The twin galaxies NGC 4496A and NGC 4496B.
ESA/Hubble & NASA, T. Boeker, B. Holwerda, Dark Energy Survey, DOE, FNAL/DECam, CTIO/NOIRLab/NSF/AURA, SDSS Acknowledgement: R. Colombari
These galaxies aren’t situated anywhere near each other, except by a happy alignment coincidence.
What you’re seeing here is NGC 4496A and NGC 4496B in the sharp eyes of the Hubble Space Telescope, visible in an image taken by the famed observatory. They appear to be right next to one another in the image, but in reality they are quite far apart; 4496A is 47 million light-years from Earth, while 4496B is 212 million light-years away.
These two galaxies are too far apart for even their vast gravities to cause influences in one another, but their chance alignment does present a unique opportunity to astronomers, the European Space Agency said in a release. Specifically, we can learn more about dust distribution in the galaxies, which in turn leads to a better understanding of the history of our universe and the objects within it.
The Hubble Space Telescope.
Getty Images
Dust can be a nuisance if you’re looking at something in visible wavelengths, because the dust dims starlight and makes distant objects even more difficult to see. Additionally, dust absorbs light in such a way that longer wavelengths are preferred, which is a process called “reddening.” (That’s different from redshift, or the phenomenon during which objects receding from us quickly have wavelengths trending towards the red edge of the spectrum.)
If you have an instrument like Hubble that can view infrared light, however, dust isn’t so much of an issue. In fact, it’s an asset, ESA points out: “By carefully measuring how starlight from background galaxies is affected by dust in intervening galaxies, astronomers can map out where the dust is in the foreground galaxy’s spiral arms,” the agency stated. “The resulting ‘dust maps’ help astronomers calibrate measurements of everything from cosmological distances to the types of stars populating galaxies.”
While ESA didn’t mention other observatories in particular, do note that the recently launched James Webb Space Telescope is optimized for infrared wavelengths to an even greater degree to Hubble. Webb is still in commissioning and early in its projected 20-year lifespan. But it may well be that a future round of science proposals allows Webb to gaze at these galaxies, or galaxies much like it, to gain even more insights.
Webb has an additional observational advantage to Hubble, being located in deep space, but at the same time there’s a challenge; the newly launched telescope is far out of reach of astronaut repairs. That said, Webb is doing tremendously well with its commissioning period and is in excellent health, allowing for a long period of observations before its fuel runs out or its instruments encounter problems, based on what we’ve seen so far. We’ll start observations on Webb in the summer.
