Category: Space Sunday

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.

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” →