Category Archives: lectures

Seattle Astronomy calendar, week of June 15

Summer arrives in the Northern Hemisphere this week, there will be an array of public astronomy events, and we celebrate a couple of anniversaries of women in space.

The Seattle Astronomical Society will hold its monthly meeting at 7:30 p.m. Wednesday, June 17 in room A102 of the Physics/Astronomy Building on the University of Washington campus in Seattle. As of this writing, the guest speaker presentation was still listed as TBA; watch the SAS website for updates.


The Theodor Jacobsen Observatory at the University of Washington. Photo: Greg Scheiderer.

Later that evening, starting at 9 p.m., the University of Washington will host one of its bi-monthly open houses at the Theodor Jacobsen Observatory. Rebecca Kemmerer, a senior in physics and astronomy, will give a talk titled, “Stars and Their Place in the Milky Way.” Kemmerer’s presentation will include a discussion of the different types of stars in our galaxy and the ways that their masses influence how they are born, live, and die. It’s free, but reservations are strongly encouraged for the talk; the classroom is small and fills up quickly! Volunteers from the Seattle Astronomical Society will be on hand to give tours of the observatory and, if weather permits—and we’re optimistic it will!—will offer a look through the facility’s vintage telescope.

Women in space

Two anniversaries of women in space come up this week. Valentina Tereshkova of the Soviet Union became the first woman in space when she flew on Vostok 6 on June 16, 1963. That flight is still the only solo space flight by a woman. Twenty years and two days later, on June 18, 1983, Sally Ride became the first U.S. woman to fly in space when she launched on the crew of the Challenger and STS-7. Ride has been on our pages a lot of late. Her birthday was May 26, and we also enjoyed Lynn Sherr‘s recent biography of the astronaut, Sally Ride: America’s First Woman in Space (Simon and Schuster, 2014). Sherr was in Seattle last year and spoke about Ride.

Busy Saturday of astro events

There will be a lot to choose from for astronomy enthusiasts on Saturday, June 20. The day’s festivities kick off with a talk by Rob Manning, the chief engineer for the Mars rover Curiosity. Manning will talk about his book, Mars Rover Curiosity: An Inside Account from Curiosity’s Chief Engineer (Smithsonian Books, 2014). The talk will be at 2 p.m. at the Museum of Flight. For our money the landing of Curiosity on Mars was one of our greatest engineering achievements. Here’s a chance to get the inside story. Pick up the book in advance. Manning will sign copies after his presentation.

Summer begins Sunday at the solstice, which happens at 9:38 a.m. Pacific time. Saturday evening Alice Enevoldsen of Alice’s Astro Info will host a solstice sunset watch at Solstice Park in West Seattle, with the gathering beginning about 8:45 p.m. for the sunset, which will be at about 9 p.m. Enevoldsen is a NASA Solar System Ambassador, and this will be her 25th seasonal sunset watch at the park. They’re fun and informative!

The Seattle Astronomical Society will host two public star parties June 20, at Green Lake in Seattle and Paramount Park in Shoreline. Both will begin at 9 p.m., weather permitting. The Tacoma Astronomical Society also plans a public night Saturday at 9 p.m. at the Fort Steilacoom campus of Pierce College. Presenter Chuck Jacobsen will talk about the Sun, and, weather permitting, members will be on hand with telescopes for a look at what’s up in the sky.

Happy Father’s Day

In case it slipped your mind, Father’s Day is June 21, and we think dear old dad would love a telescope, eyepiece, or astronomy book as a present! There’s a lovely selection of such things in the Seattle Astronomy Store!


Understanding relativity

Jeffrey Bennett thinks we ought to be teaching kids about relativity in grade school because Einstein’s theories explain so much about everything, from why the Sun shines to gravity to how your GPS system knows where you are. His book What Is Relativity?: An Intuitive Introduction to Einstein’s Ideas, and Why They Matter (Columbia University Press, 2014) does a marvelous job of making sense of some of the seemingly strange consequences of relativity.

Jeffrey Bennett

Jeffery Bennett spoke about his book “What is Relativity?” at the meeting of the Seattle Astronomical Society in April. Photo: Greg Scheiderer.

Bennett spoke about relativity at a meeting of the Seattle Astronomical Society in April. He’s on a tour marking the International Year of Light and the centennial of general relativity.

Bennett noted that a key idea of relativity is that it is motion that is relative. He illustrated this by talking about a plane flight between Nairobi and Quito, two cities on Earth’s equator. The plane leaves Nairobi, flies at 1,670 kilometers per hour, which happens to be the Earth’s rotational speed at the equator, and then lands in Quito.

A person standing on Earth would say the plane flew west at 1,670 kilometers per hour. However, a person watching this flight from the Moon would have seen the plane take off, hover while the Earth spun under it, and then land once Quito arrived. That person would peg the plane’s speed at zero. Who is right?

“Einstein’s answer is both are correct,” Bennett said, “and neither one makes sense unless you specify what you’re measuring your motion relative to.”

Absolutes are key in relativity

Bennett explained that the heart of relativity is not what is relative, but the two things that are absolute: the laws of nature and the speed of light. He used an airplane flight to illustrate the latter point as well.

If you’re in a plane going 500 miles an hour, and you throw a ball forward at 10 miles per hour, a person on the ground would see that ball going at 510 miles per hour—the speed of the plane plus the speed of the ball. However, if you shined a flashlight forward, the light would go at the speed of light, not light-plus-500. The motion of the plane does not effect the speed of light.

“It is not effected by motion of either the observer or the source,” Bennett explained. “It’s an experimentally measured fact that the speed of light is the same for everyone, and from this single fact, if you do thought experiments, you can derive all the seemingly strange consequences of relativity.”

Not so fast!

The book is loaded with such thought experiments that help one get a grasp on the concepts. One Bennett talked about at length is the impossibility of exceeding the speed of light. Imagine a spaceship with theoretically unlimited speed. If Bennett, as the pilot, turns on the ship’s headlights, both he and an observer outside the craft would see the light from the headlights moving ahead of the ship at the speed of light.

“If the headlights are going the speed of light then I’m going less than the speed of light,” Bennett explained. “We set no limits, and yet the fact that the speed of light is the same for everyone means I cannot reach it or exceed it.”

“This is not a challenge to be broken technologically,” he continued. “It’s something that simply cannot be done. In fact, the idea that you cannot go faster than the speed of light is so well established that not even science fiction writers try to break it. That’s why they go through wormholes or into hyperspace or make warp drive to bend spacetime, because science fiction writers know you cannot travel through the universe at a speed greater than the speed of light. It simply can’t be done because the speed of light is the same for everyone.”

Bennett explained that the predictions of the effects of relativity have been tested exhaustively, and much of what we see in our everyday lives serves as proof that it works.

“The sun shining is evidence that relativity is correct,” he said. “Every time you turn on a computer or a light our a cell phone you’re testing the theory of relativity and showing that it works. This is an extremely well-established idea.”

Uncommon sense

Bennett speaks about relativity often and finds that many people have a hard time with it because they feel it violates their common sense.

“The good news is it actually doesn’t violate your common sense,” Bennett said. “The bad news is the reason it doesn’t violate your common sense is because when it comes to these ideas, you just don’t have any common sense.”

Why not? Common sense, by definition, derives from everyday experiences.

“These effects of relativity become noticeable when you’re traveling at speeds close to the speed of light. And guess what? You’ve never done that,” Bennett said.


Jeffrey Bennett at the UW's physics/astronomy auditorium. Photo: Greg Scheiderer.

Jeffrey Bennett at the UW’s physics/astronomy auditorium. Photo: Greg Scheiderer.

When it comes to gravity, Newton had the math pretty well figured out, but even he thought the notion of one massive body acting somehow on another had sort of a weird, magical quality. Einstein came along and figured out that gravity is simply curvature of spacetime.

“This is one of the fundamental ideas of general relativity,” Bennett said. “Gravity is no longer a magical force at a distance, it’s just objects following the natural contours of spacetime as they are shaped by masses in the universe.”

Evidence that this is true includes gravitational lensing, gravitational time dilation, black holes, and gravitational waves. The first has been seen, the second measured, and we’ve seen the effects of the third. Bennett said scientists are optimistic they’ll actually detect gravitational waves in experiments this year.

Why relativity matters

Bennett feels that scientific knowledge, understanding of reality, and the inspiring human potential to do great things through science are among the reasons that relativity matters. A fourth reason is highly philosophical.

“In a sense, every action you ever take is a permanent part of spacetime,” he said. “Your life is a series of events, and this means that when you put them all together you are creating your own indelible mark on the universe. Perhaps if everyone understood that, we might all be a little more careful to make sure that the mark we leave is one that we are proud of. This may be a little naive, but I actually believe that if everyone understood the theory of relativity we’d all treat each other a little bit better.”

What Is Relativity? is an outstanding book that dives deeper into these concepts and leaves the reader with a better understanding of relativity.


Jim Peebles and the cosmic microwave background

Jim Peebles is a giant of science. He was studying physical cosmology long before it was considered a serious, quantitative branch of physics, and has done much to establish its respectability. Peebles also has contributed a great deal to the thinking about dark matter and dark energy.

Jim Peebles

Legendary physical cosmologist Jim Peebles makes a point during a lecture at the University of Washington May 19, 2015. Photo: Greg Scheiderer.

Peebles, the Albert Einstein Professor of Science emeritus at Princeton University, gave a lecture titled “Fifty Years of the Cosmic Microwave Background” recently at the University of Washington.

“The last 50 years have seen a truly transformative advance in our understanding of the world around us,” Peebles noted in opening the talk. He explained that the idea of the Big Bang had been bouncing around for a while, and in the early 1960s folks were setting out to prove it as fact. Peebles was a research associate with Bob Dickie at Princeton, and the two of them advanced the idea of the cosmic microwave background. Along with research associates Peter Roll and Dave Wilkinson, they built a microwave radiometer to detect the signature of a hot Big Bang.

Little did they know that the evidence had already been spotted and measured.

Several years earlier, Bell Telephone Laboratories in New Jersey had done an experiment in communication using microwave radiation.

“This was an important forerunner to the sight of our students wandering around campus staring at their cell phones,” Peebles quipped. The experiment also found a lot of background radiation despite the best engineering efforts to eliminate it. By 1963 Bob Wilson and Arno Penzias at Bell wanted to use the technology to do radio astronomy, but they needed to solve the problem of the system noise.

“The Bell people had this constant irritation,” Peebles said. “They were getting more radiation than they expected from their communications experiments.”

It must be the CMB

Peebles had already been doing lectures about the possibility of the cosmic microwave background. By 1964 the Bell folks and the Princeton people got together. Peebles and Dickie figured that the system noise plaguing Wilson and Penzias was actually the cosmic microwave background.

“We had the possibility of a great discovery,” Peebles recalled. “We already knew right away that this was something new. That was exciting because you have a new phenomenon, something new to measure, and something new to make theories about.”

Measuring to prove it

The measurement piece took a quarter century, and was accomplished with spectacular precision by two experiments just months apart in 1990: NASA’s Cosmic Background Explorer (COBE) satellite, headed by John Mather of the Goddard Space Flight Center and George Smoot of Berkeley, and a rocket-borne experiment launched by Herb Gush of the University of British Columbia, along with Mark Halpern and Ed Wishnow. Both projects, in development for about 15 years, made measurements that meshed perfectly with the theoretical predictions for the cosmic microwave background.

COBE all-sky map

COBE all-sky map. Image: NASA.

“It’s a glorious piece of evidence, I would say an iconic piece, that shows tangibly that the universe had to have evolved from a different state, because this is a thermal spectrum,” Peebles marveled. “Our universe as it is now is transparent for this radiation. There is no way it could force the radiation to relax to this thermal equilibrium. The universe had to have evolved from a state in which it was dense and hot enough to have relaxed to equilibrium and then expanded away from it.”

Interestingly, this is a tale of “missed it by that much” when it comes to Nobel Prizes. Dickie, Peebles, and the Princeton team were well on their way to making the measurement when they learned that Wilson and Penzias had already stumbled across it. The latter two won the Nobel in 1978 for their work. Mather and Smoot won the Nobel in 2006 for their COBE measurements, but Gush may have beaten them to it had it not been for equipment troubles that delayed the launch of his experiment.


Cannibal galaxies and asteroid mining

Our galaxy is a cannibal, and we have quite an appetite for resources in our own little corner of the Milky Way, too. That’s what we learned at the latest Astronomy On Tap event in Seattle, held last week at Bad Jimmy’s Brewing Company in Ballard.

John Lurie

John Lurie talked about the cannibal Milky Way galaxy at Astronomy on Tap Seattle. Photo: Greg Scheiderer.

John Lurie, a graduate student in astronomy at the University of Washington who studies the structure of the Milky Way, started his talk with a bit of history. For millennia, up until recently when light pollution made the Milky Way invisible to a great many of us, people saw it and made up stories about what it was. To Lurie’s mind, some of the violent images of Greek mythology seem fitting.

“Our Galaxy is actually a cannibal, and it likes to eat other galaxies,” he said. “Not only that, but the entrails of its victims are strewn across the heavens.”

We didn’t know much at all about the Milky Way until Galileo pointed his telescope at it four centuries ago and wrote down that he saw individual stars.

“Up until the beginning of the 20th century that was basically it,” Lurie said. “The entire universe, as far as we knew, was contained in the Milky Way.”

New learning

Fast forward to Edwin Hubble, who used a much larger telescope, the 100-inch at Mt. Wilson, to look at cepheid variables. Hubble calculated that what was then known as the “Andromeda nebula” was about 2.5 million light years distant—way too far away to be part of our galaxy. It was another galaxy.

If this ball were the Sun, the next nearest star would be in New York. Photo: Greg Scheiderer.

If this ball were the Sun, the next nearest star would be in New York. Photo: Greg Scheiderer.

Galaxies seem awfully far-flung to be cannibalizing each other, but Lurie explained that they’re actually relatively close together. He noted that if the Sun were a yellow ball a bit smaller than a pint beer glass (an apt analogy given the locale of the talk) our next nearest stellar neighbor would be in New York. However, if the disk of the Milky Way galaxy were represented by a frisbee, the next nearest major galaxy would be inside Bad Jimmy’s, a mere 20 feet away. In addition, between us and Andromeda are a number of dwarf galaxies. Astronomers have found streams of stars that are evidence that the Milky way has collided with one of them, the Sagitarius dwarf galaxy.

“That’s why I claim that our galaxy is actually a cannibal,” Lurie said. “It’s in the process of eating this galaxy. Gravitational tidal forces of the Milky Way are tearing the stars off of this dwarf galaxy and they’re being strewn out into space.”

Bigger fish

Lurie says that when it comes to cannibal galaxies there’s always someone bigger out there.

“The Andromeda galaxy is coming to get us,” he said. “It’s a little bit bigger than us, and we’re on a collision course.”

Not to worry. It won’t happen for another four billion years or so, and since individual stars are so spread out, the likelihood that two would collide is pretty small. Some stars could get flung out of the galaxy, but mostly the Milky Way and Andromeda will eventually coalesce into one big galaxy.

Mining asteroids

Matt Beasley of Planetary Resources explained the best types of asteroids for mining useful materials. Photo: Greg Scheiderer.

Matt Beasley of Planetary Resources explained the best types of asteroids for mining useful materials. Photo: Greg Scheiderer.

Closer to home folks are thinking of mining nearby asteroids for the valuable materials they contain. Dr. Matthew Beasley, a senior engineer at Redmond-based Planetary Resources, gave a talk titled, “Resources on Asteroids: What’s There, How Much, and Why?”

Beasley noted that there are 872 known asteroids of about one-kilometer orbiting in near-Earth space, and perhaps as many as 20,000 smaller ones down to about 100 meters. That’s a lot of potential targets for asteroid mining.

Why go to the trouble?

“Asteroids are extremely rich in useful materials,” Beasley said.

There are three main types of asteroids. Beasley explained that the first ones Planetary Resources will target are C-type carbonaceous asteroids. These make up about 75 percent of all asteroids, but only about six percent of the known near-Earth asteroids. They’re hard to spot because they’re so dark in color, like a lump of black clay. C-type asteroids are around 20 percent water by mass, and that’s what makes them appealing. Water is handy for space explorers to drink, and it can be broken down into hydrogen and oxygen for spacecraft fuel.

“One 75-meter C-type asteroid full of water could have fueled all of the shuttle missions,” Beasley noted. It will cost a lot less to pick up water and fuel in space than it does to launch them into space from Earth.

The second target type of asteroid is the M-type, which is heavily metallic. M-type asteroids contain virtually no water, but are rich in metals such as nickel, iron, and platinum, and maybe some silicates.

“One 500-meter metallic contains more platinum than has ever been mined by humanity,” Beasley said, adding that all of the platinum on Earth probably got here through collisions with asteroids. Platinum-group metals are highly sought after for electronics and other manufacturing, and all of the metals could be useful for building things in space. As with the water, it’s a lot less expensive to find it out there than it is to take it with you.

aotjuneA third common asteroid is the stony S-type. These contain no water, some metals, but basically are between 75 and 90 percent silicates.

“They’re a little light on volatiles and organics, lots of rock,” Beasley said, noting there’s little interest in this type of asteroid. “Basically, they’re fill dirt.”

The next Astronomy on Tap Seattle is set for 7 p.m. Wednesday, June 24 at Bad Jimmy’s. They’ll be viewing the first episode of the original Cosmos television series, featuring Carl Sagan. Idea: grab the book to read beforehand; you’ll have a leg up in the Cosmos trivia competition at the event! A guest speaker will introduce the episode, lead discussions and answer questions about it, and give updates on discoveries since the series first aired. It’s free, RSVP here.


Seattle Astronomy calendar, week of May 18

There are a lot of great events requiring some difficult choices on this week’s calendar.

Prof. Jim Peebles speaks Tuesday at the University of Washington. Photo: Princeton.

Prof. Jim Peebles speaks Tuesday at the University of Washington. Photo: Princeton.

On Tuesday, May 19, Professor P.J.E. Peebles, Albert Einstein Professor of Science at Princeton University, will give a guest lecture at the University of Washington sponsored by the departments of physics and astronomy. Titled “50 Years of the Cosmic Microwave Background: What We Have Learned, and What Questions Remain,” Peebles’ lecture will explore the science behind the Big Bang and new searches for dark matter and dark energy. The lecture, at 7 p.m. in room A102 of the Physics/Astronomy Building on the UW campus in Seattle, is free, but reservations are required.

Jennifer Wu photography

Light Painting by Jennifer Wu.

Light Painting by Jennifer Wu.

At the same hour astrophotographers may be interested in a presentation by Jennifer Wu at the Mountaineers Seattle Program Center. Wu, the co-author of Photography Night Sky: A Field Guide for Shooting After Dark, is a nature and landscape photographer specializing in creating stunning images of the night sky and stars. Since 2009, she has served as a Canon Explorer Of Light, one of just 36 photographers worldwide to be recognized with that honor.

Tickets are free for students, $14 for Mountaineers members, $16 for non-members. The event starts at 7 p.m. Tuesday, May 19 at the Mountaineers’ Center, 7700 Sand Point Way NE in Seattle.

Astronomy on Tap returns

aot3Enjoy beer and astronomy at the third event of the spring with Astronomy on Tap Seattle on Wednesday, May 20 at 7 p.m. at Bad Jimmy’s Brewing Company in Ballard. UW astronomy grad student John Lurie will give a short talk about our understanding of the evolution of the Milky Way, titled, “Our Galaxy is a Cannibal.” Dr. Matt Beasley of Planetary Resources will discuss asteroid mining. In addition to the brew and lectures, there will be astronomy trivia contests and yummy prizes from Trophy Cupcakes.

Catch our recaps of the first and second Astronomy on Tap Seattle events, and we’ll see you at number three on Wednesday. It’s free; make a reservation here.

Seattle Astronomical Society

The Seattle Astronomical Society will hold its monthly meeting Wednesday, May 20 at 7:30 p.m. in room A102 of the Physics/Astronomy Building on the University of Washington campus in Seattle. Developer Jonathan Fay will talk about Microsoft WorldWide Telescope, free software you can use to plan observations, control a telescope, explore astronomical data sets, or create custom tours for educational outreach.

Back to TJO

Theodor Jacobsen Observatory

May 20 is the third Wednesday of the month, which means it’s time for another open house at the Theodor Jacobsen Observatory on the UW campus. The event gets under way at 9 p.m. Undergrad Boren Li will give a talk titled, “Comparative Planetology: Where Will We Go?” Li will compare conditions on other planets to those on Earth and summarize our best prospects for colonization.

The talks are free but reservations are strongly recommended. Volunteers from the Seattle Astronomical Society will give tours of the observatory and, weather permitting, share a look through its vintage telescope.

Northern lights flick at PacSci

Acclaimed Norwegian solar physicist Pål Brekke will be at the Pacific Science Center Thursday, May 21, for a discussion of the fascinating phenomena of the aurora borealis. They’ll show Brekke’s new 25-minute documentary The Northern Lights: A Magic Experience at 7:30 p.m. in the center’s PACCAR Theater. The film tells the full story of the aurora and includes tips on how to take your own exquisite northern lights photos.

After the screening Brekke will talk about his experience as a longtime observer of the northern lights and about his work on the documentary. Admission is $5. View the trailer for the film below.

Weekend star parties

The Seattle Astronomical Society will hold its free public star parties Saturday, May 23 at two locations: Green Lake in Seattle and Paramount Park in Shoreline. Both events will start at 9 p.m. if the weather is suitable for stargazing.

Saturn at opposition

Saturn will be at opposition Friday, meaning we’ve arrived at the best time this year for observing the ringed planet. Jupiter and Venus are still great targets in the early evening as well. This Week’s Sky at a Glance from Sky & Telescope magazine has more observing highlights for the week.

Keep on top of area astronomy events with the Seattle Astronomy calendar.



Game of Thrones and black holes at latest Astronomy on Tap

The extreme seasons on the popular HBO series Game of Thrones and supermassive black holes were the subjects of talks at the most recent Astronomy on Tap event held at Bad Jimmy’s Brewing Company in Ballard.

AoT vs. GoT: Reasons for the (Extreme) Seasons

Russell Deitrick

Russell Deitrick makes a point during his talk at Astronomy on Tap II at Bad Jimmy’s Brewing Company. Photo: Greg Scheiderer.

Russell Deitrick is an graduate student in astronomy at the University of Washington, studying models of the dynamics of exoplanets in multi-planet systems. He is particularly interested in how interactions between planets with high eccentricity and high mutual-inclination might affect habitability of those planets. That, it would seem, makes him the perfect one to figure out what could cause the sort of long, severe, and unpredictable seasons the characters on Game of Thrones experience.

Deitrick started with a quick primer on what causes seasons. The main cause is the axial tilt, or obliquity, of the planet. Earth, for example, has an axial tilt of about 23 1/2 degrees, and when a pole is inclined toward the Sun its hemisphere enjoys summer.

There are several ways to mess with the seasons, Deitrick explained. Our Moon stabilizes precession—the wobble of the orbital axis like a top—so if a planet doesn’t have a large moon, precession would be greater and there would be more variance. You could alter the orbit itself, making it highly eccentric.

Other factors that can change climate include volcanism, solar variability, or having a planet in a binary star system.

Deitrick ran computer models in which all of these varied wildly. The simulations didn’t match the show.

“Eccentricity can’t really explain the duration of the seasons on Game of Thrones,” Deitrick said. “If you’re at high eccentricity, you may have a very long winter, but you’re going to have a correspondingly short summer, and the seasons are going to be the same length.”

He noted that changing the obliquity of the axis can explain everything except the long duration of the seasons. Volcanos can create long seasons, but Deitrick said that doesn’t fit in with the show.

“The problem with the volcanic winter is that it’s possibly too random,” he said. “The fact that the seasons are quasi-predictable suggests that it probably isn’t related to volcanos.”

He said solar variability takes to long to create climate change on the short time scale of a season, and a binary star system doesn’t appear to be part of the story in Game of Thrones.

“You’d think they’d mention somewhere in the series that there were two suns,” he said.

“None of these can explain that long night, that generation of darkness,” Deitrick added.

“The seasons on Game of Thrones probably can’t be explained by a single theory,” Deitrick concluded. “So they’re probably magic.”

Supermassive black holes: size matters

Michael Tremmel

Michael Tremmel is working on figuring out how supermassive black holes came to be. Photo: Greg Scheiderer.

Michael Tremmel, another UW astronomy grad student, took on an equally mysterious if less fictional topic in his Astronomy on Tap talk: supermassive black holes.

Tremmel explained that an ordinary black hole—one of between one and 10 solar masses—is the result of simple stellar evolution.

“When a massive star runs out of fuel and explodes in a supernova, the core of the star continues collapsing and forms a black hole,” he said.

The problem is that supermassive black holes can be of billions of solar masses and could not have formed in the same way.

“It’s still an open question where these black holes came from,” Tremmel said, “but we think that they must have formed very, very early on in the universe when the first stars that exist were beginning to form. Before there were galaxies, before there were stars, there were supermassive black holes.”

We’ve never seen a black hole because they don’t emit light. Their gravity is such that even light can’t break free. But the evidence that they exist is plain. Tremmel explained that we have observed stars orbiting rapidly around the center of our own galaxy. By gauging the trajectories of these stars we reach one conclusion about what they are orbiting.

“This object must be really, massive, and really, really small,” he said. “The only thing this thing could be is a black hole that is a billion solar masses.”

Astronomy and beer go together at Bad Jimmy's.

Astronomy and beer go together at Bad Jimmy’s.

We’ve seen the evidence of black holes in other galaxies by catching the glow of gas as it is consumed by supermassive black holes.

“This gas is flowing in, spiraling around, and becoming very, very hot,” Tremmel noted. “As that gas gets really hot it emits a lot of light.”

Tremmel said it’s an exciting time for his field of study, trying to figure out more about the formation of supermassive black holes.

“These relatively tiny objects within a galaxy are a true mystery still for astronomers,” he said.

The next Astronomy on Tap Seattle is scheduled for Wednesday, May 20 at 7 p.m. at Bad Jimmy’s. It’s free, and you can RSVP here.

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White spots on Ceres may be salt

The first big surprise as the Dawn spacecraft was approaching the dwarf planet Ceres earlier this year were bright white spots on its surface. Now that Dawn has been orbiting Ceres for six weeks, a theory has emerged about what the spots are: salt.

Dr. Tom McCord, a planetary physicist who is co-investigator on the Dawn mission, spoke about the exploration of Ceres Saturday during an astronomy day event at the Pacific Science Center in Seattle. Photo: Greg Scheiderer.

Dr. Tom McCord, a planetary physicist who is co-investigator on the Dawn mission, spoke about the exploration of Ceres Saturday during an Astronomy Day event at the Pacific Science Center in Seattle. Photo: Greg Scheiderer.

Dr. Tom McCord, a co-investigator on the Dawn mission and director of the Bear Fight Institute, a research organization based in Winthrop, Wash., spoke at an Astronomy Day event Saturday at the Pacific Science Center in Seattle. Here’s why he thinks the spots could be salt.

McCord explained that Ceres is differentiated: it has a rocky core, a water-ice mantle layer, and a dirty crust. He noted that they’ve learned a lot from the early photographs.

“There’s a lot of evidence of activity; many craters, an older surface, but not as old as the object, so something obliterated the craters from early on,” McCord said. “Distorted features, so the surface had to have been warped.”

“There are domes, things pushing out from the inside,” he continued, “and bright spots that suggest that material from inside has come to the surface in some sort of volcanism.”

In addition, McCord explained that ground-based telescopes have detected water vapor that comes and goes in the area of Ceres. Liquid water from the interior of Ceres may be being ejected to the surface, where it wouldn’t last long.


This image was taken by NASA’s Dawn spacecraft of dwarf planet Ceres on Feb. 19 from a distance of nearly 29,000 miles (46,000 kilometers). It shows that the brightest spot on Ceres has a dimmer companion, which apparently lies in the same basin. Photo: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA.

“What that would do is leave a residual salt deposit, so these bright spots could be salt deposits that accumulated around vents—volcanos—where the water is coming through,” McCord speculated.

He stresses that the work on data from Ceres is still in its early phases, joking that, “We scientists don’t know entirely what we are seeing.”

McCord said the evidence of geological activity has been the most interesting finding so far at Ceres.

“It has been active and may well still be active today,” he said. “That’s exciting to a physicist because you really want to know whether these processes that you conjure up in your models really have happened and, we hope to learn, to what extent and over what time scale.”

Ceres is a great target for study because it may hold clues to how planets form. It is the only dwarf planet in the inner solar system and is the largest object in the asteroid belt. With a diameter of 590 miles, it’s about as big as Texas.

“This is a very large small planet,” McCord said. Ceres comprises about a third of the mass of all objects in the asteroid belt.

The Dawn spacecraft is unique, according to McCord.

“It is the only interplanetary spacecraft that uses ion propulsion, and that is the only reason we are able to orbit two different objects in the outer solar system and still have enough fuel to go on,” he said. Dawn launched in 2007 and studied the asteroid Vesta for 14 months in 2011 and 2012 before heading to Ceres.

“Dawn is really a pathfinder for this kind of multiple-object extended exploration,” McCord said.

Dawn will be collecting data at Ceres for another year to 18 months. McCord said the spacecraft has four momentum wheels and needs three of them to hold itself in stable position. However two of the wheels have failed, so mission scientists are using the craft’s thrusters as a substitute. The hydrazine fuel will eventually run out, and Dawn will tumble about in a stable orbit around Ceres for a long, long time.