Interstellar Interloper 2I Borisov
17.10.2019

After the 2017 detecton of 1I/'Oumuamua, comet 2I/Borisov has become the second recognized interstellar interloper. Like 'Oumuamua, Borisov's measured hyperbolic trajectory and speed as it falls toward the Sun confirm that its origin is from beyond our Solar System.

APOD: 2023 January 17 Б Unexpected Clouds Toward the Andromeda Galaxy
16.01.2023

Why are there oxygen-emitting arcs near the direction of the Andromeda galaxy? No one is sure. The gas arcs, shown in blue, were discovered and first confirmed by amateur astronomers just last year.

Quarter Moons
20.10.2023

Half way between New Moon and Full Moon is the Moon's first quarter phase. That's a quarter of the way around its moonthly orbit. At the first quarter phase, half the Moon's visible side is illuminated by sunlight.

Hyakutake, Venus, Orion, and Pond
18.04.1996

Can you find Comet Hyakutake in the above picture? In this gorgeous photo, the starry night sky of April 9th is pictured with its new comet visitor. In the foreground is a pond with the lights of Kansas City, Missouri on the western horizon. On the upper left, the constellation of Orion is visible.

Planet Near a Galaxy Core
5.05.1996

What would the night sky look like if you lived on a planet near the center of a galaxy? Now imagine that this galaxy houses a black hole billions of times more massive than a star. From this spectacular vantage point, the sky might look like the above illustration.

The Satellites that Surround Earth
14.07.2003

Thousands of satellites orbit the Earth. Costing billions of dollars, this swarm of high altitude robots is now vital to communication, orientation, and imaging both Earth and space. One common type of orbit is geostationary where a satellite will appear to hover above one point on Earth's equator.

The Smooth Spheres of Gravity Probe B
28.04.2004

Does gravity have a magnetic counterpart? Spin any electric charge and you get a magnetic field. Spin any mass and, according to Einstein, you should get a very slight effect that acts something like magnetism. This effect is expected to be so small that it is beyond practical experience and even beyond laboratory measurement.

Night Shining Clouds
5.07.2007

Alluring noctilucent or night-shining clouds lie near the edge of space, some 80 kilometers above Earth's surface. Of course, when viewed from space the clouds are more properly called polar mesospheric clouds (PMCs) -- seen here for the first time in image data from the Aeronomy of Ice in the Mesosphere (AIM) satellite.

Dawn Before Nova
16.11.2009

Will this dawn bring another nova? Such dilemmas might be pondered one day by future humans living on a planet orbiting a cataclysmic variable binary star system. Cataclysmic variables involve gas falling from a large star onto an accretion disk surrounding a massive but compact white dwarf star.

Night Launch of the Space Shuttle Endeavour
8.02.2010

Sometimes, the space shuttle launches at night. Pictured above, the space shuttle Endeavour lifted off in yesterday's early morning hours from Launch Pad 39A in Kennedy Space Center, Florida, USA, bound for the International Space Station (ISS).