After arriving at the Tines homeworld and allying with Woodcarver to defeat Steel, Pham initiates the Countermeasure, which extends the " Slow Zone " – the inner region of the galaxy where the highest technologies, such as artificial intelligence and superluminal travel, are impossible – by thousands of light-years to enclose the Blight.

A common analogy explains that space itself is expanding, carrying galaxy | galaxies with it, like spots on an inflating balloon.

However, there are some exceptions: many of the stars in the constellation of Ursa Major ( including most of the Big Dipper ) are genuinely close to one another, travel through the galaxy with similar velocities, and are likely to have formed together as part of a cluster that is slowly dispersing.

Cosmologists study these simulations to see if they agree with the galaxy surveys, and to understand any discrepancy.

The face-on spiral galaxy is experiencing abnormally high rates of star formation, indicating that it is interacting with one or both members of the group.

NGC 2403 is a galaxy in the M81 group of galaxies, located approximately 12 million light-years from Earth with a redshift of 0. 00043.

MS0735. 6 + 7421 is a galaxy cluster with a redshift of 0. 216, located 2. 6 billion light-years from Earth.

Astronomers theorize that a collision with a smaller companion galaxy near the core of the main galaxy could have led to the unusual spiral structure.

Astronomers posit that its dust lanes, not common in elliptical galaxies, are due to a previous merger with another galaxy, probably a spiral galaxy.

NGC 5128 appears in the optical spectrum as a fairly large elliptical galaxy with a prominent dust lane.

It is a spiral galaxy with an integrated magnitude of 9. 0.

M94 is a small face-on spiral galaxy with an approximate magnitude of 8. 0, about 15 million light-years from Earth.

Norstrilians are nominally the richest people in the galaxy and defend their immensely valuable stroon with sophisticated weapons ( as shown in the story " Mother Hitton's Littul Kittons ").

However, a sufficiently sensitive radio telescope shows a faint background glow, almost exactly the same in all directions, that is not associated with any star, galaxy, or other object.

: N = the number of civilizations in our galaxy with which communication might be possible ;

It is notable as a Seyfert galaxy with strong spectral emissions indicating ionized gases and a central supermassive black hole.

The bright nucleus indicates the presence of an active galactic nucleus-a galaxy with a supermassive black hole at the center, accreting matter from the bar.

It is a 10th magnitude galaxy associated with the Fornax Cluster.

Fornax A is a radio galaxy with extensive radio lobes that corresponds to the optical galaxy NGC 1316, a 9th-magnitude galaxy.

One of the closer active galaxies to Earth at a distance of 80 million light-years, Fornax A appears in the optical spectrum as a large elliptical galaxy with dust lanes near its core.

These dust lanes have caused astronomers to discern that it recently merged with a small spiral galaxy.

A galaxy is a massive, gravitationally bound system consisting of stars, stellar remnants, an interstellar medium of gas and dust, and an important but poorly understood component called dark matter.

An Sa galaxy has tightly wound, poorly defined arms and possesses a relatively large core region.

For galaxies ( which are of course themselves much larger than 10 parsecs, and whose overall brightness cannot be directly observed from relatively short distances ) the absolute magnitude is defined by reference to the apparent brightness of a point-like or star-like source of the same total luminosity as the galaxy, as it would appear if observed at the standard 10 parsecs distance.

By convention, is ten times the ellipticity of the galaxy, rounded to the nearest integer, where the ellipticity is defined as for an ellipse with semi-major and semi-minor axes of lengths and respectively.

Hubble defined two classes of irregular galaxy:

An additional subtlety is that a galaxy at a given comoving distance is defined to lie within the " observable universe " if we can receive signals emitted by the galaxy at any age in its past history ( say, a signal sent from the galaxy only 500 million years after the Big Bang ), but because of the universe's expansion, there may be some later age at which a signal sent from the same galaxy can never reach us at any point in the infinite future ( so for example we might never see what the galaxy looked like 10 billion years after the Big Bang ), even though it remains at the same comoving distance ( comoving distance is defined to be constant with time — unlike proper distance which is used to define recession velocity due to the expansion of space ) which is less than the comoving radius of the observable universe.

The science of physical cosmology as it is practiced today had its subject material defined in the years following the Shapley-Curtis debate when it was determined that the universe had a larger scale than the Milky Way galaxy.

The galaxy contains two clearly defined spiral arms and is therefore used as an archetypal example of a Grand Design Spiral Galaxy.

It is classified as being between an elliptical and a spiral galaxy because it has faint arms and a large central bulge.

Its spiral arms wind in both directions, which makes it nearly impossible for astronomers to determine the rotation of the galaxy.

At the other extreme, an Sc galaxy has open, well-defined arms and a small core region.

Large scale carbon monoxide maps of the galaxy show that the position of this gas correlates with the spiral arms of the galaxy.

The predominant theory regarding its formation is that the progenitor galaxy was a barred spiral galaxy whose arms had a velocity too great to keep its coherence and therefore detached.

It is only within this more recent time that passages of the heliosphere through the spiral arms of the galaxy have been able to gain a strong and regularly modulating influence as described above.

Calculations suggest that the cluster will take about 250 million years to disperse, with gravitational interactions with giant molecular clouds and the spiral arms of our galaxy also hastening its demise.

A groove on a record or the arms of a spiral galaxy ( a Logarithmic spiral ) are examples of a spiral.

Messier 100 is considered an starburst galaxy, with it concentrated within a ring-actually two tightly wound spiral arms attached to a small nuclear bar with a radius of 1 kilo-parsec -, where star formation has been taking place since at least 500 million years ago in separate bursts.

Depending on the category, a galaxy may have one or more distinct features, such as spiral arms, a halo and a nucleus.

In general elliptical galaxies appear yellow-red, which is in contrast to the distinct blue tinge of a typical spiral galaxy, a colour emanating largely from the young, hot stars in its spiral arms.

Bertil Lindblad proposed that the arms represent regions of enhanced density ( density waves ) that rotate more slowly than the galaxy ’ s stars and gas.

Explanation of spiral galaxy arms.

They suggested that the spiral arms were manifestations of spiral density waves, attempting to explain the large-scale structure of spirals in terms of a small-amplitude wave propagating with fixed angular velocity, that revolves around the galaxy at a speed different from that of the galaxy's gas and stars.

A flat rotation curve emerges quite naturally in a galaxy governed by electromagnetic fields, the spiral arms of galaxies are like rolling springs that have the same rotational velocity along their length.

* IC 469 is another spiral galaxy, characterized by a compact nucleus, of oval shape, with perceptible side arms.