GALEX

A special tool flies in space.

It looks at light we cannot see. This light helps find new stars. It shows how stars are born.

The tool looks at many far-off groups of stars. These groups are called galaxies. It can see many galaxies at once.

It uses sun power to work. Four small panels catch light from the sun. This gives the tool power.

The tool worked for many years. It will stay in space for a long time. It is a great way to study the sky.

GALEX is a special space telescope. It orbits the Earth to look at the sky. Most people cannot see ultraviolet light. This is a type of light that is invisible to our eyes. GALEX uses this light to study the history of stars. It helps us learn how stars are born and how they die.

The telescope looks at galaxies. These are huge groups of stars. GALEX wants to see how galaxies change over time. It can see back about 10 billion years into the past. This helps us see how the universe grew. The telescope uses four solar cells to get power. These cells catch light from the sun.

GALEX launched on April 28, 2003. It was meant to work for 29 months. However, it worked for almost nine years! It studied many things. It made maps of the sky. It also looked at 200 galaxies near our own Milky Way. Scientists used its data to learn about black holes and dark matter. The telescope will stay in orbit until at least 2068.

Caption: This shows how much of the sky GALEX can see at once.

GALEX is a special space telescope that orbits the Earth. Its full name is the Galaxy Evolution Explorer. This tool was built to study the history of star formation. It looks at the universe using ultraviolet light. This light is invisible to our eyes. By using this light, scientists can see how galaxies change over time. GALEX helps us understand how stars are born and how they die.

The telescope works by catching ultraviolet light from far away. It uses a special mirror system called a Ritchey–Chrétien telescope. Inside, a beam-splitter directs the light to two different detectors. One detector sees Near UV light. The other detector sees Far UV light. These detectors use microchannel plates to multiply electrons. This process helps the telescope see very faint objects. A rotating wheel with a grism also helps it study light in detail.

NASA launched GALEX on April 28, 2003. It was carried into space by a Pegasus launch vehicle. The mission was originally planned to last only 29 months. However, it worked much longer than anyone expected. It stayed active for almost nine years. In 2012, NASA put the spacecraft into standby mode. Later, in 2013, the mission was officially decommissioned.

GALEX has many important facts and numbers. The spacecraft uses four solar cells to get power. These cells provide nearly 300 watts of energy. The mission cost NASA about $150.6 million. The telescope can see light from 135 to 280 nanometers. It can look back at about 10 billion years of history. This covers 80% of the way back to the Big Bang. The spacecraft will stay in orbit until at least 2068.

You can think of GALEX as a time machine for light. By looking at distant galaxies, it sees things as they were long ago. It works with other famous tools like the Hubble Space Telescope. It also joined the GOALS survey with the Spitzer and Chandra telescopes. These tools work together to map the sky. GALEX helps us see the invisible parts of our universe. It shows us how the stars we see today first began.

The Galaxy Evolution Explorer, known as GALEX, is a specialized NASA space telescope. It was designed to observe the universe using ultraviolet wavelengths. By studying this specific light, astronomers can measure the history of star formation. This mission helps us understand how galaxies change and evolve over vast periods of time. GALEX also provides data to help characterize mysterious phenomena like dark matter and black holes. It serves as a vital tool for uncovering the secrets of the early universe.

The telescope operates using a Modified Ritchey–Chrétien design. This system uses a primary mirror and a secondary mirror to collect light. A rotating grism, which is a tool combining a grating and a prism, allows for spectral composition. To separate different types of light, the spacecraft uses a UV light dichroic beam-splitter. This component is the first of its kind ever flown in space. It directs photons to two specific microchannel plate detectors. One detector captures Near UV light between 175 and 280 nanometers. The other captures Far UV light between 135 and 174 nanometers.

Inside these detectors, the light creates photoelectrons. These electrons are multiplied by a microchannel plate. An anode grid then detects the electrons. This grid can determine the exact position of an electron impact by measuring the time delay of pulses. The spacecraft itself is three-axis stabilized to stay steady. It receives nearly 300 watts of power from four fixed gallium arsenide solar cells. These cells provide the energy needed to run the complex instruments in orbit.

GALEX conducted its science through eight distinct surveys. These were divided into two main categories. The first category is the local universe investigation. This includes an all-sky imaging survey to map star formation. It also includes a nearby galaxy survey of about 200 galaxies. Additionally, there are wide-field and medium spectroscopic surveys to analyze light wavelengths. The second category is the star formation history investigation. This looks at the distant universe through deep imaging and spectroscopic surveys. These surveys allow scientists to see much further back in time.

The mission began on April 28, 2003. An air-launched Pegasus vehicle placed the craft into a circular orbit. This orbit is inclined at 29.00 degrees to the Earth's equator. The first observation occurred on May 21, 2003, in the constellation Hercules. This area was chosen because it was overhead the Space Shuttle Columbia. The mission was originally planned to last only 29 months. However, the mission was extended three times. Observation operations lasted for almost nine years before standby mode in 2012.

NASA's total life-cycle cost for the mission was US$150.6 million. In 2009, the Far UV detector stopped functioning correctly. Despite this, the mission continued to provide valuable data. In 2011, NASA reduced financial support for the project. Control of the spacecraft was later transferred to the California Institute of Technology. This transfer followed the Stevenson-Wydler Technology Innovation Act. This law allows the government to give excess research equipment to educational institutions. GALEX was officially decommissioned in June 2013.

The scientific impact of GALEX is massive. It can observe galaxies across a redshift range of Z between 0 and 2. This allows the telescope to study about 10 billion years of cosmic history. This covers 80% of the way back to the Big Bang. GALEX helps determine how quickly stars form and how they die. It also helps scientists find ultraviolet bright quasars. These quasars act as background sources for other telescopes like the Hubble Space Telescope. This helps researchers probe the gases that form galaxies.

GALEX does not work alone in the vastness of space. It participated in the GOALS survey. This study looked at Luminous Infrared Galaxies at multiple wavelengths. To do this, GALEX partnered with other famous observatories. These included the Spitzer Space Telescope, the Chandra X-ray Observatory, and the Hubble Space Telescope. By combining ultraviolet data with X-ray and infrared data, scientists get a complete picture. The spacecraft will remain in orbit until at least 2068. Even after its mission ends, it will continue to circle the Earth for many years.