From The Space Science Telescope Institute
5.28.23
Claire Blome
cblome@stsci.edu,
Abigail Major
amajor@stsci.edu
When we spring forward, the institute also looks back to celebrate the year before. In 2023, staff took on new projects, reached significant milestones, and completed ongoing initiatives at the Space Telescope Science Institute. First up: Young stars. Staff who support the Hubble Space Telescope (HST) completed and released an ambitious three-year program known as ULLYSES to support the worldwide astronomy community’s collective research about star formation.
Colleagues who support the James Webb Space Telescope (JWST) watched as astronomers around the world made discoveries on all scales during its first year of science. The year included record-setting requests for observing time, and hundreds of new refereed papers based on JWST data. As the telescope’s Science Operations Center, STScI offers ongoing support to the astronomy community by frequently improving software and keeping the science community up to date with conferences and workshops.
Building an Ultraviolet Legacy
Hubble team members reflect on the completion of one of the telescope’s most ambitious observation programs and the impact it’s already having in astronomy.
Since June 2020, the Hubble Space Telescope has observed a representative sample of young stars—those recently formed and those still in the process—as part of its three-year ULLYSES (Ultraviolet Legacy Library of Young Stars as Essential Standards) program. Completed at the end of 2023, this large Hubble program has built a rich ultraviolet dataset that will support astronomers now and long into the future. Three members of the ULLYSES implementation team, Implementation Team Lead Julia Roman-Duval, Technical Implementation Lead Will Fischer, and Data Products Lead Jo Taylor, explain why this program is so critical for future astronomical research. [See the reports about/from these researchers.]
How does a program like ULLYSES, the largest Hubble program to date, take shape?
Hubble observed hundreds of still-forming and newly formed stars in two nearby low-metallicity dwarf galaxies (including the Large Magellanic Cloud, seen above) and within our own Milky Way galaxy for its comprehensive ULLYSES program. This dataset will have lasting importance, since Hubble is the only observatory currently capable of capturing high-resolution near-ultraviolet light.
Julia Roman-Duval: The program was initiated by STScI’s director at the time, Ken Sembach. By then, Hubble had completed several other large programs, including its Deep Fields and Frontier Fields. Sembach convened meetings with the science staff to discuss what would be good ideas for large programs. Looking at massive stars in the nearby universe to complement the gaps in our archive was suggested and brought to the Space Telescope Users Committee and the astronomical community. A working group was assembled with experts from outside the institute to assess the possibilities of a program focused on ultraviolet spectroscopy of young stars. The committee drafted an extensive report outlining its science goals and observing strategy. Once that report was finalized, the Hubble mission office started assembling a team to implement the program.
What are some of the big questions we have about young stars that ULLYSES data can help answer?
Roman-Duval: It’s important to emphasize that Hubble has delivered a legacy dataset of young stars in ultraviolet light. Ultraviolet light can only be observed from space, and Hubble is the only active telescope that can observe ultraviolet light in high resolution. This dataset is made up of spectra, which encode information about each star’s temperature, chemical composition, and rotation.
The first component of ULLYSES is the study of high-mass young stars. A big question we have about high-mass stars is: How do their winds evolve and change when their abundance of heavy elements decreases? These winds impact not only the immediate environment of the massive stars, but galaxies as a whole, for example by blowing gas and dust into their halos. A lot of diagnostics for stars’ winds are in ultraviolet light, and only Hubble can capture those spectra.
Will Fischer: The second component of the program is focused on low-mass stars that are still actively forming. These stars are about as massive as the Sun, down to about a quarter of the mass of the Sun. The mass of a star is its single most important characteristic—it determines how it’s going to evolve. These low-mass stars are surrounded by disks of gas and dust. They are pulling in mass from those disks, where planets may also be forming. With ULLYSES, we’re trying to learn how this process works. How does matter make its way from the disk onto the star and increase the star’s mass over time? How a star gathers mass also affects how fast the star rotates, which is important for the star’s evolution.
When matter from the disk crashes into the star, it releases a lot of ultraviolet and X-ray light. Right now, Hubble is the only telescope with high resolution ultraviolet spectrograph capabilities. It’s also giving us nearly simultaneous visible and near-infrared coverage. These combined observations are important because young low-mass stars pull in mass at rates that vary over short timescales.
With these extensive studies of young low- and high-mass stars, Hubble is helping us obtain a full picture of star formation in the nearby universe, where we can resolve individual stars. This will help astronomers understand star formation in the more distant universe, where individual stars cannot be resolved.
Why does ULLYSES include data from other missions?
MACS 0416 (Hubble ACS and WFC3 + Webb NIRCam Image)
This panchromatic view of galaxy cluster MACS0416 was created by combining infrared observations from NASA’s James Webb Space Telescope with visible-light data from NASA’s Hubble Space Telescope. To make the image, in general the shortest wavelengths of light were color-coded blue, the longest wavelengths red, and intermediate wavelengths green. The resulting wavelength coverage, from 0.4 to 5 microns, reveals a vivid landscape of galaxies that could be described as one of the most colorful views of the universe ever created.
MACS0416 is a galaxy cluster located about 4.3 billion light-years from Earth, meaning that light we see now left the cluster shortly after the formation of our solar system. This cluster magnifies the light from more distant background galaxies through gravitational lensing. As a result, the research team has been able to identify magnified supernovae and even very highly magnified individual stars.
Those colors give clues to galaxy distances: The bluest galaxies are relatively nearby and often show intense star formation, as best detected by Hubble, while the redder galaxies tend to be more distant, or else contain copious amount of dust, as detected by Webb. The image reveals a wealth of details that are only possible to capture by combining the power of both space telescopes.
In this image, blue represents data at wavelengths of 0.435 and 0.606 microns (Hubble filters F435W and F606W); cyan is 0.814, 0.9, and 1.05 microns (Hubble filters F814W, and F105W and Webb filter F090W); green is 1.15, 1.25, 1.4, 1.5, and 1.6 microns (Hubble filters F125W, F140W, and F160W, and Webb filters F115W and F150W); yellow is 2.00 and 2.77 microns (Webb filters F200W, and F277W); orange is 3.56 microns (Webb filter F356W); and red represents data at 4.1 and 4.44 microns (Webb filters F410M and F444W).
Image: NASA, ESA, CSA, STScI, Jose M. Diego (IFCA), Jordan C. J. D’Silva (UWA), Anton M. Koekemoer (STScI), Jake Summers (ASU), Rogier Windhorst (ASU), Haojing Yan (University of Missouri)
2023 marked the first year of a partnership between Hubble and Webb. The image above shows a pair of colliding galaxy clusters, and combines visible and infrared light—one of the most comprehensive views of the universe ever taken. In the future, Hubble and Webb will continue to work together to reveal the universe in unprecedented detail. Explore the image.
What do you think we’ll learn thanks to ULLYSES? How will the data be used?
Fischer: As a result of ULLYSES, I’m seeing a revitalization of work by people who study low-mass stars. My dissertation advisor earned her Ph.D. in 1980 and at the time there were maybe a dozen people around the world who cared about these stars. Now, we have ongoing meetings to discuss ULLYSES’ low-mass stars with five times as many people. Hubble’s program is already inspiring a younger generation of researchers and restarting scientific conversations.
Taylor: Everything is disseminated through our archive, the Mikulski Archive for Space Telescopes (MAST), which is a very big platform. We worked with our colleagues to create a search form for ULLYSES data. Having everything in one place allows people to easily retrieve data for these stars and enhances the legacy of the project.
Roman-Duval: The code behind our data products is open source. Users can tweak our parameters and make a product to their liking. It’s a great tool that goes beyond the ULLYSES data. It’s already been adapted and applied elsewhere.
Three years. Almost 1,000 orbits. Does a particular memory stick out to you during your time supporting the ULLYSES program?
Roman-Duval: Some of the community members told us, “Thank you so much for doing this, because it’s extremely helpful to us,” and shared the science they are doing. I find that extremely rewarding. Every time we go to the Space Telescope Users Committee or conferences, we get good feedback. I also think the first and last observations were memorable, and when we released some of the first targets. I think there were about 14 million views.
Taylor: Releasing time-series data for the four low-mass stars was a highlight for me. We took data over a two-week period, and then would go back a year later and take two more weeks of data. As you can imagine, a lot of data accumulated from that alone, but we eventually added other Hubble archival data. Now we have many years’ worth of spectra for four targets. Putting all of that together and looking at the plots, you can see how the stars change. It’s just incredible to see that variability visualized. It’s mesmerizing.
What’s next? The final ULLYSES dataset was released on December 12, 2023, and the team will continue to organize opportunities to engage with this comprehensive data collection collaboratively. In March 2024, the team will host a workshop at the Space Telescope Science Institute to celebrate the beginning of a new era for research about young stars.
The STScI 2023 Year in Review poster offers stats about our missions and divisions, gorgeous images and an illustration, and is foldable once printed.
When the Nancy Grace Roman Space Telescope is deployed into space in late 2026, it will begin a chapter of exciting science.
Read an immersive interview with three contributors who are helping to design Roman’s Science Operations Center software, including the planning and scheduling subsystem, the data management subsystem, and the project reference database.
As the excitement for the upcoming Habitable Worlds Observatory builds, staff in STScI’s Russell B. Makidon Optics Lab report on their progress about designs for an advanced coronagraph—and the challenges they must overcome to help make the new flagship mission’s goals possible.
Accessible astronomical data is also top of mind. Colleagues who support the Barbara A. Mikulski Archive for Space Telescopes (MAST) recognize that its tools often rely on Jupyter notebooks, which can be challenging to access and navigate for people with disabilities. That led staff to organize a well-rounded Day of Accessibility. This and other MAST initiatives are helping to lower barriers to embark on astronomical research.
In addition to publishing a variety of papers, many of our colleagues also began participating in a new mentorship program, which is designed to help employees carve out safe spaces for difficult conversations and give them freedom to excel.
Our annual report also covers our engineering staff’s fine tuning of data processing, the top HST and JWST 2023 news stories, and how we engaged the public with astronomical discoveries. Also check out this year’s poster, for more stats, and captivating images and an illustration.
See the full article here .
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We are the Space Telescope Science Institute in Baltimore, Maryland, operated by The Association of Universities for Research in Astronomy. We help humanity explore the universe with advanced space telescopes and ever-growing data archives.
Association of Universities for Research in Astronomy
Founded in 1982, we have helped guide the most famous observatory in history, the Hubble Space Telescope.
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