Two of NASA’s Great
Observatories, the James Webb Space Telescope and the Hubble Space Telescope,
have captured views of a unique NASA experiment designed to intentionally smash
a spacecraft into a small asteroid in the world’s first-ever in-space test for
planetary defense. These observations of NASA’s Double Asteroid Redirection
Test (DART) impact mark the first time that Webb and Hubble simultaneously
observed the same celestial target.
On Sept. 26, 2022, at 7:14 pm EDT, DART intentionally
crashed into Dimorphos, the
asteroid moonlet in the double-asteroid system of Didymos. It was the world’s
first test of the kinetic impact mitigation technique, using a spacecraft to
deflect an asteroid that poses no threat to Earth, and modifying the object’s
orbit. DART is a test for defending Earth against potential asteroid or comet
hazards.
The coordinated Hubble and Webb
observations are more than just an operational milestone for each telescope –
there are also key science questions relating to the makeup and history of our
solar system that researchers can explore when combining the capabilities of
these observatories.
“Webb and Hubble show what we’ve always
known to be true at NASA: We learn more when we work together,” said NASA
Administrator Bill Nelson. “For the first time, Webb and Hubble have
simultaneously captured imagery from the same target in the cosmos: an asteroid
that was impacted by a spacecraft after a seven-million-mile journey. All of
humanity eagerly awaits the discoveries to come from Webb, Hubble, and our
ground-based telescopes – about the DART mission and beyond.”
Observations from Webb and Hubble together
will allow scientists to gain knowledge about the nature of the surface of
Dimorphos, how much material was ejected by the collision, and how fast it was
ejected. Additionally, Webb and Hubble captured the impact in different
wavelengths of light – Webb in infrared and Hubble in visible. Observing the
impact across a wide array of wavelengths will reveal the distribution of particle
sizes in the expanding dust cloud, helping to determine whether it threw off
lots of big chunks or mostly fine dust. Combining this information, along with
ground-based telescope observations, will help scientists to understand how
effectively a kinetic impact can modify an asteroid’s orbit.
This animated GIF combines three of the images NASA’s Hubble Space
Telescope captured after NASA’s Double Asteroid Redirection Test (DART)
intentionally impacted Dimorphos, a moonlet asteroid in the double asteroid
system of Didymos. The animation spans from 22 minutes after impact to 8.2
hours after the collision took place. As a result of the impact, the brightness
of the Didymos-Dimorphos system increased by 3 times. The brightness also
appears to hold fairly steady, even eight hours after impact. Credits:
Science: NASA, ESA, Jian-Yang Li (PSI); animation: Alyssa Pagan (STScI) Download
full-resolution, uncompressed versions and supporting visuals from the Space
Telescope Science Institute
Webb Captures Impact Site Before and After Collision
Webb took one observation of the impact location before the collision took
place, then several observations over the next few hours. Images from
Webb’s Near-Infrared Camera
(NIRCam) show a tight, compact core, with plumes of
material appearing as wisps streaming away from the center of where the impact
took place.
Observing the impact with Webb presented the flight operations, planning,
and science teams with unique challenges, because of the asteroid’s speed of
travel across the sky. As DART approached its target, the teams performed
additional work in the weeks leading up to the impact to enable and test a
method of tracking asteroids moving over three times faster than the original speed
limit set for Webb.
“I have nothing but tremendous admiration for the Webb Mission Operations
folks that made this a reality,” said principal investigator Cristina Thomas of
Northern Arizona University in Flagstaff, Arizona. “We have been planning these
observations for years, then in detail for weeks, and I’m tremendously happy
this has come to fruition.”
Scientists also plan to observe the asteroid system in the coming months
using Webb’s Mid-Infrared
Instrument (MIRI) and Webb’s Near-Infrared
Spectrograph (NIRSpec). Spectroscopic data will provide
researchers with insight into the asteroid’s chemical composition.
Webb observed the impact over five hours total and captured 10 images. The
data was collected as part of Webb’s Cycle 1 Guaranteed Time
Observation Program 1245 led by Heidi Hammel of the
Association of Universities for Research in Astronomy (AURA).
This animation, a timelapse of images from NASA’s James Webb Space Telescope, covers the time spanning just before impact at 7:14 p.m. EDT, Sept. 26, through 5 hours post-impact. Plumes of material from a compact core appear as wisps streaming away from where the impact took place. An area of rapid, extreme brightening is also visible in the animation. Credits: Science: NASA, ESA, CSA, Cristina Thomas (Northern Arizona University), Ian Wong (NASA-GSFC); Joseph DePasquale (STScI) Download full-resolution, uncompressed versions and supporting visuals from the Space Telescope Science Institute
Hubble Images Show Movement of Ejecta After Impact
Hubble also captured observations of the binary system ahead of the impact,
then again 15 minutes after DART hit the surface of Dimorphos. Images from
Hubble’s Wide Field Camera 3 show the impact in visible light. Ejecta from the
impact appear as rays stretching out from the body of the asteroid. The bolder,
fanned-out spike of ejecta to the left of the asteroid is in the general
direction from which DART approached.
Some of the rays appear to be curved slightly, but astronomers need to take a closer look to determine what this could mean. In the Hubble images, astronomers estimate that the brightness of the system increased by three times after impact, and saw that brightness hold steady, even eight hours after impact.
These images from NASA’s Hubble Space Telescope, taken (left to right) 22
minutes, 5 hours, and 8.2 hours after NASA’s Double Asteroid Redirection Test
(DART) intentionally impacted Dimorphos, show expanding plumes of ejecta from
the asteroid’s body. The Hubble images show ejecta from the impact that appear
as rays stretching out from the body of the asteroid. The bolder, fanned-out
spike of ejecta to the left of the asteroid is in the general direction from
which DART approached. These observations, when combined with data from NASA’s
James Webb Space Telescope, will allow scientists to gain knowledge about the
nature of the surface of Dimorphos, how much material was ejected by the
collision, how fast it was ejected, and the distribution of particle sizes in
the expanding dust cloud. Credits: Science: NASA, ESA, Jian-Yang Li
(PSI); image processing: Alyssa Pagan (STScI) Download
full-resolution, uncompressed versions and supporting visuals from the Space
Telescope Science Institute
Hubble plans to monitor the Didymos-Dimorphos system 10 more times over the
next three weeks. These regular, relatively long-term observations as the
ejecta cloud expands and fades over time will paint a more complete picture of
the cloud’s expansion from the ejection to its disappearance.
“When I saw the data, I was literally speechless, stunned by the amazing
detail of the ejecta that Hubble captured,” said Jian-Yang Li of the Planetary
Science Institute in Tucson, Arizona, who led the Hubble observations. “I feel
lucky to witness this moment and be part of the team that made this happen.”
Hubble captured 45 images in the time immediately before and following
DART’s impact with Dimorphos. The Hubble data was collected as part of Cycle 29 General
Observers Program 16674.
“This is an unprecedented view of an unprecedented event,” summarized Andy
Rivkin, DART investigation team lead of the Johns Hopkins University Applied
Physics Laboratory in Laurel, Maryland.
The James Webb Space Telescope is the world's premier space science
observatory. Webb will solve mysteries in our solar system, look beyond to
distant worlds around other stars, and probe 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 CSA (Canadian
Space Agency).
The Hubble Space Telescope is a project of international cooperation
between NASA and ESA. NASA's Goddard Space Flight Center in Greenbelt,
Maryland, manages the telescope. The Space Telescope Science Institute (STScI)
in Baltimore, Maryland, conducts Hubble and Webb science operations. STScI is
operated for NASA by the Association of Universities for Research in Astronomy,
in Washington, D.C.
Banner image: These images, Hubble on the left and Webb on the right, show observations of the Didymos-Dimorphos system several hours after NASA’s Double Asteroid Redirection Test (DART) intentionally impacted the moonlet asteroid. Credits: Science: NASA, ESA, CSA, Jian-Yang Li (PSI), Cristina Thomas (Northern Arizona University), Ian Wong (NASA-GSFC); image processing: Joseph DePasquale (STScI), Alyssa Pagan (STScI) Download full-resolution, uncompressed versions and supporting visuals from the Space Telescope Science Institute
Source: Webb, Hubble Capture Detailed Views of DART Impact | NASA
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