NASA’s DART spacecraft successfully slammed into a distant asteroid at hypersonic speed on Monday in the world’s first test of a planetary defense system, designed to prevent a potential doomsday meteorite collision with Earth.
Humanity’s first attempt to alter the motion of an asteroid or any celestial body played out in a NASA webcast from the mission operations center outside Washington, DC, 10 months after DART was launched.
The livestream showed images taken by DART’s camera as the cube-shaped “impactor” vehicle, no bigger than a vending machine with two rectangular solar arrays, streaked into the asteroid Dimorphos, about the size of a football stadium, at 7:14 pm EDT (23:14 GMT) some 6.8 million miles (11 million km) from Earth.
The $330 million (roughly Rs. 2,683 crore) mission, some seven years in development, was devised to determine if a spacecraft is capable of changing the trajectory of an asteroid through sheer kinetic force, nudging it off course just enough to keep Earth out of harm’s way.
Whether the experiment succeeded beyond accomplishing its intended impact will not be known until further ground-based telescope observations of the asteroid next month. But NASA officials hailed the immediate outcome of Monday’s test, saying the spacecraft achieved its purpose.
“NASA works for the benefit of humanity, so for us it’s the ultimate fulfillment of our mission to do something like this – a technology demonstration that, who knows, some day could save our home,” NASA Deputy Administrator Pam Melroy, a retired astronaut, said minutes after the impact.
DART, launched by a SpaceX rocket in November 2021, made most of its voyage under the guidance of NASA’s flight directors, with control handed over to an autonomous on-board navigation system in the final hours of the journey.
Monday evening’s bullseye impact was monitored in near real time from the mission operations center at the Johns Hopkins University Applied Physics Laboratory in Laurel, Maryland.
Cheers erupted from the control room as second-by-second images of the target asteroid, captured by DART’s onboard camera, grew larger and ultimately filled the TV screen of NASA’s live webcast just before the signal was lost, confirming the spacecraft had crashed into Dimorphos.
DART’s celestial target was an oblong asteroid “moonlet” about 560 feet (170 meters) in diameter that orbits a parent asteroid five times larger called Didymos as part of a binary pair with the same name, the Greek word for twin.
Neither object presents any actual threat to Earth, and NASA scientists said their DART test could not create a new hazard by mistake.
Dimorphos and Didymos are both tiny compared with the cataclysmic Chicxulub asteroid that struck Earth some 66 million years ago, wiping out about three-quarters of the world’s plant and animal species including the dinosaurs.
Smaller asteroids are far more common and present a greater theoretical concern in the near term, making the Didymos pair suitable test subjects for their size, according to NASA scientists and planetary defense experts. A Dimorphos-sized asteroid, while not capable of posing a planet-wide threat, could level a major city with a direct hit.
Also, the two asteroids’ relative proximity to Earth and dual configuration make them ideal for the first proof-of-concept mission of DART, short for Double Asteroid Redirection Test.
Robotic suicide mission
The mission represented a rare instance in which a NASA spacecraft had to crash to succeed. DART flew directly into Dimorphos at 15,000 miles per hour (24,000 kph), creating the force scientists hope will be enough to shift its orbital track closer to the parent asteroid.
APL engineers said the spacecraft was presumably smashed to bits and left a small impact crater in the boulder-strewn surface of the asteroid.
The DART team said it expects to shorten the orbital path of Dimorphos by 10 minutes but would consider at least 73 seconds a success, proving the exercise as a viable technique to deflect an asteroid on a collision course with Earth – if one were ever discovered.
A nudge to an asteroid millions of miles away years in advance could be sufficient to safely reroute it.
Earlier calculations of the starting location and orbital period of Dimorphos were made during a six-day observation period in July and will be compared with post-impact measurements made in October to determine whether the asteroid budged and by how much.
Monday’s test also was observed by a camera mounted on a briefcase-sized mini-spacecraft released from DART days in advance, as well as by ground-based observatories and the Hubble and Webb space telescopes, but images from those were not immediately available.
DART is the latest of several NASA missions in recent years to explore and interact with asteroids, primordial rocky remnants from the solar system’s formation more than 4.5 billion years ago.
Last year, NASA launched a probe on a voyage to the Trojan asteroid clusters orbiting near Jupiter, while the grab-and-go spacecraft OSIRIS-REx is on its way back to Earth with a sample collected in October 2020 from the asteroid Bennu.
The Dimorphos moonlet is one of the smallest astronomical objects to receive a permanent name and is one of 27,500 known near-Earth asteroids of all sizes tracked by NASA. Although none are known to pose a foreseeable hazard to humankind, NASA estimates that many more asteroids remain undetected in the near-Earth vicinity.
© Thomson Reuters 2022
How Satellites, Space Junk May Brighten Night Skies and Hinder Astronomy
Since time immemorial, humans around the world have gazed up in wonder at the night sky. The starry night sky has not only inspired countless works of music, art, and poetry but has also played an important role in timekeeping, navigation and agricultural practices in many traditions.
For many cultures, the night sky, with its stars, planets and the Milky Way, is considered just as important a part of the natural environment as the forests, lakes and mountains below. Countless people around the world gaze at the night sky: not only amateur and professional astronomers, but also casual observers who enjoy looking up at the stars to contemplate our place in the cosmos.
However, the night sky is changing. Not only is ground-based light pollution increasing rapidly, but growing numbers of satellites and space debris in orbit around Earth are also impacting the night sky.
Earlier research showed that satellites and space debris may increase the overall brightness of the night sky. In a new paper in Nature Astronomy, my colleagues and I applied this knowledge to predicting the performance of a major astronomical sky survey. We found this phenomenon may make the survey 7.5 percent less efficient and US$21.8 million (roughly Rs. 180 crore) more expensive.
A brighter sky
As a cultural astronomer, I am interested in the role of the night sky in cultural traditions around the world. In particular, I am interested in how light pollution and increasing satellite numbers affect different communities.
The number of satellites in orbit is growing rapidly. Since 2019, the number of functional satellites in orbit has more than doubled to around 7,600. The increase is mostly due to SpaceX and other companies launching large groups of satellites to provide high-speed internet communications around the world.
By the end of this decade, we estimate, there may be 100,000 satellites in orbit around the Earth. Collisions that generate space debris are more likely as space fills with new satellites. Other sources of debris include the intentional destruction of satellites in space warfare tests.
Increasing numbers of satellites and space debris reflect ever more sunlight towards the night side of Earth. This will almost certainly change the appearance of the night sky and make it harder for astronomers to do research.
One way satellites impact astronomy is by appearing as moving points of light, which show up as streaks across astronomers’ images. Another is by increasing diffuse night sky brightness. This means all the satellites that are too dim or small to be seen individually, as well as all the small bits of space debris, still reflect sunlight, and their collective effect is to make the night sky appear less dark.
Hard times for astronomers
In our research, we present the first published calculations of the aggregate effects of satellites and space debris in low-Earth orbit on major ground-based astronomy research facilities.
We looked at the effect on the planned large-scale survey of the night sky to be carried out at the Vera Rubin Observatory starting in 2024. We found that, by 2030, reflected light from objects in low-Earth orbit will likely increase the diffuse background brightness for this survey by at least 7.5 percent compared to an unpolluted sky.
This would diminish the efficiency of this survey by 7.5 percent as well. Over the ten-year lifetime of the survey, we estimate this would add some $21.8 million (roughly Rs. 180 crore) to the total project cost.
Brighter night skies mean longer exposures through telescopes are needed to see distant objects in the cosmos. This will mean that for projects with a fixed amount of observing time, less science will be accomplished, and there will be increased competition for telescope access.
In addition, brighter night skies will also reduce the detection limits of sky surveys, and dimmer objects may not be detected, resulting in missed research opportunities.
Some astrophysical events are rare and if researchers are unable to view them when they occur, there might not be an opportunity to easily see a given event again during a survey’s operational period. One example of faint objects is near-Earth objects – comets and asteroids in orbits close to Earth. Brighter night skies make it more likely such potentially hazardous objects may remain undetected.
A dramatic and unprecedented transformation
Increases in diffuse night sky brightness will also change how we see the night sky with the unaided eye. As the human eye cannot resolve individual small objects as well as a telescope can, an increase in satellites and space debris will create an even greater increase in the apparent brightness of the night sky. (When using a telescope or binoculars, one would be able to make out more of the dimmer satellites individually.) The projected increase in night sky brightness will make it increasingly difficult to see fainter stars and the Milky Way, both of which are important in various cultural traditions. Unlike “ground-based” light pollution (which tends to be the worst near large cities and heavily populated areas), the changes to the sky will be visible from essentially everywhere on Earth’s surface.
Our models give us a conservative lower limit for a likely increase in night sky brightness. If numbers of satellites and space debris continue to grow at the expected rate, the impacts will be even more pronounced.
As we note in our paper, “we are witnessing a dramatic, fundamental, and perhaps semi-permanent transformation of the night sky without historical precedent and with limited oversight”. Such a transformation will have profound consequences for professional astronomy as well as for anyone who wishes to view an unpolluted night sky.
New Event Horizon Telescope Collaboration to Create Videos of Black Holes
In 2019, the Event Horizon Telescope (EHT) collaboration produced the first-ever image of a black hole, stunning the world.
Now, scientists are taking it further. The next generation Event Horizon Telescope (ngEHT) collaboration aims to create high-quality videos of black holes.
But this next-generation collaboration is groundbreaking in other ways, too. It’s the first large physics collaboration bringing together perspectives from natural sciences, social sciences and the humanities.
For a virtual telescope spanning the planet, the larger a telescope, the better it is at seeing things that look tiny from far away. To produce black hole images, we need a telescope almost the size of Earth itself. That’s why the EHT uses many telescopes and telescope arrays scattered across the globe to form a single, virtual Earth-sized telescope. This is known as very long baseline interferometry.
Harvard astrophysicist Shep Doeleman, the founding director of the EHT, has likened this kind of astronomy to using a broken mirror. Imagine shattering a mirror and scattering the pieces across the world. Then you record the light caught by each of these pieces while keeping track of the timing, and collect those data in a supercomputer to virtually reconstruct an Earth-sized detector.
The 2019 first-ever image of a black hole was made by borrowing existing telescopes at six sites. Now, new telescopes at new sites are being built to better fill in the gaps of the broken mirror. The collaboration is currently in the process of selecting optimal places across the world, to increase the number of sites to approximately 20.
This ambitious endeavour needs over 300 experts organised into three technical working groups and eight science working groups. The history, philosophy and culture working group has just published a landmark report outlining how humanities and social science scholars can work with astrophysicists and engineers from the first stages of a project.
The report has four focus areas: collaborative knowledge formation, philosophical foundations, algorithms and visualisation, and responsible telescope siting.
How can we all collaborate? If you’ve ever tried to write a paper (or anything!) with someone else, you know how difficult it can be. Now imagine trying to write a scientific paper with over 300 people.
Should one expect each author to believe and be willing to defend every part of the paper and its conclusions? How should we all determine what will be included? If everyone has to agree with what is included, will this result in only publishing conservative, watered-down results? And how do you allow for individual creativity and boundary-pushing science (especially when you are attempting to be the first to capture something)? To resolve such questions, it’s important to balance collaborative approaches and structure everyone’s involvement in a way that promotes consensus, but also allows people to express dissent. Diversity of beliefs and practices among collaboration members can be beneficial to science.
How do we visualise the data? The aesthetic choices regarding the final black hole images and videos take place in a broader context of visual culture.
In reality, blue flames are hotter than flames appearing orange or yellow. But in the above false-colour image of Sagittarius A* – the black hole at the centre of the Milky Way – the colour palette of orange-red hues was chosen as it was believed orange would communicate to wider audiences just how hot the glowing material around the black hole is.
This approach connects to historical practices of technology-assisted scientific images, such as those by Galileo, Robert Hooke, and Johannes Hevelius. These scientists combined their early telescopic and microscopic images with artistic techniques so they would be legible to non-specialist audiences (particularly those who did not have access to the relevant instruments).
How philosophy can help Videos of black holes would be of significant interest to theoretical physicists. However, there is a bridge between formal mathematical theory and the messy world of experiment where idealised assumptions often do not hold up.
Philosophers can help to bridge this gap with considerations of epistemic risk – such as the risk of missing the truth, or making an error. Philosophy also helps to investigate the underlying assumptions physicists might have about a phenomenon.
For example, one approach to describing black holes is called the “no-hair theorem”. It’s the idea that an isolated black hole can be simplified down to just a few properties, and there’s nothing complex (hairy) about it. But the no-hair theorem applies to stable black holes. It relies on an assumption that black holes eventually settle down to a stationary state.
Responsible telescope siting The choice of locations for telescopes, or telescope siting, has historically been determined by technical and economic considerations – including weather, atmospheric clarity, accessibility and costs. There has been a historic lack of consideration for local communities, including First Nations peoples.
As the struggle at Mauna Kea in Hawai’i highlights, scientific collaborations are obligated to address ethical, social and environmental considerations when siting.
The ngEHT aims to advance responsible siting practices. It draws together experts in philosophy, history, sociology, community advocacy, science, and engineering to contribute to the decision-making process in ways that include cultural, social and environmental factors when choosing a new telescope location.
Overall, this collaboration is an exciting example of how ambitious plans demand innovative approaches – and how sciences are evolving in the 21st century.
US Air Force Hands Over NISAR Satellite to ISRO in Bengaluru
The US Air Force on Wednesday handed over NISAR, an earth observation satellite jointly developed by NASA and ISRO, to the Indian space agency. A US Air Force C-17 aircraft carrying the NASA-ISRO synthetic aperture radar (NISAR) has landed in Bengaluru, the US Consulate in Chennai said.
The satellite is an outcome of a collaboration between the American space agency NASA and Indian Space Research Organisation (ISRO).
“Touchdown in Bengaluru! @ISRO receives NISAR (@NASA-ISRO Synthetic Aperture Radar) on a @USAirforce C-17 from @NASAJPL in California, setting the stage for final integration of the Earth observation satellite, a true symbol of #USIndia civil space collaboration. #USIndiaTogether,” the US Consulate General, Chennai tweeted.
NISAR will be used by ISRO for a variety of purposes including agricultural mapping, and landslide-prone areas.
The satellite is expected to be launched in 2024 from Satish Dhawan Space Centre in Andhra Pradesh, into a near-polar orbit.
Meanwhile, ISRO also announced that it successfully carried out an “extremely challenging” controlled re-entry experiment of the decommissioned orbiting Megha-Tropiques-1 (MT-1) satellite. “The satellite re-entered the Earth’s atmosphere and would have disintegrated over the Pacific Ocean”, the Bengaluru-headquartered national space agency said on Twitter on Tuesday.
The final impact region estimated is in the deep Pacific Ocean within the expected latitude and longitude boundaries, an ISRO statement said.
The low Earth satellite was launched on October 12, 2011, as a joint satellite venture of ISRO and the French space agency, CNES for tropical weather and climate studies.
For details of the latest launches and news from Samsung, Xiaomi, Realme, OnePlus, Oppo and other companies at the Mobile World Congress in Barcelona, visit our MWC 2023 hub.
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