kosmos: V838 Monocerotis

Evidence: 100 • authority: 72

V838 Monocerotis (Nova Monocerotis 2002) is a cataclysmic binary star in the constellation Monoceros about 19,000 light years (6 kpc) from the Sun. The previously unremarked star was observed in early 2002 experiencing a major outburst, and was one of the largest known stars for a short period following the outburst. Originally believed to be a typical nova eruption, it was then identified as the first of a new class of eruptive variables known as luminous red novae. The reason for the outburst is still uncertain, but is thought to have been a merger of two stars within a triple system. The eruption occurred on one of two B3 main sequence stars in a close binary orbit. The erupting star app…

Evidence: 45 • authority: 92

An energetic stellar outburst accompanied by circumstellar light echoes.. Some classes of stars, including novae and supernovae, undergo explosive outbursts that eject stellar material into space. In 2002, the previously unknown variable star V838 Monocerotis brightened suddenly by a factor of approximately 10(4). Unlike a supernova or nova, it did not explosively eject its outer layers; rather, it simply expanded to become a cool supergiant with a moderate-velocity stellar wind. Superluminal light echoes were discovered as light from the outburst propagated into the surrounding, pre-existing circumstellar dust. Here we report high-resolution imaging and polarimetry of those light echoes, w…

Evidence: 38 • authority: 72

M31 RV is a possible red cataclysmic variable star located in the Andromeda Galaxy (M31) that experienced an outburst in 1988, which was similar to the outburst V838 Monocerotis experienced in 2002. At peak brightness, M31 RV was the most luminous red supergiant in the Local Group. Such objects have been called luminous red novae or intermediate-luminosity red transients. During the outburst, both V838 Mon and M31 RV reached a maximum absolute visual magnitude of -9.8. In 2006, the area around M31 RV was observed using the Hubble Space Telescope, but only red giants were seen. Most likely the star either became too dim for Hubble to see, the star is a companion of one of the red giants, or…

Evidence: 20 • authority: 72

Below are lists of the largest stars currently known, ordered by radius and separated into categories by galaxy. The unit of measurement used is the radius of the Sun (approximately 695,700 km; 432,300 mi).

Evidence: — • authority: 72

A variable star is a star whose brightness as seen from Earth (its apparent magnitude) changes systematically with time. This variation may be caused by a change in emitted light or by something partly blocking the light, so variable stars are classified as either: Intrinsic variables, whose inherent luminosity changes; for example, because the star swells and shrinks. Extrinsic variables, whose apparent changes in brightness are due to changes in the amount of their light that can reach Earth; for example, because the star has an orbiting companion that sometimes eclipses it. Depending on the type of star system, this variation can include cyclical, irregular, fluctuating, or transient beh…

Evidence: — • authority: 72

In astronomy, stellar classification is the classification of stars based on their spectral characteristics. Electromagnetic radiation from the star is analyzed by splitting it with a prism or diffraction grating into a spectrum exhibiting the rainbow of colors interspersed with spectral lines. Each line indicates a particular chemical element or molecule, with the line strength indicating the abundance of that element. The strengths of the different spectral lines vary mainly due to the temperature of the photosphere, although in some cases there are true abundance differences. The spectral class of a star is a short code primarily summarizing the ionization state, giving an objective meas…