Tag: Astronomy

I’ve written a lot about Planet Nine, the mysterious, yet-to-be-discovered world thought to be orbiting far out in the hinterlands of the solar system, and potentially responsible for the odd orbits of a number of bodies in the Kuiper Belt (referred to as Kuiper Belt Objects, or KBOs). Most recently – in June 2018 – I noted that one field of research suggested that while gravity could be responsible for the eccentric orbits seen with many KBOs, it might not have anything to do with the presence of another planet.

Now a new study – Shepherding In A Self-Gravitating Disk Of Trans-Neptunian Objects – further casts doubt on – but does not eliminate – the need for any planetary object being responsible for the odd orbits of Sedna and the other unusual KBOs. In it Professor Jihad Touma, from the American University of Beirut, and Antranik Sefilian, a PhD student in Cambridge’s Department of Applied Mathematics and Theoretical Physics, suggest a disc of icy material could be the cause.

The attraction for there being a planet responsible for teasing these objects into the odd orbits is that over the last 15 years, some 30 Trans-Neptunal Objects (TNOs) have been discovered in highly-elliptical orbits, all of which would appear to a large planetary object having some form of influence on them. However, despite extensive attempts to locate this mysterious body, possibly the size of Neptune, it has remained elusive – possibly because it doesn’t exist.

The Planet Nine hypothesis is a fascinating one, but if the hypothesised ninth planet exists, it has so far avoided detection. We wanted to see whether there could be another, less dramatic and perhaps more natural, cause for the unusual orbits we see in some TNOs. We thought, rather than allowing for a ninth planet, and then worry about its formation and unusual orbit, why not simply account for the gravity of small objects constituting a disc beyond the orbit of Neptune and see what it does for us?

– study co-author Antranik Sefilian

Instead, he and Touma modelled the full spatial dynamics of TNOs, taking into consideration the influence of the known giant outer planets in the solar system and a massive, extended disc of material beyond Neptune. Their results suggest that such a large – if yet-to-be-discovered – disc of material were to be orbiting the Sun at a great distance, it could give rise to TNOs occupying highly elliptical and exaggerated orbits around the Sun. In addition, they were able to model mass ranges and shapes for the icy disc and demonstrate how gradual shifts in its precession rate, could give rise to the wilder orbits seen with the 30+ eccentric TNOs.

If you remove planet nine from the model and instead allow for lots of small objects scattered across a wide area, collective attractions between those objects could just as easily account for the eccentric orbits we see in some TNOs.

– study co-author Antranik Sefilian

However, there is a problem with the theory – or two issues at this point in time. The first is that, like Planet Nine itself, it’s one things developing a computer model that demonstrates of a disc of distant material can influence TNOs and drive them into strange orbits, it is quite another to physically find it. The second is that attempts thus far made to estimate the mass of icy objects beyond Neptune have only added up to about one-tenth the mass of Earth – which is far too little to have any significant influence over TNOs. Part of the problem here is that as we’re inside the disc and looking out at it, it is incredible hard to sport the material that might be a part of it – something which Sefilian and Touma acknowledge.

But there is more than enough evidence found around other solar systems to suggest extended discs of icy material are actually quite commonplace, and so one could well by surrounding our own.  What’s required is a longer, more considered look and the space around us – something that may well take time. And even then, Touma and Sefilian acknowledge that while their study suggests there is no need for any mystery planet, the hunt for Planet Nine shouldn’t be entirely abandoned; it might be that both it and a distant icy disc of objects might be responsible for the “rogue” TNO orbits far outside the plane of the ecliptic.

New Horizons Returns Best View Yet of Ultima Thule

On January 25th, 2019 NASA and John Hopkins University revealed the most stunning picture of Ultima Thule thus far returned by the New Horizons mission as it flew by the Kuiper Belt object (KBO) on January 1st, 2019.
Obtained with the wide-angle Multicolor Visible Imaging Camera (MVIC) the image was captured when New Horizons was just 7 minutes from its point of closest approach to the KBO, and just 6,700 km (4,200 mi) from it.  With an original resolution of 440 feet (135 meters) per pixel, the image was stored in the spacecraft’s data memory and transmitted to Earth on January 18th/19th, where it went through a process designed to sharpen the image and enhance fine detail.

The oblique lighting of this image reveals new topographic details along the terminator, near the top. These details include numerous small pits up to about 0.7 km (0.4 mi) in diameter. The large circular feature, about 7 km (4 mi) across on the smaller of the two lobes, also appears to be a deep depression. It’s currently unclear whether these pits are impact craters or features resulting from other processes, such as “collapse pits” or the ancient venting of volatile materials.

This new image is starting to reveal differences in the geologic character of the two lobes of Ultima Thule, and is presenting us with new mysteries as well. Over the next month there will be better colour and better resolution images that we hope will help unravel the many mysteries of Ultima Thule.

– Alan Stern, New Horizons Principal Investigator

Continue reading “Space Sunday: planet 9, Ultima Thule and space vehicles” →

The night of January 20th/21st, 2019 marks the only total lunar eclipse visible from the Americas this year – one which also includes Europe and parts of Africa (for those willing to either stay up or get up very early).

Dubbed by some a “Super Blood Wolf Moon”, the eclipse is somewhat unique in that it brings together three lunar events. “Super” refers to the fact that the Moon’s orbit around Earth is not circular but an ellipse. It varies from 362,600 km (225,300 mi) to 405,400 km (251,900 mi) on average. This means that at perigee, the Moon can look up to 30% “brighter” than it does at apogee, and is thus a “supermoon”.

“Blood” is derived from the fact that during an eclipse, the Earth lies between the Sun and the Moon, and the Earth’s atmosphere naturally absorbs more of the blue and green wavelengths, thus leaving more of the red wavelength to strike the surface of the Moon, giving it a bloody hue. A “wolf moon” refers to the first full Moon of January – which is winter in the northern hemisphere and the time when wolf howls were most often heard in the wild.

The entire January 20th/21st eclipse will be visible from start to end from all of both North and South America, and from the UK, Ireland, Portugal, Norway and parts of Sweden and northern Russia. Elsewhere in Europe, the eclipse, including totality – when the Earth’s shadow fully covers the Moon – will be visible across Western Europe, but elements of the entire event – such as of the part of penumbral phase or parts of the partial and total phases.

A timetable of the principal points in the eclipse is provided below.

Event	UTC / GMT	EST	PST
Penumbral Eclipse begins	21 Jan, 02:36:29	20 Jan, 21:36:29	20 Jan, 18:36:29
Partial Eclipse begins	21 Jan, 03:33:54	20 Jan, 22:33:54	20 Jan, 19:33:54
Full Eclipse begins	21 Jan, 04:41:17	20 Jan, 23:41:17	20 Jan, 20:41:17
Maximum Eclipse	21 Jan, 05:12:14	21 Jan, 00:12:14	20 Jan, 21:12:14
Full Eclipse ends	21 Jan, 05:43:15	21 Jan, 00:43:15	20 Jan, 21:43:15
Partial Eclipse ends	21 Jan, 06:50:39	21 Jan, 01:50:39	20 Jan, 22:50:39
Penumbral Eclipse ends	21 Jan, 07:48:02	21 Jan, 02:48:02	20 Jan, 23:48:02

If you cannot view the eclipse directly, there are a number of other ways it can be seen and tracked:

• Livestreams available from:
  • Slooh.com starting at 03:30 UTC (22:30 EST / 19:30 PST).
  • Timeanddate.com starting at 03:00 (22:00 EST / 19:00 PST).
  • Griffith Observatory in Los Angeles starting at 04:10 UTC (20:10 EST / 17:10 PST).
  • The Virtual Telescope Project starting at 03:30 UTC (22:30 EST / 19:30 PST).
• Via mobile / tablet apps:
  • SkySafari 6 (Android and iOS).
  • Stellarium Mobile (Android and iOS).
  • Star Walk 2 (Android, iOS and Windows 10).

For a Brief Time, There Was Life on the Moon

On January 14th, 2019, the China National Space Administration confirmed that, albeit briefly, there was life on the Moon.

Admittedly, the life in question was not alien or natural to the Moon, and had been placed there by the Chinese themselves, but it was still a major milestone in the Chang’e 4 mission and China’s lunar aspirations. At its heart is an experiment referred to at the Lunar Micro Ecosystem (LME).

A 2.6 kg (5.7 lb) sealed stainless-steel cylinder containing bioscience test loads, LME designed to test whether Earth plants and organisms can grow in the harsh conditions and reduced gravity on the lunar surface. It includes six types of organisms: cotton seed, potato, rapeseed, Arabidopsis thaliana (a flowering plant), as well as yeast and fruit fly eggs.

The unit has environmental systems keep the container hospitable and Earth-like, except for the low Lunar gravity, low temperatures and radiation. It had been hoped that together, the mix of fly eggs and plants would form a simple synergy: the eggs would hatch with the larvae producing carbon dioxide to assist with plant growth, with the plants producing oxygen (and food) for the fly larvae to progress to flies; the yeast would then help with regulating the carbon dioxide and oxygen. This type of research into developing closed ecological systems is seen as a means of helping to develop biological life support systems for long duration space missions in orbit, on the Moon and to other planets.

Within a few hours after landing on January 3rd, 2019, the biosphere’s temperature was adjusted to 24°C and the seeds were watered. The cotton seed was the first to sprout, as seen in images recorded on January 7th, 2019, that were included in the report issued by CNSA. It was also indicated that the rapeseed and potato seeds had also sprouted and were growing well as of Saturday, January 12th, although no photos were included in the report. It’s not clear what happened with the other seed or the fruit fly eggs.

The celebrations on the success of the project were short-lived however, with the onset of the lunar night. In the region Chang’e 4 occupies on the far side of the Moon, temperatures started to fall rapidly at the end of the two-week lunar day, and as the LME chamber does not have any heating systems, it was reported on January 16th that the sprouts had died due to the cold, and the experiment is now regarded as being “over”.

Despite this, the Chinese believe they learned enough from LME to be of use in designing future tests to determine how terrestrial organisms fair in a sealed and pressurized lunar environment.

Continue reading “Space Sunday: of the Moon and exoplanets” →

We set a record. Never before has a spacecraft explored anything so far away. Think of it. We’re a billion miles farther than Pluto [and] Just like with Pluto, we could not be happier. What you’re seeing is the first contact binary ever explored by spacecraft: two completely separate objects that are now joined together.

– Alan Stern, New Horizons principal investigator

The astronomical year got off to a flying start on January 1st, 2019 when NASA’ New Horizons vehicle – the same craft that flew by Pluto and Charon and their attendant moons in 2015 – shot past (486958) 2014 MU₆₉, a trans-Neptunian Object (TNO) residing in the Kuiper belt. A relatively tiny object, and dubbed Ultima Thule, it wasn’t even known about when the New Horizons mission launched in January 2006.

As I noted in my previous Space Sunday report, Kuiper Belt objects are of particular interest to planetary astronomers and scientists as they represent the oldest near-pristine material in the solar system, and so could contain many secrets, from how rocky planets formed through to the origins of life. Ultima Thule itself has been of particular interest because data gathered from the Hubble Space Telescope (HST) suggested it might be a binary object due to its apparent brightness fluctuating, suggesting two bodies orbiting one another. However, as New Horizons slipped into the final days leading up to the fly-by, it seemed to report no variance’s in the light reflected by the object.

The space craft reached its point of closest approach to Ultima Thule at 05:33 UT on the morning of January 1st, 2019. However, the nature of the approach, coupled with the huge distance between Earth and the vehicle meant that the first images and data wouldn’t be received for several hours after the probe has passed the object (it takes over 6 hours for radio signals to reach Earth from the vehicle), so at the time of closest approach, scientists and the public had to make do with the images received in the 24 hours preceding it.

These images, captured while New Horizons was still more than 1 million kilometres (635,000 mi) from Ultima Thule, were enough to confirm that, rather than being either a single elongated object (as suggested by the lack of variance in brightness the probe was recording) or two objects orbiting one another, Ultima Thule is in fact a “contact binary” – objects conjoined after gently colliding with one another, to form a shape initially referred to as a “bowling pin” (this latter changed to “dirty snowman” as clearer images were received). They also revealed why New Horizons wasn’t seeing any brightness variations: whereas Hubble was seeing Ultima Thule from more of an “end on” angle (like a bottle tumbling through the air towards you), New Horizons was approach it more-or-less along its axis of rotation (like standing in front of a slowly turning propeller), so it was always reflecting the same amount of light.

The initial images led members of the New Horizons mission team to call Ultima Thule the “first ever” contact binary object to be explored. However, this might be disputed; the nucleus of comet 67P/Churyumov–Gerasimenko, as seen by ESA’s Rosetta mission, as has two lobes connected by a narrow “neck” region which could mark it as a contact binary.

Nevertheless, there is still something magical about the way the two lobes came together – as a member of the New Horizons team put it, the bump of them joining would have been so gentle, had it been caused by a car bumping your own, it wouldn’t result in any real damage. The lobes themselves are of unequal size; at 19 km (12 mi) across, the larger has been dubbed “Ultima”, while the smaller lobe has been dubbed “Thule”, and is 14 km (9 mi) across. Combined, these give the object an overall length of some 33 km (21 mi). That they came together so gently has already been seen as a confirmation of the pebble accretion theory of planetary formation.

The exterior of both lobes is probably a mix of water, methane and nitrogen ices, doubtless mixed with other elements  / minerals, and the reddish hue revealed in the colour images thus far returned is likely the result of the irradiation of ices on its surface – a process witnessed on Pluto. However, it will not until photographs taken much closer to the object – notably those at closest approach, a mere 3,500 km (2,200 mi) – are received in mid-February, that we’ll have a clear view of the object’s topography.

Following the fly-by, the images received by mission control were taken at distances between 137,000 km (85,000 mi) and 28,000 km (18,000 mi) from the object, and part of the initial data transfer. In all, some 7 Gb of data was gathered, but due to the complexities involved, it will take 20 months for all of it to be received on Earth. In fact, at the time this article was written, and due to the passage of the Sun between the spacecraft and Earth, data transfer has been suspended for five days (January 5th through 10th, 2019) to prevent data loss due to solar interference. Even so, the images that have been received have been enough to not only reveal some of Ultima Thule’s secrets, but to also create new mysteries about it.

One of these mysteries is that computer modelling suggests that given the way the two lobes came together, Ultima Thule should have a rate of spin to complete one revolution every 3 or 4 hours. However, data from New Horizons indicates it is spinning far slower: one revolution every 15 hours. So something must have slowed it down – the question is, what?

The most obvious explanation would be the gravitational influence of nearby objects – say two or three small moons orbiting Ultima Thule. However, due to the risk of collision, the space around Ultima Thule was surveyed well ahead of the fly-by, and astronomers are convinced there is nothing orbiting it either beyond 800 km (500 mi) or closer than 160 km (100 mi) – although that does leave a fairly large sphere of space between the two which may yet reveal one or more objects. More will be known on this in late January, when data on New Horizons’ own studies of the space around Ultima Thule should be received by mission control.

Continue reading “Space Sunday: Ultima Thule and Chang’e 4” →

Mars is actually the most-studied planet in the solar system after Earth. In the last two decades alone, it has been under constant observation and study, yet we know very little about the Red Planet’s interior.

That should change from Monday, November 26th, 2018, when NASA’s latest mission to Mars, the Interior Exploration using Seismic Investigations, Geodesy and Heat Transport (InSight) lander touches down on Elysium Planitia.

The aim of the mission is to carry out a detailed examination of the Red Planet’s interior – its crust, mantle and core. Doing so can answer key questions about the early formation of the rocky planets in our inner solar system – Mercury, Venus, Earth, and Mars – more than 4 billion years ago. In addition, the data gathered may also help us to understand how rocky exoplanets orbiting other stars in our galaxy may have formed.

I’ve covered some of the more unique aspects of the mission in previous Space Sunday articles (see Insight on InSight, May 2018 and Mars Roundup, October 29th), including the use of two unique surface instruments, the Seismic Experiment for Interior Structure (SEIS) and HP3, the Heat Flow and Physical Properties Package to probe the planet’s interior. However, in order for the lander to use these, and its other instruments, it must conclude its 6-month journey to Mars with the Entry, Descent and Lander (EDL) phase – or as NASA mission engineers are calling it, 7 minutes of terror.

So-called since the 2012 landing of the Curiosity rover on Mars, it is known as such because by the time mission control receives the initial signals indicating the start of EDL, the Lander will be on the surface of Mars – in one piece or otherwise. These crucial seven minutes comprise (in the anticipated Earth Receive Time, when the signals are expected to reach NASA’s Jet Propulsion Laboratory):

• 19:47 GMT: encased in its aeroshell, InSight will enter the upper reaches of Mars’ discernible atmosphere 114 km (77 mi) above the surface of planet at 19,800 km/h (12,300 mph) at a critical 12-degree angle of attack. Any less than this, and it could bounce back into space, any greater and the heat generated by atmospheric entry could overwhelm the heat protection (designed to withstand temperature up to 1,500^oC / 2,700^oF, which is reached  2 minutes into the entry sequence), and burn-up the lander.
• 19:51 GMT: having been slowed to 1,400 km/h (860 mph) and at an altitude of 11 km (7 mi), the primary parachute is deployed. 15 seconds after this, the lower heat shield is jettisoned, and 10 second after that, the three landing legs are deployed.
• 19:52 GMT: ground sensing radar activates to measure the distance to the ground.
• 19:53:25 GMT: the lander separates from it aeroshell and parachute and the landing motors start firing as the lander orients itself for touchdown.
• 19:53:47 GMT: the motors reduce velocity from 27 km/h to 8 km/h (17 mph to 5 mph).
• 19:54 GMT: InSight touches down, with the motors immediately shutting down to avoid “bouncing” or toppling.

Depending on how systems check-out, the first image from InSight could be received by mission control about 8-10 minutes after landing – although equally, it could be received any time in the first 24 hours after landing. The Mars Odyssey orbiter should overfly the landing area at around 01:30 GMT on November 27th, and will hopefully be able to image InSight on the surface of Mars with its large, circular solar panels fully deployed – these will initially remain in their stowed  configuration for around 20 minutes following landing to allow the dust thrown up by the lander’s motors to disperse and settle so that it doesn’t interfere with their operation.

Once settled on Mars, the primary mission, designed to run for a full Martian year, will commence – although it will be one that could take time to unfold.

InSight is kind of a laid-back, slow-motion mission. It’s going to take us probably two to three months, at least, to get our instruments down, and it could be early next spring before our principal instruments started returning data.

– InSight principal investigator Bruce Banerdt

As well as direct transmissions during EDL, NASA hopes to get real-time telemetry of the landing from a pair of cubesats, called Mars Cube One (MarCO), that launched as secondary payloads with InSight in May, and which will fly past Mars during the landing.

For those who wish to follow it, the InSight landing will be broadcast on a number of NASA on-line resources available.

Continue reading “Space Sunday: seven minutes of terror and a round-up” →

Another of our Sun’s closest neighbours has been found to be home to a “super-Earth” scale planet.

Barnard’s Star, named after American astronomer Edward Emerson Barnard, is a low-mass M-class red dwarf star. As I’ve noted in previous discussions of exoplanets, red dwarf stars are the most common type of star in our galaxy, believed to account for around 70% of all stars. They can be quite volatile in nature and prone stellar flares, meaning any planets in close proximity to them are unlikely to be very habitable.

But Barnard’s Star is somewhat unusual; while it is estimated to be between two and three times older than the Sun, it has a relatively low level of activity. It also has the fastest radial (side-to-side) motion of any visible star in the night sky – something that might indicate the presence of a large planet orbiting it, causing it to wobble in its spin.

Over the years, astronomer have attempted to use the star’s radial motion to try to establish if it is the result of a planet, and in 2015, instruments used by the European Southern Observatory and the Keck Observatory suggested there could be a very large planet with an orbital period of about 230 days.

More recently, the Red Dots and CARMENES campaigns, which were responsible for the discovery of a planet orbiting our nearest stellar neighbour, Proxima B (see here for more), reviewed the data gathered from multiple sources that have studied Barnard’s Star in an attempt to ascertain whether there is one or more planets orbiting Barnard’s Star.

For the analysis we used observations from seven different instruments, spanning 20 years, making this one of the largest and most extensive datasets ever used for precise radial velocity studies. The combination of all data led to a total of 771 measurements.

– Ignasi Ribas, director of the Monstec Astronomical Observatory, and study lead

The results of this work appear to confirm that there is a planet – referred to as Barnard’s Star b – is orbiting the star roughly one every 233 terrestrial days. It has a mass of at least 3.2 times that of Earth, putting it if the category of either a “super-Earth” or a “mini-Neptune”. It is some 0.4 AU (0.4 times the distance between the Earth and the Sun) from its parent.

Because of Barnard’s Star low mass and brightness, the planet only receives about 2% of the energy that the Earth receives from the Sun. This puts it at, or beyond the star’s frost line, where volatile compounds like water, carbon dioxide, ammonia and methane condense into solid ice. As a result, the planet likely has a surface temperature in the region of -170^oC, making it inhospitable to life as we know it – although if the planet has an atmosphere, its surface temperature could be higher.

This is the first time an exoplanet has been discovered using the radial velocity method. The most common method of detection is the transit method, monitoring the period dimming of a star’s brightness as seen from Earth to determine whether a planet might be orbiting it, but such is Barnard’s Star’s dimness, this has never really been and option.

Further observations are required to completely confirm the planet’s presence, but those involved in the study – including ESO – have a high degree of confidence it will be confirmed, and observations by a number of observatories around the globe are already underway.

After a very careful analysis, we are over 99 per cent confident that the planet is there, since this is the model that best fits our observations. However, we must remain cautious and collect more data to nail the case in the future … we’ll continue to observe this fast-moving star to exclude possible, but improbable, natural variations of the stellar brightness which could masquerade as a planet.

– Ignasi Ribas

Such is the proximity of Barnard’s Star to Earth, the new planet is potentially an excellent candidate for direct imaging using the next-generation instruments both on the ground and in space – such as with NASA’s James Webb Space Telescope (JWST), scheduled for launch in 2021) or Wide Field InfraRed Survey Telescope (WFIRST), which if not threatened with further cancellation, should be launched in the mid-2020s, and the European Space Agency’s Gaia mission.

‘Oumuamua Update

In my previous Space Sunday article, I wrote about our interstellar visitor, ‘Oumuamua (officially 1I/2017 U1), which was observed passing around the Sun a year ago, and the (unlikely) potential it is some form of extra-terrestrial probe.

On November 14th, 2018, NASA issued an update on the most recent findings from data obtained on the cigar-shaped object by the Spitzer infra-red telescope.

The new report, released via NASA’s Jet Propulsion Laboratory, indicates ‘Oumuamua is off-gassing volatiles, something those proposing the alien probe idea thought to be unlikely. This off-gassing likely imparted the odd tumbling motion exhibited by ‘Oumuamua . Spitzer’s observations also confirmed that the object is highly reflective – around 10 times more reflective than the comets that reside in our solar system—a surprising result, according to the paper’s authors.

Comets orbiting the Sun spend a good deal of their time gathering dust suspended in the interplanetary medium, covering them in a layer of “dirt”. As they approach the Sun, they undergo heating, causing volatiles  – often frozen water – to start venting, “cleaning” parts of the comet’s surface and raising its reflectivity. As ‘Oumuamua, has been in the depths of interstellar space for millennia and far from any star system that could contain enough dust and material to refresh its surface, it is possible that the off-gassing confirmed by Spitzer exposed far more of its underlying ice. This, coupled with some of the icy volatiles it vented falling back onto its surface (again as can happen with solar system comets) may have resulted in the object’s higher than expected albedo.

Taken with other observations of ‘Oumuamua, the Spitzer data tends to further discount the idea that it is of artificial origin.

Continue reading “Space Sunday: exoplanets ‘Oumuamua and rockets” →

On October 19th, 2017, the Panoramic Survey Telescope and Rapid Response System-1 (Pan-STARRS-1) in Hawaii announced the first-ever detection of an interstellar asteroid, named 1I/2017 U1 (aka. ‘Oumuamua).

In the months that followed, multiple additional observations were conducted that allowed astronomers to get a better idea of its size and shape, revealing it to be strangely cigar-shaped, roughly 400 metres (1312 ft) in length and approximately 40-50 metres (130-162.5 ft) in height and width, tumbling through space. These observations also showed it may be composed of dense metal-rich rock, and that it had the characteristics of both a comet and an asteroid.

However, the report on ‘Oumuamua (roughly translated as “scout”, ou being Hawaiian for “reach out for” and mua meaning “first, in advance of” – which is repeated for emphasis) that captured public imagination is the idea that the object may have been an interstellar probe.

At the heart of this idea is the fact that ‘Oumuamua accelerated away from the Sun faster than would have been the case of it receiving a “gravity assist” in swinging around our star. Initially, it was suggested that the additional acceleration was the result of the off-gassing of volatiles  – frozen water, etc., that had been heated during ‘Oumuamua’s close swing around the Sun. However, no such off-gassing had been observed when the object was closer to the Sun, which would have been expected.

In June 2018, an alternative explanation for the acceleration was posited: that it was the result of solar pressure being exerted on the object.

However, at the end of October 2018, Shmuel Bialy, a post-doctoral researcher at the CfA’s Institute for Theory and Computation (ITC) and Prof. Abraham Loeb, the Frank B. Baird Jr. Professor of Science at Harvard University, went one stage further. They proposed that while ‘Oumuamua might well be natural in origin – it could also be the object is in fact an alien probe, intentionally sent to our solar system and which uses a light sail (or what we’d call a solar sail were it to be used with a probe sent from Earth to explore out solar system) for propulsion.

Currently there is an unexplained phenomena, namely, the excess acceleration of ‘Oumuamua, which we show may be explained by the force of radiation pressure from the Sun. We explain the excess acceleration of `Oumuamua away from the Sun as the result of the force that the Sunlight exerts on its surface. For this force to explain measured excess acceleration, the object needs to be extremely thin, of order a fraction of a millimetre in thickness but tens of meters in size. This makes the object lightweight for its surface area and allows it to act as a light-sail. Its origin could be either natural (in the interstellar medium or proto-planetary disks) or artificial (as a probe sent for a reconnaissance mission into the inner region of the Solar System).

– E-mail from Baily and Loeb on their paper concerning ‘Oumuamua

Their views were circulated to various news outlets via e-mail and cause something of a stir in the first week or so of November.

Loeb has actually been an advocate of ‘Oumuamua being of intelligent origin since it was first discovered. He was one of the first to call for radio telescopes to listen to it across a range of frequencies for any signs of transmissions from it. When the SETI Institute‘s Allen Telescope Array did so without success, he pushed for the Green Bank Telescope in West Virginia to listen for radio emissions – which it did for a 6-day period December 2017, again without success

As no signals were found to be emanating from the object, rather than drop the idea of it being artificial, Loeb has put forward the ideas that it has either malfunctioned, or it is active, and we simply can’t detect the fact that it is. He’s even suggested that given Pan-STARS only managed to spot the object after it has passed perihelion, could mean that it is only “one of many” such probes sent our way, and we’ve missed the others.

Bialy has been a little more cautious with things, pointing out the paper is “high speculative”. But the fact is, the paper does come across more of an attempt to substantiate a belief (that ‘Oumuamua is of artificial origin) than anything else, and in doing so, it does ignore certain data and makes some sweeping assumptions.

For example, the paper tends to dismiss the idea that ‘Oumuamua’s unexpected acceleration was consistent with a push from solar radiation pressure. However, Michele Bannister, a planetary astronomer from New Zealand and one of many to push back against the “ET probe” idea via Twitter, used a graphic that shows the acceleration exhibited by ‘Oumuamua’s is entirely in keeping with similar non-gravitational accelerations seen with comets within the solar system.

Continue reading “Space Sunday: ‘Oumuamua, BFS and Tianhe-1” →