Podcast: The Search for Planet Nine

Posted on by onespaceman2000
Image (Credit): Artist’s rendering of a proposed Planet Nine. (NASA/JPL-Caltech)

I listened to a recent Cool Worlds Lab podcast where Professor David Kipping interviewed Professor Malena Rice from Yale University’s Department of Astronomy. The episode, titled  Planet Nine, Oumuamua, Misaligned Exoplanets, covered a good range of topics, as the title suggests.

Of greatest interest to me was the continued search for a ninth planet in our solar system (sorry, Pluto). Professor Rice was noncommittal on the likelihood of such a planet, but she is hoping NASA’s Transiting Exoplanet Survey Satellite (TESS) can help to bring more light to the topic.

She discussed how this ninth planet is estimated to be a sub-Neptune sized planet, which appears to be common in many other solar systems we have observed. Planet Nine is estimated to be a gas giant about 5-10 times the mass of Earth yet smaller than Neptune lying 300-800 astronomical units from the Sun (or about 10 times more distant that Pluto).

Professor Rice noted that it is pretty amazing that we can discover distant galaxies but not potential planets in our backyard. She attributes this difficulty to the lack of light on such a planet.

The podcast episode dives deep in this topic, and then continues into other fascinating topics such as visitors to our solar system and strange solar systems elsewhere. It is a lot to take in, but well worth the time even if you need to play it more than once.

Note: Of course, it may not be a planet at all. One theory is that it is a black hole at the edge of our solar system. I would like to hear that podcast as well.

Study Findings: A Resonant Sextuplet of Sub-Neptunes Transiting the Bright Star HD 110067

Posted on by onespaceman2000
Image (Credit): Neptune as captured by the James Webb Space Telescope’s near-infrared camera. (NASA, ESA, CSA, and STScI)

Nature abstract of the study findings:

Planets with radii between that of the Earth and Neptune (hereafter referred to as ‘sub-Neptunes’) are found in close-in orbits around more than half of all Sun-like stars. However, their composition, formation and evolution remain poorly understood. The study of multiplanetary systems offers an opportunity to investigate the outcomes of planet formation and evolution while controlling for initial conditions and environment. Those in resonance (with their orbital periods related by a ratio of small integers) are particularly valuable because they imply a system architecture practically unchanged since its birth. Here we present the observations of six transiting planets around the bright nearby star HD 110067. We find that the planets follow a chain of resonant orbits. A dynamical study of the innermost planet triplet allowed the prediction and later confirmation of the orbits of the rest of the planets in the system. The six planets are found to be sub-Neptunes with radii ranging from 1.94R⊕ to 2.85R⊕. Three of the planets have measured masses, yielding low bulk densities that suggest the presence of large hydrogen-dominated atmospheres.

Citation: Luque, R., Osborn, H.P., Leleu, A. et al. A resonant sextuplet of sub-Neptunes transiting the bright star HD 110067. Nature 623, 932–937 (2023).
https://doi.org/10.1038/s41586-023-06692-3

Study-related stories:

Space Stories: Curiosity Continues, Exoplanets with Dinosaurs, and Nasty Jupiters

Posted on by onespaceman2000
Image (Credit): Curiosity’s view of the Martian surface. (NASA)

Here are some recent stories of interest.

—NASA JPL: “NASA’s Curiosity Rover Clocks 4,000 Days on Mars“

Four thousand Martian days after setting its wheels in Gale Crater on Aug. 5, 2012, NASA’s Curiosity rover remains busy conducting exciting science. The rover recently drilled its 39th sample then dropped the pulverized rock into its belly for detailed analysis. To study whether ancient Mars had the conditions to support microbial life, the rover has been gradually ascending the base of 3-mile-tall (5-kilometer-tall) Mount Sharp, whose layers formed in different periods of Martian history and offer a record of how the planet’s climate changed over time.

—Cornell University: “‘Jurassic Worlds’ Might be Easier to Spot than Modern Earth“

Things may not have ended well for dinosaurs on Earth, but Cornell University astronomers say the “light fingerprint” of the conditions that enabled them to emerge here provide a crucial missing piece in our search for signs of life on planets orbiting alien stars. Their analysis of the most recent 540 million years of Earth’s evolution, known as the Phanerozoic Eon, finds that telescopes could better detect potential chemical signatures of life in the atmosphere of an Earth-like exoplanet more closely resembling the age the dinosaurs inhabited than the one we know today.

—UC Riverside: “Giant Planets Cast a Deadly Pall“

Jupiter, by far the biggest planet in our solar system, plays an important protective role. Its enormous gravitational field deflects comets and asteroids that might otherwise hit Earth, helping create a stable environment for life. However, giant planets elsewhere in the universe do not necessarily protect life on their smaller, rocky planet neighbors. A new Astronomical Journal paper details how the pull of massive planets in a nearby star system are likely to toss their Earth-like neighbors out of the “habitable zone.” This zone is defined as the range of distances from a star that are warm enough for liquid water to exist on a planet’s surface, making life possible.

Space Stories: Dinosaur Dust, Missing Stars, and SETI Signals

Posted on by onespaceman2000
Image (Credit): The end of the dinosaurs. (NYT, Roger Harris/Science Source)

Here are some recent stories of interest.

—Royal Observatory of Belgium: “Dust Played a Major Role in Dinosaur Demise“

Fine dust from pulverized rock generated by the Chicxulub impact likely played a dominant role in global climate cooling and the disruption of photosynthesis following the event. This is suggested by a new study published in Nature Geoscience, in which researchers Cem Berk Cenel, Özgür Karatekin and Orkun Temel of the Royal Observatory of Belgium contributed.

—Express: “Astronomers Trying to Unravel Mystery of Three Stars that Suddenly Disappeared from Sky“

A team of Spanish astronomers is leading the investigation into one of stargazing’s most perplexing mysteries. Three bright stars photographed in the night sky above southern California in 1952 vanished just an hour later. Generations of scientists have sought to explain the rare phenomenon over the past half-century, but nothing has yet convinced the community. Researchers at the Centre for Astrobiology (CAB) in Madrid tried to solve the riddle of the “triple transient” that has “remained absent from telescope exposures for 71 years” in a new paper published online.

—Sci.News: “New Study Sets Clearer Bounds on Search for Technosignatures from Extraterrestrial Intelligences“

A stable-frequency transmitter with relative radial acceleration to a receiver will show a change in received frequency over time, known as a ‘drift rate.’ For a transmission from an exoplanet, astronomers must account for multiple components of drift rate: the exoplanet’s orbit and rotation, the Earth’s orbit and rotation, and other contributions. Understanding the drift rate distribution produced by exoplanets relative to Earth, can help scientists constrain the range of drift rates to check in a Search for Extraterrestrial Intelligence (SETI) project to detect radio technosignatures, and help them decide validity of signals-of-interest, as they can compare drifting signals with expected drift rates from the target star. In a new study, University of California, Los Angeles astronomer Megan Grace Li and colleagues modeled the drift rate distribution for over 5,300 confirmed exoplanets, using parameters from the NASA Exoplanet Archive.

Study Findings: A Planetary Collision Afterglow and Transit of the Resultant Debris Cloud

Posted on by onespaceman2000
Image (Credit): Artist’s rendering of two colliding planets. (NASA)

Nature abstract of the study findings:

Planets grow in rotating disks of dust and gas around forming stars, some of which can subsequently collide in giant impacts after the gas component is removed from the disk. Monitoring programmes with the warm Spitzer mission have recorded substantial and rapid changes in mid-infrared output for several stars, interpreted as variations in the surface area of warm, dusty material ejected by planetary-scale collisions and heated by the central star: for example, NGC 2354–ID8, HD 166191 and V488 Persei. Here we report combined observations of the young (about 300 million years old), solar-like star ASASSN-21qj: an infrared brightening consistent with a blackbody temperature of 1,000 Kelvin and a luminosity that is 4 percent that of the star lasting for about 1,000 days, partially overlapping in time with a complex and deep, wavelength-dependent optical eclipse that lasted for about 500 days. The optical eclipse started 2.5 years after the infrared brightening, implying an orbital period of at least that duration. These observations are consistent with a collision between two exoplanets of several to tens of Earth masses at 2–16 astronomical units from the central star. Such an impact produces a hot, highly extended post-impact remnant with sufficient luminosity to explain the infrared observations. Transit of the impact debris, sheared by orbital motion into a long cloud, causes the subsequent complex eclipse of the host star.

Citation: Kenworthy, M., Lock, S., Kennedy, G. et al. A planetary collision afterglow and transit of the resultant debris cloud. Nature 622, 251–254 (2023).
https://doi.org/10.1038/s41586-023-06573-9

Study-related stories: