يقول سبحانه وتعالى:
(فَلَا أُقْسِمُ بِالْخُنَّسِ * الْجَوَارِ الْكُنَّسِ * وَاللَّيْلِ إِذَا عَسْعَسَ) (التكوير س 81 ، آية 15-17)
(So verily I call to witness those (Stars and galaxies) that hide and recede. Constantly moving, and accreating. And the Night as it gets Darker) (S. 81; V. 15-17)
رَوَى مُسْلِم فِي صَحِيحه وَالنَّسَائِيّ فِي تَفْسِيره عِنْد هَذِهِ الْآيَة مِنْ حَدِيث مِسْعَر بْن كِدَام عَنْ الْوَلِيد بْن سَرِيع عَنْ عَمْرو بْن حُرَيْث قَالَ : صَلَّيْت خَلْف النَّبِيّ صَلَّى اللَّه عَلَيْهِ وَسَلَّمَ الصُّبْح فَسَمِعْته يَقْرَأ " فَلَا أُقْسِم بِالْخُنَّسِ الْجَوَار الْكُنَّس وَاللَّيْل إِذَا عَسْعَسَ وَالصُّبْح إِذَا تَنَفَّسَ " وَرَوَاهُ النَّسَائِيّ عَنْ بُنْدَار عَنْ غُنْدَر عَنْ شُعْبَة عَنْ الْحَجَّاج بْن عَاصِم عَنْ أَبِي الْأَسْوَد عَنْ عَمْرو بْن حُرَيْث بِهِ نَحْوه قَالَ اِبْن أَبِي حَاتِم وَابْن جَرِير مِنْ طَرِيق الثَّوْرِيّ عَنْ أَبِي إِسْحَاق عَنْ رَجُل مِنْ مُرَاد عَنْ عَلِيّ " فَلَا أُقْسِم بِالْخُنَّسِ الْجَوَار الْكُنَّس " قَالَ هِيَ النُّجُوم تَخْنَس بِالنَّهَارِ وَتَظْهَر بِاللَّيْلِ وَقَالَ اِبْن جَرِير حَدَّثَنَا اِبْن الْمُثَنَّى حَدَّثَنَا مُحَمَّد بْن جَعْفَر حَدَّثَنَا شُعْبَة عَنْ سِمَاك بْن حَرْب سَمِعْت خَالِد بْن عَرْعَرَة سَمِعْت عَلِيًّا وَسُئِلَ عَنْ " لَا أُقْسِم بِالْخُنَّسِ الْجَوَار الْكُنَّس " فَقَالَ هِيَ النُّجُوم تَخْنَس بِالنَّهَارِ وَتَكْنُس بِاللَّيْلِ وَحَدَّثَنَا أَبُو كُرَيْب حَدَّثَنَا وَكِيع عَنْ إِسْرَائِيل عَنْ سِمَاك عَنْ خَالِد عَنْ عَلِيّ قَالَ هِيَ النُّجُوم وَهَذَا إِسْنَاد جَيِّد صَحِيح إِلَى خَالِد بْن عَرْعَرَة وَهُوَ السَّهْمِيّ الْكُوفِيّ (الراوي: خالد بن عرعرة ، خلاصة الدرجة: إسناده جيد ، المحدث: ابن كثير، المصدر: تفسير القرآن ، الصفحة أو الرقم 8/359 ).
هذا وإنّ المواقع الآنيّة الحقيقية للنجوم لا يعلمها إلاّ اللّه. وتمّ توضيح ذلك في بحث منشور عنوانه بعض أسرار القسم الرّباني بمواقع النجوم (). ناقش هذا البحث القليل من أسرار كثيرة وعظيمة ينطوي عليها القسم الرّباني بمواقع النجوم؛ وذلك من خلال ذكر بعض التَّعقيدات الفيزيائيّة الّتي تكتنف حساب أبعاد النُّجوم عن كرتنا الأرضيّة. وتبيّن أنَّ العلم الدّقيق بمواقع النّجوم ومنازلها لا يحيطُ به إلاّ الخالق سبحانه وتعالى. ويترتّبُ على ذلك عدم معرفة منازلها في السّماء، وعدم تحديد مطالعها ومشارقها بشكلٍ دقيق. وبالتالي أيّاً كان المقصود بمواقع النّجوم: منازلها ومواقعها في السّماء، مطالعها ومشارقها، انكدارها يوم القيامة أو انتثارها، نجوم القرآن، فأيُّ شيءٍ من ذلك لا يحيطُ بعلمه إلاّ الخالق سبحانه وتعالى (بحث : أسرار القسم الرّباني بمواقع النجوم).
(وَاللَّيْلِ إِذَا عَسْعَسَ)
فِيهِ قَوْلَانِ " أَحَدهمَا " إِقْبَاله بِظَلَامِهِ قَالَ مُجَاهِد أَظْلَمَ وَقَالَ سَعِيد بْن جُبَيْر إِذَا نَشَأَ وَقَالَ الْحَسَن الْبَصْرِيّ إِذَا غَشِيَ النَّاس وَكَذَا قَالَ عَطِيَّة الْعَوْفِيّ وَقَالَ عَلِيّ بْن أَبِي طَلْحَة وَالْعَوْفِيّ عَنْ اِبْن عَبَّاس " إِذَا عَسْعَسَ " إِذَا أَدْبَرَ وَكَذَا قَالَ مُجَاهِد وَقَتَادَة وَالضَّحَّاك وَكَذَا قَالَ زَيْد بْن أَسْلَم وَابْنه عَبْد الرَّحْمَن " إِذَا عَسْعَسَ " أَيْ إِذَا ذَهَبَ فَتَوَلَّى وَقَالَ أَبُو دَاوُد الطَّيَالِسِيّ حَدَّثَنَا شُعْبَة عَنْ عَمْرو بْن مُرَّة عَنْ أَبِي الْبُحْتُرِيّ سَمِعَ أَبَا عَبْد الرَّحْمَن السُّلَمِيّ قَالَ : خَرَجَ عَلَيْنَا عَلِيّ رَضِيَ اللَّه عَنْهُ حِين ثَوَّبَ الْمُثَوِّب بِصَلَاةِ الصُّبْح فَقَالَ : أَيْنَ السَّائِلُونَ عَنْ الْوِتْر " وَاللَّيْل إِذَا عَسْعَسَ وَالصُّبْح إِذَا تَنَفَّسَ " هَذَا حِين أَدْبَرَ حَسَن وَقَدْ اِخْتَارَ اِبْن جَرِير أَنَّ الْمُرَاد بِقَوْلِهِ " إِذَا عَسْعَسَ " إِذَا أَدْبَرَ قَالَ لِقَوْلِهِ " وَالصُّبْح إِذَا تَنَفَّسَ " أَيْ أَضَاءَ وَاسْتَشْهَدَ بِقَوْلِ الشَّاعِر أَيْضًا : حَتَّى إِذَا الصُّبْح لَهُ تَنَفُّسًا وَانْجَابَ عَنْهَا لَيْلهَا وَعَسْعَسًا أَيْ أَدْبَرَ وَعِنْدِي أَنَّ الْمُرَاد بِقَوْلِهِ " إِذَا عَسْعَسَ " إِذَا أَقْبَلَ وَإِنْ كَانَ يَصِحّ اِسْتِعْمَاله فِي الْإِدْبَار أَيْضًا لَكِنَّ الْإِقْبَال هَاهُنَا أَنْسَب كَأَنَّهُ أَقْسَمَ بِاللَّيْلِ وَظَلَامه إِذَا أَقْبَلَ وَبِالْفَجْرِ وَضِيَائِهِ إِذَا أَشْرَقَ كَمَا قَالَ تَعَالَى " وَاللَّيْل إِذَا يَغْشَى وَالنَّهَار إِذَا تَجَلَّى " وَقَالَ تَعَالَى " وَالضُّحَى وَاللَّيْل إِذَا سَجَى " وَقَالَ تَعَالَى " فَالِق الْإِصْبَاح وَجَعَلَ اللَّيْل سَكَنًا " وَغَيْر ذَلِكَ مِنْ الْآيَات وَقَالَ كَثِير مِنْ عُلَمَاء الْأُصُول إِنَّ لَفْظَة عَسْعَسدَ تُسْتَعْمَل فِي الْإِقْبَال وَالْإِدْبَار عَلَى وَجْه الِاشْتِرَاك فَعَلَى هَذَا يَصِحّ أَنْ يُرَاد كُلّ مِنْهُمَا وَاَللَّه أَعْلَم . قَالَ اِبْن جَرِير وَكَانَ بَعْض أَهْل الْمَعْرِفَة بِكَلَامِ الْعَرَب يَزْعُم أَنَّ عَسْعَسَ دَنَا مِنْ أَوَّله وَأَظْلَمَ وَقَالَ الْفَرَّاء كَانَ أَبُو الْبِلَاد النَّحْوِيّ يُنْشِد بَيْتًا : عَسْعَسَ حَتَّى لَوْ يَشَا ادَّنَى كَانَ لَهُ مِنْ ضَوْئِهِ مِقْبَس يُرِيد لَوْ يَشَاء إِذْ دَنَا أَدْغَمَ الذَّال فِي الدَّال قَالَ الْفَرَّاء وَكَانُوا يَزْعُمُونَ أَنَّ هَذَا الْبَيْت مَصْنُوع.
The rest of the article is just to illustrate two aspects of the stars and galaxies: Hiding and receding.
Astronomers know that normal matter, the stuff of stars and planets, makes up only 5% of the observable universe. Dark matter accounts for a further 25%, with the remaining 70% being the even more exotic dark energy, which drives the expansion of the cosmos.
Dark energy makes up approximately 70% of the universe and appears to be associated with the vacuum in space. It is distributed evenly throughout the universe, not only in space but also in time – in other words, its effect is not diluted as the universe expands. The even distribution means that dark energy does not have any local gravitational effects, but rather a global effect on the universe as a whole. This leads to a repulsive force, which tends to accelerate the expansion of the universe. The rate of expansion and its acceleration can be measured by observations based on the Hubble law. These measurements, together with other scientific data, have confirmed the existence of dark energy and provide an estimate of just how much of it exists.
تشكل الطاقة المظلمة ما يقرب من 70% من مكونات الكون، ويبدو أنها ترتبط مع الفراغ الكوني. يتم توزيعها بالتساوي في جميع أنحاء الكون، وليس فقط في الفضاء ولكن أيضا في الزمان . وبعبارة أخرى، لا يضعف تأثيرها مع توسع الكون. التوزيع المنتظم للطاقة المظلمة يعني أنه ليس لديها أي آثار جاذبية محلية، وإنما لها تأثير على نطاق الكون ككل. وتأثيرها يبدو كقوة طاردة، أو قوّة تنافر تعمل على تسريع توسع الكون. ويمكن قياس معدل التوسع والتسارع الكوني من خلال الأرصاد واستنادا إلى قانون هابل. هذه القياسات، جنبا إلى جنب مع بيانات علمية أخرى، أكدت وجود الطاقة المظلمة وحدّدت مقدارها.
Dark energy is persistent, which impart a constant impulse to the expansion of the universe, which makes galaxies accelerate away. Dark energy doesn’t dilute away as the universe expands.
الطاقة المظلمة هي ثابتة، وهي التي تبذل شغلاً وبدفع (impulse) ثابت يسهم في توسع الكون، الأمر الذي يجعل المجرات تتباعد وبتسارع. الطاقة المظلمة لا تتناقص مع توسّع الكون.
Dark matter and Dark energy are referred to by the verses:
- (وَالسَّمَاءَ بَنَيْنَاهَا بِأَيْيدٍ وَإِنَّا لَمُوسِعُونَ * وَالأرْضَ فَرَشْنَاهَا فَنِعْمَ الْمَاهِدُونَ * وَمِنْ كُلِّ شَيْءٍ خَلَقْنَا زَوْجَيْنِ لَعَلَّكُمْ تَذَكَّرُونَ) ] 49-47 الذّاريات[.
" We have built The Sama - Firmament - with might, We indeed Have vast power; to create the vastness of Space and continue to expand it * And We have spread out Ardh - Ground; interior or lower part of the Universe; the dark matter holding the galaxies -: How excellently We do spread out * And of everything We have created pairs: that ye may receive instruction " (Surah No. 51, verse 47- 49).
Examples of such pairs are: Dark matter (Sama – Firmament -, and Ardh - Ground; interior or lower part of the Universe; the dark matter holding the galaxies) and Matter. Another pair is Dark energy and energy.
متوسط رقم الآيتين (47.5) يساوي القيمة الحاليّة لمتوسط نسب الطاقة المظلمة والمادّة المظلمة:
The average value for the numbers of these two verses, 47.5, is equal to the present value of the average percentages of dark matter and dark energy:
(23% + 72%)/2= 47.5%
 "Say: Is it that ye deny Him Who created the Ardh (lower - interior - part of the early Universe; large scale structure of dark matter) in two Days (periods)? and do ye join equals with Him? He is the Lord of (all) the Worlds."  He set on the (Ardh). Like Mountains standing firm, above it, and bestowed blessings on the Ardh, and measured therein all things to give them nourishment in due proportion, in precisely four Days (periods) for those who seek knowledge, and also in accordance with (the needs of) those who seek (sustenance). " (Surah 41, Verses 9-10).
(فَلَا أُقْسِمُ بِمَا تُبْصِرُونَ * وَمَا لَا تُبْصِرُونَ) (الحاقة س 69، الآيتان 38-39)
"Furthermore I swear by what ye see * And what ye see not." (S. 69 V 38-39)
- (سُبْحَانَ الَّذِي خَلَقَ الْأَزْوَاجَ كُلَّهَا مِمَّا تُنْبِتُ الْأَرْضُ وَمِنْ أَنْفُسِهِمْ وَمِمَّا لَا يَعْلَمُونَ * وَآيَةٌ لَهُمُ اللَّيْلُ نَسْلَخُ مِنْهُ النَّهَارَ فَإِذَا هُمْ مُظْلِمُونَ) [يس 36-37]
(Glory to Allah, Who created in pairs all things that the earth produces, as well as their own (human) kind and (other) things of which they have no knowledge. * And a Sign for them is the Night: We withdraw therefrom the Day, and behold they are plunged in darkness.) (S. 36, V. 36-37)
- (والَّذِي خَلَقَ الْأَزْوَاجَ كُلَّهَا) [الزّخرف 12]
 That has created pairs in all things, and has made for you ships and cattle on which ye ride,) (S. 43, V. 12)
- (وَمِنْ كُلِّ شَيْءٍ خَلَقْنَا زَوْجَيْنِ لَعَلَّكُمْ تَذَكَّرُونَ) [الذّاريات 49].
 And of everything We have created pairs: that ye may receive instruction. ) (S. 51, V. 49)
(وَالسَّمَاءَ بَنَيْنَاهَا بِأَيْيدٍ وَإِنَّا لَمُوسِعُونَ)
(أَأَنْتُمْ أَشَدُّ خَلْقًا أَمْ السَّمَاءُ بَنَاهَا * رَفَعَ سَمْكَهَا فَسَوَّاهَا) [النّازعات 27-28]
 What! Are ye the more difficult to create or the Samaa (Firmaments) (above)? (Allah) hath constructed it:  On high hath He raised its canopy, and He hath given it order and perfection. ) (S. 79, V. 27)
(وَالسَّمَاءَ رَفَعَهَا وَوَضَعَ الْمِيزَانَ) (الرحمن 7)
(And the Firmament has He raised high, and He has set up the Balance (of Justice),) (S. 55, V. 7)
(اللَّهُ الَّذِي رَفَعَ السَّمَاوَاتِ بِغَيْرِ عَمَدٍ تَرَوْنَهَا ثُمَّ اسْتَوَى عَلَى الْعَرْشِ وَسَخَّرَ الشَّمْسَ وَالْقَمَرَ كُلٌّ يَجْرِي لِأَجَلٍ مُسَمًّى يُدَبِّرُ الْأَمْرَ يُفَصِّلُ الْآيَاتِ لَعَلَّكُمْ بِلِقَاءِ رَبِّكُمْ تُوقِنُونَ) (الرعد 2)
(Allah is He Who raised the Samawat – Firmaments - without any pillars that ye can see; then He established Himself on the Throne (of Authority); He has subjected the sun and the moon (to His Law)! Each one runs (its course) for a term appointed. He doth regulate all affairs, explaining the Signs in detail, that ye may believe with certainty in the meeting with your Lord.) (S. 13, V. 2)
يُخْبِر اللَّه تَعَالَى عَنْ كَمَالِ قُدْرَته وَعَظِيم سُلْطَانه أَنَّهُ الَّذِي بِإِذْنِهِ وَأَمْره رَفَعَ السَّمَوَات بِغَيْرِ عَمَد بَلْ بِإِذْنِهِ وَأَمْره وَتَسْخِيره رَفَعَهَا عَنْ الْأَرْض بُعْدًا لَا تُنَال (بن كثير).
(خَلَقَ السَّمَاوَاتِ بِغَيْرِ عَمَدٍ تَرَوْنَهَا وَأَلْقَى فِي الْأَرْضِ رَوَاسِيَ أَنْ تَمِيدَ بِكُمْ وَبَثَّ فِيهَا مِنْ كُلِّ دَابَّةٍ وَأَنْزَلْنَا مِنَ السَّمَاءِ مَاءً فَأَنْبَتْنَا فِيهَا مِنْ كُلِّ زَوْجٍ كَرِيمٍ) (لقمان 10)
(He created the Samawat – Firmaments - without any pillars that ye can see; He set on the earth mountains standing firm, lest it should shake with you; and He scattered through it beasts of all kinds. We send down rain from the sky, and produce on the earth every kind of noble creature, in pairs.) (S. 31, V. 10)
يُبَيِّن سُبْحَانه بِهَذَا قُدْرَته الْعَظِيمَة عَلَى خَلْق السَّمَاوَات وَالْأَرْض وَمَا فِيهِمَا وَمَا بَيْنهمَا فَقَالَ تَعَالَى " خَلَقَ السَّمَاوَات بِغَيْرِ عَمَد " قَالَ الْحَسَن وَقَتَادَة لَيْسَ لَهَا عَمَد مَرْئِيَّة وَلَا غَيْر مَرْئِيَّة . وَقَالَ اِبْن عَبَّاس وَعِكْرِمَة وَمُجَاهِد لَهَا عَمَد لَا تَرَوْنَهَا (بن كثير).
يوسّع الله سبحانه وتعالى بناء السّماء، فيتعاظم الفراغ في الكون، وتزداد الطاقة المظلمة. فينتج عنه فرش ومهاد الأرضين (المادّة المظلمة التي تحضن جاذبيّا مجرّات الكون). وبالتالي تتباعد المسافات بين المجرّات.
ALLAH (GOD) have built The Sama - Firmament - with might, He indeed Have vast power; to create its vastness and continue to expand it, and on high hath He raised its canopy. This gives rise to the so called negative pressure (Dark energy); since Sama is a solid construction (roof) with no cracks, and completely covers and surrounds the universe. This is clearly indicated by many verses.
Before the first radio observations were made in the 1930s, all that was known about the Universe came from observations in the visible part of the spectrum. Scientists were not even aware of the “hidden Universe” beyond the boundaries of the visible. For many years a kind of narrow-sightedness existed amongst astronomers that could perhaps be called “visible-light chauvinism” — an exaggerated focus on the processes that are visible to our eyes. For all that the visible part of the spectrum is very important and information-rich, it is just a tiny part of the full story.
The visible wavelengths are called “visible” because they are the wavelengths that we can see naturally. Natural selection has forged a connection between our eyes and the Sun’s light, most of which emerges in the visible range. Our eyes are biologically tuned to be sensitive where the Sun is brightest. Coincidentally, like the Sun — which is a perfectly ordinary G dwarf star — many other stars emit a large part, or even the majority, of their light in the visible range.
This section is an outline of the book titled: HIDDEN UNIVERSE (http://www.hiddenuniverse.org/). The following is a brief summary of the book; which is more or less an explanation or a light shed on the verse:
(فَلَا أُقْسِمُ بِالْخُنَّسِ * الْجَوَارِي الْكُنَّسِ * وَاللَّيْلِ إِذَا عَسْعَسَ) (التكوير س 81 ، آية 15-17)
(So verily I call to witness those (Stars and galaxies) that hide and recede. Constantly moving, and accreating. And the Night as it gets Darker) (S. 81; V. 15-17)
Until 400 years ago, when Galileo first turned his telescope towards the heavens, our perception of the Universe was limited by our eyes and the thoughts and ideas arising from what we saw. The huge leap in capability that even such a simple instrument could realize set us on the path of creating ever more powerful instruments to satisfy our voracious appetite for knowledge.
Nonetheless, until the mid-20th century our view of the Universe was limited almost entirely to the narrow band of light that could penetrate the Earth’s atmosphere and was visible either to our eyes or to sensitive photographic plates loaded at the focus of increasingly large telescopes. With these resources alone, the discoveries were still stupendous: the mapping of our Solar System, the identification of the mechanism that makes stars shine and determines how long they live, the realisation that there are a multitude of galaxies like our own Milky Way and that they constitute an expanding Universe. The profound revolution in physics during the first half of the century brought with it the understanding of how light is emitted and how to read the subtle messages it carries concerning the physical state and chemical composition of stars and nebulae.
Stimulated by the development of radar for military use, the first major expansion of our view was the result of the development of radio astronomy, leading to the realisation that the Universe could look very different to us when seen through new “eyes” tuned to a different type of radiation.
The launch of Sputnik in 1957 paved the way for astronomy’s escape from the absorbing and distorting effects of the Earth’s atmosphere. With truly clear skies, generations of exploratory spacecraft and orbiting observatories have produced a wondrous and often breathtakingly beautiful view of a Universe whose richness could not have been imagined. A string of new discoveries has come from this fleet of new space-based instruments and observatories, and each new insight has been firmly placed within the existing framework of understanding by astronomers. Meanwhile the impressive arsenal of today’s ground-based facilities bears witness to the continuing success of the modern large and highly evolved versions of the traditional telescope.
This book will enable you to peer through these exotic new telescopes and see some of the more spectacular images that have become the icons of modern astronomy. By expanding your vision beyond the visible into an array of “colours” that span the full spectrum of light, you will be able to gain a more complete picture of the Universe than has ever been possible before. These images are truly a legacy to be appreciated by everyone. Obtained using facilities built by governments and public institutions across the globe, they allow us all to better understand our place in a spectacular Universe, once hidden, but now revealed.
This book is divided into nine chapters dealing with various aspects of the unseen Universe. The first three discuss the way we perceive the Universe, using our eyes and with telescopes on the ground and in space. The next five chapters each discuss a wavelength band, starting with the most familiar, visible light, and then moving outwards on each side of the spectrum into the less familiar: infrared, ultraviolet, radio/microwaves and X-rays/gamma rays. In the final chapter we attempt to gather the individual threads of the story into one, somewhat coherent, view of the totality of the multi-wavelength Universe.
Light and Vision: Ours is a Universe of light…The light we see defines the way we understand the world around us. What is solid and what is insubstantial, what is bright and what is dark, what is beautiful and what is ugly. All of these concepts derive from visual cues. But since our vision is inextricably linked to the nature of the Sun, in a real sense even aesthetics are deeply rooted in astronomy. Perhaps it is no wonder that images of the Universe can trigger such a sense of awe. But the light from the Universe contains so much more than the light we can see for ourselves...
View from the Ground: Astronomy is an observational science. Apart from the use of space probes in the Solar System, it is not possible to carry out experiments in situ, and information must be gleaned from light signals collected by telescopes and measured with instruments such as cameras and spectrometers, which spread out the light into its constituent wavelengths and allow a closer study. Most of the telescopes in existence observe the heavens from the ground — often from remote mountain tops to get above as much of the Earth’s disturbing atmosphere as possible. But ground-based telescopes are much more than the well known visible-light telescopes that collect light from remote stars and galaxies with gigantic mirrors...
Space Observations: Astronomical observatories in space have revolutionised our knowledge of the Universe. They are one amongst the many types of satellites launched since the beginning of the space age, devoted to a great variety of applications including Earth observation, communication and broadcasting, navigation and military, right up to fully habitable space stations. Space observatories give access to light that is not visible from the ground and provide an undisturbed view of the star- and galaxy-studded sky. Expensive yes, but unbeatable in the search for the elusive photons from the hidden Universe.
The Visible Universe: The visible part of the electromagnetic spectrum is the astro-nomical base camp. This is where people first started to look at the sky with the naked eye many thousands of years ago and it remains the reference point for research taking place in all other wavelength bands. The visible band is home to the majority of the starlight and, although many scientists and engineers are finding ingenious ways to exploit the non-visible bands, there are still many secrets left to explore in the visible....
The infrared Universe: The infrared band lies just beyond the deepest red we can see. This band of the electromagnetic spectrum is a window onto a cool, dust-filled Universe. By allowing us to peer through the obscuring dust, strewn between the stars like an interstellar fog, it reveals distant reaches of our Milky Way hidden outside the visible spectrum.
At longer infrared wavelengths the dust itself becomes luminous, showing us a different facet of the wispy tendrils of tiny grains that drift through the vastness of space between the stars. Shrouded by these dust clouds, young stars form and planets like our own are assembled.
The Ultraviolet Universe: Ultraviolet light falls beyond the limits of what we can see at the blue end of the spectrum. In human terms the word ultraviolet calls to mind images of sore skin resulting from overexposure to the Sun, an indication of the high energy of this form of light. The hottest stars in the Universe are brightest in ultraviolet light. The dusty clouds that give birth to these massive, luminous objects are in turn sculpted and shaped under the onslaught of the high energy photons they emit. Ultraviolet light shows us where the action is in star formation — amongst the young, the massive and the hot stars.
The radio and microwave universe: Seen with radio telescopes, the sky is unrecognisable to a visible-light astronomer. In place of the stars in the Milky Way there are objects sprinkled throughout the entire Universe. Radio sources are rare but often intrinsically very powerful, making them detectable at very large distances. The emissions from these radio galaxies, quasars and titanic stellar explosions are the result of immensely energetic sub-atomic particles speeding through regions of twisted magnetic fields. This process is quite different from that producing the heat radiation from the surfaces of stars and it leads us to the sites of some of the most violently energetic action in the Universe.
The x-ray and high energy universe : Beyond the ultraviolet we reach the highest energies of the electromagnetic spectrum. From X-rays to the even more energetic gamma rays, the increasingly rare photons have to be counted one by one. Only the most dramatic phenomena will generate light at this far end of the spectrum. This means that X-rays and gamma rays are our window into the study of cataclysmic processes such as the explosions of massive stars and the neutron stars and black holes they leave behind, as well as hot plasmas in galaxy clusters and in nearby stars.
The Multi-wavelength universe: Astronomy began as a visual science. For thousands of years, humans used little more than their eyes to observe and record the light from the stars. All this changed 400 years ago when Galileo first turned his telescope towards the heavens, dramatically expanding our ability to see and understand the Universe. Yet, for the next 350 years, the potential of this magnificent device was limited to that tiny sliver of the spectrum visible to human eyes. As we have seen in this book, a series of technological advances over the past 50 years or so has given us access to the hidden Universe: the cosmic domains of radio waves, infrared light, ultraviolet light, X-rays and gamma rays. Layer by layer, the cosmic onion has been peeled away to reveal a richness and complexity that was unimaginable from our long-held visible perspective. We show the fundamental change in worldview brought about by expanding our perception to include the full spectrum of light.
By IB Times Staff Reporter | February 11, 2011 6:11 AM EST
A NASA team has identified about 2,100 young star candidates in a region called the North American Nebula. The nebula is named after its resemblance to the North American continent in visible light. There were only about 200 young stars known before.
NASA/JPL-Caltech: A NASA team has identified about 2,100 young star candidates in a region called the North American Nebula.
NASA's Spitzer Space Telescope has taken images of the new stars at all stages of development, from dusty little tots to young adults.
Young stars are hidden in visible-light images as they grow up surrounded by blankets of dust. NASA says dusty, dark clouds in the visible image become transparent in Spitzer's view.
"One of the things that makes me so excited about this image is how different it is from the visible image, and how much more we can see in the infrared than in the visible," says Luisa Rebull of NASA's Spitzer Science Center at the California Institute of Technology, Pasadena, Calif. "The Spitzer image reveals a wealth of detail about the dust and the young stars here."
Revealing a Hidden Universe: Into The Cosmic Time-Machine:
3) Hidden Black Holes
NASA Scientists Conduct Census of Nearby Hidden Black Holes
Scientists on a quest to find hidden black holes in the local universe have found surprisingly few.
Image to right: This illustration shows the thick dust torus that astronomers believe surrounds supermassive black holes and their accretion discs. When the torus is seen edge-on’ as in this case, much of the light emitted by the accretion disc is blocked. However, the sharp X-ray and gamma-ray eyes of INTEGRAL can peer through the thick dust and locate "hidden" black holes. INTEGRAL's survey of the local universe searched for hidden black holes but found few, which implies these kinds of black holes are largely in the more distant (earlier) universe.
resolution jpg/+ High
resolution TIF image (6 MB) Credit: ESA / V. Beckmann (NASA-GSFC)
The observation implies that if these hidden black holes exist---and most scientists are convinced they do---they must be from the more distant, earlier universe, a concept that has interesting implications for galaxy evolution.
This work constitutes the first census of the highest-energy part of the X-ray sky, where the most dust-enshrouded black holes are thought to shine. A team from NASA's Goddard Space Flight Center in Greenbelt, Md., conducted the census, comprised of nearly two years of continuous data from the European Space Agency's International Gamma Ray Astrophysics Laboratory, or INTEGRAL, satellite.
"Naturally it is difficult to find
something we know is hiding well and which has eluded detection so far,"
said Volker Beckmann of Goddard and the University of Maryland, Baltimore
County, lead author on a report in an upcoming issue of The Astrophysical
Journal. "INTEGRAL is a telescope that should see nearby hidden black
holes, but we have come up short."
The X-ray sky is thousands to millions of times more energetic than the visible sky familiar to our eyes. Much of the X-ray activity is from black holes violently sucking in gas from their surroundings.
Image above: This all-sky map shows regions of ionized hydrogen gas in the local universe. The hidden black holes detected in the INTEGRAL survey of high-energy X-ray sources are located within the diamond-shape marks. Many sources were detected through the line of sight of the dusty Milky Way galactic plane, which is the bright area stretching across the center of the entire image from left to right. Click image to enlarge. Credit: D. Finkbeiner (hydrogen) / ESA, INTEGRAL, V. Beckmann, NASA-GSFC (gamma ray)
Recent breakthroughs in X-ray astronomy, including a thorough black hole census with NASA's Chandra X-ray Observatory and Rossi X-ray Timing Explorer, have all dealt with lower-energy X-rays. The energy range is roughly 2,000 to 20,000 electron-volts. Optical light, in comparison, is about 2 electron volts.
The INTEGRAL survey is the first of its kind to glimpse into the largely unexplored higher-energy, or "hard," X-ray regime of 20,000 to 40,000 electron-volts.
"The X-ray background, this pervasive blanket of X-ray light we see everywhere in the universe, peaks at about 30,000 electron volts, yet we really know next to nothing about what produces this radiation," said co-author Neil Gehrels of Goddard.
The theory is that hidden black holes, which scientists call Compton-thick objects, are responsible for the peak at 30,000 electron volts. These X-rays are so energetic that they would penetrate even the most dust-enshrouded black holes yet remain beyond the range of powerful lower-energy X-ray observatories such as Chandra.
High-energy light in general is harder to focus than optical and lower-energy (longer-wavelength) forms of light. As a result, INTEGRAL doesn't have the resolution to make sharp images like Chandra and Hubble can.
"Basically, the higher you go in energy, the harder it is to detect faint sources," said Chris Shrader of Goddard, another co-author. "This is why no hard X-ray mission has been able to study many individual objects in the distant universe. That would require a next-generation telescope. But INTEGRAL is now the first to resolve the local universe."
INTEGRAL can obtain an unbiased count of black holes in the local universe by virtue of seeing even those that are hidden. Of all the black hole galaxies that INTEGRAL detected---that is, galaxies with supermassive black holes in their cores actively accreting gas---about 40 percent were unobscured black hole galaxies, called Seyfert 1 galaxies. About 50 percent were somewhat obscured black hole galaxies called Seyfert 2 galaxies. And less than 10 percent were the heavily shrouded "
This implies that if hidden black holes make up the bulk of the X-ray background, they aren't local. Why? One reason could be that, in the modern local universe, these black holes have had time to blow away the gas and dust that once enshrouded them, leaving them unobscured. This liberation of gas and dust would have its consequences; it would blow away to influence star and galaxy formation elsewhere.
"This is just the tip of the iceberg," Beckmann said. "In a few more months we will have a larger survey completed with the Swift mission. Our goal is to push this kind of observation deeper and deeper into the universe to see black hole activity at early epochs. That's the next great challenge for X-ray and gamma-ray astronomers."
Simona Soldi and Nicolas Produit of the INTEGRAL Science Data Centre near
Instead, I advocate thinking about them as sound-like: Gravitational waves encode in an aural-like manner the dynamics of the source that generates them. You can almost think of as language-like: The signal that we "hear" encodes information about its source. Our goal as theorists and (eventual) GW astronomers is to understand that encoding, and thus to map those signals we "hear" into a deeper understanding of their sources.
NB, this is a very early version of a page that will provide much information about GW sources and science. We will continue to develop this material over the next few years. As a consequence, things are somewhat jumbled at the moment; some files might not work perfectly, and only a few file formats are currently available.
Equal mass binary gravitational waves.
The following sounds encode the signal that we would measure when two bodies of equal mass spiral into one another. These files are available in wav and mp3 formats. The wav format files seem not quite right - I sometimes find that my wav player doesn't exit cleanly. The mp3 format files appear to pause a bit before they start.
At the start of this sound, the stars
are separated by about
At the start of this sound, the black
holes are separated by about
At the start of this sound, the black holes are either touching each other or very nearly touching.
Commentary: These sounds are presented in the frequency band that corresponds to LIGO's best sensitivity. For the lighter sources (the neutron stars and the pair of 2 ½ solar mass black holes), this means that we hear the "inspiral" signal - the waves generated while the bodies are relatively far apart and orbiting around one another. We hear the frequency and amplitude "chirp" up because the bodies are spiraling towards one another, eventually being driven to merge. We do not hear the final splat itself in this case because it is not in the region of best sensitivity. (This final merger may be more accessible with future detector upgrades.)
For the heaviest source (the pair of 50 solar mass black holes), the inspiral is at low frequencies that LIGO does not hear very well. However, the final splat is in fact right in band. That "pop" we hear corresponds to the black holes' final thrashing as they settle down into a new, more massive black hole.
Extreme mass ratio binary gravitational waves.
These sounds encode waves generated by the spiral-in of stellar mass compact bodies captured by massive black holes - for example, a 10 solar mass black hole spiraling into a million solar mass black hole. Black holes in this mass range are found in the nuclei of almost every galaxy; sources of this type are one of the key science targets for the NASA/ESA LISA mission.
These files are available at present in wav format only.
Important technical note: The frequencies of these sources (and of LISA's best sensitivity) are far lower than that of the human ear! (The peak sensitivity of LIGO, by contrast, corresponds almost exactly to human audio.) Accordingly, I had to fudge things a bit: All frequencies are shifted by a factor of a few thousand from the way that nature would actually present them. Think of it as the audio equivalent of a "false color" image.
· Sound 1: Initially circular orbit, into rapidly spinning black hole: wav format
· Sound 2: Initially circular orbit, into slowly spinning black hole: wav format
· Sound 3: Initially highly eccentric orbit, into rapidly spinning black hole: wav format
Commentary: The first two sounds illustrate the impact of the large black hole's spin upon the gravitational wave. The sound is modulated - the "buzz" you should hear in the first sound - due to the large black hole's very rapid spin. It's interesting to contrast Sounds 1 and 2 - this modulation is far weaker in Sound 2. Sound 1 also lasts much longer; this is because the black hole's spin has a very strong influence on how far the small body will inspiral before falling into the large black hole. In both of these cases, if the large black hole is one million solar masses, then the orbital radius is initial around 6 - 10 million kilometers; it decreases to a radius of a few million kilometers before the small body plunges into the massive black hole. (A million solar mass black hole would itself have a radius of about 1 ½ - 3 million kilometers.)
The third sound illustrates a very different case. The initial orbit in this case is extremely eccentric - think of a comet's orbit around the sun. Each of the pops you should hear corresponds to the smaller body passing close to the black hole and moving very rapidly. The sequence of pops gets closer together as the eccentricity shrinks. In this calculation, the eccentricity drops all the way to zero, and the final inspiral is perfectly circular. (Note, we now know that this behavior is not quite right; its manifestation here is because Sound 3 was generated using an approximation to the real laws of GW emission. Newer calculations show that the eccentricity shrinks, but is unlikely to reach zero. An updated sound will be posted here before too long.)
Last modified 2 November 2004
Jun 2, 2004
Astronomers have discovered 31 previously undetected supermassive black
holes with a “virtual” observatory - the first major discovery to be made with
the virtual approach to astronomy. Paolo Padovani of the European Southern
Observatory (ESO) and colleagues at ESO,
Quasars are star-like objects that are thought to be fuelled by supermassive black holes. Padovani and colleagues searched for a rare type quasar known as an obscured quasar. However, these objects - as their name suggests - are partially hidden by clouds of dust and gas, which makes them too faint to be observed by classical methods.
To overcome this problem, the ESO team used the Astrophysical Virtual Observatory (AVO) - a database that combines visible data from the Hubble Space Telescope, near-infrared data from the Very Large Telescope (VLT), and X-ray data from the Chandra observatory. Padovani and co-workers found 68 candidate obscured quasars, and 31 of these had characteristics that suggested they were associated with supermassive black holes.
“This discovery means that so far we might have been underestimating the number of powerful supermassive black holes by at least a factor of two, possibly up to a factor of five,” Padovani told PhysicsWeb. “This has important implications for our understanding of active galactic nuclei and quasars and therefore, given the likely connection between quasar and galaxy formation, for galaxy formation as well.”
The results also demonstrate the potential of the virtual
observatory methods. “One major obstacle in taking spectra of these sources is
their faintness, which puts them beyond the reach of even very large (8 to
The team now plans to use data from the VLT and the Spitzer Space Telescope, which operates in the far-infrared, to place tighter constraints on the redshift of the sources.
About the author: Belle Dumé is Science Writer at PhysicsWeb
4) Cosmological horizon
The cosmological horizon, (also known as the particle horizon) is the maximum distance from which particles could have traveled to the observer in the age of the universe. It represents the boundary between the observable and the unobservable regions of the universe. The existence, properties, and significance of a cosmological horizon depend on the particular cosmological model being discussed.
where a(t) is the scale
factor of the Friedmann-Lemaître-Robertson-Walker metric, and we have taken the Big Bang to
be at t =
(سَنُرِيهِمْ آيَاتِنَا فِي الْآفَاقِ وَفِي أَنْفُسِهِمْ حَتَّى يَتَبَيَّنَ لَهُمْ أَنَّهُ الْحَقُّ أَوَلَمْ يَكْفِ بِرَبِّكَ أَنَّهُ عَلَى كُلِّ شَيْءٍ شَهِيدٌ) (فصلت س 41، آية 53)
(Soon will We show them Our Signs in the horizons, and in their own souls, until it becomes manifest to them that this is the Truth. Is it not enough that thy Lord doth witness all things?) (S. 41, V. 53)
The particle horizon differs from the event horizon in that the particle horizon represents the largest comoving distance from which light could have reached the observer by a specific time, while the event horizon is the largest comoving distance from which light emitted now can ever reach the observer.
(فَلَا أُقْسِمُ بِمَا تُبْصِرُونَ * وَمَا لَا تُبْصِرُونَ) (الحاقة س 69، الآيتان 38-39)
(So I do call to witness what ye see * And what ye see not,) (S. 69, V. 38-39)
Some parts of the Universe may simply be too far away for the light from there to have reached Earth. Due to the expansion of space, at a later time they could be observed.
The visible universe is somewhat smaller than the observable universe since we see only light from the cosmic microwave background radiation that was emitted after the time of recombination, giving us the spherical surface of last scattering (gravitational waves could theoretically allow us to observe events that occurred earlier than the time of recombination, from regions of space outside this sphere).
1. ^ a b http://books.google.com/books?id=kNxeHD2cbLYC&pg=PA447&dq=%22Particle+horizon%22&as_brr=3#v=onepage&q=%22Particle%20horizon%22&f=false Cosmology: the science of the universe By Edward Robert Harrison, p. 447
2. ^ http://books.google.com/books?id=xma1QuTJphYC&pg=PA418&dq=%22Particle+horizon%22&as_brr=3#v=onepage&q=%22Particle%20horizon%22&f=false General relativity: an introduction for physicists By Michael Paul Hobson, George Efstathiou, Anthony N. Lasenby, p. 419