Space Sunday: exoplanets, starship and the Sun as a lens

An artist’s impression of H260655b and H260655c orbiting their parent star. Credit: SciNews.

Two new “super Earth” exoplanets have been confirmed as orbiting a star just 33 light-years (10 parsecs) from our own, making them two of the closest rocky exoplanets to Earth to be thus far be located.

Such is their proximity, the planets – HD260655b and HD260655c – offer new opportunities for exoplanet and comparative planetology studies. They both orbit an M-type red dwarf star, the most common  – and one of the oldest – types of star within our galaxy; these stars are both smaller and a lot cooler than main sequence stars like own own, but can also be quite violent in terms of their stellar activity. HD260655 is unusual amongst its brethren as it is somewhat brighter then most other M-type stars, given its comparatively small size. From Earth, it appears to reside within the constellation of Gemini, and is also known by a number of different catalogue designations, including Gliese 239 and Wolf 287.

HD260655b, the innermost of the two planets, zips around its parent at a giddying 2.8 terrestrial days; it is some 1.24 times the size of Earth and has 2.14 times the mass. HD260655c is much more “sedate” in its orbit, taking an entire 5.7 days to go around its parent; it is 1.53 times the size of Earth with around 3.1 times the mass.

The to planets are so close to their parent they are liable to be tidally locked, keeping the same side pointing towards the star all the time, and their estimated temperatures mean they are unlikely to support life: “b” has a temperature of around 435ºC, and likely has no atmosphere (although this is by no means certain), and “c” has an temperature averaging 284ºC – but may have a hydrogen-deficient atmosphere (so no water).

Artist’s impression of TESS in its “P/2” orbit. Credit: NASA

The planets were discovered in a 2021 review of data gathered by the NASA / MIT Transiting Exoplanet Survey Satellite (TESS) mission. Normally the confirmation process for such transiting planets – those that pass between their parent star and the point of observation to produce regular dips in the brightness of their star – can take a lot of additional work, including looking at other data about the star, repeating observations, confirming there has been no instrument error, etc. However, with HD260655, the process was accelerated because it had been tagged as having a possible planetary system in 1998 following observations using the HIRISE (now ANDES) instrument on the Keck telescope, and in 2016 following observations by the  CARMENES instrument at the Calar Alto Observatory in Spain, and the data from these instrument-based observations did much to confirm the presence of both planets.

What is particularly exciting about these two worlds is the combination of their proximity to their star, its brightness and its proximity to our own solar system, all of which makes them ideal for study by the James Webb Space Telescope (JWST).

Among other things, JWST should be able to confirm whether or not either planet has an atmosphere and the composition of that atmosphere. Should it turn out that “b” has no atmosphere but “c” does, it allows for direct observation of the role of their star in characterising each planet over time, and the manner in which M-type stars influence atmospheric loss among their worlds; this in turn allows astronomers to gain a better understanding of the nature of exoplanets orbiting other M-Type stars. Finally, study of HD260655b and HD260655c and comparisons with the rocky planets of our own system could further add to our understanding of how planetary systems in general form.

Starship Update

On June 13th, the Federal Aviation Administration  (FAA) issued its long-awaited Programmatic Environmental Assessment (PEA) concerning the SpaceX Starbase facilities at Boca Chica – and the summary is, neither the FAA nor the other government agencies that were involved in the study have come up with any significant environmental issues that would prevent SpaceX continuing with its current plans with the site.

The report doesn’t, however give SpaceX any immediate clearance to launch their first starship / super heavy orbital attempt. That requires a launch licence, which the FAA has yet to grant – and as a part of that process is that SpaceX demonstrate compliance with 75 action points raised by the PEA. Further, some of the action points will be subject to on-going review and could impact the company’s ability to secure launch licenses beyond the first. Further, the company may yet have to face direct action on the part of environmental groups in light of the fact that activities within the Boca Chica area – also a wildlife refuge – has already impacted some of the rare species living there.

Even so, it currently seems probable the SpaceX could be in a position to make their initial orbital launch attempt with a starship / super heavy combination in August 2022. As it is, the super heavy earmarked for the attempt – Booster 7 – has been equipped with its full complement of 33 Raptor engines, whilst its companion starship, Ship 24, is in the process of being fitted with its engines.

The massive “mechazilla” lifting mechanism on the launch support tower at the Starbase orbital facility, Boca Chica, was put through its paces again in mid-June, in readiness for lifting Booster 7 onto the launch table, and later stacking Ship 24 atop of it (seen bellow and to the left of the mechanism’s massive arms. Credit: BocaChicaGal / NASASpaceflight.com
In the next few weeks, we’re liable to see both Booster 7 and Ship 24 return to the launch area, with Booster 7 going through a range of static fire tests on the launch table before being mated with ship 24.

Meanwhile, at Kennedy Space, NASA has finally signalled growing (and, frankly, belated) concern about the SpaceX plans with the Pad 39A facility.

As I’ve previously reported, SpaceX resumed building a second super heavy / starship launch facility within the Pad 39A facilities the company leases from NASA. Of particular concern to NASA is the fact that SpaceX is locating the new launch platform so close to the existing Falcon 9 facilities, that the shockwave from a super heavy launch could conceivably damage the Falcon 9 pad and thus impact NASA’s ability to send crews to the International Space Station.

Pad 39A, Kennedy Space Centre, June 2022. To the left is the current Falcon 9 launch platform, sitting on top of the Apollo / Shuttle launch ramp. To the far right is the first section of the launch support tower for starship / supper heavy launches, showing the relative proximity of the two. Centre is a crane and a green structure, thought to be the start of work to install large water tanks between the two in order to deflect soundwaves from a super heavy launch away from the Falcon pad. Credit: @FarryFaz, Twitter

SpaceX appears to be trying to assuage NASA’s fears in part by installing what appears to be massive water tanks between the new launch facility and Pad 39A, possibly with the intent that the structure deflects sound away from Pad 39A. However, there is a greater threat involved in operating starship / super heavy which has not (in public, at least) been raised by NASA. To understand this threat, we need to go back to July 3rd, 1969.

That was the date on which the Soviet Union attempted to launch the second of its answer to America’s Saturn V, the N1 rocket, from the Baikonur Cosmodrome, Kazakhstan. However, seconds after lift-off the vehicle suffered a major malfunction, crashing back onto the launch pad. On impact, around 15% of the 2,400 tonnes of vehicle propellants detonated in a blast measuring 1 kiloton, obliterating the launch pad and scattering debris up to 10 km away. Fortunately, as the propellants were spread amongst 8 individual fuel tanks across the four stages of the vehicle, 85% did not detonate, but were burned in the ensuing deflagration; had they detonated, the estimated blast yield would have been closer to 7 kilotons – almost half the blast force of the first war time use of an atomic weapon (15 kilotons).

Super heavy doesn’t use multiple tanks. It effectively has two massive tanks that share a common dome (that is, the top end of one tank is the bottom of the other).  This means that in the event of a catastrophic failure, it is exceptionally likely that any detonation will involve the entire 3,600 tones of propellants on super heavy alone, again yielding a blast in excess of 7 kilotons. Such a detonation on the ground or shortly after lift-off would not only level Pad 39A, it could cause at least moderate damage to the launch infrastructure shared by pads 39A and 39B.

Imagining Exoplanets Using the Sun’s Gravity

When it comes to astronomy, gravity can be a very useful tool thanks to the way it can affect light. Back in April, for example, I wrote about the use of gravitational lensing – the bending of light from an object far, far, away by the gravity of an object much closer – to give us our first glimpse of the most distant star from our own to have yet been captured.

The star, now called Eärendel, the Old English term for “morning star” – was imaged by the Hubble Space Telescope using the gravitational lensing effect of an intervening galactic cluster. However, a team led by Slava Turyshev, a physicist at NASA’s Jet Propulsion Laboratory, California, want to take the idea of gravitational lensing to a new level, using our own Sun to image distant worlds.

In this image from the Hubble Space Telescope, a luminous red galaxy (LRG) is surrounded by the Einstein Ring artefact created by the light from a much more distant blue galaxy being distorted by the LRG’s gravity. Credit: ESA / NASA

Turyshev and his team propose the use of a network of small satellites, preferably using solar sails, that could be deployed so as to image exoplanets using a 40 cm telescope in what they call the Solar Gravity Lens (SGL).

The idea has been in development for the last three years, and Turyshev’s team have determined how to resolved many of the idea’s specific problems. One of this is that while the Sun makes an excellent gravity lens, the corona is so bright it actually blots out the Einstein Ring  – the circle of light created by the more distant object – such that it cannot be resolved. To fix this, the team determined that a satellite could, within a solar sail of the right size, use it as both a means of propulsion and effectively cover the Sun and this corona, revealing the Einstein Ring to the telescope. Determining the best size of the solar sail then allowed the team to calculate the mass and size of a satellite – thus allowing them to arrive at the optimal size for the telescope.

From that, the team have been able to work on a series of simulations based on the likely pixel size Earth-sized (or larger) would be produced at various distance up to 100 years years away, which in turn allowed them to simulate how such world would appear after processing their Einstein Ring and then deconvoluting the resultant image.

A simulation showing how Earth would look in a 128×128 resolution image captured by a 40-cm 30 parsecs away and using gravitational lensing similar to that produced by the Sun:. Left: the original 128×128 image; (c) as the image would look were it to be captured using SGL and then extracted from it Einstein Ring artefact; (r) as it would look after full deconvolution. Credit: Turyshev et al.

Further work is required to define the overall carrier spacecraft, but as Turyshev notes, SGL could provide us with insights into worlds beyond our solar system which might otherwise take years or even decades to accumulate.

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