Day: December 26, 2017

Space update special: the 8-exoplanet system and AI

Posted on by Inara Pey
Artist’s impression of the Kepler-90 planetary system. Credit: NASA / Wendy Stenzel

I missed my usual Space Sunday slot due to Christmas activities taking up much of my time, so thought I’d round out the year of astronomy / spaceflight reporting with a last look at a subject that has dominated space news this year: exoplanets.

Back in February, it was confirmed that a red dwarf star had no fewer than seven planets in orbit around it, all of them roughly Earth-sized, and three of them within the star’s habitable zone (see Space update special: the 7-exoplanet system for more). At the time it was the largest number of planets thus far found to be orbiting a star – in this case, TRAPPIST-1, as it is informally called – named for the Transiting Planets and Planetesimals Small Telescope (TRAPPIST) system that discovered it.

At the time, the discovery meant TRAPPIST-1 tied with Kepler-90 for having the most exoplanets discovered to date orbiting it. However, as announced earlier in December, Kepler 90 has now regained the title, thanks to the work of a researcher from Google AI, and an astronomer from the Harvard-Smithsonian Center of Astrophysics (CfA), with the discovery of an eighth planet orbiting the star designated Kepler-90. However, what is particularly interesting about this discovery is both the way in which it was made.

Located about 2,545 light-years (780 parsecs) from Earth in the constellation of Draco, Kepler-90, unlike TRAPPIST-1 and the majority of other planet-bearing stars, in not a M-class red dwarf star. Rather, it is a G-class main sequence star, with approximately 120% the mass and radius of the Sun. It is thought to be around 2 billion years old and it has a surface temperature of 6080 Kelvin – compared to the Sun’s 4.6 billion years of age and 5778 Kelvin surface temperature. Thus, the star and its planetary system has certain key similarities to our own solar system in terms of Kepler-90’s nature, the number of major planets now known to be orbiting it, and their distribution – the smaller rocky planets being closer to their parent than the system’s gas giants.

The Kepler system roughly compared in terms of planet sizes, with our own. Credit: NASA / Wendy Stenzel

The Kepler designation for the star indicates it was a subject of study for the Kepler Space Telescope. Prior to that, the star was designated 2MASS J18574403+4918185 in the Two Micron All-Sky Survey catalogue, compiled following the 1997-2001 whole sky astronomical survey of the heavens visible from Earth. At that time, transit data gathered from earth-based observations suggested it may have a planet orbiting it, so it was made a target for observation by Kepler, and re-designated Kepler Object of Interest 351 (KOI-351). In 2013, thanks to Kepler’s observations, it was confirmed the star had six or possibly seven planets orbiting it (the outermost remained a subject of doubt for a while after it was initially identified).

All seven of the initial discoveries were made using the transit method (Transit Photometry) to discern the presence of planets around brighter stars. This consists of observing stars for periodic dips in brightness, which are an indication that a planet is passing in front of the star (i.e. transiting) relative to the observer. Kepler’s data revealed the seven planets orbiting the star over a period of two months, with the planets being designated as follows (in order of distance from their parent star):

Kepler-90 b Kepler-90 c Kepler-90 d Kepler-90 e Kepler-90 f Kepler-90 g Kepler-90 h
Radius: 1.31 Earth Radius: 1.19 Earth Radius: 2.9 Earth Radius: 2.7 Earth Radius: 2.9 Earth Radius: 8.1 Earth Radius: 11.3 Earth
“Super Earth” “Super Earth” “Mini Neptune” “Mini Neptune” “Mini Neptune” “Saturn size” “Jupiter size”
Orbital period: 7 days* Orbital period: 8.7 days* Orbital period: 59.7 days* Orbital period: 92 days* Orbital period: 125 days* Orbital period: 210 days* Orbital period: 311 days*

*=terrestrial days

However, while the system does have similarities to our own, all of the planets within it orbit much closer to their parent star than do the planets of the solar system. So much so that the largest and outermost of those discovered, the Jupiter-sized Kepler-90 h, is the only one to orbit within the star’s habitable zone – the point at which liquid water and other essentials for life might exist in the right combinations. And while it may well sit on the inner edge of the star’s habitable zone, given that Kepler-90 h is a gas giant world somewhat equitable with Jupiter in size and mass, it is highly unlikely it is a suitable environment in which life might arise – but there is the intriguing question that should it have a sufficiently large moon orbiting it – say one the size of Titan or Ganymede – which has a good magnetic field protecting it, life might arise there.

The inner planets of the system, while more Earth-like in their size, are unlikely to support life, even if the three “mini Neptunes” were to prove to be solid bodies with atmospheres. Kepler 90 b through Kepler 90 e all orbit within or at about the same distance Mercury orbits the Sun, meaning they all experience similar or hotter surface temperatures the innermost planet of the solar system experiences. Kepler-90 f orbits at approximately the same distance as Venus does from the Sun, which likely means that if it is a mini-Neptune and, it could well be like Venus it terms of the conditions within any atmosphere it might have.

The Kepler-90 planetary orbits compared to those of the solar system’s planets. Credit: NASA / Wendy Stenzel

Continue reading “Space update special: the 8-exoplanet system and AI” →

Two quirky stops in Sansar for the holidays

Posted on by Inara Pey
Sansar: The Violin Tree

As it is the holidays and a time for fun and games, I thought I’d blog about two quirky experiences in Sansar which are easy to hop into and enjoy.

The first is the Violin Tree, by Mikki Miles, which offers a fun little trip into the world of music in an abstract kind of way – and one easily missed if not careful. The setting is simple enough: a square, hilly island rising from open waters, a circular lake at its centre. To one side, a down the slope from the spawn point, a wooden jetty points towards a raft floating on the water. A walk out along the jetty will reveal several things: the first is that half of it is a xylophone, which is playing randomly. The second is that a voice is singing over on the raft – but don’t try to walk to it over the water! The singing comes from a megaphone sitting on the raft alongside a wooden frame containing Sandro Botticelli’s Venus from The Birth of Venus (circa 1480-1490), with a granite sculpture sitting on the other side of the frame (if you want to get close use F4 + the movement keys to freecam over the water).

Sansar: The Violin Tree

Atop the island, each flanking a central body of water, sit a tree – the titular violin tree – and the 40,000 year-old bone flute of the experience description. On the lake, a little rubber duck scoots around, attracting attention; walk towards it and as you reach the edge of the lake, the duck vanishes as a gigantic piano rises from the water, the fall board and main lid opening before the piano starts to play Handel’s Water Music – albeit it slightly tinny. Similarly, approach the tree and / or bone flute, and they will also impart a music excerpt, while the brass “piping” rising from the outer slopes of the island are revealed to be the tubing of trumpet, horn or trombone.

But that’s not all. To one side of the island there sits what appears to be the entrance to a mine.  Visitors can enter it and follow the tunnel down into the island, where a little more musical fun is to be had, including a nice tip-of-the-hat to the Rolling Stones.

The Violin Tree isn’t a hugely ambitious experience – but it is one cleverly considered, which makes good use of ambient sounds and trigger volumes to offer an eclectic little musical / art / historical  visit.

Sansar: The Violin Tree

Back in September I visited the Reverse Perspective Art gallery by JackTheRipper, which offers a fascinating tour into the world of reverspective art, as conceived by Patrick Hughes (see here for more).  This is actually one of two art / optical illusion focused experiences created by JackTheRipper, and I for my second little recommendation, I offer the second: his Optical Illusions Arena.

Exceedingly simple in presentation – to the point where it might initially seem to be just a random space where someone has been playing – the Optical Illusions Arena again has more to it than may at first appear to be the case. As the name suggests, it is a space containing images and items designed to trick the eye through the use of set observation points, forced perspective and so on. What’s more, it works in either VR or Desktop mode.

Sansar: Optical Illusions Arena – from one vantages point, an odd painting on the floor (l); from another, a ladder against a wall (r)

Scattered around the single-room arena are a number of elements, some in 3D – such as what at first appears to be a collection of sticks hanging in the air – through to seemingly random paintings on the floor. Also appearing on the floor are a series of red dots with arrows indicating a direction in which to look. When standing on one of these and looking in the direction indicated either in VR mode or first-person (F3) view in Desktop mode, will reveal the secret of one of these random collections or paintings. Thus, the group of coloured sticks becomes as set of painted wooden chairs, the odd splodge of white-and-grey on the ground becomes an opening in the floor, and so on.

If visiting with a couple of friends, the reproduction of an Ames room can offer the most interesting effect. When viewed from the observation point outside of the room, two avatars entering it through the doors on either side will appear to be very differently sized, one to the other, and interesting effects – from the observer’s perspective – can then be had as they move around the room.

Sansar: Optical illusions Arena – the Ames room will make two avatars appear to be different sizes when they are apparently the same distance from the observer (note: the disjointed element of the image is due to my attempt to demonstrate the effect with one avatar and two photos, not a reflection of the build)

Neither the Violin Tree nor Optical Illusions Arena are going to set the world on fire in terms of being major attractions – but that’s not the intend of either. They’re about having a little bit of fun while experimenting in 3D and with Sansar’s tools. As such, if you find yourself with ten or fifteen minutes on your hands, why pay them both a visit?

Experience URLs