Search & fact check with cited sources for What does the July 24, 2026 Hubble Space Telescope image of NGC 4654 reveal about the galaxy's lopsided structure, what two cosmic processes caused its asymmetry, and what data from Hubble observing programs are researchers using to stud

The July 24, 2026 Hubble Space Telescope image of NGC 4654 reveals a markedly one-sided, asymmetric spiral galaxy whose lopsided structure was produced by a combination of ram-pressure stripping from the intracluster medium and a past gravitational tidal encounter with its neighboring galaxy NGC 4639. Researchers are studying this galaxy using Hubble data from a multi-wavelength observing program focused on the star formation and stellar feedback cycle in nearby galaxies, along with archival data from the Hubble Legacy Archive and complementary radio/submillimeter observations.

What the image reveals about the lopsided structure

• NGC 4654 is an intermediate spiral galaxy about 72 million light-years away in the constellation Virgo . The term "intermediate" means it has characteristics of both unbarred and barred spirals .
• The galaxy is particularly asymmetric: it has a rounded, clearly defined edge on one side and a long tail of gas stretching out from the opposite side — the tail extends beyond Hubble's field of view in this image .
• This "one-sided spiral" appearance is the hallmark visual feature described in NASA's July 24, 2026 release .

The two cosmic processes that caused the asymmetry

1. Ram-pressure stripping — As NGC 4654 moves through the hot intracluster medium of the Virgo Cluster at high speed, gas is pushed and stripped from the galaxy, creating the long gaseous tail on one side . This is the same process that affects many galaxies in the dense Virgo Cluster environment .

2. Gravitational tidal interaction — NGC 4654 had a rapid close encounter with the massive neighboring galaxy NGC 4639 . This fly-by gravitational interaction distorted the galaxy's stellar and gas distribution, pulling material asymmetrically .

Critically, studies have shown that neither process alone can explain NGC 4654's full asymmetry — numerical simulations demonstrate that only a model combining both a tidal interaction and ram-pressure stripping reproduces the observed data .

Hubble observing programs and data being used

• The data used to construct the July 2026 image were collected as part of a Hubble observing program that investigates the star formation and stellar feedback cycle in nearby galaxies . This program uses Hubble's ultraviolet and optical capabilities to trace young stellar populations and ionized gas .
• Complementary multi-wavelength studies of NGC 4654 have used radio continuum and H I observations (e.g., from the VLA) and far-infrared/submillimeter data (e.g., from ALMA and Herschel) to map molecular gas, atomic hydrogen, and the compressed gas regions near the outer edge of the optical disk .
• A 2021 study in Astronomy & Astrophysics specifically analyzed NGC 4654 as a galaxy undergoing nearly edge-on ram-pressure stripping and a fly-by gravitational interaction, using these multi-wavelength data to examine gas compression and how it triggers star formation in the compressed regions .
• Additional Hubble Wide Field Planetary Camera 2 (WFPC2) and Advanced Camera for Surveys (ACS) archival data from the Hubble Legacy Archive have also been used in studies of this galaxy's star clusters and double stellar nucleus .

Together, these data allow researchers to connect the galaxy's asymmetric gas distribution and dynamics directly to the locations and rates of star formation — showing where gas compression from the two processes triggers new star birth and where gas stripping quenches it .