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A protoplanetary disk is a rotating circumstellar disc of dense gas and dust surrounding a young newly formed star, a T Tauri star, or Herbig Ae/Be star. The protoplanetary disk may not be considered an accretion disk ; while the two are similar, an accretion disk is hotter and spins much faster.
2MASS J04202144+2813491 (also known as Tau 042021) [3] [6] is an edge-on protoplanetary disk in the Taurus Molecular Cloud. [3]The star is hidden behind the edge-on disk. Early estimates found that it has a mass of 0.272 ±0.009 M ☉, [7] but a later study did find a higher mass of 0.3–0.4 M
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The protoplanetary disk around PDS 70 was first hypothesized in 1992 [14] and fully imaged in 2006 with phase-mask coronagraph on the VLT. [2] The disk has a radius of approximately 140 au . In 2012 a large gap (~ 65 au ) in the disk was discovered, which was thought to be caused by planetary formation.
First protoplanetary disc around a pulsar discovered 4U 0142+61: 2006 Brightest star with a protoplanetary disc Vega: 2005 Not confirmed See also.
Observations suggest that gas in protoplanetary disks orbiting young stars have lifetimes of a few to several million years. [1] If planets with masses of around an Earth mass or greater form while the gas is still present, the planets can exchange angular momentum with the surrounding gas in the protoplanetary disk so that their orbits change gradually.
These methods include stellar evolutionary models, membership in a given star cluster or system, fitting the star with the standard spectral and luminosity classification system, and the presence of a protoplanetary disk, among others. Nearly all of the methods of determining age require knowledge of the mass of the star, which can be known ...
When the Sun's orbit takes it outside the galactic disc, the influence of the galactic tide is weaker; as it re-enters the galactic disc, as it does every 20–25 million years, it comes under the influence of the far stronger "disc tides", which, according to mathematical models, increase the flux of Oort cloud comets into the Solar System by ...