# How far out before some other star is brighter than the Sun? **URL:** \ **Category:** Factual Questions\ **Created:** [November 23, 2012, 5:28am UTC](https://boards.straightdope.com/t/how-far-out-before-some-other-star-is-brighter-than-the-sun/641873 "2012-11-23T05:28:04Z")\ **Posts on this page:** 20\ **Page:** 1
**Author:** ![whc.03grady](https://avatars.discourse-cdn.com/v4/letter/w/a6a055/32.png) [@whc.03grady](https://boards.straightdope.com/u/whc.03grady)\ **Post date:** [November 23, 2012, 5:28am UTC](https://boards.straightdope.com/t/how-far-out-before-some-other-star-is-brighter-than-the-sun/641873/1 "2012-11-23T05:28:04Z")
How far out do you have to go before some other star is brighter than the Sun? Which star would it be? ---
**Author:** ![Washoe](https://avatars.discourse-cdn.com/v4/letter/w/ecae2f/32.png) [@Washoe](https://boards.straightdope.com/u/Washoe)\ **Post date:** [November 23, 2012, 5:49am UTC](https://boards.straightdope.com/t/how-far-out-before-some-other-star-is-brighter-than-the-sun/641873/2 "2012-11-23T05:49:13Z")
If I could pose a related question, I’ve often wondered this—how far do you have to be from the Sun before it looks like just another star? It’s probably not very far, astronomically speaking—probably just like a light-day or two, right? ---
**Author:** ![whc.03grady](https://avatars.discourse-cdn.com/v4/letter/w/a6a055/32.png) [@whc.03grady](https://boards.straightdope.com/u/whc.03grady)\ **Post date:** [November 23, 2012, 5:54am UTC](https://boards.straightdope.com/t/how-far-out-before-some-other-star-is-brighter-than-the-sun/641873/3 "2012-11-23T05:54:21Z")
It’s the same exact question, if you think about it. Given that Voyager 1 is currently about 2/3 of a light-day away, I’m betting it’s a lot further than that. ---
**Author:** ![Michael63129](https://avatars.discourse-cdn.com/v4/letter/m/3da27b/32.png) [@Michael63129](https://boards.straightdope.com/u/Michael63129)\ **Post date:** [November 23, 2012, 5:56am UTC](https://boards.straightdope.com/t/how-far-out-before-some-other-star-is-brighter-than-the-sun/641873/4 "2012-11-23T05:56:54Z")
I’d say it would be Sirius, which is the [brightest star](http://en.wikipedia.org/wiki/List_of_brightest_stars) in the night sky, considerably brighter than Canopus, the second brightest star (the closest star is Proxima Centauri, but it is a very dim red dwarf; Alpha Centauri A is about the same distance (4.4 ly) and brighter but still far less so than Sirius, which is also about twice the distance (8.6 ly) from Earth; Canopus is so far away (310 ly) that you will pass many other stars before reaching it). This assumes you are moving in the direction of Sirius though, but it could also be true for the opposite direction since Sirius is 25 times more luminous than the Sun. ---
**Author:** ![Washoe](https://avatars.discourse-cdn.com/v4/letter/w/ecae2f/32.png) [@Washoe](https://boards.straightdope.com/u/Washoe)\ **Post date:** [November 23, 2012, 6:14am UTC](https://boards.straightdope.com/t/how-far-out-before-some-other-star-is-brighter-than-the-sun/641873/5 "2012-11-23T06:14:14Z")
> [@whc.03grady](#): > > It’s the same exact question, if you think about it. Not necessarily. Let’s say that I’m right and it’s only a light-day or two or three. That would mean that all stars look like points of light until you get close to them. So let’s say I’m 9/10 of the way to Alpha Centauri. I look out one window, and I see Alpha Centauri—a point of light. I look out the other window and see our friend Sol—also just a point of light. The reason I’m assuming that the distance at which a star becomes a point of light is pretty small is that they _all look like points of light_—all 482 bajillion of them. If I’m not mistaken (and of course I’ll go look it up later to see if I am or not) they’re all just points of light even through the Hubble. So if I’m right, and you travel from here to Alpha Centauri, for 99.99% of the trip they’re both just dots. ---
**Author:** ![septimus](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/septimus/32/410_2.png) [@septimus](https://boards.straightdope.com/u/septimus)\ **Post date:** [November 23, 2012, 7:15am UTC](https://boards.straightdope.com/t/how-far-out-before-some-other-star-is-brighter-than-the-sun/641873/6 "2012-11-23T07:15:03Z")
I think Sirius is the answer, with its apparent magnitude the same as Sol’s at a distance of 1.5 light-years from us. Betelgeuse is much more than a single point when the best telescopes are used; [for example there is a view of Betelgeuse’s “atmosphere” near the bottom of this page.](http://www.holoscience.com/wp/the-mystery-of-the-shrinking-red-star/) ---
**Author:** ![blue\_infinity](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/blue_infinity/32/2817_2.png) [@blue\_infinity](https://boards.straightdope.com/u/blue_infinity)\ **Post date:** [November 23, 2012, 7:19am UTC](https://boards.straightdope.com/t/how-far-out-before-some-other-star-is-brighter-than-the-sun/641873/7 "2012-11-23T07:19:38Z")
According to my calculations: Sirius become brighter at 1.48ly from the Sun (7.13ly from Sirius). Alpha Centauri becomes brighter at 1.77ly from the Sun (2.47ly from Alpha Centauri). ---
**Author:** ![whc.03grady](https://avatars.discourse-cdn.com/v4/letter/w/a6a055/32.png) [@whc.03grady](https://boards.straightdope.com/u/whc.03grady)\ **Post date:** [November 23, 2012, 7:33am UTC](https://boards.straightdope.com/t/how-far-out-before-some-other-star-is-brighter-than-the-sun/641873/8 "2012-11-23T07:33:17Z")
Okay, it looks like Sirius. Two people can’t be wrong, right? Now for the presumably more difficult question, the one that prompted the OP: How far out will Voyager 1 have to go before, for it, some star is brighter than the Sun, and which star is that? ---
**Author:** ![Senegoid](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/senegoid/32/6606_2.png) [@Senegoid](https://boards.straightdope.com/u/Senegoid)\ **Post date:** [November 23, 2012, 12:00pm UTC](https://boards.straightdope.com/t/how-far-out-before-some-other-star-is-brighter-than-the-sun/641873/9 "2012-11-23T12:00:30Z")
I read somewhere that, from the distance of one of our own outer planets (Neptune or Uranus or maybe Pluto), our own sun looks much like another star. Sorry, don’t know where I read that, or how reliable that source might have been, or even how literally it might have been intended. ---
**Author:** ![Alka\_Seltzer](https://avatars.discourse-cdn.com/v4/letter/a/c89c15/32.png) [@Alka\_Seltzer](https://boards.straightdope.com/u/Alka_Seltzer)\ **Post date:** [November 23, 2012, 12:06pm UTC](https://boards.straightdope.com/t/how-far-out-before-some-other-star-is-brighter-than-the-sun/641873/10 "2012-11-23T12:06:10Z")
> [@whc.03grady](#): > > Now for the presumably more difficult question, the one that prompted the OP: How far out will Voyager 1 have to go before, for it, some star is brighter than the Sun, and which star is that? That’s quite difficult to work out. Voyager 1 isn’t travelling towards any star in particular, and is moving relatively slowly. Many of the stars in the solar neighbourhood are moving many times faster with respect to the solar system. It will take Voyager 1 about 26,000 years to travel 1.5 light years from the solar system. Looking at **blue infinity** ’s figures above, at that point Sirius or Alpha Centauri might be observed to be brighter than the Sun. Sirius is moving closer to the solar system over the next 60,000 years or so. Alpha Centauri is also moving towards to us, with a closest approach in about 27,000 years time. If Voyager is moving towards Alpha Centauri, it might be the first star to outshine the sun. Otherwise, it’s very likely to be Sirius. Voyager 1 is headed towards the constellation Ophiuchus. Looking on [Stellarium](http://www.stellarium.org/), that trajectory takes it closer to Alpha Centauri and further away from Sirius. Someone would need to find the actual trajectory of all three objects and do the maths to be sure of the outcome. I’m pretty sure it’s not going to be a different star. The only other stars which will make a close approach to the solar system in the next 80,000 stars are dim dwarf stars, and nothing in the near neighbourhood is likely to outshine Sirius. ---
**Author:** ![Arrogance\_Ex\_Machina](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/arrogance_ex_machina/32/192_2.png) [@Arrogance\_Ex\_Machina](https://boards.straightdope.com/u/Arrogance_Ex_Machina)\ **Post date:** [November 23, 2012, 1:05pm UTC](https://boards.straightdope.com/t/how-far-out-before-some-other-star-is-brighter-than-the-sun/641873/11 "2012-11-23T13:05:29Z")
> [@Senegoid](#): > > I read somewhere that, from the distance of one of our own outer planets (Neptune or Uranus or maybe Pluto), our own sun looks much like another star. > > Sorry, don’t know where I read that, or how reliable that source might have been, or even how literally it might have been intended. Looking at [this picture](http://en.wikipedia.org/wiki/File:ESO-L._Cal%C3%A7ada_-_Pluto_%28by%29.jpg) which shows what the Sun should look like from Pluto that doesn’t seem to be correct. Sun is still clearly the brightest thing on the sky and not just a tiny bright dot. ---
**Author:** ![Alka\_Seltzer](https://avatars.discourse-cdn.com/v4/letter/a/c89c15/32.png) [@Alka\_Seltzer](https://boards.straightdope.com/u/Alka_Seltzer)\ **Post date:** [November 23, 2012, 1:41pm UTC](https://boards.straightdope.com/t/how-far-out-before-some-other-star-is-brighter-than-the-sun/641873/12 "2012-11-23T13:41:07Z")
> [@Arrogance\_Ex\_Machina](#): > > Looking at [this picture](http://en.wikipedia.org/wiki/File:ESO-L._Cal%C3%A7ada_-_Pluto_%28by%29.jpg) which shows what the Sun should look like from Pluto that doesn’t seem to be correct. Sun is still clearly the brightest thing on the sky and not just a tiny bright dot. The sun does appear as a point source [from Pluto](http://blogs.discovermagazine.com/badastronomy/2012/03/16/bafact-math-how-big-does-the-sun-look-from-pluto/), although it would be much brighter than any other star, about [150 to 450 times as bright](http://blogs.discovermagazine.com/badastronomy/2012/03/15/bafact-math-how-bright-is-the-sun-from-pluto/) as a full moon (Pluto is in very elliptical orbit, so the distance to the Sun varies considerably). ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [November 23, 2012, 4:10pm UTC](https://boards.straightdope.com/t/how-far-out-before-some-other-star-is-brighter-than-the-sun/641873/13 "2012-11-23T16:10:59Z")
In almost any direction, the first star to outshine the Sun is going to be Sirius. The figure that **blue infinity** calculated depends much more on the Sun getting dimmer than on Sirius getting brighter, since 1.48 ly is relatively small compared to the 8.6 ly distance between us. In fact, my hunch is that even on the direct line to alpha Centauri at 1.77 ly out from the Sun (where the two are equal), Sirius would still be a tad brighter than either. And there are certainly no other contenders than Sirius or alpha Centauri. We want a star that’s both bright and close, and those two are the brightest and third-brightest (with the second-brightest being way-distant Canopus), respectively, and are also the two closest stars of non-negligible brightness (there are a couple of stars that are closer than Sirius, but they’re red dwarfs). ---
**Author:** ![Alka\_Seltzer](https://avatars.discourse-cdn.com/v4/letter/a/c89c15/32.png) [@Alka\_Seltzer](https://boards.straightdope.com/u/Alka_Seltzer)\ **Post date:** [November 23, 2012, 5:29pm UTC](https://boards.straightdope.com/t/how-far-out-before-some-other-star-is-brighter-than-the-sun/641873/14 "2012-11-23T17:29:55Z")
> [@Chronos](#): > > In fact, my hunch is that even on the direct line to alpha Centauri at 1.77 ly out from the Sun (where the two are equal), Sirius would still be a tad brighter than either. I think you are probably right. However, by the time Voyager reaches the point where Sirius is brighter, Alpha Centauri will only be about 3 light years from the Sun, rather than it’s current distance of 4.36 light years. The question can’t be answered without knowing the trajectories of Voyager, Alpha Centauri and Sirius. ---
**Author:** ![septimus](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/septimus/32/410_2.png) [@septimus](https://boards.straightdope.com/u/septimus)\ **Post date:** [November 23, 2012, 6:39pm UTC](https://boards.straightdope.com/t/how-far-out-before-some-other-star-is-brighter-than-the-sun/641873/15 "2012-11-23T18:39:47Z")
> [@Chronos](#): > > In fact, my hunch is that even on the direct line to alpha Centauri at 1.77 ly out from the Sun (where the two are equal), Sirius would still be a tad brighter than either. We seem to be using different numbers. I see -0.27 as the apparent magnitude of the _double_ star Alpha Centauri, and see 1.83 ly (along the line Earth-Centauri) as the point of equal brightness with Sol. From [this page](http://celestialwonders.com/tools/starAngleCalc.html) the angle between Sirius and Alpha Centauri (with vertex Earth) seems to be 88.4 degrees(\*). Given that, I get that Sirius is slightly dimmer than Alpha Centauri at the point along Earth-Centauri where Sol and Alpha Centauri are equally bright. The Sirius brightness, relative to the equal Sol/Alpha Centauri brightness can be reduced further by traveling about 15 degrees further anti-Sirius instead of along the straight Earth-Centauri line. (\* - In the relatively unlikely case I made no user error!) ---
**Author:** ![dimmy\_derko](https://avatars.discourse-cdn.com/v4/letter/d/43a26b/32.png) [@dimmy\_derko](https://boards.straightdope.com/u/dimmy_derko)\ **Post date:** [November 23, 2012, 10:17pm UTC](https://boards.straightdope.com/t/how-far-out-before-some-other-star-is-brighter-than-the-sun/641873/16 "2012-11-23T22:17:51Z")
> [@Alka\_Seltzer](#): > > That’s quite difficult to work out. Voyager 1 isn’t travelling towards any star in particular, and is moving relatively slowly. Many of the stars in the solar neighbourhood are moving many times faster with respect to the solar system. > > It will take Voyager 1 about 26,000 years to travel 1.5 light years from the solar system. I take it all solar systems are orbiting the galactic centre in the same direction, yes? And our sun(along with the planets it drags with it) is moving at a pretty hefty rate, w/e that direction it’s going in is, right? So, if we wanted to send something like Voyager out of the solar system as quick as possible, why can’t we point it in the reverse direction of our solar system and leave it behind in our non-wake? What is the procedure when they are aiming one of these long-distance probes? Do they have to point it in a direction where it isn’t going to interact with any of the outer planets if they just want it to leave the solar system? ---
**Author:** ![MikeS](https://avatars.discourse-cdn.com/v4/letter/m/919ad9/32.png) [@MikeS](https://boards.straightdope.com/u/MikeS)\ **Post date:** [November 23, 2012, 10:43pm UTC](https://boards.straightdope.com/t/how-far-out-before-some-other-star-is-brighter-than-the-sun/641873/17 "2012-11-23T22:43:10Z")
> [@dimmy\_derko](#): > > What is the procedure when they are aiming one of these long-distance probes? Do they have to point it in a direction where it isn’t going to interact with any of the outer planets if they just want it to leave the solar system? No, you **want** the probe to interact with the outer planets. If you [do it right,](http://en.wikipedia.org/wiki/Gravity_assist) you can give the probe a lot more speed relative to the Sun than you could if you just use your rockets. ---
**Author:** ![Alka\_Seltzer](https://avatars.discourse-cdn.com/v4/letter/a/c89c15/32.png) [@Alka\_Seltzer](https://boards.straightdope.com/u/Alka_Seltzer)\ **Post date:** [November 23, 2012, 11:10pm UTC](https://boards.straightdope.com/t/how-far-out-before-some-other-star-is-brighter-than-the-sun/641873/18 "2012-11-23T23:10:19Z")
[quote=“dimmy\_derko, post:16, topic:641873”] I take it all solar systems are orbiting the galactic centre in the same direction, yes? [quote] Yes, but all at different speeds, wobbling in and out of the plane of the disc. > [@dimmy\_derko](#): > > So, if we wanted to send something like Voyager out of the solar system as quick as possible, why can’t we point it in the reverse direction of our solar system and leave it behind in our non-wake? It’s not like throwing a cigarette out of a car window. Ignoring other factors, it doesn’t matter which way you accelerate a rocket, it’s velocity with respect to the solar system will be the same. > [@dimmy\_derko](#): > > What is the procedure when they are aiming one of these long-distance probes? Do they have to point it in a direction where it isn’t going to interact with any of the outer planets if they just want it to leave the solar system? Actually, the quickest way to get a space probe out of the solar system is to aim it at Jupiter, and use it’s strong gravity to perform a [gravitational slingshot](http://en.wikipedia.org/wiki/Gravitational_slingshot) maneuver. ---
**Author:** ![BrosephStallin](https://avatars.discourse-cdn.com/v4/letter/b/9fc348/32.png) [@BrosephStallin](https://boards.straightdope.com/u/BrosephStallin)\ **Post date:** [November 23, 2012, 11:21pm UTC](https://boards.straightdope.com/t/how-far-out-before-some-other-star-is-brighter-than-the-sun/641873/19 "2012-11-23T23:21:56Z")
I don’t have anything academic to contribute to this conversation, but the following simulation might give you some kind of idea of the answer to the first part of the original posted question: [The Known Universe by AMNH - YouTube](https://www.youtube.com/watch?v=17jymDn0W6U) ---
**Author:** ![dimmy\_derko](https://avatars.discourse-cdn.com/v4/letter/d/43a26b/32.png) [@dimmy\_derko](https://boards.straightdope.com/u/dimmy_derko)\ **Post date:** [November 24, 2012, 12:10am UTC](https://boards.straightdope.com/t/how-far-out-before-some-other-star-is-brighter-than-the-sun/641873/20 "2012-11-24T00:10:11Z")
Thanks for the clarification, guys. > [@BrosephStallin](#): > > I don’t have anything academic to contribute to this conversation, but the following simulation might give you some kind of idea of the answer to the first part of the original posted question: [https://www.youtube.com/watch?v=17jymDn0W6U](https://www.youtube.com/watch?v=17jymDn0W6U) At 3:58 when it is zooming back into our galaxy, over on the right there is a red blob? Any idea what that is, and why there doesn’t seem to be any of them elsewhere? [Next page](https://boards.straightdope.com/t/how-far-out-before-some-other-star-is-brighter-than-the-sun/641873.md?page=2)