Astronomers determined the mass of the burning star directly using a phenomenon known as it gravitational lens effect. An international team, led by Peter McGill of the University of Cambridge (UK), used data from two telescopes to measure how light from a distant star was deflected by the white dwarf star LAWD 37, causing the distant star to temporarily move away from the star’s position and appear to have changed. This is the first time this effect has been observed with a star other than our Sun, and the first time the mass of such a star has been directly measured (Monthly Notices of the Royal Astronomical Society2 February).
LAWD 37 is a white dwarf, the compact remnant of a star like our sun. When a sun-like star runs out of nuclear fuel, it swells and blasts its outer layers into space. All that remains is its hot and compressed core. Under these conditions, matter as we know it behaves very differently and turns into a thing deteriorate command is called. LAWD 37 has been extensively researched because it is relatively close. Located 15 light-years away in the southern constellation Venus, the white dwarf is the remnant of a star that died more than a billion years ago.
Mass is one of the most important factors in the evolution of a star. For most stellar objects, astronomers derive mass indirectly, based on strong and often untested model assumptions. In the rare cases where mass can be deduced directly, the star must have a companion, as in the case of a binary star system. But for individual objects, such as LAWD 37, other methods are needed to determine mass.
McGill and his colleagues have now succeeded — together with the European Space Agency’s (ESA) Gaia Space Telescope and the NASA/ESA Hubble Space Telescope — in making the first precise mass determination of LAWD. Using Gaia, astronomers have been able to predict the motion of LAWD 37 and pinpoint the point at which it will be close enough to the background star to cause the desired lensing effect. With this information, astronomers were able to point the Hubble Space Telescope to the right place in the sky at the right time to observe the phenomenon that occurred in November 2019.
From the strength of the lens impact, which is proportional to the mass of the object acting as the lens, the mass of LAWD 37 has now been calculated to be 0.56 solar masses. This agrees well with previous theoretical predictions for the mass of this white dwarf, and confirms the reliability of existing theories about the evolution of these objects. (EE)
Astronomers have observed the bending of light around a solitary white dwarf
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