- Discovery of White Dwarf Pulsar Sheds Light on Star Evolution: In a groundbreaking discovery, scientists have identified a rare type of white dwarf star system, offering valuable insights into the process of stellar evolution. The findings contribute to our understanding of how stars transform over time.
- Exploring Planet Formation Timescales: New research by astronomers has revealed that the formation of planets can occur in remarkably shorter timescales, taking less than a million years. This discovery challenges previous assumptions about the length of time required for planetary formation.
- Virgin Galactic's First Successful Commercial Flight: Virgin Galactic has achieved a significant milestone by completing its inaugural commercial suborbital flight. The mission involved transporting a crew from the Italian Airforce and the National Research Council to the edge of space. This accomplishment marks a significant step forward in the realm of commercial space travel.
- July Skywatch Highlights: The month of July offers a host of celestial wonders for sky gazers. Notable highlights include the mesmerizing Southern Cross, the constellation Leo, and the awe-inspiring red supergiant star Antares. These celestial phenomena provide captivating sights for those observing the night skies in July.
#space #astronomy #science #news #podcast #spacetime
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00:00:00
Stuart Gary: This is space time series 26 episode 81 for
00:00:03
broadcast on the seventh of July 2023. Coming up on space time
00:00:09
discovery of a white dwarf pulsar shedding new light on
00:00:12
stellar revolution. A new study looking at how quickly planets
00:00:16
form and Virgin Galactic undertakes its first commercial
00:00:21
flight, all that and more coming up on space time.
00:00:26
Generic: Welcome to space time with Stuart Garry.
00:00:46
Stuart Gary: The discovery of a rare type of white dwarf star
00:00:49
system is providing a new understanding of stellar
00:00:52
evolution. White dwarfs are small dense stars, typically the
00:00:56
size of a planet they're formed when low mass stars like our sun
00:01:00
run out of nuclear fuel in their core. This causes the star's
00:01:05
outer envelope to expand and eventually puff off as a
00:01:08
planetary Nebula.
00:01:10
What's left behind is the exposed white hot stellar core?
00:01:14
A white dwarf which will then slowly cool over the eons. Now,
00:01:19
a rare type of white dwarf called the white dwarf pulsar
00:01:22
has been discovered for only the second time ever.
00:01:26
The first being A R Scorpio back in 2016 white dwarf pulsars
00:01:31
include a rapidly spinning white dwarf which is lashing its
00:01:35
neighbor a red dwarf star with powerful beams of electrical
00:01:38
particles and radiation causing the entire system to brighten
00:01:42
and fade dramatically over regular intervals just like the
00:01:45
beacon of a lighthouse.
00:01:47
Now, we know the pulsars caused by strong magnetic fields, but
00:01:50
scientists aren't sure what's causing those. One key theory to
00:01:54
explain the strong magnetic field is the dynamo model that
00:01:58
involves white dwarves having dynamos that is electric and
00:02:01
magnetic generators in their cause similar to that of the
00:02:04
Earth, but much more powerful.
00:02:06
But for this hypothesis to be tested, scientists needed to
00:02:09
search for other white dwarf pulsars to see if their
00:02:12
prediction held true. Now, a report in the Journal Nature
00:02:15
Astronomy describes a newly detected white dwarf pulsar
00:02:19
cataloged as J 1912, 13.72 minus 44 10, 45.1 located 773 light
00:02:28
years from Earth and spinning around 300 times faster than the
00:02:32
Earth does.
00:02:32
The white dwarf pulse is about the same size as the Earth, but
00:02:35
packing as much mass as the sun. Now, in simple terms, it means a
00:02:39
teaspoon of white dwarf material would weigh about 15 tons. White
00:02:44
dwarfs begin their lives at extremely hot temperatures but
00:02:47
gradually cooled down over billions of years.
00:02:50
And the low temperature of this particular white dwarf pulsar
00:02:53
points to an advanced age. One of the study's authors, Ingrid
00:02:56
Pela Suli from the University Of Warwick says the origins of
00:03:00
magnetic fields remains a big open question in many areas of
00:03:03
astronomy.
00:03:04
And this is particularly true for white dwarfs. See the
00:03:08
magnetic field of a white dwarf can be a million times stronger
00:03:11
than the magnetic field of the sun. And the dynamo model would
00:03:14
help to explain why you have to scan through stellar survey data
00:03:19
looking for star systems with similar characteristics to A R
00:03:22
scorpy.
00:03:23
And they then followed up any candidates with ultra cam, which
00:03:27
can detect the very fast light variations expected from a white
00:03:30
dwarf pulsar. After observing a couple of dozen candidates, they
00:03:34
finally found one that showed very similar light variations.
00:03:38
The follow up campaign using other telescopes revealed that
00:03:42
roughly every five minutes or so the system sent out a radio and
00:03:45
x-ray signal in our direction. It confirmed that there are more
00:03:50
white dwarf pulses out there. And there were other predictions
00:03:53
made by the dynamo model which were confirmed by this
00:03:56
discovery. See due to their old age white dwarfs in a pulsar
00:04:00
system should be cool.
00:04:01
Their companion should be close enough that the gravitational
00:04:04
pull of the white dwarf was in the past strong enough to
00:04:07
capture mass from the companion. And this causes them to be
00:04:10
spinning fast. And all of these predictions hold for the new
00:04:14
pulse are found. The white dwarf is cooler than 1300 Kelvin spins
00:04:19
on its axis every five minutes.
00:04:21
And the gravitational pull of the white dwarf has a strong
00:04:24
effect on the companion. This is space time still to come. A new
00:04:30
study looks at how quickly planets form and Virgin Galactic
00:04:33
undertakes its first commercial flight. All that are more still
00:04:37
to come on space time.
00:04:55
Astronomers have discovered that planets can take less than a
00:04:58
million years to form. The findings reported in the
00:05:01
astrophysical journal follow a major survey of proto planets
00:05:05
seen forming in the protoplanetary discs around
00:05:08
young stars.
00:05:10
These proto planets were already well underway in their formation
00:05:13
process. And the study's authors wanted to determine exactly how
00:05:17
early after a star is born. Do the first planets begin to form
00:05:21
within the system?
00:05:22
See these protoplanetary discs only last a few million years,
00:05:26
meaning that the forming planetary system really only has
00:05:29
this amount of time to finish its formation. However, it's
00:05:33
still not clear just how rapidly planet formation begins within
00:05:36
these discs.
00:05:37
Recent observations have revealed many protoplanetary
00:05:40
discs have structures inside them like apps and rings
00:05:44
indicating that planets already forming in these discs.
00:05:47
So if these protoplanetary discs already had planets forming in
00:05:51
them, the authors would need to look earlier in the proto
00:05:53
stellar disc from which the newborn star had just emerged
00:05:57
using alma, the Atacama large millimeter submillimeter array
00:06:01
radio Telescope in Chile.
00:06:03
The authors studied proto stars with a very high resolution in
00:06:07
order to search for the earliest signs of planetary formation,
00:06:11
they observed discs around 19 proto stars all located within
00:06:15
650 light years of the Earth.
00:06:17
Now, this in itself was the first systematic study to
00:06:21
investigate the detailed structure of discs around a
00:06:23
large sample of proto stars with high angular resolution.
00:06:27
The observations clearly showed that the protostar discs around
00:06:31
proto stars are different from the more evolved protoplanetary
00:06:35
discs among the 19 proto stars rings and gaps which are signs
00:06:40
of planetary formation were observed in only a few of the
00:06:43
discs and the ring structures and gaps were far less distinct
00:06:47
than those seen in protoplanetary discs.
00:06:50
The authors didn't expect to see such clear differences between
00:06:53
the discs around proto stars and more evolved discs.
00:06:57
The results suggest that the discs around proto stars simply
00:07:00
aren't fully ready yet for planetary formation and that
00:07:04
suggests that planetary formation in a planetary system
00:07:08
progresses rapidly in the 100 to a million years after
00:07:12
the star formation process begins, this is space time still
00:07:17
to come.
00:07:18
Virgin Galactic undertakes its first commercial flight and the
00:07:22
spectacular Southern Cross. The constellation Leo and the red
00:07:26
super giant Antares are among the many highlights of the July
00:07:31
night skies on sky watch.
00:07:49
Virgin Galactic has successfully undertaken its first commercial
00:07:52
suborbital flight carrying a crew from the Italian Air Force
00:07:56
and the nation's National Research Council to the very
00:07:58
edge of space.
00:08:00
The landmark event almost 20 years in the making marks the
00:08:03
start of the company's space tourism operations. The historic
00:08:07
flight aboard spaceship two VSS Unity lifted up from a
00:08:11
conventional runway at Spaceport America in New Mexico, attached
00:08:15
between the twin fuselages of the white knight.
00:08:18
Generic: Two mothership Eve pilots are ensuring the
00:08:20
spaceship is in the launch configuration after going
00:08:23
through the various L minus 10 checks confirming that all the
00:08:26
settings will go for launch.
00:08:27
This is also when spaceship Unity will isolate the air
00:08:31
supply from Eve and prime the rocket motor by opening the
00:08:34
backup oxidizer valve. Once these actions are complete, the
00:08:37
pilots will seek clearance from the MCC. That's shorthand for
00:08:41
the mission control center for release.
00:08:43
Stuart Gary: After climbing to an altitude of approximately
00:08:45
44 ft, that's roughly 15 m. Unity was released and
00:08:50
ignited its hybrid rocket engine to quickly accelerate vertically
00:08:54
through the sound barrier towards the blackness of space.
00:08:57
Generic: 321 release release, release ignition, good control
00:09:04
trimming that's turning, pulling the nose up after release, the
00:09:08
crew lights the rocket motor and Unity's trajectory to space
00:09:11
begins in that horizontal release position. Before turning
00:09:14
towards space a maneuver, we call the gamma turn.
00:09:17
The rest of the rocket motor burn will occur in the vertical
00:09:20
and everything after release through the completion of the
00:09:23
rocket motor burn is called boost. The trim is complete
00:09:26
immunity is in the vertical headed towards space and trim
00:09:30
has said we're now traveling at approximately mach 1.4. There's
00:09:34
max Q that's the maximum dynamic pressure on the vehicle those on
00:09:38
board are experiencing about three GS at the moment.
00:09:41
Stuart Gary: Mach two rocket motor cut off, main engine cut
00:09:44
off, ending the boost phase of the mission ended at mach 2.8
00:09:48
after boot is feather.
00:09:49
Generic: Now, sometimes when we say feather, we mean the tails
00:09:52
of the spaceship and sometimes we're referring to moving these
00:09:55
tails into what we call the feathered configuration. So due
00:09:59
to the law of conservation of momentum, feathering, the
00:10:02
vehicle that's rotating the tails to 60 degrees causes the
00:10:06
cabin of Unity to start a back flip maneuver as it approaches
00:10:10
our next phase.
00:10:12
APA And this backflip is a key part of the experience because
00:10:16
it maximizes the view of the Earth below. Our pilots use the
00:10:20
RCs. That's a reaction control system to hold the spaceship in
00:10:24
that attitude.
00:10:26
Stuart Gary: Sub or Apache was achieved just 58 minutes after
00:10:29
launch at an altitude of 85.1 kilometers, just 15 kilometers
00:10:34
short of a common line marking the official start of space.
00:10:38
Generic: Our mission specialists have been cleared to unstrap and
00:10:40
enjoy the zero G experience.
00:10:42
Colonel Villa going to the back to tend to the payloads that are
00:10:46
mounted on the rack. Le Dolfi and Leo starting their
00:10:50
experiments in their seat.
00:10:52
The feather is moving, starting that back flip maneuver. I spoke
00:10:55
of feathers is now fully.
00:10:56
Up and viva Italia, this is 100 years for the Italian Air Force.
00:11:01
So happy centennial to the Air Force. This is absolutely
00:11:05
incredible and welcome to space astronauts and Benito Neo ESPA,
00:11:11
congratulations to Walter Angelo and Leo on becoming astronauts.
00:11:15
Stuart Gary: Today, we have achieved a at 279 ft taking
00:11:21
a series of microgravity experiments and of course,
00:11:24
enjoying the spectacular views of the Earth beneath Unity began
00:11:28
its descent back to the surface.
00:11:30
Generic: Pilots are currently doing the completing the back
00:11:32
maneuver orienting the vehicle for re entry. You know, when we
00:11:37
talk about space travel, a lot of people know and they expect
00:11:40
the boost portion of flight to be loud and thrilling. And of
00:11:45
course it is. But what's interesting is that the re entry
00:11:47
is actually very similar.
00:11:49
So as supersonic air flowing over our vehicle in the
00:11:53
feathered configuration, shock waves form on top of the cabin
00:11:56
and those are audible to those inside. And then at the right
00:11:59
time, the pilots will again use the R CS to continue that back
00:12:03
flip all the way around. This prepares the vehicle for re
00:12:07
entry. In the feathered configuration.
00:12:09
The vehicle presents a large area of the wing to the
00:12:12
atmosphere, allowing our system to burn off energy while still
00:12:15
high in the thin atmosphere. And then after re entry, the feather
00:12:20
is once again lowered and locked, turning Unity into a
00:12:24
glider. It's in this configuration that the pilots
00:12:26
will fly back to Spaceport America in what we refer to as
00:12:30
the glide phase.
00:12:31
Stuart Gary: Gliding to a conventional runway landing on
00:12:34
the same tarmac had had taken off from 90 minutes earlier, the
00:12:37
Italian government had paid roughly $680 for each of the
00:12:41
passengers on the flight. British entrepreneur Richard
00:12:45
Branson founded Virgin Galactic back in 2004.
00:12:48
In the aftermath of the success of scaled composite spaceship
00:12:52
one wing space plane which had just won the X prize by becoming
00:12:56
the first privately built and operated spacecraft to reach
00:12:59
space twice within the space of two weeks. Thereby proving that
00:13:03
regular space travel is possible. Virgin Galactic's
00:13:07
fleet of suborbital rocket planes known as spaceship. Twos
00:13:10
are all based on the original spaceship. One design.
00:13:14
This is space time and time now to turn our eyes to the skies
00:13:34
and check out the celestial sphere for July on skywatch.
00:13:38
July is the seventh month of the year in both the Julian Angoor
00:13:42
calendars and he's named after the Roman Emperor Julius Caesar
00:13:46
who was born during the month before being called July. The
00:13:50
month was called Quintela, which is Latin for fifth. The addition
00:13:54
of the month January and February brought an end to that.
00:13:58
On average, July is the coldest month of the year in the
00:14:00
Southern hemisphere which is experiencing winter and also
00:14:04
marks the time when Earth is at aphelion, its furthest orbital
00:14:07
position from the sun. Of course, temperatures or more
00:14:11
accurately, seasons on Earth aren't dictated by the distance
00:14:14
from the sun.
00:14:15
But rather the length of the day and hence the amount of sunlight
00:14:19
a given part of the Earth receives, which is governed by
00:14:21
the tilt of Earth's axis. Consequently, that's why July is
00:14:25
on average, the warmest month in the northern hemisphere, which
00:14:28
is currently experiencing summer. During This Ayan Earth
00:14:31
will be 152 million, 93 kilometers from the sun.
00:14:37
That's about 5 million kilometers further away than
00:14:40
during Perra Hill and back on January the fifth when it was
00:14:43
147 million, 98 million kilometers away from the sun.
00:14:49
This year's affi occurred at 606 in the morning or Friday. July
00:14:53
the seventh Australian Eastern Standard time. That's 406 in the
00:14:57
afternoon of July the sixth us Eastern daylight time and 26 in
00:15:01
the evening. Greenwich mean time over cosmic time.
00:15:05
These dates change, that's due to variations in Earth's orbit
00:15:09
such as eccentricity as well as axial tilt and procession which
00:15:13
all follow regular cyclic patterns known as Malevich
00:15:17
cycles, eccentricity involves changes in how elliptical
00:15:21
Earth's orbit is around the sun. None of the planets actually
00:15:24
orbit the sun in perfect circles.
00:15:26
Although although Venus and Neptune are the closest,
00:15:29
instead, they all have elongated orbits which vary over time as
00:15:34
well as that Earth spins on an axis which is currently tilted
00:15:37
at 23.4 degrees compared to the ecliptic Earth's orbital plane
00:15:40
around the sun. But this angle of tilt also changes over time
00:15:45
influenced by among other things, the distribution of the
00:15:48
Earth's mass and just like a spinning top.
00:15:51
The rotational axis of the Earth also changes its orientation
00:15:55
through a process called procession, changing its
00:15:58
position in relation to fixed background stars over a 26
00:16:01
year cycle. Now, all these effects impact the amount of
00:16:05
solar radiation reaching the Earth and what time it reaches
00:16:08
the Earth and consequently the planet's seasonal and climatic
00:16:11
patterns.
00:16:14
Right now, the Southern Cross is at its highest point in the
00:16:17
Southern sky and is pointing directly towards the Southern
00:16:20
celestial pole. The Southern Cross falls within the
00:16:24
constellation Centaurus. The Centaur, the half human half
00:16:27
horse of Greek mythology and the creature is holding a bow loaded
00:16:32
with an arrow.
00:16:33
The Centaur's front legs are marked by the two pointer stars.
00:16:36
Alfre Beter Centaurus at 4.3 light years. Arter Centauri is
00:16:41
the second of the two pointer stars from the Southern Cross
00:16:44
and he is also the nearest star system to the sun.
00:16:47
The Centaur's back arches over the Southern Cross and just
00:16:51
above this is Omega Centauri, a spectacular globular cluster
00:16:56
visible with the unaided eye from dark locations. Globular
00:17:00
clusters are tightly packed spheres containing thousands to
00:17:03
millions of stars.
00:17:05
They're thought to have all originally been born at the same
00:17:08
time from the same molecular gas and dust cloud or they're the
00:17:11
cause of small Galaxies which have been consumed by bigger
00:17:14
Galaxies through galactic cannibalism. Omega Centauri is
00:17:18
about 16 light years away.
00:17:21
A light year is about 10 trillion kilometers. The
00:17:24
distance a photon can travel in a year at 300 kilometers per
00:17:28
second. The speed of light in a vacuum and the ultimate speed
00:17:31
limit of the universe.
00:17:33
Omega Centauri is one of the largest and brightest of the 150
00:17:38
or so globular clusters known to orbit around our Milky Way
00:17:41
galaxy Centaurus was one of the 48 constellations listed by the
00:17:46
second century astronomer Tome and it remains one of the 88
00:17:50
modern day constellations turning to the right or west and
00:17:55
you'll see the constellation Leo The Lion just above the western
00:17:58
horizon.
00:17:59
Its brightest star is Regulus or the little king located about 79
00:18:04
light years away. Regulus designated Alpha Leonis is
00:18:08
actually a five star system organized into two pairs.
00:18:12
Regulus A is a spectroscopic binary comprising a spectral
00:18:17
type B blue white main sequence star some four times the mass
00:18:21
and 288 times the luminosity of the sun and a faint companion
00:18:25
star thought to be a white dwarf.
00:18:27
The stellar corpse of a sun like star spectroscopic binaries are
00:18:32
stars that can be resolved by optical telescopes into two
00:18:35
separate objects and can only be separated by observing their
00:18:39
individual spectroscopic Doppler shifts as they orbit each other
00:18:42
astronomers describe stars in terms of spectral types, a
00:18:46
classification system based on temperature and characteristics.
00:18:50
The hottest most massive and most luminous stars inert a
00:18:53
spectral type of blue stars, they're followed by spectral
00:18:57
type b, blue white stars, then spectral type a white stars,
00:19:01
spectral type f whitish yellow stars, spectral type G yellow
00:19:06
stars.
00:19:06
That's where our sun fits in spectra type K orange stars and
00:19:10
the coolest and least massive known stars are spectral type M
00:19:14
red dwarf stars. Each spectral classification is also
00:19:18
subdivided using a numeric digit to represent temperature with
00:19:21
zero being the hottest and nine, the coolest and a Roman numeral
00:19:25
to represent luminosity. So put all that together and our sun is
00:19:30
a spectra type G two V or G 25 yellow dwarf star.
00:19:35
Also included in the stellar classification system are
00:19:38
spectra types LT and Y which were assigned to failed stars
00:19:42
known as brown dwarves, some of which were actually born as
00:19:45
spectra type M red dwarf stars but became brown dwarves after
00:19:49
losing some of their mass, brown dwarfs fit into a category
00:19:53
between the largest planets which can be about 13 times the
00:19:56
mass of Jupiter and the smallest spectral type M red dwarf stars
00:20:00
which can be 75 to 80 times the mass of Jupiter or 0.08 solar
00:20:05
masses located further away are Regulus BC and D which are dim
00:20:11
main sequence stars at the opposite end of the
00:20:14
constellation from Regulus is the star Bitter Leonis or
00:20:17
Denebola, the horse's tail.
00:20:20
It's also a luminous blue white star about half as bright as
00:20:23
Regulus. And the third brightest star in the constellation Leo
00:20:27
Beta Leonis has about 1.8 times the sun's mass and about 15
00:20:32
times the sun's luminosity.
00:20:34
It's suspected of being a dwarf se or delta Scotty type variable
00:20:38
star, meaning its luminosity varies slightly over a period of
00:20:41
several hours due to pulsations on its surface algebra or Gamma
00:20:46
Leonis is a binary system with a visible third component. The two
00:20:51
primary stars are located about 100 and 26 light years away and
00:20:55
can be resolved in small backyard telescopes.
00:20:58
Both are yellow giants orbiting each other every 600 Earth days.
00:21:03
The unrelated tertiary star named for Leonis is a yellow tin
00:21:07
star that can be seen through binoculars. The star's
00:21:10
traditional name algebra means forehead Del Leonis or Zosma is
00:21:14
a blue white star 58 light years from Earth epsilon.
00:21:18
The Otis is a yellow giant some 251 light years from Earth. And
00:21:22
Zeta Leonis is an optical triple star. The brightest component is
00:21:27
a white giant about 260 light years from Earth. While the
00:21:30
second brightest star 39 Leonis is widely spaced and located to
00:21:34
the south of the primary.
00:21:36
The third and faintest star in the system. 35 Leonis is to the
00:21:39
North Lou Leonis is a binary star system visible in medium
00:21:44
sized backyard telescopes located some 79 light years
00:21:49
away. Lou Leonis appears to be a yellow tin star with two
00:21:52
components orbiting each other every 183 Earth years.
00:21:56
Finally, in Leo, let's look at Taus visible as a double star
00:22:01
through binoculars. It's a yellow giant located some 621
00:22:05
light years from Earth and a binary secondary star 54 Leonis,
00:22:10
which is actually a pair of blue white stars, they're visible in
00:22:13
small telescopes and located some 289 light years away.
00:22:18
The constellation Leo also contains many Galaxies including
00:22:22
the spiral galaxy messier 66 as well as Messier 65 and GC 36 28
00:22:28
which are known as the Leo Triplet located some 37 million
00:22:33
light years away. The Leo Triplet is a somewhat distorted
00:22:36
shape due to gravitational interactions between Messer 66
00:22:40
and the other two Galaxies which are cannibalizing stars from
00:22:43
Messer 66.
00:22:45
Eventually, the outermost stars may well form a dwarf galaxy
00:22:48
orbiting M 66 Both M 65 and M 66 are visible in large binoculars
00:22:55
or small backyard telescopes, but their concentrated nuclei
00:22:58
and elongation are only visible in larger instruments.
00:23:02
Other bright well known deep sky Galaxies in Leo include Messier
00:23:06
95 Messier 96 and Messier 105. Messier 95 and Messier 96 are
00:23:14
both spiral Galaxies each about 20 million light years from
00:23:17
Earth, both look like fuzzy objects in small telescopes but
00:23:21
display their spectacular structures in larger
00:23:24
instruments. M 95 is a bar spiral.
00:23:28
Another Bard spiral NGC 2903 is thought to be similar in size
00:23:33
and structured to our own Milky Way galaxy. It was discovered by
00:23:37
William Herschel in 17 84. Close to the M 95 M 96 pair is the
00:23:43
elliptical galaxy M 105 which is also about 20 million light
00:23:47
years away.
00:23:49
The constellation also contains the Leo ring, a cloud of
00:23:52
hydrogen and helium gas orbiting two of the Galaxies in the
00:23:56
constellation, a gravitationally lensed object known as the
00:23:59
cosmic horseshoe is also found in Leo above Leo. You'll find
00:24:05
the constellation Virgo, the Greek and Roman goddess of wheat
00:24:09
and agriculture. Virgo's brightest star Spiker is visible
00:24:13
above the western horizon. It's located some 250 light years
00:24:18
away.
00:24:19
Spiker is Latin for ear of wheat which Virgo is holding in her
00:24:23
hand Spiker or alpha vi genus is the 16th brightest star in the
00:24:28
night sky and is both a spectroscopic binary and a
00:24:31
rotating eps solo variable a close binary system whose stars
00:24:36
are not eclipsing but cause apparent fluctuations in
00:24:39
brightness because of changes in the amount of light emitting
00:24:42
area visible to the observer Spiker.
00:24:45
Two main stars orbit each other once every four Earth days and
00:24:49
are so close their egg shape rather than spherical and can
00:24:52
only be separated by their spectra. The primary is the blue
00:24:56
giant variable beta seid star. It undergoes small, rapid
00:25:01
variations in brightness.
00:25:03
These are caused by pulsations of the star's surface thought to
00:25:06
be caused by the unusual properties of iron at
00:25:09
temperatures of 200 degrees in the stellar interior. It has
00:25:13
about 10 times the sun's mass and about seven times its
00:25:17
diameter.
00:25:18
The secondary star in Spiker is smaller than the primary, but
00:25:22
it's still some seven times more massive than the sun and has 3.6
00:25:26
times the sun's diameter turning to the north now and the
00:25:30
constellation Boies the herdsman or Plowman there, you'll see the
00:25:34
bright orange red star Atari or alpha boats just above the
00:25:38
northern horizon. It's a red giant located just 36 light
00:25:43
years away.
00:25:43
A bloated aging star, some 7.1 billion years old, nearing the
00:25:48
end of its life, although not much more massive than the sun.
00:25:52
It's now expanded out to some 25 times the sun's diameter and
00:25:56
will soon puff off its outer gasses envelope as a planetary
00:26:00
Nebula, revealing its white hot stellar core. A white dwarf
00:26:04
which will then slowly cool over the eons of time.
00:26:08
Another bright reddish looking star this time in the east is
00:26:11
the red super giant Antares, meaning the rival of Mars
00:26:16
because of its appearance and location in the sky, which
00:26:19
appears to be opposite of Mars in the sky. Antares is one of
00:26:23
the biggest known stars in the universe.
00:26:26
It's enormous 18 times the sun's mass, 10 times its
00:26:29
luminosity and 883 times the sun's radius, as we mentioned in
00:26:35
last month's skywatch, were it placed at the center of our
00:26:37
solar system? Its surface would extend out close to the orbit of
00:26:40
Jupiter despite being some 550 light years away.
00:26:45
Antares is still the 15th brightest star in the night sky.
00:26:49
Unlike the sun or Atari, the death of Antares will be far
00:26:53
more spectacular.
00:26:55
Antares is destined to explode as a core collapse or type two
00:26:58
supernova when it does so, sometime in the next few 100
00:27:03
years, it'll appear as bright in the Earth's sky as the full moon
00:27:07
and be quite visible even in daytime, Antares has a companion
00:27:11
star, Antares Bee, a specialty blue white main sequence star
00:27:15
more than seven times the sun's mass and five times its
00:27:18
diameter.
00:27:20
Antares is the heart of the Scorpion in the constellation
00:27:23
Scorpius. Below Scorpius is the constellation Sagittarius. The
00:27:27
Archer which points the way to the center of the Milky Way
00:27:30
galaxy Sagittarius is commonly represented as a wing Centaur
00:27:35
pulling back on a bow which is aimed at a tous the center of
00:27:39
the Milky Way galaxy and its supermassive black hole
00:27:42
Sagittarius.
00:27:43
A star lie at the westernmost part of Sagittarius, Sergio,
00:27:48
Teresa's star is about 27 light years away. And has some
00:27:52
4.3 million times the mass of our sun.
00:27:56
It was in July back in 2016, that the solar system's Barry
00:28:00
Center moved outside the sun where it will remain until 2027.
00:28:05
A Barry Center is the gravitational center of mass of
00:28:08
a celestial system. For example, in our Earth moon system, the
00:28:12
Earth and moon actually orbit each other around a common
00:28:14
center of gravity.
00:28:15
A Barry Center. And because the Earth is so much more massive
00:28:19
than the moon, the Barry Center is always inside the Earth's
00:28:22
radius. If it were outside the Earth's radius, the Earth and
00:28:26
moon would instead have been classified as a binary planetary
00:28:29
system like Pluto and Sharon.
00:28:32
The solar system's center of gravity or Barry Center is
00:28:35
usually located inside the sun's radius. After all, the sun
00:28:38
contains over 99 per cent of all the solar system's mass. But
00:28:43
actually the mass of the solar system is orbiting around the
00:28:46
solar system's Barry Center, which means the sun also has a
00:28:50
very slight spiraling 12 year orbit around the Barry Center.
00:28:54
And every now and then when the planet's orbital positions are
00:28:57
just right, especially when Jupiter and Saturn are nearest
00:29:00
to each other, their combined gravitational interactions move
00:29:04
the solar system's Barry Center ever so slightly outside the
00:29:07
sun's radius.
00:29:09
And because Jupiter and Saturn reach the salame every 11 years,
00:29:13
some scientists have speculated whether this could trigger the
00:29:16
sun's 11 year solar cycle. And before you ask the Barry Center
00:29:20
isn't named after some GNA Bay safari suit called Barry, but
00:29:24
rather, it's the ancient Greek word for heavy or center of
00:29:27
mass.
00:29:29
We also have two meteor showers, both of which peak in late July,
00:29:34
there's the Southern Delta Aris which are visible from mid July
00:29:38
to mid August each year with peak activity on July the 28th
00:29:41
and 29th, the shower originated either from the breakup of what
00:29:46
are now the Marsden and crack sun grazing comets or from the
00:29:49
parent comet P 96.
00:29:51
Maltz, the Delta Aris get their name because they're reading a
00:29:55
piece to lie in the constellation Aquarius. E one of
00:29:58
the constellation's brightest stars Delta Aquare. There are
00:30:02
two branches to the Delta Acrid meteor shower.
00:30:05
The Southern and northern, the Southern Delta Acrid are
00:30:08
considered a strong shower with an average of between 15 and 20
00:30:11
Meteors an hour between midnight and dawn. Listeners in the
00:30:15
Southern hemisphere usually get the better show because the
00:30:18
radiant is higher in the Southern sky since the radiant
00:30:21
is above the Southern horizon.
00:30:22
For northern hemisphere listeners, Meteors will be seen
00:30:25
to fan out in all directions east, north and west with few
00:30:28
Meteors heading southwards unless they're really short and
00:30:31
near the radiant. The Northern Delta Awards are the weakest
00:30:35
shower peaking later in mid August with an average peak rate
00:30:38
of about 10 Meteors per hour.
00:30:41
Meanwhile, the nearby slow and bright alpha cap record. Its
00:30:45
meteor shower will take place from as early as July the 15th
00:30:49
and continue until around August the 10th.
00:30:52
The meteor shower has infrequent but relatively bright Meteors
00:30:55
and even some fireballs it's generated as the Earth passes
00:30:59
through a debris trail left by the comet 1 69 P neat, which was
00:31:04
originally identified as the asteroid 2002 ex 12. However, it
00:31:09
was shown to be weakly active during perihelium and was then
00:31:12
reclassified as a comet. The meteor shower was created about
00:31:16
3500 to 5000 years ago.
00:31:19
When about half of the parent body disintegrated and fell into
00:31:22
dust, the cloud eventually evolved into Earth's orbit
00:31:26
causing a shower with peak rates of about five Meteors an hour
00:31:29
and some outbursts of bright flaring comets radiating out
00:31:33
from the constellation Capricorn towards the south.
00:31:36
The bulk of the comet's debris won't be on Earth's path until
00:31:39
the 24th century. By which time the alpha Capra corners are
00:31:42
expected to become a major annual meteor storm stronger
00:31:45
than any current annual shower.
00:31:48
Jonathan Nally, the editor of Australian Sky and Telescope
00:31:51
Magazine joins us now for the rest of our tour of the July
00:31:55
night skies.
00:31:56
Jonathan Nally: Good day Stewart. Yeah. Well, July night
00:31:58
sky. It's the middle of winter down here in the Southern
00:32:00
hemisphere, in the middle of summer for the fortunate people
00:32:03
up in the northern part of the planet where the temperatures
00:32:05
are very nice and it's bright and sunlight and everything. But
00:32:08
down here it's cold and a bit dark, but that's good, dark is
00:32:10
good for stargazing.
00:32:12
So if you go out in the evening, if you've never seen it, this is
00:32:14
a great time of the year actually to go out and spot the
00:32:16
Southern Cross because it's nice and high in the sky down due
00:32:20
south, just look straight down south and look up and you'll see
00:32:23
the Southern Cross there standing almost upright. Now,
00:32:26
the cross is like a kite shape. It's not like a cross like a
00:32:28
plus. It's a kite shape and it almost exactly upright.
00:32:33
Its correct name is Crooks. You could pronounce a crux. So like
00:32:38
a crucifix, that's that sort of shape. So if you have dark
00:32:40
enough skies, see if you can just see a large dark area next
00:32:46
to the Southern Cross. This is called the Coal sack Nebula. And
00:32:49
it's a giant cloud of dust and gas out there in space that's
00:32:52
blocking the light from the background star.
00:32:53
So it seems to be a hole in space, but you do need to be
00:32:56
under some pretty dark skies to see that and have your eyes well
00:32:59
dark adapted. So don't just go out after watching the telly and
00:33:02
expect to see it, give yourself 20 or 30 minutes for your eyes
00:33:05
to become adjusted to the darkness and you should be able
00:33:07
to see the coal.
00:33:08
It's really quite spectacular when you see it standing out
00:33:10
there in the middle of the Milky Way. Now, just off one corner of
00:33:13
the Southern Cross is a lovely little cluster of stars called
00:33:16
the jewel box. It gets its name from the range of colors of the
00:33:19
stars.
00:33:20
It contains to see it. You'll need at least a pair of
00:33:22
binoculars, but even a small pair of binoculars will show you
00:33:25
the jewel box and the Telescope will give you an even better
00:33:27
view. It's a really beautiful little cluster of stars to the
00:33:30
left of the Southern Cross.
00:33:31
There are two bright stars called the two pointers so
00:33:33
called because if you draw a line between them and extend it
00:33:36
further on points more or less to the Southern Cross. And we've
00:33:38
spoken about these many times on the program, the two pointers
00:33:41
are Alpha Sanaa and Beta Centauri. And we've often spoken
00:33:44
on the program about Alpha Centauri and how it's at least a
00:33:46
double star system and probably a triple star system.
00:33:49
If you include the tiny star Proxima Centauri, that's some
00:33:52
distance away and is in fact the nearest star to our solar
00:33:55
system. But Beta Centauri itself, the neighbor, it's a
00:33:58
triple star system too. It's got three stars that are pretty much
00:34:01
the same kind of star.
00:34:02
But to the naked eye, it just looks like one star, but it is
00:34:06
when you combine the light of the three of them. Yeah, it
00:34:08
looks like one star and it's the 11th brightest star the entire
00:34:11
night sky. We've got quite a few of the bright stars down in the
00:34:14
Southern part of the sky. We see that.
00:34:18
Stuart Gary: The Southern hemisphere skies have, most of
00:34:21
the bright stars in the sky are visible from here.
00:34:23
Jonathan Nally: It's got the majority of the really bright
00:34:25
ones. Yes. So we're very fortunate. I mean, you can see
00:34:27
many of those from the northern hemisphere as well, but of
00:34:29
course, they're easier to see down south here because they're
00:34:31
nice and high and speaking of high, high overhead, as seen
00:34:35
from Southern and mid latitude, this time of the year are some
00:34:38
fantastic constellations such as Scorpius and Sagittarius.
00:34:41
Now, Scorpius, the Scorpion is one of the few constellations
00:34:45
whose stars really do join up to accurately reflect its name. If
00:34:48
you do a join the dots affair with the stars, it really does
00:34:51
look like a Scorpion.
00:34:52
You see the pincers out the front and then the body and then
00:34:54
this big long curved tail with a Sting at the end of it, it's
00:34:58
really quite spectacular when you finally see it in the sky.
00:35:01
It's quite a large constellation. So you've got to
00:35:04
sort of stand back and take a big wide view and suddenly, oh,
00:35:06
there it is right there. Sagittarius, its next door
00:35:08
neighbor is named after the Archer, Sagittarius.
00:35:11
The Archer. It doesn't really look like someone holding a bow
00:35:13
and arrow and at least not to me, but it does have a better
00:35:16
claim to fame because when we look in the direction of
00:35:18
Sagittarius, we're looking into the heart of our Milky Way
00:35:21
galaxy about 26 light years away in the direction of the
00:35:25
western part of Sagittarius lies the core of our galaxy in the
00:35:29
Milky Way where a giant black hole lives.
00:35:31
So 26 light years, that's a good distance for a black hole
00:35:34
to be. You wouldn't want it very, very close. You can stay
00:35:38
where it is. Thank you very much. And it's gobbling up lots
00:35:40
of stuff all the time, four.
00:35:41
Stuart Gary: 0.3 million times the mass of our sun. And
00:35:43
luckily, it's quiet at the moment, although there are those
00:35:46
fermi bubbles to just give us a little bit of proof that it has
00:35:49
had a meal.
00:35:49
Jonathan Nally: Recently in the northern half of the sky seen
00:35:52
from Australia or New Zealand. You'll see a few bright stars.
00:35:55
There's one called Spiker, which is the brightest star in the
00:35:58
constellation of Virgo. And there's another one, a reddish
00:36:01
sort of colored one called arc Tous, which is the brightest
00:36:04
star in the constellation of boats. That's not a
00:36:06
constellation.
00:36:07
Most people are familiar with boats, it's spelled B double
00:36:10
otes and it means the herdsman or the Plowman arc tous. The
00:36:15
brightest star in boats is the fourth brightest star in the
00:36:18
night sky. And Spiker, the other one I mentioned in Virgo, it's
00:36:21
the 16th brightest star in the night sky. So there's quite a
00:36:24
few bright stars around at the moment.
00:36:26
Now, let's look at the planets for July. Mercury begins the
00:36:29
month out of view behind the sun, but give it a couple of
00:36:32
weeks and it will swing around in its orbit and then come up
00:36:36
above our western horizon after sunset in the second half of
00:36:40
July in the same area, you'll be able to see Venus and Mars.
00:36:44
In fact, for most of the month, these three planets will be
00:36:47
fairly close to each other in the post sunset, Western Sky,
00:36:51
Venus will be the big bright white one. Mars will be the
00:36:53
dimmer, reddish orange one and Mercury is a much smaller
00:36:57
intense white one. So that'd be pretty easy to spot because
00:37:00
they'll be all close together.
00:37:01
If you want to see Jupiter, you're going to have to stay up
00:37:03
well past midnight or get up early in the morning this month.
00:37:07
Because it's rising at about, I think about 2 a. m. at the start
00:37:10
of the month. You'll be able to spot it quite easily though
00:37:12
because it's a big bright light in the eastern sky. It looks
00:37:15
like a big bright star. So it's pretty easy to distinguish it
00:37:20
from everything else around it.
00:37:21
And finally, Saturn, Saturn is, are very easy to see in the
00:37:24
eastern sky at the moment after sunset because next month it's
00:37:28
going to reach a stage that astronomers call opposition.
00:37:32
This is when the sun and one of the outer planets like Jupiter
00:37:36
Saturn Uranus, that sort of thing, the sun and one of those
00:37:39
is are in opposite directions as seen from Earth.
00:37:43
So the sun is that way and the planet is 180 degrees that way.
00:37:46
And this is the best time for observation because it means
00:37:49
that when the sun is setting in the west, the planet is rising
00:37:52
in the east. And therefore, you've got all night through
00:37:54
till dawn to to get your Telescope out or your binoculars
00:37:58
or just the naked eye and have a good look at that planet, you
00:38:01
know, weather permitting.
00:38:02
So, and it's also around about the time when a planet, an outer
00:38:06
planet is that it's closest to the Earth too. So you get the
00:38:09
benefit of that as well. So next month, Saturn is going to be the
00:38:13
planet of the month and Matt Stewart is the night sky for
00:38:15
July.
00:38:16
Stuart Gary: That's Jonathan N, the editor of Australian Sky and
00:38:18
Telescope Magazine and this is space time and that's the show
00:38:39
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