Are non-Muslims going to heaven according to Islam?

Are non-Muslims going to heaven according to Islam?
Will an otherwise sinless non-Muslim ever go to heaven?
Or are non-Muslims doomed to eternal damnation?
Is the Quran clear on this?

Note: First of all, I want to make it very clear that Allaah (The Almighty) is never unjust, not even in the least degree (ch-4, Verse Number- 40 of the Glorious Qura'n).
I myself a Muslim, sometimes used to wonder that I have lots of non-Muslim friends, will they all go to HELL FOREVER........???

Well the answer is right here.....

It is part of the justice of Allaah (The Almighty) that He does not punish any people until He has first sent a warning to them and unless there is evidence against them. Allaah does not treat anybody unfairly. Allaah says (interpretation of the meaning): “… And We never punish until We have sent a Messenger (to give warning).” [al-Israa’ 17:15].

In his tafseer (commentary) on this aayah, Ibn Katheer (A great scholar of Islam) (may Allaah have mercy on him) said: “These words, ‘…And We never punish until We have sent a Messenger (to give warning)’ tell us of the justice of Allaah, may He be exalted, and that He does not punish anyone until after He has established evidence against him by sending a Messenger to him. This is like the aayat (interpretation of the meaning): ‘… Every time a group is cast therein [into Hell], its keeper will ask, “Did no warner come to you?” They will say, “Yes indeed; a warner did come to us, but we belied him and said: ‘Allaah never sent down anything (of revelation), you are only in great error.’”’ [al-Mulk 67:8] and: ‘And those who disbelieved will be driven to Hell in groups, till, when they reach it, the gates thereof will be opened (suddenly like a prison at the arrival of its prisoners). And its keepers will say, “Did not the Messengers come to you from yourselves, - reciting to you the Verses of your Lord, and warning you of the Meeting of this Day of yours?” They will say: “Yes, but the Word of torment has been justified against the disbelievers!”’ [al-Zumar 39:71]…”

A person who has never heard of Islam or the Prophet SAWS (peace and blessings of Allaah be upon him), and who has never heard the message in its correct and true form, will not be punished by Allaah if he dies in a state of kufr (disbelief). If it were asked what his fate will be, the answer will be that Allaah will test him on the Day of Resurrection: if he obeys, he will enter Paradise and if he disobeys he will enter Hell. The evidence (daleel) for this is the hadeeth of al-Aswad ibn Saree’, who reported that the Prophet of Allaah SAWS (peace and blessings of Allaah be upon him) said: “There are four (who will protest) to Allaah on the Day of Resurrection: the deaf man who never heard anything, the insane man, the very old man, and the man who died during the fatrah (the interval between the time of ‘Eesaa (Jesus, upon whom be peace) and the time of Muhammad SAWS (peace and blessings of Allaah be upon him)). The deaf man will say, ‘O Lord, Islam came but I never heard anything.’ The insane man will say, ‘O Lord, Islam came but the children ran after me and threw stones at me.’ The very old man will say, ‘O Lord, Islam came but I did not understand anything.’ The man who died during the fatrah will say, ‘O Lord, no Messenger from You came to me.’ He will accept their promises of obedience, then word will be sent to them to enter the Fire. By the One in Whose hand is the soul of Muhammad, if they enter it, it will be cool and safe for them.”

According to another report, he said: “Whoever enters it, it will be cool and safe for him, and whoever does not enter it will be dragged to it.” (The hadeeth (Teaching of Our beloved Prophet Muhammed Peace and blessings of Allaah be upon Him.) was reported by Imaam Ahmad and Ibn Hibbaan, and deemed saheeh by al-Albaani, Saheeh al-Jaami’, 881).

Everyone who hears the message of Islam in a sound and correct form (and rejects it), will have evidence against him. Whoever dies without having heard the message, or having heard it in a distorted form, then his case is in the hands of Allaah. Allaah knows best about His creation, and He will never treat anyone unfairly. And Allaah is All-Seer of His slaves. (source: The fate of kuffaar who did not hear the message of Islam).

A Serious Note: A serious advice to the people that If you are convinced that Islam is the truth, please do not delay it to accept the truth. No one is aware of his/her appointment with their Lord (i.e. no one is aware of the time of death except the Lord), so please prepare for it. Just do some research about the Glorious Qura'an, and I promise you that you will be dazzled to see how many scientific miracles are present in the Qura'an. Qura'an is the only religious book on the face of the earth that is free from any modification, errors.
It is the only book on the face of the earth that is completely memorised (word by word) by millions and read by billions.

Just to give you a glimpse of Qura'an:

Did you know that Expansion of the universe is mentioned in the Glorious Qura'an, which science finds just recently? (Qur'an, 51:47)

Did you know that complete Human embryo development cycle is mentioned in the Glorious Qura'an? (Quran, 23:12-14)

Did you know that every living thing is made up of water is mentioned in the Qura'an? (Qur'an, 24:45) , (Qur'an, 21:30), (Qur'an, 25:54)

Did you know that theory of Big-Bang which explains the creation of the universe is mentioned in the Qura'an? (Quran 21:30)

Did you know that Shape of the earth is spherical is mentioned in the Qura'an?(Quran 79:30)

Did you know that ant lives in the community is mentioned in the Qura'an which scientist used to reject centuries ago, but now they accept it? (Qur'an, 6:38) ,(Qur'an, 27:18)

Please sincerely ask yourself a question, who could have mentioned all of this and much more than this in the Glorious Qura'an?

I can go on and on, giving only the scientific miracles, forget about language miracle, numerology miracles.

Qura'an is not a Book of Science, rather it's a Book of Signs (i.e. to recognize that our Lord is One without a second and We are created for a purpose).

Peace...