Category: Discoveries (page 1 of 4)

A Southern Sky Extravaganza From TESS

Candidate exoplanets as seen by TESS in a southern sky mosaic from 13 observing sectors. (NASA/MIT/TESS)

NASA’s Transiting Exoplanet Survey Satellite (TESS) has finished its one year full-sky observation of  Southern sky and has found hundreds of candidate exoplanets and 29 confirmed planets.  It is now maneuvering  its array of wide-field telescopes and cameras to focus on the northern sky to do the same kind of exploration.

At this turning point, NASA and the Massachusetts Institute of Technology — which played a major role in designing and now operating the mission — have put together mosaic images from the first year’s observations, and they are quite something.

Constructed from 208 TESS images taken during the mission’s first year of science operations, these images are a unique  space-based look at the entire Southern sky — including the Milky Way seen edgewise, the Large and Small Magellenic galaxies, and other large stars already known to have exoplanet.

“Analysis of TESS data focuses on individual stars and planets one at a time, but I wanted to step back and highlight everything at once, really emphasizing the spectacular view TESS gives us of the entire sky,” said Ethan Kruse, a NASA Postdoctoral Program Fellow who assembled the mosaic at NASA’s Goddard Space Flight Center.

Overlaying the figures of selected constellations helps clarify the scale of the TESS southern mosaic. TESS has discovered 29 exoplanets, or worlds beyond our solar system, and more than 1,000 candidate planets astronomers are now investigating. NASA/MIT/TESS

The mission is designed to vastly increase the number of known exoplanets, which are now theorized to orbit all — or most — stars in the sky.

TESS searches for  the nearest and brightest main sequence stars hosting transiting exoplanets, which are the most favorable targets for detailed investigations.

This animation shows how a dip in the observed brightness of a star may indicate the presence of a planet passing in front of it, an occurrence known as a transit. This is how TESS identified planet.
(NASA’s Goddard Space Flight Center)

While previous sky surveys with ground-based telescopes have mainly detected giant exoplanets, TESS will find many small planets around the nearest stars in the sky.  The mission will also provide prime targets for further characterization by the James Webb Space Telescope, as well as other large ground-based and space-based telescopes of the future.

The TESS observatory uses an array of wide-field cameras to perform a survey of 85% of the sky.… Read more

A Telling Nobel Exoplanet Faux Pas

This is the Doppler velocity curve displayed by the Nobel Committee to illustrate what Mayor and Queloz had accomplished in 1995. But actually, the graph shows the curve from the Lick Observatory in California that an American team had produced to confirm the initial finding. Such was the interweaving of the work of the Swiss and the American teams searching for the first exoplanet orbiting a sun-like star. (Image courtesy of Geoff Marcy and Paul Butler, San Francisco State University)

Given the complex history of the discovery and announcement in 1995 of the first exoplanet that orbits a sun-like star, it is perhaps no surprise that errors might sneak into the retelling.  Two main groups were racing to be first, and for a variety of reasons the discovery ended up being confirmed before it was formally announced.

A confusing situation prone to mistakes if all involved aren’t entirely conversant with the details.  But an error — tantamount to scientific plagiarism — by the Nobel Committee?   That is a surprise.

The faux pas occurred at the announcement on October 8 that Michel Mayor of the University of Geneva and Didier Queloz of the the University of Cambridge had won the Nobel for physics to honor their work in detecting that first exoplanet orbiting a sun-like star.

As Nobel Committee member Ulf Danielsson described the achievement, a powerpoint display of important moments and scientific findings in their quest was displayed on a screen behind him.

When the ultimate image was on deck to be shown  — an image that presented the Doppler velocity curve that was described as the key to the discovery — the speaker appeared to hesitate after looking down to see what was coming next.

If he did hesitate, it was perhaps because to those in the know, the curve did not come from Mayor and Queloz.

Rather, it was the work of a team led by Geoffrey Marcy and Paul Butler — the San Francisco State University group that confirmed the existence of the hot Jupiter exoplanet 51 Pegasi b several days after the discovery was made public (to some considerable controversy) at a stellar systems conference in Florence.  So at a most significant juncture of the Nobel introduction of the great work of Mayor and Queloz, hard-won data by a different team was presented as part of the duo’s achievement.

This is both awkward and embarrassing, but it also indirectly points to one of the realities that the Nobel Committee is forced, by the will of Alfred Nobel, to ignore:  That science is seldom the work now of but two or three people.… Read more

The Remarkable Race to Find the First Exoplanet, And the Nobel Prize It Produced

Rendering of the planet that started it all — 51 Pegasi b. It is a “hot Jupiter” that, when discovered, broke every astronomical rule regarding where types of planets should be in a solar system. (NASA)

Earlier this week, the two men who detected the first planet outside our solar system that circled a sun-like star won a Nobel Prize in physics.  The discovery heralded the beginning of the exoplanet era — replacing a centuries-old scientific supposition that planets orbited other stars with scientific fact.

The two men are Michel Mayor,  Professor Emeritus at the University of Geneva and Didier Queloz, now of Cambridge University.  There is no Nobel Prize in astronomy and the physics prize has seldom gone to advances in the general field of astronomy and planetary science.  So the selection is all the more impressive.

Mayor and Queloz worked largely unknown as they tried to make their breakthrough, in part because previous efforts to detect exoplanets (planets outside our solar system) orbiting sun-like stars had fallen short, and also because several claimed successes turned out to be unfounded.  Other efforts proved to be quite dangerous:  a Canadian duo used poisonous and corrosive hydrogen flouride vapor in the 1980s as part of their planet-hunting effort.

But since their 1995 discovery opened the floodgates, the field of exoplanet science has exploded.  More than 4,000 exoplanets have been identified and a week seldom goes by without more being announced.  The consensus scientific view is now that billions upon billions of exoplanets exist in our galaxy alone.

While Mayor and Queloz were pioneers for sure, they did not work in a vacuum.  Rather, they were in a race of sorts with an American team that had also been working in similar near anonymity for years to also find an exoplanet.

And so here is a human, rather than a purely scientific, narrative look — reported over the years — into the backdrop to the just announced Nobel Prize.  While Mayor and Queloz were definitely the first to find an exoplanet, they were quite close to being the second.

 

Swiss astronomers Didier Queloz and Michel Mayor are seen here in 2011 in front of the European Southern Observatory’s ’s 3.6-metre telescope at La Silla Observatory in Chile. The telescope hosts the High Accuracy Radial Velocity Planet Searcher (HARPS), one of the world’s leading exoplanet hunters.  After the discovery of 51 Pegasi b, Mayor led the effort to build the HARPS planet-finding spectrometer.

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The Giant Moon That Might Be the Heart of a Jupiter

Artist’s impression of the exomoon candidate Kepler-1625b-i, the planet it is orbiting and the star. (NASA/ESA/L. Hustak, STScI)

“Moons are where planets were in the 1990s,” predicted René Heller from the Max Planck Institute for Solar System Research a few years ago. “We’re on the brink.”

Heller was predicting that we were close to the first discoveries of exomoons: moons that orbit extrasolar planets outside our solar system. When a possible exomoon detection was announced in 2017, Heller’s prediction was proved correct. Not only had we found a candidate moon, but its properties defied our formation theories just as with the discoveries of the first exoplanets.

However, a paper published in Science this month has proposed a method for building this most unusual of moons.

As we move away from the sun, the planets of our solar system become mobbed with moons. How these small worlds formed is attributed to three different processes:

Moons in our solar system are thought to have formed through three different mechanisms (E. Tasker / Many Worlds)

The most extensive moon real estate orbits our gas giants, Jupiter, Saturn, Uranus and Neptune. The majority of these moons are thought to have been born during the planets’ own formation, forming in disks of gas, dust and ice that circled the young worlds. These circumplanetary disks are like miniaturised versions of the protoplanetary disks that circle young stars and give rise to planets.

One exception to this is Neptune’s moon, Triton, which orbits in the opposite direction to the planet’s rotation. This retrograde path would not be expected to arise if Triton has formed out of a circumplanetary disk around Neptune, which always rotate the same direction as the forming planet. Instead, Triton was likely a dwarf planet that was snagged by Neptune’s gravity during a chance encounter.

The capture scenario has also been proposed for the two moons of Mars. The lumpy satellites resemble asteroids and may have been born in the asteroid belt that sits between Mars and Jupiter. However, both moons orbit the red planet in circular orbits that sit in the same plane, pointing to a more disk-like formation method. Although Mars is too small to have had a substantial circumplanetary disk during formation, a giant impact later in its history could have thrown debris into orbit. This debris disk could then have coalesced into the two moons.

Such a violent start to Mars’s moons would mimic the beginnings of our own moon.… Read more

The Planets Too Big for Their Star

Artist rendering of a red dwarf , with three exoplanets orbiting. About 75% of all stars in the sky are the cooler, smaller red dwarfs. (NASA)

Two giant planets have been found orbiting a tiny star, defying our theories for how planets are formed.

To be entirely truthful, there is nothing new in an exoplanet discovery shredding our current ideas about how planets are built. The first extrasolar planets ever discovered orbit a dead star known as a pulsar. Pulsars end their regular starry life in a colossal supernova explosion that should incinerate or eject any orbiting worlds. This discovery was followed a few years later by the first detection of a hot Jupiter; a gas giant planet orbiting its star in just a few days, defying theories that said such planets should form on long orbits where there is more building material to make massive worlds. Exoplanet hunting is a field full of surprises and now, it has one more.

GJ 3512 is a red dwarf star with a luminosity only around a thousandth (0.0016L) of our sun. The small size of these stars makes it easier to detect the presence of a planet, and many of our most famous exoplanet discoveries have been found orbiting red dwarf stars, including Proxima Centauri b and the seven worlds in the TRAPPIST-1 system. But a notable attribute of these systems is that the planets are small. Unlike our own sun which boasts four gas giant worlds, planets around red dwarfs are typically smaller than Neptune.

Artist impression of the seven planets of Trappist-1 that also orbit a red dwarf star. These are small worlds. Jupiter-sized gas giants were not previously thought to form around the small red dwarf stars (NASA/JPL-Caltech).

This preference for downsized worlds is assumed to be due to the protoplanetary disk; the disk of dust and gas that swirls around young stars out of which planets are born. Protoplanetary disks around small stars tend to be low mass and puffy. This limits and spreads out the solid material, making it difficult for a young planet to grow.

Yet the two planets discovered around GJ 3512 are not small.
Led by Juan Carlos Morales at the IEEC Institute of Space Studies of Catalonia, the announcement of the discovery was published in the journal Science today.

The team detected these two new worlds using the radial velocity technique which measures the wobble in the position of the star due to the gravitational tug of the orbiting planet.… Read more

Exoplanets Discoveries Flood in From TESS

NASA’s Transiting Exoplanet Survey Satellite (TESS) has hundreds of “objects of interest” waiting to be confirmed as planets in the data from the space telescope’s four cameras.  These three were the first confirmed TESS discoveries, identified last year during its first three months of observing. By the time the mission is done, TESS’s wide-field cameras will have covered the whole sky in search of transiting exoplanets around 200,000 of the nearest (and brightest) stars. (NASA / MIT / TESS)

The newest space telescope in the sky — NASA’s Transiting Exoplanet Survey Satellite, TESS — has been searching for exoplanets for less than a year, but already it has quite a collection to its name.

The TESS mission is to find relatively nearby planets orbiting bright and stable suns, and so expectations were high from the onset about the discovery of important new planets and solar systems.  At a meeting this week at the Massachusetts Institute of Technology devoted to TESS  results,  principal investigator George Ricker pronounced the early verdict.

The space telescope, he said,  “has far exceeded our most optimistic hopes.”  The count is up to 21 new planets and 850 additional  candidate worlds waiting to be confirmed.

Equally or perhaps more important is that the planets and solar systems being discovered promise important results.  They have not yet included any Earth-sized rocky planet in a sun’s habitable zone — what is generally considered the most likely, though hardly the only, kind of planet to harbor life — but they did include planets that offer a great deal when it comes to atmospheres and how they can be investigated.

This infographic illustrates key features of the TOI 270 system, located about 73 light-years away in the southern constellation Pictor. The three known planets were discovered by NASA’s Transiting Exoplanet Survey Satellite through periodic dips in starlight caused by each orbiting world. Insets show information about the planets, including their relative sizes, and how they compare to Earth. Temperatures given for TOI 270’s planets are equilibrium temperatures, (NASA’s Goddard Space Flight Center/Scott Wiessinger)

One of the newest three-planet system is called TOI-270, and it’s about 75 light years from Earth. The star at the center of the system is a red dwarf, a bit less than half the size of the sun.

Despite its small size, it’s brighter than most of the nearby stars we know host planets. And it’s stable, making its solar system especially valuable.

Read more

Our Ever-Growing Menagerie of Exoplanets

While we have never seen an exoplanet with anything near this kind of detail, scientists and artists now do know enough to represent them with characteristics that are plausible, given what is known about them..  (NASA)

With so many exoplanets already detected, with the pace of discovery continuing to be so fast, and with efforts to find more distant worlds so constant and global,  it’s easy to become somewhat blase´ about new discoveries.  After so many “firsts,” and so many different kinds of planets found in very different ways, it certainly seems that some of the thrill may be gone.

Surely the detection of a clearly “Earth-like planet” would cause new excitement — one that is not only orbiting in the habitable zone of its host star but also has signs of a potentially nurturing atmosphere in a generally supportive cosmic neighborhood.

But while many an exoplanet has been described as somewhat “Earth-like” and potentially habitable, further observation has consistently reduced the possibility of the planets actually hosting some form of biology.  The technology and knowledge base needed to find distant life is surely advancing, but it may well still have a long way to go.

In just the last few days, however, a slew of discoveries have been reported that highlight the allure and science of our new Exoplanet Era.  They may not be blockbusters by themselves, but they are together part of an immense scientific exploration under way, one that is re-shaping our understanding of the cosmos and preparing us for bigger discoveries and insights to come.

 

Already 3,940 exoplanets have been identified (as of April 17) with an additional 3,504 candidates waiting to be confirmed or discarded.  this is but the start since it is widely held now that virtually every star out there has a planet, or planets, orbiting it.   That’s billions of billions of planets.  This image is a collection of NASA exoplanet renderings.

What I have in mind are these discoveries:

  • The first Earth-sized planet detected by NASA’s year-old orbiting telescope TESS (Transiting Exoplanet Survey Satellite.)  TESS is designed to find planets orbiting massive stars in our near neighborhood, and it has already made 10 confirmed discoveries.  But finding a small exoplanet — 85 percent the size of Earth — is a promising result for a mission designed to not only locate as many as 20,000 new exoplanets, but to find 500 to 1,000 the rough size of Earth or SuperEarth. 
Read more

Weird Planets

 

 

Artist rendering of an “eyeball world,” where one side of a tidally locked planet is always hot on the sun-facing side and the back side is frozen cold.  Definitely a tough environment, but  might some of the the planets be habitable at the edges?  Or might winds carry sufficient heat from the front to the back?  (NASA/JPL-Caltech)

The very first planet detected outside our solar system powerfully made clear that our prior understanding of what planets and solar systems could be like was sorely mistaken.

51 Pegasi was a Jupiter-like massive gas planet, but it was burning hot rather than freezing cold because it orbited close to its host star — circling in 4.23 days.  Given the understandings of the time, its existence was essentially impossible. 

Yet there it was, introducing us to what would become a large and growing menagerie of weird planets.

Hot Jupiters, water worlds, Tatooine planets orbiting binary stars, diamond worlds (later downgraded to carbon worlds), seven-planet solar systems with planets that all orbit closer than Mercury orbits our sun.  And this is really only a brief peak at what’s out there — almost 4,000 exoplanets confirmed but billions upon billions more to find and hopefully characterize.

I thought it might be useful — and fun — to take a look at some of the unusual planets found to learn what they tell us about planet formation, solar systems and the cosmos.

 


Artist’s conception of a hot Jupiter, CoRoT-2a. The first planet discovered beyond our solar system was a hot Jupiter similar to this, and this surprised astronomers and led to the view that many hot Jupiters may exist. That hypothesis has been revised as the Kepler Space Telescope found very few distant hot Jupiters and now astronomers estimate that only about 1 percent of planets are hot Jupiters. (NASA/Ames/JPL-Caltech)

 

Let’s start with the seven Trappist-1 planets.  The first three were detected two decades ago, circling a”ultra-cool” red dwarf star a close-by 40 light years away.  Observations via the Hubble Space Telescope led astronomers conclude that two of the planets did not have hydrogen-helium envelopes around them, which means the probability increased that the planets are rocky (rather than gaseous) and could potentially hold water on their surfaces.

Then in 2016 a Belgian team, using  the Transiting Planets and Planetesimals Small Telescope (TRAPPIST) in Chile, found three more planets, and the solar system got named Trappist-1. Read more

The Kepler Space Telescope Mission Is Ending But Its Legacy Will Keep Growing.

An illustration of the Kepler Space Telescope, which is on its very last legs.  As of October 2018, the planet-hunting spacecraft has been in space for nearly a decade. (NASA via AP)

 

The Kepler Space Telescope is dead.  Long live the Kepler.

NASA officials announced on Tuesday that the pioneering exoplanet survey telescope — which had led to the identification of almost 2,700 exoplanets — had finally reached its end, having essentially run out of fuel.  This is after nine years of observing, after a malfunctioning steering system required a complex fix and change of plants, and after the hydrazine fuel levels reached empty.

While the sheer number of exoplanets discovered is impressive the telescope did substantially more:  it proved once and for all that the galaxy is filled with planets orbiting distant stars.  Before Kepler this was speculated, but now it is firmly established thanks to the Kepler run.

It also provided data for thousands of papers exploring the logic and characteristics of exoplanets.  And that’s why the Kepler will indeed live long in the world of space science.

“As NASA’s first planet-hunting mission, Kepler has wildly exceeded all our expectations and paved the way for our exploration and search for life in the solar system and beyond,” said Thomas Zurbuchen, associate administrator of NASA’s Science Mission Directorate in Washington.

“Not only did it show us how many planets could be out there, it sparked an entirely new and robust field of research that has taken the science community by storm. Its discoveries have shed a new light on our place in the universe, and illuminated the tantalizing mysteries and possibilities among the stars.”

 

 


The Kepler Space Telescope was focused on hunting for planets in this patch of the Milky Way. After two of its four spinning reaction wheels failed, it could no longer remain steady enough to stare that those distant stars but was reconfigured to look elsewhere and at a different angle for the K2 mission. (Carter Roberts/NASA)

 

Kepler was initially the unlikely brainchild of William Borucki, its founding principal investigator who is now retired from NASA’s Ames Research Center in California’s Silicon Valley.

When he began thinking of designing and proposing a space telescope that could potentially tell us how common distant exoplanets were — and especially smaller terrestrial exoplanets like Earth – the science of extra solar planets was at a very different stage.… Read more

Water Worlds, Aquaplanets and Habitability

This artist rendering may show a water world — without any land — or an aquaplanet with lots of more shallow water around a rocky planet. (NASA)

 

The more exoplanet scientists learn about the billions and billions of celestial bodies out there, the more the question of unusual planets — those with characteristics quite different from those in our solar system — has come into play.

Hot Jupiters, super-Earths, planets orbiting much smaller red dwarf stars — they are all grist for the exoplanet mill, for scientists trying to understand the planetary world that has exploded with possibilities and puzzles over the past two decades.

Another important category of planets unlike those we know are the loosely called “water worlds” (with very deep oceans) and their “aquaplanet” cousins (with a covering of water and continents) but orbiting stars very much unlike our sun.

Two recent papers address the central question of habitability in terms of these kind of planets — one with oceans and ice hundreds of miles deep, and one particular and compelling planet (Proxima Centauri b, the exoplanet closest to us) hypothesized to have water on its surface as it orbits a red dwarf star.

The question the papers address is whether these watery worlds might be habitable.  The conclusions are based on modelling rather than observations, and they are both compelling and surprising.

In both cases — a planet with liquid H20 and ice many miles down, and another that probably faces its red dwarf sun all or most of the time — the answers from modelers is that yes, the planets could be habitable.   That is very different from saying they are or even might be inhabited.  Rather,  the conclusions are based on computer models that take into account myriad conditions and come out with simulations about what kind of planets they might be.

This finding of potential watery-world habitability is no small matter because predictions of how planets form point to an abundance of water and ice in the planetesimals that grow into planets.

As described by Eric Ford, co-author of one of the papers and a professor of astrophysics at Pennsylvania State University, “Many scientists anticipate that planets with oceans much deeper than Earths could be a common outcome of planet formation. Indeed, one of the puzzling properties of Earth is that it has oceans that are just skin deep” compared to the radius of the planet.… Read more

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