Download First Light for May, 2001 - South Bay Astronomical Society

Journal of the South Bay Astronomical Society – April 2017
on line at http://sbastro.net/
On Facebook at facebook.com/SBAstroSociety
On Yahoo Groups at: https://groups.yahoo.com/neo/groups/SBASTRO/info
Monthly General Meeting: Friday May 5th 7:30 PM
Cassini at Mission End”
Matthew Ota, The Telescopes in Education Foundation
The April 4 Meeting
President Ken Rossi gaveled, or rather, dinged the meeting to a start at 7:35 PM. No visitors or newcomers were
present this evening. Ken highlighted a busy month of star parties of which only one got rained out. Successful star
parties were held at Smith Elementary, La Bellona Elementary, Wood Elementary, and El Segundo. Due to a
scheduling error, the ‘Victor Elementary star party was not very well attended.
Ken Munson related a recent solo outreach event where he took his telescopes, Nexstar 11 and Personal Solar
Telescope, to Peck Park in Rancho Palos Verdes and gave lots of people a tour of the daytime sky. Objects seen
included the Sun, Moon, Mercury, Venus, Mars and a few bright stars.
After a brief social break, the meeting resumed with a showing of the El Segundo TV report of the El Segundo Star
Party. Afterwards, President Rossi presented the evening’s speaker, Christopher Spalding. Christopher is a
graduate student at Cal Tech, studying under Konstantin Batygin. His presentation was titled “Upside-Down Stars,
Inside-Out Orbits”. Growing up in Northern Ireland, he had an excellent view of the nighttime sky and it inspired him
to become an astrophysicist.
He began his talk with a brief review of our understanding of our own solar system. For over a thousand years, the
Aristotelian view dominated the concept of our solar system. His theory placed the earth at the center of the
universe. A contrary view put forth by Aristarchus of Samos placed the sun at the center but it didn’t gain wide
acceptance.
Only with the invention of the telescope did our knowledge of the solar system became more in line with reality.
Galileo’s discovery of Jupiter’s moons showed a solar system in miniature that provided a model of the whole solar
system. It was soon realized that the stars were much more distant. So, then the question became could there be
planets around other stars? As early as 1584, Giordano Bruno posited the idea of other planets and even life. For
which he was promptly burned at the stake.
Our solar system has 8 major planets, all in a nice flat plane. In fact, the planets only vary from each other by about
2o. Immanuel Kant proposed the idea that solar systems are formed out of nebular clouds which collapse into stars
and planets, the angular momentum of the cloud serving to flatten the orbital plane.
Exo-planets are found by two primary methods: 1) the Transit technique which has found thousands of planets, and
2) the Stellar Wobble method which measures the changes in a star’s relative motion by monitoring the spectrum.
1
The transit method can only find systems that are aligned with our line of sight. The Stellar Wobble Method can find
planetary systems that are not fully aligned with our line of sight but still have a component that provides a relative
motion towards or away from Earth. Thus, the Wobble method provides for a wider range of planetary systems. If
both methods can be used on a exo-system, the size and mass of the planets can be determined.
Given these two methods, it’s not entirely surprising that many of the earliest exo-planets discovered were all “Hot
Jupiters”, large massive planets in very close orbits around their stars. 51 Pegasi has a large planet orbiting 1/20 of
the Earth-Sun distance. For 10 years, hot Jupiters dominated the list of exo-planets. Then came the Kepler
telescope which stared at one patch of sky for a long time. The data continues to be mined but the results so far are
amazing. Mr Spalding presented an interesting chart that showed the Kepler candidates. The vast majority of exoplanets seen by Kepler range between Earth and Neptune in size. Most of them are also in tight orbits. Kepler-11
has 6 planets in orbits that would all fit within the orbit of Venus.
The Trappist-1 system which has recently gain wide press coverage has a star that is 1/20 the size of the Sun and
has 7 planets in orbits that would fit inside Mercury’s orbit. Yet at least 2 or 3 are in the “Goldilocks Zone”.
Another interesting chart presented the ranges of exo-planet sizes. Curiously, there are two peaks in exo-planet
sizes. One peak occurs at about 1.3 times the size of Earth. A second peak occurs at about 2.4 times the size of
Earth. Most planets seem to lie in the “Super Earth” size around the 2.4x Earth size.
It is thought that these two peaks result from the differing way in planets form. One way a planet can before is that it
manages to retain the hydrogen atmosphere that it formed with. These planets may be big in size but lower in
density due to the thick atmospheres. Planets at the lower peak are thought to have lost most of their hydrogen
atmosphere. They may have retained other atmospheric gases which could be amenable to life. A colleague of Mr.
Spalding, Erik Petigura, theorizes that up to 20% of sun-like stars may possess habitable planets.
Some exo-planet systems appear to have some serious spin-orbit misalignment. The misalignment of the planetary
orbits to the spin axis of the Sun is only about 6 o. Many systems have been found that appear to have orbits that
look more like a model of an atom. Some systems even have planets that revolve around their stars in the opposite
direction to their star’s spin. Surprisingly, the smaller stars tend to have aligned planetary systems while big stars
are misaligned. So far, only about 50% of exo-planet systems are aligned with their star’s spin axis.
How is it possible to have such misalignment? The prevailing theory is that these systems formed out of a giant
molecular cloud. As the cloud collapsed into the different stars that could make up a loose open cluster, nearby
companion stars pulled on each other. The constant gravitational tugs on the forming planetary disks gradually tilted
the plane of the exo-planets away from the spin axis of the star.
In the case of small stars, the intense magnetic field may have held the protoplanetary disk together in the region
closest to the star, thus preventing the misalignments of the orbital plane.
In conclusion, he summarized his talk with 3 points:
1) Star-Planet Orbit Misalignment – Upside Down Systems.
2) Star-Planet Distance – Inside-out Systems.
3) Planetary size – Our system is unusual compared to most exo-planets found to date.
After a round of excellent questions by the audience, President Rossi brought the meeting to a close at 9:20 PM.
-
2
Ken Munson
This article is provided by NASA Space Place.
With articles, activities, crafts, games, and lesson plans, NASA Space Place
encourages everyone to get excited about science and technology.
Visit spaceplace.nasa.gov to explore space and Earth science!
NOAA's Joint Polar Satellite System (JPSS) to monitor
Earth as never before
By Ethan Siegel
Later this year, an ambitious new Earth-monitoring satellite will launch into a polar orbit around our planet. The new
satellite—called JPSS-1—is a collaboration between NASA and NOAA. It is part of a mission called the Joint Polar
Satellite System, or JPSS.
At a destination altitude of only 824 km, it will complete an orbit around Earth in just 101 minutes, collecting
extraordinarily high-resolution imagery of our surface, oceans and atmosphere. It will obtain full-planet coverage
every 12 hours using five separate, independent instruments. This approach enables near-continuous monitoring of
a huge variety of weather and
climate phenomena.
JPSS-1 will improve the
prediction of severe weather
events and will help advance
early warning systems. It will
also be indispensable for
long-term climate monitoring,
as it will track global rainfall,
drought conditions and ocean
properties.
The
five
independent
instruments on board are the
main assets of this mission:
 The
Cross-track
Infrared
Sounder
(CrIS) will detail the
atmosphere’s
3D
structure, measuring
water
vapor
and
temperature in over Ball and Raytheon technicians integrate the VIIRS Optical and Electrical Modules onto the
1,000
infrared JPSS-1 spacecraft in 2015. The spacecraft will be ready for launch later this year. Image
spectral channels. It Credit: Ball Aerospace & Technologies Corp.
will enable accurate
weather forecasting up to seven days in advance of any major weather events.
 The Advanced Technology Microwave Sounder (ATMS) adds 22 microwave channels to CrIS’s
measurements, improving temperature and moisture readings.
 Taking visible and infrared images of Earth’s surface at 750 meter resolution, the Visible Infrared Imaging
Radiometer Suite (VIIRS) instrument will enable monitoring of weather patterns, fires, sea temperatures,
light pollution, and ocean color observations at unprecedented resolutions.
 The Ozone Mapping and Profiler Suite (OMPS) will measure how ozone concentration varies with altitude
and in time over every location on Earth's surface. This can help us understand how UV light penetrates the
various layers of Earth’s atmosphere.
3

The Clouds and the Earth’s Radiant System (CERES) instrument will quantify the effect of clouds on Earth’s
energy balance, measuring solar reflectance and Earth’s radiance. It will greatly reduce one of the largest
sources of uncertainty in climate modeling.
The information from this satellite will be important for emergency responders, airline pilots, cargo ships, farmers
and coastal residents, and many others. Long and short term weather monitoring will be greatly enhanced by JPSS1 and the rest of the upcoming satellites in the JPSS system.
Want to teach kids about polar and geostationary orbits? Go to the NASA Space Place:
https://spaceplace.nasa.gov/geo-orbits/
SBAS Executive Board
President
Vice-President
Greg Benecke
Ryan Parker
310-217-1512
213-454-1766
[email protected]
[email protected]
Secretary
Steve Pedersen
310-378-6479
[email protected]
Treasurer & Astronomical
League Rep.
Cynthia Jackson
310-613-0647
[email protected]
SBAS Committees
Program Chairman
Astronomical League
Liaison
Outreach Committee
Newsletter Reproduction
Publications Committee:
SBAS Website
Webmaster
First Light Editor
Observing Committee
Membership Committee
Cathy Brassell
[email protected]
Ken Rossi
310-515-1586
[email protected]
Ken Munson
Greg Benecke
Craig Gates
Ray Grace
310-257-1971
310-217-1512
310-376-6387
310-370-1913
[email protected]
[email protected]
[email protected]
[email protected]
Publicity Committee
Property Committee
Manhattan Bch
Blvd
San Diego
Fwy (405)
Harbor Fwy
(110)
Monthly General
Meetings
We normally meet on the first Friday of each month
at 7:30 p.m. in the Planetarium at El Camino College
(16007 Crenshaw Bl. In Torrance). If the first Friday
is on or close to a holiday, we usually defer the
meeting until the second Friday of the month. The
Planetarium is on the south side of Manhattan
Beach Blvd., one block west of Crenshaw Blvd.
(near the center of the map at left).
Crenshaw
Blvd
The planetarium is the only round, domed building
on campus. There is on-street parking, and we can
often use campus parking: check inside to see if you
4
need a FREE parking permit for your car.
We enjoy the planetarium facilities through the courtesy of the El Camino College Administration, and have several
faculty members of the Astronomy Department as members of our Club. Our meetings always include an informal
opening, when new attendees are invited to introduce themselves and let us know about their interests in
astronomy. Members share their latest news and observations at this time. The rest of the evening is devoted to
guest speakers, who range from amateur astronomers to professional astronomers to representatives from local
aerospace companies to college professors. We are fortunate to have all these talented people in our area, willing to
come and talk to us.
Monthly Planning Meeting
Committee members (and anyone else with an interest in Society activities) meet each month, usually on the
Monday following the general meeting. Meetings are sometimes rescheduled due to travel and other circumstances.
Exact date and time of each month’s meeting will be announced in the monthly meeting. The March planning
meeting will be held at the home of TBD.
.
SBAS Dues
Month Join/Due
Member (Family)
Student Expires
Email Only
January
_$40.00
$25.00
Dec
February
_$36.67
$22.92
Dec
March
_$33.33
$18.75
Dec
April
_$30.00
$20.83
Dec
May
$26.67
$18.75
Dec
June
_$23.33
$16.67
Dec
July
_$20.00
$14.58
Dec
August
_$16.67
$12.50
Dec
September
_$13.33
$10.42
Dec
October
_$10.00
$8.33
Dec
November
_$6.67
$6.25
Dec
December
_$3.33
$4.17
Dec
Note to Current U.S. Mail Members: The SBAS Board has decided that it is no longer cost effective to publish and
mail out hard copies of the FirstLight. Since this decision was made after some 2016 renewals for U.S. Mail
memberships were received, we will either refund the difference or extend your full 2015 membership though March
of 2016.
To simplify the dues, we suggest that all membership expire in December. Dues are $40.00/year ($25.00/year for
students) and expire on December 31, of the current year. The FirstLight is now only available via Email notification
and on our web site. New members use Month Join, and current members select your expiring Month to calculate
the amount. Members that expire in October or November may wish to write one check and include next year’s
membership. Make checks payable to the South Bay Astronomical Society. Dues may be paid at the general
meeting or mailed to:
5
South Bay Astronomical Society
Attn: Greg Benecke
P.O. Box 1937
Redondo Beach, CA 90278
SBAS Membership Benefits
Contact Greg Benecke for magazine subscriptions at club rates: “Sky & Telescope” $32.95 and “Astronomy”
$34.00/1 year or $60.00/2 years!
Note: S&T subscribers at the club rate renew their subscriptions by mailing their renewal notice and check or calling
the 800# on the renewal notice.
Only new subscribers or subscribers converting their subscription to the club rate need to contact Arnie or send a
check to the PO Box. Astronomy subscriptions and renewals still go through Arnie or via the PO Box.
Astronomy Technology Today has become a digital only magazine. They have stated that current print subscribers
will continue to be able to access digital issues without any cost. New subscribers should check their website for
ordering details and subscription costs (www.astronomytechnologytoday.com).
Online Subscribe/Renew Instructions Astronomy Magazine
US Subscription Rate:
1 year/12 Issues…..$34.00
2 years/24 issues….$60.00
3 years/36 Issues….$85.95
This year, there is an additional option for club member to order or renew. If you prefer, you can complete your
individual transaction online with a credit card. Please follow the instructions below:
1) Go to www.astronomy.com/promo
2) When prompted for the promotion code, type in your club’s unique offer code “RCLUB165” and click the
“Get Offer” button.
3) Select the order term (1 year, 2 years, or 3 years).
4) Enter your name, address and credit card information. Please note: you do not need to enter the promotion
code a second time on this order page. That entry field can be disregarded.
5) Click on the “Submit” button. You will receive a confirmation page immediately. Please print this page for
your records.
If you have any questions, call one of our Customer Service Representatives at 1-800-533-6644, Monday – Friday
8:30 AM – 4:30 PM CT. Outside the US and Canada, please call 262-796-8776.
Astronomical League Observing Clubs
All SBAS members in good standing are also members of the Astronomical League and are eligible to participate in
the League’s Observing Clubs. The Astronomical League provides many different observing programs (clubs).
These programs are designed to provide a direction for your observations and to provide a goal. The programs have
certificates and pins to recognize the observers’ accomplishments and for demonstrating their observing skills with a
variety of instruments and objects. For more information, go to:
http://www.astroleague.org/observing.html.
6
New Free Astronomy Technology Today Subscription Offer
Astronomy Technology Today offers a free 12-month online subscription for members. Go to the following URL for
instructions on how to subscribe: http://www.cnyo.org/2016/02/01/12-free-months-of-astronomy-technology-todaytellem-cnyo-or-your-own-club-sent-you/
Useful and Interesting Astronomy Websites
Website
http://www.calsky.com/
https://www.aavso.org/
http://www.cleardarksky.com/csk/prov/California_clocks.html
http://ssd.jpl.nasa.gov/horizons.cgi
http://heavens-above.com
http://www.lunar-occultations.com/iota/iotandx.htm
http://pictures.ed-morana.com/ISSTransits/predictions/
http://www.aerith.net/comet/weekly/current.html
http://sohowww.nascom.nasa.gov/
7
Description
A useful site for planning an evening's star
gazing if you don't have your own
planetarium software.
Information for observers with an interest
in tracking variable stars.
Good site to check to know what the
weather will be like where you might be
planning on going.
Great site to use when you want to find a
new comet or asteroid that isn't already in
your planetarium software's list. See the
Ephemeris Generator file on the SBAS
Yahoo group site for instructions.
Check this site to find out what satellites
may be visible in your sky.
Website for the International Occultation
Timing Association. Good place to find
information on asteroid occultations of
background stars.
Find out when the ISS will transit in front
of the Sun or Moon as seen from your
location.
Weekly information on bright comets.
Good place to learn where there are bright
comets to be seen. Refer to the Horizons
website above to generate ephemerides.
See the sun in ways you might never have
imagined! You can even create your own
movies of the sun in different the different
frequencies imaged by the SOHO
spacecraft.
Outreach Events
Wood Elementary – On Thursday, March 23, club members, Ken Rossi, Jill Nakano, Tina Musto, Gerry Stowe,
Larry Kinney, Steve Pedersen and Ken Munson brought their telescopes to Wood Elementary school in Torrance.
It’s a school we’ve been to several times before and it has a very convenient area for setting up. The school always
gives us great support. The crowd this year wasn’t as big as in previous years, apparently due to a shortage of
science projects this time around. Still, the smaller crowd allowed us to give those attending a greater variety of
objects to see. This included double stars (145 Canis Major, Castor, Beta Monoceros), Nebulas (M42, NGC 3242
“The Ghost of Jupiter), star clusters (M41, M36, M38) and a very nice carbon star, R Leporis. A very nice night with
nicely clear skies even though the seeing wasn’t spectacular.
El Segundo Star Party – The annual El Segundo Star Party was held again at the top of the parking structure at
Hilltop Park on Friday March 24th. Members Ken Rossi, Larry Kinney, Jill Nakano, Steve Pedersen, and Ken
Munson set up their scopes. Gerry Stowe had planned on attending but got sick. Luckily some friends, Adam and
Miriam Litman, were able to come in his place. Once again, great support from the city parks department for turning
out all the nearby lights and providing a video show for the crowd. High thin clouds moved in and threatened to spoil
the night. Fortunately, they stayed thin and even had large open areas of sky in between so it wasn’t as bad as it
might have looked. The wind was whipping along pretty good and it was very cold in the parking lot. Still, it didn’t
keep the crowds away. A large crowd rapidly grew as the sun set and we were busy all evening until the crowd
finally thinned out around 10 PM. Amazingly, Jupiter was well up in the sky by then and those who stayed were
treated to some really amazing views of the giant planet as the seeing had improved remarkably. One interesting
change to the event this year was a news crew from the local cable channel. Reporter Amy Lieu and her camera
man stayed through the cold night to interview club members who brought their scopes as well as crowd members
who brought their families. The video can be viewed at: https://www.youtube.com/watch?v=o06XX8pnmZ8
Peck Park – Since I still had all my equipment in my car from the oddly abortive Victor Elementary star party, I
decided to do a little daytime outreach at a public park. This time I chose Peck Park at Western and Crestwood in
RPV. The sky was beautifully clear, the weather comfortably cool with just a light breeze. I was able to get a good
open spot off the main field area near the basketball court. Luckily, I never had any problem with errant basketballs!
I brought my Coronado Personal Solar Telescope and set it up on top of my Nexstar. Things really worked well and
I was able to align on the Sun, then found Venus, Mercury and Mars. Using the planets as alignment points was
better as it improved the accuracy of subsequent go-tos. That helped as I was able to find several bright stars
throughout the day. Aldebaran, Betelgeuse, Deneb and Castor were good daytime targets. The moon was
especially thrilling to people as it was in first quarter. As it rose higher in the midday, viewers were able to see more
and more craters as the contrast improved. Even so, people kept coming back to see the stars. They were so
amazed that I could find stars in the bright midday Sun.
The sun was really spectacular with two huge sunspot groups visible in white light and also in the PST. A dark
filament stretched across the eastern half of the sun. Huge prominences arced up over the eastern limb. One was
very clearly a loop prominence. Viewers were thrilled to be able to see such things. Curiously, the sunspot near the
western limb grew brighter and brighter throughout the day until by 4 PM it was glowing like a white-hot iron and was
almost painful to look at in the PST. I wondered if it meant anything. When I checked a space weather site on the
next day, I found that sunspot group had erupted with 4 large M-Class flares!
As luck would have it, I happened to be near a group of picnic tables where a large extended family and their friends
were celebrating a 5-year-old’s birthday. They had a reptile show (another outreach event!) which was fun to see
even though a really big snake kind of got away and slithered up a tree. A couple of guys had to climb up after it
and peel it off the branches. Luckily, not a venomous snake! I had quite a few of the family members come over to
take a look as well as other park visitors. The family invited me to join them for their party since I’d provided them
some amazing entertainment. That was really nice! It was an all-around really great day!
8
Milky Way: Hydrogen halo lifts the veil of our galactic home
Astronomers find missing mass in the hydrogen halo that surrounds our home galaxy
Science Daily 18 April 2017 - Sometimes it takes a lot of trees to see the forest. In the case of the latest discovery
made by astronomers at the University of Arizona, exactly 732,225. Except that in this case, the "forest" is a veil of
diffuse hydrogen gas enshrouding the Milky Way, and each "tree" is another galaxy observed with the 2.5-meter
telescope of the Sloan Digital Sky Survey
After combining this staggering number of spectra -- recorded patterns of wavelengths revealing clues about the
nature of a cosmic target -- UA astronomers Huanian Zhang and Dennis Zaritsky report the first detections of diffuse
hydrogen wafting about in a vast halo surrounding the Milky Way. Such a halo had been postulated based on what
astronomers knew about other galaxies,
but never directly observed.
What our Milky Way might look like to alien astronomers: This
image of NGC 2683, a spiral galaxy also known as the "UFO
Galaxy" due to its shape, was taken by the Hubble Space
Telescope. Since trying to find out what the Milky Way looks like is
a bit like trying to picture an unfamiliar house while being confined
to a room inside, studies like this one help us gain a better idea of
our cosmic home.
Credit: ESA/Hubble & NASA
deputy director of the UA's Steward Observatory.
Astronomers have long known that the
most prominent features of a typical spiral
galaxy such as our Milky Way -- a central
bulge surrounded by a disk and spiral
arms -- account only for the lesser part of
its mass. The bulk of the missing mass is
suspected to lie in so-called dark matter, a
postulated but not yet directly observed
form of matter believed to account for the
majority of matter in the universe. Dark
matter emits no electromagnetic radiation
of any kind, nor does it interact with
"normal" matter (which astronomers call
baryonic matter), and is therefore invisible
and undetectable through direct imaging.
The dark matter of a typical galaxy is
thought to reside in a more or less
spherical halo that extends 10 to 30 times
farther out than the distance between the
center of our galaxy and the sun,
according to Zaritsky, a professor in the
UA's Department of Astronomy and
"We infer its existence through dynamical simulations of galaxies," Zaritsky explains. "And because the ratio of
normal matter to dark matter is now very well known, for example from measuring the cosmic microwave
background, we have a pretty good idea of how much baryonic matter should be in the halo. But when we add all
the things we can see with our instruments, we get only about half of what we expect, so there has to be a lot of
baryonic matter waiting to be detected."
By combining such a large number of spectra, Zaritsky and Zhang, a postdoctoral fellow in the Department of
Astronomy/Steward Observatory, covered a large portion of space surrounding the Milky Way and found that diffuse
hydrogen gas engulfs the entire galaxy, which would account for a large part of the galaxy's baryonic mass.
"It's like peering through a veil," Zaritsky said. "We see diffuse hydrogen in every direction we look."
He pointed out that this is not the first time gas has been detected in halos around galaxies, but in those instances,
the hydrogen is in a different physical state.
"There are cloudlets of hydrogen in the galaxy halo, which we have known about for a long time, called high-velocity
clouds," Zaritsky said. "Those have been detected through radio observations, and they're really clouds -- you see
an edge, and they're moving. But the total mass of those is small, so they couldn't be the dominant form of hydrogen
in the halo."
9
Since observing our own galaxy is a bit like trying to see what an unfamiliar house looks like while being confined to
a room inside, astronomers rely on computer simulations and observations of other galaxies to get an idea of what
the Milky Way might look like to an alien observer millions of light-years away.
For their study, scheduled for advance online publication on Nature Astronomy's website on Apr. 18, the researchers
sifted through the public databases of the Sloan Digital Sky Survey and looked for spectra taken by other scientists
of galaxies outside our Milky Way in a narrow spectral line called hydrogen alpha. Seeing this line in a spectrum tells
of the presence of a particular state of hydrogen that is different from the vast majority of hydrogen found in the
universe.
Unlike on Earth, where hydrogen occurs as a gas consisting of molecules of two hydrogen atoms bound together,
hydrogen exists as single atoms in outer space, and those can be positively or negatively charged, or neutral.
Neutral hydrogen constitutes a small minority compared to its ionized (positive) form, which constitutes more than
99.99 percent of the gas spanning the intergalactic gulfs of the universe.
Unless neutral hydrogen atoms are being energized by something, they are extremely difficult to detect and
therefore remain invisible to most observational approaches, which is why their presence in the Milky Way's halo
had eluded astronomers until now. Even in other galaxies, halos are difficult to pin down.
"You don't just see a pretty picture of a halo around a galaxy," Zaritsky said. "We infer the presence of galactic halos
from numerical simulations of galaxies and from what we know about how they form and interact."
Zaritsky explained that based on those simulations, scientists would have predicted the presence of large amounts
of hydrogen gas stretching far out from the center of the Milky Way, but remaining associated with the galaxy, and
the data collected in this study confirm the presence of just that.
"The gas we detected is not doing anything very noticeable," he said. "It is not spinning so rapidly as to indicate that
it's in the process of being flung out of the galaxy, and it does not appear to be falling inwards toward the galactic
center, either."
One of the challenges in this study was to know whether the observed hydrogen was indeed in a halo outside the
Milky Way, and not just part of the galactic disk itself, Zaritsky said.
"When you see things everywhere, they could be very close to us, or they could be very far away," he said. "You
don't know."
The answer to this question, too, was in the "trees," the more than 700,000 spectral analyses scattered across the
galaxy. If the hydrogen gas were confined to the disk of the galaxy, our solar system would be expected to "float"
inside of it like a ship in a slowly churning maelstrom, orbiting the galactic center. And just like the ship drifting with
the current, very little relative movement would be expected between our solar system and the ocean of hydrogen.
If, on the other hand, it surrounded the spinning galaxy in a more or less stationary halo, the researchers expected
that wherever they looked, they should find a predictable pattern of relative motion with respect to our solar system.
"Indeed, in one direction, we see the gas coming toward us, and the opposite direction, we see it moving away from
us," Zaritsky said. "This tells us that the gas is not in the disk of our galaxy, but has to be out in the halo."
Next, the researchers want to look at even more spectra to better constrain the distribution around the sky and the
motions of the gas in the halo. They also plan to search for other spectral lines, which may help better understand
the physical state such as temperature and density of the gas.
10
Hubble sees starbursts in Virgo
Although galaxy formation and evolution are still far from being fully
understood, the conditions we see within certain galaxies -- such as
so-called starburst galaxies -- can tell us a lot about how they have
evolved over time. Starburst galaxies contain a region (or many
regions) where stars are forming at such a breakneck rate that the
galaxy is eating up its gas supply faster than it can be replenished!
NGC 4536 is such a galaxy, captured here in beautiful detail by the
Hubble's Wide Field Camera 3 (WFC3). Located roughly 50 million
light-years away in the constellation of Virgo (The Virgin), it is a hub
of extreme star formation. There are several different factors that can
lead to such an ideal environment in which stars can form at such a
rapid rate. Crucially, there has to be a sufficiently massive supply of
gas. This might be acquired in a number of ways -- for example by
passing very close to another galaxy, in a full-blown galactic collision,
or as a result of some event that forces lots of gas into a relatively
small space.
Star formation leaves a few tell-tale fingerprints, so astronomers can
tell where stars have been born. We know that starburst regions are
rich in gas. Young stars in these extreme environments often live fast
and die young, burning extremely hot and exhausting their gas
supplies fairly quickly. These stars also emit huge amounts of intense
ultraviolet light, which blasts the electrons off any atoms of hydrogen
lurking nearby (a process called ionization), leaving behind often
colorful clouds of ionized hydrogen (known in astronomer-speak as
HII regions).
Although galaxy formation and evolution
are still far from being fully understood,
the conditions we see within certain
galaxies -- such as so-called starburst
galaxies -- can tell us a lot about how they
have evolved over time. Starburst
galaxies contain a region (or many
regions) where stars are forming at such a
breakneck rate that the galaxy is eating
up its gas supply faster than it can be
replenished!
Credit: ESA/Hubble & NASA
Supermassive black holes found in two tiny galaxies
Black holes may lurk in most ultra-compact dwarf remnants of shredded
galaxies
Three years ago, a University of Utah-led team discovered that an ultra-compact dwarf galaxy contained a
supermassive black hole, then the smallest known galaxy to harbor such a giant black hole. The findings suggested
that the dwarfs were likely tiny leftovers of larger galaxies that were stripped of their outer layers after colliding into
other, larger galaxies.
Now, the same group of U astronomers and colleagues have found two more ultra-compact dwarf galaxies with
supermassive black holes. Together, the three examples suggest that black holes lurk at the center of most of these
objects, potentially doubling the number of supermassive black holes known in the universe. The black holes make
up a high percentage of the compact galaxies' total mass, supporting the theory that the dwarfs are remnants of
massive galaxies that were ripped apart by larger galaxies.
"We still don't fully understand how galaxies form and evolve over time. These objects can tell us how galaxies
merge and collide," says Chris Ahn, doctoral candidate in the Department of Physics & Astronomy, and lead author
of the international study that published Monday in The Astrophysical Journal. "Maybe a fraction of the centers of all
galaxies are actually these compact galaxies stripped of their outer parts."
Measuring galaxies
11
The authors measured two ultra-compact dwarf galaxies, named VUCD3 and M59cO, that lie far beyond the spiral
arms of our Milky Way, orbiting massive galaxies in the Virgo galaxy cluster. They detected a supermassive black
hole in both galaxies; VUCD3's black hole has a mass equivalent to 4.4 million suns, making up about 13 percent of
the galaxy's total mass, and M59cO's black hole has a mass of 5.8 million suns, making up about 18 percent of its
total mass.
By comparison, the
monstrous black hole
at the center of the
Milky Way has a
mass of 4 million
suns, but makes up
less than .01 percent
of the galaxy's total
mass. "It's pretty
amazing when you
really think about it.
These ultra-compact
dwarfs are around
0.1 percent the size
of the Milky Way, yet
they
host
supermassive black
holes that are bigger
than the black hole
at the center of our
own galaxy," marvels
Ahn.
UU astronomers and colleagues have found two ultra-compact dwarf galaxies, VUCD3
and M59cO, with supermassive black holes. The findings suggest that the dwarfs are
likely tiny leftovers of larger galaxies that were stripped of their outer layers after
colliding into other, larger galaxies M87 and M59, respectively.
Credit: NASA/Space Telescope Science Institute
To calculate the ultra-compact dwarf galaxies' mass, the astronomers measured the movement of the stars using
the Gemini North telescope located on Mauna Kea volcano in Hawaii. The astronomers have to correct for the
distortions caused by Earth's atmosphere. They shot a laser into the sky to make a fake little star, and moved a
mirror around hundreds of times a second to undo the distortion. They then applied the technique to the ultracompact dwarf galaxies, which are so small that the corrections are necessary to measure the motions inside the
object. The technique, known as adaptive optics, brings the once blurry galaxy into focus.
They also analyzed images from the Hubble Space Telescope to measure the distribution of the stars in each
galaxy, and created a computer simulation that best fit their observations.
They found that the motion of the stars at the center of the galaxies moved much faster than those on the outside, a
classic signature of a black hole. VUCD3 and M59cO are the second and third ultra-compact dwarf galaxies found to
contain a supermassive black hole, suggesting that all such dwarfs may harbor similarly massive light-sucking
objects.
Ultra-compact dwarf galaxy mysteries
Astronomers discovered ultra-compact dwarf galaxies in the late 1990s. The objects are made up of hundreds of
millions of stars densely packed together on an average of 100 light years across. Scientists took measurements to
see what was happening inside the galaxies, and something didn't add up; the ultra-compact dwarf galaxies had
more mass than their stars alone could account for. Senior author Anil Seth, assistant professor in the Department
of Physics & Astronomy at the U, led the 2014 study that found the first ultra-compact dwarf galaxy with a
supermassive black hole. The two U-led studies make a strong case that supermassive black holes at the center of
the galaxies are responsible for the extra mass.
An alternate theory of the dwarfs is that they are just really massive star clusters -- groups of a hundred thousand
stars born at the same time. The largest star cluster in the Milky Way is three million stars, and ultra-compact dwarf
galaxies are 10 to 100 times bigger than that. "The question was, 'Is that because they form bigger star clusters with
the same process? Or are they different in some way?' This work shows that they are different," Seth continues.
"It's obvious in retrospect, because the center of a regular galaxy looks almost exactly like these objects, but that
wasn't what most people thought they were. I wasn't convinced that we were going to find a black hole when I took
12
the observations," says Seth. "This is a cool example of scientific discovery and how quickly you can reorient our
understanding of the universe."
Black holes and the formation of galaxies
Black holes are areas with such strong gravity that not even light can escape. They form when stars collapse,
leaving behind a black hole with dense mass that exerts gravitational force on the objects around it. Supermassive
black holes have a mass of more than 1 million suns, and are thought to be at the center of all big galaxies.
One explanation for the supermassive black hole inside the ultra-compact dwarf galaxies is that the galaxies were
once made up of billions of stars. The authors believe that the dwarfs were "swallowed up" and ripped apart by the
gravity of much larger galaxies. The ultra-compact dwarf black hole is the remnant of its formerly massive size. The
findings change the way that astronomers can piece together how galaxies form and evolve over time.
"We know that galaxies merge and combine all the time -- that's how galaxies evolve. Our Milky Way is eating up
galaxies as we speak," says Seth. "Our general picture of how galaxies form is that little galaxies merge to form big
galaxies. But we have a really incomplete picture of that. The ultra-compact dwarf galaxies provide us a longer
timeline to be able to look at what's happened in the past."
First 'image' of a dark matter web that connects galaxies
Researchers at the University of Waterloo have been able to
capture the first composite image of a dark matter bridge that
connects galaxies together. The scientists publish their work in a
new paper in Monthly Notices of the Royal Astronomical Society.
The composite image, which combines a number of individual
images, confirms predictions that galaxies across the universe are
tied together through a cosmic web connected by dark matter that
has until now remained unobservable.
Dark matter, a mysterious substance that comprises around 25
per cent of the universe, doesn't shine, absorb or reflect light,
which has traditionally made it largely undetectable, except
through gravity.
Dark matter filaments bridge the space
between galaxies in this false colour map.
The locations of bright galaxies are shown by
the white regions and the presence of a dark
matter filament bridging the galaxies is
shown in red.
Credit: S. Epps & M. Hudson / University of
Waterloo
"For decades, researchers have been predicting the existence of
dark-matter filaments between galaxies that act like a web-like
superstructure connecting galaxies together," said Mike Hudson, a
professor of astronomy at the University of Waterloo. "This image
moves us beyond predictions to something we can see and
measure."
As part of their research, Hudson and co-author Seth Epps, a
master's student at the University of Waterloo at the time, used a
technique called weak gravitational lensing, an effect that causes
the images of distant galaxies to warp slightly under the influence
of an unseen mass such as a planet, a black hole, or in this case,
dark matter. The effect was measured in images from a multi-year
sky survey at the Canada-France-Hawaii Telescope.
They combined lensing images from more than 23,000 galaxy pairs located 4.5 billion light-years away to create a
composite image or map that shows the presence of dark matter between the two galaxies. Results show the dark
matter filament bridge is strongest between systems less than 40 million light years apart.
"By using this technique, we're not only able to see that these dark matter filaments in the universe exist, we're able
to see the extent to which these filaments connect galaxies together," said Epps.
13
14
Schedule of Coming Events
Date
5 May
Event
Eta Aquarids Meteor Shower Peak
The meteors we currently see as members of the Eta Aquariid shower separated from Halley’s
Comet hundreds of years ago. The shower peaks at about a rate of around a meteor per minute,
although such rates are rarely seen from northern latitudes due to the low altitude of the radiant.
5 May
National Space Day
National Space Day is observed annually on the first Friday in May. This day is dedicated to the
extraordinary achievements, benefits and opportunities in the exploration and use of space. The
goal of National Space Day is to promote math, science, technology and engineering education in
young people to inspire them to pursue a career in science, especially a career in space-related
jobs. Check it out at : http://www.nationaldaycalendar.com/national-space-day-first-friday-in-may/
5 May Friday Monthly General Meeting
Night 7:30PM Topic: “Cassini at Mission End” Matthew Ota, Telescopes in Education Foundation
8 May
Monthly Planning Meeting
Monday Night
See directions on Page 4.
7:30 PM
17 May
Mercury at Greatest Western Elongation
20 May
Saturday
Evening
In Town Dark Sky Observing Session at Ridgecrest Middle School– 28915 NortbBay Rd. RPV,
Weather Permitting: Please contact Greg Benecke to confirm that the gate will be opened!
27 May
Saturday
Night
Out of Town Dark Sky Observing Session
Contact Greg Benecke to coordinate a location.
15
South Bay Astronomical Society
*********
Next General Meeting at El Camino College Planetarium
Friday, May 5th 7:30 PM
“Cassini at Mission End”
Matthew Ota, The Telescopes in Education Foundation
*********
South Bay Astronomical Society
P.O. Box 1937
Redondo Beach, CA 90278
16