Mysterious long-term dimming of KIC 8462852 may be caused by dust, astronomers say

Orbiting dust cloud – artists’ impression [credit: Karen L. Teramura]

An orbiting cloud of dust round ‘Tabby’s star’ may lack excitement for casual observers, but there it is – probably.

University of Arizona astronomer Huan Meng and co-authors have found the long-term dimming of KIC 8462852 — a main-sequence F-type star located in the constellation Cygnus, about 1,480 light-years from Earth — appears to be weaker at longer infrared (IR) wavelengths of light and stronger at shorter ultraviolet (UV) wavelengths, reports Sci-News.com.

Such reddening is characteristic of dust particles and inconsistent with more fanciful ‘alien megastructure’ concepts, which would evenly dim all wavelengths of light.

Variable sunshine— researchers explain why our Sun’s brightness fluctuates

Sunspots [image credit: NASA]

One of the authors of the research says: “The results of our study show us that we have identified the governing parameters in our model”. Both climate and exoplanet research could benefit from the findings.

The Sun shines from the heavens, seemingly calm and unvarying. In fact, it doesn’t always shine with uniform brightness, but shows dimmings and brightenings, reports Phys.org.

Two phenomena alone are responsible for these fluctuations: the magnetic fields on the visible surface and gigantic plasma currents, bubbling up from the star’s interior.

A team headed by the Max Planck Institute for Solar System Research in Göttingen reports this result in today’s issue of Nature Astronomy. For the first time, the scientists have managed to reconstruct fluctuations in brightness on all time scales observed to date – from minutes up to decades.

Trappist-1: seven-planet resonance chain confirmed

Much media attention on this new paper this week. Is there a surprise lurking in the details now that the orbit period of the seventh planet has been confirmed?.

What the numbers in the diagram show is the orbits per planet in a fixed period (top row), the conjunctions per planet pair in the same period (second row), and the ratios that represents (third row).

The number of conjunctions of any two planets is the difference between the two orbit numbers in a given period, which in this case is equivalent to just under 1446 Earth days (see data below).

Apart from the obvious symmetry of the ratios, something else arose from the science paper.

Astrophysicists find that planetary harmonies around TRAPPIST-1 save it from destruction: Why Phi?

Exoplanets up to 90 times closer to their star than Earth is to the Sun.

Excellent – we outlined this ‘resonance chain’ (as they have now dubbed it) in an earlier post here at the Talkshop [see ‘Talkshop note’ in the linked post for details].

When NASA announced its discovery of the TRAPPIST-1 system back in February it caused quite a stir, and with good reason says Phys.org.

Three of its seven Earth-sized planets lay in the star’s habitable zone, meaning they may harbour suitable conditions for life.

But one of the major puzzles from the original research describing the system was that it seemed to be unstable.

“If you simulate the system, the planets start crashing into one another in less than a million years,” says Dan Tamayo, a postdoc at U of T Scarborough’s Centre for Planetary Science.

Exoplanet discovery by an amateur astronomer shows the power of citizen science

Planetary detective work [credit: superwasp.org]

Pattern recognition is still best left to humans it seems.

You don’t need to be a professional astronomer to find new worlds orbiting distant stars, as Phys.org reports.

Darwin mechanic and amateur astronomer Andrew Grey this week helped to discover a new exoplanet system with at least four orbiting planets. But Andrew did have professional help and support.

The discovery was a highlight moment of this week’s three-evening special ABC Stargazing Live, featuring British physicist Brian Cox, presenter Julia Zemiro and others.

Atmosphere around low-mass Super-Earth detected

Size comparison of GJ 1132 b (aka Gliese 1132 b) with Earth [credit: Wikipedia]

Early indications from models suggest that ‘an atmosphere rich in water and methane would explain the observations very well.’

Astronomers have detected an atmosphere around the super-Earth GJ 1132b, reports the Max Planck Institute for Astronomy.

This marks the first detection of an atmosphere around a low-mass Super-Earth, in terms of radius and mass the most Earth-like planet around which an atmosphere has yet been detected.

Thus, this is a significant step on the path towards the detection of life on an exoplanet. The team, which includes researchers from the Max Planck Institute for Astronomy, used the 2.2 m ESO/MPG telescope in Chile to take images of the planet’s host star GJ 1132, and measuring the slight decrease in brightness as the planet and its atmosphere absorbed some of the starlight while passing directly in front of their host star.

While it’s not the detection of life on another planet, it’s an important step in the right direction: the detection of an atmosphere around the super-Earth GJ 1132b marks the first time an atmosphere has been detected around a planet with a mass and radius close to that of Earth (1.6 Earth masses, and 1.4 Earth radii).

Major Discovery! 7 Earth-Size Alien Planets Circle Nearby Star

Exoplanets up to 90 times closer to their star than Earth is to the Sun.

We did know something about this system already, but more work has led to today’s announcement.

Astronomers have never seen anything like this before, says Space.com: Seven Earth-size alien worlds orbit the same tiny, dim star, and all of them may be capable of supporting life as we know it, a new study reports. 

“Looking for life elsewhere, this system is probably our best bet as of today,” study co-author Brice-Olivier Demory, a professor at the Center for Space and Habitability at the University of Bern in Switzerland, said in a statement. 

Orbital resonance found in a four planet system

HR 8799 system [image credit: Many Worlds]

It can’t get much more obvious than this. The report says ‘it’s a one-two-four-eight resonance’ of the orbits of these massive planets, but we find it’s much nearer to 1:2:4:9, with the outer planet taking 450 years for one orbit.

The era of directly imaging exoplanets has only just begun, but the science and viewing pleasures to come are appealingly apparent says Many Worlds.

This evocative movie of four planets more massive than Jupiter orbiting the young star HR 8799 is a composite of sorts, including images taken over seven years at the W.M. Keck observatory in Hawaii. The movie clearly doesn’t show full orbits, which will take many more years to collect.

The closest-in planet circles the star in around 49 years [report incorrectly says 40]; the furthest takes more than 400 years. But as described by Jason Wang,  an astronomy graduate student at the University of California, Berkeley, researchers think that the four planets may well be in resonance with each other.

Exoplanet anniversary: 1st alien worlds confirmed 25 years ago today

Still from pulsar animation. [Image credit: NASA]

The exoplanet revolution began 25 years ago today. On Jan. 9, 1992, astronomers Alex Wolszczan and Dale Frail published a paper in the journal Nature announcing the discovery of two planets circling an incredibly dense, rapidly rotating stellar corpse known as a pulsar.

It was a landmark find: while several alien-world “candidates” had recently been spotted, Wolszczan and Frail provided the first confirmation that planets exist beyond our own solar system, reports Mike Wall.

“From the very start, the existence of such a system carried with it a prediction that planets around other stars must be common, and that they may exist in a wide variety of architectures, which would be impossible to anticipate on the basis of our knowledge of the solar system alone,” Wolszczan, who’s based at Pennsylvania State University, wrote in a note about the pulsar planets for the “Name Exoworlds” contest sponsored by the International Astronomical Union.

Earth-bound instrument analyzes light from planets circling distant stars

Subaru telescope, Hawaii (far left) [image credit: Wikipedia]

Being able to measure things like the mass, temperature and atmospheric composition of exoplanets should generate some interesting new data for analysis, with possible implications for climate theory.

A team of scientists and engineers led by Princeton researchers recently reported the successful operation of a new instrument for the Subaru Telescope in Hawaii that will allow astronomers to make direct observations of planets orbiting nearby stars.

The instrument, dubbed CHARIS, was designed and built by a team led by N. Jeremy Kasdin, a professor of mechanical and aerospace engineering. It allows astronomers to isolate light reflecting from planets larger than Jupiter and then analyze the light to determine details about the planets’ size, age and atmospheric constituents.

Alien solar system Kepler-80 has tightly spaced planets in synchronized orbits

Synchronized orbits of the Kepler-80 system [Credit: Florida Institute of Technology]

Another example of planetary resonance has been discovered thanks to NASA’s Kepler space telescope.
H/T Phys.org

Located about 1,100 light years away, Kepler-80, named for the NASA telescope that discovered it, features five small planets orbiting in extreme proximity to their star.

As early as 2012, Kepler scientists found that all five planets orbit in an area about 150 times smaller than the Earth’s orbit around the Sun, with “years” of about one, three, four, seven and nine days.

Astronomers discover a giant planet spinning up its star

An artist’s image of a hot-Jupiter exoplanet [credit: NASA]

What exactly goes on in terms of interactions between giant planets and their host star? The researchers admit the need ‘to disentangle some of the very poorly understood physics behind tidal dissipation’, as Phys.org reports. More observations needed.

A giant “hot Jupiter” exoplanet has recently been detected by an international team of astronomers led by Kaloyan Penev of Princeton University. The newly found alien world, designated HATS-18b, is an interesting case of a planet tidally spinning up its parent star.

Just 40 light years from Earth, three planets might host life forms adapted to infrared worlds

Artist’s impression [credit: ESO/M. Kornmesser]

From Phys.org:
Is there life beyond our solar system? If there is, our best bet for finding it may lie in three nearby, Earth-like exoplanets.

For the first time, an international team of astronomers from MIT, the University of Liège in Belgium, and elsewhere have detected three planets orbiting an ultracool dwarf star, just 40 light years from Earth.

The sizes and temperatures of these worlds are comparable to those of Earth and Venus, and are the best targets found so far for the search for life outside the solar system. The results are published today in the journal Nature.

Rocky ‘super Earth’ exoplanet has one side much hotter than the other

Artist’s view of 55 Cancri e [credit: Wikipedia]

Unusual atmospheric data from this exoplanet: not much heat transfer from the side permanently facing its star to the dark side, giving it a ‘large day–night temperature gradient’.

The orbit period is only 18 hours, as it’s much nearer to its star than Mercury is to the Sun. It may also have ‘an unknown source of heat’, as Phys.org reports.

An international team of astronomers, led by the University of Cambridge, has obtained the most detailed ‘fingerprint’ of a rocky planet outside our solar system to date, and found a planet of two halves: one that is almost completely molten, and the other which is almost completely solid.

Monster planet is ‘dancing with the stars’

Eccentric orbit example: Pluto [credit: NASA]

Surprisingly intricate interactions are going on ‘behind the scenes’ in some, if not all, planetary systems – including our own of course.

A team of scientists has discovered a highly unusual planetary system comprised of a sun-like star, a dwarf star, and an enormous planet sandwiched in between, reports ScienceDaily.

The planet, first discovered in 2011 orbiting a star called HD 7449, is about eight times the mass of Jupiter and has one of the most eccentric orbits ever found.

Shifting eclipses and 3:2 orbital ratio found in giant exoplanets

NASA’s next exoplanet hunter (TESS)
[image credit: MIT]

Try to imagine Saturn and Uranus orbiting the Sun in 8 and 12 days respectively. Far-fetched? In our solar system, yes, but something very similar has been observed in an exoplanetary star system, as was recently discussed by scientist and blogger Hugh Osborn, one of the co-authors of a study of the surprising 2-planet system.

In his blog post, Osborn notes re the March 2015 solar eclipse:
Calculating something so far ahead seems like an impressive feat but in fact astronomers can precisely work out exactly when and where eclipses will occur for not just the next hundred, but the next million years. Such is the way for most transiting exoplanets too, the calculations for which could probably be valid in thousands of years.

But a new planetary system, discovered by a team that includes Warwick astronomers (including me), doesn’t yet play by these rules. It consists of two planets orbiting their star, a late K star smaller than our sun, in periods of 7.9 and 11.9 days. The pair have radii 7- and 4-larger than Earth, putting them both between the sizes of Uranus and Saturn. They are the 4th and 5th planets to be confirmed in data from K2, the rejuvenated Kepler mission that monitors tens of thousands of stars looking for exoplanetary transits. (36 other planet candidates, including KIC201505350b & c, have been released previously).

But it is their orbits, rather than planetary characteristics, that have astronomers most excited. “The periods are almost exactly in a ratio of 1:1.5” explains Dave Armstrong, lead author of the study. This can be seen directly in how the star’s brightness changes over time. This lightcurve appears to have three dips of different depths, marked here by green, red and purple dips. ”Once every three orbits of the inner planet and two orbits of the outer planet, they transit at the same time”, causing the deep purple transits.

Exoplanet J1407b has a ring system 200 times larger than Saturn’s

Super-sized exoplanet rings [credit: Ron Miller / Astronomy Now]

They say ‘the diameter of the ring system is nearly 120 million kilometres’. Imagine the forces in play to keep all that in order. Astronomy Now reports:

Astronomers at the Leiden Observatory, The Netherlands, and the University of Rochester, USA, have discovered that the ring system that they see eclipse the very young Sun-like star J1407 is of enormous proportions, much larger and heavier than the ring system of Saturn. The ring system — the first of its kind to be found outside our Solar System — was discovered in 2012 by a team led by Rochester’s Eric Mamajek.

A new analysis of the data, led by Leiden’s Matthew Kenworthy, shows that the ring system consists of over 30 rings, each of them tens of millions of kilometres in diameter. Furthermore, they found gaps in the rings, which indicate that satellites (“exomoons”) may have formed. The result has been accepted for publication in the Astrophysical Journal.

Read the rest here.

Exoplanet link to Lucas number series

Jupiter-sized exoplanet [Wikipedia]

Tallbloke has spotted a science paper about exoplanets where one system has two planets whose orbital periods are close to 11:4 ratio Lucas numbers.

Paper: ‘We also refine the parameters of two planets announced previously around HD 113538, based on a longer series of measurements. The planets have a period of 663± 8 and 1818 ± 25 days, orbital eccentricities of 0.14 ± 0.08 and 0.20 ± 0.04, and minimum masses of 0.36 ± 0.04 and 0.93 ±0.06 MJup.’
[MJup = mass of Jupiter]

The outer planet is slightly smaller than Jupiter and the inner one is about one third of it, by mass. Noting the uncertainties in the orbital periods, we can see how closely they relate to the Lucas ratio:
663/3 = 221 = 55 x 4, +1
1818/3 = 606 = 55 x 11, +1
difference = 55 x 7

This is very close to 4:11 orbit ratios with 7 conjunctions in that time period, 4-7-11.

Mean motion resonances in multiplanetary systems – new study

Exoplanet analysis is a growing field of scientific study as data pours in from the likes of NASA’s successful Kepler probe.

The abstract of a new paper explains its focus on this data:
‘Mean motion resonances and near-resonances up to the outer/inner orbital period ratio’s value of 5 and the denominator 4 are tested for all adjacent exoplanet orbits.’

Without delving into the nuts and bolts of the analysis here, let’s look at the list of results (click on image to view details):

By Marian C. Ghilea (2015)

The column ‘resonance type’ shows the planet:planet ratios we’re interested in.
Clearly there are many examples, although ‘near resonances’ are also included.

From the author’s concluding remarks:
‘Performing a simple analysis, the resonance or near-resonance states present in all the multiplanetary systems known to date can be found numerically using a computer analysis tool.’

‘The first results, presented in this paper, suggest different resonance or near-resonance distributions for different planet categories. The resonance/near resonance numbers of 2/1 and 3/2 appear to be dominant for the planets with larger masses while the 5/3 resonance seems to be the most common for terrestrial planets and mini neptunes. For giant planets, the 2/1 resonances are dominating at larger distances from the host star while the 3/2 resonance is more common at close distances from it. Resonances for values higher than 5/2 are encountered
only for planets with masses larger than 10 (ME*)’ [*Earth masses].

We can see from this that these ‘near resonances’ crop up regularly in exoplanet systems just as they do in our solar system e.g. Jupiter-Saturn 5:2, Neptune-Pluto 3:2.

Whatever the mechanism(s) involved, the frequency of their appearance can’t be regarded as accidental.

***
See also the Wikipedia page on orbital resonance

Why Phi? – ‘Fractals seen in throbs of pulsating golden stars’

Kepler Space Telescope [NASA]

A very interesting report of a new science paper has appeared in the New Scientist:

‘William Ditto and his colleagues at the University of Hawaii, Manoa, compared the two strongest oscillations, or tones, made by the variable star KIC 5520878, using observations by NASA’s Kepler space telescope. They noticed that dividing the frequency of the secondary note by that of the primary, or lowest, note gives a value near the “golden ratio” – a number that shows up often in art and nature and is close to 1.618′

So is it real or did they perhaps just imagine it?
Let’s start with the abstract :

‘The unprecedented light curves of the Kepler space telescope document how the brightness of some stars pulsates at primary and secondary frequencies whose ratios are near the golden mean, the most irrational number.’