AEA Astronomy Club Newsletter October 2020

Contents

AEA Astronomy Club News & Calendar p.1
Video(s) & Picture(s) of the Month p. 2
Astronomy News p. 11
General Calendar p. 13

Colloquia, lectures, mtgs. p. 13
Observing p. 16

Useful Links p. 17
About the Club p. 18

Club News & Calendar.

Club Calendar

Club Meeting Schedule: --

1 Oct

AEA

TBD

(A1/1735)

AEA Astronomy Club Meeting

TBD -- Great Courses video

Teams

5 Nov

AEA Astronomy Club Meeting

TBD -- Great Courses video

(Teams)

AEA Astronomy Club meetings are now on 1^st Thursdays at 11:30 am. For 2020: Jan. & Feb. in A1/1735, March 5 in A1/2906 and for the rest of 2020 (April to Dec.) virtual meetings on Teams.

Club News:

We need volunteers to help with:

· Assembling our new 16-inch Hubble Optics Dobs

· Installing our new software on our tablet & laptop

· Populating our club Sharepoint site with material & links to the club’s Aerowiki & Aerolink materials – Kaly Rangarajan has volunteered to help with this

· Arranging future club programs

· Managing club equipment & library (Kelly Gov volunteered to help with the library)

Astronomy Video(s) & Picture(s) of the Month

(generally from Astronomy Picture of the Day, APOD: http://apod.nasa.gov/apod/archivepix.html)

VIDEO: GW Orionis: A Star System with Tilted Rings https://apod.nasa.gov/apod/ap200929.html
Animation Illustration Credit: ESO, U. Exeter, S. Kraus et al., L. Calçada

Explanation: Triple star system GW Orionis appears to demonstrate that planets can form and orbit in multiple planes. In contrast, all the planets and moons in our Solar System orbit in nearly the same plane. The picturesque system has three prominent stars, a warped disk, and inner tilted rings of gas and grit. The featured animation characterizes the GW Ori system from observations with the European Southern Observatory's VLT and ALMA telescopes in Chile. The first part of the illustrative video shows a grand vista of the entire system from a distant orbit, while the second sequence takes you inside the tilted rings to resolve the three central co-orbiting stars. Computer simulations indicate that multiple stars in systems like GW Ori could warp and break-up disks into unaligned, exoplanet-forming rings.

VIDEO: Salt Water Remnants on Ceres https://apod.nasa.gov/apod/ap200901.html
Video Credit: Dawn Mission, NASA, JPL-Caltech, UCLA, MPS/DLR/IDA

Explanation: Does Ceres have underground pockets of water? Ceres, the largest asteroid in the asteroid belt, was thought to be composed of rock and ice. At the same time, Ceres was known to have unusual bright spots on its surface. These bright spots were clearly imaged during Dawn's exciting approach in 2015. Analyses of Dawn images and spectra indicated that the bright spots arise from the residue of highly-reflective salt water that used to exist on Ceres' surface but evaporated. Recent analysis indicates that some of this water may have originated from deep inside the dwarf planet, indicating Ceres to be a kindred spirit with several Solar System moons, also thought to harbor deep water pockets. The featured video shows in false-color pink the bright evaporated brine named Cerealia Facula in Occator Crater. In 2018, the mission-successful but fuel-depleted Dawn spacecraft was placed in a distant parking orbit, keeping it away from the Ceres' surface for at least 20 years to avoid interfering with any life that might there exist.

VIDEO: A Thousand Meteors https://apod.nasa.gov/apod/ap200912.html
Video Credit & Copyright: Greg Priestley

Explanation: Over a thousand meteors flash through the night in this intriguing timelapse video. Starting in April 2019 the individual video frames were selected from 372 relatively clear nights of imaging from an automated wide-field observatory in rural New South Wales Australia. Arranged by local sidereal time, a timekeeping system that uses the positions of stars to measure Earth's rotation, the frames follow the full annual progression of constellations through the wide field of view seen from 33 degrees south latitude. They capture a diverse array of meteors including sporadic meteors, bright fireballs, and shower meteors (plus a lightning sprite), during the period. All frames were processed consistently and so show real variations in the local sky conditions.

Filaments of the Cygnus Loop
Image Credit: ESA/Hubble & NASA, W. Blair; Acknowledgement: Leo Shatz

Explanation: What lies at the edge of an expanding supernova? Subtle and delicate in appearance, these ribbons of shocked interstellar gas are part of a blast wave at the expanding edge of a violent stellar explosion that would have been easily visible to humans during the late stone age, about 20,000 years ago. The featured image was recorded by the Hubble Space Telescope and is a closeup of the outer edge of a supernova remnant known as the Cygnus Loop or Veil Nebula. The filamentary shock front is moving toward the top of the frame at about 170 kilometers per second, while glowing in light emitted by atoms of excited hydrogen gas. The distances to stars thought to be interacting with the Cygnus Loop have recently been found by the Gaia mission to be about 2400 light years distant. The whole Cygnus Loop spans six full Moons across the sky, corresponding to about 130 light years, and parts can be seen with a small telescope toward the constellation of the Swan (Cygnus).

Enceladus in Infrared
Image Credit: VIMS Team, SSI, U. Arizona, U. Nantes, CNRS, ESA, NASA

Explanation: One of our Solar System's most tantalizing worlds, icy Saturnian moon Enceladus appears in these detailed hemisphere views from the Cassini spacecraft. In false color, the five panels present 13 years of infrared image data from Cassini's Visual and Infrared Mapping Spectrometer and Imaging Science Subsystem. Fresh ice is colored red, and the most dramatic features look like long gashes in the 500 kilometer diameter moon's south polar region. They correspond to the location of tiger stripes, surface fractures that likely connect to an ocean beneath the Enceladus ice shell. The fractures are the source of the moon's icy plumes that continuously spew into space. The plumes were discovered by by Cassini in 2005. Now, reddish hues in the northern half of the leading hemisphere view also indicate a recent resurfacing of other regions of the geologically active moon, a world that may hold conditions suitable for life.

ISS Transits Mars
Image Credit & Copyright: Tom Glenn

Explanation: Yes, but have you ever seen the space station do this? If you know when and where to look, watching the bright International Space Station (ISS) drift across your night sky is a fascinating sight -- but not very unusual. Images of the ISS crossing in front of the half-degree Moon or Sun do exist, but are somewhat rare as they take planning, timing, and patience to acquire. Catching the ISS crossing in front of minuscule Mars, though, is on another level. Using online software, the featured photographer learned that the unusual transit would be visible only momentarily along a very narrow stretch of nearby land spanning just 90 meters. Within this stretch, the equivalent ground velocity of the passing ISS image would be a quick 7.4 kilometers per second. However, with a standard camera, a small telescope, an exact location to set up his equipment, an exact direction to point the telescope, and sub-millisecond timing -- he created a video from which the featured 0.00035 second exposure was extracted. In the resulting image capture, details on both Mars and the ISS are visible simultaneously. The featured image was acquired last Monday at 05:15:47 local time from just northeast of San Diego, California, USA. Although typically much smaller, angularly, than the ISS, Mars is approaching its maximum angular size in the next few weeks, because the blue planet (Earth) is set to pass its closest to the red planet (Mars) in their respective orbits around the Sun.

Orion in Depth
Illustration Credit & Copyright: Ronald Davison

Explanation: Orion is a familiar constellation. The apparent positions of its stars in two dimensions create a well-known pattern on the bowl of planet Earth's night sky. Orion may not look quite so familiar in this 3D view though. The illustration reconstructs the relative positions of Orion's bright stars, including data from the Hipparcus catalog of parallax distances. The most distant star shown is Alnilam. The middle one in the projected line of three that make up Orion's belt when viewed from planet Earth, Alnilam is nearly 2,000 light-years away, almost 3 times as far as fellow belt stars Alnitak and Mintaka. Though Rigel and Betelgeuse apparently shine brighter in planet Earth's sky, that makes more distant Alnilam intrinsically (in absolute magnitude) the brightest of the familiar stars in Orion. In the Hipparcus catalog, errors in measured parallaxes for Orion's stars can translate in to distance errors of a 100 light-years or so.

Biomarker Phosphine Discovered in the Atmosphere of Venus
Image Credit: ISAS, JAXA, Akatsuki; Processing: Meli thev

Explanation: Could there be life floating in the atmosphere of Venus? Although Earth's planetary neighbor has a surface considered too extreme for any known lifeform, Venus' upper atmosphere may be sufficiently mild for tiny airborne microbes. This usually disfavored prospect took an unexpected upturn yesterday with the announcement of the discovery of Venusian phosphine. The chemical phosphine (PH3) is a considered a biomarker because it seems so hard to create from routine chemical processes thought to occur on or around a rocky world such as Venus -- but it is known to be created by microbial life on Earth. The featured image of Venus and its thick clouds was taken in two bands of ultraviolet light by the Venus-orbing Akatsuki, a Japanese robotic satellite that has been orbiting the cloud-shrouded world since 2015. The phosphine finding, if confirmed, may set off renewed interest in searching for other indications of life floating high in the atmosphere of our Solar System's second planet out from the Sun.

GW190521: Unexpected Black Holes Collide
Illustration Credit: Raúl Rubio (Virgo Valencia Group, The Virgo Collaboration)

Explanation: How do black holes like this form? The two black holes that spiraled together to produce the gravitational wave event GW190521 were not only the most massive black holes ever seen by LIGO and VIRGO so far, their masses -- 66 and 85 solar masses -- were unprecedented and unexpected. Lower mass black holes, below about 65 solar masses are known to form in supernova explosions. Conversely, higher mass black holes, above about 135 solar masses, are thought to be created by very massive stars imploding after they use up their weight-bearing nuclear-fusion-producing elements. How such intermediate mass black holes came to exist is yet unknown, although one hypothesis holds that they result from consecutive collisions of stars and black holes in dense star clusters. Featured is an illustration of the black holes just before collision, annotated with arrows indicating their spin axes. In the illustration, the spiral waves indicate the production of gravitational radiation, while the surrounding stars highlight the possibility that the merger occurred in a star cluster. Seen last year but emanating from an epoch when the universe was only about half its present age (z ~ 0.8), black hole merger GW190521 is the farthest yet detected, to within measurement errors.

A Falcon 9 Moon
Image Credit & Copyright: Katie Darby

Explanation: Illuminating planet Earth's night, full moons can have many names. This year the last full moon of northern hemisphere summer was on September 2, known to some as the Full Corn Moon. A few days earlier on August 30 this almost full moon rose just before sunset though, shining through cloudy skies over Cape Canaveral Air Force Station on Florida's Space Coast. A well-timed snapshot caught the glare of rocket engines firing below the lunar disk, a Falcon 9 rocket's first stage successfully returning to Cape Canaveral's landing zone 1. About 9 minutes earlier, the same SpaceX Falcon 9 rocket had launched the SAOCOM 1B satellite toward polar orbit. The fourth launch for this reusable Falcon 9 first stage, it was the first launch to a polar orbit from Cape Canaveral since 1969.

A Halo for Andromeda
Digital Illustration Credit: NASA, ESA, J. DePasquale and E. Wheatley (STScI) and Z. Levay

Explanation: M31, the Andromeda Galaxy, is the closest large spiral galaxy to our Milky Way. Some 2.5 million light-years distant it shines in Earth's night sky as a small, faint, elongated cloud just visible to the unaided eye. Invisible to the eye though, its enormous halo of hot ionized gas is represented in purplish hues for this digital illustration of our neighboring galaxy above rocky terrain. Mapped by Hubble Space Telescope observations of the absorption of ultraviolet light against distant quasars, the extent and make-up of Andromeda's gaseous halo has been recently determined by the AMIGA project. A reservoir of material for future star formation, Andromeda's halo of diffuse plasma was measured to extend around 1.3 million light-years or more from the galaxy. That's about half way to the Milky Way, likely putting it in contact with the diffuse gaseous halo of our own galaxy.

Astronomy News:

A spherical star cluster has surprisingly few heavy elements

https://www.sciencenews.org/article/globular-star-cluster-surprising-few-heavy-elements

Called RBC EXT8, the cluster challenges some theories of how galaxies form and evolve

By Lisa Grossman

9 HOURS AGO

A strange, newly measured clump of stars orbiting the nearby Andromeda galaxy has the lowest level of heavy chemical elements ever seen in one of these mysterious star clusters. Named RBC EXT8, this globular cluster is also surprisingly massive, challenging theories for how such clusters and some galaxies form, astronomers report online October 15 in Science.

“It’s a very unusual object,” says astrophysicist Oleg Gnedin of the University of Michigan in Ann Arbor, who was not involved in the new discovery.

Globular clusters are crowded, spherical collections of stars that orbit a galaxy’s center, though most, including RBC EXT8, live in the galactic outskirts. The clusters are typically billions of years old, so their stars tend to be chemically pristine, meaning they formed before the universe had time to create much of any of the elements heavier than hydrogen or helium, which astronomers lump together as “metals.”

Previous observations of these clusters in the Milky Way and other galaxies had suggested that there’s a limit to how low a globular cluster’s metal content can be. The most metal-poor clusters were about 300 times less rich in heavy elements like iron than the sun, but no less.

But spectra of RBC EXT8, some 2.5 million light-years away, show that the cluster’s metal content is about 800 times less than the sun’s. The globular cluster that held the previous record for lowest “metallicity” has three times that amount.

“It was completely unexpected that we would find a globular cluster that is so metal poor,” says astronomer Søren Larsen of Radboud University in Nijmegen, the Netherlands.

The bigger, fuzzy blob in the inset image at left is RBC EXT8, a globular cluster that orbits about 88,000 light-years from the center of the galaxy Andromeda (shown at right). The cluster has surprisingly few heavy elements for its size, a new study finds.© 2020 ESASKY, CFHT

What’s more, given its metal-poor status, this cluster is surprisingly massive, weighing about 1.14 million times the mass of the sun. (A mid-weight globular cluster is about 100,000 solar masses, but some clusters reach 3 million solar masses. RBC EXT8 is heavy, but not the heaviest.)

That mass makes the cluster even harder to explain because across the cosmos, the more massive a galaxy or cluster is, the more heavy elements it normally has.

There are several potential explanations for that trend, but one is simply that more massive galaxies or globular clusters have more stars. A star fuses heavy elements in its core and sprinkles them around its host cluster or galaxy as it ages. Sufficiently massive stars can explode in a supernova, spreading those metals to become part of the next generation of stars (SN: 8/9/19). So more stars means more opportunity for metals to accumulate locally.

More massive objects also have the advantage of gravity, which lets them better hold on to the metals that they do have and remain a cohesive group for billions of years. Less massive globular clusters dissolve into their host galaxies over time.

Those trends together could have explained the apparent “metallicity floor” for globular clusters — all of the less massive, more metal-poor clusters have broken apart over the eons.

RBC EXT8 turns that conventional wisdom on its head. “It’s too big to have as low metallicity as it has,” Gnedin says. “That’s the conundrum.”

General Calendar:

Colloquia, Lectures, Seminars, Meetings, Open Houses & Tours:

Colloquia: Carnegie (Tues. 4pm), UCLA, Caltech (Wed. 4pm), IPAC (Wed. 12:15pm) & other Pasadena (daily 12-4pm): http://obs.carnegiescience.edu/seminars/

1 Oct

AEA Astronomy Club Meeting

TBD -- Great Courses video

(Teams)

Cancelled for now

Friday Night 7:30PM SBAS Monthly General Meeting

in the Planetarium at El Camino College (16007 Crenshaw Bl. In Torrance)

Oct. 15 The von Kármán Lecture Series: 2020

An Astronomical View

The Hubble Ultra Deep Field Image (see description on the right, below)

Thursday, October 15, 2020

2020 October

A spherical star cluster has surprisingly few heavy elements

Called RBC EXT8, the cluster challenges some theories of how galaxies form and evolve

Oct. 15 The von Kármán Lecture Series: 2020

Galaxy of Horrors: Terrifying Real Planets

DR. DONALD BROWNLEE

THE GOLDEN AGE OF SAMPLE RETURN MISSIONS FROM SPACE: WHAT COMET SAMPLES HAVE TOLD US ABOUT THE ORIGIN OF THE SOLAR SYSTEM

Telescope, Binocular & Accessory Buying Guides