The Methuselah Nebula (MWP 1) is a large, very old bipolar planetary nebula located approximately 4,500 light-years away in the northern constellation Cygnus (the Swan). With a diameter of 15 light-years, it is one of the largest planetary nebulae known.
Planetary nebulae are a very brief final phase in the lives of Sun-like stars. These objects typically last only 10 to 20 thousand years. They form when evolved central stars eject their outer layers into space, revealing bare cores which then ionize the gaseous clouds of expelled material. The ejected material eventually disappears into the interstellar medium and the central stars gradually cool until they no longer have enough energy to excite the surrounding clouds.
The Methuselah Nebula is unusually old for a planetary nebula. It has an estimated age of 150,000 years. The age was derived based on the nebula’s expansion rate. The shape of the symmetric planetary nebula traces the evolution of its central star in the late stages of its life cycle.
This image was obtained with the wide-field view of the Mosaic camera on the Mayall 4-meter telescope at Kitt Peak National Observatory. MWP1 is a very usually shaped, unusually large, and unusually old, planetary nebulae. The progenitor star is also one of the hottest stars known, so hot it is producing large amounts of X-rays. The image was generated with observations in the Oxygen [OIII] (blue) and Hydrogen-Alpha (orange) filters. In this image, North is up, East is to the left. Image credit: T.A. Rector (University of Alaska Anchorage) and H. Schweiker (WIYN and NOIRLab/NSF/AURA) (CC BY 4.0)
Like the central star of the Skull Nebula (NGC 246) in the constellation Cetus (the Sea Monster), the progenitor of the Methuselah Nebula is a PG 1159 star (pre-degenerate star). It has a hydrogen-deficient atmosphere and is currently in the process of evolving from a planetary nebula nucleus (PNN) into a hot white dwarf.
PG 1159 stars have an unusual atmospheric composition. Once they leave the asymptotic giant branch (AGB), they are believed to begin fusing helium again. As a result, their atmospheres contain material that was between the hydrogen- and helium-burning shells when the stars were still on the asymptotic giant branch.
The nebula’s central star, catalogued as RX J2117.1+3412, was discovered in a survey with the ROSAT satellite in the early 1990s. It is classified as a GW Virginis star, a pulsating white dwarf whose brightness varies due to non-radial gravity wave pulsations. It has the variable star designation V2027 Cygni.
In 2010 Werner et al. reported detecting iron in the star’s spectrum.
A 2020 study led by A. H. Córsico, Facultad de Ciencias Astronómicas y Geofísicas, Universidad Nacional de La Plata, Argentina, found an effective temperature of 170,000 ± 10 000 K for the star, based on an asteroseismological analysis of data obtained with the Transiting Exoplanet Survey Satellite (TESS). The team’s findings make RX J2117.1+3412 the hottest GW Virginis variable known. The researchers determined a distance of 502 ± 12 parsecs for the hot star.
The Methuselah Nebula has an apparent size of 13 by 9 arcminutes, corresponding to a linear size of 5.3 by 3.7 parsecs. The nebula’s bipolar morphology could be the result of a close binary central star or a central star with a strong magnetic field.
A 2021 study led by Alaa Ali, Department of Astronomy, Faculty of Science, Cairo University, Egypt, found a radius of 0.81 ± 0.08 parsecs, a dynamical age of 26.3 ± 5.6 × 103 years, and an evolutionary age of 3.4 ± 0.8 × 103 years for the Methuselah Nebula. The astronomers proposed a final mass of 0.58 solar masses for the central star. Their findings are based on the parallax and proper motion data collected by the Gaia space observatory.
Other studies estimated a mass of around 0.56 solar masses and a rotation period of 1.16 ± 0.05 days for V2027 Cygni.
Facts
The Methuselah Nebula has the catalogue designation MWP 1. The designation comes from the initials of its discoverers, the German astronomers C. Motch of the Max Planck Institute for Extraterrestrial Physics, K. Werner of the Institute of Theoretical Physics and Astrophysics, University of Kiel, and M. W. Pakull of the Heidelberg-Königstuhl State Observatory.
The astronomers identified the nebula’s central star as a new PG 1159 star in the ROSAT XRT all sky survey in 1992. Follow-up observations resulted in the discovery of the faint, large nebula around the star.
The central star of the Methuselah Nebula was discovered to be variable by T. K. Watson and K. Werner in 1992. The astronomers found brightness variations with an amplitude of 0.03.
Location
The Methuselah Nebula lies in the constellation of Cygnus, in the region of the Northern Cross asterism. It appears near the Swan’s wing, outlined by the orange giant star Aljanah (Epsilon Cygni) and yellow giant Zeta Cygni.
A smaller a fainter planetary nebula, named Alv 1 (PN G 79.8-10.2) after its discoverer, the Portuguese amateur astronomer Filipe Alves, appears in the same field of view. Alves discovered the nebula while imaging MWP 1. The nebulae lie about 1 degree south of the hot blue star Upsilon Cygni (mag. 4.43).
The Methuselah Nebula has a very low surface brightness and cannot be observed in amateur telescopes. It is best seen photographically.
Location of Methuselah Nebula (MWP1), image: Stellarium
Methuselah Nebula – MWP 1
| Constellation | Cygnus |
| Object type | Planetary nebula |
| Right ascension | 21h 17m 08.2817782392s |
| Declination | +34° 12′ 27.415995372″ |
| Apparent size | 13′ x 9′ |
| Distance | 4,500 light-years (1,380 parsecs) |
| Size | 15 light-years |
| Names and designations | Methuselah Nebula, MWP 1, PN G080.3-10.4, PN G080.8-10.6, PK 080-10 1, UCAC2 43874429, V2027 Cygni, V2027 Cyg, EUVE J2117+34.2, GSC2 N033322050500, 2MASS J21170827+3412274, TIC 117070953, RX J2117.1+3412, 1RXS J211707.9+341220, 1SWASP J211708.29+341227.6, WD 2115+339, Gaia DR2 1855295171732158080, Gaia DR3 1855295171732158080 |