Hubble/Roman Galactic Bulge Survey Region (VISTA VVV Survey)

This near-infrared image from the ground-based VISTA VVV Survey shows the galactic bulge near Sagittarius A* (pronounced "A star"), the black hole at the Milky Way's center. The region, outlined in white, shows five stacked fields of view from NASA's Nancy Grace Roman Space Telescope that will be observed as part of its Galactic Bulge Time-Domain Survey, one of its three core community surveys. (Roman will also observe a sixth field at the galactic center that is not shown here.) Prior to Roman's launch, a team of researchers sought to use Hubble to capture the same regions in preparation for potential microlensing events.

These events cause the light from a more distant object to warp as a mass precisely aligns in front of that object. These masses, therefore, act like lenses, bending the light from objects behind them like background stars. In this case, the glow from the densely packed stars within the galactic bulge would be the distant light source. Having these Hubble observations allows us to capture the moments before these microlensing events happen, providing astronomers a way to clearly characterize objects (stars, planets, and even stellar-mass black holes) that cause microlensing by passing in front of stars within the galactic bulge.

The colored lines representing the Hubble survey area are stylized and represent a large number of individual pointings.