Over the last two decades we have seen quite a few fictional astronomical settings become very real. One of them is the idea of a planet with two suns.

In Star Trek we have seen planets that have two suns. We were first introduced to the tourist world of Risa in Star Trek: The Next Generation’s “Captain’s Holiday,” and revisited this world many times with Enterprise NCC-1701-D as well as Enterprise NX-01 under Captain Archer. Even some of the Deep Space Nine crew had occasion to visit.

Figure 1: A beautiful double sunset on the beach of the Temtibi Lagoon on Risa. Source: Memory Alpha.

While the Vulcan system consists of one star with planets, the star itself is part of a trinary system, 40 Eridani, also known as Omicron Eridani, about sixteen lightyears away from Earth. Though it was never stated explicitly, most astronomer fans now accept 40 Eridani A as the primary star for Vulcan. Being part of a trinary system, the other two, the white dwarf star 40 Eridani B and the red dwarf star 40 Eridani C, would not only stand out in the night sky (apparent magnitudes of -8 and -6 respectively), but would also be visible during the day. To compare bright object visible from Earth, Venus has an apparent magnitude of -4.7, while the Moon has -12.6. The magnitude scale is a reverse scale, in that the smaller (or more negative) the number, the brighter the object. The faintest objects we can see with the naked eye have magnitudes of about +6. All of which means that while technically Vulcan has only one sun, people would be able to see three stars during the day.

Figure 2: Two stars visible in the Vulcan sky (visuals from a video game). Source: Memory Alpha.

Figure 3: The Vulcan system in an Okudagram. We can see that 40 Eridani A is in a binary configuration with the binary system of 40 Eridani B and C. 40 Eridani A has three planets, a closer one, and the binary planet of Vulcan and T’Khut. Source: Memory Alpha.

All of this was fiction until pretty recently. I remember having a conversation with fellow astronomers at a meeting many years ago over coffee, and everyone thought while having planets around stars in wide binary systems was no problem, in the case of close binaries the gravitational forces would disrupt any developing protoplanetary disks preventing planets from forming. While that is still true, what about cases of extremely close binaries, so that a disk could form around both stars?

What was thought to be impossible has now been shown to be quite real. The Kepler Space Telescope and other observatories have found several systems with very close binaries that are orbited by planets.

Figure 4: An artist's rendition of planet Kepler-34b in orbit around its two suns. Credit: Image by David A. Aguilar, Harvard-Smithsonian Centre for Astrophysics.

Figure 5: An artist's rendition of planet Kepler-35b in orbit around its two suns. Credit: NASA/ Lynette Cook.

Figure 6: This is an artist’s impression of the roughly Saturn-sized planet orbiting two red dwarf stars in the system OGLE-2007-BLG-349, located 8,000 light-years from Earth. The stars are just 11 million kilometers apart (less than one third the distance from Mercury to the Sun), while the planet orbits at a distance of 480 million kilometers (3.2 AU, 3.2 times the distance from Earth to the Sun). Credit: NASA, ESA, and G. Bacon (STScI).

And here is a system that is quite similar to that of Vulcan, a planet orbiting a star which is also orbited by a binary pair of stars. The star is HD188753, and it is located 149 light-years from Earth in the constellation of Cygnus. This is the first known planet in such a triple system.

Figure 7: An artist’s view from an imagined moon around the first known planet in a triple system, HD188753 in Cygnus. The brightest star behind the mountain is the planet’s primary, the other two stars are the binary pair. This is what the view might look like from Vulcan or T’Khut. Credit: NASA/JPL-Caltech.

And finally, the 50th anniversary of Star Trek has been noted and celebrated by astronomers and several institutions have paid tribute in unique ways. Here is one example.

Figure 8: (left) Nebulae IRAS 19340+2016 and IRAS 19343+2026 are seen by NASA's Spitzer Space Telescope. (right) With a bit of imagination they resemble Enterprises NCC-1701-D and NCC-1701 from "Star Trek". Credit: NASA/JPL-Caltech.

Here are a few links for you if you’d like to learn more about this topic.

Kepler Space Telescope:

Spitzer Space Telescope:

Memory Alpha:

If you are interested in hearing more about the latest discoveries in the physical sciences and technology in a fannish setting, come visit us at Shore Leave next summer (7-9 July 2017). This fan-run convention features over 12 hours of science programming, in addition of course to all the usual con activities. For more information please visit http://www.shore-leave.com.

Inge Heyer


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