Atlas of Peculiar Galaxies

Here are some fun and unusual galaxies from the Atlas of Peculiar Galaxies, a catalog produced by Halton Arp. A total of 338 galaxies are presented in the atlas, which was originally published in 1966.

1. IC 883 (Arp 193), remnant of two galaxies’ merger    
2. Arp 147, an interacting pair of ring galaxies
3. Giant elliptical galaxy NGC 1316
4. Interacting pair of galaxies: Arp 238 (UGC 8335
5. Merging galaxy pair named NGC 520 (Arp 157)

Southern Craters and Galaxies : The Henbury craters in the Northern Territory, Australia, planet Earth, are the scars of an impact over 4,000 years old. When an ancient meteorite fragmented into dozens of pieces, the largest made the 180 meter diameter crater whose weathered walls and floor are lit in the foreground of this southern hemisphere nightscape. The vertical panoramic view follows our magnificent Milky Way galaxy stretching above horizon, its rich central starfields cut by obscuring dust clouds. A glance along the galactic plane also reveals Alpha and Beta Centauri and the stars of the Southern Cross. Captured in the region’s spectacular, dark skies, the Small Magellanic Cloud, satellite of the Milky Way, is the bright galaxy to the left. Not the lights of a nearby town, the visible glow on the horizon below it is the Large Magellanic Cloud rising. via NASA


Space Weather

 To the casual observer, the Sun may appear unimpressive from 93 million miles (150 million km - 1 AU) away but upon closer examination – in the extreme ultraviolet region of the spectrum, it becomes evident that it’s characterized by unpredictable and explosive surface activity. The Sun creates highly variable and complex conditions in the space, as well. We call these conditions ‘space weather’. Space weather is an emerging multidisciplinary field within space sciences that studies how solar activity influences Earth’s space environment.

  Our Sun continuously bathes Earth in solar energy, in the forms of: electromagnetic radiation (visible light, microwaves, radio waves, infrared, ultraviolet, X-ray, gamma rays) and corpuscular radiation (streams of subatomic particles such as protons, electrons, and neutrons). The Sun is a magnetic variable star, and like most stars, it’s composed of superheated plasma; a collection of negatively charged electrons and positively charged ions. Its magnetic fields are produced by electric currents that are generated by the movement of the charged particles. The electrically conductive solar plasma acts like a viscous fluid, so the plasma near the poles rotates slower than the plasma at the equator. This differential rotation results in a twisting and stretching of the magnetic field lines, leading to the formation of sunspots, solar flares and CMEs.

The Sun’s overall magnetic field is quite weak compared to sunspots, which are localized regions of intense magnetism (magnetic loops that poke out of the photosphere), and they can be 1000 times stronger than the Sun’s average field. Above sunspot regions, the Sun’s magnetic field lines twist and turn like rubber bands, and when the field lines interact, the confined coronal plasma is accelerated to several million miles per hour in a powerful magnetic eruption. The cloud of extremely hot and electrically charged plasma expelled from the active region is called a coronal mass ejection, or CME for short. CMEs aimed at Earth are called halo events or halo CMEs because of the way they look in coronagraph images; the coronagraph instrument will detect it as a gradually expanding ring around the Sun. As the CME moves away from the Sun, it pushes an interplanetary shock wave before it, amplifying the solar wind speed, and magnetic field strength, as well. The Sun’s magnetic field isn’t confined to the star, the interplanetary magnetic field (IMF) is carried into interplanetary space by the solar wind and CMEs.

Depending on how the IMF is aligned in relationship to our geomagnetic field, there can be various results when the CME arrives. Some particles get deflected around Earth – thanks to the invisible magnetic “bubble”, called the magnetosphere (it’s actually non-spherical), but a small amount of ionized particles can still get into our near-Earth environment (geospace), mostly via the magnetotail. The magnetosphere is formed when the flow of the solar wind impacts the Earth’s magnetic (dipole) field. The overall shape of Earth’s magnetosphere is influenced by the speed, density and temperature of the solar wind: the dayside is continuously compressed by the solar wind, and the nightside is stretched out into a tear drop shaped magnetotail. Our magnetosphere is an extremely dynamic region and it’s filled with a variety of current systems.

When a powerful CME hits Earth, electrons in the magnetosphere cascade into the ionosphere at the polar regions, creating the so-called Birkeland or field-aligned current that flows along the main geomagnetic field. If the CME’s polarity matches that of Earth’s magnetic field (Northward IMF), our magnetosphere may deflect some of the highly charged particles. The problems occur when the CME’s polarity is the opposite of Earth’s (Southward IMF) because it can cause a geomagnetic storms and brief magnetospheric substorms that disrupt Earth’s own magnetic environment.

 Changes in the ionosphere trigger bright aurorae that are, in fact, the visual manifestation of the interaction between solar energetic particles and the high-altitude atmosphere. Solar energetic particles are high-energy charged particles, they can induce voltages and currents in power grids and cause large-scale power and radio blackouts, temporary operational anomalies, damage to spacecraft electronics. During geomagnetic storms, the energy transferred into the ionosphere by the Birkeland current heats up (Joule heating) the atmosphere, which consequently rises and increases drag on low-altitude satellites.

 Fortunately, there is a fleet of observing spacecraft monitoring the Sun’s activity across a wide range of electromagnetic wavelengths. Their continuous observations and measurements of solar and geospace variability gives us the ability to prepare and respond to potentially harmful space weather events.

Related Links:

Doomed Star Eta Carinae : Eta Carinae may be about to explode. But no one knows when - it may be next year, it may be one million years from now. Eta Carinae’s mass - about 100 times greater than our Sun - makes it an excellent candidate for a full blown supernova. Historical records do show that about 150 years ago Eta Carinae underwent an unusual outburst that made it one of the brightest stars in the southern sky. Eta Carinae, in the Keyhole Nebula, is the only star currently thought to emit natural LASER light. This featured image, taken in 1996, brought out new details in the unusual nebula that surrounds this rogue star. Now clearly visible are two distinct lobes, a hot central region, and strange radial streaks. The lobes are filled with lanes of gas and dust which absorb the blue and ultraviolet light emitted near the center. The streaks remain unexplained. via NASA


“We are really witnessing the opening of a new tool for doing astronomy. We have turned on a new sense.
We have been able to see and now we will be able to hear as well.”

Karachi-born quantum astrophysicist Nergis Mavalvala, a member of the team that announced on Thursday the scientific milestone of detecting gravitational waves, ripples in space and time

Image:  Nergis Mavalvala, center, next to MIT physics professor Matthew Evans, left, and MIT research scientist Erik Katsavounidis, right, Feb. 11, 2016, in Cambridge, Mass. — AP

In the Heart of the Virgo Cluster : The Virgo Cluster of Galaxies is the closest cluster of galaxies to our Milky Way Galaxy. The Virgo Cluster is so close that it spans more than 5 degrees on the sky - about 10 times the angle made by a full Moon. With its heart lying about 70 million light years distant, the Virgo Cluster is the nearest cluster of galaxies, contains over 2,000 galaxies, and has a noticeable gravitational pull on the galaxies of the Local Group of Galaxies surrounding our Milky Way Galaxy. The cluster contains not only galaxies filled with stars but also gas so hot it glows in X-rays. Motions of galaxies in and around clusters indicate that they contain more dark matter than any visible matter we can see. Pictured above, the heart of the Virgo Cluster includes bright Messier galaxies such as Markarians Eyes on the upper left, M86 just to the upper right of center, M84 on the far right, as well as spiral galaxy NGC 4388 at the bottom right. via NASA