Looking up in to the night sky itò??s not difficult to see why the ancient Greeks believed that all the stars in the night sky were fixed on a celestial sphere revolving around the Earth and other planets. From our view on Earth the stars appear to be at a fixed distance in the sky rotating with the seasons and never changing their positions relative to each other, rising in the east and setting in the west.Òš However, we know now that the Earth is not the centre of the cosmos but a tiny world in an expanding Universe. So from Earth how far can we see and which star is the farthest?
This is a question which does not have one simple definitive answer. We know that the Sun is the closest star to us at 150 million km (93 million miles) away. However, when it comes to the farthest star there are a few more variables that can be considered.
Stars on fixed celestial sphere surrounding the Sun and planets. (Image credit: Wikimedia.org)
Farthest star visible with the unaided eye
Under todayò??s light polluted skies the most distant star that can be seen without any great difficultly is the star Deneb. Located in the constellation of Cygnus the swan and one point of the summer triangle asterism, this star is located around 1550 light years away from Earth. However, different estimates from this distance can range between 1400- 3000 light years. Despite difficulties in pin-pointing a specific distance for this star, it is the most distant star we can see. It is also in the top twenty brightest stars visible meaning it should be relatively easy to spot in the night sky throughout the summer months from here in Northern Ireland.
Deneb one point of the Summer Triangle in the constellation of Cygnus. (Image credit: Stellarium/MRedpath.)
It is thought that under ideal dark skies conditions that the human eye can see objects up an apparent magnitude of +6 (the lower the number the brighter the object, the Sun is -26, a full moon is -12, Deneb Òšis + 1.25). There are some stars on the cusp of this visible unaided boundary which are estimated to be even further away. The Garnet Star (ÞÌ Cephei) discovered by Herschel has a magnitude of +4 and is estimated to be between 4300-9300 light years away. This star is difficult to see even under perfect conditions.
Many sources say that further still thanÒšÞÌ Cephei is the variable star V762 Cas in the constellation of Cassiopeia which has a magnitude of 5.8 (making it just visible to the unaided eye in perfect viewing conditions) and is often said to to be 16 000 light years away. However this distance is apparently based on out of date data; the 2007 Hipparcos Catalogue says it has a parallax of 1.18 milli-seconds of arc (with an uncertainty of 0.45 milli-seconds). This is equivalent to a distance of 2760 light years (but based on the large uncertainty, it could be as close as 2000 light years or as 4465 light years). ESA’s Gaea mission will probably eventually provide an accurate value for the distance to V762 Cas, but as off now it is probably not the most distant visible star (thanks to Rob Jefferies for pointing this out).
Large and Small Magellanic clouds, dwarf satellite galaxies located above the ALMA telescope. These are visible with the naked eye from the southern hemisphere. (Image credit: ESO/C. Malin.)
Farthest stellar object visible with the unaided eye
Galaxies are huge cities full of stars and the most distant of these which is still visible with the naked eye here in the northern hemisphere is the Andromeda galaxy. This is the largest galaxy in our local group of galaxies, which includes our Milky Way galaxy and more than 30 smaller ones. The Andromeda galaxy is a massive 2.5 million light years away from us and has a magnitude of +3.4, so can be seen without the need for an optical device if you have good, clear skies. This galaxy isnò??t visible from everywhere in the southern hemisphere but here you can see the Magellanic Clouds. These are satellite galaxies in orbit around the Milky Way. The Large Magellanic cloud is around 160 000 light years and has a magnitude of +0.9 so should be visible even in areas with some light pollution.
Andromeda Galaxy located 2.5 million light years away and can be seen with the naked eye. (Image credit: Wikimedia.org)
Farthest supernova viewed
Whenever a large star ends its life, it can result in a supernova explosion. The brightest most distant supernova ever viewed from the Earth without a telescope is Keplerò??s supernova.Òš This explosion was discovered by Johannes Kepler in 1604 who originally thought it was a new star in the constellation of Ophiuchus. At its brightest it had a magnitude of -2.5 and was brighter than the planets in the night sky and then it dimmed over the following weeks. ÒšIt is thought that this explosion occurred around 20 000 light years away in our Milky Way galaxy.
X-ray image of Remnants of the Kepler supernova, observed with NASAò??s Chandra X-ray Observatory.Òš (Image Credits: X-ray: NASA/CXC/NCSU/M.Burkey et al; Infrared: NASA/JPL-Caltech)
With the help of optical devices and telescopes based in space Òšlike Hubble, we can locate objects which are even further afield and not visible with the naked eye. In April 2013, Hubbleò??s Wide Field Camera 3, located one of the most distant supernovas ever discovered. It has been named SN Wilson (after President Woodrow Wilson). The supernova occurred 10 billion light years away, at the time when the Universe was still young.
Seeing even further
There are stars located even further away than the unaided eye can see. Thanks to the Hubble telescope we can not only see distant supernovas but even more distant galaxies. A galaxy is a system of stars, gas and dust held together by gravity. Over the past 10 years Hubble has been looking deep into space into the constellation of Fornax in the Southern hemisphere and has discovered thousands of galaxies.Òš The latest image assembled by images captured by Hubble is the eXtreme Deep Field (XDF). This has allowed astronomers to discover the most distant object UDFj-39546284, an early forming galaxy at over 13.2 billion light years away when the Universe was still developing into the form we see today.Òš Other space-based telescopes planned in the next few years like the James Webb Space telescope will be able to use infrared imaging to see beyond the spectrum of visible light from the Universe to hopefully discover even more distant objects.
Image Hubbleò??s eXtreme deep field image. Credit: (Image Credit: NASA; ESA; G. Illingworth, D. Magee, and P. Oesch, University of California, Santa Cruz; R. Bouwens, Leiden University; and the HUDF09 Team).
There are many distant stars many millions of light years from the Earth located in distant galaxies. However at this great distance from Earth it is difficult to measure precise distances and which single star is the farthest from us. Many of these very distant objects are invisible to the human eye and are only detectable with the use of optical aids. However, the unaided eye can still detect some amazing objects which not only allow us to see thousands of light years away but let us catch a glimpse to the beginnings of the Universe.
(Article by Martina Redpath, Education Support Officer)
what a great array of colours in the Kepler supernova, hard to believe it happened so long ago.
it is an x-ray image: those are false colors.
Prof. James Kaler, using the figure of 2,600 light years as the distance, estimated Deneb to have a diameter 200 times greater than our Sun, and about a quarter of a million times brighter in visible light. That’s why we can see something that is so extremely far away … Nice post!
Deneb’s basic stats have always been contentious. Based on recent data we have just updated our Beyond the Blue show to the values you’ve quoted.
Hi Martina,
An excellent & well presented article. However, it’s not true to say that the Andromeda Galaxy is not visible in the Southern Hemisphere – I have seen it easily from South Africa, and it’s actually visible from as far South as the Falkland Islands or New Zealand.
Terry
Hi Terry, thanks for the correction, I’ve amended the text accordingly.
Thanks a lot for the article . Its really healpful . Will stay tune for more
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Good article……and it makes me wonder so very many (hypothetical?) questions! If I were to see Deneb at this exact moment…..what year was it emitting that same light [or maybe at what time was it that our current assignment of years was]? Earth in ratio to The Milky Way would compare in what way with the ratio of one hydrogen atom to Earth? Same, more, or less? So many questions…..time and space comparisons…..other life? I won’t even open up the theology can of worms…lol…..and stuff like this makes me think back to a Steve Martin bit: “Let’s Get Small”……and the one fact I realize when I think of these things is that we are small! Good article!
If Deneb is 1550 light years away from Earth (and as the article says that is not certain), the light we see tonight left in 2013-1550 = 463 AD.
Earth is about 12800 km across, while the Milk Way is about 9.5 hundred quadrillion km across, so the Milky Way is about 75 trillion times as wide as the Earth.
A hydrogen atom is about 0.11nm across (a tiny bit over one ten-billionth of a meter), so the Earth is about 11600 trillion times as wide as a hydrogen atom.
All this is just amazing, the more u think the more questions you have and it makes u believe a powerful god is out there
Therefore god must be counterintuitive, because my logic says that the most complex things are, less complex should be its causation. And god is a hell of a complex thing.
This logic is itself counterintuitive, and is not generally applicable but descriptive of only some generative cases. For example, human beings themselves (and life generally) are products of DNA. We would not expect that it would be true that the less complex the DNA, the less complex the resulting organism. In order to have complex life, you must first encode the complex information necessary for the generation of life. Human beings require an incredibly huge amount of information before you can generate one.
Secondly, even if we accepted a general rule that the complexity of the thing is inversely proportional to the complexity of its causation, such a rule would only apply to things that have causes in the first place. God, by definition, does not have a cause. Counter intuitively, this is a requirement of causality.
To understand why, consider the simplest possible description of the universe. This simplified universe has always existed in a steady state. It would be ridiculous to ask what the cause of that universe is. The universe has no cause, rather it always has been. It is the cause of all things. We can infinitely regress the question, “What is the cause of this?”, and the answer is, “The prior moment.”, and so the answer to the question, “What is the cause of all things?”, is satisfactorily answered by, “The universe.”, and causality is never violated because there never exists anything without a cause.
This model of the universe was the leading materialist model of the universe during the 19th century. However, the 20th century brought a revolution in our material understanding. We discovered that the universe had a beginning. We could no longer accept the eternal steady state of the universe as the root cause of all things. Something external to the universe had started it. The people who first proposed that there was scientific proof the universe had a beginning were therefore initially attacked by materialists as being unscientific theists and lambasted and denigrated (in a repeat of the attacks on those that had proposed plate tectonics and catastrophic geology, and for the same reasons).
Since our model has to be scrapped, Occam’s razor asks us to propose the next simpler system. First, the universe, and secondly some minimally complex external cause which has the properties of being eternal and unchanging we’d originally proposed the universe has. God is one such candidate for the second component of the model, and in my opinion a likely one, since this universe exhibits otherwise inexplicable fine tuning.
I’m not sure your confidence in your own logic is well placed.
I dislike the rationalization that because we don’t understand what is beyond our limited sense of the small corner of our four dimensional universe that anything outside of scope must be eternal for some reason. Therefore we can scrap the scientific method that got us this far and replace it with what is essentially a human belief system of a greater, eternal and inexplicable power because it has to be in order to satisfy our species personality tick to visualize and organize. Whether you want to call it God or Multiverse or Infinity. It’s all the same concept to paint broad strokes to fill in a gap of lack of knowledge and a need to have a narrative.
However the most simple explanation that everyone will pass over because it is seemingly impossible to our mind is that the universe simply came into being from nothing. We can’t visualize nothing creating something even though particles exist and cease to exist all around us everyday. Therefore “nothing” won’t even be a candidate to satisfy Occam’s razor. Even if it is by far the most simple and best explanation we have at the moment. We will always opt for unprovable system of Infinity or God that exists in a place outside or beyond our finite dimensional universe.
(Content removed: Dear Ritchie, I am sorry but I cannot approve this comment. Not only is it off-topic, but this is not a forum for you to argue with people because you do not approve of their religious beliefs ò?? ADMIN)
I’m not very familiar with the astronomical matters, so perhaps it is a silly question, but I will make it anyway.
If the most distant oblect in the universe is 13.8 b.y. away, and this is also indicative of the age of the universe, doesn’t that mean that object was already there 13.8 b.y. ago, as we receive its light today? Then, the age of the universe should’ t be the sum of this time plus the time the object took to move to that distance from the bing bang point? (much higher that 13.8 b.y. as its speed should be much lower than the speed of light)
Thanks
That might be true in a static Universe, which is not the case for ours. We know the Universe is expanding at an increasing rate (google dark energy). With that said, the diameter of the observable Universe is 93 billion light years. How we come up with that… I have no clue :p
George Mataxas is right. Something really wrong is with all these tenths of bilions of light years’ distances… Who did really robustly measure them or at least,- did estimate them decently, even with taking into account, so called: the concept of expanding Universe? I do not feally know.
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As for me the billions and billions of light years distances and cubic empty spaces, spaced randomly with galaxies, globular clusters, stars, etc., etc. are simply some kind of veiled form of emotional play-ground for the technocrats on Earth, which can not face even the most common and basic, yet the dearest problems, i.e. many of the basic problems of humanity.
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On other hand, relatively middle close, and relatively short distances on astronomical scale did really emerged into state-of-art measurement domain. (up to several hundreds od parsecs) I must admit, cause I’m not quite dumb with all these stuffs , regarding the astronomy itself..
Hi, I am trying to track down the source of this claim that V762 Cas is the most distant naked eye star. Where does your distance come from? The 2007 revised Hipparcos parallax for this star yields a distance of 850pc – i.e. about 2500 light years.
Hi Rob, thanks for your question. Yes, there does seem to be an issue here, I am not sure where the large estimate of the distance comes from, it does seem very commonly quoted yet I cannot find where this was originally published. I’ll have the article amended.
Hello, I am a Christian who is also interested in the stars since the Bible says the “stars shall be for signs”, (Gen.1:14). I know there is much controversy over the age of the universe and whether is came about in the creation story of the Bible or by evolution. I believe in the creation story so I have no reason to believe in evolution. Google, Aquilla Fleetwood, Night Signs.
(434 words cut – sorry, this material is way off topic- ADMIN)
How can you be interested in stars (which are intrinsically basic to the age of the universe) when your belief in Biblical creation throws out most of science (particularly physics, chemistry, geology, and archaeology)?
My scientist is Yahweh! Thanks, Aquilla
I love stars. They are amazing
(Content removed: Dear Ritchie, I am sorry but I cannot approve this comment. Not only is it off-topic, but this is not a forum for you to argue with people because you do not approve of their religious beliefs ò?? ADMIN)
I have struggled with all of this. Here is my thinking now. God does not exist in a time dimension. He is aware of ALL the physical attributes of the universe. When there is an apparent conflict between what we discover in science and the words of the words of the BIBLE, it’s OK. God is aware. HE has just decided not to reveal ALL to us at this time. Be patient….in time he will.
Just looking at the sky tonight and googled how far they are from Earth. Ended up here and have to say this is the first time I’ve ever wondered or thought about stars. Nice bit of reading on the site also. Makes you think about so many things looking up at them. Is there people out there looking back at our sun loll never know. Amazing…….
it’s helpful for us.
thanks
New galaxies at 13,2 billion light years away! So if one believes in the “big bang” theory, how long has it taken from that moment for the universe to spread so far and at what speed? Seems to me that the distance in time between the first formation of our sun and the day it blows apart and obliterates the earth is simply like a blink of an eye.
Is the Universe expanding from one central point in an ever-increasing outward movement? If so will it ever be possible to determine where the starting point is?
I have a problem imaging an infinite universe.
Dear Neville, thank you for your questions.
The light from those galaxies has taken 13.2 billion years to reach us and it was travelling at the speed of light (roughly 300 000 km/s). (This seems pretty self-evident, I am sorry if I have misunderstood your question).
No this isn’t possible, to be honest there is no “starting point”. I can best try to explain it by saying that the whole Universe originated in the Big Bang and immediately started expanding, basically the Big Bang happened “everywhere”!
We all do!
I’m having trouble understanding “how to perform these large measurements”…. i.e. when we get a result “observation”….how do we calculate the distance? (I’m just learning)!~!
Dear Theolesarge, there’s good explanation at this episode of the Exposing Pseudoastronomy podcast (link).
I think it is sooo soo much to learn and we are still in the stone age! I mean open your eyes ppl we really just started using cell phones and computers if you think about it? I think other outer space beings look at us the way we look at ants… Which is rarely! We still kill each other we still smoke cigarettes drink alcohol we are pretty uneducated beings don’t you agree OPEN your eyes! Racism is here on earth like we are not all human.. It’s very crazy when you start to think about it.. It’s just the beginning when we become 1 we will become 1 big brain and we will travel space like we travel the highways today and move from planet to planer when stars die
If we don’t wipe our kind out first ????
Hi, sorry jump in in here but thought you guys may be able to help.
I was told years ago that some of the stars in the sky dont actually exist , as they burnt out years ago and that they are so far away the light is still only just reaching us. Is this correct ?
Many thanks
Dear Danny, that is a common belief but it is incorrect. Compared to human lifetimes stars live for long times (millions of years) and most of the stars we see with our unaided eyes are in the middle of their lives and within two thousand light years of the Sun, so it’s safe to say that the vast majority of them are still burning away.
please tell me which star is more away from our universe and also tell me the distance .
Hi Zeeshan, Its difficult to determine which exact single star is the most farthest in the Universe, but astronomers using the Hubble and Spitz Telescopes have discovered galaxy MACS0647-JD, which they reckon is 13.3 billion light years away. It is located between constellations Ursa Major and Minor, some of the stars within this this galaxy may some of the most distant in the Universe.
13.3 billion light years certainly is a long, long way away, considering that ONE light year represents around 9 trillion kilometers.. I am interested in knowing whether it could be possible that this galaxy – or at least one or more of its stars – no longer exists; i.e. whether it’s just that we can’t see that yet??!!
Dear POD, I am pretty sure that this galaxy still exists, after all some of the stars in our our galaxy have been dated to be 13.2 billion years old, so galaxies can can exist for a long, long time.
Hi Admin….with apologies, but “pretty sure” means you are not sure. I don’t know either, hence my question. My question was merely whether it is POSSIBLE that that galaxy no longer exists (or that a star within the galaxy no longer exists). When talking about 13.2 billion light years, a lot of births and deaths can happen in that time (including the birth of our own solar system).
Anyone else have any views? We are looking at something which existed long before we did. Could it (or some of ist components) be long gone?
Dear POD, the only processes I know of that can destroy a galaxy is when a small galaxy is absorbed by a larger one or if similar-sized galaxies merge. According to this site (link)
So it is not impossible that the galaxy in question no longer exists, though the stars in galaxies which merge or collide stay intact. Basically no one can say if that galaxy still exists in the form it was when imaged, but I am confident that some of the stars in it back then still exist somewhere in the Universe.
wow thats a long time ago
its realy long way a way from the eath its realy fasanating to me anyway its realy hard to look at the star
Who cares about all that god stuff in the way some people were mentioning it?
The stars the universe etc are a completely fascinating absolute dact by virtue that they are there, and its marvellous to know that we are (have been) part of a celestial family that is our universe.
Every thing else is pale in comparison.
(One word changed- please be polite- ADMIN)
Deneb is not the furthest star unless you are referring to the brightest stars only with apparent magnitude of 1 or less. There is so many stars out there that I am sure that many is much further than Deneb but are much fainter. I am trying to find out which star is the furthest with an apparent magnitude of 6 or even 8 , 10 . Deneb is a very remarkable star not only because of its gigantic size but also of its brightness as in absolute magntiude.. Absolute magnitude is used to measure the brightness of any star at 32 light years from you. Now Deneb has an apparent magnitude of 1.25 when viewed at 2600 light years.. if you travel closer to Deneb until you are only 32 light years from Deneb, it will be much brighter at minus 8 almost as bright as full moon. If Deneb is as close as Sirius , the brightest apparent star at 8 light year, then Deneb will definitely be as bright as our Full Moon . We will have a full moon effect from Deneb for most of the year which we would not wish to have..Deneb is a very bright white and really huge star!! We should be thankful that Deneb is so far away!!
Is the universe finite, or infinite?
If we say it is infinite, is it possible to create something infinite? Does creation require discreteness of the thing created?
If we say it is finite, what is on the other side of the limit? If we say space, what is space, is it something, is it part of the universe?
Jon you really got me on that question. Either ,Neither or both is all my feeble mind could come up with. And that’s not an answer. But thank you for getting my neurons firing almost to the point of meltdown. Keep it up , My brain needs the exercise.