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Ten months after launch, NASA’s asteroid-deflecting DART spacecraft neared a planned impact with its target on Monday in a test of the world’s first planetary defense system, designed to prevent a doomsday collision with Earth.

The cube-shaped “impactor” vehicle, roughly the size of a vending machine with two rectangular solar arrays, was on course to fly into the asteroid Dimorphos, about as large as a football stadium, and self-destruct around 7pm EDT (4:30 IST) some 6.8 million miles (11 million km) from Earth.

The mission’s finale will test the ability of a spacecraft to alter an asteroid’s trajectory with sheer kinetic force, plowing into the object at high speed to nudge it astray just enough to keep our planet out of harm’s way.

It marks the world’s first attempt to change the motion of an asteroid, or any celestial body.

DART, launched by a SpaceX rocket in November 2021, has made most of its voyage under the guidance of NASA’s flight directors, with control to be handed over to an autonomous on-board navigation system in the final hours of the journey.

Monday evening’s planned impact is to be monitored in real time from the mission operations center at the Johns Hopkins University Applied Physics Laboratory (APL) in Laurel, Maryland.

DART’s celestial target is an asteroid “moonlet” about 560 feet (170 metres) 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 cannot create a new existential 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 pose 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.

Also, their relative proximity to Earth and dual-asteroid configuration make them ideal for the first proof-of-concept mission of DART, short for Double Asteroid Redirection Test.

Robotic mission suicide

The mission represents a rare instance in which a NASA spacecraft must ultimately crash to succeed.

The plan is for DART to fly directly into Dimorphos at 15,000 miles per hour (24,000 kph), bumping it hard enough to shift its orbital track closer to its larger companion asteroid.

Cameras on the impactor and on a briefcase-sized mini-spacecraft released from DART days in advance are designed to record the collision and send images back to Earth.

DART’s own camera is expected to return pictures at the rate of one image per second during its final approach, with those images streaming live on NASA TV starting an hour before impact, according to APL.

The DART team said it expects to shorten the orbital track 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 small nudge to an asteroid millions of miles away could be sufficient to safely reroute it away from the planet.

The test’s outcome will not be known until a new round of ground-based telescope observations of the two asteroids in October. Earlier calculations of the starting location and orbital period of Dimorphos were confirmed during a six-day observation period in July.

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.

NASA has put the entire cost of the DART project at $330 million (roughly Rs. 2,700 crore), well below that of many of the space agency’s most ambitious science missions.

© Thomson Reuters 2022


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A Nearby Supernova May End Dark Matter Search, Claims New Study

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A Nearby Supernova May End Dark Matter Search, Claims New Study

The pursuit of understanding dark matter, which comprises 85 percent of the universe’s mass, could take a significant leap forward with a nearby supernova. Researchers at the University of California, Berkeley, led by Associate Professor of Physics Benjamin Safdi, have theorised that the elusive particle known as the axion might be detected within moments of gamma rays being emitted from such an event. Axions, predicted to emerge during the collapse of a massive star’s core into a neutron star, could transform into gamma rays in the presence of intense magnetic fields, offering a potential breakthrough in physics.

Potential Role of Gamma-Ray Telescopes

The study was published in Physical Review Letters and revealed that the gamma rays produced from axions could confirm the particle’s mass and properties if detected. The Fermi Gamma-ray Space Telescope, currently the only gamma-ray observatory in orbit, would need to be pointed directly at the supernova, with the likelihood of this alignment estimated at only 10 percent. A detection would revolutionise dark matter research, while the absence of gamma rays would constrain the range of axion masses, rendering many existing dark matter experiments redundant.

Challenges in Catching the Event

For detection, the supernova must occur within the Milky Way or its satellite galaxies—an event averaging once every few decades. The last such occurrence, supernova 1987A, lacked sensitive enough gamma-ray equipment. Safdi emphasised the need for preparedness, proposing a constellation of satellites, named GALAXIS, to ensure 24/7 sky coverage.

Axion’s Theoretical Importance

The axion, supported by theories like quantum chromodynamics (QCD) and string theory, bridges gaps in physics, potentially linking gravity with quantum mechanics. Unlike neutrinos, axions could convert into photons in strong magnetic fields, providing unique signals. Laboratory experiments like ABRACADABRA and ALPHA are also probing for axions, but their sensitivity is limited compared to the scenario of a nearby supernova. Safdi expressed urgency, noting that missing such an event could delay axion detection by decades, underscoring the high stakes of this astrophysical endeavour.

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Fastest-Moving Stars in the Galaxy May be Piloted by Aliens, New Study Suggests

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Fastest-Moving Stars in the Galaxy May be Piloted by Aliens, New Study Suggests

Intelligent extraterrestrial civilisations might be utilising stars as massive interstellar vehicles to explore the galaxy, according to a theory proposed by Clement Vidal, a philosopher at Vrije Universiteit Brussel in Belgium. His research suggests that alien species could potentially accelerate their binary star systems to traverse vast cosmic distances. While such a concept is purely hypothetical and unproven, Vidal’s recent paper, which has not undergone peer review, raises intriguing possibilities about advanced extraterrestrial engineering.

Concept of Moving Star Systems

The study was published in the Journal of the British Interplanetary Society. As per a report by LiveScience, the idea revolves around the notion that alien civilisations, instead of building spacecraft for interstellar travel, might manipulate entire star systems to travel across the galaxy. Vidal highlights binary star systems, particularly those involving neutron stars and smaller companion stars, as ideal candidates. Neutron stars, due to their immense gravitational energy, could serve as anchors for devices designed to propel the system by selectively ejecting stellar material.

Vidal explained in the paper that uneven heating or manipulation of magnetic fields on a star’s surface could cause it to eject material in one direction. This process would create a reactionary thrust, propelling the binary system in the opposite direction. The concept provides a way to travel while preserving planetary ecosystems, making it a theoretically viable method for species reliant on their home systems.

Known Examples with High Velocities

Astronomers have identified hypervelocity stars, such as the pulsars PSR J0610-2100 and PSR J2043+1711, which exhibit high accelerations. While their movements are believed to be natural phenomena, Vidal suggests they could be worth further investigation to rule out potential artificial influences.

This theory adds an unconventional angle to the search for intelligent life, expanding possibilities beyond traditional methods of exploration like searching for signals or probes. The research underscores the importance of considering advanced and unconventional methods aliens might employ to navigate the galaxy.

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Hubble Telescope Finds Unexpectedly Hot Accretion Disk in FU Orionis

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Hubble Telescope Finds Unexpectedly Hot Accretion Disk in FU Orionis

NASA’s Hubble Space Telescope has provided new insights into the young star FU Orionis, located in the constellation Orion. Observations have uncovered extreme temperatures in the inner region of its accretion disk, challenging current models of stellar accretion. Using Hubble’s Cosmic Origins Spectrograph and Space Telescope Imaging Spectrograph, astronomers captured far-ultraviolet and near-ultraviolet spectra, revealing the disk’s inner edge to be unexpectedly hot, with temperatures reaching 16,000 kelvins—almost three times the Sun’s surface temperature.

A Star’s Bright Outburst Explained

First observed in 1936, FU Orionis became a hundred times brighter in months and has remained a unique object of study. Unlike typical T Tauri stars, its accretion disk touches the stellar surface due to instabilities. These are caused by the disk’s large mass, interactions with companion stars, or material falling inwards. Lynne Hillenbrand, a co-author from Caltech, in a statement said that the ultraviolet brightness seen exceeded predictions, revealing a highly dynamic interface between the star and its disk.

Implications for Planet Formation

As per a report by NASA, the study holds significant implications for planetary systems forming around such stars. The report further quoted Adolfo Carvalho, lead author of the study, saying that while distant planets in the disk may experience altered chemical compositions due to outbursts, planets forming close to the star could face disruption or destruction. This revised model provides critical insights into the survival of rocky planets in young star systems, he further added.

Future Investigations on FU Orionis

The research team continues to examine spectral emission lines in the collected data, aiming to map gas movement in the star’s inner regions. Hillenbrand noted that FU Orionis offers a unique opportunity to study the mechanisms at play in eruptive young stars. These findings, published in The Astrophysical Journal Letters, showcase the ongoing value of Hubble’s ultraviolet capabilities in advancing stellar science.

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