A sweeping barred spiral galaxy marks the spot in this image, but the real treasure is the gravitational lens in the lower-right corner, where a distant background galaxy is being magnified and distorted by the gravity of a closer galaxy.

This observation is one of many gravitational lensing images taken by NASA’s Hubble Space Telescope in preparation for science with the new Nancy Grace Roman Space Telescope.

Gravitational lensing occurs when the mass of a foreground object – such as a galaxy – warps spacetime, causing light to bend, distort, and magnify as it passes around the object, similar to a giant lens in space. Lenses like this occur when a precise chance alignment takes place between the foreground and background galaxies, causing light from the background galaxy to curve around the foreground galaxy.

In this image, the gravitational lens features a foreground elliptical galaxy that is about 4.5 billion light-years away. That means the light we see from this galaxy now would have first started traveling toward us when our solar system was still forming. The background galaxy is about eight billion light-years away, almost twice as far. It appears as a pair of arcs, one large and very noticeable to the upper left of the foreground galaxy, the other a much smaller, flipped image of the same background galaxy to the lower right. This configuration is called an arc-counterarc pair.

The more massive the foreground galaxy is, the stronger the gravitational lens and the more significantly it bends light. By studying the distortion of the background galaxy, researchers can determine how much mass the foreground galaxy contains. This plays a huge role in the study of dark matter, the mysterious, invisible substance that makes up the majority of mass in the universe. The visible matter is not enough to account for the level of distortion in the background galaxy, which allows researchers to calculate both the mass of the foreground galaxy and how much dark matter it contains.

Almost all of the objects in this image are galaxies, except for a few scattered foreground stars. The barred spiral galaxy in this image – so called because its arms extend from a bar of stars in its center – is about the size of our own Milky Way galaxy, which astronomers think is a barred spiral as well. The tiny spiral to the left of the large spiral may be a satellite galaxy, similar to the Large and Small Magellanic Clouds that orbit the Milky Way.

Hubble views the cosmos primarily in visible and ultraviolet light with some infrared coverage, and Roman sees mainly infrared wavelengths and some visible light. Hubble can provide high-resolution views of individual objects, while Roman has a much larger field of view conducive to panoramas.

Images like this offer a glimpse of how Hubble and Roman will work together to build an even more comprehensive picture of the cosmos. This is just one of many gravitational lens images captured by Hubble. Astronomers will use them to analyze gravitational distortions to learn more about dark matter in the foreground galaxies and to lay the groundwork for future Roman observations.

Hubble can only view these gravitational lenses one at a time, while Roman’s wide view of the sky will provide a greater sample of these lenses. Astronomers are using Hubble’s sharp images to build a computer model to better analyze dark matter-induced distortions. This tool will help astronomers analyze Roman’s large images. Hubble will also follow up on interesting lenses Roman detects.

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Media Contact:

Claire Andreoli
NASA’s Goddard Space Flight Center, Greenbelt, MD
claire.andreoli@nasa.gov

This NASA Hubble Space Telescope image features the edge-on, intermediate spiral galaxy NGC 1827, located roughly 37 million light-years away in the constellation Columba, the Dove. Hubble captured the image as part of a survey looking at 260 satellite galaxies around 22 Milky Way-like host galaxies within a radius of about 32 million light-years from Earth. Hubble has already observed 111 of these satellite galaxies. The remaining galaxies will take an additional 149 Hubble orbits, one orbit for each galaxy, to observe.

The image, taken with Hubble’s Advanced Camera for Surveys, reveals bright-blue regions along the galaxy’s disk dotted with dark dust lanes where new stars are likely forming. A bright foreground star appears just to the left of the galaxy’s bright central bulge but is located between us and the galaxy. Its four diffraction spikes are the result of light bending around the internal supports that hold Hubble’s secondary mirror.

Low-mass galaxies like the ones in this Hubble observing program provide a way to test the predictions of cosmological models on small scales, which struggle to match observations. The data Hubble gathers will help us better understand and characterize the properties of low-mass galaxies in Milky Way-like systems, allowing researchers to refine cosmological models.

Media Contact:

Claire Andreoli
NASA’s Goddard Space Flight Center, Greenbelt, MD
claire.andreoli@nasa.gov

Diligent sleuthing by astronomers has broken open a cold case in the data archive of NASA’s Hubble Space Telescope. In a study published Monday in Nature Astronomy, researchers report uncovering a surprising chemical clue that indicates the white dwarf star HS 0209+0832 may host a second-generation planet. 

A white dwarf is the remnant core of a low-mass star that has burned through all its nuclear fuel and lost its outer envelope of gas and dust to space. A second-generation planet is a world that forms around the stellar remnant from its cast-off material. 

“Rather than the white dwarf stage being a kind of epilogue to the story of a star and its planets, this research points to the systems we are familiar with only being the first chapter of a potentially much longer tale, with some new characters showing up. That’s a really exciting prospect to pursue,” said Jamie Williams, astronomer and lead author, a doctoral candidate at the University of Warwick in the United Kingdom.

Earth and the other planets in our solar system are first-generation planets, which form from material left over from a star’s birth. 

“What Hubble is showing us in this white dwarf system is something we haven’t seen before: a high abundance of the element niobium, the signature of which I was unfamiliar with when I first found it in the archival data,” Williams said.

When Hubble first observed the star in 1999, the data contained roughly 100 chemical features that could not be identified. Williams went back to those records armed with an updated chemical database and found that niobium matched many of the mystery features.

Williams explained that, while niobium is found in our solar system and has multiple uses on Earth, including in jewelry and medical imaging devices, the amount Hubble found in the HS 0209+0832 system points to a planet forming not from a star’s birth, but from the material ejected as it dies. 

“Niobium and other elements heavier than iron are astronomically special because, unlike many common elements, they are not formed in the cores of stars by thermonuclear fusion,” said Nicholas Stone, a theoretical astrophysicist at the University of Wisconsin – Madison and member of the research team. “Instead, these heavy elements can only be synthesized in the exotic conditions that briefly emerge inside dying stars. The presence of niobium is a signpost of these ‘death’ throes, and the expulsion of the dying star’s innards into space.” 

Once the star ejected this chemically enriched material, the team theorizes that some of it coalesced into a gas giant planet. The remainder of the ejecta dispersed long ago, but the planet remains.

“When Jamie asked me about niobium in relation to this study I was truly gobsmacked, as that element had not been reported in any other white dwarf analyzed to date. Once we realized it was there, everything fell into place,” said astronomer and study co-author Boris Gaensicke, also at the University of Warwick.

The research team confirmed the Hubble observations with data from NASA’s retired FUSE (Far Ultraviolet Spectroscopic Explorer) mission, which also showed strong signatures of niobium in the HS 0209+0832 system. 

NASA’s TESS (Transiting Exoplanet Survey Satellite) also observed the white dwarf for four months, allowing it to detect periodic brightness variations that indicate that a planet orbits at a distance of about 3.7 million miles (6 million kilometers), much closer than Mercury orbits the Sun. 

The research team estimates the candidate planet is a gas giant about the size of Jupiter that is rapidly losing atmosphere. Because the white dwarf star is relatively new, it is still very hot and likely blasting this planet with energy that is stripping its outer material. This could result in the planet having a comet-like tail of material that would form a disk around the white dwarf star and fall back on to its surface, leading to Hubble detecting the niobium when studying the star. Despite this mass loss, Williams said that the planet is likely not a temporary blip on the cosmic radar. 

“If the second-generation planet is there, I think it is likely to survive. Eventually the white dwarf will cool and then maintain a consistent temperature, with the planet in its stable habitable zone for millions of years,” Williams said.

Williams added that there is still a lot of work to do to understand these types of systems — how second-generation planets form, how common or rare they are, and how they evolve in orbit around a “dead” star. He’ll use Hubble to explore these questions for the next several years, hoping to build up substantial data and statistics about these new types of celestial bodies.

“I think this research is an important example of the fact that scientific discovery is not a straight path,” Gaensicke said. “It often needs that magical moment when people discuss big questions on their minds and realize that together they can find unexpected answers.”

The Hubble Space Telescope has been operating for more than three decades and continues to make ground-breaking discoveries that shape our fundamental understanding of the universe. Hubble is a project of international cooperation between NASA and ESA (European Space Agency). NASA’s Goddard Space Flight Center in Greenbelt, Maryland, manages the telescope and mission operations. Lockheed Martin Space also supports mission operations at Goddard. The Space Telescope Science Institute in Baltimore, which is operated by the Association of Universities for Research in Astronomy, conducts Hubble science operations for NASA.