a process in which distortions (like those from Earth’s atmosphere) are removed from a telescope’s image in real time. First, a wavefront sensor uses a reference star to measure the distortions that are occurring, and the distortions are then removed with a phase corrector.
the ability of an instrument, such as a telescope, to distinguish objects that are very close to each other. The angular resolution of an instrument is the smallest angular separation at which the instrument can observe two neighboring objects as two separate objects.
the onboard electronics used for operating a spacecraft, including communications, navigation, and electronic flight management systems
a region of space containing a huge amount of mass compacted into an extremely small volume. A black hole’s gravitational influence is so strong that nothing, not even light, can escape from it.
Cepheid variable star
a type of pulsating star whose light and energy output vary noticeably over a set period of time. The time period over which the star varies is directly related to its light output or luminosity, making these stars useful standard candles for measuring intergalactic distances.
the residual energy in empty space which is causing the expansion of the universe to accelerate
the reduction or elimination of some objectives, performance requirements, or capabilities compared to those in an earlier baseline plan
a device or tool connected to the end of a robot arm
the targeting devices aboard HST that lock onto “guide stars” and measure their positions relative to the object being viewed. Adjustments based on these precise readings keep Hubble pointed in the right direction.
the amount of something (such as radiation) passing through a surface per unit time
a spinning wheel mounted on a non-stationary frame that stabilizes and points a space-based observatory. This spinning wheel resists applied external forces and tends to retain its original orientation in space.
a number that expresses the rate at which the universe expands with time. H0 appears to be between 60 and 75 kilometers per second per million parsecs. (One parsec is equal to 3.26 light-years and 3.085678 × 1013 kilometers, or approximately 18 trillion miles.)
Milky Way Galaxy
The Milky Way, a spiral galaxy, is the home of Earth, the Sun, and the rest of our solar system.
any man-made object, or portions thereof, in orbit about Earth which no longer serves a useful purpose
an expanding shell of glowing gas expelled by a star late in its life
matter that is beginning to come together to form a star and its collection of orbiting planets
the brightest type of active galactic nucleus, believed to be powered by a supermassive black hole. The word “quasar” is derived from quasi-stellar radio source, because this type of object was first identified as a kind of radio source.
an instrument or instrument system for measuring the distance, for example, between two spacecraft as they approach one another
one of four spinning wheels that work by rotating a large flywheel up to 3000 rpm or braking it to exchange momentum with the spacecraft which will make HST turn. The flywheels work together to make the observatory rotate either more rapidly or less rapidly toward a new target.
an apparent shift toward longer wavelengths of spectral lines in the radiation emitted by an object caused by motion of the emitting object away from the observer
an example of optical aberration, a deviation from perfect image formation in which light from different parts of a mirror or lens is brought to different foci
the explosive death of a massive star whose energy output causes its expanding gases to glow brightly for weeks or months
the control of robots from a distance
a general-purpose reliability distribution used to model material strength and times-to-failure of electronic and mechanical components, equipment, or systems