1 min read
Heavyweight Stars Light Up Nebula NGC 6357
The small open star cluster Pismis 24 lies in the core of the large emission nebula NGC 6357 in Scorpius, about 8,000 light-years away from Earth. Some of the stars in this cluster are extremely massive and emit intense ultraviolet radiation.
The brightest object in the picture is designated Pismis 24-1. It was once thought to weigh as much as 200 to 300 solar masses. This would not only have made it by far the most massive known star in the galaxy, but would have put it considerably above the currently believed upper mass limit of about 150 solar masses for individual stars.
However, Hubble Space Telescope high-resolution images of the star show that it is really two stars orbiting one another (inset pictures at top right and bottom right). They are estimated to each be 100 solar masses.
In addition, spectroscopic observations with ground-based telescopes further reveal that one of the stars is actually a tight binary that is too compact to be resolved even by Hubble. This divides the estimated mass for Pismis 24-1 among the three stars. Although the stars are still among the heaviest known, the mass limit has not been broken thanks to the multiplicity of the system.
The observations were performed by a team of astronomers led by J. Maí;z Apellániz of the Instituto de Astrofí;sica de Andalucí;a in Spain. The team imaged Pismis 24-1 with Hubble's Advanced Camera for Surveys in April 2006.
The images of NGC 6357 were taken with Hubble's Wide Field and Planetary Camera 2 in April 2002.
About the Object
- R.A. PositionR.A. PositionRight ascension – analogous to longitude – is one component of an object's position.17h 25m 23.99s
- Dec. PositionDec. PositionDeclination – analogous to latitude – is one component of an object's position.-34° 25' 59.99"
- ConstellationConstellationOne of 88 recognized regions of the celestial sphere in which the object appears.Scorpius
- DistanceDistanceThe physical distance from Earth to the astronomical object. Distances within our solar system are usually measured in Astronomical Units (AU). Distances between stars are usually measured in light-years. Interstellar distances can also be measured in parsecs.About 8,000 light-years (2,500 parsecs)
- DimensionsDimensionsThe physical size of the object or the apparent angle it subtends on the sky.2.4 arcminutes (6 light-years or 1.75 parsecs) wide
About the Data
- Data DescriptionData DescriptionProposal: A description of the observations, their scientific justification, and the links to the data available in the science archive.
Science Team: The astronomers who planned the observations and analyzed the data. "PI" refers to the Principal Investigator.This image was created from HST data from the following proposals: 10602: J. Maiz-Apellaniz (Instituto de Astrofísica de Andalucía, Spain), N. Walborn and E. Nelan (STScI), N. Morrell Carnegie Institution of Washington), and V. Niemela (Universidad Nacional de La Plata) 9857: O. De Marco (American Museum of Natural History), C. R. O'Dell (Vanderbilt University), and R. Rubin (NASA Ames Research Center) 9091: J. Hester, P. Scowen, and K. Healy, (Arizona State University). - InstrumentInstrumentThe science instrument used to produce the data.HST>ACS/WFC, HST>ACS/HRC, and HST>WFPC2
- Exposure DatesExposure DatesThe date(s) that the telescope made its observations and the total exposure time.April 2002 and April 2006
- FiltersFiltersThe camera filters that were used in the science observations.F550W (V), F547M (Strömgren y), F656N (Halpha), F658N (Halpha+[N II]), and F850LP (SDSS i)
- Object NameObject NameA name or catalog number that astronomers use to identify an astronomical object.Pismis 24, NGC 6357, Cl Pismis 24
- Object DescriptionObject DescriptionThe type of astronomical object.Open Star Cluster and Emission Nebula
- Release DateDecember 11, 2006
- Science ReleaseHeavyweight Stars Light Up Nebula NGC 6357
This image is a composite of many separate exposures made by the ACS and WFPC2 instruments on the Hubble Space Telescope using several different filters. Five filters were used to sample both broad and narrow wavelength ranges. The color results from assigning different hues (colors) to each monochromatic image. In this case, the assigned colors are: Blue: F550W (V) + F547M (Strömgren y) Red: F656N (Halpha) + F658N (Halpha+[N II]) + F850LP (SDSS i)
Related Images & Videos
Share
Details
Claire Andreoli
NASA’s Goddard Space Flight Center
Greenbelt, Maryland
claire.andreoli@nasa.gov
