Astronomy Picture Of the Day (APOD)Encke and the Tadpoles
History's second known periodic comet is Comet Encke (2P/Encke). As it swings through the inner Solar System, Encke's orbit takes it from an aphelion, its greatest distance from the Sun, inside the orbit of Jupiter to a perihelion just inside the orbit of Mercury.
Orionids in Taurus
History's first known periodic comet, Comet Halley (1P/Halley), returns to the inner Solar System every 76 years or so. The famous comet made its last appearance to the naked-eye in 1986. But dusty...
APOD: 2023 October 25 Б Gone in 60 Seconds: A Green Flash Sunset
In 60 seconds, this setting Sun will turn green. Actually, the top of the Sun already appears not only green, but wavey -- along with all of its edges. The Sun itself is unchanged -- both effects are caused by looking along hot and cold layers in Earth's atmosphere.
APOD: 2023 October 24 Б Arp 87: Merging Galaxies from Hubble
This dance is to the death. As these two large galaxies duel, a cosmic bridge of stars, gas, and dust currently stretches over 75,000 light-years and joins them. The bridge itself is strong evidence that these two immense star systems have passed close to each other and experienced violent tides induced by mutual gravity.
APOD: 2023 October 23 Б Moon Io from Spacecraft Juno
There goes another one! Volcanoes on Jupiter's moon Io keep erupting. To investigate, NASA's robotic Juno spacecraft has begun a series of visits to this very strange moon. Io is about...
APOD: 2023 October 22 Б Ghost Aurora over Canada
What does this aurora look like to you? While braving the cold to watch the skies above northern Canada early one morning in 2013, a most unusual aurora appeared. The aurora definitely appeared to be shaped like something, but what?
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.
Galaxies and a Comet
Galaxies abound in this sharp telescopic image recorded on October 12 in dark skies over June Lake, California. The celestial scene spans nearly 2 degrees within the boundaries of the well-trained northern constellation Canes Venatici.
A Sunrise at Sunset Point
This timelapse series captured on October 14 is set against the sunrise view from Sunset Point, Bryce Canyon, planet Earth. Of course on that date the New Moon caught up with the Sun in the canyon's morning skies.
APOD: 2023 October 18 Б Dust and the Western Veil Nebula
It's so big it is easy to miss. The entire Veil Nebula spans six times the diameter of the full moon, but is so dim you need binoculars to see it. The nebula was created about 15,000 years ago when a star in the constellation of the Swan (Cygnus) exploded.