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Space News Update — March 31, 2020 —
Contents
In the News
Story 1:
NASA Selects Mission to Study Causes of Giant Solar Particle Storms
Story 2:
Are the Gaps in These Disks Caused by Planets?
Story 3:
Comet ATLAS: Will It Become a Naked-Eye Object?
Departments
The Night Sky
ISS Sighting Opportunities
NASA-TV Highlights
Space Calendar
Food for Thought
Space Image of the Week
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1. NASA Selects Mission to Study Causes of Giant Solar Particle Storms
A new NASA mission called SunRISE will study what drives solar particle storms – giant surges of solar particles that erupt
off of the Sun – as depicted in this illustration. Understanding how such storms affect interplanetary space can help
protect spacecraft and astronauts. Credits: NASA
NASA has selected a new mission to study how the Sun generates and releases giant space weather storms –
known as solar particle storms – into planetary space. Not only will such information improve understanding of
how our solar system works, but it ultimately can help protect astronauts traveling to the Moon and Mars by
providing better information on how the Sun’s radiation affects the space environment they must travel
through.
The new mission, called the Sun Radio Interferometer Space Experiment (SunRISE), is an array of six
CubeSats operating as one very large radio telescope. NASA has awarded $62.6 million to design, build and
launch SunRISE by no earlier than July 1, 2023.
NASA chose SunRISE in August 2017 as one of two Mission of Opportunity proposals to conduct an 11-month
mission concept study. In February 2019, the agency approved a continued formulation study of the mission
for an additional year. SunRISE is led by Justin Kasper at the University of Michigan in Ann Arbor and managed
by NASA’s Jet Propulsion Laboratory (JPL) in Pasadena, California.
"We are so pleased to add a new mission to our fleet of spacecraft that help us better understand the Sun, as
well as how our star influences the space environment between planets," said Nicky Fox, director of NASA's
Heliophysics Division. "The more we know about how the Sun erupts with space weather events, the more we
can mitigate their effects on spacecraft and astronauts."
The mission design relies on six solar-powered CubeSats – each about the size of a toaster oven – to
simultaneously observe radio images of low-frequency emission from solar activity and share them via NASA’s
Deep Space Network. The constellation of CubeSats would fly within 6 miles of each other, above Earth's
atmosphere, which otherwise blocks the radio signals SunRISE will observe. Together, the six CubeSats will
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create 3D maps to pinpoint where giant particle bursts originate on the Sun and how they evolve as they
expand outward into space. This, in turn, will help determine what initiates and accelerates these giant jets of
radiation. The six individual spacecraft will also work together to map, for the first time, the pattern of
magnetic field lines reaching from the Sun out into interplanetary space.
NASA's Missions of Opportunity maximize science return by pairing new, relatively inexpensive missions with
launches on spacecraft already approved and preparing to go into space. SunRISE proposed an approach for
access to space as a hosted rideshare on a commercial satellite provided by Maxar of Westminster, Colorado,
and built with a Payload Orbital Delivery System, or PODS. Once in orbit, the host spacecraft will deploy the six
SunRISE spacecraft and then continue its prime mission.
Missions of Opportunity are part of the Explorers Program, which is the oldest continuous NASA program
designed to provide frequent, low-cost access to space using principal investigator-led space science
investigations relevant to the Science Mission Directorate’s (SMD) astrophysics and heliophysics programs. The
program is managed by NASA’s Goddard Space Flight Center in Greenbelt, Maryland, for SMD, which conducts
a wide variety of research and scientific exploration programs for Earth studies, space weather, the solar
system and universe.
Credit: NASASPAceflight.com
Source: NASA Return to Contents
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2. Are the Gaps in These Disks Caused by Planets?
The column on the left shows gas distribution in five of the circumstellar debris disks in the study. On the right are
measurements for gas in those disks in different velocity channels. Those images show “velocity kinks.” Image Credit: C.
Pinte et al, 2020.
Astronomers like observing distant young stars as they form. Stars are born out of a molecular cloud, and once
enough of the matter in that cloud clumps together, fusion ignites and a star begins its life. The leftover material
from the formation of the star is called a circumstellar disk.
As the material in the circumstellar disk swirls around the now-rotating star, it clumps up into individual planets. As
planets form in it, they leave gaps in that disk. Or so we think.
One of the most observed young stars is called HL Tauri. It’s in the constellation Taurus and is about 450 light years
away. The Atacama Large Millimeter Array (ALMA) captured a well-known image of HL Tauri in 2014. That image is
the sharpest image ever taken by ALMA.
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Since then, astronomers have observed other young stars, and also found gaps in their disks. Note that ALMA, as its
name tells us, is not a visible light telescope. There’s so much gas and dust in circumstellar disks that visible light is
useless for studying them. ALMA observes in wavelengths of light between infrared and radio waves, so it can see
into the swirling disk of gas and dust.
A new study looked at 18 young stars and their disks, and found evidence that 8 of those stars have what they call
“velocity kinks” that may signal the presence of young, still-forming planets. The study is titled “Nine Localized
Deviations from Keplerian Rotation in the DSHARP Circumstellar Disks: Kinematic Evidence for Protoplanets Carving
the Gaps.” Lead author of the study is Christophe Pinte of Monash University, Australia, and the University of
Grenoble Alpes, France). The paper is published in The Astrophysical Journal Letters.
Though astronomers can see the gaps in circumstellar disks, they can’t see the planets. After years of trying with
some of the world’s best telescopes, astronomers have only directly imaged a single exoplanet in a gap around one
star. So even though it might seem obvious that baby planets are responsible, and there’s really no other way they
could form, it’s still an unproven theory. This new study helps make the case that at least some of the observed
gaps in circumstellar disks are caused by planets.
This study used data from the Disk Substructures at High Angular Resolution (DSHARP) project. DSHARP uses ALMA
to study nearby bright circumstellar disks (also called protoplanetary disks). According to the website, DSHARP is
“designed to assess the prevalence, forms, locations, sizes, and amplitudes of small-scale substructures in the
distributions of the disk material and how they might be related to the planet formation process.”
There are other candidate explanations for the gaps in the disks. One is snow lines, or frost lines. In a circumstellar
debris disk, a frost line is the distance from the star where it’s cold enough for volatiles to freeze. This includes not
only water ice, but also ammonia, methane, carbon dioxide and others. Beyond the frost line, these substances
freeze into solid ice grains.
This is the sharpest image ever taken by
ALMA — sharper than is routinely achieved in visible light with the
NASA/ESA Hubble Space Telescope. It shows the
protoplanetary disc surrounding the young
star HL Tauri. With young stars like this one, and CI Tau, the observations reveal
substructures within the disc that have never
been seen before and even show the possible
positions of planets forming in the dark patches within the
system. In this picture the features seen in the
HL Tauri system are labelled. Credit: ALMA
(ESO/NAOJ/NRAO)
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Another possible explanation for these gaps is dust grain sintering. That’s when dust compacts into a solid structure
through heat and pressure, but without melting. A team of scientists explored that idea in this paper.
Other candidates include magneto-hydrodynamic effects, zonal flows, and self-induced dust traps. After the 2014
ALMA image of HL Tauri and its rings, researchers published a number of papers presenting evidence in favor of all
of these possible explanations.
But none of them are as intriguing as the baby planet explanation. And since we now know that most, if not all,
stars host exoplanets, it makes sense.
ALMA doesn’t just take pictures of these young stars and their debris disks. It uses its power to study the gas
distribution in the disks. The image below is from the new study. It compares gas distribution in five disks with
velocity measurements of the same disk.
At the heart of this new study are what’s called “velocity kinks.”
The circumstellar debris disk around HL Tauri and other young stars is largely made of gas, and it’s rotating. As it
rotates, its movement is governed by Keplerian velocity. Keplerian velocity describes how a disk of material should
move when it’s dominated by a massive body at its center. But as the image above shows, there are kinks in the
gas. According to the authors of the new paper, these kinks are evidence of young planets.
From the paper: “Embedded planets perturb the Keplerian gas flow in their vicinity, launching spiral waves at
Lindblad resonances both inside and outside their orbits.”
For at least one of the 20 young stars, the disrupted flow is evidence of large gas giants: “Accurate measurements
of rotation curves revealed, for instance, radial pressure gradients and vertical flows, likely driven by gaps carved in
the gas surface density by Jupiter-mass planets in the disk of HD 163296.”
The study presents a lot of strong evidence in support of protoplanets. But the authors acknowledge that there
could be other causes. One of them is in the data itself.
“Several observational effects and physical mechanisms may produce features in the channel maps that look like
velocity kinks,” the authors say. “The most obvious one is the reconstruction process at low signal-to-noise ratio
that often results in patchy emission that could be mistaken for kinks. We cannot exclude that such artifacts are
present in the DSHARP data…”
But they’ve taken steps to eliminate those errors, and in the end of their paper they make several statements in
summary:
“We found nine localized (channel-specific) velocity perturbations indicative of non-Keplerian motion in
DSHARP observations of 8 protoplanetary disks, out of the 18 selected sources.”
“The presence of embedded planets would naturally explain both the continuum rings and gas velocity
deviations from Keplerian rotation.”
“If planets are indeed responsible for these tentative velocity kinks, they should have masses of the order of
a Jupiter mass.”
In several cases, the authors couldn’t reach definitive conclusions. “… non-detections in other disks or in
other gaps in disks where we detected a kink do not necessarily imply the absence of Jupiter-mass planets.”
So there we have it. This thorough and interesting paper advances the idea that gaps in circumstellar debris disks
are indeed caused by baby planets.
As our observing power grows, and as telescopes like the James Webb and others become operational, the
evidence will likely grow more conclusive.
Source: Universe Today Return to Contents
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3. Comet ATLAS: Will It Become a Naked-Eye Object?
Glowing aqua from carbon and cyanogen emissions and sprouting a 15′ long tail, Comet ATLAS passes near Rho (ρ)
Ursae Majoris on March 22nd. Its coma has ballooned in recent days to 15′ across, which at its current distance is equal
to half the size of the Sun. South is up. Gerald Rhemann
Not since Comet 46P/Wirtanen passed near the Pleiades star cluster in December 2018 has a naked-eye comet
graced the night sky. That may soon change. On December 28, 2019, astronomers with the automated Asteroid
Terrestrial-impact Last Alert System (ATLAS) survey discovered a 20th-magnitude comet in Ursa Major that was
subsequently named Comet ATLAS (C/2019 Y4).
Once a reasonable orbit was determined, Comet ATLAS proved a close match to the Great Comet of 1844 (C/1844
Y1). Both have periods around 4,000 years, approach within 0.25 astronomical unit (a.u.), or 37.4 million
kilometers, of the Sun at perihelion, and are inclined 45° to the ecliptic. These and other orbital similarities were
strong enough to conclude that both objects were fragments of a single, much larger comet that broke apart about
5,000 years ago. For all we know there may be additional fragments en route for future appearances.
Comet ATLAS’s orbit is
tilted 45° with respect to
the plane of the planets.
Closest approach to the
Earth occurs on May
23rd (116.7 million
kilometers), prior to its
May 31st perihelion.
NASA / JPL Horizons
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Because the Great Comet reached 2nd magnitude and grew a 10° tail in January 1845 many of us wondered if its
sibling might be capable of doing the same. The answer is a qualified "yes." But one thing is certain — the comet is
brightening exponentially.
How Bright Will Comet ATLAS Be? While a hundredfold increase in brightness in a month makes a comet
lover's heart palpitate, it could also mean that the comet's volatile ices are rapidly vaporizing as it nears the Sun.
Once those materials are depleted some astronomers expect Comet ATLAS's brightness curve to flatten out, a
common occurrence in comets that have rarely or never come close to the Sun before. Long-period comets that
approach within 1 a.u. of our star have been known to split apart, disintegrate, and disappear. Comet ISON (C/2012
S1) offers a classic example. Shortly before its November 2013 perihelion, the comet crumbled into a cloud of dust
and ice, dashing hopes for the spectacle so many of us had anticipated.
According to NASA’s JPL Horizons the comet could reach magnitude –5, exceeding Venus in brightness at perihelion
on May 31st. Because it will lie 13° southwest of the Sun at that time, it might be possible to see the object in
broad daylight with a properly shielded telescope.
That prediction may be overly optimistic however. In a March 19th notice from the Central Bureau for Astronomical
Telegrams (CBAT), Director Daniel Green applied a formula based on the behavior of previous long-period, Sun-
hugging comets and derived a more conservative peak magnitude of –0.3.
It's good news either way. In both predictions Comet ATLAS will reach naked-eye brightness in mid-May before it's
lost in the solar glare. The JPL Horizons formula predicts a peak magnitude between 1 and 2, while Green
anticipates that number to be between 2 and 3. During the first half of May the comet will appear low in the
evening sky at dusk and early nightfall as it tracks through Perseus. Binoculars should reveal a bright, strongly
condensed coma followed by dust and gas tails pointing away from the Sun. With a little luck we might even see
the tail without optical aid.
After rounding the Sun, Comet ATLAS returns to view around June 15th at dawn in Orion for Southern Hemisphere
skywatchers. Initially glowing at magnitude 3 or 4, the comet will fade quickly — assuming it survives a sizzling
perihelic encounter!
For now, observers in the Northern Hemisphere can follow the comet from Ursa Major through Camelopardalis with
a 6-inch or larger telescope. While visible in binoculars the comet is still quite diffuse and takes some effort to see.
That should change soon.
The comet remains a circumpolar object for much of the U.S. and Europe until about two weeks before perihelion,
when best viewing will be during the early evening hours. If the comet is especially dusty, we'll likely see a more
spectacular tail instead of a bright, spiked fuzz ball. Be hopeful, but as always when it comes to these fragile
objects, temper your expectations.
Source: Sky and Telescope Return to Contents
The chart shows the
position of Comet ATLAS
(C/2019 Y4) through April
24th at 0h UT for the dates
shown. As the comet
approaches perihelion, we'll
be providing updated
charts. Sky & Telescope
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The Night Sky
Friday, April 3
Venus this evening shines right in the left edge of the Pleiades! How soon before the end of twilight can
you first begin to see the little cluster? Bring out your telescope, binoculars, and/or long-focus camera!
Of course they're nowhere near each other, really. Venus this evening is 5.2 light-minutes from us, while
the Pleiades are 440 light-years in the background. That's 150 million times farther. To put that in
perspective: If Venus was a mark on your eyeglasses a half inch from your eye, the Pleiades would be
1,200 miles away in front of it − and 30 miles from side to side.
Saturday, April 4
This evening look right or lower right of the Moon for Regulus, the leading star of Leo. They're about 5°
apart for North America. Above the Moon by a similar distance or a bit more is Algieba, the second-
brightest star after Regulus in the Sickle of Leo The Sickle, a backward question mark, forms the Lion's
stick-figure's head, neck, chest, and front foot.
Source: Sky and Telescope Return to Contents
On the evening of Friday April 3rd, the Pleiades seem to leak out of Venus! As seen from most of North America, they spill to the lower right.
Tuesday, March 31 First-quarter Moon (exactly so at 6:21
a.m. Wednesday morning EDT). The
Moon is in the feet of Gemini. After
dark you'll find Orion far below it,
Procyon off to its left, and brighter
Capella farther to its right. More or
less above the Moon are Gemini's
head stars, Pollux and Castor.
Wednesday, April 1 The Moon after dark shines high below
Pollux. Farther lower left of the Moon
is brighter Procyon. Far below Procyon
is Sirius, the brightest star in the night.
Thursday, April 2 Look left of the Moon this evening for
Pollux and Castor. Farther below the
Moon are Procyon, the Little Dog Star,
and farther down Sirius, the big Dog
Star. The three form a tall, nearly
vertical line.
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ISS Sighting Opportunities (from Denver)
Date Visible Max Height Appears Disappears
Tue Mar 31, 7:57 PM 3 min 13° 10° above NNW 10° above NE
Tue Mar 31, 9:33 PM 1 min 25° 15° above NW 25° above NNW
Wed Apr 1, 8:46 PM 3 min 26° 11° above NNW 24° above NE
Thu Apr 2, 7:59 PM 5 min 20° 10° above NNW 11° above ENE
Thu Apr 2, 9:36 PM < 1 min 34° 22° above WNW 34° above WNW
Fri Apr 3, 8:49 PM 3 min 67° 22° above NW 47° above E
Sighting information for other cities can be found at NASA’s Satellite Sighting Information
NASA-TV Highlights (all times Eastern Time Zone)
April 1, Wednesday
4 p.m. - Video file of the International Space Station Expedition 63 Crew’s pre-launch activities at the
Baikonur Cosmodrome in Kazakhstan (Cassidy, Ivanishin, Vagner; includes material recorded from March
24-April 1) - Johnson Space Center via Baikonur, Kazakhstan (Media Channel)
Watch NASA TV online by going to the NASA website. Return to Contents
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Space Calendar
Mar 31 - Mars Passes 0.9 Degrees From Saturn
Mar 31 - Amor Asteroid 2020 FB4 Near-Earth Flyby (0.031 AU)
Mar 31 - Apollo Asteroid 2020 FA1 Near-Earth Flyby (0.047 AU)
Mar 31 - Atira Asteroid 2013 TQ5 Closest Approach To Earth (0.412 AU)
Mar 31 - 15th Anniversary (2005), Mike Brown, et al's Discovery of Dwarf Planet Makemake
Mar 31 - 1620th Anniversary (400 AD), Comet C/400 F1 Near-Earth Flyby (29.8 Lunar Distance)
Mar 31-Apr 02 - Space Science Week
Apr 01 - Astro2020 Teleconference: Panel on Cosmology
Apr 01 - 60th Anniversary (1960), Tiros 1 Launch (1st Weather Satellite)
Apr 01-07 - Conference: Protostar and Planets VII, Kyoto, Japan
Apr 02 - Apollo Asteroid 2020 FG6 Near-Earth Flyby (0.014 AU)
Apr 02 - Apollo Asteroid 2019 GM1 Near-Earth Flyby (0.023 AU)
Apr 02 - 175th Anniversary (1845), 1st Photo of Sun taken by Louis Fizeau & Leon Foucault
Apr 03 - Mercury Passes 1.4 Degrees From Neptune
Apr 03 - Venus Passes 0.3 Degrees from the Pleiades
Apr 03 - Apollo Asteroid 2020 FK3 Near-Earth Flyby (0.027 AU)
Apr 04 - Apollo Asteroid 2020 FL6 Near-Earth Flyby (0.013 AU)
Apr 04 - Apollo Asteroid 2015 FC35 Near-Earth Flyby (0.027 AU)
Source: JPL Space Calendar Return to Contents
TIROS Weather Satellite
Left, Credit: Smithsonian
Right Credit:
NOAA
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Food for Thought
Planetary Defenders Validate Asteroid Deflection Code
Lawrence Livermore researchers compared results of asteroid deflection simulations to experimental data and found that
the strength model has a substantial effect on momentum transferred.
Planetary defense researchers at Lawrence Livermore National Laboratory (LLNL) continue to validate their ability to
accurately simulate how they might deflect an Earth-bound asteroid in a study that will be published in the April
issue of the American Geophysical Union journal Earth and Space Science.
The study, led by LLNL physicist Tané Remington, also identified sensitivities in the code parameters that can help
researchers working to design a modeling plan for the Double Asteroid Redirection Test (DART) mission in 2021,
which will be the first-ever kinetic impact deflection demonstration on a near-Earth asteroid.
Asteroids have the potential to impact Earth and cause damage at the local to global scale. Humankind is capable of
deflecting or disrupting a potentially hazardous object. However, due to the limited ability to perform experiments
directly on asteroids, understanding how multiple variables might affect a kinetic deflection attempt relies upon
large-scale hydrodynamic simulations thoroughly vetted against relevant laboratory‐scale experiments.
“We’re preparing for something that has a very low probability of happening in our lifetimes, but a very high
consequence if it were to occur,” Remington said. “Time will be the enemy if we see something headed our way
one day. We may have a limited window to deflect it, and we will want to be certain that we know how to avert
disaster. That’s what this work is all about.”
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This study investigated the accuracy of the codes by comparing simulation results to the data from a 1991
laboratory experiment conducted at Kyoto University, where a hyper-velocity projectile impacted a basalt sphere
target.
Remington used an adaptive smoothed-particle hydrodynamics code named Spheral to produce simulation results
that closely resemble the experimental findings. The simulations also helped the researchers identify which models
and material parameters are most important to accurately simulate impact scenarios with a brittle, rocky asteroid.
They found that selection of the strength model and its parameters had a substantial effect on the predicted crater
size and the amount of momentum transferred into the target asteroid. In addition to the strength model, the team
found that simulation results also are sensitive to strain models and material parameters.
These findings highlight the link between having properly validated codes and having the confidence needed to
effectively plan a deflection mission. While no asteroids pose an immediate threat to Earth, LLNL researchers are
collaborating with the National Nuclear Security Administration and NASA in the development of a modeling plan for
the DART mission. These findings will help the team hone its modeling plan for DART.
The DART spacecraft will launch in late July 2021. The target is a binary (two asteroids orbiting each other) near-
Earth asteroid named Didymos that is being intensely observed using telescopes on Earth to precisely measure its
properties before impact. The DART spacecraft will deliberately crash into the smaller moonlet in the binary asteroid
— dubbed Didymoon — in September 2022 at a speed of approximately 6.6 kilometers/second. The collision will
change the speed of the moonlet in its orbit around the main body by a fraction of 1 percent, but this will change
the orbital period of the moonlet by several minutes — enough to be observed and measured using telescopes on
Earth.
“This study suggests that the DART mission will impart a smaller momentum transfer than previously calculated,”
said Mike Owen, LLNL physicist, coauthor on the paper and developer of the Spheral code. “If there were an Earth-
bound asteroid, underestimating momentum transfer could mean the difference between a successful deflection
mission and an impact. It’s critical we get the right answer. Having real world data to compare to is like having the
answer in the back of the book.”
Schematic of the DART mission shows the impact on the moonlet of asteroid (65803) Didymos. Post-impact observations
from Earth-based optical telescopes and planetary radar would, in turn, measure the change in the moonlet’s orbit about
the parent body. Credits: NASA/Johns Hopkins Applied Physics Lab
Source: Lawrence Livermore National Laboratory Return to Contents
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Space Image of the Week
A 212-Hour Exposure of Orion
Image Credit & Copyright: Stanislav Volskiy, Rollover Annotation: Judy Schmidt
Explanation: The constellation of Orion is much more than three stars in a row. It is a direction in space that is rich with impressive nebulas. To better appreciate this well-known swath of sky, an extremely long exposure was taken over many clear nights in 2013 and 2014. After 212 hours of camera time and an additional year of processing, the featured 1400-exposure collage spanning over 40 times the angular diameter of the Moon emerged.
Of the many interesting details that have become visible, one that particularly draws the eye is Barnard's Loop, the bright red circular filament arcing down from the middle. The Rosette Nebula is not the giant red nebula near the top of the image -- that is a larger but lesser known nebula known as Lambda Orionis. The Rosette Nebula is visible, though: it is the red and white nebula on the upper left. The bright orange star just above the frame center is Betelgeuse, while the bright blue star on the lower right is Rigel. Other famous nebulas visible include the Witch Head Nebula, the Flame Nebula, the Fox Fur Nebula, and, if you know just where to look, the comparatively small Horsehead Nebula. About those famous three stars that cross the belt of Orion the Hunter -- in this busy frame they can be hard to locate, but a discerning eye will find them just below and to the right of the image center.
Source: NASA APOD Return to Contents