Nu2 Lupi is a G-class star not all that far away in astronomical terms (48 light years) in the constellation Lupus, its proximity verified by parallax measurements and firmed up by the Hipparcos satellite. This is one of the closest G-class stars to our own, and it’s a fast mover in other ways, with a high radial velocity. Its age is estimated at roughly 12 billion years, making it one of the oldest stars near our system. HARPS spectrograph data pulled up three planets here in 2019, two of them later found to transit. And now we have, unexpectedly, a third transit. The surprising nature of the third relates to the distance of the third planet from the star. The two inner worlds, with masses between Earth’s and Neptune’s, take 12 and 28 days to orbit Nu2 Lupi. The third takes 107 days, far enough out that a transit seemed unlikely. The ratio of the diameter of the star to the diameter of the orbit comes into play in determining the probability of a transit. We have the European Space...

Call it the Earth Transit Zone, that region of space from which putative astronomers on an exoplanet could see the Earth transit the Sun. Lisa Kaltenegger (Cornell University) is director of the Carl Sagan Institute and the author of a 2020 paper with Joshua Pepper (LeHigh University) that examined the stars within the ETZ (see Seeing Earth as a Transiting World). While Kaltengger and Pepper identified 1004 main sequence stars within 100 parsecs that would see Earth as a transiting planet, Kaltenegger reminds us that stars are ever in motion. Given the abundant resources available in the European Space Agency's Gaia eDR3 catalog, why not work out positions and stellar motions to examine the question over time? After all, there are SETI implications here. We study planetary atmospheres using data taken during transits. Are we, in turn, the subject of such study from astronomers elsewhere in the cosmos? Thus Kaltenegger's new paper in Nature, written with Jackie Faherty (American...

The Allende meteorite is the largest carbonaceous chondrite meteorite ever discovered. Falling over Mexico's state of Chihuahua in 1969 and breaking up in the atmosphere, the object yielded over two tons of material that have provided fodder for scientists interested in the early days of the Solar System. The meteorite contains numerous calcium-aluminum-rich inclusions (CAIs), which are considered to be the first kind of solids formed in the system 4.5 billion years ago. Samples of the Allende meteorite are considered 'primitive,' which in this parlance means unaffected by significant alteration since formation. Now a team led by Tom Zega (University of Arizona Lunar and Planetary Laboratory) has gone to work on a dust grain from this object, in order to simulate the conditions under which it formed in the Sun's protoplanetary disk. The grain was drawn from one of several CAIs discovered in the Allende meteorite sample. Analysis of the sample's chemistry and crystal structure...

As we learn more about how planetary systems form, it's becoming accepted that a large number of planets are being ejected from young systems because of their interactions with more massive worlds. I always referred to these as 'rogue planets' in previous articles on the subject, but a new paper from Patricio Javier Ávila (University of Concepción, Chile) and colleagues makes it clear that the term Free Floating Planet (FFP) is now widespread. A new acronym for us to master! There have been searches to try to constrain the number of free floating planets, though the suggested ranges are wide. Microlensing seems the best technique, as it can spot masses we cannot otherwise see through their effect on background starlight. Of these, the estimates come in at around 2 Jupiter-mass planets and 2.5 terrestrial-class rocky worlds per star that have been flung into the darkness. This is a vast number of planets, but we have to be wary of mass uncertainties, as the cut-off between...

The beauty of nearby M-dwarf stars for exoplanet research is the depth of transits. If we are fortunate enough to find a planet crossing the face of the star as seen from our observatory, the star's small size means a larger portion of its light will be attenuated. As you would imagine, this makes planets easier to spot, but the other significant advantage is that we have greater capability at analyzing the planet's atmosphere. TOI-1231b certainly fits the bill, although it's a bit of an anomaly in the TESS universe. The space observatory operates with a built in observational bias because the Science Processing Operations Center (SPOC) pipeline and the Quick Look Pipeline (QLP) that comb through TESS data on a 2-minute and 30 minute cadence respectively have to show two transits for the planet's period to be determined. Factor in that most of the TESS sky coverage is observed for 28 days and you wind up in the majority of cases with detections of planets with orbital periods of less...

You can blame H. G. Wells' The Time Machine for my interest in the Earth's far future. That swollen red Sun at the end of the novel created vivid 'end of the world' scenarios for me as a boy, and later I would learn that outer planets or moons around a G-class star might turn habitable once it became a red giant. But it would only be in the last few years that I learned how robust the investigations into white dwarf systems -- the fate of a red giant -- have become, and now we're finding out not only that such stars can retain planets, but can conceivably create new ones through an emerging disk packed with the pulverized dust of remnant materials like asteroids. Image: This artist's concept shows a white dwarf debris disk. Credit: NASA/JPL-Caltech. Jordan Steckloff (Planetary Science Institute, Tucson) has just published a short paper on the matter, looking at how white dwarf debris disks emerge. The disks seem to form only after ten to twenty million years following the end of the...