Monday, January 30, 2023

Exploring The Turbulent Tarantula Nebula | Hubble

Exploring The Turbulent Tarantula Nebula | Hubble


A snapshot of the Tarantula Nebula (also known as 30 Doradus) is the most recent from the NASA/European Space Agency Hubble Space Telescope. The Tarantula Nebula is a large star-forming region of ionised hydrogen gas that lies 161,000 light years from Earth in the Large Magellanic Cloud, and its turbulent clouds of gas and dust can be seen swirling between the region’s bright, newly-formed stars.

Image Description: Wispy, nebulous clouds extend from the lower-left of the image. At the top and right the dark background of space can be seen through the sparse nebula. Along the left and in the corner are many layers of brightly-colored gas and dark, obscuring dust. A cluster of small, bright blue stars in the same corner expands out across the image. Many much smaller stars cover the background.

The Tarantula Nebula is a familiar site for Hubble. It is the brightest star-forming region in our galactic neighborhood and home to the hottest, most massive stars known. This makes it a perfect natural laboratory in which to test out theories of star formation and evolution, and a rich variety of Hubble images of this region have been released to the public in recent years. The NASA/European Space Agency/Canadian Space Agency James Webb Space Telescope also recently delved into this region, revealing thousands of never-before-seen young stars.

This new image combines data from two different observing proposals. The first was designed to explore the properties of the dust grains that exist in the void between stars and which make up the dark clouds winding through this image. This proposal, which astronomers named Scylla, complements another Hubble observing proposal called Ulysses and is revealing how interstellar dust interacts with starlight in a variety of environments. This image also incorporates data from an observing program studying star formation in conditions similar to the early Universe, as well as cataloguing the stars of the Tarantula Nebula for future science with Webb.


Credit: European Space Agency (ESA)/Hubble & NASA, C. Murray, E. Sabbi

Acknowledgement: Y.-H. Chu

Release Date: Jan. 30, 2023


#NASA #ESA #Astronomy #Space #Science #Hubble #Nebula #30Doradus #TarantulaNebula #Dorado #Constellation #LMC #Galaxy #Cosmos #Universe #SpaceTelescope #HST #STScI #GSFC #UnitedStates #Europe #STEM #Education

Sunday, January 29, 2023

Jupiter’s Great Red Spot | Hubble Space Telescope

Jupiter’s Great Red Spot | Hubble Space Telescope

Hubblecast 123 Light: This video highlights Jupiter’s trademark spot and observations made of the feature by the NASA/European Space Agency Hubble Space Telescope that demonstrate that the spot has shrunk over time.


Credits:

Directed by: Bethany Downer

Editing: Nico Bartmann

Web and technical support: Mathias André and Raquel Yumi Shida

Written by: Bethany Downer  

Footage and photos:     European Space Agency (ESA), NASA, A. Simon, M.H. Wong, M. Kornmesser, H. Hammel, R. Beebe

Duration: 1 minute, 30 seconds

Release Date: Aug. 8, 2019


#NASA #Hubble #Astronomy #Space #Science #Planet #Jupiter #Atmosphere #GRS #GreatRedSpot #SolarSystem #MilkyWayGalaxy #Cosmos #Universe #HST #SpaceTelescope #ESA #Europe #GSFC #STScI #UnitedStates #STEM #Education #Model #Visualization #HD #Video

A Close-Up Look at Jupiter’s Dynamic Atmosphere | Hubble

A Close-Up Look at Jupiter’s Dynamic Atmosphere | Hubble


The NASA/European Space Agency Hubble Space Telescope reveals the intricate, detailed beauty of Jupiter’s clouds in this image from Hubble’s Wide Field Camera 3, when the planet was 644 million kilometers from Earth. The image features the distinct bands of roiling clouds that are characteristic of Jupiter’s atmosphere and represents a stretched-out map of the entire planet.

Researchers combined several Hubble exposures to create this flat map, which excludes the polar regions (above 80 degrees latitude). These observations of Jupiter form part of the Outer Planet Atmospheres Legacy (OPAL) program.


Credit: NASA, European Space Agency (ESA), A. Simon (Goddard Space Flight Center), and M.H. Wong (University of California, Berkeley)

Capture Date: June 27, 2019

Release Date: Aug. 8, 2019


#NASA #Hubble #Astronomy #Space #Science #Planet #Jupiter #Atmosphere #GRS #GreatRedSpot #SolarSystem #MilkyWayGalaxy #Cosmos #Universe #HST #SpaceTelescope #ESA #Europe #GSFC #STScI #UnitedStates #STEM #Education

Global Model of Jupiter | NASA & European Space Agency

Global Model of Jupiter | NASA & European Space Agency

This three-dimensional model of Jupiter was computer-generated from a new global map of the planet that was taken by the NASA/European Space Agency Hubble Space Telescope’s Wide Field Camera 3 when the planet was 644 million kilometers from Earth.


Credit: NASA, ESA, A. Simon (Goddard Space Flight Center), and M.H. Wong (University of California, Berkeley), M. Kornmesser

Duration: 24 seconds

Capture Date: June 27, 2019 

Release Date: Aug 8, 2019


#NASA #Hubble #Astronomy #Space #Science #Planet #Jupiter #Atmosphere #GRS #GreatRedSpot #SolarSystem #MilkyWayGalaxy #Cosmos #Universe #HST #SpaceTelescope #ESA #Europe #GSFC #STScI #UnitedStates #STEM #Education #Model #Visualization #HD #Video

Zooming into the Great Red Spot of Jupiter | Hubble

Zooming into the Great Red Spot of Jupiter | Hubble

This video is a pan across the surface of Jupiter, featuring a zoom into the planet's trademark Great Red Spot.

This image was taken by the NASA/ESA Hubble Space Telescope’s Wide Field Camera 3, when the planet was 644 million kilometers from Earth. The image highlights the Great Red Spot in a more intense color palette in the clouds swirling in the planet’s turbulent atmosphere than seen in previous years.


Credit: NASA, European Space Agency (ESA), A. Simon (Goddard Space Flight Center), and M.H. Wong (University of California, Berkeley)   

Duration: 40 seconds

Capture Date: June 27, 2019 

Release Date: Aug. 12, 2019


#NASA #Hubble #Astronomy #Space #Science #Planet #Jupiter #Atmosphere #GRS #GreatRedSpot #SolarSystem #MilkyWayGalaxy #Cosmos #Universe #HST #SpaceTelescope #ESA #Europe #GSFC #STScI #UnitedStates #STEM #Education #HD #Video

Jupiter’s Colorful Palette | Hubble

Jupiter’s Colorful Palette | Hubble


The NASA/European Space Agency Hubble Space Telescope reveals the intricate, detailed beauty of Jupiter’s clouds in this image by Hubble’s Wide Field Camera 3, when the planet was 644 million kilometers from Earth. The image features the planet’s trademark Great Red Spot and a more intense color palette in the clouds swirling in the planet’s turbulent atmosphere than seen in previous years.

The observations of Jupiter form part of the Outer Planet Atmospheres Legacy (OPAL) program.


Credit: NASA, European Space Agency (ESA), A. Simon (Goddard Space Flight Center), and M.H. Wong (University of California, Berkeley)

Image Date: June 27, 2019

Release Date: August 8, 2019


#NASA #Hubble #Astronomy #Space #Science #Planet #Jupiter #Atmosphere #GRS #GreatRedSpot #SolarSystem #MilkyWayGalaxy #Cosmos #Universe #HST #SpaceTelescope #ESA #Europe #GSFC #STScI #UnitedStates #STEM #Education

A Galactic Triplet: Interacting Galaxies | Hubble

 A Galactic Triplet: Interacting Galaxies | Hubble


A dramatic triplet of galaxies takes center stage in this image from the NASA/European Space Agency Hubble Space Telescope, which captures a three-way gravitational tug-of-war between interacting galaxies. This system—known as Arp 195—is featured in the Atlas of Peculiar Galaxies, a list which showcases some of the weirder and more wonderful galaxies in the universe.

Observing time with the Hubble Space Telescope is extremely valuable, so astronomers do not want to waste a second. The schedule for Hubble observations is calculated using a computer algorithm which allows the spacecraft to occasionally gather bonus snapshots of data between longer observations. This image of the clashing triplet of galaxies in Arp 195 is one such snapshot. Extra observations such as these do more than provide spectacular images—they also help to identify promising targets to follow up with telescopes, such as the NASA/European Space Agency/Canadian Space Agency James Webb Space Telescope.


Credit: European Space Agency/Hubble & NASA, J. Dalcanton

Duration: 30 seconds

Release Date: July 26, 2021


#NASA #Hubble #Astronomy #Space #Science #Galaxy #Galaxies #Arp195 #Lynx #Constellation #Cosmos #Universe #HST #SpaceTelescope #ESA #Europe #GSFC #STScI #UnitedStates #STEM #Education #HD #Video

A Galactic Triplet: Interacting Galaxies | Hubble

A Galactic Triplet: Interacting Galaxies | Hubble

A dramatic triplet of galaxies takes center stage in this image from the NASA/European Space Agency Hubble Space Telescope, which captures a three-way gravitational tug-of-war between interacting galaxies. This system—known as Arp 195—is featured in the Atlas of Peculiar Galaxies, a list which showcases some of the weirder and more wonderful galaxies in the universe.

Observing time with the Hubble Space Telescope is extremely valuable, so astronomers do not want to waste a second. The schedule for Hubble observations is calculated using a computer algorithm which allows the spacecraft to occasionally gather bonus snapshots of data between longer observations. This image of the clashing triplet of galaxies in Arp 195 is one such snapshot. Extra observations such as these do more than provide spectacular images—they also help to identify promising targets to follow up with telescopes, such as the NASA/European Space Agency/Canadian Space Agency James Webb Space Telescope.


Credit: European Space Agency/Hubble & NASA, J. Dalcanton

Release Date: July 26, 2021


#NASA #Hubble #Astronomy #Space #Science #Galaxy #Galaxies #Arp195 #Lynx #Constellation #Cosmos #Universe #HST #SpaceTelescope #ESA #Europe #GSFC #STScI #UnitedStates #STEM #Education

Saturday, January 28, 2023

Great Galaxies of The Perseus Galaxy Cluster | Hubble

Great Galaxies of The Perseus Galaxy Cluster | Hubble
Two things capture your attention in this spectacular image taken by Hubble’s Wide Field Camera 3 (WFC3): the two enormous galaxies that flank the left and right sides of the image. The galaxy on the left is a lenticular galaxy, which rejoices in the name of 2MASX J03193743+4137580. The side-on spiral galaxy on the right is more simply named UGC 2665. Both galaxies lie approximately 350 million light-years from Earth, and they both form part of the enormous Perseus galaxy cluster. 

Perseus is an important figure in Greek mythology, renowned for slaying Medusa the Gorgon—who is herself famous for the unhappy reason that she was cursed to have living snakes for hair. Given Perseus’s impressive credentials, it seems appropriate that the eponymous galaxy cluster is one of the biggest objects in the known Universe, consisting of thousands of galaxies, only a few of which are visible in this image.

The wonderful detail in the image is thanks to the WFC3’s powerful resolution and high sensitivity. The WFC3 is sensitive to both visible and infrared light, so those are the wavelengths that are captured in this image. The Perseus supercluster looks very different at other wavelengths. Whilst in this image the spaces between the galaxies appear dark and peaceful, when the X-ray emission is observed the Perseus cluster appears to be burning with bright intense light.


Credit: European Space Agency (ESA)/Hubble & NASA, W. Harris

Acknowledgement: L. Shatz

Duration: 30 seconds 

Release Date: July 5, 2021


#NASA #Hubble #Astronomy #Space #Science #Galaxy #Galaxies #2MASXJ031937434137580 #UGC2665 #GalaxyClusters #PerseusSupercluster #Perseus #Constellation #Cosmos #Universe #HST #SpaceTelescope #ESA #Europe #GSFC #STScI #UnitedStates #STEM #Education #HD #Video

Great Galaxies of The Perseus Galaxy Cluster | Hubble

Great Galaxies of The Perseus Galaxy Cluster | Hubble


Two things capture your attention in this spectacular image taken by Hubble’s Wide Field Camera 3 (WFC3): the two enormous galaxies that flank the left and right sides of the image. The galaxy on the left is a lenticular galaxy, which rejoices in the name of 2MASX J03193743+4137580. The side-on spiral galaxy on the right is more simply named UGC 2665. Both galaxies lie approximately 350 million light-years from Earth, and they both form part of the enormous Perseus galaxy cluster. 

Perseus is an important figure in Greek mythology, renowned for slaying Medusa the Gorgon—who is herself famous for the unhappy reason that she was cursed to have living snakes for hair. Given Perseus’s impressive credentials, it seems appropriate that the eponymous galaxy cluster is one of the biggest objects in the known Universe, consisting of thousands of galaxies, only a few of which are visible in this image.

The wonderful detail in the image is thanks to the WFC3’s powerful resolution and high sensitivity. The WFC3 is sensitive to both visible and infrared light, so those are the wavelengths that are captured in this image. The Perseus supercluster looks very different at other wavelengths. Whilst in this image the spaces between the galaxies appear dark and peaceful, when the X-ray emission is observed the Perseus cluster appears to be burning with bright intense light.


Credit: European Space Agency (ESA)/Hubble & NASA, W. Harris

Acknowledgement: L. Shatz

Release Date: July 5, 2021


#NASA #Hubble #Astronomy #Space #Science #Galaxy #Galaxies #2MASXJ031937434137580 #UGC2665 #GalaxyClusters #PerseusSupercluster #Perseus #Constellation #Cosmos #Universe #HST #SpaceTelescope #ESA #Europe #GSFC #STScI #UnitedStates #STEM #Education

A Bear on Planet Mars? | NASA's Mars Reconnaissance Orbiter

A Bear on Planet Mars? | NASA's Mars Reconnaissance Orbiter

Wait . . . what? Is this a peculiar formation or do your eyes deceive you? 

There is a hill with a V-shaped collapse structure ("the nose"), two craters ("the eyes"), and a circular fracture pattern ("the head"). The circular fracture pattern might be due to the settling of a deposit over a buried impact crater. Maybe "the nose" is a volcanic or mud vent and the deposit could be lava or mud flows?

"Maybe just grin and bear it!" ;)

Seeing familiar objects or patterns in otherwise random or unrelated objects or patterns is called pareidolia. It is a form of apophenia, which is a more general term for the human tendency to seek patterns in random information. 

Black and white images are less than 5 km across; enhanced color images are  less than1 km.

The Mars Reconnaissance Orbiter (MRO) is a spacecraft designed to study the geology and climate of Mars, to provide reconnaissance of future landing sites, and to relay data from surface missions back to Earth. It was launched on August 12, 2005, and reached Mars on March 10, 2006. 

NASA’s Jet Propulsion Laboratory (JPL), a division of the California Institute of Technology in Pasadena, Calif., manages the Mars Reconnaissance Orbiter for NASA’s Science Mission Directorate, Washington. The HiRISE camera was built by Ball Aerospace and Technology Corporation and is operated by the University of Arizona.


Credit: NASA/JPL-Caltech/University of Arizona

Narration: Tre Gibbs

Tre's website: www.tregibbs.com

Duration: 52 seconds

Release Date: Jan. 25, 2023


#NASA #Astronomy #Space #Science #Mars #Planet #RedPlanet #Hill #Craters #Pareidolia #Geology #Landscape #Terrain #MRO #HiRISE #Spacecraft #JPL #Caltech #UA #UniversityOfArizona #UnitedStates #SolarSystem #STEM #Education #HD #Video

Long Duration Human Spaceflight: Hibernation Research | European Space Agency

Long Duration Human Spaceflight: Hibernation Research | European Space Agency

Did you know that the European Space Agency (ESA) is researching human hibernation for long distance spaceflight to Mars or beyond? Hibernating astronauts could be the best way to save mission costs, reduce the size of spacecraft by a third and keep crew healthy on their way to Mars. An ESA-led investigation suggests that human hibernation goes beyond the realm of science-fiction and may become a game-changing technique for space travel.

When packing for a return flight to the Red Planet, space engineers account for around two years’ worth of food and water for the crew.

Torpor during hibernation is an induced state that reduces the metabolic rate of an organism. This ‘suspended animation’ is a common mechanism in animals who wish to preserve energy.

Reducing the metabolic rate of a crew en route to Mars down to 25% of the normal state would dramatically cut down the amount of supplies and habitat size, making long-duration exploration more feasible.

Mimicking therapeutic torpor, the idea of putting human into a state of hibernation, has been around in hospitals since the 1980s—doctors can induce hypothermia to reduce metabolism during long and complex surgeries. However, it is not an active reduction of energy and misses most of the advantages of torpor. Studies on hibernation to visit other planets could offer new potential applications for patient care on Earth.

Animals hibernate to survive periods of cold and food or water scarcity, reducing their heart rate, breathing and other vital functions to a fraction of their normal life, while body temperature lowers close to ambient temperature. Tardigrades, frogs and reptiles are very good at it.

Lower testosterone levels seem to aid long hibernation in mammals, estrogens in humans strongly regulate energy metabolism.

With the crew at rest for long periods, artificial intelligence will come into play during anomalies and emergencies.

The possibilities of hibernation for medical use is of particular interest to the European research community and could transform how we approach many severe illnesses.

Inducing torpor is already used in some medical environments such as surgical theathers to replace anesthesia in those patients allergic to anesthetic drugs.

The step to space research is closer than you might think. Get involved with spaceflight research via https://www.esa.int/spaceflightAO

Find out about our commercial partnerships and opportunities in human and robotic exploration via https://www.esa.int/explorationpartners to run your research in microgravity as well.


Credit: European Space Agency (ESA)

Duration: 8 minutes

Release Date: Jan. 25, 2023

#NASA #ESA #Space #Science #Astronauts #HumanSpaceflight #SolarSystem #Mars #RedPlanet #Exploration #HumanBiology #AnimalBiology #Hibernation #Torpor #LifeSupport #LongDurationMissions #LifeSciences #Europe #MedicalResearch #STEM #Education #HD #Video

Expedition 68: NASA’s SpaceX Crew-6 | International Space Station

Expedition 68: NASA’s SpaceX Crew-6 | International Space Station


The four SpaceX Crew-6 members pose for a portrait underneath a Falcon 9 rocket booster at SpaceX's headquarters in Hawthorne, California. From left, are Mission Specialist Andrey Fedyaev of Roscosmos; Commander Stephen Bowen and Pilot Warren "Woody" Hoburg, both from NASA; and Mission Specialist Sultan Alneyadi from the Mohammed bin Rashid Space Centre of the United Arab Emirates (UAE)


SpaceX Crew-6 crew members inside SpaceX Hangar X at the Kennedy Space Center in Florida

SpaceX Crew-6 crew members pose for a photo on the SpaceX helipad at the Kennedy Space Center in Florida
SpaceX Crew-6 crew members pose for a photo during a training session at the Kennedy Space Center's Launch Pad 39A in Florida

The four crew members of NASA's SpaceX Crew-6 mission to the International Space Station are Mission Specialist Sultan Al Nedayi of the United Arab Emirates (UAE), Mission Specialist Andrey Fedyaev of Roscosmos (Russia), Pilot William Hoburg (NASA), and Commander Stephen Bowen (NASA). Launch is scheduled for no earlier than Sunday, Feb. 26, 2023.

Astronaut Sultan AlNeyadi from the Mohammed bin Rashid Space Center (United Arab Emirates) will make history by being the first astronaut from the Arab world to spend six months on the International Space Station (ISS). AlNeyadi has undergone a 20-month long rigorous training for the Crew-6 mission. AlNeyadi began his training in September 2018, at the Yuri Gagarin Cosmonaut Training Center at Star City in Moscow, Russia.

Cosmonaut Andrey Fedyaev (Russia)

Andrey Valerievich Fediaev (Russian Cyrillic: Андрей Валерьевич Федяев; born February 26, 1981) is a Russian cosmonaut. Fediaev received his an engineering degree in air transport and Air Traffic Control from the Balashov Military Aviation School in 2004. Following graduation, Fediaev joined the Russian Air Force in the 317th mixed aviation segment. He obtained the rank of major before his retirement in 2013. He logged over 500 hours in Russian aircraft.

Fediaev was selected as a cosmonaut in 2012. He reported to the Gagarin Cosmonaut Training Center in 2012 and was named a test cosmonaut on June 16, 2014.

On July 15, 2022, he was assigned to the SpaceX Crew-6 mission after a recent crew swap agreement between NASA and Roscosmos.

NASA Astronaut William Hoburg's Official Biography:

https://www.nasa.gov/astronauts/biographies/warren-hoburg

https://www.nasa.gov/content/warren-hoburg-phd-nasa-astronaut

NASA Astronaut Stephen Bowen's Official Biography:

https://www.nasa.gov/astronauts/biographies/stephen-g-bowen

NASA’s Commercial Crew Program (CCP) works with the American aerospace industry to provide safe, reliable, and cost-effective transportation to and from the International Space Station on American-made rockets and spacecraft launching from American soil.

An international partnership of space agencies provides and operates the elements of the International Space Station (ISS). The principals are the space agencies of the United States, Russia, Europe, Japan, and Canada. The ISS has been the most politically complex space exploration program ever undertaken.


Credit: Space Exploration Technologies Corp. (SpaceX)

Image Dates: Aug. 8, 2022 - Jan. 13, 2023


#NASA #ESA #Space #Earth #Science #ISS #SpaceX #CrewDragon #Spacecraft #SpaceXCrew6 #Astronauts #SultanAlNedayi #MBRSC #UAE #Cosmonaut #AndreyFedyaev #Russia #Россия #Роскосмос #WilliamHoburg #MIT #StephenBowen #USNavy #CCP #HumanSpaceflight #UnitedStates #STEM #Education

Friday, January 27, 2023

Honoring Our Fallen Heroes | This Week @NASA

Honoring Our Fallen Heroes | This Week @NASA

Honoring our fallen heroes, working on a nuclear option for space travel, and the next crewed mission to the space station . . . a few of the stories to tell you about—This Week at NASA!


Credit: National Aeronautics and Space Administration (NASA)

Video Producer: Andre Valentine

Video Editor: Haley Reed

Music: Universal Production Music

Duration: 2 minutes

Release Date: Jan. 27, 2023


#NASA #Space #Earth #ISS #SpaceXCrew6 #Moon #Artemis #Astronomy #Science #NASARemembers #Astronauts #Apollo1 #SpaceShuttleChallenger #SpaceShuttleColumbia #Scientists #Engineers #Heroes #History #SolarSystem #Exploration #UnitedStates #History #STEM #Education #HD #Video

Iceberg Larger than London Breaks Off Antarctica’s Brunt Ice Shelf | ESA

Iceberg Larger than London Breaks Off Antarctica’s Brunt Ice Shelf | ESA

Satellite imagery confirms an iceberg around the size of Greater London broke off Antarctica’s Brunt Ice Shelf due to a natural process called ‘calving’. The iceberg, measuring 1550 sq km, detached from the 150 m-thick ice shelf a decade after scientists first spotted massive cracks in the shelf.

For more information on the newly-birthed A81 iceberg: https://www.esa.int/Applications/Observing_the_Earth/Copernicus/Giant_iceberg_breaks_away_from_Antarctic_ice_shelf


Credit: European Space Agency (ESA)

Duration: 4 minutes

Release Date: Jan. 27, 2023


#ESA #Space #Earth #Planet #Satellites #Copernicus #Sentinel #EarthObservation #RemoteSensing #Atmosphere #Oceans #Climate #ClimateChange #Meteorology #Antarctica #BruntIceShelf #Iceberg #A81Iceberg #STEM #Education #HD #Video

International Space Station Research: Annual Highlights 2022 | NASA Johnson

International Space Station Research: Annual Highlights 2022 | NASA Johnson

"For over 20 years, the International Space Station has conducted research in microgravity to develop technologies, unlock biological phenomena, and more! In 2022 the station’s unique laboratory enabled measurements of the Earth’s surface temperature, paved the way in experimental quantum physics, and conducted hundreds of experiments across scientific disciplines."

The Annual Highlights of Results from the International Space Station publication shares some of the space station’s outstanding achievements of 2022. The full publication is available for download at: www.nasa.gov/stationresultsresourcelibrary

Learn more about the important research being operated on Station:

https://www.nasa.gov/iss-science 

For more information about STEM on Station:

https://www.nasa.gov/stemonstation

Science, Technology, Engineering, Math (STEM) Education

An international partnership of space agencies provides and operates the elements of the  International Space Station (ISS). The principals are the space agencies of the United States, Russia, Europe, Japan, and Canada. The ISS has been the most politically complex space exploration program ever undertaken.


Credit: NASA's Johnson Space Center (JSC)

Duration: 55 seconds

Release Date: Jan. 27, 2023


#NASA #Space #Earth #Science #ISS #Microgravity #Research #Laboratory #Experiments #Astronauts #HumanSpaceflight #UnitedStates #STEM #Education #HD #Video