Space Sunday: collisions, gamma bursts and rockets

A Hubble Space Telescope image from Oct. 8 shows the debris blasted from the surface of an asteroid called Dimorphos 12 days after it was struck by NASA’s DART spacecraft. Credit: NASA / ESA / STScI / Hubble

The results are now in – to a degree – on the success of NASA’s Double Asteroid Redirect Test (DART) mission which has been the focus of my two previous Space Sunday updates.

An attempt to test the theory that a vehicle launched from Earth could successful divert the orbit of a near-Earth obit (NEO) threatening this planet with a collision simply through the kinetic force imparted through crashing into it, DART struck Dimorphos, a 160-m asteroid orbiting the much larger Didymos as both orbit the Sun every 2.11 years crossing and re-crossing Earth’s orbit.

As I’ve previously noted, Dimorphos was selected as a target as scientist know a lot about its orbits – it shares a stable solar orbit with Didymos, it had a near-circular equatorial orbit around Didymos once every 11.9 hours, allowing DART to strike it pretty much head-on, thus transferring all of its 22,530 km/h velocity into a force to counter Dimorphos’ own velocity and 5 million tonnes of mass.

Prior to the impact, the DART team indicated any change in Dimorphos’ orbit of Didymos of 73 seconds or more would be considered a success – although it would likely take a couple of weeks after the impact before the exact change in the asteroid’s orbit would be known, as detailed Earth-based observations would be required.

It turns out that DART didn’t affect the orbit of Dimorphos by seconds – by a whopping 32 minutes, altering it from 11 hours and 55 minutes to 11 hours and 23 minutes and also reducing the average distance between Dimorphos and Didymos. This strongly suggests such a mission, undertaken a the right time, could be an effective means of diverting an Earth-threatening asteroid. However, the team note further observations are required.

This result is one important step toward understanding the full effect of DART’s impact with its target asteroid. As new data come in each day, astronomers will be able to better assess whether, and how, a mission like DART could be used in the future to help protect Earth from a collision with an asteroid if we ever discover one headed our way.

– Lori Glaze, director of NASA’s Planetary Science Division.

One of the reasons DART may have had a much greater impact (no pun intended) on Dimorphos and give pause for further consideration is that while much was known about its orbit around Didymos, little was known about its composition. Post-impact, the images captured by the Hubble and James Webb space telescopes and Earth-based observatories suggest Dimorphos is essentially a ball of loosely packed gravel, dust and ice. Thus, DART’s impact was amplified by the jet of ejecta throw off of the asteroid. As such, it is unclear as to whether the impact would have had the same effect against a more closely-bound asteroid, such as those which are iron-rich.

A mosaic of enhanced imagery shows the material that was ejected from the asteroid Dimorphos as a result of the DART collision. The nested “windows” in the picture reflect how the exposure was adjusted to compensate for the brightness of the material. Credit; NASA

Given this, getting an early a warning as possible of a potential impact so that the threatening asteroid or comet could be struck at a point in its orbit where it is far enough from Earth, it only requires a slight alteration to its orbit in order to be deflected.

An upcoming mission that could achieve this is the Near-Earth Object (NEO) Surveyor. Due for launch in 2026, this Earth-orbiting observatory is specifically designed to seek out NEOs of 140 m diameter or larger which regularly cross Earth’s orbit around the Sun and come within 30 million kilometres of our planet while doing so.

An artist’s impression of the Near-Earth Object (NEO) Surveyor, due for launch in 2026. Credit: NASA

By using two heat-sensitive infrared imaging channels, the observatory will be able to make accurate measurements of NEO sizes and gain valuable information about their composition, shapes, rotational states, and orbits, allowing scientists and engineers to determine the best means to divert any that may come to present a real impact threat.

Gamma Ray Burst “The Most Powerful Flash of Light Ever Seen”

Astronomers just detected what may be the most powerful flash of light ever witnessed.

Gamma ray busts are the most energetic type of electromagnetic explosion known to exist in the universe. They are believed to come in two forms: short bursts, lasting around 2 seconds and believed to be caused by ultra-dense neutron stars colliding; and long bursts, lasting several minutes, believed to be caused by so-called “hypernovas”, – the death explosion of really super-massive stars prior to them collapsing into black holes.

Gamma-ray bursts are the most energetic flashes of light known to exist in the universe. Credit: NASA, ESA and M. Kornmesser

Up to 100 times brighter than supernovas, and therefore also referred to as super luminous supernovae, these latter blasts can give off as much energy in a minute or so as the Sun will generate throughout its 10 billion year lifespan.

The blast detected on Sunday, October 9th by NASA’s orbiting Neil Gehrels Swift Observatory, appears to have released 18 teraelectron-volts (TeV; one trillion electron volts) – almost double the energy of any such other burst thus far detected. In fact it was so powerful, it confused astronomers. Initially, it was believed the burst came from somewhere relatively close to the solar system and that it was an X-ray burst. It took additional analysis to confirm the flash was in fact a gamma-ray burst, and that it originated some 2.4 billion light-years away – which still makes it the closest such burst ever seen.

An artist’s impression of the explosion of SN 2006gy, a superluminous supernova. Credit: NASA

Officially designated GRB221009A, the burst was far enough away to cause excitement among astronomers rather than concern. However, should such a blast occur anywhere close to our stellar neighbourhood, it could very realistically end all life on this planet. In fact, it is believed that one of the biggest mass-extinction events in Earth’s history – the Late Ordovician mass extinction (LOME) event, which occurred 450 million years ago and eliminated up  60% of marine genera and nearly 85% of marine species in the second-largest mass extinction event of Earth’s history – may well have been triggered by such a blast.

Exactly which star caused GRB221009A isn’t known at this point, but it is so bright across all spectrums – X-ray, optical, radio and gamma – it is easy for observatories on Earth to monitor, allowing an extensive catalogue of data about it to be gathered.

When you are dealing with cosmic explosions that blast out stellar remains at near the speed of light, leaving a black hole behind, you are watching physics occurring in the most extreme environments that are impossible to recreate on Earth. We still don’t fully understand this process. Such a nearby explosion means we can collect very high quality data to study and understand how such explosions occur.

– Astronomer Gemma Anderson, Curtin University in Australia

In Brief

NASA Sets November 14th for Artemis 1 Launch

NASA will now attempt to launch the uncrewed Artemis 1 mission to cislunar space on Monday, November 14th, in what could a spectacular night-time launch debut for the massive Space Launch System (SLS) rocket. A 69-minute launch window for the vehicle opens at 00:07 EST (05:07 UTC) on the 14th on what will be a “short duration” mission of 25.5 days, with splashdown off the Californian coat occurring on December 9th, 2022.

Currently, the rocket and its mobile launch platform remain in the Vehicle Assembly Building at Kennedy Space Centre, Florida, having been rolled back from Pad 39B in the face of tropical storm Ian. Whilst there, the vehicle is receiving some crucial equipment swap-outs of battery systems which have exceeded their recommended deployment periods without inspection / replacement, and a series of inspection tours to  confirm the vehicle’s overall status.

Should the mission miss the November 14th launch opportunity, two further windows will be available the same week, on the 16th and 19th November, both occurring at around 02:5 UTC.

SpaceX Stacks Ship 24 and Booster 7

Following the return of Booster 7 to the orbital launch complex at Starbase, Boca Chica, Texas, SpaceX mounted Ship 24 on top of the rocket this past week, sparking speculation that the first orbital launch attempt is very imminent.

The stacking took place on Tuesday, October 11th, and marks the first time these particular vehicles have been stacked together – the last time SpaceX stacked a Starship / Super Heavy combination, it was Ship 20 and Booster 4.

The Mechazilla “Chopsticks” lower Ship 24 onto the top of Booster 7 on Tuesday, October 11th. Note the quick disconnect (QD) arm located between booster and starship, and which – when connected – is used to provide propellants and ground power to the starship vehicle. Credit: SpaceX

Whether the stacking signified an imminent launch is somewhat doubtful. SpaceX have yet to complete a full wet dress rehearsal for both vehicles, which involves filling their respective propellant tanks to capacity, and complete a full static fire test of all 33 Raptor engines on Booster 7 (which is apparently still planned). However, the biggest factor affecting any launch attempt is that the FAA still have yet to issue SpaceX a launch licence for Starship and Super Heavy – something quite possibly dependent on the company completing all the updates and additional work on the launch platform itself, all of which has been on-going for that last several weeks. As such, any launch is unlikely to be before around the middle of November.

First Scottish Skyrora Launch End in Failure

Skyrora, the Scottish rocket start-up suffered a failure with the first launch of their Skylark L sub-orbital launcher in what was still a remarkable achievement.

The 11-metre tall Skylark L is designed to lob up to 60 Kg of science payload up to 100 km altitude. However, in its first flight on October 8th, 2022, the vehicle suffered an (undisclosed at the time of writing) anomaly, and crashed into the sea some 500 metres from the launch site.

The latter was located in a most unusual setting: the Langanes peninsula in north-eastern Iceland, a remote setting most famous for being the home of a NATO-Icelandic air defence radar station. The unusual aspect being there is no actual launch complex on the peninsula. Instead, and as well as developing their own family of rockets – of which the latest is the Skylark L – and their 3D printed engines, the company and developed a fully mobile launch system which can be shipped to any launch location in the world and have minimal impact on the environment.

Skyrora’s suborbital Skylark L rocket mounted on its mobile paunch platform on the Langanes peninsula ahead of the October 8th, 2022 launch. Credit: Skyrora

This first launch wasn’t expected to be a success, being the first-time outing for Skylark L, but the company is using it to gain experience in handling large-scale rocket launches (they have previously launches a series of small-scale supersonic rockets) ahead of planned launches from the UK mainland commencing in 2023.

Despite being just 5 years old, Skyrora is building an impressive development record – as well designing and printing their own engines and developing the Skylark L, the company is also working a 3-stage orbital rocker called the Skyrora XL capable of delivering 315 Kg up to 500 km altitude and Space Tug designed to remove space debris and maintain or replace satellites in orbit. The company plan to operate Skyrora XL from the SaxaVord Spaceport in the Shetland Isles.

Arecibo Observatory: No New Dish, and No Funding for Observatory

The National Science Foundation (NSF) has confirmed that the 305-metre diameter Arecibo radio dish in Puerto Rico will not be rebuilt.

The iconic telescope, built into a karst sinkhole on a mountain, successfully operated for 57 years, becoming famous in film and television as well as being the world-s largest radio telescope throughout most of it life before a combination of storm damage and earthquakes brought the structure low when the 900-tonne receiving platform collapsed onto the dish in 2020 (see Space Sunday: returns and a collapse).

A photograph of the receiving platform of the main radio telescope at the Arecibo Observatory prior to its collapse in 2020. Credit: University of Central Florida)

Since then the question as to whether the main dish would be rebuilt has remained somewhat open. Following the clearing of the site, the Puerto Rican government had hoped that the US government / NSF would fund a construction of a new large telescope – if not the complete reconstruction of the 305-metre dish. However, the NSF has confirmed this will not be the case; Arecibo’s position as a leading radio telescope observatory is to come to an end, although the facility will not close.

Instead, US $5 million is to be spent build on the observatory’s legacy as a key educational institution, transforming the site into a hub for science, technology, engineering and math (STEM) education. The money will cover the development of the educational facilities and their operation for an initial period of five years – but it does not provide any funding for the continued science operations using the surviving telescopes and systems at the observatory. Even so, the observatory is likely to still serve astronomy: the observatory has decades of data archived which researchers will continue to use, so papers based on that data and crediting the observatory will continue to appear on science journals and periodicals.

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