This image illustrates how a light echo works, and how an optical illusion of material moving outward is created.

This composite image from NASA Spitzer Space Telescope shows the remnant of a star that exploded, called Cassiopeia A center and its surrounding light echoes -- dances of light through dusty clouds, created when stars blast apart.

"Light Echo" Illuminates Dust Around Supergiant Star V838 Monocerotis (V838 Mon) Credit: NASA and The Hubble Heritage Team (AURA/STScI) The Hubble Space Telescope is a project of international cooperation between NASA and the European Space Agency. NASA's Goddard Space Flight Center manages the telescope. The Space Telescope Science Institute conducts Hubble science operations. Goddard is responsible for HST project management, including mission and science operations, servicing missions, and all associated development activities. To learn more about the Hubble Space Telescope go here: <a href="http://www.nasa.gov/mission_pages/hubble/main/index.html" rel="nofollow">www.nasa.gov/mission_pages/hubble/main/index.html</a> <a href="http://www.nasa.gov/centers/goddard/home/index.html" rel="nofollow">NASA Goddard Space Flight Center</a> is home to the nation's largest organization of combined scientists, engineers and technologists that build spacecraft, instruments and new technology to study the Earth, the sun, our solar system, and the universe. Follow us on <a href="http://twitter.com/NASA_GoddardPix" rel="nofollow">Twitter</a> Join us on <a href="http://www.facebook.com/pages/Greenbelt-MD/NASA-Goddard/395013845897?ref=tsd" rel="nofollow">Facebook</a>

History of Hubble Space Telescope (HST)

This series of photos, captured by the NASA Hubble Space Telescope's (HST) Advanced Camera for Surveys from May to December 2002, dramatically demonstrates the reverberation of light through space caused by an unusual stellar outburst in January 2002. A burst of light from the bizarre star is spreading into space and reflecting off of surrounding circumstellar dust. As different parts are sequentially illuminated, the appearance of the dust changes. This effect is referred to as a "light echo". The red star at the center of the eyeball like feature is the unusual erupting super giant called V838 Monocerotis, or V Mon, located about 20,000 light-years away in the winter constellation Monoceros (the Unicorn). During its outburst, the star brightened to more than 600,000 times our Sun's luminosity. The circular feature has now expanded to slightly larger than the angular size of Jupiter on the sky, and will continue to expand for several more years until the light from the back side of the nebula begins to arrive. The light echo will then give the illusion of contracting, until it finally disappears by the end of the decade.

Listed as Cassiopeia A, this remnant of the supernova is one of the brightest radio sources in the known universe. More recently, NASA WISE telescope detected infrared echoes of the flash of light rippling outwards from the supernova.

Echoes of a Stellar Ending

History of Hubble Space Telescope (HST)

This photo, captured by the NASA Hubble Space Telescope's (HST) Advanced Camera for Surveys, is Hubble's latest view of an expanding halo of light around the distant star V838 Monocerotis, or V Mon, caused by an unusual stellar outburst that occurred back in January 2002. A burst of light from the bizarre star is spreading into space and reflecting off of surrounding circumstellar dust. As different parts are sequentially illuminated, the appearance of the dust changes. This effect is referred to as a "light echo". Located about 20,000 light-years away in the winter constellation Monoceros (the Unicorn), the star brightened to more than 600,000 times our Sun's luminosity. The light echo gives the illusion of contracting, until it finally disappears by the end of the decade.

Echo Mapping in a Black Hole Accretion Disk and Torus (Animation)

This animation shows the events that serve as the basis of an astrophysics technique called "echo mapping," also known as reverberation mapping. At center is a supermassive black hole surrounded by a disk of material called an accretion disk. As the disk gets brighter it sometimes even releases short flares of visible light. Blue arrows show the light from this flash traveling away from the black hole, both toward an observer on Earth and toward an enormous, doughnut-shaped structure (called a torus) made of dust. The light gets absorbed, causing the dust to heat up and release infrared light. This brightening of the dust is a direct response to — or, one might, say an "echo" — of the changes happening in the disk. Red arrows show this light traveling away from the galaxy, in the same direction as the initial flash of visible light. Thus an observer would see the visible light first, and (with the right equipment) the infrared light later. Astronomers have previously proposed using echo mapping as a means of measuring distances to cosmic objects. If scientists can observe both the initial flare of visible light and the subsequent infrared brightening in the dust, they could in theory use that information to measure the disk's luminosity, which could then be used to measure the distance to that galaxy by comparing it to the galaxy's brightness as seen from Earth. The temperature in the part of the disk closest to the black hole can reach tens of thousands of degrees but decreases with distance. When it reaches about 2,200 degrees Fahrenheit (1,200 Celsius), it is cool enough for dust to form. The more luminous the disk, the farther away from it the dust forms and the longer it takes light from the disk to reach the dust and produce the "echo." The distance from the accretion disk to the inside of the dust doughnut can be billions or trillions of miles. Even light, traveling at 186,000 miles (300,000 kilometers) per second, can take months or years to cross it. NASA's Near Earth Object Wide Field Infrared Survey Explorer (NEOWISE), previously named WISE, surveys the entire sky about once every six months and is on track to complete 16 such surveys by the end of 2020, providing astronomers with repeated opportunities to observe galaxies and look for signs of those light echoes. A study using data from WISE measured the luminosity of over 500 black hole accretion disks using echo mapping, but the subsequent distance measurements lacked precision compared to other distance measuring techniques. Additional data and an improved understanding of dust torus dynamics could improve those measurements. Movie available at https://photojournal.jpl.nasa.gov/catalog/PIA23866

Hubble Watches Super Star Create Holiday Light Show

This festive NASA Hubble Space Telescope image resembles a holiday wreath made of sparkling lights. The bright southern hemisphere star RS Puppis, at the center of the image, is swaddled in a gossamer cocoon of reflective dust illuminated by the glittering star. The super star is ten times more massive than our sun and 200 times larger. RS Puppis rhythmically brightens and dims over a six-week cycle. It is one of the most luminous in the class of so-called Cepheid variable stars. Its average intrinsic brightness is 15,000 times greater than our sun’s luminosity. The nebula flickers in brightness as pulses of light from the Cepheid propagate outwards. Hubble took a series of photos of light flashes rippling across the nebula in a phenomenon known as a "light echo." Even though light travels through space fast enough to span the gap between Earth and the moon in a little over a second, the nebula is so large that reflected light can actually be photographed traversing the nebula. By observing the fluctuation of light in RS Puppis itself, as well as recording the faint reflections of light pulses moving across the nebula, astronomers are able to measure these light echoes and pin down a very accurate distance. The distance to RS Puppis has been narrowed down to 6,500 light-years (with a margin of error of only one percent). The Hubble Space Telescope is a project of international cooperation between NASA and the European Space Agency. NASA's Goddard Space Flight Center in Greenbelt, Md., manages the telescope. The Space Telescope Science Institute (STScI) in Baltimore, Md., conducts Hubble science operations. STScI is operated by the Association of Universities for Research in Astronomy, Inc., in Washington, D.C. Acknowledgment: H. Bond (STScI and Pennsylvania State University) <a href="http://www.nasa.gov/audience/formedia/features/MP_Photo_Guidelines.html" rel="nofollow">NASA image use policy.</a> <a href="http://www.nasa.gov/centers/goddard/home/index.html" rel="nofollow">NASA Goddard Space Flight Center</a> enables NASA’s mission through four scientific endeavors: Earth Science, Heliophysics, Solar System Exploration, and Astrophysics. Goddard plays a leading role in NASA’s accomplishments by contributing compelling scientific knowledge to advance the Agency’s mission. Follow us on <a href="http://twitter.com/NASA_GoddardPix" rel="nofollow">Twitter</a> Like us on <a href="http://www.facebook.com/pages/Greenbelt-MD/NASA-Goddard/395013845897?ref=tsd" rel="nofollow">Facebook</a> Find us on <a href="http://instagram.com/nasagoddard?vm=grid" rel="nofollow">Instagram</a>

Infrared Echoes of a Black Hole Eating a Star Illustration

This illustration shows a glowing stream of material from a star as it is being devoured by a supermassive black hole in a tidal disruption flare. When a star passes within a certain distance of a black hole -- close enough to be gravitationally disrupted -- the stellar material gets stretched and compressed as it falls into the black hole. In the process of being accreted, the gas heats up and creates a lot of optical and ultraviolet light, which destroys nearby dust but merely heats dust further out. The farther dust that is heated emits a large amount of infrared light. In recent years, a few dozen such flares have been discovered, but they are not well understood. Astronomers gained new insights into tidal disruption flares thanks to data from NASA's Wide-field Infrared Survey Explorer (WISE). Studies using WISE data characterized tidal disruption flares by studying how surrounding dust absorbs and re-emits their light, like echoes. This approach allowed scientists to measure the energy of flares from stellar tidal disruption events more precisely than ever before. http://photojournal.jpl.nasa.gov/catalog/PIA20027

Ingenuity Captures Perseverance at Belva Crater

This image of NASA's Perseverance Mars rover at the rim of Belva Crater was taken by the agency's Ingenuity Mars Helicopter during the rotorcraft's 51st flight on April 22, 2023, the 772nd Martian day, or sol, of the rover's mission. At the time the image was taken, the helicopter was at an altitude of about 40 feet (12 meters). The rover is in the upper left of the image, parked at a light-toned rocky outcrop the science team is calling "Echo Creek." Perseverance's tracks can be seen extending from its location to the upper-right side of image. The helicopter's shadow can be seen on the rocky hill in the foreground, just to the right and below the image's center. The hill, designated "Mount Julian" by the science team, is a planned future stop for the rover. A small triangular piece of debris from the rover's entry, descent, and landing system can be seen at the lower center of image. https://photojournal.jpl.nasa.gov/catalog/PIA25884

The Evolution of a Planet-Forming Disk Artist Concept Animation

This frame from an animation shows the evolution of a planet-forming disk around a star. Initially, the young disk is bright and thick with dust, providing raw materials for building planets. In the first 10 million years or so, gaps appear within the disk as newborn planets coalesce out of the dust, clearing out a path. In time, this planetary "debris disk" thins out as gravitational interactions with numerous planets slowly sweep away the dust. Steady pressure from the starlight and solar winds also blows out the dust. After a few billion years, only a thin ring remains in the outermost reaches of the system, a faint echo of the once-brilliant disk. Our own solar system has a similar debris disk -- a ring of comets called the Kuiper Belt. Leftover dust in the inner portion of the solar system is known as "zodiacal dust." Bright, young disks can be imaged directly by visible-light telescopes, such as NASA's Hubble Space Telescope. Older, fainter debris disks can be detected only by infrared telescopes like NASA's Spitzer Space Telescope, which sense the disks' dim heat. http://photojournal.jpl.nasa.gov/catalog/PIA07099

Perseverance Takes in View at Belva Crater

This view of the interior of Belva Crater was generated using data collected by the Mastcam-Z instrument aboard NASA's Perseverance Mars rover on April 22, 2023, the 772nd Martian day, or sol, of the mission. When the 152 individual images that make up this mosaic were taken, the rover was parked at the west side of the crater's rim, on a light-toned rocky outcrop the science team is calling "Echo Creek." Belva Crater is about 0.6 miles (0.9 kilometers) in diameter. The view here is looking across the crater towards the distant east-northeast wall of the much-larger Jezero Crater (center of the image), some 25 miles (40 kilometers) away. Impact craters like Belva can offer grand views and contain vertical cuts that provide important clues to the geologic history of the area. The mosaic shows multiple locations of bedrock exposed in vertical cross-section. One of these exposed sections of bedrock (located on the hill seen between the 60 and 75 hashmarks) is angled steeply downward and is nearly 65 feet (20 meters) tall. Called "dipping beds," such a steeply angled bedrock section could indicate the presence of a large Martian sandbar made of sediment that billions of years ago was deposited by a river flowing into the lake that Jezero Crater once held. The most distant point on Belva Crater's rim (just to the left of center in the mosaic) is about 3,500 feet (1,060 meters) away from the rover. The large boulder seen in the far right of the mosaic is about 65 feet (20 meters) away and is about 5 feet (1.5 meters) in diameter. Arizona State University leads the operations of the Mastcam-Z instrument, working in collaboration with Malin Space Science Systems in San Diego, on the design, fabrication, testing, and operation of the cameras, and in collaboration with the Niels Bohr Institute of the University of Copenhagen on the design, fabrication, and testing of the calibration targets. A key objective for Perseverance's mission on Mars is astrobiology, including the search for signs of ancient microbial life. The rover will characterize the planet's geology and past climate, pave the way for human exploration of the Red Planet, and be the first mission to collect and cache Martian rock and regolith (broken rock and dust). Subsequent NASA missions, in cooperation with ESA (European Space Agency), would send spacecraft to Mars to collect these sealed samples from the surface and return them to Earth for in-depth analysis. The Mars 2020 Perseverance mission is part of NASA's Moon to Mars exploration approach, which includes Artemis missions to the Moon that will help prepare for human exploration of the Red Planet. https://photojournal.jpl.nasa.gov/catalog/PIA25889