MOST microsatellite reveals true nature of mysterious dust-forming Wolf-Rayet binary CV Ser

May 31, 2011

(PhysOrg.com) -- Using the Canadian MOST microsatellite, a team of researchers from the Universite de Montreal and the Centre de Recherche en Astrophysique du Quebec has made a stunning observation. As they'll report at this week's CASCA 2011 meeting in Ontario, Canada, the team has observed significant changes in the depth of the atmospheric eclipses in the 30-day binary WR+O system CV Serpentis, suggesting a never before seen change of mass-loss rate of the WR component by 70%.

Intrinsically luminous stars, like those in CV Ser, are the ecological motors of the Universe. They include both massive stars (i.e., those that explode as supernovae after driving strong winds all their lives) and medium-mass stars (about 1-8 M_Sun, that increase their luminosity by a factor of 1,000 only during their last dying stages before ejecting their extended outer layers in what astronomers call planetary nebulae). Massive stars are relatively rare, but they make up for this by their extreme luminosities and winds.

Among , the most interesting stage is arguably the last 10% in the lifetime of the star, when is used up and the star survives by much hotter He-burning. This is the so-called Wolf-Rayet stage, named after the two French astronomers that discovered the first stars of this type in 1867 using a small telescope in Paris equipped with a spectroscope. Wolf and Rayet were astonished by the intense, broad emission lines arising in their ultra-strong hot .

Towards the end of the WR phase, the products of He-burning (mainly ) eventually reach the stellar surface and are blown off in the wind. WR stars in this stage are called WC stars (in contrast to WN stars, where the N-rich products of H-burning are still spewing out). Some WC stars are known to produce copious quantities of carbon-based dust, i.e., conglomerates of many C atoms stuck together in amorphous ranging in size from a few to millions of atoms. How dust forms in general is one of the mysteries of the cosmos, but most astronomers believe that it requires high pressure and less than high temperatures, making it even more of a mystery how hot WC can do it. But they do, so it behooves astronomers to examine key cases for clues.

One key case is undoubtedly the sporadic dust-producing WC star in CV Ser. MOST was recently used to monitor CV Ser twice (2009 and 2010), revealing remarkable changes in the depths of the atmospheric eclipse that occurs every time the hot companion's light is absorbed as it passes through the inner dense WC wind. The remarkable, unprecedented 70% change in the WC mass-loss rate might be connected to dust formation.

Explore further: Astronomers find evidence of water clouds in brown dwarf atmosphere

Provided by Canadian Astronomical Society

4.4 /5 (5 votes)

Related Stories

Brilliant Star in a Colourful Neighbourhood

Jul 28, 2010

A spectacular new image from ESO's Wide Field Imager at the La Silla Observatory in Chile shows the brilliant and unusual star WR 22 and its colorful surroundings. WR 22 is a very hot and bright star that ...

Dust, blowing in the wind

Apr 25, 2011

(PhysOrg.com) -- Interstellar space contains vast quantities of dust that obscures our view while helping to catalyze the chemical reactions that turn atomic gases into complex molecular species. Most dust ...

The Stars behind the Curtain (w/ Video)

Feb 03, 2010

(PhysOrg.com) -- ESO is releasing a magnificent VLT image of the giant stellar nursery surrounding NGC 3603, in which stars are continuously being born. Embedded in this scenic nebula is one of the most luminous ...

Celestial Season's Greetings from Hubble

Dec 19, 2006

Swirls of gas and dust reside in this ethereal-looking region of star formation imaged by NASA's Hubble Space Telescope. This majestic view, located in the Large Magellanic Cloud (LMC), reveals a region where ...

Recommended for you

Evidence for supernovas near Earth

4 hours ago

Once every 50 years, more or less, a massive star explodes somewhere in the Milky Way. The resulting blast is terrifyingly powerful, pumping out more energy in a split second than the sun emits in a million ...

What lit up the universe?

11 hours ago

New research from UCL shows we will soon uncover the origin of the ultraviolet light that bathes the cosmos, helping scientists understand how galaxies were built.

Eta Carinae: Our Neighboring Superstars

19 hours ago

(Phys.org) —The Eta Carinae star system does not lack for superlatives. Not only does it contain one of the biggest and brightest stars in our galaxy, weighing at least 90 times the mass of the Sun, it ...

Best view yet of merging galaxies in distant universe

23 hours ago

Using the Atacama Large Millimeter/submillimeter Array, and other telescopes, an international team of astronomers has obtained the best view yet of a collision that took place between two galaxies when the ...

Image: Hubble stirs up galactic soup

Aug 25, 2014

(Phys.org) —This new NASA/ESA Hubble Space Telescope image shows a whole host of colorful and differently shaped galaxies; some bright and nearby, some fuzzy, and some so far from us they appear as small ...

User comments : 3

Adjust slider to filter visible comments by rank

Display comments: newest first

lengould100
5 / 5 (1) May 31, 2011
Cool.
omatumr
2 / 5 (3) May 31, 2011
Towards the end of the WR phase, the products of He-burning (mainly carbon atoms) " . . .


That statement is incorrect.

Laboratory and theoretical studies both show that burning of Helium (He-4) produces mostly Oxygen (O-16), rather than Carbon (C-12).

Nobel Laureate William A. Fowler commented on this problem.

His statement is quoted and addressed on page 2 of this preprint ["Neutron Repulsion", The APEIRON Journal, in press, 19 pages (2011)]

http://arxiv.org/...2.1499v1

With kind regards,
Oliver K. Manuel
Former NASA Principal
Investigator for Apollo
LKD
not rated yet Jun 01, 2011
Carbon needs to form first to produce Oxygen when reacting with Helium. :(