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The light is usually in a particular frequency interval or band. Light curves can be periodic, as in the case of eclipsing binaries , Cepheid variables , other periodic variables, and transiting extrasolar planets ; or aperiodic , like the light curve of a nova , cataclysmic variable star , supernova , microlensing event , or binary as observed ...
The amount of penetration of UV relative to altitude in Earth's ozone. Next in frequency comes ultraviolet (UV). In frequency (and thus energy), UV rays sit between the violet end of the visible spectrum and the X-ray range. The UV wavelength spectrum ranges from 399 nm to 10 nm and is divided into 3 sections: UVA, UVB, and UVC.
Frequency division: Original signal is converted into square waves and then divided by a fixed factor (here: 16). Frequency division (FD) bat detectors synthesise a sound which is a fraction of the bat call frequencies, typically 1/10. This is done by converting the call into a square wave, otherwise called a zero crossing signal. This square ...
Atmospheric refraction of the light from a star is zero in the zenith, less than 1′ (one arc-minute) at 45° apparent altitude, and still only 5.3′ at 10° altitude; it quickly increases as altitude decreases, reaching 9.9′ at 5° altitude, 18.4′ at 2° altitude, and 35.4′ at the horizon; [4] all values are for 10 °C and 1013.25 hPa ...
Apparent magnitude, the brightness of an object as it appears in the night sky. Absolute magnitude, which measures the luminosity of an object (or reflected light for non-luminous objects like asteroids); it is the object's apparent magnitude as seen from a specific distance, conventionally 10 parsecs (32.6 light years).
A heterodyne bat detector does not give a very accurate measurement of the frequency of a bat call, One reason is that the call frequencies can easily vary by 1 kHz or more due to the doppler shift. To track these changes and to get a more precise frequency, a frequency division bat detector or a time expansion bat detector is used using a ...
The two oldest-known fossil skeletons of bats, unearthed in southwestern Wyoming and dating to at least 52 million years ago, are providing insight into the early evolution of these flying mammals ...
Without an atmosphere, a small star would have an apparent size, an "Airy disk", in a telescope image determined by diffraction and would be inversely proportional to the diameter of the telescope. However, when light enters the Earth's atmosphere , the different temperature layers and different wind speeds distort the light waves, leading to ...