Artist's concept of NASA's Spitzer Space Telescope surrounded by examples of exoplanets it has looked at. Credit: NASA/JPL-Caltech
After NASA recommended in May that Spitzer space telescope officials send in a revised budget or face possible termination of operations, in a turnaround, the agency’s science mission directorate has now agreed to extend the mission for another two years.
The news broke on Twitter yesterday when the NASA Spitzer account shared the news. An update posted on its website said the decision is “subject to the availability of Congressional appropriations in FY [fiscal year] 2015”, but added that there will soon be a call out for observing time in that period.
Previously, NASA informed Spitzer officials that due to “constrained budget conditions” that their initial request to extend operations past fiscal 2015 was not approved, in line with recommendations from the NASA senior astrophysics review. While the mission was not terminated at that time, officials were asked to “respond with a request for a budget augmentation to conduct continued operations with reduced operations costs.”
The mission was being reviewed at the same time as other astrophysics missions, such as the Kepler planet-hunting space telescope that was asking for (and received) a new mission that would allow it to do useful science despite two busted reaction wheels, or pointing devices. The review said Spitzer was the most expensive of the missions reviewed, and that the telescope’s abilities were “significantly reduced” after it ran out of coolant in 2009.
The bow shock of Zeta Ophiuchi, another runaway star observed by Spitzer (NASA/JPL-Caltech)
In an update on the Spitzer website, officials shared more details but did not say if the budget had been reformulated in response to NASA’s suggestion.
We are very happy to report that Spitzer operations have been extended by the NASA Science Mission Directorate for two more years! The letter of direction states: “The Science Mission Directorate has made the decision to extend Spitzer operations for the next two years. The Spitzer observatory is an important resource for on-going infrared observations for research programs across the Science Mission Directorate, and, subject to the availability of Congressional appropriations in FY 2015, it will be continued. Both the Astrophysics and the Planetary Science Divisions have requested observing time commitments for FY 2015, and both Divisions have committed funding to support their observations.” We are working hard to get a call for observing proposals issued by the end of July. And thank you to all the people at NASA Headquarters and in the community that have worked so hard to support science with Spitzer.
Interior of Jupiter. Image Credit: NASA / R. J. Hall
It’s likely that Jupiter-like planets’ origins root back to either the rapid collapse of a dense cloud or small rocky cores that glom together until the body is massive enough to accrete a gaseous envelope.
Although these two competing theories are both viable, astronomers have, for the first time, seen the latter “core accretion” theory in action. By studying the exoplanet’s host star they’ve shed light on the composition of the planet’s rocky core.
“Our results show that the formation of giant planets, as well as terrestrial planets like our own Earth, leaves subtle signatures in stellar atmospheres”, said lead author and PhD student Marcelo Tucci Maia from University of São Paulo, Brazil, in a press release.
Maia and colleagues pointed the 3.5-meter Canada-France-Hawaii Telescope toward the constellation Cygnus, in order to take a closer look at two Sun-like stars in the distant 16 Cyg triple-star system. Both stars, having formed together from the same gaseous disk over 10 billion years ago and having reached the same mass, are nearly solar twins.
But only one star, 16 Cygni B, hosts a giant planet. By decomposing the light from the two stars into their wavelengths and looking at the difference between the two stars, the team was able to detect signatures left from the planet formation process on 16 Cygni B.
It’s the perfect laboratory to study the formation of giant planets.
Difference in chemical composition between the stars 16 Cyg A and 16 Cyg B, versus the condensation temperature of the elements in the proto-planetary nebula. Image Credit: M. Tucci Maia, J. Meléndez, I. Ramírez.
Maia and colleagues found that the star 16 Cygni A is enhanced in all chemical elements relative to 16 Cygni B. Hence, the metals removed from 16 Cygni B were most likely removed from the protoplanetary disk in order to form the planet.
On top of the overall deficiency in all elements, 16 Cygni B has an added deficiency in the refractory elements — those with high condensation temperatures that form dust grains more easily — such as iron, aluminum, nickel, magnesium, scandium, and silicon. This helps verify what astronomers have expected all along: rocky cores are rich in refractory elements.
The team was able to decipher that these missing elements likely created a rocky core with a mass of about 1.5 to 6 Earth masses, which is similar to the estimate of Jupiter’s core.
“16 Cyg is a remarkable system, but certainly not unique,” said coauthor Ivan Ramírez from the University of Texas. “It is special because it is nearby; however, there are many other binary stars with twin components on which this experiment could be performed. This could help us find planet-host stars in binaries in a much more straightforward manner compared to all other planet-finding techniques we have available today.”
The results were accepted for publication in The Astrophysical Journal Letters and are available online.
Dazzlimg Sirius, with its white dwarf companion to the lower left. Credit: NASA, ESA, H. Bond (STScI) and M. Barstow (University of Leicester).
Looking for something off beat to observe? Some examples of curious astronomical objects lie within the reach of the dedicated amateur armed with a moderate-sized backyard telescope. With a little skill and persistence, you just might be able to track down a white dwarf star. Unlike splashy nebulae or globular clusters, a white dwarf star will just appear as a speck, a tiny dot in the field of view of your telescope’s eyepiece. But just as in the case of observing other exotic objects such as red giants and quasars, part of the thrill of tracking down these astrophysical beasties is in knowing just what it is that you’re seeing. Heck, many amateur astronomers fail to realize that any white dwarf stars are within range of their instruments and have never tracked one down.
The astrophysical nature of white dwarf stars was first uncovered in the early 20th century. Most of the early white dwarf stars discovered were companions in binary star systems and this allowed astronomers to gauge their mass by following the orbital motion of such pairs over time. Soon, astronomers realized that they were looking at something peculiar, a new type of compact but massive stellar object that stubbornly refused to be pigeon-holed along the main sequence of the freshly conceived Hertzsprung-Russell diagram.
Today, we know that white dwarf stars are the remnants of stars which have long since passed the Red Giant stage. We say that a white dwarf is a degenerate star, and no, this not a commentary on its moral state. The Chandrasekhar limit gives us an upper limit in size for a white dwarf at about 1.4 solar masses, beyond which electron degeneracy pressure can no longer act against the inward pull of gravity. Our Sun will one day become a white dwarf, over 6 billion years from now. Think of cramming the mass of our star into the volume of the Earth and you have some idea just how dense a white dwarf is: a cubic centimetre of white dwarf weighs 250 about tons, and two cup fulls of white dwarf would weigh more than a Nimitz-class aircraft carrier.
Think of a white dwarf as a cooling ember of a star long past its hydrogen fusing prime. And white dwarfs will cool down to infrared radiating black dwarfs over trillions of years, far longer than the present 13.7 billion year age of the universe. In fact, the age of white dwarfs currently observed is one on the underpinning tenets of modern Big Bang cosmology.
All amazing stuff. In any event, here is a baker’s half dozen of white dwarf stars that you can find with a telescope tonight. A more extensive list of the nearest white dwarfs to the Earth can be found on Sol Station.
The orbit of Sirius B. Wikimedia Commons image in the Public Domain.
Sirius B: This is the nearest white dwarf to the Earth at 8.6 light years distant. Shining at magnitude +8.5, Sirius B would be a cinch to see, if only dazzling Sirius A — the brightest star in our sky at magnitude -1.5 — were not nearby. Sirius B orbits its primary once every 50 years and will reach a maximum separation of 11.5” from its primary in 2025, a prime time to cross it off of your life list in the coming decade. Blocking the primary just out of the field of view, or using an occulting bar eyepiece is key to finding Sirius B.
Sirius B was discovered by American telescope maker Alvan Graham Clark in 1862. The Dogon people of Mali also have some curious myths surrounding the star Sirius.
Constellation: Canis Major
Right Ascension: 6 Hours 45’
Declination: -16° 43’
The apparent orbit of Procyon B through 2039. Graphic created by the author.
Procyon B: Located 11.5 light years distant, Procyon B was discovered in 1896 by John Martin Schaeberle from the Lick observatory. Shining at magnitude +10.7, the chief difficultly with spotting this white dwarf, as with Sirius B, is that it has a companion about 10 magnitudes – that’s 10,000 times brighter – nearby just 4.3” away.
Constellation: Canis Minor
Right Ascension: 7 hours 39’
Declination: +5 13’
The location of GJ 440 (HIP 57367) in the southern sky. Credit: Starry Night Education Software.
-LP145-141: Also known as GJ 440, LP145-141 is one of the best southern hemisphere white dwarf stars on the list. LP145-141 is a solitary white dwarf shining at magnitude +11.5. Located 15 light years distant, LP145-141 is thought to be a member of the nearby Wolf 219 Moving Group of stars.
Constellation: Musca
Right Ascension: 11 Hours 46’
Declination: -64° 50’
The location of Van Maanen’s Star in the constellation Pisces. Credit: Stellarium
-Van Maanen’s Star: Shining at magnitude +12.4 and located 14.1 light years distant, Van Maanen’s star is the closest solitary white dwarf to Earth and the best example of a white dwarf for small telescopes. Discovered by Ariaan van Maanen in 1917, Van Maanen’s Star also has a very high proper motion of 3” per year.
Constellation: Pisces
Right Ascension: 00 Hours 49’
Declination: 05° 23’
The 40 Omicron Eridani system. Image by Author
-40 Omicron Eridani B: This is a great one to track down. The triple system of 40 Omicron Eridani b contains a fine example of a red and white dwarf orbiting a main sequence star. Located 16.5 light years distant and shining at magnitude +9.5, Omicron Eridani was the first white dwarf star discovered in 1783 by Sir William Herschel, although its true nature wasn’t deduced until 1910. Omicron Eridani B is currently 82” from its primary, an easy split.
Constellation: Eridanus
Right Ascension: 4 Hours 15’
Declination: 7° 39’
-Stein 2051: Rounding off the list and located just over 18 light years distant, Stein 2051 is another example of a red dwarf/white dwarf pair. Stein 2051 b shines at a similar brightest to Van Maanen’s star at magnitude +12.4.
Constellation: Camelopardalis
Right Ascension: 04 Hours 31’
Declination: +58° 59’
Let us know about your trials and triumphs in hunting down these fascinating objects!
Comet 67P/C-G photographed on July 14, 2014 from a distance of approximately 12 000 km.
Credits: ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA
I thought the photos earlier this week were amazing. This little movie, made of 36 ‘smoothed’ or interpolated images of Comet 67P/Churyumov-Gerasimenko, takes it to the next level, showing the comet’s complex shape even more clearly as Rosetta nudges ever closer to its target. Some have likened it to a duck, a boot and even a baby’s foot. The original photos used for the animation were more pixelated, but a technique known as “sub-sampling by interpolation” was used to smooth out the pixels for a more natural look. Be aware that because of processing, 67P C-G appears smoother than it might be. While the surface looks textured, including what appears to be a small crater atop the duck’s head, we have to be careful at this stage not to over-interpret – some of the details are artifacts.
Raw pixelated image of the comet (left) and after smoothing. Credit: ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA
No one knows yet how such an unusual shape formed in the first place. Possibly the comet is a ‘contact binary’ made of two separate comets or two parts of larger, shattered comet that stuck together during a low-velocity collision. This may have happened more 4 billion years ago when the icy building blocks of the planets and comets were numerous and collisions far more frequent than they are today. Contact binaries aren’t uncommon; we see them in asteroids and comets alike.
* The comet may have once been a more spherical object but after many trips around the sun developed an asymmetrical shape from ice vaporization and outgassing.
* A near-catastrophic impact blasted away a huge chunk of comet ice.
* The strong gravitational pull experienced during a close pass of a large planet like Jupiter or Saturn may have pulled it into an irregular shape.
* A large outburst could have weakened a region on the comet’s surface that later crumbled away.
Detailed view of the likely contact binary asteroid 25143 Itokawa visited by the Japanese spacecraft Hayabusa in 2005. Credit: JAXA
“We will need to perform detailed analyses and modelling of the shape of the comet to determine how best we can fly around such a uniquely shaped body, taking into account flight control and astrodynamics, the science requirements of the mission, and the landing-related elements like landing site analysis and lander-to-orbiter visibility,” said Rosetta Mission Manager Fred Jansen. ” But with fewer than 10,000 km to go before the August 6th rendezvous, our open questions will soon be answered.”
In the meantime, keep the photos and movies coming. We can’t get enough.
Artist's conception of NASA's Space Launch System with Orion crewed deep space capsule. Credit: NASA
In three years, NASA is planning to light the fuse on a huge rocket designed to bring humans further out into the solar system.
We usually talk about SLS here in the context of the astronauts it will carry inside the Orion spacecraft, which will have its own test flight later in 2014. But today, NASA advertised a possible other use for the rocket: trying to find life beyond Earth.
At a symposium in Washington on the search for life, NASA associate administrator John Grunsfeld said SLS could serve two major functions: launching bigger telescopes, and sending a mission on an express route to Jupiter’s moon Europa.
The James Webb Space Telescope, with a mirror of 6.5 meters (21 feet), will in part search for exoplanets after its launch in 2018. Next-generation telescopes of 10 to 20 meters (33 to 66 feet) could pick out more, if SLS could bring them up into space.
“This will be a multi-generational search,” said Sara Seager, a planetary scientist and physicist at the Massachusetts Institute of Technology. She added that the big challenge is trying to distinguish a planet like Earth from the light of its parent star; the difference between the two is a magnitude of 10 billion. “Our Earth is actually extremely hard to find,” she said.
Much like our solar system, Kepler-62 is home to two habitable zone worlds. The small shining object seen to the right of Kepler-62f is Kepler-62e. Orbiting on the inner edge of the habitable zone, Kepler-62e is roughly 60 percent larger than Earth. Image credit: NASA Ames/JPL-Caltech.
While the symposium was not talking much about life in the solar system, Europa is considered one of the top candidates due to the presence of a possible subsurface ocean beneath its ice. NASA is now seeking ideas for a mission to this moon, following news that water plumes were spotted spewing from the moon’s icy south pole. A mission to Europa would take seven years with the technology currently in NASA’s hands, but the SLS would be powerful enough to speed up the trip to only three years, Grunsfeld said.
And that’s not all that SLS could do. If it does bring astronauts deeper in space as NASA hopes it will, this opens up a range of destinations for them to go to. Usually NASA talks about this in terms of its human asteroid mission, an idea it has been working on and pitching for the past year to a skeptical, budget-conscious Congress.
But in passing, John Mather (NASA’s senior project scientist for Webb) said it’s possible astronauts could be sent to maintain the telescope. Webb is supposed to be parked in a Lagrange point (gravitationally stable location) in the exact opposite direction of the sun, almost a million miles away. It’s a big contrast to the Hubble Space Telescope, which was conveniently parked in low Earth orbit for astronauts to fix every so often with the space shuttle.
An Artist’s Conception of the James Webb Space Telescope. Credit: ESA.
While NASA works on the funding and design for larger telescope mirrors, Webb is one of the two new space telescopes it is focusing on in the search for life. Webb’s infrared eyes will be able to peer at solar systems being born, once it is launched in 2018. Complementary to that will be the Transiting Exoplanet Survey Satellite, which will fly in 2017 and examine planets that pass in front of their parent stars to find elements in their atmospheres.
The usual cautions apply when talking about this article: NASA is talking about several missions under development, and it is unclear yet what the success of SLS or any of these will be until they are battle-tested in space.
But what this discussion does show is the agency is trying to find many purposes for its next-generation rocket, and working to align it to astrophysics goals as well as its desire to send humans further out in the solar system.
Image of the sky where the radio burst FRB 121102 was found, in the constellation Auriga. You can see its location with a green circle. At left is supernova remnant S147 and at right, a star formation area called IC 410. Credit: Rogelio Bernal Andreo (DeepSkyColors.com)
Where are these radio bursts coming from? Astronomers have heard these signals from the sky several times, but always with the same telescope (Parkes Observatory in Australia). There was debate about whether these were coming from inside or outside the galaxy, or even from Earth itself (given only the one observatory was detecting them.)
A new study with a different telescope, the Arecibo Observatory in Puerto Rico, concludes that the bursts are from outside the galaxy. This is the first time one of these bursts have been found in the northern hemisphere of the sky.
“Our result is important because it eliminates any doubt that these radio bursts are truly of cosmic origin,” stated Victoria Kaspi, an astrophysics researcher at McGill University who participated in the research. “The radio waves show every sign of having come from far outside our galaxy – a really exciting prospect.”
Fast radio bursts are a flurry of radio waves that last a few thousandths of a second, and at any given minute there are only seven of these in the sky on average, according to the Max Planck Institute for Radio Astronomy. Their cause is unknown. They could be anything from black holes, to neutron stars coming together, to the magnetic field of pulsars (a type of neutron star) flaring up — or something else.
Arecibo Observatory in Puerto Rico. Credit: NAIC – Arecibo Observatory, a facility of the NSF
The pulse was found Nov. 2, 2012 in the constellation Auriga. Astronomers believe it is from quite far away from measuring its plasma dispersion, or the slowdown of radio waves as they crash into interstellar electrons. This particular source had triple the maximum dispersion than what would be found inside the galaxy, astronomers stated.
“The brightness and duration of this event, and the inferred rate at which these bursts occur, are all consistent with the properties of the bursts previously detected by the Parkes telescope in Australia,” stated Laura Spitler, who led the research. (She was at Cornell University when the study began, but is now at the Max Planck Institute for Radio Astronomy in Bonn, Germany.)
Will you see it? Comet Jacques will pass about 3.5 degrees north of brilliant Venus tomorrow morning July 13. This map shows the sky facing northeast about 1 hour before sunrise. Stellarium
Comet C/2014 E2 Jacques has returned! Before it disappeared in the solar glow this spring, the comet reached magnitude +6, the naked eye limit. Now it’s back at dawn, rising higher each morning as it treks toward darker skies. Just days after its July 2 perihelion, the fuzzball will be in conjunction with the planet Venus tomorrow morning July 13. With Mercury nearby, you may have the chance to see this celestial ‘Rat Pack’ tucked within a 8° circle.
First photo of Comet Jacques on its return to the morning sky taken on July 11. Two tails are visible – a short, dust tail pointing to the lower left of the coma and longer gas or ion tail to the right. Credit: Gerald Rhemann
While I can guarantee you’ll see Venus and probably Mercury (especially if you use binoculars), morning twilight and low altitude will undoubtedly make spotting Comet Jacques challenging. A 6-inch telescope might nail it. Look for a small, fuzzy cloud with a brighter core against the bluing sky. Patience is the sky observer’s most useful tool. It won’t be long before the comet’s westward motion combined with the seasonal drift of the stars will loft it into darkness again.
Use this map to follow Comet Jacques as it moves west across Taurus and Auriga over the next few weeks. Planet positions are shown for July 13 with stars to magnitude +6. Jacques’ position is marked every 5 days. Click to enlarge. Source: Chris Mariott’s SkyMap
A week from now, when the moon’s slimmed to half, the comet will be nearly twice as high and should be easily visible in 50mm binoculars at the start of morning twilight.
Comet Jacques is expected to remain around magnitude +6 through the remainder of July into early August and then slowly fade. It will be well-placed in Perseus at the time of the Perseid meteor shower on Aug. 12-13. Closest approach to Earth occurs on August 29 at 52.4 million miles (84.3 million km). Good luck and let us know if you see it.
The dwarf galaxy UGC 5189A, site of the supernova SN 2010jl. Image Credit: ESO
The Universe is overflowing with cosmic dust. Planets form in swirling clouds of dust around a young star; Dust lanes hide more-distant stars in the Milky Way above us; And molecular hydrogen forms on the dust grains in interstellar space.
Even the soot from a candle is very similar to cosmic carbon dust. Both consist of silicate and amorphous carbon grains, although the size grains in the soot are 10 or more times bigger than typical grain sizes in space.
But where does the cosmic dust come from?
A group of astronomers has been able to follow cosmic dust being created in the aftermath of a supernova explosion. The new research not only shows that dust grains form in these massive explosions, but that they can also survive the subsequent shockwaves.
Stars initially draw their energy by fusing hydrogen into helium deep within their cores. But eventually a star will run out of fuel. After slightly messy physics, the star’s contracted core will begin to fuse helium into carbon, while a shell above the core continues to fuse hydrogen into helium.
The pattern continues for medium to high mass stars, creating layers of different nuclear burning around the star’s core. So the cycle of star birth and death has steadily produced and dispersed more heavy elements throughout cosmic history, providing the substances necessary for cosmic dust.
“The problem has been that even though dust grains composed of heavy elements would form in supernovae, the supernova explosion is so violent that the grains of dust may not survive,” said coauthor Jens Hjorth, head of the Dark Cosmology Center at the Niels Bohr Institute in a press release. “But cosmic grains of significant size do exist, so the mystery has been how they are formed and have survived the subsequent shockwaves.”
The team led by Christa Gall used ESO’s Very Large Telescope at the Paranal Observatory in northern Chile to observe a supernova, dubbed SN2010jl, nine times in the months following the explosion, and for a tenth time 2.5 years after the explosion. They observed the supernova in both visible and near-infrared wavelengths.
SN2010jl was 10 times brighter than the average supernova, making the exploding star 40 times the mass of the Sun.
“By combining the data from the nine early sets of observations we were able to make the first direct measurements of how the dust around a supernova absorbs the different colours of light,” said lead author Christa Gall from Aarhus University. “This allowed us to find out more about the dust than had been possible before.”
The results indicate that dust formation starts soon after the explosion and continues over a long time period.
The dust initially forms in material that the star expelled into space even before it exploded. Then a second wave of dust formation occurs, involving ejected material from the supernova. Here the dust grains are massive — one thousandth of a millimeter in diameter — making them resilient to any following shockwaves.
“When the star explodes, the shockwave hits the dense gas cloud like a brick wall. It is all in gas form and incredibly hot, but when the eruption hits the ‘wall’ the gas gets compressed and cools down to about 2,000 degrees,” said Gall. “At this temperature and density elements can nucleate and form solid particles. We measured dust grains as large as around one micron (a thousandth of a millimeter), which is large for cosmic dust grains. They are so large that they can survive their onward journey out into the galaxy.”
If the dust production in SN2010jl continues to follow the observed trend, by 25 years after the supernova explosion, the total mass of dust will have half the mass of the Sun.
Seven new dwarf galaxies shine in the field of view surrounding M101, the Pinwheel Galaxy. Credit: Yale University
Using a unique type of telescope that includes long-range lenses, astronomers at Yale University have found seven dwarf galaxies surrounding the well-known Pinwheel Galaxy, M101.
It’s unclear if the septuplets are actually orbiting the pinwheel, or just happen to be in the same field of view. But astronomers at Yale say that this shows the so-called Dragonfly Telephoto Array is working well, and they are planning follow-up observations to see what else they can find.
“The previously unseen galaxies may yield important insights into dark matter and galaxy evolution, while possibly signaling the discovery of a new class of objects in space,” Yale University stated in a release.
The galaxies escaped detection before because their light is so diffuse, but this is what the telescope is designed to pick up. The telescope is constructed of eight telephoto lenses (similar to what you would use to photograph a sporting event) that include “special coating” to stop any light from scattering inside. The telescope is called “Dragonfly” because like an insect, it has multiple eyes for looking at things.
The Dragonfly Telephoto Array, a unique Yale University telescope used to look for diffuse light in galaxies. Credit: Yale University
Follow-up observations will come with the Hubble Space Telescope. If it turns out that these galaxies are not bound to M101, the results will be equally interesting to astronomers.
“There are predictions from galaxy formation theory about the need for a population of very diffuse, isolated galaxies in the universe,” stated Allison Merritt, a Yale graduate student who led the research.
“It may be that these seven galaxies are the tip of the iceberg, and there are thousands of them in the sky that we haven’t detected yet.”
There’s no doubt the term “Earth-like” is a bit of a misnomer. It requires only that a planet is both Earth-size (less than 1.25 times Earth’s girth and less than twice Earth’s mass) and circles its host star within the habitable zone.
But defining a “Sun-like” star may be just as difficult. A solar twin should have a temperature, mass, age, radius, metallicity, and spectral type similar to the Sun. Although measuring most of these factors isn’t easy, aging a star is extremely difficult, and astronomers tend to ignore it when concluding if a star is Sun-like or not.
This is less than ideal, given that our Sun and all stars change over time. Thankfully a technique — gyrochronology — is allowing astronomers to measure stellar ages based only on spin and find true solar analogues.
“We have found stars with properties that are close enough to those of the Sun that we can call them ‘solar twins,'” said lead author Jose Dias do Nascimento from the Harvard-Smithsonian Center for Astrophysics (CfA) in a press release.
do Nascimento and colleagues measured the spin of 75 stars by looking for changes in brightness caused by dark star spots, rotating in and out of view. Although this difference is minute, clocking in at a few percent or less, NASA’s Kepler spacecraft excels at extracting such small changes in brightness.
On average, the sampled stars spin once every 19 days, compared to the 25-day rotation period of the Sun. This makes most of the stars slightly younger than the Sun, as younger stars spin faster than older ones.
The relationship between stellar spin and age was determined in previous research by Soren Meibom (CfA) and colleagues, who measured the rotation rates for stars in a one-billion-year-old cluster. Since the stars already had a known age, the team could measure their spin rates and calibrate the previous relationship.
Using this method, do Nascimento and colleagues found 22 true solar analogues within their data set of 75 stars.
“With solar twins we can study the past, present, and future of stars like our Sun,” said do Nascimento. “Consequently, we can predict how planetary systems like our solar system will be affected by the evolution of their central stars.”
The results were accepted for publication in The Astrophysical Journal Letters and are available online.
