# How can a 1700 year old pulsar visible? **URL:** \ **Category:** Factual Questions\ **Created:** [December 22, 2010, 8:10pm UTC](https://boards.straightdope.com/t/how-can-a-1700-year-old-pulsar-visible/565111 "2010-12-22T20:10:27Z")\ **Posts on this page:** 13\ **Page:** 1
**Author:** ![Zyanthia](https://avatars.discourse-cdn.com/v4/letter/z/d6d6ee/32.png) [@Zyanthia](https://boards.straightdope.com/u/Zyanthia)\ **Post date:** [December 22, 2010, 8:10pm UTC](https://boards.straightdope.com/t/how-can-a-1700-year-old-pulsar-visible/565111/1 "2010-12-22T20:10:27Z")
I was reading a question about simulation being possible that had a link to a Star Trek article [that linked to an article on a pulsar](http://en.wikipedia.org/wiki/PSR_B1509-58) that states: “PSR B1509-58 is a pulsar approximately 17,000 light-years away in the constellation of Circinus discovered by the Einstein X-Ray Observatory in 1982. It is approximately 1700 years old and sits in a nebula that spans about 150 light years.” If the object is only 1700 years old and 17,000 light years away, how can we see it already? Shouldn’t we have to wait another 15,300 years before the light is visible on Earth? Or do they mean that what we are seeing is only 1,700 years old but the pulsar is actually 18,700 years old now? ---
**Author:** ![Squink](https://avatars.discourse-cdn.com/v4/letter/s/b5e925/32.png) [@Squink](https://boards.straightdope.com/u/Squink)\ **Post date:** [December 22, 2010, 8:11pm UTC](https://boards.straightdope.com/t/how-can-a-1700-year-old-pulsar-visible/565111/2 "2010-12-22T20:11:53Z")
That last is exactly what they mean. ---
**Author:** ![Zyanthia](https://avatars.discourse-cdn.com/v4/letter/z/d6d6ee/32.png) [@Zyanthia](https://boards.straightdope.com/u/Zyanthia)\ **Post date:** [December 22, 2010, 8:31pm UTC](https://boards.straightdope.com/t/how-can-a-1700-year-old-pulsar-visible/565111/3 "2010-12-22T20:31:31Z")
Thank you! I was getting myself confused to trying to figure it out 🙂 ---
**Author:** ![pericynthion](https://avatars.discourse-cdn.com/v4/letter/p/85e7bf/32.png) [@pericynthion](https://boards.straightdope.com/u/pericynthion)\ **Post date:** [December 23, 2010, 7:04am UTC](https://boards.straightdope.com/t/how-can-a-1700-year-old-pulsar-visible/565111/4 "2010-12-23T07:04:50Z")
In a very real sense, as far as we are concerned it is only 1700 years old: [Relativity of simultaneity - Wikipedia](http://en.wikipedia.org/wiki/Relativity_of_simultaneity) ---
**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:** [December 23, 2010, 7:54am UTC](https://boards.straightdope.com/t/how-can-a-1700-year-old-pulsar-visible/565111/5 "2010-12-23T07:54:03Z")
> [@pericynthion](#): > > In a very real sense, as far as we are concerned it is only 1700 years old … This seems the logical usage of time in such contexts; don’t astronomers say “with our radio telescopes we can see the universe when it was only 380,000 years old”? Otherwise, given my desire to see an interesting spectacle in my lifetime, I’d not ask whether Betelgeuse, which [may be undergoing](http://astronomynow.com/news/n0907/29betel/) a [state change](http://www.astronomynow.com/0906010RedgiantstarBetelgeuseisshrinking.html) right now, will explode soon. I’d ask: **Has Betelgeuse already exploded?** 😃 ---
**Author:** ![Mangetout](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mangetout/32/19_2.png) [@Mangetout](https://boards.straightdope.com/u/Mangetout)\ **Post date:** [December 23, 2010, 8:02am UTC](https://boards.straightdope.com/t/how-can-a-1700-year-old-pulsar-visible/565111/6 "2010-12-23T08:02:15Z")
I accidentally a 1700 year old pulsar. ---
**Author:** ![Qadgop\_the\_Mercotan](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/qadgop_the_mercotan/32/83_2.png) [@Qadgop\_the\_Mercotan](https://boards.straightdope.com/u/Qadgop_the_Mercotan)\ **Post date:** [December 23, 2010, 1:46pm UTC](https://boards.straightdope.com/t/how-can-a-1700-year-old-pulsar-visible/565111/7 "2010-12-23T13:46:01Z")
> [@septimus](#): > > **Has Betelgeuse already exploded?** And if it did, was it a consequence of the Great Collapsing Hrung disaster? 😕 ---
**Author:** ![Gyrate](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/gyrate/32/3588_2.png) [@Gyrate](https://boards.straightdope.com/u/Gyrate)\ **Post date:** [December 23, 2010, 1:58pm UTC](https://boards.straightdope.com/t/how-can-a-1700-year-old-pulsar-visible/565111/8 "2010-12-23T13:58:19Z")
> [@Mangetout](#): > > I accidentally a 1700 year old pulsar. You may have thought you a pulsar but you actually a burning dog. ---
**Author:** ![njtt](https://avatars.discourse-cdn.com/v4/letter/n/ecd19e/32.png) [@njtt](https://boards.straightdope.com/u/njtt)\ **Post date:** [December 23, 2010, 2:48pm UTC](https://boards.straightdope.com/t/how-can-a-1700-year-old-pulsar-visible/565111/9 "2010-12-23T14:48:47Z")
> [@Zyanthia](#): > > “PSR B1509-58 is a pulsar approximately 17,000 light-years away in the constellation of Circinus discovered by the Einstein X-Ray Observatory in 1982. It is approximately 1700 years old and sits in a nebula that spans about 150 light years.” I think that by far the most likely explanation is a typographical error. They mean that because the pulsar is 17,000 light years away, what we are seeing now is something that existed 17,000 years ago (gee whiz!) - but somehow a zero and a comma got dropped from the second number. ---
**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:** [December 23, 2010, 4:56pm UTC](https://boards.straightdope.com/t/how-can-a-1700-year-old-pulsar-visible/565111/10 "2010-12-23T16:56:14Z")
> [@Qadgop\_the\_Mercotan](#): > > And if it did, was it a consequence of the Great Collapsing Hrung disaster? 😕 Will I be branded an uncultured Rip Van Winkle from the 19th century if I admit I had to Google this? And Googling, I find a large number of chapters all on-line beginning > [@](#): > > The house stood on a slight rise just on the edge of the village… The only person for whom the house was in any way special was Arthur Dent, and that was only because it happened to be the one he lived in… Looks like a fun read! But I’m already [del]wasting all available free time on the Internet[/DEL] working industriously a full 24-7. :mad: Mr. Qadgop: Please report directly to BBQ Pit! ---
**Author:** ![Qadgop\_the\_Mercotan](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/qadgop_the_mercotan/32/83_2.png) [@Qadgop\_the\_Mercotan](https://boards.straightdope.com/u/Qadgop_the_Mercotan)\ **Post date:** [December 23, 2010, 5:21pm UTC](https://boards.straightdope.com/t/how-can-a-1700-year-old-pulsar-visible/565111/11 "2010-12-23T17:21:44Z")
> [@septimus](#): > > Mr. Qadgop: Please report directly to BBQ Pit! That’s Dr. Qadgop to you, **septi**! And if we’re meeting in the pit, you’d better know where your towel is! And from hereon, you shall be known as **Ix**! [sub]Ix translates as “Boy who does not know what a Hrung is, nor why it should choose to collapse on Betelgeuse 7”.[/sub] 😃 ---
**Author:** ![snailboy](https://avatars.discourse-cdn.com/v4/letter/s/97f17d/32.png) [@snailboy](https://boards.straightdope.com/u/snailboy)\ **Post date:** [December 23, 2010, 5:32pm UTC](https://boards.straightdope.com/t/how-can-a-1700-year-old-pulsar-visible/565111/12 "2010-12-23T17:32:31Z")
> [@pericynthion](#): > > In a very real sense, as far as we are concerned it is only 1700 years old: [Relativity of simultaneity - Wikipedia](http://en.wikipedia.org/wiki/Relativity_of_simultaneity) I don’t believe that the relativity of simultaneity states that the time it took for light to reach an observer shouldn’t be considered when calculating the time it occurred, simply that even when this is considered, two observers may see an event as happening at different times relative to other events. ---
**Author:** ![DHMO](https://avatars.discourse-cdn.com/v4/letter/d/ecc23a/32.png) [@DHMO](https://boards.straightdope.com/u/DHMO)\ **Post date:** [December 25, 2010, 11:25am UTC](https://boards.straightdope.com/t/how-can-a-1700-year-old-pulsar-visible/565111/13 "2010-12-25T11:25:24Z")
Part of the problem stems from the attempt to determine what “Reality” is. We can see the Pulsar, and measure its distance from us as we would any other cosmic object—in the instant case, 17 thousand light-years. From the debris and gasses surrounding the Pulsar, we can estimate that the catacalysm which created it occured about 1700 years ago. While the light bringing us of this information has been in transit for 17,000 years, in a very real sense, what we are seeing today is what it looked like 17,000 years ago! What the Pulsar is doing, and how it looks, _right now_, has no meaning. There is absolutely no contradiction in the OP, unless one tries to frame reality in the terms that the explosion _really_ occured at some point in the past, which we somehow are aware of, even though no light or other information has had time to reach us yet, and we must, perforce, wait another 15,300 years for the information-bearing light to reach us.