A helioscope is an instrument used in observing the

Sun The Sun is the star at the centre of the Solar System. It is a massive, nearly perfect sphere of hot plasma, heated to incandescence by nuclear fusion reactions in its core, radiating the energy from its surface mainly as visible light a ...

and

sunspots Sunspots are temporary spots on the Sun's surface that are darker than the surrounding area. They are one of the most recognizable Solar phenomena and despite the fact that they are mostly visible in the solar photosphere they usually affe ...

. The helioscope was first used by

Benedetto Castelli Benedetto Castelli (1578 – 9 April 1643), born Antonio Castelli, was an Italians, Italian mathematician. Benedetto was his name in religion on entering the Benedictine Order in 1595. Life Born in Brescia, Castelli studied at the University of ...

(1578–1643) and refined by

Galileo Galilei Galileo di Vincenzo Bonaiuti de' Galilei (15 February 1564 – 8 January 1642), commonly referred to as Galileo Galilei ( , , ) or mononymously as Galileo, was an Italian astronomer, physicist and engineer, sometimes described as a poly ...

(1564–1642). The method involves projecting an image of the sun onto a white sheet of paper suspended in a darkened room with the use of a telescope. The first ''machina helioscopica'' or helioscope was designed by

Christoph Scheiner Christoph Scheiner (25 July 1573 (or 1575) – 18 June 1650) was a Jesuit priest, physicist and astronomer in Ingolstadt. Biography Augsburg/Dillingen: 1591–1605 Scheiner was born in Markt Wald near Mindelheim in Swabia, earlier margravate Burg ...

(1575 –1650) to assist his

sunspot Sunspots are temporary spots on the Sun's surface that are darker than the surrounding area. They are one of the most recognizable Solar phenomena and despite the fact that they are mostly visible in the solar photosphere they usually aff ...

observations. (Latin) In the context of modern astroparticle physics, the term ''helioscope'' can also refer to an experiment that seeks to observe hypothetical particles (such as the

axion An axion () is a hypothetical elementary particle originally theorized in 1978 independently by Frank Wilczek and Steven Weinberg as the Goldstone boson of Peccei–Quinn theory, which had been proposed in 1977 to solve the strong CP problem ...

) produced inside the sun. Examples of such helioscope experiments searching for axions include the

CERN Axion Solar Telescope The CERN Axion Solar Telescope (CAST) is an experiment in astroparticle physics to search for axions originating from the Sun. The experiment, sited at CERN in Switzerland, was commissioned in 1999 and came online in 2002 with the first data-t ...

and

International Axion Observatory The International Axion Observatory (IAXO) is a next-generation axion helioscope for the search of Axion, solar axions and axion-like particles (ALPs). It is the follow-up of the CERN Axion Solar Telescope, CERN Axion Solar Telescope (CAST), wh ...

References

Astronomical instruments Telescope types {{telescope-stub

See also

References