Planetary science

Where do White Dwarfs Come From?

Where a star ends up at the end of its life depends on the mass it was born with. Stars that have a lot of mass may end their lives as black holes or neutron stars. A low or medium mass star (with mass less than about 8 times the mass of our Sun) will become a white dwarf. A typical white dwarf is about as massive as the Sun, yet only slightly bigger than the Earth. This makes white dwarfs one of the densest forms of matter, surpassed only by neutron stars and black holes.

The major difference is due to the way in which they are formed.
1. White dwarfs are formed from the collapse of low mass stars, less than about 10 time the mass of the Sun. This star loses most of its mass in a wind, leaving behind a core that is less than 1.44 solar mass. On the other hand, neutron stars are formed in the catastrophic collapse of the core of a massive star.
Other differences follow:

The goal of planetary astronomy is to understand both the differences and the similarities (called comparative planetology) of the major objects in the solar system, including their atmospheres, surfaces, internal structures, and other factors, such as magnetic fields. The study is also aimed at understanding the sequence of events and dates that define the history of the solar system. When studying the planets of the solar system (see Figure 1 ), the first thing one might notice is that the characteristics of the planets suggest a division into two fundamental types: the terrestrial (Earth-like) and the gas-giant (Jupiter-like) planets. These characteristics are compared in Table 1 .

The key stage in the Birth of Giant Planets observed by Astronomers using the ALMA telescope. They have seen vast streams of gas, expected to be created by giant planets as they grow, a key stage in the birth of giant planets.    An artist’s impression of the disc of gas and cosmic dust around the young star HD 142527.    Image © ALMA (ESO/NAOJ/NRAO)/M. Kornmesser (ESO)/Nick Risinger

The key stage in the birth of Giant Planets observed by Atacama Large Millimeter/submillimeter Array (ALMA) telescope, around the young star HD 142527.

Planets forming around the young star HD 142527, are helping  the star itself continue to grow, resolving a longstanding mystery.

 researchers say.

More than 400 planets have now been found orbiting other stars, but Earth-sized planets – which may be the best habitats for life – have remained elusive.

NASA's orbiting Kepler telescope is designed to find them. It has been scrutinising 100,000 stars since April 2009, searching for telltale dips in starlight created when planets pass in front of their host stars.

A giant planet with the density of Styrofoam is one of a clutch of new exoplanets discovered by NASA's Kepler telescope. The planets are too hot to support life as we know it, but the discoveries, made during the telescope's first few weeks of operation, suggest Kepler is on the right track to find Earth's twins

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