Webb’s Quest for Primeval Black Holes

The Webb team continues to work on commissioning the science instruments, the final step before starting science operations in the summer. We recently saw the beautiful image of the black hole in the center of our Milky Way galaxy, taken by the Event Horizon Telescope. One of the puzzles of modern astronomy is how every large galaxy came to have a giant central black hole, and how some of these black holes are surprisingly large even at very early times. We asked Roberto Maiolino, a member of the Near-Infrared Spectrometer (NIRSpec) instrument science team, to tell us how Webb will help to answer some of these questions.

“One of the most exciting areas of discovery that Webb is about to open is the search for primeval black holes in the early universe. These are the seeds of the much more massive black holes that astronomers have found in galactic nuclei. Most (probably all) galaxies host black holes at their centers, with masses ranging from millions to billions of times the mass of our Sun. These supermassive black holes have grown to be so large both by gobbling matter around them and also through the merging of smaller black holes.

“An intriguing recent finding has been the discovery of hyper-massive black holes, with masses of several billion solar masses, already in place when the universe was only about 700 million years old, a small fraction of its current age of 13.8 billion years. This is a puzzling result, as at such early epochs there is not enough time to grow such hyper-massive black holes, according to standard theories. Some scenarios have been proposed to solve this conundrum. One possibility is that black holes, resulting from the death of the very first generation of stars in the early universe, have accreted material at exceptionally high rates. Another scenario is that primeval, pristine gas clouds, not yet enriched by chemical elements heavier than helium, could directly collapse to form a black hole with a mass of a few hundred thousand solar masses, and subsequently accrete matter to evolve into the hyper-massive black holes observed at later epochs. Finally, dense, nuclear star clusters at the centers of baby galaxies may have produced intermediate mass black hole seeds, via stellar collisions or merging of stellar-mass black holes, and then become much more massive via accretion.

A chart showing the populations of known black holes (as large black dots) and the candidate black hole progenitors in the early universe (as shaded regions).
This illustration shows the populations of known black holes (large black dots) and the candidate black hole progenitors in the early universe (shaded regions). Credit: Roberto Maiolino, University of Cambridge.

“Webb is about to open a completely new discovery space in this area. It is possible that the first black hole seeds originally formed in the ‘baby universe,’ within just a few million years after the big bang. Webb is the perfect ‘time machine’ to learn about these primeval objects. Its exceptional sensitivity makes Webb capable of detecting extremely distant galaxies, and because of the time required for the light emitted by the galaxies to travel to us, we will see them as they were in the remote past.

“Webb’s NIRSpec instrument is particularly well suited to identify primeval black hole seeds. My colleagues in the NIRSpec Instrument Science Team and I will be searching for their signatures during ‘active’ phases, when they are voraciously gobbling matter and growing rapidly. In these phases the material surrounding them becomes extremely hot and luminous and ionizes the atoms in their surroundings and in their host galaxies. NIRSpec will disperse the light from these systems into spectra, or ‘rainbows.’ The rainbow of active black hole seeds will be characterised by specific ‘fingerprints,’ features of highly ionized atoms. NIRSpec will also measure the velocity of the gas orbiting in the vicinity of these primeval black holes. Smaller black holes will be characterized by lower orbital velocities. Black hole seeds formed in pristine clouds will be identified by the absence of features associated with any element heavier than helium.

“I look forward to using Webb’s unprecedented capabilities to search for these black hole progenitors, with the ultimate goal of understanding their nature and origin. The early universe and the realm of black holes seeds is a completely uncharted territory that my colleagues and I are very excited to explore with Webb.”

— Roberto Maiolino, professor of experimental astrophysics and director of the Kavli Institute for Cosmology, University of Cambridge


Jonathan Gardner, Webb deputy senior project scientist, NASA’s Goddard Space Flight Center

Stefanie Milam, Webb deputy project scientist for planetary science, NASA Goddard

Webb Nearly Set to Explore the Solar System

As NASA’s James Webb Space Telescope moves through the final phases of commissioning its science instruments, we have also begun working on technical operations of the observatory.  While the telescope moves through space, it will constantly find distant stars and galaxies and point at them with extreme precision to acquire images and spectra. However, we also plan to observe planets and their satellites, asteroids, and comets in our solar system, which move across the background stars of our galaxy. Webb needs to be able to lock on to these objects and track them with sufficient precision to obtain images and spectra. The Webb team recently completed the first test to track a moving object. The test verified that Webb could conduct moving target science! As we move forward through commissioning, we will test other objects moving at various speeds to verify we can study objects with Webb that move throughout the solar system.

Today, we asked Heidi Hammel, Webb interdisciplinary scientist for solar system observations, to tell us about her plans for studying Earth’s nearest neighbors:

“I am really excited about Webb’s upcoming first year of science operations! I lead a team of equally excited astronomers eager to begin downloading data. Webb can detect the faint light of the earliest galaxies, but my team will be observing much closer to home. They will use Webb to unravel some of the mysteries that abound in our own solar system.

“One of the questions I get asked frequently is why we need a powerful telescope like Webb to study our nearby solar system. We planetary scientists use telescopes to complement our in situ missions (missions that we send to fly by, orbit, or land on objects). One example of this is how Hubble was used to find the post-Pluto target for the New Horizons mission, Arrokoth. We also use telescopes when we don’t have in situ missions planned – like for the distant ice giants Uranus and Neptune or to make measurements of large populations of objects, such as hundreds of asteroids or Kuiper Belt Objects (small ice worlds beyond the orbits of Neptune, including Pluto), since we can only send missions to just a few of these.

“The Webb team has already used an asteroid within our solar system to run engineering tests of the ‘moving target’ (MT) capability. The engineering team tested this capability on a small asteroid in the Main Belt: 6481 Tenzing, named after Tenzing Norgay, the famous Tibetan mountain guide who was one of the first people to reach the summit of Mount Everest. Bryan Holler, at the Space Telescope Science Institute, had a choice of about 40 possible asteroids to test the MT tracking, but, as he told our team: “Since the objects were all virtually identical otherwise, picking the one with a name linked to success seemed like a no-brainer.”  We like that sort of thing.

Uranus shown within the field of view for MIRI spectroscopy. Keck image and data of Uranus courtesy L. Sromovsky, Leigh Fletcher.

“My role with Webb as an ‘Interdisciplinary Scientist’ means that my program uses all of the capabilities of this forefront telescope! We need all of them to truly understand the solar system (and the universe!).

“Our solar system has far more mysteries than my team had time to solve. Our programs will observe objects across the solar system: We will image the giant planets and Saturn’s rings; explore many Kuiper Belt Objects; analyze the atmosphere of Mars; execute detailed studies of Titan; and much more! There are also other teams planning observations; in its first year, 7% of Webb’s time will be focused on objects within our solar system.

“One exciting and challenging program we plan to do is observe ocean worlds. There’s evidence from the Hubble Space Telescope that Jupiter’s moon Europa has sporadic plumes of water-rich material. We plan to take high-resolution imagery of Europa to study its surface and search for plume activity and active geologic processes. If we locate a plume, we will use Webb’s spectroscopy to analyze the plume’s composition.

Simulated spectroscopy results from the plumes of Europa. This is an example of the data the Webb telescope could return that could identify the composition of subsurface ocean of this moon. Credit: NASA-GSFC/SVS, Hubble Space Telescope, Stefanie Milam, Geronimo Villanueva

“I have a soft spot in my heart for Uranus and Neptune. Indeed, it was the lack of a mission to these very distant worlds that got me involved in Webb so many decades ago. The Uranus team hopes to definitively link the chemistry and dynamics of the upper atmosphere (detectable with Webb) to the deeper atmosphere that we have been studying with other facilities over many decades. I’ve spent the past 30 years using the biggest and best telescopes humanity has ever built to study these ice giants, and we will now add Webb to that list.

“We have been planning for Webb observations for over twenty years, and that has gone into overdrive now that we are launched, deployed, and focused! I’ll note that nearly all of my team’s solar system data will be freely available to the broad planetary science community immediately. I made that choice to enable more science discoveries with Webb in future proposals.

“I am gratified to have been able to work with the team for all this time, and I especially want to give a shout out to the thousands of people who collectively have enabled this amazing facility for the astrophysics and planetary communities. Thank you! Ad astra!”

Heidi Hammel, vice president for science, Association of Universities for Research in Astronomy (AURA)


Stefanie Milam, Webb deputy project scientist for planetary science, NASA’s Goddard Space Flight Center

Jonathan Gardner, Webb deputy senior project scientist, NASA Goddard

Seventeen Modes to Discovery: Webb’s Final Commissioning Activities

With the telescope optics and instruments aligned, the Webb team is now commissioning the observatory’s four powerful science instruments. There are 17 different instrument “modes” to check out on our way to getting ready for the start of science this summer. Once we have approved all 17 of these modes, NASA’s James Webb Space Telescope will be ready to begin scientific operations!

In this post we’ll describe the 17 modes, and readers are encouraged to follow along as the Webb team checks them off one by one on the Where is Webb tracker. Each mode has a set of observations and analysis that need to be verified, and it is important to note that the team does not plan to complete them in the order listed below. Some of the modes won’t be verified until the very end of commissioning.

For each mode we have also selected a representative example science target that will be observed in the first year of Webb science. These are just examples; each mode will be used for many targets, and most of Webb’s science targets will be observed with more than one instrument and/or mode. The detailed list of peer-reviewed observations planned for the first year of science with Webb ranges from our solar system to the most distant galaxies.

1.  Near-Infrared Camera (NIRCam) imaging. Near-infrared imaging will take pictures in part of the visible to near-infrared light, 0.6 to 5.0 micrometers wavelength. This mode will be used for almost all aspects of Webb science, from deep fields to galaxies, star-forming regions to planets in our own solar system. An example target in a Webb cycle 1 program using this mode: the Hubble Ultra-Deep Field.

2.  NIRCam wide field slitless spectroscopy. Spectroscopy separates the detected light into individual colors. Slitless spectroscopy spreads out the light in the whole instrument field of view so we see the colors of every object visible in the field. Slitless spectroscopy in NIRCam was originally an engineering mode for use in aligning the telescope, but scientists realized that it could be used for science as well. Example target: distant quasars.

3.  NIRCam coronagraphy. When a star has exoplanets or dust disks in orbit around it, the brightness from a star usually will outshine the light that is reflected or emitted by the much fainter objects around it. Coronagraphy uses a black disk in the instrument to block out the starlight in order to detect the light from its planets. Example target: the gas giant exoplanet HIP 65426 b.

4.  NIRCam time series observations – imaging. Most astronomical objects change on timescales that are large compared to human lifetimes, but some things change fast enough for us to see them. Time series observations read out the instruments’ detectors rapidly to watch for those changes. Example target: a pulsing neutron star called a magnetar.

5.  NIRCam time series observations – grism. When an exoplanet crosses the disk of its host star, light from the star can pass through the atmosphere of the planet, allowing scientists to determine the constituents of the atmosphere with this spectroscopic technique. Scientists can also study light that is reflected or emitted from an exoplanet, when an exoplanet passes behind its host star. Example target: lava rain on the super-Earth-size exoplanet 55 Cancri e.

6.  Near-Infrared Spectrograph (NIRSpec) multi-object spectroscopy. Although slitless spectroscopy gets spectra of all the objects in the field of view, it also allows the spectra of multiple objects to overlap each other, and the background light reduces the sensitivity. NIRSpec has a microshutter device with a quarter of a million tiny controllable shutters. Opening a shutter where there is an interesting object and closing the shutters where there is not allows scientists to get clean spectra of up to 100 sources at once. Example target: the Extended Groth Strip deep field.

7.  NIRSpec fixed slit spectroscopy. In addition to the microshutter array, NIRSpec also has a few fixed slits that provide the ultimate sensitivity for spectroscopy on individual targets. Example target: detecting light from a gravitational-wave source known as a kilonova.

8.  NIRSpec integral field unit spectroscopy. Integral field unit spectroscopy produces a spectrum over every pixel in a small area, instead of a single point, for a total of 900 spatial/spectral elements. This mode gives the most complete data on an individual target. Example target: a distant galaxy boosted by gravitational lensing.

9.  NIRSpec bright object time series. NIRSpec can obtain a time series spectroscopic observation of transiting exoplanets and other objects that change rapidly with time. Example target: following a hot super-Earth-size exoplanet for a full orbit to map the planet’s temperature.

10.  Near-Infrared Imager and Slitless Spectrograph (NIRISS) single object slitless spectroscopy. To observe planets around some of the brightest nearby stars, NIRISS takes the star out of focus and spreads the light over lots of pixels to avoid saturating the detectors. Example target: small, potentially rocky exoplanets TRAPPIST-1b and 1c.

11.  NIRISS wide field slitless spectroscopy. NIRISS includes a slitless spectroscopy mode optimized for finding and studying distant galaxies. This mode will be especially valuable for discovery, finding things that we didn’t already know were there. Example target: pure parallel search for active star-forming galaxies.

12.  NIRISS aperture masking interferometry. NIRISS has a mask to block out the light from 11 of the 18 primary mirror segments in a process called aperture masking interferometry. This provides high-contrast imaging, where faint sources next to bright sources can be seen and resolved for images. Example target: a binary star with colliding stellar winds.

13.  NIRISS imaging. Because of the importance of near-infrared imaging, NIRISS has an imaging capability that functions as a backup to NIRCam imaging. Scientifically, this is used mainly while other instruments are simultaneously conducting another investigation, so that the observations image a larger total area. Example target: a Hubble Frontier Field gravitational lensing galaxy cluster.

14.  Mid-Infrared Instrument (MIRI) imaging. Just as near-infrared imaging with NIRCam will be used on almost all types of Webb targets, MIRI imaging will extend Webb’s pictures from 5 to 27 microns, the mid-infrared wavelengths. Mid-infrared imaging will show us, for example, the distributions of dust and cold gas in star-forming regions in our own Milky Way galaxy and in other galaxies. Example target: the nearby galaxy Messier 33.

15.  MIRI low-resolution spectroscopy. At wavelengths between 5 and 12 microns, MIRI’s low-resolution spectroscopy can study fainter sources than its medium-resolution spectroscopy. Low resolution is often used for studying the surface of objects, for example, to determine the composition. Example target: Pluto’s moon Charon.

16.  MIRI medium-resolution spectroscopy. MIRI can do integral field spectroscopy over its full mid-infrared wavelength range, 5 to 28.5 microns. This is where emission from molecules and dust display very strong spectral signatures. Example targets: molecules in planet-forming disks.

17.  MIRI coronagraphic imaging. MIRI has two types of coronagraphy: a spot that blocks light and three four-quadrant phase mask coronagraphs. These will be used to directly detect exoplanets and study dust disks around their host stars. Example target: searching for planets around our nearest neighbor star Alpha Centauri A.

— Jonathan Gardner, Webb deputy senior project scientist, NASA’s Goddard Space Flight Center

MIRI’s Sharper View Hints at New Possibilities for Science

Here, a close-up of the MIRI image is compared to a past image of the same target taken with NASA’s Spitzer Space Telescope’s Infrared Array Camera (at 8.0 microns). The MIRI version on the right shows stars and interstellar gas in sharp detail.
Credit: NASA/JPL-Caltech (left), NASA/ESA/CSA/STScI (right)

NASA’s James Webb Space Telescope is aligned across all four of its science instruments, as seen in a previous engineering image showing the observatory’s full field of view. Now, we take a closer look at that same image, focusing on Webb’s coldest instrument: the Mid-Infrared Instrument, or MIRI.

The MIRI test image (at 7.7 microns) shows part of the Large Magellanic Cloud. This small satellite galaxy of the Milky Way provided a dense star field to test Webb’s performance.

Here, a close-up of the MIRI image is compared to a past image of the same target taken with NASA’s Spitzer Space Telescope’s Infrared Array Camera (at 8.0 microns). The retired Spitzer telescope was one of NASA’s Great Observatories and the first to provide high-resolution images of the near- and mid-infrared universe. Webb, with its significantly larger primary mirror and improved detectors, will allow us to see the infrared sky with improved clarity, enabling even more discoveries.

Here, a close-up of the MIRI image is compared to a past image of the same target taken with NASA’s Spitzer Space Telescope’s Infrared Array Camera (at 8.0 microns). The MIRI version on the right shows stars and interstellar gas in sharp detail.
Credit: NASA/JPL-Caltech (top), NASA/ESA/CSA/STScI (bottom)

For example, Webb’s MIRI image shows the interstellar gas in unprecedented detail. Here, you can see the emission from “polycyclic aromatic hydrocarbons,” or molecules of carbon and hydrogen that play an important role in the thermal balance and chemistry of interstellar gas. When Webb is ready to begin science observations, studies such as these with MIRI will help give astronomers new insights into the birth of stars and protoplanetary systems.

 

Here, a close-up of the MIRI image is compared to a past image of the same target taken with NASA’s Spitzer Space Telescope’s Infrared Array Camera (at 8.0 microns). The MIRI image shows stars and interstellar gas in sharp detail.
Credit: NASA/ESA/CSA/STScI

In the meantime, the Webb team has begun the process of setting up and testing Webb’s instruments to begin science observations this summer. Today at 11 a.m., Webb experts will preview these next two months of instrument preparations in a teleconference for media. Listen to the audio stream live at nasa.gov/live.

Examining the Heart of Webb: The Final Phase of Commissioning

NASA’s James Webb Space Telescope is now experiencing all seasons – from hot to cold – as it undergoes the thermal stability test. Meanwhile, activities are underway for the final phase of commissioning: digging into the details of the science instruments, the heart of Webb. To complete commissioning, we will measure the detailed performance of the science instruments before we start routine science operations in the summer.

Today, the lead commissioning scientist for Webb, Scott Friedman of the Space Telescope Science Institute (STScI), gives us all the details on this final phase of commissioning.

“With the telescope beautifully aligned and the observatory near its final cryogenic temperature, we are ready to begin the last group of activities before the science observations start: science instrument commissioning. Here I describe just a few of those activities.

“The instruments, the Near-Infrared Camera (NIRCam), Near-Infrared Spectrometer (NIRSpec), Near-Infrared Imager and Slitless Spectrometer (NIRISS), Mid-Infrared Instrument (MIRI), and the Fine Guidance Sensor (FGS) have been powered up and safely cooled. We have operated their mechanisms and detectors, including filter wheels, grating wheels, and the NIRSpec microshutter assembly. The Webb optics team used images of isolated stars taken with each of the instruments to align the primary and secondary mirrors of the observatory. But we have more work to do before Webb is fully ready to embark on the ambitious science observations that will reveal the secrets of the universe.

“We will now begin an extensive suite of calibrations and characterizations of the instruments using a rich variety of astronomical sources. We will measure the instruments’ throughput – how much of the light that enters the telescope reaches the detectors and is recorded. There is always some loss with each reflection by the mirrors of the telescope and within each instrument, and no detector records every photon that arrives. We will measure this throughput at multiple wavelengths of light by observing standard stars whose light emission is known from data obtained with other observatories combined with theoretical calculations.

“The astrometric calibration of each instrument maps the pixels on the detectors to the precise locations on the sky, to correct the small but unavoidable optical distortions that are present in every optical system. We do this by observing the Webb astrometric field, a small patch of sky in a nearby galaxy, the Large Magellanic Cloud. This field was observed by the Hubble Space Telescope to establish the coordinates of about 200,000 stars to an accuracy of 1 milli-arcsec (less than 0.3 millionths of a degree). Calibrating this distortion is required to precisely place the science targets on the instruments’ field of view. For example, to get the spectra of a hundred galaxies simultaneously using the NIRSpec microshutter assembly, the telescope must be pointed so that each galaxy is in the proper shutter, and there are a quarter of a million shutters!

“We will also measure the sharpness of the stellar images, what astronomers call the ‘point spread function.’ We already know the telescope is delivering to the instruments image quality that exceeds our prelaunch expectations, but each instrument has additional optics. These optics perform a function, such as passing the light through filters to get color information about the astronomical target or using a diffraction grating to spread the incoming light into its constituent colors. Measuring the point spread function within each instrument at different wavelengths provides an important calibration for interpreting the data.

“We will test target acquisition for each instrument. For some observations, it is sufficient to point the telescope using the position of a guide star in the Fine Guidance Sensor and know the location of the science target relative to that guide star. This places the science target to an accuracy of a few tenths of an arcsecond. However, in some cases more precision is necessary, approximately a hundredth of an arcsecond. For example, for coronagraphy, the star has to be placed behind a mask so its light is blocked, allowing the nearby exoplanet to shine through. In time series observations, we measure how an exoplanet’s atmosphere absorbs the stellar light during the hours it takes to pass in front of its star, allowing us to measure the properties and constituents of the planet’s atmosphere. Both of these applications require that the instrument send corrections to the telescope pointing control system to put the science target precisely in the correct location within the instrument’s field of view.

“A final example of our instrument commissioning activities is observations of moving targets. Most astronomical objects are so far away that they appear to be stationary on the sky. However, this is not true of the planets, satellites and rings, asteroids, and comets within our own solar system. Observing these requires that the observatory change its pointing direction relative to the background guide stars during the observation. We will test this capability by observing asteroids of different apparent speeds using each instrument.

“We are now in the last two months of Webb’s commissioning before it is fully ready for its scientific mission. We still have important properties and capabilities of the instruments to test, measure, and demonstrate. When these are complete, we will be ready to begin the great science programs that astronomers and the public alike have been eagerly awaiting. We are almost there.”

– Scott Friedman, lead commissioning scientist for Webb, STScI


-Jonathan Gardner, Webb deputy senior project scientist, NASA Goddard

-Stefanie Milam, Webb deputy project scientist for planetary science, NASA Goddard

 

NASA’s Gregory Robinson Named Finalist for Service to America Medal

A headshot of Gregory L. Robinson
Credit: NASA

On May 1, the nonprofit, nonpartisan Partnership for Public Service announced the 2022 finalists for the Samuel J. Heyman Service to America Medal (Sammies) – an  awards program honoring excellence and innovation in federal service. Among the finalists is Gregory L. Robinson, program director for the James Webb Space Telescope at NASA Headquarters.

Selected from more than 400 nominations, Robinson has been named a Management Excellence finalist for his achievements in overseeing NASA’s largest and most complex international space science program, which will enable scientific breakthroughs in nearly every branch of astronomy.

“Greg Robinson is a leader who epitomizes excellence,” said Thomas Zurbuchen, NASA’s associate administrator for the Science Mission Directorate. “Across a massive international program of diverse teams and perspectives, he built the trust, consensus, and motivation to see this revolutionary mission to launch.”

Webb launched on Dec. 25, 2021, and endured a harrowing multi-week spacecraft commissioning period where hundreds of intricate parts synchronized to work successfully in the harsh environment of space while on its journey to its final orbit one million miles from Earth.

“I am very honored to be considered for a Service to America Medal,” Robinson said. “Working with an incredible, resilient team and partners across the globe to overcome many challenges has been a great privilege. I have enjoyed a great career at NASA for over 30 years, and to be a part of the mission’s historic moment when Webb launched flawlessly on Christmas Day was an awe-inspiring gift.”

Since its inception in 2002, the Sammies have honored more than 650 outstanding federal employees. Robinson is among 30 federal employees across 22 federal agencies honored as 2022 Sammies finalists for their outstanding contributions to safety, public health, and sustainability across our nation and the world.

Prior to leading Webb, Robinson served as the deputy associate administrator for programs in NASA’s Science Mission Directorate. He is a veteran executive, who previously served as deputy center director at NASA’s Glenn Research Center in Cleveland, NASA deputy chief engineer, and as the acting National Environmental Satellite, Data, and Information Service deputy assistant administrator at the National Oceanic and Atmospheric Administration.

Gregory L. Robinson holds a microphone and for an interview on NASA TV
Greg Robinson, program director for NASA’s James Webb Space Telescope Program at NASA Headquarters, gives a brief interview on NASA Television as he and the launch team monitor the countdown to Webb’s launch Dec. 25, 2021, at Europe’s Spaceport in Kourou, French Guiana. Webb is a large infrared telescope with a 21.3-foot (6.5-meter) primary mirror. The observatory will study every phase of cosmic history—from within our solar system to the most distant observable galaxies in the early universe. Credit: NASA/Bill Ingalls

Webb is the first space science telescope to use a large primary mirror that consists of 18 segments and an unparalleled optical system that recently showed the world its first focused image of a single star. Recently, the Webb team successfully aligned the telescope, confirming it can capture focused images with its four onboard science instruments. Now, it is undergoing the process of commissioning the instruments so it can deliver spectacular images and spectra this summer.

The observatory will enable the study of every phase of 13.5 billion years of cosmic history – from within our solar system to the most distant observable galaxies in the early universe – to everything in between.

More About the Sammies

More information about the program and the 2022 finalists is available online. All finalists are eligible for the Service to America Medals People’s Choice Award. Beginning Monday, May 2, members of the public may vote online for the federal employee they believe has made the most significant contribution to the American people. The People’s Choice winner will be announced in the summer.

More About the Webb Mission

The James Webb Space Telescope, the largest and most complex science observatory ever built, is an international program led by NASA with its partners, the European Space Agency and the Canadian Space Agency. As the scientific successor to the Hubble Space Telescope, Webb will explore the secrets of the universe and reveal new discoveries to help us understand our  place in the cosmos.

For more information about NASA’s Webb mission, visit https://www.nasa.gov/webb.

By Natasha R. Pinol, James Webb Space Telescope program communications lead at NASA Headquarters, Washington

The Hot and Cold of Webb

Completion of NASA’s James Webb Space Telescope’s optical alignment has moved us into the final phase of commissioning the Science Instruments. During this final phase the Webb team and instrument scientists will test all the modes and operations for the four science instruments to measure their performance, calibration, and overall observatory operations.

While the mirrors are slowly cooling to their final operating temperatures, the Webb team is preparing for the thermal stability test. We asked Erin Smith, the Webb deputy observatory project scientist, to tell us about the hot and cold of this test.

“Webb’s five-layer sunshield keeps the telescope and science instruments cool and shielded from the Sun, Earth and moon. This protection allows Webb to make measurements of the infrared universe, which requires a cold telescope and cold instrument optics. However, as Webb points to different targets around the sky, the angle of the Sun on the sunshade changes, which changes the thermal profile of the observatory. These variations in temperature can induce small changes in the observatory, and affect Webb’s optical quality, pointing, observed backgrounds, and other parameters.

“The thermal stability exercise will measure these changes by moving between the extremes of Webb’s field of view, from the hot to the cold attitude, spending multiple days in the cold attitude, then slewing back to the hot attitude. During this time, the Webb team will measure the thermal stability, pointing performance and optical wavefront drift. In addition to measuring the performance of the observatory, the team will also check the thermal modeling used to predict observatory behavior.

“With the telescope shielded from the Sun, Webb observes an annulus, or donut, on the sky at any given time, called the “field of regard”. Over the course of each year, this annulus sweeps out the whole sky. Pitch is the angle towards (negative) or away (positive) from the Sun. Webb points between pitches of -5 and +45 degrees. The “hot” attitude is at 0 degrees, with the Sun squarely illuminating the sunshield. The “cold” attitude is +45 degrees, with the sunlight reduced by a factor of cosine(45 degrees), about 0.7.


Top: Webb at the ‘hot’ attitude, pointed near the continuous viewing zone (CVZ); bottom: Webb at the ‘cold’ attitude.
Credit: NASA/STScI

“To begin the thermal stability test, the Webb team will point the observatory in the hot attitude at about 0 degrees pitch, and keep it there for a five days while it thermally stabilizes. The team will make baseline measurements of the pointing stability, optical wavefront error and any oscillations caused by the instrument electronics. Once this baseline has been established, the team will slew the observatory to the cold attitude, about +40 degrees pitch. Immediately after the slew, the team will use NIRCam’s suite of weak lenses for 24 hours to continuously measure any short-timescale effects on the wavefront. After this, the team will monitor the stability of the telescope every 12 hours, to measure the thermal stabilization of the telescope itself.

“The observatory will spend more than a week at the cold attitude, until the temperatures stabilize. Then Webb will slew back to the hot attitude, and the team will take high-cadence pointing stability data using both the FGS/NIRISS and NIRCam instruments. The MIRI instrument will also make observations at both attitudes, to understand how the changing thermal environment affects the mid-infrared background levels. During this long test, the Observatory will not sit idle; some instrument commissioning activities are compatible with the hot and cold pointings.

“When assembled together, the data from the thermal stability tests will allow the observatory team to better understand how the observatory behaves thermally. Although the changes are expected to be very small, Webb is so sensitive that they could make a difference as we optimize the telescope’s performance. This real-world calibration of the complicated thermal models used by Webb’s developers will help to inform future observing strategies and proposals.”

-Erin Smith, Webb deputy observatory project scientist, NASA Goddard


-Jonathan Gardner, Webb deputy senior project scientist, NASA Goddard

-Stefanie Milam, Webb deputy project scientist for planetary science, NASA Goddard

 

 

 

NASA’s Webb In Full Focus, Ready for Instrument Commissioning

This mosaic of five different star-packed images shows the field of view of NASA's James Webb Space Telescope as seen through its its four scientific instruments, and its Fine Guidance Sensor. All sensors are capturing images in full focus. For this test, Webb pointed at part of the Large Magellanic Cloud, a small satellite galaxy of the Milky Way, providing a dense field of hundreds of thousands of stars across all the observatory’s sensors. Each image shows a black field dotted with red-hued (colorized) stars. Webb’s three imaging instruments are NIRCam (images shown here at a wavelength of 2 microns), NIRISS (image shown here at 1.5 microns), and MIRI (shown at 7.7 microns, a longer wavelength revealing emission from interstellar clouds as well as starlight). MIRI's image contains bright stars with cloud like structures streaking across the frame. NIRSpec is a spectrograph rather than imager but can take images for calibrations and target acquisition. Dark regions visible in parts of the NIRSpec data are due to structures of its microshutter array, which has several hundred thousand controllable shutters that can be opened or shut to select which light is sent into the spectrograph. Webb’s Fine Guidance Sensor tracks guide stars to point the observatory accurately and precisely, its image set in the mosaic contains much brighter stars showing large 6-sided projections on the stars closest in the frame
Credit: NASA/STScI

Alignment of NASA’s James Webb Space Telescope is now complete. After full review, the observatory has been confirmed to be capable of capturing crisp, well-focused images with each of its four powerful onboard science instruments. Upon completing the seventh and final stage of telescope alignment, the team held a set of key decision meetings and unanimously agreed that Webb is ready to move forward into its next and final series of preparations, known as science instrument commissioning. This process will take about two months before scientific operations begin in the summer.

The alignment of the telescope across all of Webb’s instruments can be seen in a series of images that captures the observatory’s full field of view.

“These remarkable test images from a successfully aligned telescope demonstrate what people across countries and continents can achieve when there is a bold scientific vision to explore the universe,” said Lee Feinberg, Webb optical telescope element manager at NASA’s Goddard Space Flight Center.

The optical performance of the telescope continues to be better than the engineering team’s most optimistic predictions. Webb’s mirrors are now directing fully focused light collected from space down into each instrument, and each instrument is successfully capturing images with the light being delivered to them. The image quality delivered to all instruments is “diffraction-limited,” meaning that the fineness of detail that can be seen is as good as physically possible given the size of the telescope. From this point forward the only changes to the mirrors will be very small, periodic adjustments to the primary mirror segments.

“With the completion of telescope alignment and half a lifetime’s worth of effort, my role on the James Webb Space Telescope mission has come to an end,” said Scott Acton, Webb wavefront sensing and controls scientist, Ball Aerospace. “These images have profoundly changed the way I see the universe. We are surrounded by a symphony of creation; there are galaxies everywhere! It is my hope that everyone in the world can see them.”

This mosaic of five different star-packed images shows the field of view of NASA's James Webb Space Telescope as seen through its its four scientific instruments, and its Fine Guidance Sensor. All sensors are capturing images in full focus. For this test, Webb pointed at part of the Large Magellanic Cloud, a small satellite galaxy of the Milky Way, providing a dense field of hundreds of thousands of stars across all the observatory’s sensors. Each image shows a black field dotted with red-hued (colorized) stars. Webb’s three imaging instruments are NIRCam (images shown here at a wavelength of 2 microns), NIRISS (image shown here at 1.5 microns), and MIRI (shown at 7.7 microns, a longer wavelength revealing emission from interstellar clouds as well as starlight). MIRI's image contains bright stars with cloud like structures streaking across the frame. NIRSpec is a spectrograph rather than imager but can take images for calibrations and target acquisition. Dark regions visible in parts of the NIRSpec data are due to structures of its microshutter array, which has several hundred thousand controllable shutters that can be opened or shut to select which light is sent into the spectrograph. Webb’s Fine Guidance Sensor tracks guide stars to point the observatory accurately and precisely, its image set in the mosaic contains much brighter stars showing large 6-sided projections on the stars closest in the frame
Engineering images of sharply focused stars in the field of view of each instrument demonstrate that the telescope is fully aligned and in focus. For this test, Webb pointed at part of the Large Magellanic Cloud, a small satellite galaxy of the Milky Way, providing a dense field of hundreds of thousands of stars across all the observatory’s sensors. The sizes and positions of the images shown here depict the relative arrangement of each of Webb’s instruments in the telescope’s focal plane, each pointing at a slightly offset part of the sky relative to one another. Webb’s three imaging instruments are NIRCam (images shown here at a wavelength of 2 microns), NIRISS (image shown here at 1.5 microns), and MIRI (shown at 7.7 microns, a longer wavelength revealing emission from interstellar clouds as well as starlight). NIRSpec is a spectrograph rather than imager but can take images, such as the 1.1 micron image shown here, for calibrations and target acquisition. The dark regions visible in parts of the NIRSpec data are due to structures of its microshutter array, which has several hundred thousand controllable shutters that can be opened or shut to select which light is sent into the spectrograph. Lastly, Webb’s Fine Guidance Sensor tracks guide stars to point the observatory accurately and precisely; its two sensors are not generally used for scientific imaging but can take calibration images such as those shown here. This image data is used not just to assess image sharpness but also to precisely measure and calibrate subtle image distortions and alignments between sensors as part of Webb’s overall instrument calibration process. Credit: NASA/STScI

Now, the Webb team will turn its attention to science instrument commissioning. Each instrument is a highly sophisticated set of detectors equipped with unique lenses, masks, filters, and customized equipment that helps it perform the science it was designed to achieve. The specialized characteristics of these instruments will be configured and operated in various combinations during the instrument commissioning phase to fully confirm their readiness for science. With the formal conclusion of telescope alignment, key personnel involved with the commissioning of each instrument have arrived at the Mission Operations Center at the Space Telescope Science Institute in Baltimore, and some personnel involved with telescope alignment have concluded their duties.

Webb Telescope Completes Alignment Phase
Credit: NASA’s Goddard Space Flight Center

Though telescope alignment is complete, some telescope calibration activities remain: As part of scientific instrument commissioning, the telescope will be commanded to point to different areas in the sky where the total amount of solar radiation hitting the observatory will vary to confirm thermal stability when changing targets. Furthermore, ongoing maintenance observations every two days will monitor the mirror alignment and, when needed, apply corrections to keep the mirrors in their aligned locations.

By Thaddeus Cesari, NASA Goddard

Is Webb at Its Final Temperature?

The Mid-Infrared Instrument (MIRI) on NASA’s James Webb Space Telescope is now cooled by a gaseous helium cryocooler to under 7 kelvins. With the cooler in its final state, the Webb team is operating the MIRI instrument this week as part of seventh and final stage of the telescope alignment. When the instrument is operating, the detectors and electronics produce heat, which is balanced by the cryocooler to keep MIRI at a stable, and very cold, operating temperature. The near-infrared instruments also warm up during operations and have to dissipate heat, although for these instruments this is done with passive cooling; the heat from the detectors and electronics is radiated into deep space.

Now that the instruments are at their operating temperatures, the telescope mirrors will also continue cooling down to their final temperatures, but they are not quite there yet. The primary mirror segments and the secondary mirror are made of beryllium (coated with gold). At cryogenic temperatures, beryllium has a long thermal time constant, which means that it takes a long time to cool or to heat up. The primary mirror segments are still cooling, very slowly.

The secondary mirror, hanging out on the end of its support structure a long way from any heat sources, is the coldest mirror, currently at 29.4 kelvins. The 18 primary mirror segments range in temperature from 34.4 kelvins to 54.5 kelvins. An advantage of beryllium mirrors is that they don’t change shape with temperature the way glass mirrors would at these temperatures, so the temperature range does not affect the telescope alignment process.

Currently, four of the 18 mirror segments are above 50 kelvins: at 52.6, 54.2, 54.4, and 54.5. These four mirror segments emit some mid-infrared light that reaches the MIRI detectors. Since all the mirror temperatures are now below 55 kelvins, it is expected that MIRI will be sensitive enough to perform its planned science, but any additional cooling of these mirrors will only enhance its performance. The Webb team hopes to see the mirrors cool by an additional 0.5 to 2 kelvins.

When we point the telescope at an astronomical target, the telescope and sunshield move together. The angle that the sunshield presents to the Sun is called the pointing “attitude.” The tiny amount of residual heat that makes its way through the five-layer sunshield to the primary mirror depends on this attitude, and since the mirror segment temperatures change very slowly, their temperatures depend on the attitude averaged over multiple days.

During commissioning, Webb is currently spending most of its time pointed at the ecliptic poles, which is a comparatively hot attitude. During science operations, starting this summer, the telescope will have a much more even distribution of pointings over the sky. The average thermal input to the warmest mirror segments is expected to go down a bit, and the mirrors will cool a bit more.

Later in commissioning, we plan to test the thermal dependence of the mirrors on the attitude. We will point Webb at a hot attitude for several days, and point Webb at a cold attitude for several days, in a process called the thermal slew. This will inform us how long it takes for the mirrors to cool down or heat up when the observatory is at these positions for any given amount of time.

Is Webb at its final temperature? The answer is: almost!


–Jonathan Gardner, Webb deputy senior project scientist, NASA’s Goddard Space Flight Center

Webb Will Study Formation, Composition, Clouds of Distant Worlds

The journey of commissioning the Webb telescope continues this week with the successful cooling of the Mid-InfraRed Instrument (MIRI), through the critical ‘pinch point,’ down to its final operating temperature of less than 7 kelvins (-447 degrees Fahrenheit, or -266 degrees Celsius). This was a precondition to completing the seventh and final stage of the mirror alignment process.  The next steps include initial check-outs of MIRI and continue on to the final stages of multi-instrument, multi-field alignment with all four science instruments.

Last week we shared the cool science on star and planet formation planned for Webb. Today, we get into details on how Webb will study planets around other stars, which are known as extrasolar planets, or exoplanets. Knicole Colón, Webb’s deputy project scientist for exoplanet science, takes us into the discovery space of exploring new worlds beyond our solar system. Dr. Colón brings a unique perspective as she is also the project scientist for the Transiting Exoplanet Survey Satellite (TESS), a mission that has found many exoplanet targets that Webb will observe.

“Over the last 30 years, astronomers have discovered over 5,000 extrasolar planets. These discoveries have revealed that exoplanets span a vast range of masses, sizes, and temperatures and orbit all types of stars, leading to extraordinarily diverse worlds.

“With its powerful spectroscopic and imaging capabilities across a wide infrared wavelength range, Webb is poised to revolutionize our knowledge of the composition of these worlds and of planet-forming disks. From small, potentially rocky exoplanets up to giant, gaseous ones, Webb will observe these worlds with the transit technique. Direct imaging techniques will be used to study young, giant exoplanets along with the environments in which planets form and evolve around stars, known as protoplanetary disks and debris disks.

“One specific exoplanet observation that will be done with Webb involves collecting observations over the course of a planet’s orbit to enable measurements of the atmospheric composition and dynamics. I am involved in a program to observe the gas giant HD 80606 b as part of Webb’s first year of observations. Because the orbit of HD 80606 b is extremely eccentric (non-circular) and long (111 days), the amount of energy received by the planet from its star ranges from approximately 1 to 950 times what Earth receives from the Sun! This results in extreme temperature variations, which are predicted to cause clouds to rapidly form and dissipate in the planet’s atmosphere on very short timescales. Our science team will probe these predicted cloud dynamics in real-time over the course of a continuous ~18 hour observation of HD 80606 b as it passes behind its star, using the NIRSpec instrument on Webb to measure thermal light from the planet’s atmosphere.

Caption: The orbital configuration of HD 80606 b is shown along with expected temperature variations as viewed from Earth and Webb at several orbital phases. The planned “start” and “end” of the ~18 hour stretch of Webb observations are indicated (credit: adapted from de Wit et al. 2016; courtesy of James Sikora).

“Beyond gas giants, a number of Webb’s exoplanet targets in its first year of observations are small and orbit stars that are smaller and cooler than the Sun, known as M dwarfs. While exoplanet discovery began around 30 years ago, many of these small exoplanets around M dwarfs were just discovered in the last few years by surveys like TESS. Webb observations will start to reveal the diversity of atmospheres that exist on these small planets by searching for evidence of molecules like water, carbon dioxide, and methane in their atmospheres. Because M dwarfs are typically much more active than the Sun and have energetic stellar flares that could potentially strip the atmospheres off of these planets, Webb observations may even reveal that some of these small planets have no atmosphere at all.

Caption: This artist’s illustration shows three small planets discovered by TESS around an M dwarf star called L 98-59. Planets c and d are just 1.4 and 1.6 times larger than Earth and will be observed in Webb’s first year of science (credit: NASA’s Goddard Space Flight Center).

“With TESS and other surveys continuing to discover additional planets in our galaxy at a regular pace and Webb preparing to study the atmospheres of many of these newly discovered worlds, our exoplanet adventures are in many ways just beginning.”

Knicole Colón, Webb’s deputy project scientist for exoplanet science, NASA’s Goddard Space Flight Center


Stefanie Milam, Webb deputy project scientist for planetary science, NASA Goddard

Jonathan Gardner, Webb deputy senior project scientist, NASA Goddard