A stunning new image from the NASA/ESA Hubble Space Telescope shows a collection of galaxies — NGC 1356, LEDA 467699, LEDA 95415 and IC 1947 — in the small southern constellation of Horologium.
This Hubble image shows four spiral galaxies in the constellation of Horologium: the large, prominent spiral galaxy on the right side of the image is NGC 1356; the two apparently smaller spiral galaxies flanking it are LEDA 467699 (above it) and LEDA 95415 (very close at its left) respectively; and finally, IC 1947 sits along the left side of the image. Image credit: NASA / ESA / Hubble / J. Dalcanton, Dark Energy Survey / DOE / FNAL / NOIRLab / NSF / AURA / L. Shatz.
“This image is a really interesting example of how challenging it can be to tell whether two galaxies are actually close together, or just seem to be from our perspective here on Earth,” Hubble astronomers said in a statement.
“A quick glance at this image would likely lead you to think that NGC 1356, LEDA 467699 and LEDA 95415 were all close companions, whilst IC 1947 was more remote.”
“However, we have to remember that 2D images such as this one only give an indication of angular separation: that is, how objects are spread across the sphere of the night sky.”
“What they cannot represent is the distance objects are from Earth,” they noted.
“For instance, whilst NGC 1356 and LEDA 95415 appear to be so close that they must surely be interacting.”
“The former is about 550 million light-years from Earth and the latter is roughly 840 million light-years away, so there is nearly a whopping 300 million light-year separation between them.”
“That also means that LEDA 95415 is likely nowhere near as much smaller than NGC 1356 as it appears to be.”
“On the other hand, whilst NGC 1356 and IC 1947 seem to be separated by a relative gulf in this image, IC 1947 is only about 500 million light-years from Earth.”
“The angular distance apparent between them in this image only works out to less than four hundred thousand light-years, so they are actually much closer neighbors in 3D space than NGC 1356 and LEDA 95415.”
The color image was made from separate exposures taken in the visible and infrared regions of the spectrum with Hubble’s Advanced Camera for Surveys (ACS) and the Dark Energy Camera, which is mounted on NSF’s Víctor M. Blanco 4-m telescope at Cerro Tololo Inter-American Observatory in Chile, a program of NSF’s NOIRLab.
Four filters were used to sample various wavelengths. The color results from assigning different hues to each monochromatic image associated with an individual filter.
