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Home , Messier 82, NGC 6302

TAAS Monthly Observing Challenge – June 2016

Deep Sky Object

NGC 6712 (GC) Scutum ra: 18h 53m 04.3s dec: -08° 42’ 22” Magnitude (visual) = 8.1 Size = 9.8’ Concentration class = 9 Distance = approximately 22,500 light years

Description: Probably discovered by Le Gentil on July 9, 1749. Discovered by William Herschel on June 16, 1784.

This globular was first cataloged by William Herschel as H I.47, as he first classified it as a bright round . John Herschel numbered it h 3762 in his "Cape" catalog on the ground of his observations in the 1830s, and included it in his General Catalogue of 1864 as GC 4441. At its distance of 22,500 light-years, NGC 6712's apparent diameter of 7.4 minutes of arc corresponds to a linear extension of about 50 light-years, and its visual brightness of 8.1 magnitude to an of -7.50, or an intrinsic of about 90,000 times that of our Sun. Its overall spectral type has been determined as F9. It is approaching us at 107.5 km/s.

Cecilia Payne-Gaposchkin mentions that a dwarf nova had occurred in NGC 6712, which makes it one of three globulars where such were observed, the others being M5 and M30. In 1999, ESO astronomers used the 8.2-m VLT Unit Telescope (UT1) to photograph and investigate globular cluster NGC 6712 and found evidence that this cluster is "evaporating," and has already lost its faintest stars to the halo.

Source: http://spider.seds.org/spider/MWGC/n6712.html

Al: Herschel 400, Globular Cluster

Challenge Object

NGC 6302 (PN) – aka Bug Nebula or Butterfly Nebula ra: 17h 13m 44.3s dec: -37° 06’ 13” Magnitude (visual) = 9.6 Size = 89” Distance = 3800 light years

Description: The Butterfly Nebula is a bipolar located in Scorpius. It lies at a distance of 3,800 light years from Earth. Named for its resemblance to a butterfly, the nebula has a wingspan that stretches across three light years. It is sometimes also called the Bug Nebula. It has the designation NGC 6302 in the .

The Butterfly Nebula has one of the most complex structures ever seen in a planetary nebula. The dying central is one of the hottest known stars in the . It has a surface temperature of around 222,204°C (400,000 F) and is hidden from view by dust clouds, but shines brightly in ultraviolet wavelengths. The dust cloud around the star has an estimated temperature of 18,000°C. The gas in the nebula is moving very quickly across space at over 600,000 miles (965,606 kilometres) per hour. The star at the centre of the nebula is a with an estimated mass of about 0.64 solar masses. It has a dense disc of dust and gas surrounding it at the equator, which is believed to have caused the star’s outflow of material to form the bipolar butterfly shape, resembling an hour-glass.

Source: http://www.constellation-guide.com/butterfly-nebula

AL: Caldwell 69, Planetary Nebula; TAAS 200

Binocular Object

M82 / NGC 3034 (GX) –aka Cigar Galaxy ra: 09h 55m 52.2s dec: +69° 40’ 48” Magnitude (visual) = 8.4 Size = 11.2’ x 4.3’ Position angle = 65° Distance = approximately 12 million light years

Description: M82 was discovered on December 31, 1774 by Johann Elert Bode together with M81; he described it as a "nebulous patch", about 0.75 deg away from M81, which "is very pale and of elongated shape," and cataloged it as No. 18 in his catalog. Pierre Méchain independently rediscovered both as nebulous patches in August 1779 and reported them to , who added them to his catalog after his position measurement on February 9, 1781.

Messier 82 (M82, NGC 3034) is a remarkable galaxy of peculiar type in Ursa Major. It is usually classified as irregular, though probably a distorted disk galaxy, and famous for its heavy star-forming activity, thus a prototype member of the class of starbursting galaxies.

Forming a most conspicuous physical pair with its neighbor, M81 (THE showpiece galaxies for many Northern hemispherers), this galaxy is the prototype of an irregular of the second type, i.e. a "disk" irregular. Its core seems to have suffered dramatically from a semi-recent close encounter with M81, being in a heavy starburst and displaying conspicuous dark lanes. This turbulent explosive gas flow is also a strong source of radio noise, discovered by Henbury Brown in 1953. The radio source was first called Ursa Major A (strongest radio source in UMa) and cataloged as 3C 231 in the Third Cambridge Catalogue of Radio Sources.

Recently, over 100 freshly-formed (young) globular clusters have been discovered with the . Their formation is probably another effect triggered by the encounter with M81. It was estimated that the most recent tidal encounter occurred between about 50 and several 100 million years ago:

Source: http://messier.seds.org/m/m082.html

AL: Binocular Messier

Double Star

Epsilon Lyrae (DS) Lyra – aka Double Double ra: 18h 44m 18.5s dec: +39° 40’ 12.4” Magnitudes (visual) = 5.0,6.1 / 5.3,5.4 Separation = 2.1” / 2.4” (210” between double star pairs) Position angle = 174° Distance = approximately 160 light years

Description: There are many multiple star systems in the sky, but Epsilon Lyrae is special because it’s so easy – and so satisfying – to see as multiple. You can easily split the widest two components of the Epsilon Lyrae quadruple system with binoculars. You might even be able to split them with the unaided eye under excellent sky conditions.

The two primary star systems of Epsilon Lyrae – the two that you see with binoculars – are thought to be 10,000 times the sun-Earth distance apart. They probably take at least a half a million years to revolve around each other. The component binaries visible through the telescope are much closer together. They’re believed to circle each other in periods of about a thousand years. And there are even more stars in this system. A fifth star orbits one of the primary pairs; it was first detected in 1986, not with the eye but with speckle imaging. Other nearby stars may also be part of the Epsilon Lyrae system, bringing the system to a total of 10 stars.

Source: http://earthsky.org/brightest-stars/epsilon-lyrae-the-famous-double-double-star

AL: Double Star