Hubble image shows several dozen boulders flung from Dimorphos

Boulders drifting from Dimorphos
Click for original image.

Using the Hubble Space Telescope, astronomers have photographed several dozen boulders that were flung off of the asteroid Dimorphos following the impact by the space probe DART. The picture to the right, reduced and brightened to more clearly show those boulders, was taken on December 19, 2022, four months after DART’s impact.

These are among the faintest objects Hubble has ever photographed inside the Solar System. The ejected boulders range in size from 1 meter to 6.7 meters across, based on Hubble photometry. They are drifting away from the asteroid at around a kilometre per hour.

The blue streak is the dust tail that has streamed off of Dimorphos since the impact, pushed away from the sun by the solar wind.

Hubble spots double tail of debris from DART impact of Dimorphus

Dimorphus double tail
Click for original image.

A series of images taken by the Hubble Space Telescope of the ejecta released when DART crashed into the small 525-foot-wide asteroid Dimorphus has found that debris forming a double tail trailing away from the Sun.

The picture to the right, cropped, reduced, and enhanced to post here, was taken on October 11, 2022 by Hubble, and shows those two tails as close parallel debris trails.

Repeated observations from Hubble over the last several weeks have allowed scientists to present a more complete picture of how the system’s debris cloud has evolved over time. The observations show that the ejected material, or “ejecta,” has expanded and faded in brightness as time went on after impact, largely as expected. The twin tail is an unexpected development, although similar behavior is commonly seen in comets and active asteroids. The Hubble observations provide the best-quality image of the double-tail to date.

Following impact, Hubble made 18 observations of the system. Imagery indicates the second tail formed between 2-8 October 2022.

Though observations by telescope will continue for the years to follow, the real punchline to this event will be when the European probe Hera rendezvouses with the Didymous-Dimorphus pair in 2026 to perform several years of very close observations.

DART’s impact shortened Dimorphus’s orbit around Didymos by 32 minutes

LICIACube Explorer image of DART impact
LICIACube Explorer image just after the DART
impact. Dimorphus is the blob near the top.

After two weeks of analyzing the orbit of Dimorphus around its parent asteroid Didymos, astronomers have determined that the impact of DART on Dimorphus shortened its orbit by 32 minutes.

Prior to DART’s impact, it took Dimorphos 11 hours and 55 minutes to orbit its larger parent asteroid, Didymos. Since DART’s intentional collision with Dimorphos on Sept. 26, astronomers have been using telescopes on Earth to measure how much that time has changed. Now, the investigation team has confirmed the spacecraft’s impact altered Dimorphos’ orbit around Didymos by 32 minutes, shortening the 11 hour and 55-minute orbit to 11 hours and 23 minutes. This measurement has a margin of uncertainty of approximately plus or minus 2 minutes.

Before its encounter, NASA had defined a minimum successful orbit period change of Dimorphos as change of 73 seconds or more. This early data show DART surpassed this minimum benchmark by more than 25 times.

It also appears the ejecta from the impact — much greater than expected — helped propel Dimorphus, a result that I think was also not expected.

Researchers are now shifting to studying the debris and asteroid itself, to better understand what happened as well as the nature of Dimorphus itself. This will also include a European probe dubbed Hera that will launch in 2024 an dvisit both asteroids in 2026.

Two days after DART’s impact of Dimorphus, ejected dust extends like a comet tail out more than 6,000 miles

Dust tail from Dimorphus two days after DART impact
Click for full image.

Using a telescope in Chile, astronomers photographed the ejecta two days after the impact of DART into the 525-foot-wide asteroid Dimorphus, and detected a tail of dust extending out more than 6,000 miles.

The picture to the right, cropped and reduced to post here, shows that tail.

In this new image, the dust trail — the ejecta that has been pushed away by the Sun’s radiation pressure, not unlike the tail of a comet — can be seen stretching from the center to the right-hand edge of the field of view. … At Didymos’s distance from Earth at the time of the observation, that would equate to at least 10,000 kilometers (6000 miles) from the point of impact.

Didymos is the larger parent asteroid that Dimorphus orbits.

It is still too soon to get the numbers on how Dimorphus’s path in space was changed by that impact. In fact, we still really don’t have a clear idea what is left of Dimophus itself. The ejecta cloud needs to clear somewhat to see what’s hidden inside it.

Hubble & Webb make first coordinated observations, tracking DART impact of Dimorphus

Webb and Hubble together look at DART impact of Dimorphus
Click for full image.

For the first time scientists have used both the Hubble Space Telescope and the James Webb Space Telescope to observe the same astronomical event, in this case the impact of the DART spacecraft on the asteroid Dimorphus on September 26, 2022.

The two images to the right show the asteroid several hours after impact. Both telescopes also captured images before the impact as well. From the press release:

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.

When Webb was first conceived in the late 1990s, it was exactly for this reason, to combine Hubble’s optical vision with Webb’s infrared view. Though more than a decade late, it has finally happened.

It will be months before scientists begin to decipher the data produced by all the telescopes and spacecraft used to observe the DART impact. What we are seeing now are merely hints at what has been learned.

First ground-based telescope view of DART impact on Dimorphus

LICIACube Explorer image of DART impact

We now have the first ground-based images of the DART impact on the 525-foot-wide asteroid Dimorphus yesterday, captured by the Hawaiian telescope ATLAS.

You need to watch the video of the full sequence of images, available here, to get a true sense of the impact. The cloud of material quickly expands to about twice the asteroid’s size, then dissipates away, with the remaining asteroid now appearing larger (?). That larger size could be caused by a remaining cloud of material that still needs to settle back to the surface.

More images have been released by a Chinese telescope. Also, the first images from the Italian cubesat LICIACube Explorer, flying in parallel with DART, have been released. I have posted one to the right. The large blob near the center is the parent half-mile-wide asteroid, Didymos. Dimorphus is buried in the debris cloud above and slightly to the right.

Hat tip stringer Jay for the links to these images.

DART hits Dimorphus

Didymos and Dimorphus


The surface of Dimorphus

The probe DART today successfully impacted the small 525-foot-wide asteroid Dimorphus. From the data produced engineers will calculate how much that impact changed Dimorphus’ orbit around it parent asteroid, half-mile-wide Didymos.

The three images to the right give a sense of the approach and impact.

The first, at 2 minutes and 30 seconds from impact, shows Didymos in the left bottom corner. You can actually see individual boulders on its surface. At this distance and resolution is is unclear whether it is a rubble pile or a more solid body. Dimorphus is no longer a mere dot, but no surface features can yet be discerned.

The second image, only seventeen seconds before DART crashed into Dimorphus, shows us the entire asteroid. Though it appears to be a pile of rocks, it also appears less of a rubble pile than both Ryugu and Bennu, visited by probes in 2019 and 2020. Those rubble-piles had almost no smooth surface areas. Dimorphus however at this distance and resolution does appear to have a lot of areas where the surface is relatively smooth, suggesting its structure is more solid than a rubble pile.

At only 525 feet across, some of those bigger boulders are about 50 to 60 feet in diameter.

The white dot in the center of Dimorphus marks the rocks seen in the third image, taken about five seconds before impact. At this resolution so close to the surface, it appears the smooth areas are actually made up of many tiny pebbles and dust.

The biggest rock in the center of the picture is probably between ten to twenty feet in diameter.

The primary data from this mission will not be available for a few weeks. Scientists have to observe both asteroids to see how much, if at all, Dimorphus’s orbit was shifted by the impact. Also, the images from the Italian cubesat, LICIACube Explorer, which was flying parallel to DART and taking pictures of the impact, plume, and back side of Dimorphus, won’t be available until later this week. Those images should give us a measure of the spacecraft’s effect on the asteroid. They will also reveal a lot more about the asteroid’s geology.