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How to Observe Exploded Stars

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How to Observe Exploded Stars DEEPSKY OBSERVING Massive stars die in fantastic style. Their remains form spectacular telescopic sights. ⁄⁄⁄ BY STEVE GOTTLIEB A cosmic motivation On July 4, 1054, Chinese astrologers How to observe announced the appearance of a “guest star” in Taurus. This supernova quickly sur- passed Venus in brightness and remained visible for 23 days during daylight and 21 exploded stars months at night. The debris from this event is an SNR now known as the Crab Nebula (M1). A violent event called a supernova In 1731, British physician and amateur happens in a galaxy once or twice a century. A star heavier astronomer John Bevis made the first tele- scopic observation of the 1054 remnant. than about 12 solar masses ends its brief life span in a dra- French comet-hunter Charles Messier matic explosion called a core-collapse supernova. The super- rediscovered the nebula in 1758, describing nova ejects most of the star’s material while creating heavy “a whitish light, elongated in the shape of a flame of a candle, discovered while observ- elements such as lead, silver, and gold. This interstellar molecular clouds. The star’s ing the comet of 1758.” This observation process forged many of the elements in our debris mixes with the interstellar medium, inspired Messier to compile his famed cata- bodies and the solar system. forming a delicate supernova remnant log of 103 deep-sky objects; he placed this The blast releases as much energy as all (SNR). It’s a spectacular telescopic target. SNR first, designating it M1. of the other stars in the galaxy combined. Radio and X-ray surveys have revealed 265 When Irish astronomer William Parsons The star then shines intensely enough to be such SNRs — a type of nebula, or glowing (the third Earl of Rosse) trained his 36-inch visible in the daytime for several days. gas — but only a few of them are visible in reflector on M1 in 1844, he described The blast’s expanding shock wave prop- backyard scopes. Follow along for a tour of “resolvable filaments singularly disposed, agates into space, compressing and heating the most spectacular sights. springing principally from its southern extremity, and not, as is usual in clusters, irregularly in all directions.” A remarkable sketch by Lord Rosse, published in the Phil- osophical Transactions of the Royal Society of 1844, shows filaments or appendages streaming out the sides and inspired the name “Crab Nebula.” In 1967, Cambridge University graduate student Jocelyn Bell and advisor Anthony Hewish used a radio telescope to discover the first pulsar — a rapidly rotating neutron star with an intense magnetic field produc- ing a narrow beam of radiation that sweeps through our line of sight. Before this obser- vation, astronomers suspected neutron stars were the corpses of massive stars that died in supernova explosions. One year later, in 1968, astronomers discovered the Crab Nebula’s corpse star: a 16th-magnitude pul- THE JELLYFISH NEBULA (IC 443) sar that rotates about 30 times a second. A in Gemini exhibits tendrils of neb- ulosity hanging from the central Steve Gottlieb gave readers a tour of Wolf- object. This wreckage is from a THE CRAB NEBULA (M1) harbors a pulsar at its center. Shocked gas and interstellar mate- Rayet bubbles in the February 2006 issue. He star that exploded roughly 5,000 rial give this supernova remnant its twisting filaments. BRIAN LULA observes under the skies of northern California. years ago. MARK HANSON © 2011 Kalmbach Publishing Co. This material may not be reproduced in any form astronomywithout permission⁄⁄⁄ september from the publisher. www.Astronomy.com After observing the Veil from a dark site countless times over the past 25 years, I’m still astonished by its intricate, lacy threads. With my 10x30 image-stabilized bin- oculars, the eastern section, NGC 6992/5, is faintly visible as a narrow, ghostly arc in a rich star field. An 80mm refractor at low power will frame both the eastern and western arcs and reveal the Veil as a huge, glowing bubble. With an 8-inch scope and a narrowband filter, the main arcs resolve into delicate, filamentary wisps. The western arc, NGC 6960 or the “Witch’s Broom,” is more than 1° long and pierced by 52 Cygni. The south- ern end broadens and bifurcates, while the brighter northern end tapers to a spike. Larger scopes show a breathtaking view, in which the brighter filaments take on a noticeable electric appearance. The more detailed eastern arc, sometimes dubbed THE VEIL NEBULA in Cygnus shows off a bubble structure that makes its origin — an “The Waterfall,” has a surreal amount of explosion — apparent. You can split the Veil into three objects from east to west: the lacy, filamentary detail and multiple strands Waterfall, Pickering’s Wedge, and the Witch’s Broom. ADAM BLOCK that appear three-dimensional and braided. Feathery, side-branching nebulosity streams THE PENCIL NEBULA (NGC 2736) is the Vela Supernova Remnant’s twisted filaments of nebulosity. This SNR is one of the nearest to gradual slowdown of the pulsar provides the The magnificent to the west on the nebula’s southern end. brightest strand. Shock-compressed interstellar gas results in Earth (just 815 light-years away). DANIEL VERSCHATSE energy for the glowing nebula. The premier visual SNR is the Veil Nebula. A triangular piece known as “Pickering’s The Crab Nebula is a snap to locate — Its three main sections (NGC 6960 and NGC Wedge” sits between the two main branches In my 18-inch at 64x, the brightest sec- of nebulosity to the southwest. You can fol- ness, this ethereal thread is a challenge to roughly 1° northwest of 3rd-magnitude Zeta 6992/5) form a partial cosmic wreath nearly on the northern side. This 45'-long triangu- tion appears as a gently curving band of low another long, narrow filament to the detect among the maze of Milky Way stars. (ζ) Tauri — but the nebula will appear fea- 3° in diameter. Astronomers previously esti- lar wisp is widest at the northern end and nebulosity oriented northwest to southeast west of the 5th-magnitude double star HD Fortunately, like other SNRs, it exhibits tureless in light-polluted skies. For the best mated the Veil was at least 2,500 light-years shows a split. It displays much of the same and roughly 10' by 3'. A well-defined arc 72127 at R.A. 8h29.5m and Dec. –44°43'. strong OIII emission. A narrowband filter view of any SNR, head to a dark site, and away, but research using the Hubble Space wispy structure as its brighter counterparts. forms the eastern boundary southwest of The Vela SNR’s brightest strand is the increases contrast and enhances the view. use a narrowband filter to increase contrast. Telescope (HST) and the Far-Ultraviolet the bright arc. At the bright arc’s southern Pencil Nebula (NGC 2736). This isolated When I first took a look with my 18- At magnitude 8.5, the Crab is faintly Spectroscopic Explorer (FUSE) gives a The sky creature end, the glow dims and appears to hook linear filament is 4.5° east of the Vela pul- inch in 2001, I was amazed to find a gossa- visible in a 50mm finder scope or large, shorter distance of 1,500 light-years. These As the nickname suggests, the Jellyfish toward a triangle of stars. sar. The nebula’s form suggests the super- mer filament, just 1' wide but stretching handheld binoculars. A 6-inch scope will data have dropped the nebula’s estimated age Nebula (IC 443) is a strange creature. This nova’s shock front has compressed a dense across 14' of a crowded Milky Way field. reveal a 6' by 4' glow with pinched-in sides. from 30,000 years to less than 10,000. expanding bubble of debris has sculpted a A southern delight region of interstellar gas in the galactic This ghostly wisp dangles from an 8th- This pinch creates an irregular potato shape William Herschel discovered the Veil shell of shocked gas about 50' northeast of At a distance of roughly 815 light-years, the plane. When I observed the Pencil Nebula magnitude star on its southwest end. From with extensions toward the northwest and more than 220 years ago, and, until 1980, it 3rd-magnitude Eta (η) Geminorum. Ten- Vela Supernova Remnant is one of the from Costa Rica with a 13.1-inch scope and there, the nebula gracefully arcs to the southeast. In my 18-inch, I see subtle mot- was considered a challenging target. The drils of nebulosity appear to dangle from nearest. Its faint tendrils of nebulosity are a UHC filter, I found it easily. It’s a 20'-long northeast, passing by a 9.5-magnitude star. tling in the interior, while the nebula’s situation changed with the introduction of the SNR’s circular rim and create the jel- splashed across 5° of sky. splinter of light extending southwest to With careful viewing, portions of the fila- periphery looks tattered. An OIII filter nebula filters. Today, the Veil is a star-party lyfish appearance. Even though the Vela SNR is fainter northeast with weak filamentary structure ment resolve into two strands. To find this brings out some filamentary streaks, par- favorite. You can easily locate it by pointing The SNR is slamming into a nearby than the Veil, you can trace much of the and hints of two intertwined threads. obscure SNR, head to a dark site, and search ticularly on the southwest side. your scope at 4.3-magnitude 52 Cygni. dense molecular cloud, crushing and Vela in an 8-inch using an OIII filter.
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