An article titled Astronomers revisit dwarf stars’ promise appeared in the News section of the Nature journal on October 31th. The APACHE Project is cited together with analogous present and future surveys, primarly MEarth. In the article, the efforts of ground-based surveys targeted to M dwarfs are discussed in light of the findings made by the Kepler satellite. The essence of this publication is that the hard work of the Apaches is indeed required, and ground-based intensive observations are very important to increase the statistics of exoplanets orbiting cool stars. Our sleeves are always rolled up!
The number of discovered exoplanets is approaching the goal of 1000. We are very close to reach this symbolic milestone, which is relevant for all the mankind. Today, Jean Schneider of the Paris Observatory, founder of The Extrasolar Planets Encyclopaedia (http://exoplanet.eu/), has started among the members of the community interested in exoplanet science an intriguing discussion about the world-wide celebration expected in websites and magazines for the 1000th detected exoplanet. There are several open questions about how to properly communicate this to the people, all of them arising from the difficulty in providing an exact count of the new worlds discovered. Despite this, of course this achievement represents a very important occasion for raising awareness and excitement in people of OUR world about what we have done in only 20 years. Mass media will be very interested to know about it, and the community must arrive prepared to the appointment by providing shared and enthusiastic answers. Even if the 1000th planet will be necessarily a ‘conventional’ choice, what is real is that today it is technically within our grasp to discover life on Earth-like planets and new investments are necessary to reach this goal, which will profoundly influence all the mankind and change our way of thinking.
Yesterday, it was a glorious and balmy day in the Aosta Valley. The OAVdA astrophysicists had just begun a new working day when they were told by two Turin astronomers (members of the Apache team) that they were coming up with an unexpected guest. He’s Douglas N. C. Lin, Professor of Astronomy and Astrophysics at the University of California in Santa Cruz. Prof. Lin is one of the world leading experts in planetary systems formation theories. His research interests have spanned, over time, several fields like stellar clusters dynamics, galaxy formation and the properties of the Large Magellanic Cloud, to mention but a few. A symposium was specifically organized in occasion of his 60th birthday to honor his outstanding contributions to astronomy. The symposium was held in June 2009 in Prato, Italy and was promoted by the Melbourne-based Monash University.
Scientific knowledge is anything but conclusive. And much the more so if you consider theories about planetary formation around stars. We have only a very incomplete knowledge on this subject.New theories are continually being discussed as long as observations help us to take closer and closer views to nearby stars and the planets that are being formed in their proximity. Thus, it often happens to discover something that looks unlikely today … and is probably due to look much moreordinary tomorrow. Astronomers from across the world – including the APACHE team working at the OAVdA – always bear this statement in mind.
This is the case of the star TW Hydrae and its intriguing story. This star is an early M dwarf, 176 light years away, less massive and dimmer than our Sun. It came to the limelight in 2007 for a supposed-to-be Jovian planet orbiting it at a mere 0,04 AU distance. But this planet afterwards turned out to be just a spot on the star’s surface …
No planets then? TW Hydrae is also well-known among astronomers because it is surrounded by a gas and dust disk that is supposed to be a planetary system under construction. The Hubble Space Telescope has detected a gap in this debris disk that points towards the presence of an object that ispicking up material from the disk: a newborn planet that is coming to life. The gap and the budding planet are located over 10 billion km from the star, two to three times the distance to Neptune from the Sun.
So, what’s the deal with it? Why does it challenge current knowledge about planetary formation?The fact is, that astronomers reckon planets to take tens of millions of years to be formed. Moreover, at so large a distance from its parent star, a planet would take longer to grow up sweeping stuff from the disk because of its slow orbital motion, and because of a supposeddeficiency of material at such distances. But TW Hydrae is only 8 million years old. So what? Perhaps the mechanism involved on this planet’s formation is different from what astronomers think. In fact, an alternative theory suggests that in proper conditions gravitational instabilities would eventually trigger a collapse capable of building up a planet in a few thousand years only. But this is not the whole story. Other measures point towards a 6 to 28 Earth masses for the planet under inspection, and this is much less than needed to bring about planetary formation via thegravitational instabilities mechanism.
So, the problem is still there. Astronomers plan to use ALMA and the James Webb Telescope in the future to cast more light upon this system. If there’s but one thing astronomers know, it is how uncertain our knowledge about planetary formation is to date.
It is sunrise here in the Alps and a very good night has just gone by. While analyzing the data collected last night, we observed an M dwarf of the Apache Input Catalogue flaring (see the light curve in figure. Time (HJD) is on the X-axis). Instead, tonight the star was quite all the time. Since July 2012, when APACHE officially started, it is the first time that we clearly observe a stellar flare occurring on one of our target stars. This should mean that our observing strategy is sensible to flares, which usually last just for few minutes. The star seems to be a mid M dwarf and it should be located at nearly 75 light years from us: when the flare occurred, the Earth was plagued by the Second World War. We did not find in literature any information concerning the activity of this red dwarf, so this appears to be a new finding from APACHE!
This is for sure a very hot topic! The lively debate concerning the occurrence rate of habitable terrestrial planets around red dwarfs produced a new paper by R. Kopparapu (Penn State University) accepted by the Astrophysical Journal Letters and available here as a pre-print. The manuscript entitled A revised estimate of the occurrence rate of terrestrial planets in the habitable zones around Kepler M-dwarfs is an update of the recent paper by Dressing & Charbonneau that we have advertised in a previous post. According to the new calculations of Kopparapu, based on the Kepler data and new estimated limits for the Habitable Zone (HZ) boundaries, the frequency of terrestrial planets (0.5-1.4 Earth radius) in the HZ of cool stars is increased to 0.48-0.53, while Dressing & Charbonneau calculated the lower value 0.15. Assuming Earth-size planets with 0.5 – 2 Earth radius, the frequency increases to 0.51-0.61 planet/star. So, the potential for finding Earth-like planets around M dwarfs may be higher than previously reported, and the Apaches will search for them with greater enthusiasm!
Today we have received and mounted the telescope number 5 of the APACHE array. In few days it will be operating with the other four already functioning since July, 2012.
Superman locates his home planet Krypton around an M-dwarf… but that star is not a target observed by APACHE!0
Recently, Superman has found the location of his home planet Krypton (http://www.guardian.co.uk/culture/us-news-blog/2012/nov/05/neil-degrasse-tyson-superman-planet). It is orbiting the close M-dwarf star LHS 2520, that is located 27.1 light years from Earth. Unfortunately, the APACHE observations can not confirm the existence of the planet because the star is not included in the list of the monitored targets… However, APACHE is looking for planets which could be home of other super heroes! Stay tuned.
The APACHE Project will be presented tomorrow (7th November, 2012 at session 2/3: 12.00-12.20) at the GREAT-ESF Workshop “GAIA and Exoplanets: GREAT Synergies at the Horizons in Turin Nov 5-7, 2012.
We will be there with an oral contribution of Mario Damasso, PhD Student at Doctoral School in Astronomy, University of Padova, and scientific researcher at the OAVdA:
The APACHE Project: searching for transiting planets around cool stars
Here you can find the abstract and more information.
and with a poster by Jean Marc Christille, PhD Student, University of Perugia and scientific researcher at the OAVdA:
THE APACHE Survey Hardware and Software Design: Tools for an Automatic Search of Small-size Transiting Exoplanets
Here you can find the abstract and more information
As soon as possible we will publish the slides and the poster.