بدين 1

بدين 1; Bedin I
	صورة مشروحة لمجرة بدين 1 (يسار)
بيانات الرصد (حقبة J2000)
الكوكبة	الطاووس
صعود مستقيم	19h 10m 45.41s
الميل	-59° 55′ 04.32″
المسافة	8.7+0.5; −0.7 Mpc
المقاس (س.ض.)	840 × 340 pc
الأبعاد الظاهرة (V)	20" × 8"
القدر الظاهر (V)	19.94
القدر المطلق (V)	−9.76
	انظر أيضاً: مجرة، قائمة المجرات

الإحداثيات: , −59° 55′ 04.32″

بدين 1، هي مجرة قزمة كروية تقع في كوكبة الطاووس. تقع المجرة وراء العنقود المغلق NGC 6752، وتبعد عن الأرض حوالي 28.38 مليون سنة ضوئية. بدين 1 هي أول المجرات القديمة المعروفة، والتي تشكلت منذ حوالي 10013 مليون سنة مضت، وتعتبر من أكثر الكواكب القزمة انعزالااً، وتقع على بعد 2.12 مليون سنة ضوئية تقريباً من NGC 6744، أقرب جيرانها الذين قد يحدثا مرتبطين فيزيائياً. على هذا النحو، اعتبرها فهماء الفلك "حفرية" من الكون المبكر. اكتشفت المجرة بالصدفة بواسطة الفلكي الإيطالي لويجي بدين، الذي كان يفهم الأقزام البيضاء في NGC 6752 باستخدام تلسكوب هبل الفضائي في سبتمبر 2018؛ أُعلن عن الاكتشاف في ورقة نُشرت في أواخر يناير 2019.

التسمية

بدين 1، تُنطق //، أسماها فريق اكتشافها على اسم قائدهم، لويجي بدين، وهوباحث في مرصد تابع للمعهد الوطني للفيزياء الفلكية في پادوا، إيطاليا. ويشتهر بالمكتشف الأوحد للمجرة. اختابر بدين والفريق اختار الفريق تجنب إعطاء المجرة "هوية مجهولة مبنية على إحداثياتها".

الخصائص

بدين 1 هي مجرة قزمة كروية معزولة، تحمل نفس خصائص المجرتين القزمتين KKR 25 وتوكانا. يقدر حجمها بحوالي 840 في 340 فرسخ، أو2.700 في 1.100 سنة ضوئية، أي خمس حجم سحابة ماجلان الكبرى. تحتوي المجرة على نجوم عمالقة حمراء منخفضة اللمعان، ويبلغ قطر استضاائتها ضعف قطر استضاءة مجرة درب التبانة تقريباً،بقدر مطلق −9.76. يعتقد حتى مجرة بدين 1 قد تشكلت منذ حوالي 10-13 بليون سنة، دون تشكل أي نجوم، مما يجعلها من أقدم المجرات المعروفة. كما يحتمل حتى تكون بدين 1 أكثر المجرات القزمة انعزالاً، إذ تبعد عن الأرض بعد 8.7 م.فرسخ تقريباً، أوحوالي 28.38 مليون سنة ضوئية، و650 كيلو-فرسخ على الأقل، أو2.12 مليون سنة ضوئية عن أقرب جيرانها، المجرة الحلزونية المتوسطة NGC 6744؛ وتفصل نفس المسافة بين مجرة درب التبانة ومجرة أندرومدا. ويعتقد بارتباطها فيزيائياً مع NGC 6744، على الرغم من المسافة التي تفصل بينهما. عمرها، انعزالها، وعدم تفاعلها مع المجرات الأخرى، أدى إلى حملها اعتبارها "أحفورة" من الكون المبكر.

الرصد

تقع بدين 1 في كوكبة الطاووس، عند المطلع المستقيم 19^h 10^m 45.41^sوميل -59° 55′ 04.32″. تقع المجرة وراء مجموعة من النجوم الخلفية مجهولة الاسم ضمن العنقود المغلق NGC 6752. تقدر أبعاد المجرة 20 فيثمانية ثانية قوسية من نقطة رصدها على الأرض، ويبلغ قدرها الظاهري 19.94، على الرغم من انخفاض ملحوظ في رؤييتها بسبب NGC 6752، خامس أكثر العناقيد المغلقة لمعاناً في السماء بقدر ظاهري 5.4. اكتشف بدين 1 بالصدفة بواسطة فريق كان يبحث عن أقزام بيضاء في عنقود نجمي في محاولة للوقوف على تقدير أفضل لعمرها.

انظر أيضاً

قائمة مجرات سميت بأسماء أشخاص
قائمة أقرب المجرات

المصادر

الهوامش

^ This photograph was taken in a three-day exposure of the Wide Field Channel (WFC) of the Advanced Camera for Surveys (ACS) aboard Hubble between 9-13 September 2018. Bedin I is visible behind a group of stars at the far left of the image as a cluster of distant points of light; it is partly cut-off by the image's 1×1 arcminute field of view.
^ Bedin I is ∼650 kiloparsecs from NGC 6744 along the plane of the sky. More accurate measurements to judge its horizontal distance, and thus its true distance from NGC 6744, are needed.

المراجع

Bedin, Luigi; Salaris, Maurizio; Rich, R. Michael; Richer, Harvey; Anderson, Jay; Bettoni, Daniela; Nardiello, Domenico; Milone, Antonio P.; Marino, A. F.; Libralato, Mattia; Bellini, Andrea; Dieball, Andrea; Bergeron, Pierre; Burgasser, Adam J.; Apai, Daniel (21 March 2019). "The HST Large Programme on NGC 6752. I. Serendipitous discovery of a dwarf Galaxy in background". Monthly Notices of the Royal Astronomical Society: Letters. Oxford University Press. 484 (1): L54–L58. doi:10.1093/mnrasl/slz004. Archived from the original on 31 January 2019. Retrieved 31 January 2019.
Plait, Phil (1 February 2019). "Astronomers accidentally discover a nearby galaxy in a Hubble image!". Syfy Wire. Archived from the original on 2 February 2019. Retrieved 2 February 2019.

الحواشي

^ Space Telescope Science Institute (31 January 2019). "Bedin 1 in NGC 6752". Hubblesite. Archived from the original on 1 February 2019. Retrieved 1 February 2019. Object Position - R. A. 19:10:45.41 Dec. -59:55:04.32; Dimensions - Image is about 1 arcmin across (about 9,000 light-years); Instrument - ACS/WFC; Exposure Dates - September 9-13, 2018
^ Plait 2019, "...it's sitting right near the core of NGC 6752, so there are lots of far brighter stars sitting near and even on top of it, contaminating the sample. [...] the galaxy is near the edge of the image’s field of view."
^ Bedin et al. 2019, "Unfortunately, Bedin I is very close to the border of the field of view, where the large dithers gave us an overall incomplete and shallower view with respect to the centre of the fov."
^ (in English). Launch Pad Astronomy, YouTube.ستة February 2019. Event occurs at 3:41. Retrieved 21 February 2019. ...designated Bedin ICS1 maint: unrecognized language (link)
^ Plait 2019, "which the astronomers named Bedin I, after the lead investigator on the team, Luigi Bedin"
^ Wall, Mike (31 January 2019). "Hubble Telescope Discovers 'Living Fossil' Galaxy in Our Milky Way's Backyard". Space.com. Archived from the original on 1 February 2019. Retrieved 1 February 2019. The find was fortuitous. An international team of astronomers was using Hubble's Advanced Camera for Surveys instrument to study white dwarfs [...] nicknamed Bedin 1, after discovery team leader L. R. Bedin of the INAF-Osservatorio Astronomico di Padova in Italy...
^ Instituto de Astrofísica de Canarias (1 August 2018). "After the Kepler supernova explosion, no survivors were left behind". Phys.org. Archived from the original on 1 February 2019. Retrieved 1 February 2019. ...says Luigi Bedin, researcher at Osservatorio Astronomico di Padova (INAF)
^ Freeman, David (31 January 2019). "Tiny 'oddball' galaxy discovered lurking in our cosmic backyard". NBC News MACH. Archived from the original on 1 February 2019. Retrieved 1 February 2019. The newfound galaxy, dubbed Bedin 1 in an acknowledgment of the scientist's singular role in its discovery [...] It's about 30 times smaller than the Milky Way and a thousand times dimmer.
^ Dvorsky, George (1 February 2019). "Astronomers Accidentally Discover a Hidden Galaxy Right Next Door". Gizmodo. Archived from the original on 2 February 2019. Retrieved 2 February 2019. Bedin 1 is located in the Pavo constellation [...] Bedin said he pleased with the galaxy’s new name, saying it was "nice to adopt a nickname from one of its discoverers instead of an anonymous identification based on its coordinates."
^ Bedin et al. 2019, "We conclude that this object is most likely an isolated dwarf spheroidal galaxy [...] The size and the estimated ellipticity of Bedin I offer the closest resemblance to the Tucana dwarf spheroidal galaxy. KKR 25 is an almost identical isolated dwarf system, with similar luminosity...
^ Griffin, Andrew (1 February 2019). "Astronomers accidentally find a tiny galaxy that is nearly as old as the universe itself". The Independent. Archived from the original on 2 February 2019. Retrieved 2 February 2019. Together, those porperties led astronomers to classify it as what is called a dwarf spheroidal galaxy. [...] Because it is so distant from any other galaxies – and so has been left largely undisturbed – as well as its old age, the astronomers refer to Bedin 1 as a fossil from the beginning of the cosmos.
^ Bedin et al. 2019, "...and size of ∼840 × 340 pc, about one-fifth the size of the Large Magellanic Cloud."
^ Bedin et al. 2019, "A comparison of the observed colour–magnitude diagram with synthetic counterparts, which account for the galaxy distance modulus, reddening, and photometric errors, suggests the presence of an old (∼13 Gyr) and metal-poor ([Fe/H] ∼ −1.3) population."
^ Plait 2019, "Still, enough individual stars are visible for the astronomers to examine them carefully. They were able to find quite a few red giant stars..."
^ Carter, Jamie (31 January 2019). "The Milky Way Has A New Neighbor. Accidental Discovery As Ancient Galaxy Photobombs Hubble Telescope". Forbes. Archived from the original on 1 February 2019. Retrieved 1 February 2019. The astronomers that fortuitously discovered Bedin 1 were on a hunt for white dwarf stars in an effort to measure the age of NGC 6752 [...] it is roughly a thousand times dimmer than our Milky Way.
^ Bedin et al. 2019, "^amax^-axis ∼20 arcsec (∼840 pc); ^bmax^-axis ∼8 arcsec (∼340 pc); ^mF606W 19.94; ^MF606W −9.76"
^ Bedin et al. 2019, "We conclude that this system likely formed more than 10 Gyr ago in a 'single' burst, and likely experienced no additional star formation since its formation."
^ Bedin, Luigi; Jäger, Mathias (31 January 2019). "Hubble fortuitously discovers a new galaxy in the cosmic neighbourhood". ESA/Hubble. Archived from the original on 1 February 2019. Retrieved 1 February 2019. It lies about 30 million light-years from the Milky Way and 2 million light-years from the nearest plausible large galaxy host, NGC 6744. This makes it possibly the most isolated small dwarf galaxy discovered to date. [...] astronomers were able to infer that the galaxy is around 13 billion years old — nearly as old as the Universe itself.
^ Bedin, Luigi; Villard, Ray (31 January 2019). "Hubble Accidentally Discovers a New Galaxy in Cosmic Neighborhood". NASA Solar System Exploration. Archived from the original on 1 February 2019. Retrieved 1 February 2019. Because of its 13-billion-year-old age, and its isolation — which resulted in hardly any interaction with other galaxies — the dwarf is the astronomical equivalent of a living fossil from the early universe. [...] The science team's results will be published online January 31, 2019, in the Monthly Notices of the Royal Astronomical Society: Letters.
^ Bedin et al. 2019, "...but could be associated with NGC 6744. [...] (so, at a minimum distance of ∼650 kpc on the plane of the sky). [...] Our photometry is too shallow to reach the horizontal branch, which would provide additional constraints on both the distance and star formation history."
^ Plait 2019, "It does appear to be in the same region of sky and at about the same distance as the big spiral NGC 6744, but even then they're separated by at least two million light years, a huge distance (Andromeda is about that far from the Milky Way)..."
^ ESA/Hubble Information Centre (31 January 2019). "Hubble fortuitously discovers a new galaxy in the cosmic neighbourhood". Phys.org. Archived from the original on 1 February 2019. Retrieved 1 February 2019. The aim of their observations was to use these stars to measure the age of the globular cluster, [...] Bedin 1, which lies far behind the foreground globular cluster NGC 6752.
^ Plait 2019, "Their combined light brings this galaxy to a magnitude of about 20..."
^ O'Meara, Stephen James (8 April 2013). "113 The Starfish, The Windmill NGC 6752". . Cambridge University Press. p. 411. ISBN . Archived from the original on 1 February 2019. Retrieved 1 February 2019. At magnitude 5.4, it can be seen with the naked eye, and it ranks 5th among the globular clusters in total brightness.

وصلات خارجية

The HST Large Programme on NGC 6752. I. Serendipitous discovery of a dwarf Galaxy in background at Monthly Notices of the Royal Astronomical Society: Letters (Archived 31 January 2019)