NasaBot's Space

Galaxy Wars: M81 and M82 [apod.nasa.gov]

The two dominant galaxies near center are far far away, 12 million light-years distant toward the northern constellation of the Great Bear.

On the right, with grand spiral arms and bright yellow core is spiral galaxy M81.

Also known as Bode's galaxy, M81 spans some 100,000 light-years.

On the left is cigar-shaped irregular galaxy M82.

The pair have been locked in gravitational combat for a billion years.

Gravity from each galaxy has profoundly affected the other during a series of cosmic close encounters.

Their last go-round lasted about 100 million years and likely raised density waves rippling around M81, resulting in the richness of M81's spiral arms.

M82 was left with violent star forming regions and colliding gas clouds so energetic that the galaxy glows in X-rays.

In the next few billion years, their continuing gravitational encounters will result in a merger, and a single galaxy will remain.

This extragalactic scenario also includes other members of the interacting M81 galaxy group with NGC 3077 below and right of the large spiral, and NGC 2976 at upper right in the frame.

Captured under dark night skies in the Austrian Alps, the foreground of the wide-field image is filled with integrated flux nebulae.

Those faint, dusty interstellar clouds reflect starlight above the plane of our own Milky Way galaxy.

The Seagull Nebula [apod.nasa.gov]

A broad expanse of glowing gas and dust presents a bird-like visage to astronomers from planet Earth, suggesting its popular moniker - The Seagull Nebula.

Using narrowband image data, this 3-panel mosaic of the cosmic bird covers a 2.5 degree swath across the plane of the Milky Way, near the direction of Sirius, alpha star of the constellation Canis Major.

Likely part of a larger shell structure swept up by successive supernova explosions, the broad Seagull Nebula is cataloged as Sh2-296 and IC 2177.

The prominent bluish arc below and right of center is a bow shock from runaway star FN Canis Majoris.

This complex of gas and dust clouds with other stars of the Canis Majoris OB1 association spans over 200 light-years at the Seagull Nebula's estimated 3,800 light-year distance.

MACS0647: Gravitational Lensing of the Early Universe by Webb [apod.nasa.gov]

Gravitational lensing by the galaxy cluster MACS0647 — in which the massive foreground cluster distorts and lenses the light emitted by distant background galaxies along the line of sight — is on vivid display here in this recent multi-color infrared image from the James Webb Space Telescope (JWST).

In particular, the background source MACS0647-JD is seen to be lensed three times by the cluster.

When first discovered with the Hubble Space Telescope, MACS0647-JD was observed as an amorphous blob.

With Webb though, this single source is revealed to be a pair or small group of galaxies.

The colors of the MACS0647-JD objects are different as well — indicating differences potentially in the age or dust content of these galaxies.

These new images provide rare examples of galaxies in an era only a few 100 million years after the Big Bang.

Unexpected Clouds Toward the Andromeda Galaxy [apod.nasa.gov]

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.

The two main origin hypotheses for the arcs are that they really are close to Andromeda (M31), or that they are just coincidentally placed gas filaments in our Milky Way galaxy.

Adding to the mystery is that arcs were not seen in previous deep images of M31 taken primarily in light emitted by hydrogen, and that other, more distant galaxies have not been generally noted as showing similar oxygen-emitting structures.

Dedicated amateurs using commercial telescopes made this discovery because, in part, professional telescopes usually investigate angularly small patches of the night sky, whereas these arcs span several times the angular size of the full moon.

Future observations — both in light emitted by oxygen and by other elements — are sure to follow.

Moon Enhanced [apod.nasa.gov]

Our Moon doesn't really look like this.

Earth's Moon, Luna, doesn't naturally show this rich texture, and its colors are more subtle.

But this digital creation is based on reality.

The featured image is a composite of multiple images and enhanced to bring up real surface features.

The enhancements, for example, show more clearly craters that illustrate the tremendous bombardment our Moon has been through during its 4.6-billion-year history.

The dark areas, called maria, have fewer craters and were once seas of molten lava.

Additionally, the image colors, although based on the moon's real composition, are changed and exaggerated.

Here, a blue hue indicates a region that is iron rich, while orange indicates a slight excess of aluminum.

Although the Moon has shown the same side to the Earth for billions of years, modern technology is allowing humanity to learn much more about it — and how it affects the Earth.

M1: The Crab Nebula from Hubble [apod.nasa.gov]

This is the mess that is left when a star explodes.

The Crab Nebula, the result of a supernova seen in 1054 AD, is filled with mysterious filaments.

The filaments are not only tremendously complex, but appear to have less mass than expelled in the original supernova and a higher speed than expected from a free explosion.

The featured image, taken by the Hubble Space Telescope, is presented in three colors chosen for scientific interest.

The Crab Nebula spans about 10 light-years.

In the nebula's very center lies a pulsar: a neutron star as massive as the Sun but with only the size of a small town.

The Crab Pulsar rotates about 30 times each second.

Discovery + Outreach: Graduate student research position open for APOD

Perihelion Sun 2023 [apod.nasa.gov]

Perihelion for 2023, Earth's closest approach to the Sun, was on January 4 at 16:17 UTC.

That was less than 24 hours after this sharp image of the Sun's disk was recorded with telescope and H-alpha filter from Sidney, Australia, planet Earth.

An H-alpha filter transmits a characteristic red light from hydrogen atoms.

In views of the Sun it emphasizes the Sun's chromosphere, a region just above the solar photosphere or normally visible solar surface.

In this H-alpha image of the increasingly active Sun planet-sized sunspot regions are dominated by bright splotches called plages.

Dark filaments of plasma snaking across the solar disk transition to bright prominences when seen above the solar limb.

Young Star Cluster NGC 346 [apod.nasa.gov]

The most massive young star cluster in the Small Magellanic Cloud is NGC 346, embedded in our small satellite galaxy's largest star forming region some 210,000 light-years distant.

Of course the massive stars of NGC 346 are short lived, but very energetic.

Their winds and radiation sculpt the edges of the region's dusty molecular cloud triggering star-formation within.

The star forming region also appears to contain a large population of infant stars.

A mere 3 to 5 million years old and not yet burning hydrogen in their cores, the infant stars are strewn about the embedded star cluster.

This spectacular infrared view of NGC 346 is from the James Webb Space Telescope's NIRcam.

Emission from atomic hydrogen ionized by the massive stars' energetic radiation as well as and molecular hydrogen and dust in the star-forming molecular cloud is detailed in pink and orange hues.

Webb's sharp image of the young star-forming region spans 240 light-years at the distance of the Small Magellanic Cloud.

Stardust in Perseus [apod.nasa.gov]

This cosmic expanse of dust, gas, and stars covers some 6 degrees on the sky in the heroic constellation Perseus.

At upper left in the gorgeous skyscape is the intriguing young star cluster IC 348 and neighboring Flying Ghost Nebula with clouds of obscuring interstellar dust cataloged as Barnard 3 and 4.

At right, another active star forming region NGC 1333 is connected by dark and dusty tendrils on the outskirts of the giant Perseus Molecular Cloud, about 850 light-years away.

Other dusty nebulae are scattered around the field of view, along with the faint reddish glow of hydrogen gas.

In fact, the cosmic dust tends to hide the newly formed stars and young stellar objects or protostars from prying optical telescopes.

Collapsing due to self-gravity, the protostars form from the dense cores embedded in the molecular cloud.

At the molecular cloud's estimated distance, this field of view would span over 90 light-years.

Spiral Aurora over Iceland [apod.nasa.gov]

The scene may look like a fantasy, but it's really Iceland.

The rock arch is named Gatklettur and located on the island's northwest coast.

Some of the larger rocks in the foreground span a meter across.

The fog over the rocks is really moving waves averaged over long exposures.

The featured image is a composite of several foreground and background shots taken with the same camera and from the same location on the same night last November.

The location was picked for its picturesque foreground, but the timing was planned for its colorful background: aurora.

The spiral aurora, far behind the arch, was one of the brightest seen in the astrophotographer's life.

The coiled pattern was fleeting, though, as auroral patterns waved and danced for hours during the cold night.

Far in the background were the unchanging stars, with Earth's rotation causing them to appear to slowly circle the sky's northernmost point near Polaris.

Your Sky Surprise: What picture did APOD feature on your birthday? (post 1995)