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NGC 3603-A1 (HD 97950A1) is a double-eclipsing 
The two component stars of NGC 3603-A1 circle each other every 3.77 days, and show brightness variations of about 0.3 magnitudes due to eclipses. The stars orbit very close to each other, separated by barely their own diameters and at or near to filling their
NASA Image of the day
{{DEFAULTSORT:NGC 3603-A1 Carina (constellation) Wolf–Rayet stars NGC 3603 097950A1 054948A1 Durchmusterung objects Eclipsing binaries
binary star
A binary star is a system of two stars that are gravitationally bound to and in orbit around each other. Binary stars in the night sky that are seen as a single object to the naked eye are often resolved using a telescope as separate stars, in wh ...
system located at the centre of the HD 97950
HD 97950, is a multiple star system and part of a super star cluster within the NGC 3603 H II region. It was catalogued as a single star although it was always known to be a compact cluster. It is now resolved into a massive multiple star at th ...
cluster in the NGC 3603
NGC 3603 is a nebula situated in the Carina–Sagittarius Arm of the Milky Way around 20,000 light-years away from the Solar System. It is a massive H II region containing a very compact open cluster (probably a super star cluster) HD 97950.
...
star-forming region
Star formation is the process by which dense regions within molecular clouds in The "medium" is present further soon.-->interstellar space
, about 25,000 light year
A light-year, alternatively spelled light year, is a large unit of length used to express astronomical distances and is equivalent to about 9.46 trillion kilometers (), or 5.88 trillion miles ().One trillion here is taken to be 1012 ...
s from Earth
Earth is the third planet from the Sun and the only astronomical object known to harbor life. While large volumes of water can be found throughout the Solar System, only Earth sustains liquid surface water. About 71% of Earth's surfa ...
. Both stars are of spectral type WN6h and among the most luminous and most massive known.
HD 97950 was catalogued as a star, but was known to be a dense cluster or close multiple star. In 1926, the six brightest members were given letters from A to F, although several of them have since been resolved into more than one star. Star A was first resolved into three components using speckle interferometry
Speckle imaging describes a range of high-resolution astronomical imaging techniques based on the analysis of large numbers of short exposures that freeze the variation of atmospheric turbulence. They can be divided into the shift-and-add ("''i ...
, although they can now be directly imaged using space-based or adaptive optics. Component A1 was finally determined to be a spectroscopic binary.
The two component stars of NGC 3603-A1 circle each other every 3.77 days, and show brightness variations of about 0.3 magnitudes due to eclipses. The stars orbit very close to each other, separated by barely their own diameters and at or near to filling their roche lobe
In astronomy, the Roche lobe is the region around a star in a binary system within which orbiting material is gravitationally bound to that star. It is an approximately teardrop-shaped region bounded by a critical gravitational equipotential, wit ...
s.
The masses of A1a and A1b determined from the orbital parameters are and respectively. This makes them the two most massive stars directly measured, i.e. with their masses determined (using Keplerian orbits), and not estimated from models. The masses estimated from analysis of the physical properties are slightly higher at and .
Each component is a Wolf-Rayet (WR) star, with spectra dominated by strong broadened emission lines. Type WN6 indicates that ionised nitrogen lines are strong in comparison to ionised carbon lines, and the suffix ''h'' indicates that hydrogen is also seen in the spectrum. This type of WR star is not the classical stripped helium-burning aged star, but a young highly luminous object with CNO cycle
The CNO cycle (for carbon–nitrogen–oxygen; sometimes called Bethe–Weizsäcker cycle after Hans Albrecht Bethe and Carl Friedrich von Weizsäcker) is one of the two known sets of fusion reactions by which stars convert hydrogen to helium, ...
fusion products showing at the surface due to strong conventional and rotational mixing, and high mass loss rates from the atmosphere. The emission lines are generated in the stellar wind
A stellar wind is a flow of gas ejected from the upper atmosphere of a star. It is distinguished from the bipolar outflows characteristic of young stars by being less collimated, although stellar winds are not generally spherically symmetric.
D ...
and the photosphere
The photosphere is a star's outer shell from which light is radiated.
The term itself is derived from Ancient Greek roots, φῶς, φωτός/''phos, photos'' meaning "light" and σφαῖρα/''sphaira'' meaning "sphere", in reference to it ...
is completely hidden. The surface fraction of hydrogen is still estimated to be 60-70%.
Although the stars are very young, around 1.5 million years old, they have already lost a considerable fraction of their initial masses. The initial masses are estimated to have been and , meaning they have lost and respectively.
References
External links
*NASA Image of the day
{{DEFAULTSORT:NGC 3603-A1 Carina (constellation) Wolf–Rayet stars NGC 3603 097950A1 054948A1 Durchmusterung objects Eclipsing binaries