Space News & Blog Articles

In the past decade, the discovery of extrasolar planets has accelerated immensely. To date, 4,424 exoplanets have been confirmed in 3,280 star systems, with another 7,453 awaiting confirmation. So far, most of these planets have been gas giants, with about 66% being similar to Jupiter or Neptune, while another 30% have been giant rocky planets (aka. “Super-Earths). Only a small fraction of confirmed exoplanets (less than 4%) have been similar in size to Earth.

However, according to new research by astronomers working at NASA Ames Research Center, it is possible that Earth-sized exoplanets are more common than previously thought. As they indicated in a recent study, there could be twice as many rocky exoplanets in binary systems that are obscured by the glare of their parent stars. These findings could have drastic implications in the search for potentially habitable worlds since roughly half of all stars are binary systems.

For the sake of their study, the research team examined 517 exoplanet-hosting stars that were identified by NASA’s Transiting Exoplanet Survey Satellite (TESS) during its three years in operation. When compared to data from the twin telescopes of the international Gemini Observatory and the WIYN 3.5-meter Telescope at Kitt Peak National Observatory, they found that over 100 of these stars likely had a binary companion.

The paper that describes their findings has been accepted for publication in the Astronomical Journal. Dr. Kathryn Lester, a postdoctoral researcher at NASA Ames Research Center, led the research effort with the assistance of colleagues from NASA Ames, the U.S. Naval Observatory, the NASA Exoplanet Science Institute, the NSF’s National Optical-Infrared Astronomy Research Laboratory (NOIRLab), the Lowell Observatory, as well as Georgia State and Standford University.

The Trouble with Transits

To date, the vast majority of confirmed exoplanets (roughly 75%) have been discovered using the Transit Method (aka. Transit Photometry). This consists of observing stars for periodic dips in their brightness, which can be the result of a planet passing in front of their face (transiting) relative to the observer. Like its predecessor, Kepler, TESS relies on the Transit Method to determine the presence of exoplanet systems around thousands of stars at any given time.

“The best laid plans of mice and men often go awry” – this famous paraphrase of Scottish poet Robert Burns sometimes sums up human ingenuity.  That is exactly what happened when a county in Washington State decided to replace all of its county-owned streetlights with LEDs at least partially in an effort to combat light pollution.  New research shows that they actually made the light pollution worse.

Dr. Li-Wei Hung and her colleagues at the National Park Service recently released a paper currently available on arXiv that details work that they did to monitor the night sky both before and after Chelan County replaced their streetlights with LEDs.

Map of Chelan County and where its street lights are located.
Credit – Hung et al.

Chelan County is located in the north-central part of the state and serves as a gateway to several outdoor recreational areas nearby, including North Cascades National Park.  Given this interest in the outdoors, less light pollution would seem like a benefit to stargazing hoping to catch a glimpse of the Milky Way.

So the county decided to replace all 3,693 of the county-owned streetlights (60% of the total outdoor streetlights in Chelan County) with “full cutoff” light emitting diodes for bulbs.  About 80% of these new LEDs were “3000K” or “warm white light”, while the other 20% were slightly brighter “4000K” bulbs that were installed to meet lighting requirements set by the Washington State Department of Transportation.

Last year we reported on how the Roman Space Telescope’s backers hoped it would be able to detect rogue planets using a technique called “microlensing”.  Now, a team led by Iain McDonald, then at the University of Manchester, beat them to the punch by finding a few examples of Earth-sized rogue planets using data from an already aging space telescope – Kepler.

Both collecting and analyzing the data used in the study wasn’t easy though.  Kepler embarked on a two-month campaign in 2016 that had it looking at millions of stars located near the center of the Milky Way every 30 minutes.  Even with that much data, picking the signal from the noise was difficult.  

They are difficult because microlensing is exhibited by tiny fluctuations in the light of stars when an object passes in front of them.  According to Dr. McDonald, about every one in a million stars in the galaxy is subject to microlensing at any point in time.  So of the million of stars towards the center of the Milky Way, several could be undergoing microlensing right now.

Those events can last anywhere from minutes to days, as it depends on the difference between the foreground object and background stars, as well as the weight of the foreground object.  Of the many microlensing events that take place facing the galactic core, only approximately 1% of them are caused by rogue planets, and the signals from those events are much smaller when compared to microlenses caused by foreground stars.

Despite all the difficulties in collecting data with an old telescope, siphoning through all the additional data and background noise, and trying to differentiate between events caused by stars and those caused by planets, Dr. McDonald and his co-author, Eamonn Kerins were able to find 27 candidates for microlensing events. Of those, four could have potentially been caused by Earth-sized rogue planets.  

Even though the Cassini mission at Saturn ended nearly four years ago, data from the spacecraft still keeps scientists busy. And the latest research using Cassini’s wealth of data might be the most enticing yet.

Researchers say they’ve detected methane in the plumes of Saturn’s icy moon Enceladus. The process for how the methane is produced is not known at this time, but the study suggests that the surprisingly large amount of methane found are likely coming from activity at hydrothermal vents present on Enceladus’s interior seafloor. These vents could be very similar those found in Earth’s oceans, where microorganisms live, feed on the energy from the vents and produce methane in a process called methanogenesis.

“We are not concluding that life exists in Enceladus’ ocean,” said Régis Ferrière, an associate professor at the University of Arizona, and one of the study’s two lead authors.  “Rather, we wanted to understand how likely it would be that Enceladus’ hydrothermal vents could be habitable to Earthlike microorganisms. Very likely, the Cassini data tell us, according to our models.”

One of the biggest surprises of the 13-year Cassini mission came in Enceladus, a tiny moon with active geysers at its south pole. At only about 310 miles (500 km) in diameter, the bright and ice-covered Enceladus should be too small and too far from the Sun to be active. Instead, this little moon is one of the most geologically dynamic objects in the Solar System.

Stunning backlit images of the moon from Cassini’s camera show plumes erupting in Yellowstone-like geysers, emanating from tiger-stripe-shaped fractures in the moon’s surface. The discovery of the geysers took on more importance when Cassini later determined the plumes contained water ice and organics. Since life as we know it relies on water, this small but energetic moon has been added to the short list of possible places for life in our Solar System. 

A close pass of Comet Wirtanen in 2018 offered researchers an unprecedented opportunity.

Comets are full of surprises. Not only do they often under- or very occasionally over- perform versus expectations, but they also offer a glimpse of the remnants of the very early solar system. In December 2018, astronomers had an unprecedented opportunity to study one of these relics of the early solar system up close as Comet 46P/Wirtanen sped by Earth just 30 times the Earth-Moon distance (7.1 million miles away) on its closest passage for this century.

Discovered by astronomer Carl A. Wirtanen in 1948, short period Comet 46P Wirtanen orbits the Sun every 5.4 years, on a path that takes it from a perihelion 1.06 AU from the Sun to an aphelion of 5.13 AU, just outside the perihelion of Jupiter.

The 2018 approach past Earth for the comet was an especially favorable one, and this time, astronomers at the W.M. Keck Observatory on Maunakea, Hawai’i were ready. Keck’s Near Infrared Spectrograph (NIRSPEC) just received a major upgrade, featuring more pixels and higher sensitivity, an upgrade that would see first light obtaining spectra of the comet.

And the results, recently published in The Planetary Science Journal were a spectacular success. Not only did the team classify a list of key compounds seen out-gassing from Comet Wirtanen, but they discovered a high alcohol ratio for the comet, along with an anomalous heating mechanism at play.