12Z")
> [@](#): > > \*Originally posted by vd \* > \*\*One _natural_ satellite anyway. > > And the Milky Way:D \*\* Can you see any non-natural satellites with the naked eye? ---
**Author:** ![MC\_Master\_of\_Ceremonies](https://avatars.discourse-cdn.com/v4/letter/m/bb73d2/32.png) [@MC\_Master\_of\_Ceremonies](https://boards.straightdope.com/u/MC_Master_of_Ceremonies)\ **Post date:** [November 26, 2003, 8:26pm UTC](https://boards.straightdope.com/t/most-distant-object-in-space-visible-with-the-naked-eye/215421/13 "2003-11-26T20:26:00Z")
> [@](#): > > \*Originally posted by PetW \* > \*\*Can you see any non-natural satellites with the naked eye? \*\* Yes, if you’re looking at the right place at the right time. ---
**Author:** ![Squink](https://avatars.discourse-cdn.com/v4/letter/s/b5e925/32.png) [@Squink](https://boards.straightdope.com/u/Squink)\ **Post date:** [November 26, 2003, 8:35pm UTC](https://boards.straightdope.com/t/most-distant-object-in-space-visible-with-the-naked-eye/215421/14 "2003-11-26T20:35:32Z")
A type 1a supernova with an [absolute magnitude of -19.5](http://adsabs.harvard.edu/cgi-bin/nph-bib_query?2002AJ....123..745R) would be _just_ visible to the naked eye, mag. 6, at a distance of 4,104,097 light years. Using m = M + 5log(d) - 5 ( M = absolute magnitude, d is in parsecs (3.2 LY)) You’d have to know where to look, and catch the star in the first few hours after it exploded. ---
**Author:** ![vd](https://avatars.discourse-cdn.com/v4/letter/v/b19c9b/32.png) [@vd](https://boards.straightdope.com/u/vd)\ **Post date:** [November 26, 2003, 8:38pm UTC](https://boards.straightdope.com/t/most-distant-object-in-space-visible-with-the-naked-eye/215421/15 "2003-11-26T20:38:17Z")
See [here](http://spaceflight.nasa.gov/realdata/sightings/index.html) for when the ISS and other satellites can be seen from your location. The ISS is quite bright and can easily be seen (at least in the suburbs). From a dark location you can just watch for movement for 15 minutes or so, and eventually you’ll see something cruising by in low earth orbit ---
**Author:** ![Colophon](https://avatars.discourse-cdn.com/v4/letter/c/f05b48/32.png) [@Colophon](https://boards.straightdope.com/u/Colophon)\ **Post date:** [November 26, 2003, 8:46pm UTC](https://boards.straightdope.com/t/most-distant-object-in-space-visible-with-the-naked-eye/215421/16 "2003-11-26T20:46:25Z")
> [@](#): > > Only about six thousand? Gee, I thought it was billions and billions. Or was Carl Sagan on drugs? Oh, there are billions and billions, but you can’t see most of them. ---
**Author:** ![sick-boy](https://avatars.discourse-cdn.com/v4/letter/s/b5ac83/32.png) [@sick-boy](https://boards.straightdope.com/u/sick-boy)\ **Post date:** [November 26, 2003, 9:13pm UTC](https://boards.straightdope.com/t/most-distant-object-in-space-visible-with-the-naked-eye/215421/17 "2003-11-26T21:13:29Z")
The reason why you can’t see them is obvious. All stars emit light with a certain power. If the energy flux from the star reaching your eye is above a certain limit ( 8,8\*10^-11 w/m2) you can see the star. If not, you can’t see it. If we make some assumptions we can easily calculate the amount of visible stars. If we assume that all stars emit light like our Sun, that is, with P=3,9_10^26W, and that there are 3,5_10^-3 stars per cubic meter in the space surrounding us, we can calculate that the amount of visible stars is 3700. Not all stars emit light like Sun and their density in space is not constant, but I hope this crude model helps somebody… ---
**Author:** ![Squink](https://avatars.discourse-cdn.com/v4/letter/s/b5e925/32.png) [@Squink](https://boards.straightdope.com/u/Squink)\ **Post date:** [November 26, 2003, 9:33pm UTC](https://boards.straightdope.com/t/most-distant-object-in-space-visible-with-the-naked-eye/215421/18 "2003-11-26T21:33:41Z")
> [@](#): > > _Originally posted by sick-boy \* > The reason why you can’t see them is obvious. All stars emit light with a certain power. If the energy flux from the star reaching your eye is above a certain limit ( 8,8_10^-11 w/m2) you can see the star. If not, you can’t see it. I put together a chart of the maximum distance at which various types of stars would be visible to the naked eye back in this thread: [Naked eye viewing](http://boards.straightdope.com/sdmb/showthread.php?s=&postid=2888950&highlight=absolute+AND+magnitude#post2888950) ---
**Author:** ![Malacandra](https://avatars.discourse-cdn.com/v4/letter/m/45deac/32.png) [@Malacandra](https://boards.straightdope.com/u/Malacandra)\ **Post date:** [November 26, 2003, 11:37pm UTC](https://boards.straightdope.com/t/most-distant-object-in-space-visible-with-the-naked-eye/215421/19 "2003-11-26T23:37:06Z")
Hasn’t _s Doradus_ flared up in historical times bright enough to be a naked-eye object, and isn’t that in the Lesser Magellanic Cloud? Can’t find the reference at the moment. (That’s barely a tenth of the distance to the Andromeda galaxy, but a single star rather than a galaxy or cluster.) ---
**Author:** ![Tim\_T-Bonham.net](https://avatars.discourse-cdn.com/v4/letter/t/46a35a/32.png) [@Tim\_T-Bonham.net](https://boards.straightdope.com/u/Tim_T-Bonham.net)\ **Post date:** [November 27, 2003, 1:31am UTC](https://boards.straightdope.com/t/most-distant-object-in-space-visible-with-the-naked-eye/215421/20 "2003-11-27T01:31:43Z")
Slightly off topic, but [this site](http://antwrp.gsfc.nasa.gov/apod/) posts a new Astronomy picture of the day every day, with an explanation of each one. Some of them are photos of the things talked about in this thread. And many of them are very interesting photos. I found one that I liked so much I used it as my PC wallpaper. [Next page](https://boards.straightdope.com/t/most-distant-object-in-space-visible-with-the-naked-eye/215421.md?page=2)