With Hubble, astronomers use UV light for first time to measure a still-forming planet’s growth rate

In 2018, the exo-planet PDS 70b was observed using the Very Large Array.  It’s discovery… The post With Hubble, astronomers use UV light for first time to measure a still-forming planet’s growth rate appeared first on NASASpaceFlight.com.

With Hubble, astronomers use UV light for first time to measure a still-forming planet’s growth rate

In 2018, the exo-planet PDS 70b was observed using the Very Large Array.  It’s discovery instantly placed it at the top of observation requests and telescope time for one quite profound reason: the exoplanet was still forming.

For the first time, a still-accreting planet had been discovered, providing astrophysicists a unique opportunity to study how planets form with real-time observations.  But one pesky problem existed: PDS 70b was far too close to its parent star for the usual exoplanet observational techniques to allow researchers to measure the planet’s growth rate.

Now, for the first time ever using UV-band observations, a group of astrophysicists working with the Hubble Space Telescope’s Wide Field Camera 3 have produced the first measurement of PDS 70b’s current growth rate.

The exoplanet in question orbits the star PDS 70 — a young, 10 million year old, K5 spectral type, low-mass T Tauri star located approximately 370 light-years from our solar system in the constellation Centaurus.

A 140 AU-wide (1 Astronomical Unit , or AU, is equal to the average distance of Earth from the Sun: approximately 149 million kilometers) accretion disk around the star was confirmed in 2006, with an approximately 65 AU gap in that disk found in 2012.

The gap instantly intensified interest in PDS 70, as large gaps in young star systems’ accretion disks are usually an indication of forming planets according to models of stellar system development.

PDS 70b seen in this image from the Very Large Telescope. The planet stands out as a bright point to the right of the center of the image. (Credit: ESO, VLT, André B. Müller)

In 2018, exoplanet PDS 70b was found in a 119.2 year orbit located approximately 20 AU from its parent star using the Very Large Telescope in Chile. The massive Jupiter-like planet, itself more than five times Jupiter’s mass, was too close to its parent star to be observed in the ways necessary to discern its current accretion (or growth) rate.

“To study this specific planet, it needs UV information,” said Dr. Yifan Zhou, Postdoctoral Fellow, McDonald Observatory, University of Austin and lead author on the new study on PSD 70b’s accretion measurement, in an interview with NASASpaceflight.

“Hubble is basically the only telescope that can do this work” due to the detail and precision of the observations,” noted Dr. Zhou.

Using the orbital Hubble Space Telescope to observe the PDS 70 system gave Zhou et al. their best chance of seeing the exoplanet in the UV wavelength.  However, “the non-ideal part of Hubble compared to ground-based telescopes [is that] Hubble has a very small mirror.  It’s only 2.4 meters.”

The smaller the mirror, the less sharp the image.  To account for this, the team employed multiple techniques — some for the first time with UV observations — to pull the exoplanet from the data while ensuring they were not detecting a false positive.

“One very important concept here, the application we use in this observation is called angular differential imaging.  You take the image with different position angles, and your PSF, the point spread function structure is rotating with the telescope but your planet is staying in the same position,” related Dr. Zhou.

“We can rotate the two images to have their point spread function match with each other, and when we subtract [them] from each other, your astrophysical signal, or planet signal, stays there and you remove all of your contamination from the star.”

“So that’s a very important technique we used here.  It was developed in ground-based observations of exoplanets,” added Dr. Zhou.

Typically, two angular differential imaging positions are used for such observations.  However, for this investigation, 18 different angles were required to gather the needed information. 

To ensure the data didn’t return a false positive, interference showing an exoplanet where there isn’t one, Zhou et al. used artificial signals purposefully added to the images to ensure they were seeing a real exoplanet.   “At the very first stage, we [inserted] an artificial signal that we [knew was] there.  We inserted it into the images to see if after all these types of image processing we [could] recover [it],” said Dr. Zhou.  “And we recovered it, so that gave us additional confidence we were seeing a real signal.”

Observations with Hubble occurred in two main wavelengths used for the final investigation in conjunction with various filters across 18 orbits.  Each orbit included ten, 120 second UV F336W band exposures and nine 20 second F656N (for hydrogen-alpha, or Hα, emission line) exposures using Wide Field Camera 3.

In total, 21,600 seconds of observations in the F336W band and 3,240 seconds of information in the F656N band were collected.  After working with the data, Zhou et al. confirmed the detection of the exoplanet PDS 70b in UV. 

For the first time, the UV information provided a clear look at the current accretion process taking place at PDS 70b.

After its initial discovery, follow-up observations found PDS 70b likely had a circumplanetary disk of material… just as planetary formation models predicted it would.  The new UV investigation shed further light on the exoplanet’s disk, which itself proved useful in determining the processes still governing PDS 70b’s growth.

The Hα emission lines from PDS 70b observed by Zhou et al. clearly showed active accretion as Hα emissions occur as material, following a forming planet’s magnetic field lines, flows into the planet and is heated in the process — creating a hot shock.

Temperatures of hydrogen atoms in the gas and material being pulled into the planet therefore increase to the point where the atoms are excited and their single electron moves from the second to the third energy state.  When the electron falls back to the second energy level, an Hα emission is produced.

However, a puzzling result from the analysis was the final measured accretion rate, which was found to be: M = 1.4 ± 0.2 x 10-8 MJupyr-1Put another way, under its current accretion rate, it would take PDS 70b one million years to accrete 1/100th of Jupiter’s mass.

And that’s lower than super-Jupiter gas giant planet formation models predict.

PDS 70b, seen by Hubble. (Credit: Joseph DePasquale, STScI)

Zhou et al. are quick to caution that their calculations are a snapshot in time.  Additional observation, multi-decade, multi-century observations will reveal if accretion rates fluctuate greatly over time as planets go through growth spurts, so to speak, followed by periods of less active formation or if “Hα production in planetary accretion shocks is more efficient than [previous] models predicted, or [if] we underestimated the accretion luminosity/rate,” noted Zhou et al. in their paper published in April 2021 issue of .

 The team further noted, “By combining our observations with planetary accretion shock models that predict both UV and Hα flux, we can improve the accretion rate measurement and advance our understanding of the accretion mechanisms of gas giant planets.” 

Moreover, as Dr. Zhou related to NASASpaceflight, additional observations will also reveal how much of the circumplanetary disk will accrete to the planet and how much of it will remain to form moons.

“After the planet accretion is finished, there’s leftovers in the circumplanetary disk.  Those materials, they congregate.  Now, in terms of discovering them, my expectation is that it’s very, very challenging.”

Not only is discerning an exomoon around an exoplanet incredibly difficult, alignment is also key.  “We need to have the planet aligned with the star and then the moon aligned with the planet,” related Dr. Zhou.

While there are no confirmed exomoons to date, a few candidates have been proposed, and the potential – as technical advances – that PDS 70b could provide a close-to-home look at exomoon development remains.

To this end, Dr. Zhou looks forward to the pending launch of the James Webb Space Telescope and its 6.5 meter mirror and infrared imaging capability.

“For James Webb, we will have the first opportunity to probe the actual disk that is being accreted onto the planet.  And, actually, PDS 70b is a prime target for multiple James Webb programs that already have the guaranteed time observation.  So [those teams will] observe this planet in multiple wavelengths,” noted Dr. Zhou.

The PDS 70 has two confirmed exoplanets, 70b and 70c, the latter of which was not seen in the data.

(Lead image credit: NASA, ESA, STScI, Joseph Olmsted)

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Ingenuity enters operations demonstration phase as Perseverance team marks initial science returns

Nearly three months after landing on Mars, NASA’s Perseverance mission is marking its initial science… The post Ingenuity enters operations demonstration phase as Perseverance team marks initial science returns appeared first on NASASpaceFlight.com.

Ingenuity enters operations demonstration phase as Perseverance team marks initial science returns

Nearly three months after landing on Mars, NASA’s Perseverance mission is marking its initial science returns from the Martian surface as the Ingenuity helicopter enters its new phase of operational demonstration flights on the Red Planet. 

Ingenuity’s flight will gather information on the surrounding Martian terrain for the mission’s teams to identify science targets for the mobile laboratory.

Ingenuity into new phase

The history-making helicopter known as Ingenuity has now begun a new series of operations on Mars, setting yet another altitude flight record on the Red Planet.

On 7 May, Ingenuity completed its fifth flight, a 129 meter journey south of Wright Brothers Field. After translating to its new location, the craft climbed to 10 meters altitude — a new record — to capture images of the surrounding area.

The flight lasted 108 seconds, commencing at 19:26 UTC / 12:33 local time at Jezero Crater, Mars.

“We bid adieu to our first Martian home, Wright Brothers Field, with grateful thanks for the support it provided to the historic first flights of a planetary rotorcraft,” said Bob Balaram, chief engineer for Ingenuity at the Jet Propulsion Lab (JPL).

Ingenuity crossed millions of kilometers of space and was lowered to the surface of Mars by the Perseverance rover, which relays results from Ingenuity back to Earth and transmits instructions from Earth to Ingenuity.

Ingenuity, seen after landing on 7 May by Perseverance’s Mastcam-Z imager. (Credit: NASA/JPL-Caltech/ASU/MSSS)

The rotorcraft made the first powered, controlled flight by a heavier-than-air flying machine on another planet on 19 April 2021, almost 117 years after the Wright Brothers made their history-making flight on Kill Devil Hill in North Carolina.

During its first flight, the 1.8 kilogram Ingenuity ascended to 3 meters, hovered, rotated, and then landed safely.

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  • The rotorcraft’s first flight lasted 39.1 seconds, as compared to the Wright Flyer’s 12 second flight. As a nod to the Wright Brothers, JPL incorporated a small piece of the Wright Flyer’s actual fabric into Ingenuity itself.

    That piece of fabric has now been involved with the first powered, controlled flight on two planets. Moreover, the “airfield” where Ingenuity first flew, next to the Van Zyl Overlook where Perseverance was parked, was named Wright Brothers Field.

    On Ingenuity’s second flight on 22 April, the electric helicopter rose vertically to 5 meters, flew laterally for 2 meters, made three turns, stayed airborne for 51.6 seconds, and then landed. A few days later, Ingenuity took flight for the third time on 25 April.

    The rotorcraft rose vertically to 5 meters, flew laterally for 50 meters, achieved an airspeed of 2 m/s, and landed safely.

    Ingenuity’s fourth flight was originally planned for 29 April, but its computer failed to change to flight mode and the craft stayed on the ground. After JPL evaluated what happened, the flight was rescheduled for the following day.

    The fourth flight featured a climb to 5 meters and a flight south for 133 meters and then back for a 266 meter round trip. The flight lasted 117 seconds and captured numerous photographs for aerial surveillance of the surrounding landscape. 

    While designed to provide 350 watts for a 90 second flight, Ingenuity’s power system has performed better than expected, along with its other systems.

    An aspect of Ingenuity’s better than expected performance is its rotors’ ability to shake the ever-present Martian dust off of the craft’s solar panels during flight. This ability to keep dust off of the solar panels not only extends Ingenuity’s mission, but could also provide data on future solar panel designs that need to function on the Red Planet.

    With its fifth flight complete, Ingenuity is now at a location known as Airfield B. 

    “The plan forward is to fly Ingenuity in a manner that does not reduce the pace of Perseverance science operations,” said Balaram. “We may get a couple more flights in over the next few weeks, and then the agency will evaluate how we’re doing.”

    “We have already been able to gather all the flight performance data that we originally came here to collect. Now, this new operations demo gives us an opportunity to further expand our knowledge of flying machines on other planets.”


    While Ingenuity has been busy with its flight program, Perseverance has also stayed busy when not needed as a communications platform for the rotorcraft.

    The rover has not only continued system checkouts, but also begun initial science operations and important technology demonstrations applicable to future Mars missions.

    One of the largest successes so far is the MOXIE, or Mars Oxygen In-Situ Resource Utilization Experiment. MOXIE is designed to test the process of converting Martian air (96% carbon dioxide) into oxygen for use by astronauts or as fuel for rockets. 

    On 20 April, MOXIE successfully made 5.4 grams of oxygen in one hour using a solid oxide electrolysis process, enough for 10 minutes of breathable air for an astronaut.

    The MOXIE unit is a 17.1 kilogram box mounted to the front right side of Perseverance. It is about the size of a car battery but is designed to withstand temperatures of 800℃ inherent with the process that converts carbon dioxide to oxygen and carbon monoxide, which will be expelled into the Martian air. 

    Its gold coating also protects Perseverance from damaging heat that might otherwise threaten the other instruments and the rover.

    MOXIE will be run at least nine more times over the next Martian year (two Earth years), and will be tested under different conditions, including time of day and temperature, as it works to produce up to 10 grams of oxygen per hour. 

    The data gathered will inform the design and operation of larger units that will have to process Martian air and regolith into products such as breathable air, water, and rocket fuel for future missions.

    Future oxygen-generating devices will need to be up to one ton in mass to produce much larger quantities of oxygen, most of which would become liquid oxidizer for future rockets that plan to launch from the Martian surface.

    Another technology demonstrator that has functioned well during the first months of Perseverance’s mission is the Mars Environmental Dynamics Analyzer, or MEDA. MEDA is an automated weather station that has been gathering daily reports on dust particle concentration and size as well as surface radiation, wind speed and direction, temperature, air pressure, and humidity. 

    Weather reports will be critical for future crewed missions at Mars so astronauts can be aware of hazards that could impact their mission. Local weather data from MEDA can also be used with global climate and weather data being collected from the Al-Amal orbiter from the United Arab Emirates to form a more complete picture of Mars’ weather and climate dynamics.

    With the primary science phase of Perseverance’s mission beginning in earnest, the rover will now bring its science instruments to bear on the region where it currently resides.

    The area near the landing site is believed to contain mudstones from the middle of Jezero Crater’s ancient lake. The first surface samples will be taken from Perseverance’s current general location before the rover departs.

    Overall, Perseverance will trek toward the ancient river delta in Jezero Crater, traversing different geologic terrain and gathering data to help decode Martian geological history as well as its ancient habitability.

    (Lead image: Perseverance selfie with Ingenuity on the Martian surface. Credit: NASA/JPL)

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