Astronomy

What planets or exoplanets orbit the Sun's elder twin HIP 102152?

What planets or exoplanets orbit the Sun's elder twin HIP 102152?


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Has anyone done any research on the planets that orbit the HIP102152? Since that star is similar to ours and older, I postulate that it's likely those planets are most worthwhile searching for advanced civilizations.


No planets have been detected in orbit around HIP 102152.

That does not mean that no planets exist, but that our current techniques are no able to detect them. Most planet are detected by the transit method. This observes the very small dip in light when a planet goes in front of the star. However if the planet's orbit doesn't line up exactly with Earth, then the planet will not be detected.

Other methods can detect large planets that orbit close to the star, or very large planets in orbit very var from the star. Solar systems like ours are harder to detect.

Given what we know about the abundance of planets, it is likely that HIP 102152 has a planetary system. But actual detection might no be possible with current technology.

Moreover there is no obvious reason to think that life or intelligent life is particularly likely just because the star is similar to the sun. The nature of the star may rule out intelligent life. But as far as we know, life just needs a reasonally stable energy source and a lot of luck. It doesn't need a solar twin.


If you look up the star on SIMBAD and view the references, you will come across some papers about a project called the Solar Twin Planet Search, which as the name implies is a project searching for planets around solar twins. The first paper in the series, Ramírez et al. (2014) "The Solar Twin Planet Search. I. Fundamental parameters of the stellar sample" lists HIP 102152 as one of the target stars for the project, which measures radial velocities using the HARPS spectrograph.

So far, nothing's shown up. If you search the exoplanet catalogues, e.g. the NASA Exoplanet Archive or the Extrasolar Planets Encyclopaedia, there are no known planets around HIP 102152. Data collected during the Solar Twin Planet Search has been used to put upper limits on the masses of planets around the star, see Figure 4 in Monroe et al. (2013) "High Precision Abundances of the Old Solar Twin HIP 102152: Insights on Li Depletion from the Oldest Sun": the limit ranges from a few Earth masses for 1-day orbits to roughly Saturn-mass planets at 1000 days. The abundances of various elements in the star do suggest that there may well be terrestrial planets orbiting the star, but they would be well below the detection limits for all but the shortest orbits.


Oldest solar twin identified: VLT provides new clues to help solve lithium mystery

This image tracks the life of a Sun-like star, from its birth on the left side of the frame to its evolution into a red giant star on the right. On the left the star is seen as a protostar, embedded within a dusty disc of material as it forms. It later becomes a star like our Sun. After spending the majority of its life in this stage, the star's core begins to gradually heat up, the star expands and becomes redder until it transforms into a red giant. Following this stage, the star will push its outer layers into the surrounding space to form an object known as a planetary nebula, while the core of the star itself will cool into a small, dense remnant called a white dwarf star. Marked on the lower timeline are where our Sun and solar twins 18 Sco and HIP 102152 are in this life cycle. The Sun is 4.6 billion years old and 18 Sco is 2.9 billion years old, while the oldest solar twin is some 8.2 billion years old -- the oldest solar twin ever identified. By studying HIP 102152, we can get a glimpse of what the future holds for our Sun. This image is illustrative the ages, sizes, and colours are approximate (not to scale). The protostar stage, on the far left of this image, can be some 2000 times larger than our Sun. The red giant stage, on the far right of this image, can be some 100 times larger than the Sun. Credit: ESO/M. Kornmesser

(Phys.org) —An international team led by astronomers in Brazil has used ESO's Very Large Telescope to identify and study the oldest solar twin known to date. Located 250 light-years from Earth, the star HIP 102152 is more like the Sun than any other solar twin—except that it is nearly four billion years older. This older, but almost identical, twin gives us an unprecedented chance to see how the Sun will look when it ages. The new observations also provide an important first clear link between a star's age and its lithium content, and in addition suggest that HIP 102152 may be host to rocky terrestrial planets.

Astronomers have only been observing the Sun with telescopes for 400 years—a tiny fraction of the Sun's age of 4.6 billion years. It is very hard to study the history and future evolution of our star, but we can do this by hunting for rare stars that are almost exactly like our own, but at different stages of their lives. Now astronomers have identified a star that is essentially an identical twin to our Sun, but 4 billion years older—almost like seeing a real version of the twin paradox in action.

Jorge Melendez (Universidade de São Paulo, Brazil), the leader of the team and co-author of the new paper explains: "For decades, astronomers have been searching for solar twins in order to know our own life-giving Sun better. But very few have been found since the first one was discovered in 1997. We have now obtained superb-quality spectra from the VLT and can scrutinise solar twins with extreme precision, to answer the question of whether the Sun is special."

The team studied two solar twins—one that was thought to be younger than the Sun (18 Scorpii) and one that was expected to be older (HIP 102152). They used the UVES spectrograph on the Very Large Telescope (VLT) at ESO's Paranal Observatory to split up the light into its component colours so that the chemical composition and other properties of these stars could be studied in great detail.

They found that HIP 102152 in the constellation of Capricornus (The Sea Goat) is the oldest solar twin known to date. It is estimated to be 8.2 billion years old, compared to 4.6 billion years for our own Sun. On the other hand 18 Scorpii was confirmed to be younger than the Sun—about 2.9 billion years old.

This 3D animation shows the life of a Sun-like star, from its birth on the left side of the frame to its evolution into a red giant star on the right. On the left the star is seen as a protostar, embedded within a dusty disc of material as it forms. It later becomes a star like our Sun. After spending the majority of its life in this stage, the star transforms into a red giant. Following this stage, the star will push its outer layers into the surrounding space to form an object known as a planetary nebula, while the core of the star itself will cool into a small, dense remnant called a white dwarf star. Marked on the lower timeline are where our Sun and solar twins 18 Sco and HIP 102152 are in this life cycle. The Sun is 4.6 billion years old and 18 Sco is 2.9 billion years old, while the oldest solar twin is some 8.2 billion years old — the oldest solar twin ever identified. By studying HIP 102152, we can get a glimpse of what the future holds for our Sun. This animation is illustrative the ages, sizes, and colours are approximate (not to scale). The protostar stage can be some 2000 times larger than our Sun. The red giant stage can be some 100 times larger than the Sun. Credit: ESO/M. Kornmesser

Studying the ancient solar twin HIP 102152 allows scientists to predict what may happen to our own Sun when it reaches that age, and they have already made one significant discovery. "One issue we wanted to address is whether or not the Sun is typical in composition," says Melendez. "Most importantly, why does it have such a strangely low lithium content?"

Lithium, the third element in the periodic table, was created in the Big Bang along with hydrogen and helium. Astronomers have pondered for years over why some stars appear to have less lithium than others. With the new observations of HIP 102152, astronomers have taken a big step towards solving this mystery by pinning down a strong correlation between a Sun-like star's age and its lithium content.

Our own Sun now has just 1% of the lithium content that was present in the material from which it formed. Examinations of younger solar twins have hinted that these younger siblings contain significantly larger amounts of lithium, but up to now scientists could not prove a clear correlation between age and lithium content.

TalaWanda Monroe (Universidade de São Paulo), the lead author on the new paper, concludes: "We have found that HIP 102152 has very low levels of lithium. This demonstrates clearly for the first time that older solar twins do indeed have less lithium than our own Sun or younger solar twins. We can now be certain that stars somehow destroy their lithium as they age, and that the Sun's lithium content appears to be normal for its age."

A final twist in the story is that HIP 102152 has an unusual chemical composition pattern that is subtly different to most other solar twins, but similar to the Sun. They both show a deficiency of the elements that are abundant in meteorites and on Earth. This is a strong hint that HIP 102152 may host terrestrial rocky planets.


Astronomers Discover a “Jupiter Twin” Around a Sun-Like Star

An artist’s impression showing a newly discovered Jupiter twin gas giant orbiting the solar twin star, HIP 11915. The planet is of a very similar mass to Jupiter and orbits at the same distance from its star as Jupiter does from the Sun. This, together with HIP 11915’s Sun-like composition, hints at the possibility of the system of planets orbiting HIP 11915 bearing a resemblance to our own Solar System, with smaller rocky planets orbiting closer to the host star. Credit: ESO/M. Kornmesser

Using the ESO 3.6-meter telescope, an international team of astronomers has identified a planet just like Jupiter orbiting at the same distance from the Sun-like star HIP 11915.

According to current theories, the formation of Jupiter-mass planets plays an important role in shaping the architecture of planetary systems. The existence of a Jupiter-mass planet in a Jupiter-like orbit around a Sun-like star opens the possibility that the system of planets around this star may be similar to our own Solar System. HIP 11915 is about the same age as the Sun and, furthermore, its Sun-like composition suggests that there may also be rocky planets orbiting closer to the star.

So far, exoplanet surveys have been most sensitive to planetary systems that are populated in their inner regions by massive planets, down to a few times the mass of the Earth. This contrasts with our Solar System, where there are small rocky planets in the inner regions and gas giants like Jupiter farther out.

According to the most recent theories, the arrangement of our Solar System, so conducive to life, was made possible by the presence of Jupiter and the gravitational influence this gas giant exerted on the Solar System during its formative years. It would seem, therefore, that finding a Jupiter twin is an important milestone on the road to finding a planetary system that mirrors our own.

A Brazilian-led team has been targeting Sun-like stars in a bid to find planetary systems similar to our Solar System. The team has now uncovered a planet with a very similar mass to Jupiter, orbiting a Sun-like star, HIP 11915, at almost exactly the same distance as Jupiter. The new discovery was made using HARPS, one of the world’s most precise planet-hunting instruments, mounted on the ESO 3.6-metre telescope at the La Silla Observatory in Chile.

Although many planets similar to Jupiter have been found at a variety of distances from Sun-like stars, this newly discovered planet, in terms of both mass and distance from its host star, and in terms of the similarity between the host star and our Sun, is the most accurate analogue yet found for the Sun and Jupiter.


An artist’s impression showing a newly discovered Jupiter twin gas giant orbiting the solar twin star, HIP 11915. The planet is of a very similar mass to Jupiter and orbits at the same distance from its star as Jupiter does from the Sun. This, together with HIP 11915’s Sun-like composition, hints at the possibility of the system of planets orbiting HIP 11915 bearing a resemblance to our own Solar System, with smaller rocky planets orbiting closer to the host star. Credit: ESO/M. Kornmesser

The planet’s host, the solar twin HIP 11915, is not only similar in mass to the Sun, but is also about the same age. To further strengthen the similarities, the composition of the star is similar to the Sun’s. The chemical signature of our Sun may be partly marked by the presence of rocky planets in the Solar System, hinting at the possibility of rocky planets also around HIP 11915.

According to Jorge Melendez, of the Universidade de São Paulo, Brazil, the leader of the team and co-author of the paper, “the quest for an Earth 2.0, and for a complete Solar System 2.0, is one of the most exciting endeavors in astronomy. We are thrilled to be part of this cutting-edge research, made possible by the observational facilities provided by ESO.”

Megan Bedell, from the University of Chicago and lead author of the paper, concludes: “After two decades of hunting for exoplanets, we are finally beginning to see long-period gas giant planets similar to those in our own Solar System thanks to the long-term stability of planet hunting instruments like HARPS. This discovery is, in every respect, an exciting sign that other solar systems may be out there waiting to be discovered.”

Follow-up observations are needed to confirm and constrain the finding, but HIP 11915 is one of the most promising candidates so far to host a planetary system similar to our own.

This research was presented in a paper entitled “The Solar Twin Planet Search II. A Jupiter twin around a solar twin”, by M. Bedell et al., to appear in the journal Astronomy and Astrophysics.


Astronomers Locate Oldest Known Solar Twin

An international team led by astronomers in Brazil has used ESO's Very Large Telescope to identify and study the oldest solar twin known to date.

Located 250 light-years from Earth, the star HIP 102152 is more like the Sun than any other solar twin -- except that it is nearly four billion years older. This older, but almost identical, twin gives us an unprecedented chance to see how the Sun will look when it ages. The new observations also provide an important first clear link between a star's age and its lithium content, and in addition suggest that HIP 102152 may be host to rocky terrestrial planets.

Astronomers have only been observing the Sun with telescopes for 400 years -- a tiny fraction of the Sun's age of 4.6 billion years. It is very hard to study the history and future evolution of our star, but we can do this by hunting for rare stars that are almost exactly like our own, but at different stages of their lives. Now astronomers have identified a star that is essentially an identical twin to our Sun, but 4 billion years older -- almost like seeing a real version of the twin paradox in action [1].


This image shows solar twin HIP 102152, a star located 250 light-years from Earth in the constellation of Capricornus (The Sea Goat). ESO/Digitized Sky Survey 2. Acknowledgement: Davide De Martin.

Jorge Melendez (Universidade de São Paulo, Brazil), the leader of the team and co-author of the new paper explains: "For decades, astronomers have been searching for solar twins in order to know our own life-giving Sun better. But very few have been found since the first one was discovered in 1997. We have now obtained superb-quality spectra from the VLT and can scrutinise solar twins with extreme precision, to answer the question of whether the Sun is special."

The team studied two solar twins [2] -- one that was thought to be younger than the Sun (18 Scorpii) and one that was expected to be older (HIP 102152). They used the UVES spectrograph on the Very Large Telescope (VLT) at ESO's Paranal Observatory to split up the light into its component colours so that the chemical composition and other properties of these stars could be studied in great detail.

They found that HIP 102152 in the constellation of Capricornus (The Sea Goat) is the oldest solar twin known to date. It is estimated to be 8.2 billion years old, compared to 4.6 billion years for our own Sun. On the other hand 18 Scorpii was confirmed to be younger than the Sun -- about 2.9 billion years old.

Studying the ancient solar twin HIP 102152 allows scientists to predict what may happen to our own Sun when it reaches that age, and they have already made one significant discovery. "One issue we wanted to address is whether or not the Sun is typical in composition," says Melendez. "Most importantly, why does it have such a strangely low lithium content?"

Lithium, the third element in the periodic table, was created in the Big Bang along with hydrogen and helium. Astronomers have pondered for years over why some stars appear to have less lithium than others. With the new observations of HIP 102152, astronomers have taken a big step towards solving this mystery by pinning down a strong correlation between a Sun-like star's age and its lithium content.

Our own Sun now has just 1% of the lithium content that was present in the material from which it formed. Examinations of younger solar twins have hinted that these younger siblings contain significantly larger amounts of lithium, but up to now scientists could not prove a clear correlation between age and lithium content [3].

TalaWanda Monroe (Universidade de São Paulo), the lead author on the new paper, concludes: "We have found that HIP 102152 has very low levels of lithium. This demonstrates clearly for the first time that older solar twins do indeed have less lithium than our own Sun or younger solar twins. We can now be certain that stars somehow destroy their lithium as they age, and that the Sun's lithium content appears to be normal for its age." [4]

A final twist in the story is that HIP 102152 has an unusual chemical composition pattern that is subtly different to most other solar twins, but similar to the Sun. They both show a deficiency of the elements that are abundant in meteorites and on Earth. This is a strong hint that HIP 102152 may host terrestrial rocky planets [5].

Notes
[1] Many people have heard of the twin paradox: one identical twin takes a space journey and comes back to Earth younger than their sibling. Although there is no time travelling involved here, we see two distinctly different ages for these two very similar stars -- snapshots of the Sun's life at different stages.

[2] Solar twins, solar analogues and solar-type stars are categories of stars according to their similarity to our own Sun. Solar twins are the most similar to our Sun, as they have very similar masses, temperatures, and chemical abundances. Solar twins are rare but the other classes, where the similarity is less precise, are much more common.

[3] Previous studies have indicated that a star's lithium content could also be affected if it hosts giant planets (eso0942, eso0118, Nature paper), although these results have been debated (ann1046).

[4] It is still unclear exactly how lithium is destroyed within the stars, although several processes have been proposed to transport lithium from the surface of a star into its deeper layers, where it is then destroyed.

[5] If a star contains less of the elements that we commonly find in rocky bodies, this indicates that it is likely to host rocky terrestrial planets because such planets lock up these elements as they form from a large disc surrounding the star. The suggestion that HIP 102152 may host such planets is further reinforced by the radial velocity monitoring of this star with ESO's HARPS spectrograph, which indicates that inside the star's habitable zone there are no giant planets. This would allow the existence of potential Earth-like planets around HIP 102152 in systems with giant planets existing close in to their star, the chances of finding terrestrial planets are much less as these small rocky bodies are disturbed and disrupted.

More information
This research was presented in a paper to appear in "High precision abundances of the old solar twin HIP 102152: insights on Li depletion from the oldest Sun", by TalaWanda Monroe et al. in the Astrophysical Journal Letters.

The team is composed of TalaWanda R. Monroe, Jorge Meléndez (Universidade de São Paulo, Brazil [USP]), Iván Ramírez (The University of Texas at Austin, USA), David Yong (Australian National University, Australia [ANU]), Maria Bergemann (Max Planck Institute for Astrophysics, Germany), Martin Asplund (ANU), Jacob Bean, Megan Bedell (University of Chicago, USA), Marcelo Tucci Maia (USP), Karin Lind (University of Cambridge, UK), Alan Alves-Brito, Luca Casagrande (ANU), Matthieu Castro, José-Dias do Nascimento (Universidade Federal do Rio Grande do Norte, Brazil), Michael Bazot (Centro de Astrofísica da Universidade de Porto, Portugal) and Fabrício C. Freitas (USP).

ESO is the foremost intergovernmental astronomy organisation in Europe and the world's most productive ground-based astronomical observatory by far. It is supported by 15 countries: Austria, Belgium, Brazil, the Czech Republic, Denmark, France, Finland, Germany, Italy, the Netherlands, Portugal, Spain, Sweden, Switzerland and the United Kingdom. ESO carries out an ambitious programme focused on the design, construction and operation of powerful ground-based observing facilities enabling astronomers to make important scientific discoveries. ESO also plays a leading role in promoting and organising cooperation in astronomical research. ESO operates three unique world-class observing sites in Chile: La Silla, Paranal and Chajnantor. At Paranal, ESO operates the Very Large Telescope, the world's most advanced visible-light astronomical observatory and two survey telescopes. VISTA works in the infrared and is the world's largest survey telescope and the VLT Survey Telescope is the largest telescope designed to exclusively survey the skies in visible light. ESO is the European partner of a revolutionary astronomical telescope ALMA, the largest astronomical project in existence. ESO is currently planning the 39-metre European Extremely Large optical/near-infrared Telescope, the E-ELT, which will become "the world's biggest eye on the sky".


Jupiter twin discovered around solar twin

An international group of astronomers has used the ESO 3.6-metre telescope to identify a planet just like Jupiter orbiting at the same distance from a Sun-like star, HIP 11915. According to current theories, the formation of Jupiter-mass planets plays an important role in shaping the architecture of planetary systems. The existence of a Jupiter-mass planet in a Jupiter-like orbit around a Sun-like star opens the possibility that the system of planets around this star may be similar to our own Solar System. HIP 11915 is about the same age as the Sun and, furthermore, its Sun-like composition suggests that there may also be rocky planets orbiting closer to the star.

So far, exoplanet surveys have been most sensitive to planetary systems that are populated in their inner regions by massive planets, down to a few times the mass of Earth [1]. This contrasts with our Solar System, where there are small rocky planets in the inner regions and gas giants like Jupiter farther out.

According to the most recent theories, the arrangement of our Solar System, so conducive to life, was made possible by the presence of Jupiter and the gravitational influence this gas giant exerted on the Solar System during its formative years. It would seem, therefore, that finding a Jupiter twin is an important milestone on the road to finding a planetary system that mirrors our own.

A Brazilian-led team has been targeting Sun-like stars in a bid to find planetary systems similar to our Solar System. The team has now uncovered a planet with a very similar mass to Jupiter [2], orbiting a Sun-like star, HIP 11915, at almost exactly the same distance as Jupiter. The new discovery was made using HARPS, one of the world's most precise planet-hunting instruments, mounted on the ESO 3.6-metre telescope at the La Silla Observatory in Chile.

Although many planets similar to Jupiter have been found [3] at a variety of distances from Sun-like stars, this newly discovered planet, in terms of both mass and distance from its host star, and in terms of the similarity between the host star and our Sun, is the most accurate analogue yet found for the Sun and Jupiter.

The planet's host, the solar twin HIP 11915, is not only similar in mass to the Sun, but is also about the same age. To further strengthen the similarities, the composition of the star is similar to the Sun's. The chemical signature of our Sun may be partly marked by the presence of rocky planets in the Solar System, hinting at the possibility of rocky planets also around HIP 11915.

According to Jorge Melendez, of the Universidade de São Paulo, Brazil, the leader of the team and co-author of the paper, "the quest for an Earth 2.0, and for a complete Solar System 2.0, is one of the most exciting endeavors in astronomy. We are thrilled to be part of this cutting-edge research, made possible by the observational facilities provided by ESO." [4]

Megan Bedell, from the University of Chicago and lead author of the paper, concludes: "After two decades of hunting for exoplanets, we are finally beginning to see long-period gas giant planets similar to those in our own Solar System thanks to the long-term stability of planet hunting instruments like HARPS. This discovery is, in every respect, an exciting sign that other solar systems may be out there waiting to be discovered."

Follow-up observations are needed to confirm and constrain the finding, but HIP 11915 is one of the most promising candidates so far to host a planetary system similar to our own.

[1] The current detection techniques are more sensitive to large or massive planets close to their host stars. Small and low-mass planets are mostly beyond our current capabilities. Giant planets that orbit far from their host star are also more difficult to detect. Consequently, many of the exoplanets we currently know are large and/or massive, and close to their stars.

[2] The planet was discovered by measuring the slight wobble it imposes on its host star while orbiting around it. As the inclination of the planet's orbit is not known, only a lower limit to its mass can be estimated. Note that the activity of the star, which is linked to the variations of its magnetic field, could possibly mimic the signal that is interpreted as the signature of the planet. The astronomers have performed all the known tests to investigate this possibility, but it is currently impossible to completely rule it out.

[3] An example of another Jupiter Twin is the one around HD 154345, described here.

[4] Since the signature of the Brazilian accession agreement in December 2010, Brazilian astronomer have had full access to the ESO observing facilities.


Astronomers discover Jupiter twin around solar twin

CHICAGO, July 15 (UPI) -- A team of international astronomers may have found a solar system just like ours, lending hope to researchers looking to find rocky Earth-like exoplanets in the habitable zone.

Using data collected by the European Southern Observatory's 3.6-meter telescope, researchers recently located a Jupiter-like gas planet orbiting a sun nearly identical to our own.

Not only is the faraway gas giant similar in mass, size and composition to Jupiter, it's also orbiting its host star at distance similar to the separation between Jupiter and our sun. The star around which the Jupiter lookalike orbits is called HIP 11915, and it is equally resemblant of our sun -- featuring a similar mass, age and composition.

While researchers have yet to identify other exoplanets, the newly located solar system is likely to reveal new planetary discoveries as researchers probe further.

It's the familiar composition of HIP 11915 -- and the fact that Jupiter's twin is farther away and not closer in -- that makes researchers believe this solar system may have evolved a cast of planets similar to our own, including inner orbit rocky planets like Earth.

Kepler and other exoplanet survey missions have located a variety of alien solar systems. But the ones that are easiest to spot -- and thus the ones that are spotted most frequently -- are systems with stars that host big bloated planets with tight orbits. These big planets block out their sun's light, making them easier for Earth-bound algorithms to pick them out and identify them as exoplanets, but these systems are less likely to host the Earth-like planets scientists are most interested in.

"The quest for an Earth 2.0, and for a complete Solar System 2.0, is one of the most exciting endeavors in astronomy," Jorge Melendez, a researcher at the University of Sao Paulo and co-author of a new paper of the two twins, said in a press release. "We are thrilled to be part of this cutting-edge research, made possible by the observational facilities provided by ESO."

"After two decades of hunting for exoplanets, we are finally beginning to see long-period gas giant planets similar to those in our own solar system thanks to the long-term stability of planet-hunting instruments like HARPS," the High Accuracy Radial velocity Planet Searcher, added Megan Bedell, an astronomer at the University of Chicago and lead author of the new paper, soon to be published in the journal Astronomy & Astrophysics.

"This discovery is, in every respect, an exciting sign that other solar systems may be out there waiting to be discovered," she concluded.


Jupiter twin discovered around solar twin

So far, exoplanet surveys have been most sensitive to planetary systems that are populated in their inner regions by massive planets, down to a few times the mass of the Earth [1]. This contrasts with our Solar System, where there are small rocky planets in the inner regions and gas giants like Jupiter farther out.

According to the most recent theories, the arrangement of our Solar System, so conducive to life, was made possible by the presence of Jupiter and the gravitational influence this gas giant exerted on the Solar System during its formative years. It would seem, therefore, that finding a Jupiter twin is an important milestone on the road to finding a planetary system that mirrors our own.

A Brazilian-led team has been targeting Sun-like stars in a bid to find planetary systems similar to our Solar System. The team has now uncovered a planet with a very similar mass to Jupiter [2], orbiting a Sun-like star, HIP 11915, at almost exactly the same distance as Jupiter. The new discovery was made using HARPS, one of the world's most precise planet-hunting instruments, mounted on the ESO 3.6-metre telescope at the La Silla Observatory in Chile.

Although many planets similar to Jupiter have been found [3] at a variety of distances from Sun-like stars, this newly discovered planet, in terms of both mass and distance from its host star, and in terms of the similarity between the host star and our Sun, is the most accurate analogue yet found for the Sun and Jupiter.

The planet's host, the solar twin HIP 11915, is not only similar inmass to the Sun, but is also about the same age. To further strengthen the similarities, the composition of the star is similar to the Sun's. The chemical signature of our Sun may be partly marked by the presence of rocky planets in the Solar System, hinting at the possibility of rocky planets also around HIP 11915.

According to Jorge Melendez, of the Universidade de São Paulo, Brazil, the leader of the team and co-author of the paper, "the quest for an Earth 2.0, and for a complete Solar System 2.0, is one of the most exciting endeavors in astronomy. We are thrilled to be part of this cutting-edge research, made possible by the observational facilities provided by ESO." [4]

Megan Bedell, from the University of Chicago and lead author of the paper, concludes: "After two decades of hunting for exoplanets, we are finally beginning to see long-period gas giant planets similar to those in our own Solar System thanks to the long-term stability of planet hunting instruments like HARPS. This discovery is, in every respect, an exciting sign that other solar systems may be out there waiting to be discovered."

Follow-up observations are needed to confirm and constrain the finding, but HIP 11915 is one of the most promising candidates so far to host a planetary system similar to our own.

[1] The current detection techniques are more sensitive to large or massive planets close to their host stars. Small and low-mass planets are mostly beyond our current capabilities. Giant planets that orbit far from their host star are also more difficult to detect. Consequently, many of the exoplanets we currently know are large and/or massive, and close to their stars.

[2] The planet was discovered by measuring the slight wobble it imposes on its host star while orbiting around it. As the inclination of the planet's orbit is not known, only a lower limit to its mass can be estimated. Note that the activity of the star, which is linked to the variations of its magnetic field, could possibly mimic the signal that is interpreted as the signature of the planet. The astronomers have performed all the known tests to investigate this possibility, but it is currently impossible to completely rule it out.

[3] An example of another Jupiter Twin is the one around HD 154345, described here: http://iopscience. iop. org/ 1538-4357/ 683/ 1/ L63/ pdf/ 587461. pdf .

[4] Since the signature of the Brazilian accession agreement in December 2010, Brazilian astronomer have had full access to the ESO observing facilities.

This research was presented in a paper entitled "The Solar Twin Planet Search II. A Jupiter twin around a solar twin", by M. Bedell et al., to appear in the journal Astronomy and Astrophysics.

The team is composed of M. Bedell (Department of Astronomy and Astrophysics, University of Chicago, Chicago, Illinois, USA Visiting Researcher at the Departamento de Astronomia do IAG/USP, Universidade de São Paulo, São Paulo, Brazil), J. Meléndez (Universidade de São Paulo, São Paulo, Brazil), J. L. Bean (Department of Astronomy and Astrophysics, University of Chicago), I. Ramírez (McDonald Observatory and Department of Astronomy, University of Texas, Austin, Texas, USA), M. Asplund (Research School of Astronomy and Astrophysics, The Australian National University, Weston, Australia), A. Alves-Brito (Instituto de Fisica, Universidade Federal do Rio Grande do Sul, Porto Alegre, Rio Grande do Sul, Brazil), L. Casagrande (Research School of Astronomy and Astrophysics, Australia), S. Dreizler (Institut für Astrophysik, University of Göttingen, Germany), T. Monroe (Universidade de São Paulo, Brazil), L. Spina (Universidade de São Paulo, Brazil) and M. Tucci Maia (Universidade de São Paulo, Brazil).

ESO is the foremost intergovernmental astronomy organisation in Europe and the world's most productive ground-based astronomical observatory by far. It is supported by 16 countries: Austria, Belgium, Brazil, the Czech Republic, Denmark, France, Finland, Germany, Italy, the Netherlands, Poland, Portugal, Spain, Sweden, Switzerland and the United Kingdom, along with the host state of Chile. ESO carries out an ambitious programme focused on the design, construction and operation of powerful ground-based observing facilities enabling astronomers to make important scientific discoveries. ESO also plays a leading role in promoting and organising cooperation in astronomical research. ESO operates three unique world-class observing sites in Chile: La Silla, Paranal and Chajnantor. At Paranal, ESO operates the Very Large Telescope, the world's most advanced visible-light astronomical observatory and two survey telescopes. VISTA works in the infrared and is the world's largest survey telescope and the VLT Survey Telescope is the largest telescope designed to exclusively survey the skies in visible light. ESO is a major partner in ALMA, the largest astronomical project in existence. And on Cerro Armazones, close to Paranal, ESO is building the 39-metre European Extremely Large Telescope, the E-ELT, which will become "the world's biggest eye on the sky".

Megan Bedell
University of ChicagoUSA
Tel: +1 518 488 9348
Email: [email protected]

Jorge Meléndez
Universidade de São PauloBrazil
Tel: +55 11 3091 2840
Email: [email protected]

Richard Hook
ESO Public Information Officer
Garching bei München, Germany
Tel: +49 89 3200 6655
Cell: +49 151 1537 3591
Email: [email protected]

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Contents

Defining the three categories by their similarity to the Sun reflects the evolution of astronomical observational techniques. Originally, solar-type was the closest that similarity to the Sun could be defined. Later, more precise measurement techniques and improved observatories allowed for greater precision of key details like temperature, enabling the creation of a solar analog category for stars that were particularly similar to the Sun. Later still, continued improvements in precision allowed for the creation of a solar-twin category for near-perfect matches.

Similarity to the Sun allows for checking derived quantities—such as temperature, which is derived from the color index—against the Sun, the only star whose temperature is confidently known. For stars that are not similar to the Sun, this cross-checking cannot be done. [1]

Solar-type

These stars are broadly similar to the Sun. They are main-sequence stars with a B−V color between 0.48 and 0.80, the Sun having a B−V color of 0.65. Alternatively, a definition based on spectral type can be used, such as F8V through K2V, which would correspond to B−V color of 0.50 to 1.00. [1] This definition fits approximately 10% of stars, [3] so a list of solar-type stars would be quite extensive. [4]

Solar-type stars show highly correlated behavior between their rotation rates and their chromospheric activity (e.g. Calcium H & K line emission) and coronal activity (e.g. X-ray emission) [5] Because solar-type stars spin down during their main-sequence lifetimes due to magnetic braking, these correlations allow rough ages to be derived. Mamajek & Hillenbrand (2008) [6] have estimated the ages for the 108 solar-type (F8V–K2V) main-sequence stars within 52 light-years (16 parsecs) of the Sun based on their chromospheric activity (as measured via Ca, H, and K emission lines).

The following table shows a sample of solar-type stars within 50 light years that nearly satisfy the criteria for solar analogs (B−V color between 0.48 and 0.80), based on current measurements (the Sun is listed for comparison):

Solar analog

These stars are photometrically similar to the Sun, having the following qualities: [1]

  • Temperature within 500 K from that of the Sun (5278 to 6278 K)
  • Metallicity of 50�% (± 0.3 dex) of that of the Sun, meaning the star's protoplanetary disk would have had similar amounts of dust from which planets could form
  • No close companion (orbital period of ten days or less), because such a companion stimulates stellar activity

Solar analogs not meeting the stricter solar twin criteria include, within 50 light years and in order of increasing distance (The Sun is listed for comparison.):

Identifier J2000 coordinates [7] Distance [7]
(ly)
Stellar
class [7]
Temperature
(K)
Metallicity
(dex)
Age
(Gyr)
Notes
Right ascension Declination
Sun 0.0000158G2V5,778+0.004.6 [8]
Sigma Draconis   [27] 19 h 32 m 21.6 s +69 °   39 ′   40 ″ 18.8G9–K0 V5,297𕒴.204.7 [28]
Beta Canum Venaticorum   [29] 12 h 33 m 44.5 s +41 °   21 ′   27 ″ 27.4G0V5,930𕒴.306.0 [17]
61 Virginis   [30] 13 h 18 m 24.3 s 󔼚 °   18 ′   40 ″ 27.8G5V5,558𕒴.026.3 [19]
Zeta Tucanae   [31] 00 h 20 m 04.3 s 󈞬 °   52 ′   29 ″ 28.0F9.5V5,956𕒴.142.5 [15]
Beta Comae Berenices   [32] 13 h 11 m 52.4 s +27 °   52 ′   41 ″ 29.8G0V5,970𕒴.062.0 [17]
61 Ursae Majoris   [33] 11 h 41 m 03.0 s +34 °   12 ′   06 ″ 31.1G8V5,483𕒴.121.0 [17]
HR 511   [34] 01 h 47 m 44.8 s +63 °   51 ′   09 ″ 32.8K0V5,333+0.053.0 [17]
Alpha Mensae   [35] 06 h 10 m 14.5 s 󈞶 °   45 ′   11 ″ 33.1G5V5,594+0.105.4 [15]
HD 69830   [36] 08 h 18 m 23.9 s 󔼔 °   37 ′   56 ″ 40.6K0V5,410𕒴.0310.6 [15]
HD 10307   [37] 01 h 41 m 47.1 s +42 °   36 ′   48 ″ 41.2G1.5V5,848𕒴.057.0 [17]
HD 147513   [38] 16 h 24 m 01.3 s 󔼯 °   11 ′   35 ″ 42.0G1V5,858+0.030.4 [19]
58 Eridani   [39] 04 h 47 m 36.3 s 󔼘 °   56 ′   04 ″ 43.3G3V5,868+0.020.6 [15]
47 Ursae Majoris   [40] 10 h 59 m 28.0 s +40 °   25 ′   49 ″ 45.9G1V5,954+0.066.0 [15]
Psi Serpentis   [41] 15 h 44 m 01.8 s +02 °   30 ′   54.6 ″ 47.8G5V5,6830.043.2 [42]
HD 84117   [43] 09 h 42 m 14.4 s 󈞃 °   54 ′   56 ″ 48.5F8V6,167𕒴.033.1 [15]
HD 4391   [44] 00 h 45 m 45.6 s 󈞛 °   33 ′   07 ″ 48.6G3V5,878𕒴.031.2 [15]
20 Leonis Minoris   [45] 10 h 01 m 00.7 s +31 °   55 ′   25 ″ 49.1G3V5,741+0.206.5 [17]
Nu Phoenicis   [46] 01 h 15 m 11.1 s 󈞙 °   31 ′   54 ″ 49.3F8V6,140+0.185.7 [15]
51 Pegasi   [47] 22 h 57 m 28.0 s +20 °   46 ′   08 ″ 50.9G2.5IVa5,804+0.207.0 [15]

Solar twin

To date no solar twin that exactly matches the Sun has been found. However, there are some stars that come very close to being identical to that of the Sun, and are such considered solar twins by members of the astronomical community. An exact solar twin would be a G2V star with a 5,778K surface temperature, be 4.6 billion years old, with the correct metallicity and a 0.1% solar luminosity variation. [48] Stars with an age of 4.6 billion years are at the most stable state. Proper metallicity and size are also very important to low luminosity variation. [49] [50] [51]

Morgan-Keenan spectral classification of stars. Most common star type in the universe are M-dwarfs, 76%. The sun is a 4.6 billion year-old G-class (G2V) star and is more massive than 95% of all stars. Only 7.6% are G-class stars

The stars below are more similar to the Sun and having the following qualities: [1]

  • Temperature within 50 K from that of the Sun (5728 to 5828 K) [lower-alpha 1](within 10 K of sun (5768� K)).
  • Metallicity of 89�% (± 0.05 dex) of that of the Sun, meaning the star's proplyd would have had almost exactly the same amount of dust for planetary formation
  • No stellar companion, because the Sun itself is a solitary star
  • An age within 1 billion years from that of the Sun (3.6 to 5.6 Ga)

The following are the known stars that come closest to satisfying the criteria for a solar twin. The Sun is listed for comparison. Highlighted boxes are out of range for a solar twin. The star may have been noted as solar twin in the past, but are more of a solar analog.

Some other stars are sometimes mentioned as solar-twin candidates such as: Beta Canum Venaticorum however it has too low metallicities (𕒴.21) for solar twin. 16 Cygni B is sometimes noted as twin, but is part of a triple star system and is very old for a solar twin at 6.8 Ga. Two solar sibling candidates (similar age, metallicity, and kinematics) are Gaia DR2 1927143514955658880 and 1966383465746413568. [79]


Happy (or is it Merry?) Aphelion This Friday

This 4 th of July weekend brings us one more reason to celebrate. On July 5 th at approximately 11:00 AM EDT/15:00 UT, our fair planet Earth reaches aphelion, or its farthest point from the Sun at 1.0167 Astronomical Units (A.U.s) or 152,096,000 kilometres distant.

Though it may not seem it to northern hemisphere residents sizzling in the summer heat, we’re currently 3.3% farther from the Sun than our 147,098,290 kilometre (0.9833 A.U.) approach made in early January.

We thought it would be a fun project to capture this change. A common cry heard from denier circles as to scientific facts is “yeah, but have you ever SEEN it?” and in the case of the variation in distance between the Sun and the Earth from aphelion to perihelion, we can report that we have!

We typically observe the Sun in white light and hydrogen alpha using a standard rig and a Coronado Personal Solar Telescope on every clear day. We have two filtered rigs for white light- a glass Orion filter for our 8-inch Schmidt-Cassegrain, and a homemade Baader solar filter for our DSLR. We prefer the DSLR rig for ease of deployment. We’ve described in a previous post how to make a safe and effective solar observing rig using Baader solar film.

Our primary solar imaging rig. A Nikon D60 DSLR with a 400mm lens + a 2x teleconverter and Baader solar filter. Very easy to employ!

We’ve been imaging the Sun daily for a few years as part of our effort to make a home-brewed “solar rotation and activity movie” of the entire solar cycle. We recently realized that we’ve imaged Sol very near aphelion and perihelion on previous years with this same fixed rig, and decided to check and see if we caught the apparent size variation of our nearest star. And sure enough, comparing the sizes of the two disks revealed a tiny but consistent variation.

It’s a common misconception that the seasons are due to our distance from the Sun. The insolation due to the 23.4° tilt of the rotational axis of the Earth is the dominant driving factor behind the seasons. (Don’t they still teach this in grade school? You’d be surprised at the things I’ve heard!) In the current epoch, a January perihelion and a July aphelion results in milder climatic summers in the northern hemisphere and more severe summers in the southern. The current difference in solar isolation between hemispheres due to eccentricity of Earth’s orbit is 6.8%.

The orbit of the Earth also currently has one of the lowest eccentricities (how far it deviates for circular) of the planets at 0.0167, or 1.67%. Only Neptune (1%) and Venus (0.68%) are “more circular.”

The orbital eccentricity of the Earth also oscillates over a 413,000 year period between 5.8% (about the same as Saturn) down to 0.5%. We’re currently at the low end of the scale, just below the mean value of 2.8%.

Variation in eccentricity is also coupled with other factors, such as the change in axial obliquity the precession of the line of apsides and the equinoxes to result in what are known as Milankovitch cycles. These variations in extremes play a role in the riddle of climate over hundreds of thousands of years. Climate change deniers like to point out that there are large natural cycles in the records, and they’re right – but in the wrong direction. Note that looking solely at variations in the climate due to Milankovitch cycles, we should be in a cooling trend right now. Against this backdrop, the signal of anthropogenic climate forcing and global dimming of albedo (which also masks warming via cloud cover and reflectivity) becomes even more ominous.

Aphelion can presently fall between July 2 nd at 20:00 UT (as it did last in 1960) and July 7 th at 00:00 UT as it last did on 2007. The seemingly random variation is due to the position of the Earth with respect to the barycenter of the Earth-Moon system near the time of aphelion. The once every four year reset of the leap year (with the exception of the year 2000!) also plays a lesser role.

Perihelion and aphelion vs the solstices and equinoxes, an exaggerated view. (Wikimedia Commons image under a 3.0 Unported Attribution-Share Alike license. Author Gothika/Doudoudou).

I love observing the Sun any time of year, as its face is constantly changing from day-to-day. There’s also no worrying about light pollution in the solar observing world, though we’ve noticed turbulence aloft (in the form of bad seeing) is an issue later in the day, especially in the summertime. The rotational axis of the Sun is also tipped by about 7.25° relative to the ecliptic, and will present its north pole at maximum tilt towards us on September 8th. And yes, it does seem strange to think in terms of “the north pole of the Sun…”

We’re also approaching the solar maximum through the 2013-2014 time frame, another reason to break out those solar scopes. This current Solar Cycle #24 has been off to a sputtering start, with the Sun active one week, and quiet the next. The last 2009 minimum was the quietest in a century, and there’s speculation that Cycle #25 may be missing all together.

And yes, the Moon also varies in its apparent size throughout its orbit as well, as hyped during last month’s perigee or Super Moon. Keep those posts handy- we’ve got one more Super Moon to endure this month on July 22 nd . The New Moon on July 8 th at 7:15UT/3:15 AM EDT will occur just 30 hours after apogee, and will hence be the “smallest New Moon” of 2013, with a lot less fanfare. Observers worldwide also have a shot at catching the slender crescent Moon on the evening of July 9 th . This lunation and the sighting of the crescent Moon also marks the start of the month of Ramadan on the Muslim calendar.

Be sure to observe the aphelion Sun (with proper protection of course!) It would be uber-cool to see a stitched together animation of the Sun “growing & shrinking” from aphelion to perihelion and back. We could also use a hip Internet-ready meme for the perihelion & aphelion Sun- perhaps a “MiniSol?” A recent pun from Dr Marco Langbroek laid claim to the moniker of “#SuperSun” in time for next January’s perihelion

Could a new trend be afoot?


Jupiter twin discovered around solar twin

An international group of astronomers has used the ESO 3.6-metre telescope to identify a planet just like Jupiter orbiting at the same distance from a Sun-like star, HIP 11915. According to current theories, the formation of Jupiter-mass planets plays an important role in shaping the architecture of planetary systems. The existence of a Jupiter-mass planet in a Jupiter-like orbit around a Sun-like star opens the possibility that the system of planets around this star may be similar to our own Solar System. HIP 11915 is about the same age as the Sun and, furthermore, its Sun-like composition suggests that there may also be rocky planets orbiting closer to the star. ESO/M. Kornmesser

So far, exoplanet surveys have been most sensitive to planetary systems that are populated in their inner regions by massive planets, down to a few times the mass of the Earth. This contrasts with our Solar System, where there are small rocky planets in the inner regions and gas giants like Jupiter farther out.

According to the most recent theories, the arrangement of our Solar System, so conducive to life, was made possible by the presence of Jupiter and the gravitational influence this gas giant exerted on the Solar System during its formative years. It would seem, therefore, that finding a Jupiter twin is an important milestone on the road to finding a planetary system that mirrors our own.

A Brazilian-led team has been targeting Sun-like stars in a bid to find planetary systems similar to our Solar System. The team has now uncovered a planet with a very similar mass to Jupiter, orbiting a Sun-like star, HIP 11915, at almost exactly the same distance as Jupiter. The new discovery was made using HARPS, one of the world’s most precise planet-hunting instruments, mounted on the ESO 3.6-metre telescope at the La Silla Observatory in Chile.

Although many planets similar to Jupiter have been found at a variety of distances from Sun-like stars, this newly discovered planet, in terms of both mass and distance from its host star, and in terms of the similarity between the host star and our Sun, is the most accurate analogue yet found for the Sun and Jupiter.

The planet’s host, the solar twin HIP 11915, is not only similar inmass to the Sun, but is also about the same age. To further strengthen the similarities, the composition of the star is similar to the Sun’s. The chemical signature of our Sun may be partly marked by the presence of rocky planets in the Solar System, hinting at the possibility of rocky planets also around HIP 11915.

According to Jorge Melendez, of the Universidade de São Paulo, Brazil, the leader of the team and co-author of the paper, “the quest for an Earth 2.0, and for a complete Solar System 2.0, is one of the most exciting endeavors in astronomy. We are thrilled to be part of this cutting-edge research, made possible by the observational facilities provided by ESO.”

Megan Bedell, from the University of Chicago and lead author of the paper, concludes: “After two decades of hunting for exoplanets, we are finally beginning to see long-period gas giant planets similar to those in our own Solar System thanks to the long-term stability of planet hunting instruments like HARPS. This discovery is, in every respect, an exciting sign that other solar systems may be out there waiting to be discovered.”

Follow-up observations are needed to confirm and constrain the finding, but HIP 11915 is one of the most promising candidates so far to host a planetary system similar to our own.


Watch the video: HIP 11915b - Jupiter Twin Orbiting Solar Twin (June 2022).