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Euclid calling: downloading the Universe
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By NASA
Rebekah Hounsell is an assistant research scientist working on ways to optimize and build infrastructure for future observations made by the Nancy Grace Roman Space Telescope. The mission will shed light on many astrophysics topics, like dark energy, which are currently shrouded in mystery. Rebekah also works as a support scientist for the TESS (Transiting Exoplanet Survey Satellite) mission, helping scientists access and analyze data.
Name: Rebekah Hounsell
Title: Assistant Research Scientist
Formal Job Classification: Support Scientist for the TESS mission and Co-Principal Investigator of the Roman Supernova Project Infrastructure Team (PIT)
Organization: Code 667.0
Rebekah Hounsell knew she wanted to study space from a very young age. Now, she’s a scientist at NASA’s Goddard Space Flight Center in Greenbelt, Md. NASA/Chris Gunn What do you do and what is most interesting about your role at Goddard?
I am fortunate to have several roles at Goddard. I am a support scientist for TESS. Here I aid the community in accessing and analyzing TESS data. I am a co-principal investigator of a Roman project infrastructure team, focusing on building infrastructure to support supernova cosmology with the Roman HLTDS (High Latitude Time-Domain Survey). In addition, I am part of the Physics of the Cosmos program analysis group executive committee, co-chairing both the Cosmic Structure Science interest group and the Time-Domain and Multi-Messenger Astrophysics Science interest group. In these roles I have been fortunate enough to get a glimpse into how missions such as TESS and Roman work and how we can make them a success for the community. Missions like TESS are paving the way for future wide area surveys like Roman, providing a plethora of high cadence transient and variable star data, which can be used to gain a better understanding of our universe and our place within it.
How will your current work influence the Nancy Grace Roman Space Telescope’s future observations?
The Roman team I am leading is tasked with developing a pixels-to-cosmology pipeline for the analysis of supernova data from the HLTDS. What this means is that we will develop tools to aid the community in obtaining supernova lightcurves and prism spectra, which are precise enough to be used in testing various cosmological modes. We are also working to develop tools which will allow the community to test various HLTDS designs, adjusting cadence, filters, exposure times, etc., to best optimize its output for their science.
What got you interested in astrophysics? What was your path to your current role?
When I was a child I lived in a very rural area in England, with little to no light pollution. I had a wonderful view of the night sky and was fascinated by stars. I remember when I found out that the universe was expanding and my first thought was “into what?” I think it was that which fueled my curiosity about space and pushed me into astrophysics. At about 10 years old, I decided astrophysics was the path for me, and after that I really started to focus on physics and math at school.
At 18, 19 I went to Liverpool University/Liverpool John Moores and completed my master’s in astrophysics in 2008. I then went on to obtain my Ph.D., focusing on classical and recurrent novae. In 2012 I received my first postdoc at STScI (the Space Telescope Science Institute in Baltimore). It was at STScI that I learned about how the instruments operating on Hubble worked and figured out that what I really loved doing was working on data and improving it. At the time however, I wasn’t ready to leave academia altogether, so I took another postdoc at the University of Illinois Champaign Urbana/UC Santa Cruz. It was here that I first started working on Roman, only back then it was known as WFIRST. I was a member of a Supernova Science Investigation Team for WFIRST and worked to optimize the design of what was then known as the SN survey, later to become the HLTDS. During this time I published a paper that created some of the most realistic simulations of the survey, including various statistical and systematic effects. After this I headed to the University of Pennsylvania to work on core collapse supernovae from the Dark Energy Survey. This was an exciting data set, but again I realized what I really liked doing was working on data from or for a mission. As such I took my current job at NASA.
Rebekah stands by a model of NASA’s upcoming Nancy Grace Roman Space Telescope. The observatory’s deployable aperture cover, or sun shade, is visible in the background in the largest clean room at Goddard.NASA/David Friedlander What are you most looking forward to exploring through Roman’s eyes?
Given the nature of the mission, Roman is going to discover a plethora of transient events. Some of these will be extremely rare and if caught in one of Roman’s high cadenced, deep fields, the data obtained will be able to shed new light on the physics driving these phenomena. I am also excited about these data being used with those from other observatories including the Vera C. Rubin Observatory and NASA’s James Webb Space Telescope.
What has surprised you the most about the universe as you’ve learned more about it?
We are still discovering so many new things which shed new light on the universe, its evolution, and our place in it. In recent years we have learned about kilonovae, gravitational waves, and we’ve discovered various diverse supernovae. There are so many extreme and complex events that we are still trying to understand, and I suspect that Roman will reveal even more.
What is your favorite thing about working for NASA?
There is no one path to working at NASA. I have met so many people who entered into the field following completely different paths than myself. I love this. We all have something different to bring to the table and those differences are what makes NASA what it is today.
A portrait of Rebekah in front of the NASA meatball.NASA/David Friedlander What hobbies fill your time outside of work?
I like to paint and draw. I also enjoy looking after animals. I also love participating in outreach events. When I lived in Philly I helped to set up the Astronomy on Tap branch there. I think it is important to talk about what we do and why it is needed.
What advice do you have for others who are interested in working in astronomy?
There is no one path. Don’t think you have to complete x, y, z steps and then you make it. That is not true. Do what you are passionate about, what you enjoy to learn about. And most importantly ask questions! Learn about what others are doing in the field, how they got there, and figure out what works for you.
By Ashley Balzer
NASA’s Goddard Space Flight Center, Greenbelt, Md.
Conversations With Goddard is a collection of Q&A profiles highlighting the breadth and depth of NASA’s Goddard Space Flight Center’s talented and diverse workforce. The Conversations have been published twice a month on average since May 2011. Read past editions on Goddard’s “Our People” webpage.
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Last Updated Jul 16, 2024 ContactAshley Balzerashley.m.balzer@nasa.govLocationGoddard Space Flight Center Related Terms
People of NASA Careers Goddard Space Flight Center Nancy Grace Roman Space Telescope People of Goddard Women at NASA Explore More
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By European Space Agency
Video: 00:06:08 ESA’s Euclid space mission has released five unprecedented new views of the Universe. These never-before-seen images demonstrate Euclid’s remarkable ability to unravel the secrets of the cosmos. Scientists are now equipped to hunt for rogue planets, study mysterious matter through lensed galaxies, and explore the evolution of the Universe. Join us as we explore these groundbreaking discoveries and what they mean for the future of space exploration.
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By European Space Agency
A newly devised procedure to de-ice Euclid's optics has performed significantly better than hoped. Light coming in to the visible ‘VIS’ instrument from distant stars was gradually decreasing due small amounts of water ice building up on its optics. Mission teams spent months devising a procedure to heat up individual mirrors in the instrument’s complex optical system, without interfering with the finely tuned mission’s calibration or potentially causing further contamination. After the very first mirror was warmed by just 34 degrees, Euclid's sight was restored.
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By European Space Agency
A few layers of water ice – the width of a strand of DNA – are starting to impact Euclid’s vision; a common issue for spacecraft in the freezing cold of space, but a potential problem for this highly sensitive mission that requires remarkable precision to investigate the nature of the dark Universe. After months of research, Euclid teams across Europe are now testing a newly designed procedure to de-ice the mission's optics. If successful, the operations will validate the mission teams’ plan to keep Euclid’s optical system as ice-free as possible for the rest of its life in orbit.
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By NASA
6 min read
NASA’s Webb, Hubble Telescopes Affirm Universe’s Expansion Rate, Puzzle Persists
When you are trying to solve one of the biggest conundrums in cosmology, you should triple check your homework. The puzzle, called the “Hubble Tension,” is that the current rate of the expansion of the universe is faster than what astronomers expect it to be, based on the universe’s initial conditions and our present understanding of the universe’s evolution.
Scientists using NASA’s Hubble Space Telescope and many other telescopes consistently find a number that does not match predictions based on observations from ESA’s (European Space Agency’s) Planck mission. Does resolving this discrepancy require new physics? Or is it a result of measurement errors between the two different methods used to determine the rate of expansion of space?
This image of NGC 5468, a galaxy located about 130 million light-years from Earth, combines data from the Hubble and James Webb space telescopes. This is the farthest galaxy in which Hubble has identified Cepheid variable stars. These are important milepost markers for measuring the expansion rate of the universe. The distance calculated from Cepheids has been cross-correlated with a type Ia supernova in the galaxy. Type Ia supernovae are so bright they are used to measure cosmic distances far beyond the range of the Cepheids, extending measurements of the universe’s expansion rate deeper into space.
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Hubble has been measuring the current rate of the universe’s expansion for 30 years, and astronomers want to eliminate any lingering doubt about its accuracy. Now, Hubble and NASA’s James Webb Space Telescope have tag-teamed to produce definitive measurements, furthering the case that something else – not measurement errors – is influencing the expansion rate.
“With measurement errors negated, what remains is the real and exciting possibility we have misunderstood the universe,” said Adam Riess, a physicist at Johns Hopkins University in Baltimore. Riess holds a Nobel Prize for co-discovering the fact that the universe’s expansion is accelerating, due to a mysterious phenomenon now called “dark energy.”
As a crosscheck, an initial Webb observation in 2023 confirmed that Hubble measurements of the expanding universe were accurate. However, hoping to relieve the Hubble Tension, some scientists speculated that unseen errors in the measurement may grow and become visible as we look deeper into the universe. In particular, stellar crowding could affect brightness measurements of more distant stars in a systematic way.
The SH0ES (Supernova H0 for the Equation of State of Dark Energy) team, led by Riess, obtained additional observations with Webb of objects that are critical cosmic milepost markers, known as Cepheid variable stars, which now can be correlated with the Hubble data.
“We’ve now spanned the whole range of what Hubble observed, and we can rule out a measurement error as the cause of the Hubble Tension with very high confidence,” Riess said.
The team’s first few Webb observations in 2023 were successful in showing Hubble was on the right track in firmly establishing the fidelity of the first rungs of the so-called cosmic distance ladder.
Astronomers use various methods to measure relative distances in the universe, depending upon the object being observed. Collectively these techniques are known as the cosmic distance ladder – each rung or measurement technique relies upon the previous step for calibration.
But some astronomers suggested that, moving outward along the “second rung,” the cosmic distance ladder might get shaky if the Cepheid measurements become less accurate with distance. Such inaccuracies could occur because the light of a Cepheid could blend with that of an adjacent star – an effect that could become more pronounced with distance as stars crowd together and become harder to distinguish from one another.
The observational challenge is that past Hubble images of these more distant Cepheid variables look more huddled and overlapping with neighboring stars at ever farther distances between us and their host galaxies, requiring careful accounting for this effect. Intervening dust further complicates the certainty of the measurements in visible light. Webb slices though the dust and naturally isolates the Cepheids from neighboring stars because its vision is sharper than Hubble’s at infrared wavelengths.
At the center of these side-by-side images is a special class of star used as a milepost marker for measuring the universe’s rate of expansion – a Cepheid variable star. The two images are very pixelated because they are a very zoomed-in view of a distant galaxy. Each of the pixels represents one or more stars. The image from the James Webb Space Telescope is significantly sharper at near-infrared wavelengths than Hubble (which is primarily a visible-ultraviolet light telescope). By reducing the clutter with Webb’s crisper vision, the Cepheid stands out more clearly, eliminating any potential confusion. Webb was used to look at a sample of Cepheids and confirmed the accuracy of the previous Hubble observations that are fundamental to precisely measuring the universe’s expansion rate and age. NASA, ESA, CSA, STScI, Adam G. Riess (JHU, STScI)
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“Combining Webb and Hubble gives us the best of both worlds. We find that the Hubble measurements remain reliable as we climb farther along the cosmic distance ladder,” said Riess.
The new Webb observations include five host galaxies of eight Type Ia supernovae containing a total of 1,000 Cepheids, and reach out to the farthest galaxy where Cepheids have been well measured – NGC 5468 – at a distance of 130 million light-years. “This spans the full range where we made measurements with Hubble. So, we’ve gone to the end of the second rung of the cosmic distance ladder,” said co-author Gagandeep Anand of the Space Telescope Science Institute in Baltimore, which operates the Webb and Hubble telescopes for NASA.
Hubble and Webb’s further confirmation of the Hubble Tension sets up other observatories to possibly settle the mystery. NASA’s upcoming Nancy Grace Roman Space Telescope will do wide celestial surveys to study the influence of dark energy, the mysterious energy that is causing the expansion of the universe to accelerate. ESA’s Euclid observatory, with NASA contributions, is pursuing a similar task.
At present it’s as though the distance ladder observed by Hubble and Webb has firmly set an anchor point on one shoreline of a river, and the afterglow of the big bang observed by Planck’s measurement from the beginning of the universe is set firmly on the other side. How the universe’s expansion was changing in the billions of years between these two endpoints has yet to be directly observed. “We need to find out if we are missing something on how to connect the beginning of the universe and the present day,” said Riess.
These finding were published in the February 6, 2024 issue of The Astrophysical Journal Letters.
The Hubble Space Telescope has been operating for over 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. NASA’s Goddard Space Flight Center in Greenbelt, Maryland, manages the telescope. Goddard also conducts mission operations with Lockheed Martin Space in Denver, Colorado. The Space Telescope Science Institute (STScI) in Baltimore, Maryland, conducts Hubble and Webb science operations for NASA.
The James Webb Space Telescope is the world’s premier space science observatory. Webb is solving mysteries in our solar system, looking beyond to distant worlds around other stars, and probing the mysterious structures and origins of our universe and our place in it. Webb is an international program led by NASA with its partners, ESA (European Space Agency) and the Canadian Space Agency.
More Webb News: https://science.nasa.gov/mission/webb/latestnews/
More Hubble News: https://science.nasa.gov/mission/hubble/hubble-news/
More Webb Images: https://science.nasa.gov/mission/webb/multimedia/images/
More Hubble Images: https://science.nasa.gov/mission/hubble/multimedia/hubble-images/
Webb Mission Page: https://science.nasa.gov/mission/webb/
Hubble Mission Page: https://science.nasa.gov/mission/hubble/
Learn More
Hubble Reaches New Milestone in Mystery of Universe’s Expansion Rate
Mystery of the Universe’s Expansion Rate Widens With New Hubble Data
NASA’s Hubble Extends Stellar Tape Measure 10 Times Farther Into Space
Discovering the Runaway Universe
Media Contacts:
Claire Andreoli – claire.andreoli@nasa.gov
Laura Betz – laura.e.betz@nasa.gov
NASA’s Goddard Space Flight Center, Greenbelt, MD
Ray Villard, Christine Pulliam
Space Telescope Science Institute, Baltimore, MD
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Last Updated Mar 11, 2024 Editor Andrea Gianopoulos Location Goddard Space Flight Center Related Terms
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