Abell 30 is a planetary nebula located in the constellation of Cancer, at a distance of 5,500 light years. It belongs in the rare category of born-again planetary nebulae, in which stellar activity started up again after the creation of the planetary nebula.[1]
| Emission nebula | |
|---|---|
| Planetary nebula | |
 Composite image of Abell 30 in optical light and X-rays[1] | |
| Observation data: J2000.0 epoch | |
| Right ascension | 08h 46m 53s[2] |
| Declination | 17° 52′ 46″[2] |
| Distance | 5,500 ly |
| Apparent magnitude (V) | 14.3[2] |
| Apparent dimensions (V) | 0.29′ × 0.13′[2] |
| Constellation | Cancer |
| Notable features | born-again nebula |
| Designations | PK 208+33 1, Abell 30, IRAS F08440+1803, GALEX J084653.4+175248, 2MASS J08465346+1752463 |
Morphology
editAbell 30 consists of an outer shell, a faint cloverleaf pattern, and a central star that is surrounded by knots. The outer shell has a radius of 63 arcseconds and brightens gradually up to a sharp edge. The cloverleaf pattern is more pronounced towards the southeast and southwest and reaches 26 arcseconds from the centre, almost half away to the edge.[3]
The brightest knots lie within 10 arcseconds from the central star. Although originally four knots were identified, named J1 to J4, higher resolution images of the images revealed that they were composed of smaller knots and filaments.[4] These smaller knots are cometary in appearance, with a length of several arcseconds and a width of less than half an arcsecond. The nebula has two bright polar knots, lying about seven arcseconds from the central star,[5] and both feature a bow shock towards the central star. The other knots are arranged in a disk like the spokes of a wheel seen at an inclination of 60 degrees. To the southwest, where the bright knots are located, the knots form a fan.[6]
The infrared morphology of the nebula is quite different. It features smooth disk-like emission extending along a northeast to southwest axis, passing through the central star and knot J4, while no enhancement is seen at knots J1 and J3. Along the axis also lie the brightest parts of the outer shell of the nebula.[7] The X-ray emission of the nebula consists of a point source at the central star and diffuse emission associated with the knots and the cloverleaf structure. The diffuse emission is possibly the result of the material in the knots getting hit by the fast stellar wind and heated into plasma.[8]
The central star of the planetary nebula has been found to have a spectral type between a carbon rich Wolf–Rayet star and a PG 1159 star, and is categorised as a [WC]-PG 1159 star.[9] Its temperature is estimated to be 110,000 K. The star appears to be variable, with a period of 1.06 days. It is possible that the presence of a colder and dimmer companion is the source of the variability observed.[9]
Formation
editA planetary nebula is formed in the late stage of the evolution of a sun-like star. After having steadily produced energy for several billion years through the nuclear fusion of hydrogen into helium in its central region, or core, the star undergoes a series of energy crises related to the depletion of hydrogen and subsequent contraction of the core. These crises culminate in the star expanding a hundred-fold to become a red giant.[10]
Eventually the outer envelope of the red giant is ejected and moves away from the star at a relatively sedate speed of less than 100,000 miles per hour. The star meanwhile is transformed from a cool giant into a hot, compact star known as a white dwarf that produces intense ultraviolet radiation and a fast wind of particles moving at about 6 million miles per hour. The interaction of the UV radiation and the fast wind with the ejected red giant envelope creates the planetary nebula, creating a large spherical shell.[10] The outer shell has an observed age of 12,500 years.[1]
In rare cases, the helium shell of the star reaches critical mass and fuses into carbon and oxygen in the region surrounding the star’s core and heats the outer envelope of the star so much that it temporarily becomes a red giant again, in what is known as a very late thermal pulse.[11] The sequence of events – envelope ejection followed by a fast stellar wind – is repeated on a much faster scale than before, and a small-scale planetary nebula is created inside the original one. In a sense, the planetary nebula is reborn.[10] This new activity created the knots in the inner part of the nebula.[1] The expansion rate of the knots when observed by Hubble Space Telescope across a time span of 20 years indicates they have an age of 610 to 950 years.[11]
Composition
editThe central region of the nebula is notably depleted in hydrogen when observed in H-alpha emission and the knots appear to be rich in helium.[12]
See also
edit- Abell 78 - a similar planetary nebula
- V605 Aquilae - the central star of Abell 58, that underwent a very late thermal pulse
- Sakurai's Object - a star in a faint planetary nebula undergoing a very late thermal pulse
References
edit- ^ a b c d "Abell 30: X-rays from a Reborn Planetary Nebula". chandra.harvard.edu. Retrieved 15 November 2024.
- ^ a b c d "PN A66 30". simbad.cds.unistra.fr. Retrieved 10 November 2024.
- ^ Jacoby, G. H. (December 1979). "Unusual structure in the planetary nebulae Abell 30 and Abell 78". Publications of the Astronomical Society of the Pacific. 91: 754. doi:10.1086/130582.
- ^ Rodríguez-González, J B; Santamaría, E; Toalá, J A; Guerrero, M A; Montoro-Molina, B; Rubio, G; Tafoya, D; Chu, Y-H; Ramos-Larios, G; Sabin, L (6 July 2022). "Common envelope evolution in born-again planetary nebulae – Shaping the H-deficient ejecta of A 30". Monthly Notices of the Royal Astronomical Society. 514 (4): 4794–4802. doi:10.1093/mnras/stac1697.
- ^ Borkowski, Kazimierz J.; Harrington, J. P.; Tsvetanov, Zlatan; Clegg, Robin E. S. (September 1993). "HST imaging of hydrogen-poor ejecta in Abell 30 and Abell 78 - Wind-blown cometary structures". The Astrophysical Journal. 415: L47. doi:10.1086/187029.
- ^ Borkowski, Kazimierz J.; Harrington, J. Patrick; Tsvetanov, Zlatan I. (20 August 1995). "Interaction of a Stellar Wind with Clumpy Stellar Ejecta in A30". The Astrophysical Journal. 449 (2). doi:10.1086/309643.
- ^ Dinerstein, H. L.; Lester, D. F. (June 1984). "Evidence for an infrared disk in the core of the extraordinary planetary nebula Abell 30". The Astrophysical Journal. 281: 702. doi:10.1086/162147.
- ^ Guerrero, M. A.; Ruiz, N.; Hamann, W.-R.; Chu, Y.-H.; Todt, H.; Schönberner, D.; Oskinova, L.; Gruendl, R. A.; Steffen, M.; Blair, W. P.; Toalá, J. A. (20 August 2012). "REBIRTH OF X-RAY EMISSION FROM THE BORN-AGAIN PLANETARY NEBULA A30". The Astrophysical Journal. 755 (2): 129. doi:10.1088/0004-637X/755/2/129.
- ^ a b Jacoby, George H; Hillwig, Todd C; Jones, David (11 October 2020). "Abell 30 - A binary central star among the born-again planetary nebulae". Monthly Notices of the Royal Astronomical Society: Letters. 498 (1): L114–L118. doi:10.1093/mnrasl/slaa138.
- ^ a b c "A Reborn Planetary Nebula - NASA". nasa.gov. 16 November 2012. Retrieved 15 November 2024.
This article incorporates text from this source, which is in the public domain.
- ^ a b Fang, X.; Guerrero, M. A.; Marquez-Lugo, R. A.; Toalá, J. A.; Arthur, S. J.; Chu, Y.-H.; Blair, W. P.; Gruendl, R. A.; Hamann, W.-R.; Oskinova, L. M.; Todt, H. (5 December 2014). "Expansion of Hydrogen-Poor Knots in the Born-Again Planetary Nebulae A30 and A78". The Astrophysical Journal. 797 (2): 100. doi:10.1088/0004-637X/797/2/100.
- ^ Jacoby, G. H.; Ford, H. C. (March 1983). "The hydrogen-depleted planetary nebulae Abell 30 and Abell 78". The Astrophysical Journal. 266: 298. doi:10.1086/160779.
