Elizabeth Tasker

Author: Elizabeth Tasker (page 2 of 2)

NASA’s Planet-Hunter TESS Has Just Been Launched to Check Out the Near Exoplanet Neighborhood

A SpaceX Falcon 9 rocket transporting the TESS satellite lifts off from launch complex 40 at the Cape Canaveral Air Force Station in Cape Canaveral, Fla., Wednesday, April 18, 2018. The space telescope will survey almost the entire sky, staring at the brightest, closest stars in an effort to find any planets that might be encircling them. (AP Photo/John Raoux)

On January 5, 2010, NASA issued landmark press release : the Kepler Space Telescope had discovered its first five new extra-solar planets.

The previous twenty years had seen the discovery of just over 400 planets beyond the solar system. The majority of these new worlds were Jupiter-mass gas giants, many bunched up against their star on orbits far shorter than that of Mercury. We had learnt that our planetary system was not alone in the Galaxy, but small rocky worlds on temperate orbits might still have been rare.

Based on just six weeks of data, these first discoveries from Kepler were also hot Jupiters; the easiest planets to find due to their large size and swiftly repeating signature as they zipped around the star. But expectations were high that this would be just the beginning.

“We expected Jupiter-size planets in short orbits to be the first planets Kepler could detect,” said Jon Morse, director of the Astrophysics Division at NASA Headquarters at the time the discovery was announced. “It’s only a matter of time before more Kepler observations lead to smaller planets with longer period orbits, coming closer and closer to the discovery of the first Earth analog.”

Morse’s prediction was to prove absolutely right. Now at the end of its life, the Kepler Space Telescope has found 2,343 confirmed planets, 30 of which are smaller than twice the size of the Earth and in the so-called “Habitable Zone”, meaning they receive similar levels of insolation –the amount of solar radiation reaching a given area–to our own planet.

Yet, the question remains: were any of these indeed Earth analogs?

In just a few decades, thanks to Kepler, the Hubble Space Telescope and scores of astronomers at ground-based observatories, we have gone from suspecting the presence of exoplanets to knowing there are more exoplanets than stars in our galaxy. (NASA/Ames Research Station; Jessie Dotson and Wendy Stenzel)

It was a question that Kepler was not equipped to answer. Kepler identifies the presence of a planet by looking for the periodic dip in starlight as a planet passes across the star’s surface.… Read more

The Just-Approved European ARIEL Mission Will Be First Dedicated to Probing Exoplanet Atmospheres

March 29, 2018 / Elizabeth Tasker / 0 Comments

The Ariel space telescope will explore the atmospheres of exoplanets. (Artist impression, ESA)

The European Space Agency (ESA) has approved the ARIEL space mission—the world’s first dedicated exoplanet atmosphere sniffer— to fly in 2028.

ARIEL stands for the “Atmospheric Remote-sensing Infrared Exoplanet Large-Survey mission.” It is a space telescope that can detect which atoms and molecules are present in the atmosphere of an exoplanet.

The mission was selected as a medium class mission in the ESA Cosmic Vision program; the agency’s decadal plan for space missions that spans 2015 – 2025.

One of the central themes for Cosmic Vision is uncovering the conditions for planet formation and the origins of life. This has resulted in three dedicated exoplanet missions within the same decadal plan. ARIEL will join CHEOPS (in the small class mission category) and PLATO (another medium class mission) in studying worlds beyond our own sun.

Yet ARIEL is a different type of telescope from the other exoplanet-focused missions. To understand why, we need to examine what properties we can observe of these distance exo-worlds.

Exoplanet missions can be broadly divided into two types. The first type are the exoplanet hunter missions that search the skies for new worlds.

These are spacecraft and instruments such as the NASA Kepler Space Telescope. Since it launched in 2009, Kepler has been an incredibly prolific planet hunter. The telescope has found thousands of planets, modeled their orbits and told us about the distribution of their sizes.

From Kepler, we have learnt that planet formation is common, that it can occur around stars far different from our own sun, and that these worlds can have a vast range of sizes and myriad of orbits quite unlike our own Solar System.

Current and future (or proposed) space missions with capacities to identify and characterize exoplanets. (NASA,ESA: T. Wynne/JPL, composited by Barbara Aulicino)

However, the information Kepler is able to provide about individual planets is very limited. The telescope monitors stars for the tiny drop in light as the planet crosses (or “transits”) the star’s surface. From this, astronomers can measure the radius of the planet and its orbital period but nothing about the planet’s surface conditions.

The result is a little like knowing the number of students and distribution of grades in a particular school, but having no idea if the student who sits in the third row actually likes math.… Read more

To Understand Habitability, We Need to Return to Venus

February 8, 2018 / Elizabeth Tasker / 0 Comments

This image shows the night side of Venus in thermal infrared. It is a false-color image using data from the Japanese spacecraft Akatsuki’s IR2 camera in two wavelengths, 1.74 and 2.26 microns. Darker regions denote thicker clouds, but changes in color can also denote differences in cloud particle size or composition from place to place. JAXA / ISAS / DARTS / Damia Bouic

“You can feel what it’s like on Venus here on Earth,” said Kevin McGouldrick from the Laboratory for Atmospheric and Space Physics at the University of Colorado, Boulder. “Heat a hot plate until it glows red, place your palm on its surface and then run over that hand with a truck.”

The surface of Venus is a hellish place. Suffocated by a thick atmosphere, pressure on the Venusian surface is 92 times greater than on the surface of Earth. Temperatures sit at a staggering 863°F (462°C), which is sufficient to melt lead.

The longest a spacecraft has survived in these conditions is a mere 127 minutes; a record set by the Russian Venera 13 mission over 35 years ago.

As the brightest planet in the night sky, Venus allured ancient astronomers into naming the world after the Roman mythological goddess of love and beauty. This now seems an ironic choice, but the contrast between distant observation and surface conditions produces an apt juxtaposition for exoplanets.

The comparison has led to an article in Nature Geoscience by McGouldrick and a nine author white paper advising on astrobiology strategy for the National Science Foundation. The conclusion of both publications echoes the irony of Venus’s name: we need to return to the inferno of Venus to understand habitable worlds.

A portion of western Eistla Regio is displayed in this three-dimensional perspective view of the surface of Venus. Synthetic aperture radar data from the spacecraft Magellan is combined with radar altimetry to develop a three-dimensional map of the surface. Rays cast in a computer intersect the surface to create a three-dimensional perspective view. The simulated hues are based on color images recorded by the Soviet Venera 13 and 14 spacecraft. The image, a frame from a video released in 1991, was produced at NASA’s JPL Multimission Image Processing Laboratory.

In the last 25 years, scientists have discovered over 3,500 extrasolar planets. The vast majority of these worlds have not been imaged directly, but are detected by tiny influences on their host star.… Read more

Artificial Intelligence Has Just Found Two Exoplanets: What Does This Mean For Planet Hunting?

December 18, 2017 / Elizabeth Tasker / 0 Comments

There are now two known eight-planet solar systems in the galaxy. Artificial intelligence was used to comb through the data collected three years ago by the Kepler Space Telescope and its algorithms helped find Kepler 90-1, the eight planet in that solar system. (NASA)

The media was abuzz last week with the latest NASA news conference. A neural network — a form of artificial intelligence or machine learning — developed at Google had found two planets in data previously collected by NASA’s prolific Kepler Space Telescope. It’s a technique that could ultimately track-down our most Earth-like planets.

The new exoplanets orbit stars already known to host planetary systems, Kepler-90 and Kepler-80. While both are only slightly larger than the Earth, their two-week orbits makes these worlds too hot to be considered likely candidates for hosting life. Moreover, the systems are thousands of light years away, putting the planets out of range of atmospheric studies that could test their habitability.

With over 3,500 exoplanets already discovered, you might be forgiven for finding these additions underwhelming. However, while other planets in the same system have been known about for several years, these two Earth-sized worlds were previously overlooked. The difference is not a new telescope, but an exploration of the data with a different kind of brain.

The Kepler Space Telescope searches for planets using the transit technique; detecting small dips in amount of starlight as the planet passes in front of the star. As planets are much smaller than stars, picking out this tiny light drop is a tricky task. For a Jupiter-sized planet orbiting a star like our Sun, the decrease in brightness is only about 1%. For an Earth-sized planet, the signal becomes so small it is right on the edge of what Kepler is able to detect. This makes their dim wink extremely difficult to spot in the data.

Kepler Space Telescope collected data on planet transits around distant stars for four years, and the information has provided — and will continue providing — a goldmine for planet hunters. A severe malfunction in 2013 had robbed Kepler of its ability to stay pointed at a target without drifting off course, but the spacecraft was stabilized and readjusted to observe a different set of stars. (NASA)

The discovery paper published in the Astronomical Journal combined the expertise of Christopher Shallue from Google’s artificial intelligence project, Google Brain, and Andrew Vanderburg, a NASA Sagan Postdoctoral Fellow and astronomer at the University of Texas at Austin.… Read more

Can You Overwater a Planet?

November 22, 2017 / Elizabeth Tasker / 0 Comments

Water worlds, especially if they have no land on them, are unlikely to be home to life, or at least life we can detect. Some of the basic atmospheric and mineral cycles that make a planet habitable will be absent. Cool animation of such a world. (NASA)

Wherever we find water on Earth, we find life. It is a connection that extends to the most inhospitable locations, such as the acidic pools of Yellowstone, the black smokers on the ocean floor or the cracks in frozen glaciers. This intimate relationship led to the NASA maxim, “Follow the Water”, when searching for life on other planets.

Yet it turns out you can have too much of a good thing. In the November NExSS Habitable Worlds workshop in Wyoming, researchers discussed what would happen if you over-watered a planet. The conclusions were grim.

Despite oceans covering over 70% of our planet’s surface, the Earth is relatively water-poor, with water only making up approximately 0.1% of the Earth’s mass. This deficit is due to our location in the Solar System, which was too warm to incorporate frozen ices into the forming Earth. Instead, it is widely — though not exclusively — theorized that the Earth formed dry and water was later delivered by impacts from icy meteorites. It is a theory that two asteroid missions, NASA’s OSIRIS-REx and JAXA’s Hayabusa2, will test when they reach their destinations next year.

But not all planets orbit where they were formed. Around other stars, planets frequently show evidence of having migrated to their present orbit from a birth location elsewhere in the planetary system.

One example are the seven planets orbiting the star, TRAPPIST-1. Discovered in February this year, these Earth-sized worlds orbit in resonance, meaning that their orbital times are nearly exact integer ratios. Such a pattern is thought to occur in systems of planets that formed further away from the star and migrated inwards.

Trappist-1 and some of its seven orbiting planets. They would have been sterilized by high levels of radiation in the early eons of that solar system — unless they were formed far out and then migrated in. That scenario would also allow for the planets to contain substantial amounts of water. (NASA)

The TRAPPIST-1 worlds currently orbit in a temperate region where the levels of radiation from the star are similar to that received by our terrestrial worlds.… Read more

Phobos and Deimos: Captured Asteroids or Cut From Ancient Mars?

June 16, 2017 / Elizabeth Tasker / 0 Comments

Illustration of Mars with its two moons, Phobos and Deimos. (NASA/JPL-Caltech/Malin Space Science Systems/Texas A&M Univ.)

The global success rate for sending missions to land on the moons of Mars has hardly been impressive — coming in at zero out of three attempts. They were all led by the Russian (or former Soviet) space agencies, in collaboration with organizations ranging from the Chinese and Bulgarian space agencies to the Paris Observatory and the U.S. Planetary Society.

Now the Japanese space agency JAXA has approved its own mission to Phobos and Deimos, scheduled to launch from the Tanegashima Space Center in September 2024.

The Martian Moons eXploration (MMX) spacecraft will arrive at Mars in August 2025 and spend the next three years exploring the two moons and the environment around Mars. During this time, the spacecraft will drop to the surface of one of the moons and collect a sample to bring back to Earth. Probe and sample are scheduled to return to Earth in the summer of 2029.

Mars takes its name from the god of war in ancient Greek and Roman mythology. The Greek god Ares became Mars in the Roman adaptation of the deities. Mars’s two moons are named for Phobos and Deimos; in legend the twin sons of Ares who personified fear and panic.

Today, what the moons together personify is a compelling mystery, one regarding how in reality they came to be.

Both Martian moons are small, with Phobos’s average diameter measuring 22.2km, while the even smaller Deimos has an average size of just 13km. This makes even Phobos’s surface area only comparable to that of Tokyo. Their diminutive proportions means that the moons resemble asteroids, with irregular structures due to their gravity being too weak to pull them into spheres.

This leads to the question that has inspired a long-running debate: Were Phobos and Deimos formed during an impact with Mars, or are they asteroids that have been captured by Mars’s gravity?

Phobos and Deimos, photographed by the Mars Reconnaissance Orbiter. (NASA/JPL)

Our own Moon is thought to have been created when a Mars-sized body slammed into the early Earth. Debris from the collision was thrown into the Earth’s orbit where is coalesced into our only natural satellite.

A similar scenario is possible for Phobos and Deimos. In the late stages of our solar system’s formation, giant impacts such as the one that struck the Earth were relatively common.… Read more

Many Worlds