New Hubble Release: Dramatic Galaxy Collision

Article written: 13 Oct , 2009
Updated: 26 Apr , 2016

At first glance, this latest image release from Hubble appears to be one really bizarre-looking galaxy. But actually, this is a pair of spiral galaxies that resemble our own Milky Way smashing together at breakneck speeds. The centers have already merged into one nucleus, and the two tidal tails stretching out from the center are sparkling with active star formation, prompted by the exchange of mass and gases from the dramatic collision. This object, NGC 2623, or Arp 243, is about 250 million light-years away in the constellation of Cancer (the Crab), and is in the late stages of the merging process.

The prominent lower tail is richly populated with bright star clusters — 100 of them have been found in these observations. The large star clusters that the team has observed in the merged galaxy are brighter than the brightest clusters we see in our own vicinity. These star clusters may have formed as part of a loop of stretched material associated with the northern tail, or they may have formed from debris falling back onto the nucleus. In addition to this active star-forming region, both galactic arms harbor very young stars in the early stages of their evolutionary journey.

Watch this video for more information on NGC 2623:

Some mergers (including NGC 2623) can result in an active galactic nucleus, where one of the supermassive black holes found at the centers of the two original galaxies is stirred into action. Matter is pulled toward the black hole, forming an accretion disc. The energy released by the frenzied motion heats up the disc, causing it to emit across a wide swath of the electromagnetic spectrum.

NGC 2623 is so bright in the infrared that it belongs to the group of very luminous infrared galaxies (LIRG) and has been extensively studied as the part of the Great Observatories All-sky LIRG Survey (GOALS) project that combines data from Hubble, the Spitzer Space Telescope, Chandra X-ray Observatory and the Galaxy Evolution Explorer (GALEX). The combination of resources is helping astronomers characterize objects like active galactic nuclei and nuclear star formation by revealing what is unseen at visible wavelengths.

The data used for this color composite were actually taken in 2007 by the Advanced Camera for Surveys (ACS) aboard Hubble, but is just being released now, as a team of over 30 astronomers, led by Aaron S. Evans, recently published an overview paper, detailing the first results of the GOALS project. Observations from ESA’s X-ray Multi-Mirror Mission (XMM-Newton) telescope contributed to the astronomers’ understanding of NGC 2623.

NGC 2623 paper
GOALS Overview paper
GOALS website

Source: European Hubble website


9 Responses

  1. Jon Hanford says

    Interesting resemblance to the “Antennae” galaxy (NGC 4038-39 = Arp 244). In the linked paper, the researchers mention that this system represents a larger, more distant counterpart to the “Antennae”. For a sense of scale, the bluish starburst region to the upper left of the nucleus is reported to be 60% the size of the LMC (~3.2 kpc) but two times brighter! And further, the paper mentions that ~7% of the 100 Super Star Clusters discovered have luminosities exceeding that of 30 Doradus (the Tarantula Nebula = NGC 2070). So a few of those star clusters in the small starburst region near the nucleus are probably brighter than 30 Dor! Beautiful Hubble image of a distant interacting luminous infrared galaxy.

  2. DrFlimmer says

    Thanks Jon, for the numbers. They give a small feeling of the scales we are dealing with here.


  3. Lawrence B. Crowell says

    I presume galaxy clusters end up being dominated by a single large elliptical galaxy formed from the coalescence of galaxies. Our galaxy is a bit of a galaxy cannibal already, and in about 2 billion years will with Andromeda engage in the sort of tango seen in the numerical simulations. The local group might end up with one large elliptical galaxy with a few dwarf galaxies around it.

    With gravity, entropy increases with clumping. The accumulation of galaxies into large ellipticals at least makes thermodynamic sence.


  4. Jon Hanford says

    @LBC, It does seem that most galaxy clusters with sufficient mass will eventually evolve to have a supermassive galaxy in its midst. Some clusters (like the nearby Coma Cluster) have two of these monster size galaxies that have yet to coalesce into an even larger supergalaxy. Definitely entropy in action.

    Our own Local Group is probably best described as just that, a rather small group of galaxies. But not forever. Observations show that our Local Group is falling towards the massive Virgo Cluster. Whatever becomes of the Milkomeda Galaxy (Andromeda-Milky Way merger) it will eventually be gobbled up by some supergiant galaxy in the Virgo Cluster ( say….M 87 ).

  5. Lawrence B. Crowell says

    Yep, and these hypergalaxies will end up as islands where any observer in them will see other galaxies redshift away and disappear. It might only take 20 billion years for that to happen. Such observers might also notice a much higher frequency of red dwarf stars and collapsed stellar remnants than we observe.


  6. DrFlimmer says

    Such observers might also notice a much higher frequency of red dwarf stars and collapsed stellar remnants than we observe.

    [deep voice on] And when this happens, the ultimate doom is at hand. Prepare for the last day to come – it may be the longest day and a far longer night. [deep voice off]

  7. Lawrence B. Crowell says

    In about 10^{16} years the last of the stars will have winked out, and even by 10^{12} years the night sky in the Androway galaxy will be pretty dark. Things will grind down from there. In about 10^{40} years any region of the universe bounded by the cosmological horizon will consist of one large black hole, and little else. Those will eventually quantum evaporate away by the year 10^{110} . The unvierse will appear as a perfect de Sitter vacuum solution, almost. The cosmological horizon will quantum decay and over an infinite (near infinite?) time frame receed off to infinity. The universe will end up as a Minkowski spacetime or a pure void.

    However, not all is doom! During that long dark time the Hawking radiation from the cosmological horizon has a finite probability for giving rise to “Boltzmann brains.” These are odd entities, but in the year 10^{10^{10^…}}} a random assembly of such quantum states could come about to form a processor (Boltzmann brain), which could spend its existence computing out all possible mathematics.

    Lawrence B. Crowell

  8. DrFlimmer says

    Reminds me of the last chapter in Phil Plait’s book “Death from the sky”. In it he deals exactly with these mind-boggling numbers and the “dark” things that may happen. Somehow, I prefer the shiny situation of today….

  9. Jon Hanford says

    Perhaps those Boltzmann brains could be set to work on Tegmark’s mathematical universe hypothesis ( ) 🙂

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