تلسكوب الفضاء هابل يلتقط صورة جميلة جدا لنجم السلحفاة اللامع


In space, being outshone is an occupational hazard. This NASA/ESA Hubble Space Telescope image captures a galaxy named NGC 7250. Despite being remarkable in its own right — it has bright bursts of star formation and recorded supernova explosions — it blends into the background somewhat thanks to the gloriously bright star hogging the limelight next to it.  This bright object is a single and little-studied star named TYC 3203-450-1, located in the constellation of Lacerta (The Lizard), much closer than the much more distant galaxy. Only this way a normal star can outshine an entire galaxy, consisting of billions of stars. Astronomers studying distant objects call these stars “foreground stars” and they are often not very happy about them, as their bright light is contaminating the faint light from the more distant and interesting objects they actually want to study. In this case TYC 3203-450-1 million times closer than NGC 7250 which lies over 45 million light-years away from us. Would the star be the same distance as NGC 7250, it would hardly be visible in this image.

مركز قطر لعلوم الفضاء والفلك: سلمان بن جبر آل ثاني

ظهر في صورة تلسكوب الفضاء هابل جرم سماوي لامع في كوكبة السلحفاة الشهيرة Lacerta وتسمى في الفلك الشعبي الحديث “السحلية” Lizard وهو عبارة عن نجم لامع منفرد ومدروس إلى حد ما، ويحمل الرمز TYC 3203-450-1 ويظهر النجم أقرب بكثير من المجرة البعيدة جدا.

تظهر في الصورة الملتقطة بواسطة تلسكوب هابل صورة واضحة للمجرة اللامعة التي تحمل الرمز NGC 7250 التي تبدوا رائعة وهادئة إلا أنها في الحقيقة غنية بالانفجارات اللامعة التي تتولد منها النجوم الجديدة، وكذلك النجوم المنفجرة أو السوبرنوفا supernova، حيث تمتزج الانفجارات مع بعضها بوضوح في خلفية الصورة، ويعود الفضل للنجم اللامع فيها الذي يعمل على إضاءة السدم والمادة المحيطة في السديم.

هذه الطريقة الوحيدة التي يمكن فيها أن يتجاوز لمعان نجم عادي لمعان مجرة بأكملها تتكون من بلايين النجوم، وعلماء الفلك الذين يدرسون النجوم البعيدة يسمون هذه النجوم “النجوم المتقدمة” foreground stars ولا يهمهم لمعانها الكبير وإضاءتها لما حولها، وإنما يريدون دراستها بشكل موسع لكشف المزيد من أسرارها.

وفي هذه الحالة يبدو النجم TYC 3203-450-1 أقرب بأكثر من مليون مرة من المجرة NGC 7250 التي تبعد عن الأرض بأكثر من 45 مليون سنة ضوئية، وإذا ما افترضنا أن النجم كان على نفس مسافة المجرة فأنه لن يظهر في هذه الصورة على الأطلاق.

Light travels through space at just under 300 000 kilometres per second! This staggering speed is used to calculate astronomical distances; although often misinterpreted as a unit of time (due to its misleading name), a light-year is actually a unit of astronomical distance, and is defined as the distance that light travels in a year. For reference, this is around nine trillion kilometres… but it’s a little tricky to visualise! With this in mind, 15 000 light-years may sound like a truly huge distance, but compared to the vastness of the cosmos, it’s really quite nearby. In fact, an object sitting 15 000 light-years away would not even be outside our home galaxy, the Milky Way. This is roughly the distance between us and a young super star cluster known as Westerlund 1, home to one of the largest stars ever discovered.  Stars are classified according to their spectral type, surface temperature, and luminosity. While studying and classifying the cluster’s constituent stars, astronomers discovered that Westerlund 1 is home to one of the largest stars ever discovered, originally named Westerlund 1-26. It is a red supergiant (although sometimes classified as a hypergiant) with a radius over 1500 times that of our Sun. If Westerlund 1-26 were placed where our Sun is in our Solar System, it would extend out beyond the orbit of Jupiter.  Most of Westerlund 1’s stars are thought to have formed in the same burst of activity, meaning that they have similar ages and compositions. The cluster is relatively young in astronomical terms — at around three million years old it is a baby compared to our own Sun, which is some 4.6 billion years old.