For some time, astrophysicists have argued over how many Dark Stars there might be in the galaxy, with varying opinions. (Note that astronomers use several different names for these objects: sub-brown dwarfs, Y Dwarfs, ‘planemos’). In this short article, I argue that new evidence presented about the stellar populations of open star clusters point towards there being more Dark Stars than stars in our galaxy.
When I use the term ‘Dark Star’ in my book (1) and internet articles, I’m generally referring to gas giant planets/ultra-cool dwarf stars which are several times more massive than Jupiter, up to perhaps ~13 times as massive (at this point, the gas giant begins to burn deuterium and is reclassified as a brown dwarf). Most examples of these objects (perhaps more than a few million years old) are essentially dark. By contrast, very young examples light up more brightly, because they still retain some heat from their formation. It’s a curious quirk of nature that these sub-brown dwarfs are actually smaller in size than Jupiter, despite being heavier. Because these objects are so small, and so dim, they are extraordinarily difficult to observe. Some have been found, but they are usually either extremely young (and therefore still burning brightly), or are exoplanets discovered orbiting parent stars (and so detectable through gravitational ‘wobble’ effects, or other means of finding massive exoplanets).
It has been my contention for some time that the populations of these objects are significantly underestimated. It is recognised generally that these ultra-cool dwarf stars may be free-floating objects in inter-stellar space, often as a result of having been ejected from young star systems as the fledgling planets in those systems jostle for position. Opinions about their numbers vary greatly among astrophysicists. There may be twice as many of these objects as stars, according to studies involving gravitational microlensing surveys of the galactic bulge (2). Other studies conflict with this conclusion, arguing that there may be as few as 1 object of 5-15 MJup size per 20-50 stars in a cluster (3). This discrepancy is important because the difference is perhaps as high as two orders of magnitude, and this ultimately affects our understanding of how many free-floating Dark Stars we can expect to find out there.
Their mass, lying between that of Jupiter and the deuterium-burning limit at about 13 MJup (4) seems to single Dark Stars out as rather special objects:
“An abrupt change in the mass function at about a Jupiter mass favours the idea that their formation process is different from that of stars and brown dwarfs. They may have formed in proto-planetary disks and subsequently scattered into unbound or very distant orbits.” (2)
Therefore, if the number of free-floating sub-brown dwarfs (also sometimes known as “planemos”) is on the high end of expectation, then it means that there are also likely to be far more of these objects in wide, distant orbits around their parent stars. This, in turn, increases the likelihood of there being a similar Dark Star object (or more) in our own immediate solar neighbourhood. Read More…
NASA made a big announcement this week about new exoplanets found orbiting the dwarf star TRAPPIST-1 some 39 light years away. I’ve discussed this particular dwarf star system before (1), as it was already known to have three terrestrial planets in attendance orbiting very close to this cool, fairly dim star (2,3). The dwarf star is approximately one tenth the size of the Sun, and it’s mass places it on the border between a brown dwarf and a red dwarf star. Unusually for a star this small, TRAPPIST-1 has a high metallicity, which actually exceeds that of the Sun (4).
Now, an international team of astronomers, using the Belgian TRAPPIST telescope in Chile and the Spitzer infra-red space telescope, have released details about a further four terrestrial planets in this mini-star system, three of which (e, f and g) are located within it’s habitable zone, where temperatures favour the presence of liquid water (5):
“Researchers led by Michaël Gillon, of the University of Liège in Belgium, have been studying the infrared light emitted by this miniature star and have detected drops in luminosity characteristic of transits, i.e. the passage of astronomical bodies moving across its face. As early as 2015, the first three planets (dubbed b, c and d) had been identified. Tracking the system using TRAPPIST and the space telescope Spitzer, the team was then able to identify four others planets (e, f, g and h) in 2016. Based on the frequency of these transits and the degree of reduction in luminosity of the star, they have demonstrated that these seven planets are all comparable in size to Earth (to within 15%), and orbit very close to their star.” (6)
I recently reviewed a book about Carl Sagan’s interest in ancient aliens, written by Donald Zygutis (1). Early on in his illustrious career, Sagan expressed scepticism about seeking E.T. life using radio telescopes, instead advocating a search through historical accounts and myths to determine whether our planet had been visited (2). He argued that in a standard galaxy there are so many stars/planets etc, that all you’d need to do is point the radio receiver at any given galactic source beyond the Milky Way, and alien radio signals should come screaming out at you.
They generally don’t, of course, which led Sagan to the early logical conclusion that SETI’s search with radio telescopes was bound to fail. However, this approach became the only game in town, with serious funding at its disposal, and Sagan fell into line behind it – supporting this doomed search for E.T. radio signals ostensibly from stars within out galactic neighbourhood.
Decades on, and SETI has come up with little of any merit. The odd interesting blip, sure, but nothing demonstrably repetitive, or intelligent. Other searches have also come up empty-handed, including an extensive search for highly advanced galactic civilisations using infra-red (3), based upon the theories of the physicist Freeman Dyson. Looking for an infra-red signature from other galaxies seems like a bit of a stretch to me. Sagan’s initial premise about radio waves emanating from other distant galaxies is more plausible. By staring at the tiny amount of our sky that any given distant galaxy occupies, radio telescopes can cover a lot of possible stars in a very small space. If any of them contain radio-emitting alien species, shouting for attention, then we should pick them up one would have thought. Read More…
A new theory about planet formation has posited that stars, placed under inordinate stress, could break apart catastrophically, flinging their smouldering remains out into the void at tumultuous speeds. It would take quite a force to render stars apart in this way. The supermassive black hole which lies at the centre of the galaxy creates just such an impression. Wayward stars drifting inexorably into the depths of its immense gravitational well would not fare well, during what are termed Tidal Disruption Events (1,2).
Researchers from Harvard University (namely, undergraduate Eden Girma and James Guillochon, an Einstein fellow at the Harvard-Smithsonian Center for Astrophysics), have conducted computer simulations to model what happens to this streaming material, and the results are quite extraordinary:
“Every few thousand years, an unlucky star wanders too close to the black hole at the center of the Milky Way. The black hole’s powerful gravity rips the star apart, sending a long streamer of gas whipping outward. That would seem to be the end of the story, but it’s not. New research shows that not only can the gas gather itself into planet-size objects, but those objects then are flung throughout the galaxy in a game of cosmic “spitball.”” (3)
Almost nine months after the release of their paper about the likely existence of Planet Nine (1), Drs Mike Brown and Konstantin Batygin have secured a sizeable chunk of valuable time on the Subaru telescope, based in Hawaii. If they’re right about where it is, and luck is on their side, then they may detect the elusive planet within weeks. Brown and Batygin think they’ve narrowed it down to roughly 2,000 square degrees of sky near Orion, which will take approximately 20 nights of telescope time to cover with the powerful 8.2-meter optical-infrared Subaru telescope at the summit of Maunakea, Hawaii, which is operated by the National Astronomical Observatory of Japan (2). Mike Brown is quite gung-ho about it, as can be gleaned from these extracts from a recent interview with the L.A. Times:
“”We are on the telescope at the end of September for six nights. We need about 20 nights on the telescope to survey the region where we think we need to look. It’s pretty close to the constellation Orion…We’re waiting for another couple of weeks before it’s up high enough in the sky that we can start observing it and then we’re going to start systematically sweeping that area until we find it.
“”It makes me think of the solar system differently than I did before. There’s the inner solar system, and now we are some of the only people in the world who consider everything from Neptune interior to be the inner solar system, which seems a little crazy.”” (3)
Let’s hope they’re on the money. They have quite a lot to say about some of the correspondence that comes their way from members of what might loosely be termed ‘the Planet X community’.
Not so long ago, brown dwarfs (failed stars caught in an awkward in-betweener zone between stars and planets) were hypothetical bodies. Their low stellar masses allow for only a very short period of light-emission in their early years, after which they cool and darken considerably.
“[A] brown dwarf has too little mass to ignite the thermonuclear reactions by which ordinary stars shine. However, it emits heat released by its slow gravitational contraction and shines with a reddish colour, albeit much less brightly than a star.” (1)
It was recognised early on that if they existed at all, they would be very difficult to spot – and so it proved. In recent years, the ability to detect these objects has improved considerably, including more effective infra-red sky surveys. As they have become more common, the frontier of sub-stellar bodies has dropped in mass into the ultra-cool stellar bodies known as sub-brown dwarfs – many of which would equally properly be designated as rogue gas giant planets. These objects tend to have masses below 13 times that of Jupiter (13Mj) (2). These objects have always interested me greatly, and very early on in my own research efforts I was advocating the potential importance of sub-brown dwarfs in the hunt for additional planets orbiting our own Sun at great distances (3). I used the term ‘Dark Star’ to describe these ultra-cool objects; a term suggested by a friend of mine. Some can be found orbiting stars (usually beyond 50AU) while others are free-floating entities in their own right.
Continuing the discussion from last month’s blog about planetessimal-building conditions in space beyond the solar system’s heliopause boundary (1). In my February paper, I discussed anomalous results which had come back from various space probes regarding the influx of large grain interstellar dust into the heliosphere (2). More on this in a moment. A correspondent of mine had noted similarities between what I had been writing about and previous work by Paul LaViolette, who had written about the origins of the dust picked up by the Ulysses spacecraft:
“I would suggest that the dust originates from a circumsolar dust sheath that is concentrated toward the plane of the ecliptic in a fashion similar to the disk girdling the star Beta Pictoris and that is co-moving with the Sun. Infrared observations confirm the existence of dust sheaths around other stars in the solar neighborhood, leading to the conclusion that our Solar System is similarly shrouded.” (3)
The 20 million year old star Beta Pictoris provides astronomers with the best example of a gas giant exoplanet found orbiting within an evolving proto-planetary disk, made all the more dramatic by its side-on view and the brightness of scattered light from the revolving disk:
“In 1984 Beta Pictoris was the very first star discovered to host a bright disc of light-scattering circumstellar dust and debris. Ever since then Beta Pictoris has been an object of intensive scrutiny with Hubble and with ground-based telescopes. Hubble spectroscopic observations in 1991 found evidence for extrasolar comets frequently falling into the star.” (4)
A young ‘Dark Star’, weighing in at 4 Jupiter masses, is one of only a few such exoplanets to have been directly imaged. It’s also a rather curious object for another reason: It’s orbiting the main star of a triple star system some 340 light years away, in a dynamical arrangement which lies on the very edge of mathematical possibility (1). HD131399ab is just 16 million years old, and could be classified as an ultra cool sub-brown dwarf rather than a Jovian class gas giant. At this youthful age its temperature is about 600 degrees Celsius, allowing it to be directly imaged in infra-red by SPHERE operated by the European Southern Observatory.
The triple star system is indeed curious. The two minor stars (B and C) orbit the main star A at a distance of about 300 Astronomical Units, all the time twirling around each other at approximately Saturn’s distance from the Sun. The newly discovered exoplanet, HD131399ab, also orbits around the main star A in a wide orbit “about twice as large as Pluto’s if compared to our solar system, and brings the planet to about one-third of the separation of the stars [B & C] themselves.” (2). The massive planet’s orbit around its parent star is by far the widest known orbit within a multi-star system.
I’ve been hinting in recent blogs that I have been developing a new idea about the Planet X phenomenon. I’ve held off writing about it for a while because I wanted to try to present the idea at a conference and gauge the reaction to the idea. That opportunity presented itself at the ‘Il Ritorno di Planet X Nibiru’ conference held in Rome on 29th May 2016, at which I was the keynote international speaker (1). I presented two one-hour talks, and during the second one I discussed the arguments behind this new idea, complete with some explanatory slides. There were some light-bulb moments among the delegates, I’m happy to say, and so I think it’s a good time to present part of this thesis in a very concise way here, for general consideration. A more detailed examination of this idea may be the subject of a future book.
The two moons of Mars have always presented planetary scientists with something of a mystery. These tiny moons, Phobos and Deimos, whizz around Mars at no great height at all: Phobos whips around the red planet in less than 8 hours, at a height of only 3,700 miles – the closest of any moon to its parent planet. I say ‘parent’ advisedly because a new theory of the origin of these peculiar little moons suggests that they emerged from a major impact between mars and a dwarf planet. It has generally been assumed that they were captured asteroids, but the relative circularity of their orbits argued against such a capture. Work on the possibility of a catastrophic origin was carried out last year by two separate teams of researchers, after decades of battling intense scepticism within the scientific community (1). An important finding of the modelling at that time was that the resultant debris would circulate around the red planet at a relatively low altitude, which is in keeping with the orbits of the two extant moons.
More recently, further computer modelling of various impact scenarios carried out by one of those teams has narrowed down the range of masses of an impactor to about the size of Pluto. The resultant debris field was initially far more extensive than the two moons left today: