In a similar way than the Moon orbits Earth trapped by its gravitational field, small galaxies can revolve around larger ones. These are then ‘satellites’ of the more massive central galaxy.
Satellite galaxies are more complex than their isolated field counterparts because their properties are linked not only to its own evolution, but also to their response to strong gravitational forces and other environmental effects associated to orbiting within a larger host.
Satellite galaxies infall throughout the whole life-time of the main halo. But only a handful survive and constitute the satellite system that we observe today. Many, the less lucky ones, are incapable of resisting the gravitational forces and get disrupted. Signatures of this history can be found in the “stellar halos” of galaxies, a dim, extended and diffuse component made of loosely bound stars stripped from satellites that disappeared long time ago.
Satellite galaxies are not always alone, but sometimes they infall as part of large associations of dwarfs.
Arp 271 is a pair of interacting spiral galaxies located about 90 million light years away towards the constellation Virgo. Together they are about 130,000 light years across and appear to be connected by a bridge of material.
The two galaxies, NGC 5426 and NGC 5427, are similar, with large spiral arms and a compact core. Because of their similarities, it is probable that neither will be destroyed by the slow collision. As they merge, their stars will likely not collide though gravitational waves will bunch up surrounding gas, leading to the formation of new stars.
is an interacting pair of disk galaxies in the late stages of its
merger. Observations show that both of the galaxies involved were about
the same mass and collided about 700 million years ago in the constellation of Ursa Major. The clash of galaxies caused a rush of star formation and previous Hubble observations showed over 1,000 bright, young star clusters bursting to life at the heart of the galaxy pair.
There’s like 20 other galaxies in this image by the way!
Gravitational Lensing Reveals Major Galaxy Merger in Far Infrared Region
Using data from Hubble, the Gemini South Telescope, Keck, and other observatories, a team with the European Space Observatory managed to use gravitational lensing to observe a distant major merger. The lensed system, H1429-0028, lies in the far infrared and sub millimeter region. One of the team’s aims was to confirm the lensing hypothesis.
With the help of the Gemini South Telescope, the team made long-slit spectroscopic observations. Long-slit spectroscopy is a technique used to observe objects that are stretched out. The slits allow for only a narrow strip of radiation to pass through. It then passes through a prism or a diffraction grating so that the radiation splits into its constituent wavelengths, which, in turn, yields a color spectrum. These observations were used to obtain spectroscopic redshift.
The team used a tip-tilt star at 78" or roughly 20,000 Earth radii northeast of H1429-0028. Stellar parallax is the result of relative motion between a star and the Earth. It can be used to measure distances under one arcsecond or 1/3600th of a degree. The team obtained images of H1429-0028 in sub-arcsecond resolution using the Keck-II LGSAO (laser-guide star-adaptive opitics). The tip-tilt star was then fit into the vignetted field of the sensor. In optics, vignetting reduces the brightness of an image.
H1429-0028 was also observed using Z-SPEC which is mounted on the APEX telescope. The telescope operates between infrared light and radio wave frequencies. Submillimeter astronomy allows for observations in the distant, cold, and dust filled universe. The observations were made at z=1.026, which puts H1429-0028 at a distance of approximately 8,560 MLY (8.56 billion years) away.
In correspondence, Simon Dye explains the roll of the Hubble Space Telescope. “The HST provided near-infrared imaging at 1.1µm [micrometer] wavelength. Since the source being gravitationally lensed lies at a high redshift, going to the near-IR ensures we get a better detection, i.e. a higher S/N image. This is because the source is intrinsically bright in the blue part of the spectrum, but this blue light gets shifted to the near-IR due to its redshift. The image was drizzled, which means that four images were taken, each one offset by half a pixel in x and y. These are then combined to obtain an image which is twice the resolution of the native Wide Field Camera 3 on board the HST.”
Dye also explain the roll of ALMA. “ALMA is a new interferometric facility. Its not fully built yet (there are still antennas being added) but it is already of good enough quality to get some really great data. ALMA is perfect because it has high resolution and works at the wavelengths that the lens systems were originally detected in (you run the risk of not detecting them at other wavelenths). The other nice thing about the data is that ALMA gives you a data cube, rather than just an image. The data cube consists of a series of images, each taken at a slightly different wavelength. In this way, you can trace an emission line (for example CO molecular features) spatially across the image but also in wavelength and this tells you how quickly material is moving in and out of the image at different points across the image.” He adds that “the problem with doing this with the raw data is that the lensed background source is highly distorted and multiply imaged by the foreground lens. By applying the lens reconstruction algorithm to the data cube therefore allows the distortion to be taken out in each image slice so that we can trace how material is moving in the source. The lens acts like a bit magnifying glass so we end up with a much more magnified view of the background source than we would have done if the lens wasn’t there. In fact the maps in fig 9 of the paper wouldn’t be possible without the magnification due to the lens.”
The Antennae Galaxies (NGC 4038/4039) were used as models. Though the interacting galaxies aren’t an exact match, the similarities explain properties of H1429-0028. They also help visualize the background galaxy of H1429-0028. Gravitational lensing observations of large galaxies allow for approximations of gravitational mass based on the effect it has on light from background galaxies. Massive objects deflect light with their gravity. The foreground galaxy is an edge-on disk–like the Sombrero Galaxy (M104)–that’s surrounded by an Einstein ring that’s nearly complete. The foreground galaxy is roughly 2,470 MLY (2.47 billion years) away. With the help of multi-wavelength and high resolution imaging, the lensing hypothesis was confirmed.
Arp 273 is a group of interacting galaxies, lying 300 million light years away in the constellationAndromeda and first discovered in 1966. In this photograph from the Hubble Space Telescope, the larger of the spiral galaxies, known as UGC 1810, has a disk that is tidally distorted into a rose-like shape by the gravitational tidal pull of the companion galaxy below it, known as UGC 1813. A swath of blue jewels across the top is the combined light from clusters of intensely bright and hot young blue stars.
Arp 286 is a set of three interacting galaxies located about 90 million light years away towards the constellation Virgo. The three galaxies are NGC 5566, NGC 5569, and NGC 5560.
NGC 5566 is the larger galaxy at 150,000 light years across. Below it is NGC 5569, while NGC 5560 is being distorted by the gravitational interactions between it and NGC 5566. Galactic interactions like this are common in our universe, and are a normal part of the evolution of galaxies including our own.
With such a long list of muscly human Marvel superheroes to design for Disney Infinity 2.0, I took whatever opportunity I could get to work on non-human characters, just for a change of pace. Rocket Raccoon was definitely one of the most fun to design.
Astronomy Photo of the Day: 12/13/14 — IC 2163 & NGC 2207
Deck the halls with.. gas and dust? These downright festive-looking galaxies are NGC 2207 and IC 2163. They dwell 130 million light-years from Earth, in the constellation of Canis Major. Both galaxies, which were once spiral in nature, are at a pivotal point in their lives, hanging between friendly interaction and an all out merger.
In 15 years alone, NASA’s Chandra X-Ray Observatory has identified 3 separate supernova events, one happens to be “the most bountiful collection of super bright x-ray lights known.” Better known as “ultraluminous X-ray sources” (ULXs), these regions are believed to be associated with binary star systems, or a star locked in a tight orbit around another dense body, usually a neutron star, pulsar or a stellar-mass black hole.
Immense gravitational forces see the denser body pull stellar material from the star’s outer-envelope. As it inches toward the body in question, the material is heated up substantially, reaching several millions of degrees in temperature, whilst emitting x-rays that can be picked up by Chandra.
In this newly-released composite, optical data from Hubble is represented in green, red and blue (appearing as blue, white, orange and brown, according to NASA), x-ray data from Chandra is seen in pink, and the infrared data , gathered by NASA’s Spitzer Space Telescope, is seen in red.
NGC 1569 is a dwarf galaxy located about 11 million light years away towards the constellation Camelopardalis. It is part of a group of about 10 galaxies centered on IC 342, and the gravitational attractions between these may contribute to its high rate of star formation.
NGC 1569 has a very high rate of star formation, 100 times that of the Milky Way. This probably started around 25 million years ago, and has created several young star clusters. The turbulence is further fed by supernova explosions as more massive stars end their lives, sending out material and triggering more star formation.
UGC 8335 is a strongly interacting pair of spiral galaxies resembling two ice skaters. The interaction has united the galaxies via a bridge of material and has yanked two strongly curved tails of gas and stars from the outer parts of their bodies . Both galaxies show dust lanes in their centers. UGC 8335 is located in the constellation of Ursa Major, the Great Bear, about 400 million light-years from Earth.
A new form of diffuse galaxy has been discovered inside the Coma Cluster. This place is made 99.99% of dark matter, totally invisible as it doesn’t interact with light.
The galaxy is known as Dragonfly 44 and was discovered by astronomers Pieter van Dokkum and his colleagues.
The way star systems orbit around the center of a galaxy is inexplicable with “normal” physics. To account for the velocity variations and patterns we need to add a new ingredient to the gravitational pot: dark matter.
Dragonfly 44 in particular has so few stars that were the dark matter to be taken away, the galaxy would fly apart the same way you’d go flying if the cord holding the swing to a swing set were severed.
The Whirlpool Galaxy and Beyond : Follow the handle of the Big Dipper away from the dippers bowl, until you get to the handles last bright star. Then, just slide your telescope a little south and west and you might find this stunning pair of interacting galaxies, the 51st entry in Charles Messiers famous catalog. Perhaps the original spiral nebula, the large galaxy with well defined spiral structure is also cataloged as NGC 5194. Its spiral arms and dust lanes clearly sweep in front of its companion galaxy , NGC 5195. The pair are about 31 million light-years distant and officially lie within the angular boundaries of the small constellation Canes Venatici. Though M51 looks faint and fuzzy to the human eye, the above long-exposure, deep-field image taken earlier this year shows much of the faint complexity that actually surrounds the smaller galaxy. Thousands of the faint dots in background of the featured image are actually galaxies far across the universe. via NASA
NGC 5775 is a spiral galaxy located about 85 million light years away towards the constellation Virgo. It is part of the Virgo Cluster of galaxies, along with nearby NGC 5574, which it is starting to merge with. Though neither galaxy yet shows a tidal tail, a common feature of strongly interacting galaxies, bridges of hydrogen gas have been observed stretching between the two.
From our position on Earth, we see NGC 5775 edge on. This limits our view of its spiral structure, arms, and core, but offers new insights into the galactic halo, seen around galaxies with high star formation. The formation and persistence of this cloud of hot gas surrounding the galaxy is unknown, though it is theorized to act like a fountain- supernovae push hot gas out of the disk, which returns when it cools.
The M81 Group - Bodes Galaxy (M81) and the Cigar Galaxy (M82)
Bodes Galaxy, also known as NGC 3031 or M81, is a spiral galaxy about 12 million light-years away in the constellation Ursa Major. In this image Bodes Galaxy is on the bottom. Due to its proximity to Earth, large size and active galactic nucleus (which harbors a 70 million M☉ supermassive black hole), Messier 81 has been studied extensively by professional astronomers. The galaxy’s large size and relatively high brightness also make it a popular target for amateur astronomers.
The Cigar Galaxy, also known as NGC 3034 or M82, is a starburst galaxy about 12 million light-years away in the same constellation the previously mentioned M81. It is about five times more luminous than the whole Milky Way and one hundred times more luminous than our galaxy’s center. The starburst activity is thought to be triggered by interaction with neighboring galaxy M81, and M82 is a member of the M81 Group. As the closest starburst galaxy to our own, M82 is the prototypical example of this type of galaxy.