The Tadpole Galaxy

Arp 188, aka the Tadpole Galaxy, is a disrupted barred spiral galaxy about 420 million light-years from Earth . Its most noticeable feature is a massive tail of stars about 280,000 light-years long. Astronomers believe that the tail was formed about 100 million years ago by a merger or near merger of two galaxies.

A more compact galaxy crossed in front of a larger one and was partially strung out behind the resulting Tadpole by the gravitational interactions.

Image Credit: NASA / ESA

Young Stars and Old Timers

Stars in SagittariusThe Hubble Space Telescope took this picture of a group of stars in the constellation of Sagittarius. Blue stars can be seen scattered across the frame, set against a backdrop of red companions. This blue stars are young, most likely formed at the same time from the same collapsing molecular cloud.

Red stars are much cooler than the sun, so they are either at the end of their lives or they are much less massive. These lower-mass stars are called red dwarfs and are thought to be the most common type of star in the Milky Way. The blue stars are hot. They are either young or very massive, many times the mass of the Sun.

A star’s mass decides its lifespan. Massive stars burn brightly over a short lifespan and die after only tens of millions of years. Yellow stars like the Sun typically live longer, burning for approximately ten billion years. Smaller stars, on the other hand, live life in the slow lane and may exist for trillions of years.

Image Credit: NASA

Tethys Takes a Look at Saturn

Tethys and SaturnIn this picture taken by the Cassini spacecraft the two large craters on Tethys near the line where day fades to night seem to be looking at Saturn. (Click the image to embiggen it.)

The shadowing on the craters caused by being near Tethys’ terminator throws their topography into sharp relief. The larger, southernmost of the two shows a more complex structure. Its central peak is  probably the result of the surface reacting to the violent post-impact excavation of the crater. The northern crater doesn’t have a similar feature. The impact was likely too small to form a central peak, or the composition of the material in the immediate vicinity couldn’t support the formation of a central peak.

Image Credit: NASA

The Rotation of Neptune

This video is a full-globe map of Neptune created from Hubble Space Telescope data taken in January, 2020. The planet completes a rotation every 16 hours.

Neptune has dynamic weather. White clouds of methane ice crystals swirl around the planet, and two giant dark spots, giant storms, circle around the northern hemisphere. Around the southern pole, banding is concentrated where the winds are blowing west to east, in the same direction as the planet’s rotation. but near the equator, the winds blow east to west, in the opposite direction as the planet’s rotation.

The giant vortex near the equator is 4,600 miles across, wider than the Atlantic Ocean. Its slightly smaller companion is 3,900 miles across.

Video Credit: STScI

You Can’t See This From Here

PlutoNightNew Horizons was about 21,000 kilometers beyond Pluto, about 19 minutes after its closest approach, when it took this picture. The image also reveals Pluto’s tenuous and complex layers of hazy atmosphere. The crescent twilight landscape near the top of the frame are areas on the south of the planet including the nitrogen ice plains informally known as Sputnik Planum and rugged mountains of water-ice in the Norgay Montes.

Image Credit: NASA

A Nearby Cluster

FornaxClusterNamed for the southern constellation in whose part of the sky most of its galaxies can be found, the Fornax Cluster is one of the closest clusters of galaxies. At an average of 62 million light-years away, it is almost 20 times more distant than the nearby Andromeda Galaxy. Almost every yellow blob in this two-degree-wide image is an elliptical galaxy in the cluster. The barred spiral galaxy NGC 1365 that stands out in the lower right is a member of the cluster.

Image Credit: ESO

A Lonely Galaxy

0105-4x5color.aiMost galaxies are clumped together in groups or clusters, but NGC 6503 is in a lonely position at the edge of a strangely empty patch of space called the Local Void. The Local Void is a region of space over 150 million light-years across that is essentially empty of stars or galaxies. NGC 6503 is 18 million light-years away from us in the constellation Draco. It’s about 30,000 light-years or a third of the size of the Milky Way.

Image Credit: NASA / ESA

Mergers and Acquisitions

Arp 299 is a pair of colliding galaxies. Both of them are classified as barred irregular galaxies. The interaction of the two galaxies is producingstarburst regions. Data from the Chandra X-Ray Observatory reveals 25 bright X-ray sources in Arp 299. The image above combines X-ray data from Chandra (pink), higher-energy X-ray data from NuSTAR (purple), and optical data from the Hubble Space Telescope (white and faint brown).

Image Credit: NASA

A Butterfly

butterfly_hstThis is NGC 6302 (aka The Butterfly Nebula). It is approximately 4,000 light-years from Earth in the constellation Scorpius (the Scorpion). With an estimated surface temperature of about 250,000 °C, the dying central star of this planetary nebula shines brightly in ultraviolet light, but it’s hidden from direct view by a dense doughnut-shaped cloud of dust. This close-up of the nebula was taken by the Hubble Space Telescope‘s Wide Field Camera 3 which was installed during the final shuttle servicing mission. The dust torus surrounding the central star is near the center of this view, almost edge-on to our line-of-sight. Click on the image to embiggen it.

Image Credit: NASA

Asteroids!

idamoonThis color mosaic shows the asteroid Ida and its moon Dactyl. The images use to assemble this picture were taken by the camera system on the Galileo spacecraft as it was passing through the Asteroid Belt in 1993. Ida is about 52 km in length and, as you can see, is irregularly shaped. The image shows many craters, including quite a few degraded ones, indicating Ida’s surface is older than previously thought.

Dactyl was discovered in the series of images Galileo recorded over an observation period of 5.5 hours during the 1993 flyby of Ida. Dactyl’s longest dimension is about 1.6 km.

Image Credit: NASA

Mimas

Mimas is one of Saturns moons. It’s about 130 km in diameter, one of the smallest bodies in the Solar System with sufficient gravity to pull itself into a spherical shape. This picture was taken in 2010 by the Cassini spacecraft.

The Gentle Reader may make his own moon-not-a-space-station or AT&T-naming-rights jokes.

Image Credit: NASA

Mergers and Acquisitions

The messy result of a galactic collisionThis is a collision between two galaxies—a spiral galaxy and a lenticular galaxy. There’s an almost 3D appearance to the picture as the spiral arms embrace the lenticular galaxy’s bulge.

There’s more evidence of the collision in the image. Look at the stream of stars coming out from the merging galaxies toward the top of the image. The bright spot in the middle of the plume is the unique feature of this collision. That spot is believed to be the former nucleus of the spiral galaxy ejected from the system during the collision. It’s now being disassembled by tidal forces producing the stream of stars.

Image Credit: NASA

A Broad Spectrum Pinwheel

When I worked in the audio business, we used to jokingly describe a wide band system as working from dc to daylight. This picture of the M101 (aka, the Pinwheel Galaxy) uses images take in the infrared, visible, ultraviolet and X-rays from four of NASA’s space-based telescopes. The wide-spectrum view shows that both young and old stars are evenly distributed along the galaxy’s spiral arms. Composite images allow astronomers to see how features in one part of the spectrum match up with those seen in other parts. It is like seeing with IR night-vision goggles, a regular camera, an ultraviolet camera, and X-ray vision, all at the same time.

The Pinwheel Galaxy is in the constellation of the Big Dipper. It is about 70 percent larger than our own Milky Way Galaxy about 21 million light years from Earth.

Image Credit: NASA

Hyperion

HyperionHyperion is one of Saturn’s moons. It is named for one of the Titans who was the Greek god of watchfulness and observation and the older brother of Cronus. Saturn was the analog of Cronus in Roman mythology.

Hyperion is one of the largest irregularly shaped bodies in the Solar System, and it rotates chaotically, tumbling unpredictably as it orbits Saturn. That made it  challenging to target a specific region of the moon’s surface for observation by the Cassini spacecraft, and most of Cassini‘s approaches saw the same side of the craggy moon. The view above is from a closest encounter in 2005.

BTW, the first time I saw this picture, I was reminded of a wasps’ nest.

Image Credit: NASA