NASA astronaut Christina Koch works while tethered near the Port 6 truss segment of the International Space Station. http://www.nasa.gov/sites/default/files/thumbnails/image/iss061e005311.jpg

In 1572, Danish astronomer Tycho Brahe was among those who noticed a new bright object in the constellation Cassiopeia. http://www.nasa.gov/sites/default/files/thumbnails/image/tycho.jpg

NASA astronaut Christina Koch conducts her fourth spacewalk at the International Space Station with fellow NASA astronaut Jessica Meir http://www.nasa.gov/sites/default/files/thumbnails/image/iss061e008880.jpeg

Vice President Mike Pence delivers remarks during the opening ceremony of the 70th International Astronautical Congress. http://www.nasa.gov/sites/default/files/thumbnails/image/48936697326_123e0925c3_k.jpg

Engineers and technicians at NASA’s Michoud Assembly Facility in New Orleans have structurally mated the first of four RS-25 engines to the core stage for NASA’s Space Launch System (SLS) rocket that will help power the first Artemis mission to the Moon. http://www.nasa.gov/sites/default/files/thumbnails/image/maf_20191021_p_rs-25_engine_install_reveal-62.jpg

The Medusa merger, was not always one entity, but two. An early galaxy consumed a smaller gas-rich system, throwing out streams of stars and dust into space. These streams resemble the writhing snakes that Medusa, a monster in ancient Greek mythology, famously had on her head in place of hair, lending the object its intriguing name. http://www.nasa.gov/sites/default/files/thumbnails/image/potw1939a.jpg

Astronomers using data from NASA’s Chandra X-ray Observatory and other telescopes have put together a detailed map of a rare collision between four galaxy clusters. http://www.nasa.gov/sites/default/files/thumbnails/image/abell1758.jpg

This image of star trails was compiled from time-lapse photography taken by NASA astronaut Christina Koch while onboard the International Space Station. http://www.nasa.gov/sites/default/files/thumbnails/image/startrailtimelapse_lrg.jpg

A Northrop Grumman Antares rocket is seen as it rolls out to Pad-0A, Tuesday, Oct. 29, 2019, at NASA's Wallops Flight Facility in Virginia. http://www.nasa.gov/sites/default/files/thumbnails/image/48980275608_dec6675aae_k.jpg

From the vantage point of space aboard the International Space Station, NASA astronaut Andrew Morgan captured this image of a California wildfire. http://www.nasa.gov/sites/default/files/thumbnails/image/461c5671.jpg

The Northrop Grumman Antares rocket, with Cygnus resupply spacecraft onboard, launches from Pad-0A of NASA's Wallops Flight Facility, Saturday, November 2, 2019. http://www.nasa.gov/sites/default/files/thumbnails/image/49002058586_3ad9f42d8c_k.jpg

Orson John helps prepare Ice, Cloud and land Elevation Satellite-2 (ICESat-2) for encapsulation in the United Launch Alliance Delta II payload fairing on Sept. 4, 2018, at Space Launch Complex 2 at Vandenberg Air Force Base in California. http://www.nasa.gov/sites/default/files/thumbnails/image/icesat2closeoutorson.jpg

The U.S. Cygnus space freighter from Northrop Grumman is pictured in the grips of the Canadarm2 robotic arm as it was installed to the Unity module for 70 days of cargo transfers. http://www.nasa.gov/sites/default/files/thumbnails/image/iss061e028414.jpg

This week in 1967, the Apollo 4 mission launched from NASA’s Kennedy Space Center. http://www.nasa.gov/sites/default/files/thumbnails/image/s67-50903_cropped.jpg

A student from Sinte Gleska University works to build a model rover for a NASA Community College Aerospace Scholars. http://www.nasa.gov/sites/default/files/thumbnails/image/rover_0.jpg

The planet Mercury is seen in silhouette, low center, as it transits across the face of the Sun, Monday, Nov. 11, 2019. http://www.nasa.gov/sites/default/files/thumbnails/image/49048341728_21e121889f_o.jpg

Powtawche Valerino is a guidance engineer who works for Aerodyne Industries at the NASA's Marshall Space Flight Center, supporting the agency’s Space Launch System program. http://www.nasa.gov/sites/default/files/thumbnails/image/powtawchevalerino.jpg

Fifty years ago, on Nov. 14, 1969, Apollo 12 launched at 11:22 a.m. EST from Launch Complex 39A at the Kennedy Space Center in Florida. http://www.nasa.gov/sites/default/files/thumbnails/image/s80-37406.jpg

Many galaxies we see through telescopes such as the NASA/ESA Hubble Space Telescope, the source of this beautiful image, look relatively similar: spiraling arms, a glowing center, and a mixture of bright specks of star formation and dark ripples of cosmic dust weaving throughout. This galaxy, a spiral galaxy named NGC 772, is no exception. http://www.nasa.gov/sites/default/files/thumbnails/image/hubble.jpg

Station Commander ​​Luca Parmitano of the European Space Agency conducts repairs, while attached to the Canadarm during the first spacewalk to repair the Alpha Magnetic Spectrometer. http://www.nasa.gov/sites/default/files/thumbnails/image/15november2019spacewalk.jpg