#2024 dec

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Astronomy Picture of the Day

2024 December 11

The Shells and Jets of Galaxy Centaurus A

A galaxy is seen in the center of the image. Faint shells are seen around it. A red-colored jet is seen emanating from the galaxy toward the lower right.

Image Credit: Rolf Olsen

What's the closest active galaxy to planet Earth? That would be Centaurus A, cataloged as NGC 5128, which is only 12 million light-years distant. Forged in a collision of two otherwise normal galaxies, Centaurus A shows several distinctive features including a dark dust lane across its center, outer shells of stars and gas, and jets of particles shooting out from a supermassive black hole at its center. The featured image captures all of these in a composite series of visible light images totaling over 310 hours captured over the past 10 years with a homebuilt telescope operating in Auckland, New Zealand. The brightness of Cen A's center from low-energy radio waves to high-energy gamma rays underlies its designation as an active galaxy.

Authors & editors: Robert Nemiroff (MTU) & Jerry Bonnell (UMCP)

NASA Official: Amber Straughn

A service of: ASD at NASA / GSFC,

NASA Science Activation

& Michigan Tech. U.

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Astronomy Picture of the Day

2024 December 3

Ice Clouds over a Red Planet

Ice clouds are seen over the surface of Mars on the upper right. Toward the lower left is a bright spot in the sky which is likely the Sun rising through Martian dust.

Image Credit: NASA, JPL-Caltech, Kevin M. Gill; Processing: Rogelio Bernal Andreo

If you could stand on Mars -- what might you see? You might look out over a vast orange landscape covered with rocks under a dusty orange sky, with a blue-tinted Sun over the horizon, and odd-shaped water clouds hovering high overhead. This was just the view captured last March by NASA's rolling explorer, Perseverance. The orange coloring is caused by rusted iron in the Martian dirt, some of which is small enough to be swept up by winds into the atmosphere. The blue tint near the rising Sun is caused by blue light being preferentially scattered out from the Sun by the floating dust. The light-colored clouds on the right are likely composed of water-ice and appear high in the Martian atmosphere. The shapes of some of these clouds are unusual for Earth and remain a topic of research.

Authors & editors: Robert Nemiroff (MTU) & Jerry Bonnell (UMCP)

NASA Official: Amber Straughn

A service of: ASD at NASA / GSFC,

NASA Science Activation

& Michigan Tech. U.

[of-stars-and-dust]

Astronomy Picture of the Day

2024 December 8

Aurora around Saturn's North Pole

A picture of Saturn is shown with tan clouds and light rings. Surrounding the north pole at the top are bright blue swirls.

Image Credit: NASA, ESA, Hubble, OPAL Program, J. DePasquale (STScI), L. Lamy (Obs. Paris)

Are Saturn's auroras like Earth's? To help answer this question, the Hubble Space Telescope and the Cassini spacecraft monitored Saturn's North Pole simultaneously during Cassini's final orbits around the gas giant in September 2017. During this time, Saturn's tilt caused its North Pole to be clearly visible from Earth. The featured image is a composite of ultraviolet images of auroras and optical images of Saturn's clouds and rings, all taken by Hubble. Like on Earth, Saturn's northern auroras can make total or partial rings around the pole. Unlike on Earth, however, Saturn's auroras are frequently spirals -- and more likely to peak in brightness just before midnight and dawn. In contrast to Jupiter's auroras, Saturn's auroras appear better related to connecting Saturn's internal magnetic field to the nearby, variable, solar wind. Saturn's southern auroras were similarly imaged back in 2004 when the planet's South Pole was clearly visible to Earth.

Authors & editors: Robert Nemiroff (MTU) & Jerry Bonnell (UMCP)

NASA Official: Amber Straughn

A service of: ASD at NASA / GSFC,

NASA Science Activation

& Michigan Tech. U.

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Astronomy Picture of the Day

2024 December 23

Christmas Tree Aurora

A star filled night sky is shown with aurora visible in blue, purple and green. The aurora could be perceived to be a spruce tree, or even a Christmas tree.

Image Credit & Copyright: Jingyi Zhang

It was December and the sky lit up like a Christmas tree. Shimmering, the vivid green, blue, and purple auroral colors that formed the tree-like apparition were caused by high atmospheric oxygen and nitrogen reacting to a burst of incoming electrons. Collisions caused the orbital electrons of atoms and molecules to jump into excited energy states and emit visible light when returning to their normal state. The featured image was captured in Djúpivogur, Iceland during the last month of 2023. Our Sun is currently in its most energetic phase of its 11-year cycle, with its high number of active regions and sunspots likely to last into next year. Of course, the Sun has been near solar maximum during this entire year, with its outbursts sometimes resulting in spectacular Earthly auroras.

Authors & editors: Robert Nemiroff (MTU) & Jerry Bonnell (UMCP)

NASA Official: Amber Straughn

A service of: ASD at NASA / GSFC,

NASA Science Activation

& Michigan Tech. U.

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Astronomy Picture of the Day

2024 December 17

Near to the Heart Nebula

A wide star field is shown with several nebulae as identified by the rollover image. On the upper left is a large nebula named the Heart Nebula.

Image Credit & Copyright: Jeff Horne & Drew Evans

What excites the Heart Nebula? First, the large emission nebula on the upper left, catalogued as IC 1805, looks somewhat like a human heart. The nebula glows brightly in red light emitted by its most prominent element, hydrogen, but this long-exposure image was also blended with light emitted by sulfur (yellow) and oxygen (blue). In the center of the Heart Nebula are young stars from the open star cluster Melotte 15 that are eroding away several picturesque dust pillars with their atom-exciting energetic light and winds. The Heart Nebula is located about 7,500 light years away toward the constellation of Cassiopeia. This wide field image shows much more, though, including the Fishhead Nebula just below the Heart, a supernova remnant on the lower left, and three planetary nebulas on the image right. Taken over 57 nights, this image is so deep, though, that it clearly shows fainter long and complex filaments.

Authors & editors: Robert Nemiroff (MTU) & Jerry Bonnell (UMCP)

NASA Official: Amber Straughn

A service of: ASD at NASA / GSFC,

NASA Science Activation

& Michigan Tech. U.

[of-stars-and-dust]

Astronomy Picture of the Day

2024 December 25

Diamond Dust Sky Eye

A snow covered road goes up a hill to a sky filled with stars. Arcs and halos in the sky ahead appear similar to a giant eye.

Image Credit & Copyright: Jaroslav Fous

Why is there a huge eye in the sky? Diamond dust. That is an informal term for small ice crystals that form in the air and flitter to the ground. Because these crystals are geometrically shaped, they can together reflect light from the Sun or Moon to your eyes in a systematic way, causing huge halos and unusual arcs to appear. And sometimes, together the result can seem like a giant eye looking right back at you. In the featured image taken in the Ore Mountains of the Czech Republic last week, a bright Moon rising through ice fog-filled air resulted in many of these magnificent sky illusions to be visible simultaneously. Besides Moon dogs, tangent arcs, halos, and a parselenic circle, light pillars above distant lights are visible on the far left, while Jupiter and Mars can be found just inside the bottom of the 22-degree halo.

Authors & editors: Robert Nemiroff (MTU) & Jerry Bonnell (UMCP)

NASA Official: Amber Straughn

A service of: ASD at NASA / GSFC,

NASA Science Activation

& Michigan Tech. U.

[of-stars-and-dust]

Astronomy Picture of the Day

2024 December 14

Apollo 17's Moonship

Image Credit: Apollo 17, NASA, (Image Reprocessing: Andy Saunders)

Awkward and angular looking, Apollo 17's lunar module Challenger was designed for flight in the near vacuum of space. Digitally enhanced and reprocessed, this picture taken from Apollo 17's command module America shows Challenger's ascent stage in lunar orbit. Small reaction control thrusters are at the sides of the moonship with the bell of the ascent rocket engine underneath. The hatch allowing access to the lunar surface is seen at the front, with a round radar antenna at the top. Mission commander Gene Cernan is clearly visible through the triangular window. This spaceship performed gracefully, landing on the Moon and returning the Apollo astronauts to the orbiting command module in December of 1972. So where is Challenger now? Its descent stage remains at the Apollo 17 landing site in the Taurus-Littrow valley. The ascent stage pictured was intentionally crashed nearby after being jettisoned from the command module prior to the astronauts' return to planet Earth.

Authors & editors: Robert Nemiroff (MTU) & Jerry Bonnell (UMCP)

NASA Official: Amber Straughn

A service of: ASD at NASA / GSFC,

NASA Science Activation

& Michigan Tech. U.

[of-stars-and-dust]

Astronomy Picture of the Day

2024 December 12

Phaethon's Brood

Image Credit & Copyright: Mikiya Sato (Nippon Meteor Society)

Based on its well-measured orbit, 3200 Phaethon (sounds like FAY-eh-thon) is recognized as the source of the meteoroid stream responsible for the annual Geminid meteor shower. Even though most meteor shower parents are comets, 3200 Phaethon is a known and closely tracked near-Earth asteroid with a 1.4 year orbital period. Rocky and sun-baked, its perihelion or closest approach to the Sun is well within the orbit of innermost planet Mercury. In this telescopic field of view, the asteroid's rapid motion against faint background stars of the heroic constellation Perseus left a short trail during the two minute total exposure time. The (faint) parallel streaks of its meteoric children flashed much more quickly across the scene. The family portrait was recorded near the Geminid meteor shower's very active peak on 2017 December 13. That was just three days before 3200 Phaethon's historic close approach to planet Earth. This year, the night of December 13 should again see the peak of the Geminid meteor shower, but faint meteors will be washed out by the bright light of the nearly full moon.

Authors & editors: Robert Nemiroff (MTU) & Jerry Bonnell (UMCP)

NASA Official: Amber Straughn

A service of: ASD at NASA / GSFC,

NASA Science Activation

& Michigan Tech. U.