This image from the Hubble Space Telescope shows the spiral arms of the galaxy NGC 7038 winding languidly across space. Located about 220 million light-years from Earth, NGC 7038 lies in the southern constellation Indus.
With an incredibly rich and intricately detailed view of a spiral galaxy, this image also exposes a huge number of distant stars and galaxies around it. That’s because it’s made from a combined 15 hours worth of NASA/ESA Hubble time focused on NGC 7038 and collecting light. So much data indicates that this is a valuable target, and indeed, NGC 7038 has been particularly helpful to astronomers measuring distances at vast cosmic scales.
Using an interconnected chain of measurement techniques called the Cosmic Distance Ladder, researchers are able to determine distances to astronomical objects. Each rung in the ladder is calibrated by earlier steps, based on measurements of objects closer to us. Therefore, the accuracy of distances at the largest scales is dependent on how accurately distances to nearby objects can be determined. Hubble inspected NGC 7038 with its Wide Field Camera 3 (WFC3) to calibrate two of the most common distance measurement techniques: type 1A supernovae and Cepheid variables.
One of Hubble’s original science goals was to accurately establish distances to night-sky objects, and throughout the course of its three decades of operation, Hubble’s increasingly precise distance measurements have contributed to one of the most intriguing unsolved problems in astronomy. The Hubble constant, which captures the rate of expansion of the Universe, is derived from distance measurements.
As astronomers’ measurements of the Hubble constant have become more precise, their value has become increasingly inconsistent with the value of the Hubble Constant derived from observations of the Big Bang’s afterglow. Astronomers have been unable to explain the mismatch between the two values of the Hubble constant, which suggests that a new discovery in cosmology is waiting to be made.