Sh2-308

Last updated
Sh2-308
Emission nebula
Dolphin Head Nebula - Lucky Budd - Jan 2022.tif
Observation data: J2000.0 epoch
Class3 2 2
Right ascension 06h 54m 13s
Declination −23° 55′ 42″
Distance4530  ly
Apparent magnitude (V)7.0
Apparent dimensions (V)35′×35′
Constellation Canis Major
Physical characteristics
Radius 30 ly
DesignationsSh-308, RCW 11, LBN 1052
See also: Lists of nebulae

Sh2-308, also designated as Sharpless 308, RCW 11, or LBN 1052, [1] and commonly known as the Dolphin-Head Nebula, is an H II region located near the center of the constellation Canis Major, composed of ionised hydrogen. [2] It is about 8 degrees south of Sirius, the brightest star in the night sky. The nebula is bubble-like and surrounds a Wolf–Rayet star named EZ Canis Majoris. This star is in the brief, pre-supernova phase of its stellar evolution. The nebula is about 4,530 light-years (1,389 parsecs ) away from Earth, [3] but some sources indicate that both the star and the nebula are up to 5,870 ly (1,800 pc) away. [4] [5] Yet others indicate the nebula is as close as 1,875 ly (575 pc) from Earth. [6]

Contents

Central star

Sh2-308 surrounds the Wolf–Rayet star EZ Canis Majoris, also designated EZ CMa or WR 6. Its apparent magnitude varies from 6.71 to 6.95. Its spectral type indicates that the star is very hot and luminous. The spectrum shows that it is devoid of hydrogen at the surface. [7] EZ Canis Majoris is expected eventually to explode in a supernova, therefore subsuming the nebula. [8]

Formation

The nebula was formed about 70,000 years ago by the star EZ Canis Majoris throwing off its outer hydrogen layers, revealing inner layers of heavier elements. [2] Fast stellar winds, blowing at 1,700 km/s (3.8 million mph) from this star, create the bubble-shaped nebula as they sweep up slower moving material from an earlier phase of the star's evolution. The hydrogen composing the nebula is ionised by intense ultraviolet radiation. [9] The nebula is approximately 60 light-years across at its widest point. [10]

Observation

The most favorable period for observing the nebula in the night sky is between the months of December and April. Its southern declination makes it easier to observe from the Southern Hemisphere, though it is easily visible from most of the Northern Hemisphere as well. It appears as a faint cloud in photographs taken with high-power amateur instruments, with the help of special filters.

Related Research Articles

<span class="mw-page-title-main">Wolf–Rayet star</span> Heterogeneous stars with unusual spectra

Wolf–Rayet stars, often abbreviated as WR stars, are a rare heterogeneous set of stars with unusual spectra showing prominent broad emission lines of ionised helium and highly ionised nitrogen or carbon. The spectra indicate very high surface enhancement of heavy elements, depletion of hydrogen, and strong stellar winds. The surface temperatures of known Wolf–Rayet stars range from 20,000 K to around 210,000 K, hotter than almost all other kinds of stars. They were previously called W-type stars referring to their spectral classification.

<span class="mw-page-title-main">Arches Cluster</span>

The Arches Cluster is the densest known star cluster in the Milky Way, about 100 light-years from its center in the constellation Sagittarius, 25,000 light-years from Earth. Its discovery was reported by Nagata et al. in 1995, and independently by Cotera et al. in 1996. Due to extremely heavy optical extinction by dust in this region, the cluster is obscured in the visual bands, and is observed in the X-ray, infrared and radio bands. It contains approximately 135 young, very hot stars that are many times larger and more massive than the Sun, plus many thousands of less massive stars.

<span class="mw-page-title-main">AG Carinae</span> Luminous variable star in the constellation Carina

AG Carinae is a star in the constellation Carina. It is classified as a luminous blue variable (LBV) and is one of the most luminous stars in the Milky Way. The great distance and intervening dust mean that the star is not usually visible to the naked eye; its apparent brightness varies erratically between magnitude 5.7 and 9.0.

<span class="mw-page-title-main">NGC 346</span> Open cluster in the constellation Tucana

NGC 346 is a young open cluster of stars with associated nebula located in the Small Magellanic Cloud (SMC) that appears in the southern constellation of Tucana. It was discovered August 1, 1826 by Scottish astronomer James Dunlop. J. L. E. Dreyer described it as, "bright, large, very irregular figure, much brighter middle similar to double star, mottled but not resolved". On the outskirts of the cluster is the multiple star system HD 5980, one of the brightest stars in the SMC.

<span class="mw-page-title-main">NGC 5307</span> Planetary nebula in the constellation Centaurus

NGC 5307 is a planetary nebula in the southern constellation of Centaurus, positioned less than 3° to the northeast of the star Epsilon Centauri. It was discovered by English astronomer John Herschel on April 15, 1836. The nebula is located at a distance of approximately 10.6 kilolight-years from the Sun. The central star, designated PNG 312.3+10.5, is a weak emission-line star, superficially similar to the WC subtype of Wolf–Rayet stars. It has a spectral class of O(H)3.5 V.

<span class="mw-page-title-main">WR 136</span> Star in the constellation of Cygnus

WR 136 is a Wolf–Rayet star located in the constellation Cygnus. It is in the center of the Crescent Nebula. Its age is estimated to be around 4.7 million years and it is nearing the end of its life. Within a few hundred thousand years, it is expected to explode as a supernova.

<span class="mw-page-title-main">EZ Canis Majoris</span> Binary star system in the constellation Canis Major

EZ Canis Majoris is binary system in the constellation of Canis Major. The primary is a Wolf-Rayet star and it is one of the ten brightest Wolf-Rayet stars, brighter than apparent magnitude 7.

<span class="mw-page-title-main">WR 7</span> Star in the constellation Canis Major

WR 7 is a Wolf–Rayet star in the constellation of Canis Major. It lies at the centre of a complex bubble of gas which is shocked and partially ionised by the star's radiation and winds.

<span class="mw-page-title-main">WR 102ka</span> Star in the constellation Sagittarius

WR 102ka, also known as the Peony star, is a slash star that is one of several candidates for the most luminous-known star in the Milky Way.

<span class="mw-page-title-main">VY Canis Majoris</span> Star in the constellation Canis Major

VY Canis Majoris is an extreme oxygen-rich (O-rich) red hypergiant (RHG) or red supergiant (RSG) and pulsating variable star 1.2 kiloparsecs from the Solar System in the slightly southern constellation of Canis Major. It is one of the largest known stars, one of the most luminous and massive red supergiants, and one of the most luminous stars in the Milky Way.

<span class="mw-page-title-main">WR 102ea</span> Star in the constellation Sagittarius

WR 102ea is a Wolf–Rayet star in the Sagittarius constellation. It is the third most luminous star in the Quintuplet cluster after WR 102hb. With a luminosity of 2,500,000 times solar, it is also one of the most luminous stars known. Despite the high luminosity it can only be observed at infra-red wavelengths due to the dimming effect of intervening dust on visual light.

<span class="mw-page-title-main">AB7</span> Binary star in the Small Magellanic Cloud in the constellation Tucana

AB7, also known as SMC WR7, is a binary star in the Small Magellanic Cloud. A Wolf–Rayet star and a supergiant companion of spectral type O orbit in a period of 19.56 days. The system is surrounded by a ring-shaped nebula known as a bubble nebula.

<span class="mw-page-title-main">WR 124</span> Star in the constellation Sagitta

WR 124 is a Wolf–Rayet star in the constellation of Sagitta surrounded by a ring nebula of expelled material known as M1-67. It is one of the fastest runaway stars in the Milky Way with a radial velocity around 200 km/s. It was discovered by Paul W. Merrill in 1938, identified as a high-velocity Wolf–Rayet star. It is listed in the General Catalogue of Variable Stars as QR Sagittae with a range of 0.08 magnitudes.

<span class="mw-page-title-main">WR 25</span> Binary star system in the constellation Carina

WR 25 is a binary star system in the turbulent star-forming region the Carina Nebula, about 6,800 light-years from Earth. It contains a Wolf-Rayet star and a hot luminous companion and is a member of the Trumpler 16 cluster. The name comes from the Catalogue of Galactic Wolf–Rayet Stars.

<span class="mw-page-title-main">WR 24</span> Wolf-Rayet star in the constellation Carina

WR 24 is a Wolf-Rayet star in the constellation Carina. It is one of the most luminous stars known. At the edge of naked eye visibility it is also one of the brightest Wolf Rayet stars in the sky.

<span class="mw-page-title-main">WR 102c</span>

WR 102c is a Wolf–Rayet star located in the constellation Sagittarius towards the galactic centre. It is only a few parsecs from the Quintuplet Cluster, within the Sickle Nebula.

<span class="mw-page-title-main">NGC 1501</span> Planetary nebula in the constellation Camelopardalis

NGC 1501 is a complex planetary nebula located in the constellation of Camelopardalis, discovered in 27 Aug 1787 by William Herschel. It is also known as the Oyster Nebula.

<span class="mw-page-title-main">Melnick 34</span> Binary star in the Large Magellanic cloud

Melnick 34, also called BAT99-116, is a binary Wolf–Rayet star near R136 in the 30 Doradus complex in the Large Magellanic Cloud. Both components are amongst the most massive and most luminous stars known, and the system is the most massive known binary system.

WR 102 is a Wolf–Rayet star in the constellation Sagittarius, an extremely rare star on the WO oxygen sequence. It is a luminous and very hot star, highly evolved and close to exploding as a supernova.

<span class="mw-page-title-main">WR 31a</span> Wolf Rayet star in the constellation Carina

WR 31a, commonly referred to as Hen 3-519, is a Wolf–Rayet (WR) star in the southern constellation of Carina that is surrounded by an expanding Wolf–Rayet nebula. It is not a classical old stripped-envelope WR star, but a young massive star which still has some hydrogen left in its atmosphere.

References

  1. ↑ "Sh 2-308". SIMBAD . Centre de données astronomiques de Strasbourg . Retrieved 2017-04-30.
  2. 1 2 "Inflating Sh2-308". www.spacetelescope.org. Retrieved 2017-05-22.
  3. ↑ van Leeuwen, F. (2007-11-01). "Validation of the new Hipparcos reduction". Astronomy and Astrophysics. 474 (2): 653–664. arXiv: 0708.1752 . Bibcode:2007A&A...474..653V. doi:10.1051/0004-6361:20078357. ISSN   0004-6361. S2CID   18759600.
  4. ↑ "APOD: 2009 April 23 - Sharpless 308". apod.nasa.gov. Retrieved 2017-05-02.
  5. ↑ Morris, P W; Crowther, P A; Houck, J R (2004-06-01). "Spitzer-IRS Sectroscopy of the Prototype Wolf–Rayet star EZ CMa (HD 50896)". arXiv: astro-ph/0406074 .
  6. ↑ Burningham, Ben; Naylor, Tim; Jeffries, R. D.; Devey, C. R. (2003-12-01). "On the nature of Collinder 121: insights from the low-mass pre-main sequence". Monthly Notices of the Royal Astronomical Society. 346 (4): 1143–1150. arXiv: astro-ph/0308488 . Bibcode:2003MNRAS.346.1143B. doi:10.1111/j.1365-2966.2003.07160.x. ISSN   0035-8711. S2CID   16366019.
  7. ↑ Hamann, W.-R.; Gräfener, G.; Liermann, A. (2006). "The Galactic WN stars". Astronomy and Astrophysics. 457 (3): 1015. arXiv: astro-ph/0608078 . Bibcode:2006A&A...457.1015H. doi:10.1051/0004-6361:20065052. S2CID   18714731.
  8. ↑ "Hubble Image of the Week - EZ Canis Majoris, Sh2-308". SciTech Daily. 2017-04-17. Retrieved 2017-05-26.
  9. ↑ Toalá, J. A.; Guerrero, M. A.; Ramos-Larios, G.; Guzmán, V. (2015). "WISE morphological study of Wolf-Rayet nebulae". Astronomy & Astrophysics. 578: A66. arXiv: 1503.06878 . Bibcode:2015A&A...578A..66T. doi:10.1051/0004-6361/201525706. ISSN   0004-6361. S2CID   55776698.
  10. ↑ Hille, Karl (2017-04-21). "Hubble's Cosmic Bubbles". NASA. Retrieved 2017-04-30.

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