#barred galaxy

[timbercow]

Space jaws hunting a space seal. Based on NGC 1427A for the shark, and the Antennae Galaxies for the seal.

[therealuniverse]

MESSIER 91 GALAXY M91 (NGC 4548) is a faint barred spiral galaxy in the constellation Coma Berenices and is a member of the Virgo Galaxy Cluster. The galaxy lies about 55 million light years from Earth. It has a very prominent bar structure connected to two outer arms that trail stars and interstellar dust. The distribution of the atomic gas shows a ring-like structure.

When Charles Messier was observing and logging deep space objects on the night of March 18, 1781, chances are very good that M91 was what he was describing when he recorded: “Nebula without stars, fainter than M90″. But, there was a problem… Charles Messier made a rare bookkeeping mistake and logged its position wrong. So, for a long time M91 was a missing Messier object, as Messier had determined its position from M89 while he thought it was from M58. M91 was catalogued as H II.120 by William Herschel in 1784. Navigating using the directions that Messier initially, yet erroneously logged, Herschel thought the object to be NGC 4571, a beautiful but faint barred spiral galaxy. The identity of M91 was corrected by observations by astronomer William C. Williams in 1969. Prior opinions have been that M91 had either been a comet which the great comet hunter Messier mistook for a nebula. Measurements done by the Hubble Space Telescope indicate that M91 is moving away from us at a speed of about 400 km/s (895,000 mph). The galaxy’s particular speed is unusual because the Virgo Cluster is moving away from us at a speed of 1100 km/s (2.4 million mph), indicating M91 must be traveling toward us at 700 km/s (1.5 million mph) relative to the other galaxies in the Virgo Cluster. -JMP http://www.universetoday.com/48349/messier-91/ http://messier.seds.org/m/m091.html Image Credit: Kitt Peak National Observatory (Haynes)/NOAO/AURA/NSF

[thetimeandspaceblog]

Hubble Spots a Curious Spiral

The universe is simply so vast that it can be difficult to maintain a sense of scale. Many galaxies we see through telescopes such as the NASA/ESA Hubble Space Telescope, the source of this beautiful image, look relatively similar: spiraling arms, a glowing center, and a mixture of bright specks of star formation and dark ripples of cosmic dust weaving throughout.

This galaxy, a spiral galaxy named NGC 772, is no exception. It actually has much in common with our home galaxy, the Milky Way. Each boasts a few satellite galaxies, small galaxies that closely orbit and are gravitationally bound to their parent galaxies. One of NGC 772's spiral arms has been distorted and disrupted by one of these satellites (NGC 770 - not visible in the image here), leaving it elongated and asymmetrical.

However, the two are also different in a few key ways. For one, NGC 772 is both a peculiar and an unbarred spiral galaxy; respectively, this means that it is somewhat odd in size, shape or composition, and that it lacks a central feature known as a bar, which we see in many galaxies throughout the cosmos - including the Milky Way. These bars are built of gas and stars, and are thought to funnel and transport material through the galactic core, possibly fueling and igniting various processes such as star formation.

Text credit: ESA (European Space Agency)

Image credit: ESA/Hubble & NASA, A. Seth et al.

Hubble Space Telescope

Time And Space

[thefirststarr]

This is M95. It is a barred spiral galaxy found 33 million light-years away! Its arms play host to a large amount of star formation.

Image Credit & Copyright: NASA, ESA, STScI, and D. Calzetti (University of Massachusetts, Amherst) and R. Chandar (University of Toledo)

[chibinotan]

Wide-Field Galaxy

[timbercow]

Details of the extra galaxies in my Space Jaw piece.

[therealuniverse]

Barred Spiral Galaxies This is a shot from the Hubble Space Telescope showing Barred Spiral Galaxy NGC 4394. This one is located about 55 million light years from us, and along with the Milky Way is a member of the large Virgo Cluster of galaxies. Barred galaxies are extremely common in the universe and have been described going back to the original classification for galaxies set up by astronomer Edwin Hubble. This particular galaxy would be described as an SBb galaxy – a Spiral Barred galaxy with the extra b referring to how well defined the bar is.

A bar is thought to be a stage in the evolution of a spiral galaxy. Evidence from the Hubble Telescope shows that about 60% of nearby spiral galaxies have bars at their centers, but at high redshift (meaning great distances from us or earlier in the universe’s history) only 30% of spiral galaxies have bars, indicating that they are a signature of spiral galaxies becoming mature. Bars are thought to serve as active conduits that reshape spiral galaxies. They allow the transfer of accreted gas from the outer part of the galaxy to the inner region, while also exchanging angular momentum outwards to keep the galaxy in balance. The presence of a bar therefore triggers an increase in the formation rate of new stars near the center of a galaxy, which in turn increases the size of the galactic bulge at the galaxy’s center and also eventually increases the metallicity of the galaxy due to the burst of star formation. The exact details of bar formation are still being studied; scientists agree that they are produced by resonances or waves in the dust in the galaxy created as material moves around the central galactic core. Simulations show that galaxies can form and destroy bars, sometimes over and over, as pulses of gas move through the galaxy, and in some cases they could last as long as 10 billion years. In the 1970s, researchers realized that the stars in our own Milky Way galaxy were not moving in the correct directions for the spiral arms to reach all the way to the galactic center. Instead, our own galaxy hosts a bar at the center that connects to the spiral arms; it isn’t as prominent as the one in this image, but it is there. -JBB Image credit: https://www.nasa.gov/image-feature/goddard/2016/hubble-spies-the-barred-spiral-galaxy-ngc-4394 References: http://articles.adsabs.harvard.edu/full/2005A%26G....46f..28K/F000030.000.html https://academic.oup.com/mnras/article/463/1/1074/2590000 https://academic.oup.com/mnrasl/article/369/1/L56/1003619 https://www.aanda.org/articles/aa/abs/2002/34/aa2271/aa2271.html

[chibinotan]

Future Galactic Merger