Space News Update - July 10, 2020- Contents
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Space News Update
— July 10, 2020 —
Contents
In the News
Story 1:
NASA's InSight Flexes Its Arm While Its 'Mole' Hits Pause
Story 2:
The Collective Power of The Solar System’s Dark, Icy Bodies
Story 3:
Comet NEOWISE Delights
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's InSight Flexes Its Arm While Its 'Mole' Hits Pause
In his logbook, German Aerospace Center’s (DLR) Instrument Lead Tilman Spohn who is back in Berlin since
April and communicating with JPL via the web, gives us the latest updates regarding the InSight mission and
our HP3 instrument - the 'Mole' - which will hammer into the Martian surface.
Logbook entry 7 July 2020
Hammering on Sol 557. At the time of the jumping, the tether had stopped moving. Credit: NASA/JPL-Caltech
On Saturday 20 June 2020 (Sol 557 on Mars), the team completed the 'Free Mole Test' announced in my
previous blog post. The result was not quite what we had optimistically hoped for, but was also not entirely a
surprise. The 'Mole' started bouncing in place after making some progress without direct support from the
scoop on 13 June (Sol 550).
We have no direct observations of the Mole's movement or measurements of its progress. Rather, we judge
this from the motion of the tether, or more precisely, from the apparent motion of features on the tether with
respect to the background. The images clearly show that the tether moved back and forth and eventually
stopped altogether, suggesting that the Mole did not dig further down on its own.
The 'Free Mole Test' had already started on the previous Saturday, 13 June (Sol 550), but the evidence at that
time for the Mole progressing downward during 125 hammer strokes was too ambiguous to be readily
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accepted. The scoop initially went down pushing on the back-cap of the Mole and was further pressed into the
sand by the arm. In the middle of the video clip, the scoop stopped moving and the dust particles in the scoop
came to rest while the tether kept moving to the right by a few millimeters. This clearly suggested that the
Mole had moved away from the scoop and had progressed downwards on its own. The tiltmeter showed the
Mole becoming somewhat more upright, which is supporting evidence, and the short-period seismometer
showed a change in the frequency characteristics of the recorded hammer signal. The tether apparently
reversed motion a few frames later, before going on to move to the right. It then made a very small move to
the left again before it finished while moving forward. A careful analysis of the images showed that the net
forward motion of the tether (and the Mole?) was two to three millimeters. The integrated motion may have
been three to five times as much!
When the team analyzed the images on the following Monday, they were pleased to see the Mole moving
forward but agreed that at least another hammering cycle was required before we would be willing to
conclude that the Mole was in the ground deep enough to dig on its own. 'Dig on its own' is admittedly not
quite technically accurate, as we were still aiming to provide indirect support by pressing the scoop onto the
surface, thereby intending to increase the pressure on the Mole and the friction on its hull. Of course, we could
not say how much we helped the Mole that way as we do not know the mechanical properties of the duricrust
well enough.
On Sunday 21 June, when we looked at the images that had been sent to Earth after the hammering session
on Saturday (Sol 557, 150 hammer strokes), we had to conclude that having the Mole two to three
centimeters deeper in and below the surface was not providing the necessary friction, even when helped with
pushing on the regolith. The tether moved back and forth and then to the left, reversing much of its forward
progress from Sol 550. In the middle of the movie, one can see that the dust particles resumed moving. Two
particles seem to even be jumping up some centimeters. But on closer inspection, one can see them rather
moving forward from the interior of the scoop in several slides. The moving dust particles imply that the Mole
had backed up again and was tapping on the flat side of the scoop from below.
This result of the 'Free Mole Test' was, of course, not quite what we had hoped for, but we cannot say that it
came as a complete surprise. After all, we are continuing to fight against the missing friction on the Mole hull.
The test supports our earlier conclusion that the cohesive duricrust is unusually thick – at least based on what
we previously knew about Mars – and that it must be quite rigid. From the Mole's first backing out (on Sol
322) and the observation that it stopped when it was 20 centimeters out of the ground, some of us (including
myself) estimated that the duricrust was 20 centimeters thick (the Mole’s 40-centimetre length minus the 20
centimeters that it had backed out). The present observations at least don’t invalidate that conclusion.
What are our next plans?
First of all, let me say that the team continues to be determined, although we appreciate that the task is not
likely to become easier. We have, of course, made a plan for this outcome of the 'Free Mole Test'. The plan
calls for retracting the arm and stereo imaging the pit with the Mole in its interior. We will be interested to see
how deep in the Mole really is (it should be a centimeter or so below the surface), whether the morphology of
the pit has changed and whether the sand that we had seen in the pit is still there or whether the pit has been
drained by the hammering action.
Depending on what the imaging reveals, we plan to see whether or not we can move enough sand into the pit
to provide the necessary friction, likely aided by pushing on the sand pile using the scoop to provide additional
pressure (see the sketch below). This will be different from pushing on the duricrust surface because the sand
has no rigidity and can transfer the force more readily. The scoop will, in addition, guard against the Mole
backing out.
3 of 15
Sketch of the assumed situation in the pit before and after filling the pit as is presently being discussed by the team.
During Sols 550 and 557, a large fraction of the pit was empty (left). The stress provided by the push on the regolith with
the scoop had to be transferred through the duricrust around the pit to the Mole. Because the pressure generated by the
scoop widens and decreases in amplitude with depth, not more than about 35 percent of the load was likely acting on the
Mole at a depth equivalent to one scoop width that is 7 centimeters. If the duricrust is very rigid, this value could be
significantly smaller. In addition, approximately 20 percent of the length of the Mole was without any friction. Filling the
pit with sand (right) can provide friction to the entire hull and the load can be transferred through the sand filling much
more effectively. Credit: DLR
Filling the pit will not be an easy task and may take quite some time. (This is the reason for conducting the
'Free Mole Test' without prior filling of the pit.) A preliminary estimate before the recent pushing and
hammering suggested a required volume of 300 cubic centimeters of sand, equivalent to a scrape (or a
number of scrapes) with the seven-centimeters-wide scoop for the entire 40 centimeters, assuming that the
sand layer is one centimeter thick, as suggested by the images.
The team will take a break now to discuss all the issues at hand and make the arm available for other scientific
activities. If all goes well, we expect to be back in August.
Source: DLR and NASA Return to Contents
4 of 15
2. The Collective Power of The Solar System’s Dark, Icy Bodies
Scientists have long
struggled to explain
the existence of the
solar system's
"detached objects,"
which have orbits
that tilt like seesaws
and often cluster in
one part of the
night sky. (Credit:
Steven
Burrows/JILA)
The outermost reaches of our solar system are a strange place—filled with dark and icy bodies with nicknames like
Sedna, Biden and The Goblin, each of which span several hundred miles across.
Two new studies by researchers at the University of Colorado Boulder may help to solve one of the biggest
mysteries about these far away worlds: why so many of them don’t circle the sun the way they should.
The orbits of these planetary oddities, which scientists call “detached objects,” tilt and buckle out of the plane of the
solar system, among other unusual behaviors.
“This region of space, which is so much closer to us than stars in our galaxy and other things that we can observe
just fine, is just so unknown to us,” said Ann-Marie Madigan, an assistant professor in the Department of
Astrophysical and Planetary Sciences (APS) at CU Boulder.
Some researchers have suggested that something big could be to blame—like an undiscovered planet, dubbed
“Planet 9,” that scatters objects in its wake.
But Madigan and graduate student Alexander Zderic prefer to think smaller. Drawing on exhaustive computer
simulations, the duo makes the case that these detached objects may have disrupted their own orbits—through tiny
gravitational nudges that added up over millions of years. The findings, Madigan said, provide a tantalizing hint to
what may be going on in this mysterious region of space.
“We’re the first team to be able to reproduce everything, all the weird orbital anomalies that scientists have seen
over the years,” said Madigan, also a fellow at Joint Institute for Laboratory Astrophysics (JILA). “It’s crazy to think
that there’s still so much we need to do.”
The team published its results July 2 in The Astronomical Journal and last month in The Astronomical Journal
Letters.
Power to the asteroids
The problem with studying the outer solar system, Madigan added, is that it’s just so dark.
“Ordinarily, the only way to observe these objects is to have the sun’s rays smack off their surface and come back
to our telescopes on Earth,” she said. “Because it’s so difficult to learn anything about it, there was this assumption
that it was empty.”
She’s one of a growing number of scientists who argue that this region of space is far from empty—but that doesn’t
make it any easier to understand.
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Just look at the detached objects. While most bodies in the solar system tend to circle the sun in a flat disk, the
orbits of these icy worlds can tilt like a seesaw. Many also tend to cluster in just one slice of the night sky, a bit
similar to a compass that only points north.
A rogue's gallery of the
largest known objects
in the solar system
beyond the orbit of
Neptune. (Credit: CC
Photo via Wikimedia
Commons)
Madigan and Zderic wanted to find out why. To do that, they turned to supercomputers to recreate, or model, the
dynamics of the outer solar system in greater detail than ever before.
“We modeled something that may have once existed in the outer solar system and also added in the gravitational
influence of the giant planets like Jupiter,” said Zderic, also of APS.
In the process, they discovered something unusual: the icy objects in their simulations started off orbiting the sun
like normal. But then, over time, they began to pull and push on each other. As a result, their orbits grew wonkier
until they started to resemble the real thing. What was most remarkable was that they did it all on their own—the
asteroids and minor planets didn’t need a big planet to throw them for a loop.
“Individually, all of the gravitational interactions between these small bodies are weak,” Madigan said. “But if you
have enough of them, that becomes important.”
Earth times 20
Madigan and Zderic had seen hints of similar patterns in earlier research, but their latest results provide the most
exhaustive evidence yet.
The findings also come with a big caveat. In order to make Madigan and Zderic’s theory of “collective gravity” work,
the outer solar system once needed to contain a huge amount of stuff.
“You needed objects that added up to something on the order of 20 Earth masses,” Madigan said. “That’s
theoretically possible, but it’s definitely going to be bumping up against people’s beliefs.”
One way or another, scientists should find out soon. A new telescope called the Vera C. Rubin Observatory is
scheduled to come online in Chile in 2022 and will begin to shine a new light on this unknown stretch of space.
“A lot of the recent fascination with the outer solar system is related to technological advances,” Zderic said. “You
really need the newest generation of telescopes to observe these bodies.”
Source: University of Colorado, Boulder Return to Contents
6 of 15
3. Comet NEOWISE Delights
Debra Ceravolo captured this stunning portrait of Comet NEOWISE (C/2020 F3) at 4 a.m. on July 8, 2020. She used a
300mm astrograph with a 2700mm focal length to make 160, 1-second stacked exposures. The camera was a SBIG
STFSC8050 one shot color CCD cooled to –20° C. The resulting image is very similar to the view in a modest telescope.
Whatever you do, see this comet. I almost couldn't believe my eyes when I pointed a pair of 10 × 50
binoculars at NEOWISE on July 7th at dawn. OMG. What a sumptuous view! The comet's head, a bright,
yellow pea, sprouted a 3° pale orange tail that arched upwards in a most elegant way. With the naked eye, I
saw a delicate streak of light about 1.5° long with a tiny, star-like coma. The image of a faint meteor jumped
to mind.
Far to the right of NEOWISE, Venus and Aldebaran glimmered in Taurus. Comparing the comet to Aldebaran
(magnitude 0.9), I estimated its brightness at magnitude 1.4, by far the brightest comet to grace our skies
since PanSTARRS (C/2011 L4) in March 2013. And what timing. Just what we needed for the COVID-19 blues!
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NEOWISE survived its July 3rd perihelion in grand form, glowing around magnitude 0, bright enough for some
amateurs to spot it the very same day. It has since faded to magnitude 1.5–2 but its beauty is undiminished.
In fact, the comet has become more extraordinary over the past few nights because it's slowly climbing higher
into a darker sky at the same time that the Moon is waning from full to third quarter. On July 8th the tail
length had doubled to 6° (my estimate), and the comet appeared more obvious to the naked eye than the
morning prior.
I've heard from observers who've observed NEOWISE everywhere from the countryside to Los Angeles. The
news is good. Check out this report from Richard K. Mitchell:
"Here in Albuquerque, the comet was a beautiful sight this morning (July 7). I could see it fairly easy with the
naked eye but not an obvious sight, but very impressive sight in 10×50 binoculars. So I would encourage
anyone in the “burbs” or a smaller city to give it a try."
Or this from Jim Twellman on July 8: "Observed once again from the I-64 overpass at Lake St Louis (an
outlying suburb of St. Louis, MO. ) The comet was easily visible in 10 × 50s but was spectacular in the 15 ×
70s. Estimate 2.0 magnitude."
I don't want to give the impression that NEOWISE is super-easy to see — you still need know where to look —
but once seen you'll return to it with ease. Thank goodness for Capella. Located in the comet's vicinity, this
bright star points the way for novice and amateur observers alike.
Daily positions for Comet NEOWISE are shown for 0h UT July 10-15. To convert to EDT, subtract 4 hours and back up to
the previous date. For example, July 10th at 0h UT = July 9th at 8 p.m. EDT. The comet wraps up its morning
appearance from many locations by mid-month then transitions to an evening object as it zips from Lynx into Ursa Major
(see below). Click on the image for a large chart. Sky & Telescope
Although NEOWISE sits quite low and appears faint at the start of dawn, it quickly brightens as it gains
altitude, offsetting (at least for a time) the intensifying twilight. The best time slot to see the object through
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July 11-12 is from 2 hours to 1 hour before sunrise. With 10 x 50 binoculars I've been able to follow the
comet up to within 40 minutes of sunup.
Through a telescope the colors are even more intense, but the most remarkable sight is the comet's bifurcated
tail — split in two by a dark, U-shaped channel. This feature is also visible in binoculars and photographs, but
far more dramatic in a scope. I use a portable 10-inch f/4.5 Dobsonian at low magnification (48×). Bifurcated
tails appear in comets that are actively producing massive quantities of dust either after a close passage to the
Sun or during a major outburst.
You'll spot Comet NEOWISE in late evening twilight as it tickles the paws of Ursa Major later this month. Daily positions
for Comet NEOWISE are shown for 0h UT July 15-23.
NEOWISE has a prominent dust tail, formed when dust-rich ice vaporizes in the Sun's heat. Micron-size dust
particles scatter sunlight and glow faintly yellow. An enormous amount of dust must concentrate near the false
nucleus because its yellow color is unmistakable.
Dawn comet viewing will be best through about July 18th, with the evening apparition starting about July 12th
and continuing the remainder of the summer. Between July 12–18 you can observe it at both dusk and dawn.
So set your alarm and plan to be out about 2 hours before sunrise (for now). Find a location with a good view
of the northeastern sky, and don't forget to bring binoculars and a camera. Most mobile phone photos will look
grainy, but a basic DSLR on a tripod at ISO 800 with a 2-second exposure will net you an image you'd be
happy to share on social media.
I hope good weather comes your way so you can see Comet NEOWISE while it's still bright. Nothing would
make me happier. By the time I wrapped up my July 7th observation I felt like I was floating on air with light
beams shooting from my fingertips. As the comet vaporizes to create one of the most beautiful sky sights in
years, you may just find that it will melt your heart, too.
Source: Sky and Telescope Return to Contents
9 of 15
The Night Sky
FRIDAY, JULY 10
Jupiter and Saturn rise in twilight this week. Mars
is a fire-beacon high in the southeast in early
dawn, and the Moon joins it there tomorrow and
Sunday mornings July 11th and 12th. On those
same two mornings, Venus passes just 1° from
Aldebaran.
SATURDAY, JULY 11
If you have a dark enough sky, the Milky Way now
forms a magnificent arch high across the whole
eastern sky after nightfall is complete. It runs all
the way from below Cassiopeia in the north-
northeast, up and across Cygnus and the Summer
Triangle in the east, and down past the spout of
the Sagittarius Teapot in the south-southeast.
Meanwhile the Big Dipper, high in the northwest
after dark, is dipping down to "scoop water"
through the evenings of summer and early fall.
Take a look low in the east after about 1 a.m. and
there will be the waning Moon, nearly last quarter,
with brilliant Mars roughly 5° to its upper right (for
Catch Venus in conjunction with Aldebaran in early
North America). By dawn Sunday morning, they dawn Saturday and Sunday mornings. Look twice; it
shine high in the southeast. outshines Aldebaran by 170 times. Venus right now is at
its greatest brilliance as the "Morning Star." And don't
SUNDAY, JULY 12 skip bright Mars much higher in the southeast!
After nightfall, spot Altair in the east-southeast. It's the second-brightest star on the whole eastern side of the
sky, after Vega high to its upper left.
Above Altair by a finger-width at arm's length is little orange Tarazed. A bit more than a fist to Altair's left or
lower left is little Delphinus, the Dolphin, leaping leftward.
Last-quarter Moon (exactly so at 7:29 p.m. EDT). The Moon clears the horizon due east around 1 a.m. tonight,
with Mars now shining some 16° to its upper right.
MONDAY, JULY 13
Starry Scorpius is sometimes called "the Orion of Summer" — for its brightness, its blue-white giant stars, and
its prominent red supergiant (Antares in the case of Scorpius, Betelgeuse for Orion). But Scorpius passes a lot
lower across the southern sky than Orion does, for those of us at mid-northern latitudes. That means it has only
one really good evening month: July.
Catch Scorpius due south soon after dark, before it starts to tilt lower toward the southwest. It's full of deep-sky
objects to hunt out with good charts using a telescope or even binoculars.
TUESDAY, JULY 14
Jupiter is at opposition tonight, opposite the Sun as seen from Earth. For all practical purposes, this is when
Jupiter is its closest and brightest for the year. All this July and August Jupiter is the brightest point in the night,
until Venus rises in the early morning hours.
Source: Sky and Telescope Return to Contents
10 of 15ISS Sighting Opportunities (from Denver)
Date Visible Max Height Appears Disappears
Sat Jul 11, 00:50 AM 1 min 17° 17° above NNE 11° above NNE
Sat Jul 11, 2:25 AM < 1 min 11° 10° above NNW 11° above N
Sat Jul 11, 4:02 AM 1 min 13° 10° above NNW 13° above N
Sun Jul 12, 00:03 AM < 1 min 14° 14° above NE 12° above NE
Sun Jul 12, 1:36 AM 1 min 12° 10° above NW 12° above NNW
Sun Jul 12, 3:15 AM < 1 min 11° 10° above NNW 11° above N
Sun Jul 12, 4:50 AM 3 min 31° 10° above NW 31° above NNE
Sun Jul 12, 11:15 PM < 1 min 17° 17° above NE 11° above NE
Mon Jul 13, 00:48 AM 2 min 15° 10° above NW 15° above NNW
Mon Jul 13, 2:27 AM < 1 min 10° 10° above N 10° above N
Mon Jul 13, 4:03 AM 2 min 21° 11° above NNW 21° above N
Mon Jul 13, 10:22 PM 6 min 76° 10° above SW 11° above NE
Sighting information for other cities can be found at NASA’s Satellite Sighting Information
NASA-TV Highlights (all times Eastern Time Zone)
Regularly Scheduled Programming
NASA TV Schedule for Week of July 6
NASA TV Schedule for Week of July 13
Live Programming
July 10, Friday
11 a.m. - SpaceCast Weekly (All Channels)
July 14, Tuesday
1:10 p.m. - International Space Station Expedition 63 in-flight educational with the Experiment Aircraft
Association Young Eagle Students using pre-record questions and NASA astronauts Bob Behnken and Doug
Hurley (All Channels)
Watch NASA TV online by going to the NASA website. Return to Contents
11 of 15Space Calendar
Jul 10 - Apstar 6D CZ-3B/G2 Launch
Jul 10 - Jilin-1 High Resolution-02A, 02B, 02E (Jilin-1 Gaofen-02A, 02B, 02E) Kuaizhou-11
Launch
Jul 10 - Asteroid 1221 Amor Closest Approach To Earth (0.829 AU)
Jul 10 - Kuiper Belt Object 486958 Arrokoth At Opposition (42.160 AU)
Jul 10 - Webinar: The Emerging Space Nations
Jul 11 - Parker Solar Probe, 3rd Venus Flyby
Jul 11 - Starlink 9 (60)/BlackSky Global 5 & 6 Falcon 9 Launch
Jul 11 - Apollo Asteroid 2020 MU1 Near-Earth Flyby (0.048 AU)
Jul 11 - AMSAT South Africa Space Symposium 2020, Midrnad, South Africa
Jul 12 - Apollo Asteroid 2020 ML Near-Earth Flyby (0.029 AU)
Jul 12 - Amor Asteroid 6569 Ondaatje Closest Approach To Earth (0.262 AU)
Jul 12-16 - Virtual: JpGU-AGU Joint Meeting
Jul 13 - Amor Asteroid 2020 KJ7 Near-Earth Flyby (0.030 AU)
Jul 13 - Amor Asteroid 2009 OS5 Near-Earth Flyby (0.045 AU)
Jul 13 - Online: Space Nuclear Propulsion Technologies Committee Meeting 7 - Industry Perspectives on
NEP/NTP
Jul 13 - Online Roundtable: Science and Astronomy in the Current Social and Economic Situation
Jul 13 - Junior Academy Online Workshop: How to Train Your Demogorgon - The (Pseudo) Science of
Stranger Things
Jul 13-15 - Decadal Survey on Astronomy and Astrophysics 2020 Meeting, Woods Hole, Massachusetts
Jul 13-15 - Online: Lyman Alpha Emitters Workshop and Lager Meeting, Pasadena, California
Jul 13-15 - Virtual: 14th Scientific Meeting of the Spanish Astronomical Society
Jul 13-17 - Virtual Conference: Quantum Gravity 2020
Jul 13-17 - Workshop: Space Plasma Physics, Crete, Greece
Jul 13-17 - MOBSTER-1 Virtual Conference: Stellar Variability as a Probe of Magnetic Fields in Massive Stars
Jul 13-17 - Online: 41st Canadian Symposium on Remote Sensing, Yellowknife, Canada
Jul 14 - Mars Hope Mission (Al-Amal) H-2A Launch (United Arab Emirates)
Jul 14 - Anasis-II Falcon 9 Launch
Jul 14 - Jupiter At Opposition
Jul 14 - Apollo Asteroid 2020 MQ2 Near-Earth Flyby (0.044 AU)
Jul 14 - Webinar: Tracking Environmental Changes Due to COVID-19 Through Remote Sensing
Jul 14 - 5th Anniversary (2015), New Horizons, Pluto Flyby
Jul 14 - 55th Anniversary (1965), Mariner 4, Mars Flyby
Jul 14-15 - Virtual Mini conference: Compact Objects and Energetic Phenomena in the Multi-Messenger Era
Jul 14-15 - International Conference on Physics, Cosmology and Astrophysics (ICPCA), Tokyo, Japan
Source: JPL Space Calendar Return to Contents
12 of 15Food for Thought
Study: Dying Stars Breathe Life into Earth
NGC 7789, also known as Caroline's Rose, is an old open star cluster of the Milky Way, which lies about 8,000 light-years
away toward the constellation Cassiopeia. It hosts a few White Dwarfs of unusually high mass, analyzed in this study.
Credit: Guillaume Seigneuret and NASA
As dying stars take their final few breaths of life, they gently sprinkle their ashes into the cosmos through the
magnificent planetary nebulae. These ashes, spread via stellar winds, are enriched with many different
chemical elements, including carbon.
Findings from a study published today in Nature Astronomy show that the final breaths of these dying stars,
called white dwarfs, shed light on carbon's origin in the Milky Way.
"The findings pose new, stringent constraints on how and when carbon was produced by stars of our galaxy,
ending up within the raw material from which the Sun and its planetary system were formed 4.6 billion years
ago," says Jeffrey Cummings, an Associate Research Scientist in the Johns Hopkins University's Department of
Physics & Astronomy and an author on the paper.
The origin of carbon, an element essential to life on Earth, in the Milky Way galaxy is still debated among
astrophysicists: some are in favor of low-mass stars that blew off their carbon-rich envelopes by stellar winds
13 of 15became white dwarfs, and others place the major site of carbon's synthesis in the winds of massive stars that
eventually exploded as supernovae.
Using data from the Keck Observatory near the summit of Mauna Kea volcano in Hawaii collected between
August and September 2018, the researchers analyzed white dwarfs belonging to the Milky Way's open star
clusters. Open star clusters are groups of up to a few thousand stars held together by mutual gravitational
attraction.
From this analysis, the research team measured the white dwarfs' masses, and using the theory of stellar
evolution, also calculated their masses at birth.
The connection between the birth masses to the final white dwarf masses is called the initial-final mass
relation, a fundamental diagnostic in astrophysics that contains the entire life cycles of stars. Previous research
always found an increasing linear relationship: the more massive the star at birth, the more massive the white
dwarf left at its death.
But when Cummings and his colleagues calculated the initial-final mass relation, they were shocked to find
that the white dwarfs from this group of open clusters had larger masses than astrophysicists previously
believed. This discovery, they realized, broke the linear trend other studies always found. In other words, stars
born roughly 1 billion years ago in the Milky Way didn't produce white dwarfs of about 0.60-0.65 solar masses,
as it was commonly thought, but they died leaving behind more massive remnants of about 0.7 - 0.75 solar
masses.
The researchers say that this kink in the trend explains how carbon from low-mass stars made its way into the
Milky Way. In the last phases of their lives, stars twice as massive as the Milky Way's Sun produced new
carbon atoms in their hot interiors, transported them to the surface and finally spread them into the
surrounding interstellar environment through gentle stellar winds. The research team's stellar models indicate
that the stripping of the carbon-rich outer mantle occurred slowly enough to allow the central cores of these
stars, the future white dwarfs, to grow considerably in mass.
The team calculated that stars had to be at least 1.5 solar masses to spread its carbon-rich ashes upon death.
The findings, according to Paola Marigo, a Professor of Physics and Astronomy at the University of Padova and
the study's first author, helps scientists understand the properties of galaxies in the universe. By combining
the theories of cosmology and stellar evolution, the researchers expect that bright carbon-rich stars close to
their death, like the progenitors of the white dwarfs analyzed in this study, are presently contributing to the
light emitted by very distant galaxies. This light, which carries the signature of newly produced carbon, is
routinely collected by the large telescopes from space and Earth to probe the evolution of cosmic structures.
Therefore, this new understanding of how carbon is synthesized in stars also means having a more reliable
interpreter of the light from the far universe.
Source: EurekAlert/Johns Hopkins University Return to Contents
14 of 15Space Image of the Week
Other Worlds
Credit: Y. Beletsky (LCO)/ESO
Explanation One of the most exhilarating results in modern astronomy is the knowledge that the Universe is full of
worlds beyond our Solar System, known as exoplanets. Increasing evidence suggests that the majority of stars in
the Universe have planets whizzing around them; one such system can be seen in this majestic Picture of the
Week.
The antennas here are among the 66 that make up the Atacama Large Millimeter/submillimeter Array (ALMA),
located on the Chajnantor plateau in Chile. Two bright stars sit directly above the center antenna; the brightest of
these two stars is a triple star system known as Alpha Centauri. An exoplanet named Proxima b was recently
discovered orbiting within the habitable zone of one these three stars (Proxima Centauri) by ESO telescopes and
other facilities. As Alpha Centauri is the closest star system to Earth, Proxima b is the closest exoplanet to Earth
ever discovered.
Another world can be seen in this stunning sky — this time, one a little closer to home. At the top of the image, two
bright, reddish objects sit just outside the main river of the Milky Way. The one on the left is Antares — a red giant
star in Scorpius — and the one on the right is Saturn, the spectacular ringed gas giant planet.
Source: European Southern Observatory Return to Contents
15 of 15You can also read
