Black holes and LIGO on Bainbridge Island

The Laser Interferometer Gravitational-wave Observatory—LIGO—is leading scientists to discoveries at an impressive clip. Just two years ago we wrote about UW Bothell physics professor Joey Shapiro Key’s talk to the Seattle Astronomical Society about the detection of gravitational waves from the merger of two stellar-mass black holes—a discovery that won the Nobel Prize. Last week at Bainbridge Island Open Mic Science Key talked about LIGO, its latest detections, and plans for even bigger science in the future.

Joey Shapiro Key

Interferometers are a simple idea. They have two perpendicular arms of equal length. Laser light is split into the two arms, hits mirrors at the far ends, and returns to the source. If something changes the length of an arm, the light waves interfere with each other. LIGO in Hanford and a twin observatory in Louisiana are huge observatories with arms four kilometers long, and they are making amazing measurements.

“When we detect the gravitational waves they are quite pristine, even from billions of light years away,” Key explained. “But it was a challenge because gravitational waves interact so weakly with matter—that’s why they’re so pristine when they reach us—they’re very hard to detect.”

How hard? Einstein, who thought up the notion of gravitational waves and did the math to explain how they would work, thought the effect was too small to ever detect. It took a century to develop the technology to do it. LIGO can detect unbelievably minute changes in the length of its arms when a wave passes through.

“This is the most sensitive measuring device in the world,” Key said of LIGO. “For those four-kilometer arms, the change in the length in the arms we measure is a thousand times smaller than the width of a proton in the center of an atom.”


Simulation by SXS

The big discovery by LIGO since Key’s previous talk came in August of 2017.

“We detected a gravitational-wave signal from two neutron stars colliding, followed immediately by a detection of a gamma-ray burst by NASA’s Fermi satellite, and this set off a worldwide search for the source of that gravitational wave signal,” Key said. More than half a dozen observatories were involved in the work, observing the event in many wavelengths across the electromagnetic spectrum and pinning down the galaxy in which the collision occurred.

“This is the first ever multi-messenger detection with gravitational waves where we’re doing observations using gravitational waves and light,” Key said. Being able to see light from the event taught us a lot.

“We really learned from this one in particular that most of the heavy elements in our universe, including what solar systems are made of, what planets are made of, and what we are made of, comes from neutron stars colliding and kilonova events,” Key noted.

Just as light has a wide range of wavelengths, so do gravitational waves. Key said LIGO can only detect a limited slice of those wavelengths. It would be not able to find gravitational waves from the collisions of supermassive black holes or from the early universe. That will take a different tool.

“The future of gravitational wave astronomy lies in experiments such as LISA, the Laser Interferometer Space Antenna, that will do laser interferometry in space,” Key said. LISA is a joint venture between NASA and the European Space Agency, but there will be a bit of a wait for it. LISA’s planned launch isn’t until 2034. In the meantime, LIGO has plenty to do, with planned upgrades that will make the detector even more sensitive.

“We really are in a brand new era of gravitational wave astronomy, and there’s a lot to be discovered,” Key said.

Hanging out with comet hunter David Levy

One of the great perks of membership in the Seattle Astronomical Society is that the speakers at its annual banquet are typically dynamite. This year’s event featured one of the giants of astronomy, David H. Levy, who has discovered 22 comets, including the famous Shoemaker-Levy 9 that slammed into Jupiter in 1994.

Levy’s talk was highly autobiographical, which is fitting because his own autobiography, A Nightwatchman’s Journey: The Road Not Taken, is scheduled to come out this summer. Levy’s story is not necessarily complete, however; he’s still at it.

“Astronomers never really retire; you certainly don’t retire from being an amateur astronomer because it’s in your blood, it’s what you do, it’s what you live for,” Levy noted.

“I don’t think I’m ever going to discover another comet,” he said. “I’m still searching, because the search is so much fun!”

Several events from his youth seemed to steer Levy to a life in astronomy. Leslie Peltier discovered the Comet Kesak-Peltier in June of 1954 when Levy was about six years old. Later, when he was in high school, Levy was assigned to do a report on a book of his choosing. He picked Starlight Nights: The Adventures of a Star-Gazer, an autobiography of Peltier that had just been released. Levy couldn’t put it down, and it remains his all-time favorite book.

His parents sent him to Twin Lake Camp for three summers, and he didn’t like it much, but one year while returning to his cabin after a fireworks display he saw a shooting star and took it as an omen.

Then, in 1960 Levy had to do a public speech on any topic. He chose comets. Just before graduation, Levy crashed while riding his bicycle and broke his arm. A cousin gave him a book about the solar system as a get-well present. He devoured it.

“Any doubt that I was going to be interested in the night sky after that was erased,” Levy said. “All there was to do was astronomy.”

Seattle Astronomy’s Greg Scheiderer (left) visited with
comet hunter and author David H. Levy at the Seattle
Astronomical Society banquet Jan. 27.

Like many astronomers amateur and professional, Levy has kept a log book with notes about all of his observing sessions. His dates back to 1959 when he saw a partial solar eclipse, and as of the end of January included an amazing 20,922 sessions.

“Each one of them I cherish,” Levy smiled, noting about note-taking that, “If you don’t write it down, you haven’t done it.”

His first session looking for comets is dated December 17, 1965. It was nearly 19 years until he found his first in 1984. He’d logged a half dozen by 1990. Most of his comet hunting was visual in the early days, but it was around 1990 that he started doing photographic searches in partnership with Gene and Carolyn Shoemaker. One of the comets they discovered together is Shoemaker-Levy 9.

The gag among comet hunters is that to get famous your discovery has to become really bright. Shoemaker-Levy 9 didn’t do that, but the spectacular collision of its fragments with Jupiter in 1994 was a historic event.

“What it’s famous for is what it taught us,” Levy said “In colliding with Jupiter, it gave Earth a lesson in the origin of life.”

“It doesn’t prove that a comet collision means that life is going to start on a world,” he added. “What it does show is that when comets collide with a world, life eventually can start. It doesn’t mean that it does, but it’s one of the ways it does.”

“We’re all the progeny of comets,” Levy said.

His presentation was enjoyable and his autobiography promises to be an engaging read. It will be his 35th book. Watch for news about it in this space later this year.

A quick visit from 'Oumuamua

The first known interstellar object to visit our solar system came and went in a hurry, and didn’t give astronomers much time for observations. The strange ’Oumuamua was first discovered when it zipped past Earth in October, and by December it was already way too faint to see. Gregory Laughlin, astronomy professor from Yale, gave a plenary talk about ‘Oumuamua at the recent meeting of the American Astronomical Society held in Seattle.

Gregory Laughlin, astronomy professor at Yale,
gave a talk about ‘Oumuamua Jan. 7 at the 233rd
meeting of the American Astronomical Association,
held in Seattle. Photo: Drew Dettweiler.

About a half dozen observatories collected data about ‘Oumuamua as it sped through the inner solar system at 26 km/sec. Laughlin said they computed a highly eccentric path that indicated that the object came from beyond our solar system. Spectra of ‘Oumuamua found it to be red and featureless. Much of the other stuff in the outer solar system, such as trojan asteroids, Kuiper Belt objects, and moons of other planets also are reddish.

“The immediate inference is that ‘Oumuamua is some kind of reddish, icy, volatile-rich body from another planetary system,” Laughlin said, “something that’s been ejected and which has traveled through space for a long time, and which has happened to encounter the solar system.”

Laughlin noted that there are a number of strange attributes of ‘Oumuamua. Even though it passed close to the Sun, there was no sign of coma, so there was no or very little fine dust on ‘Oumuamua. It has an odd period light curve that varies in magnitude by three in the space of hours, and that’s a lot. It suggests that ‘Oumuamua is monolithic. It was accelerating as it headed out of the solar system, a fact discerned because its path wasn’t a good match for a Keplerian orbit. The acceleration indicates there must be some sort of outgassing, but ‘Oumuamua didn’t exhibit the chaotic sort of tumbling usually associated with that. Instead, the object’s jet may swing it back and forth like a pendulum.

“We think that the acceleration, the rotation, and the chaotic light curve are all reasonably in match,” Laughlin noted. “There’s lots of mysteries with ‘Oumuamua, but it doesn’t appear that there’s anything completely crazy.”

Laughlin looks forward to a time when our observing tools are more sensitive and we can hunt down other such objects in interstellar space.

“‘Oumuamua’s presence is signaling a vast population of unseen planets,” Laughlin said. He figures there may be about 10²⁶ such objects in the galaxy. For ‘Oumuamua, he said the likelihood of getting close to another star is about once every 10¹⁴ to 10¹⁵ years.

“Those brief, exciting moments in September and October were wonderful for us, but they were really the time of ‘Oumuamua’s life,” he said.

Hawaiian names for astronomical objects

The relationship between astronomy and Hawaii has not always been a happy one. Witness the legal squabble about the construction of the Thirty Meter Telescope at Mauna Kea, which was just settled in court last fall. But there’s been a thaw in this cold war according to Ka’iu Kimura, executive director of the ‘Imiloa Astronomy Center in Hilo, Hawaii.

“I participated in ‘Imiloa from its very inception in an attempt to bring about collaboration between the indigenous and scientific communities,” Kimura said before Laughlin’s lecture. She recalled that the effort was hardly a collaboration at first, but sharing a space helped, and now they’ve arrived at an agreement that respects both sides.

“Major astronomical discoveries from both Haleakala and Mauna Kea are being given Hawaiian names, honoring Hawaii as a place of discovery and of profound knowledge,” Kimura said, adding that a name isn’t just what something or someone is called.

“A name represents the identity and gives insight to that someone or something’s origins and connections to others, and for Hawaiians this ancient practice affirms Hawaii’s ongoing contribution to global astronomical advancement.”

The name of our recent visitor was largely created by Larry Kimura, Ka’iu’s uncle and a professor of Hawaiian language and Hawaiian studies at the University of Hawaii, Hilo.

“We loosely translate ‘Oumuamua to mean a scout or messenger from the deep, distant past,” Ka’iu said. Future objects will be named by a working group that includes astronomers, indigenous Hawaiians, educators, and community leaders. Kimura believes that the collaboration builds deeper appreciation and creates a shared sense of ownership in the outcomes.

Total lunar eclipse visible from Seattle

Seattle astronomy buffs are downright pessimistic about seeing celestial events, even those that happen during our good-weather months. (And we have them.) Thus in the week before the total lunar eclipse of January 20, 2019, I posted this on the Seattle Astronomy Facebook page.

Amazingly enough, at about mid-day on eclipse day the clouds actually did begin to part a little, and a check of the Seattle Clear Sky Chart revealed a prediction that we’d have just 30 percent cloud cover come eclipse hour, and that it would be downright clear late in the evening.

One learns not to trust these things, but when the full Moon actually got up above the trees and into a clear sky out back of Seattle Astronomy headquarters, I decided this was going to happen and hauled the telescope out of the basement and onto the back deck. As the eclipse began I snapped a quick photo in order to express my amazement.

The shadow of Earth is moving across the Moon and we can SEE it in Seattle! pic.twitter.com/xgt4oF2RpH

— Seattle Astronomy (@SeattleAstro) January 21, 2019

I am not an astrophotographer, as people who evaluate the entries for the Seattle Astronomical Society‘s quarterly photo contest always remind me. This one was shot with my smartphone, though when using it with the telescope I find it devilishly difficult to get the proper aim through the eyepiece (must pick up one of those gadgets from Cloud Break Optics soon.) My other “astro” camera is an old Canon Powershot A530, which is pretty easy to just stick up to the eyepiece and shoot.

I used the phone to get a pretty OK, if somewhat pixellated, pic at totality, too.


Interestingly enough, I found that the color of the “blood Moon” wasn’t quite so pronounced through the telescope and camera is it was in my naked-eye view. I think the magnification diffuses the color a bit, and the camera isn’t really made for that sort of work.

Even my sweetie, who is not normally prone to looking through telescopes at night in January, or any other month, for that matter, went out quite a few times for a magnified look, and we both spent most of the eclipse watching from a warm environment inside behind the glass of the French doors.

I hope you got a chance to see the eclipse wherever you were. The next one visible in Seattle will happen in May of 2021.

Searching for life with giant telescopes

The Kepler Space Telescope discovered more than 2,600 exoplanets—planets orbiting stars other than our Sun. Kepler used the transit method, watching for tiny dips in the amount of light coming from a star when a planet passed in front of it. After more than nine years in space, Kepler ran out of fuel last month and NASA officially ended the telescope’s science mission. The torch has been passed to a new generation of planet hunters, and experts in the field of exoplanets say we may be less than a decade away from answering one of humanity’s biggest questions: is there life somewhere besides Earth?

Harvard physics Prof. David Charbonneau
gave a lecture at the UW Oct. 16.
Photo: Greg Scheiderer.

“We are the special generation that for the first time in human history is going to have the technological ability—if we choose—to go and answer this great question,” said David Charbonneau, professor of astronomy at Harvard University and a member of the Kepler mission team. Charbonneau gave a lecture recently at the University of Washington, part of the Frontiers of Physics series. He suggests that when we look for an inhabited planet, we don’t confine ourselves to just finding people.

“There may be other humans out there, but I’m going to advocate that we need to create and cast the broadest net possible when we go and actually make the first search for life outside the solar system,” Charbonneau said. He noted that SETI has been listening for years with no contact so far, and other planets are too far away to visit any time soon. But we are on the verge of being able to analyze the chemical content of exoplanet atmospheres, and that can tell us if there’s life on the ground. A scientist on a distant planet looking at Earth could tell there is life here by the chemicals in our atmosphere.

“Life has radically changed the content of our atmosphere,” he said, by creating oxygen and other elements. “We’re going to try to detect life through the unintentional waste products that are produced as life goes about its business.”

News reports of discoveries often note if an exoplanet is “Earth-like,” but in reality we know little about conditions on these far-away worlds. We can accurately figure an exoplanet’s size, mass, and density, but know little else about them. Two new telescopes—one in space, one on the ground—may be able to give us the data we need to know about actual conditions on these planets.

Giant Magellan Telescope

The Giant Magellan Telescope (GMT) is being built in Chile by an international consortium, and is expected to begin science operations around 2023. The GMT will be the largest optical telescope ever constructed, with seven 8.5-meter mirrors. This huge telescope will be able to gather an enormous amount of light, enough to analyze the atmospheres of exoplanets.

James Webb Space Telescope

The James Webb Space Telescope (JWST) is a NASA project scheduled to launch in 2021. JWST will have a 6.5-meter primary mirror, and the observatory will be able to observe light in the infrared, and that’s important.

“Infrared is where all the molecules we want to study show their fingerprints,” Charbonneau said, listing oxygen, water, and methane among the molecules of interest.

He said the JWST “will revolutionize essentially all major branches of astrophysics.”

Charbonneau said we need both of the new telescopes to nail down whether an exoplanet is inhabited.

“Individually, a large ground-based telescope or the James Webb Space Telescope cannot tell us if there’s life on a planet,” he said. That’s because they’re sensitive to different molecules. The GMT could spot oxygen, which usually means life. It’s not certain, though, because oxygen could be created in other ways. The JWST could find methane, carbon monoxide, and carbon dioxide, which would put that oxygen in context, determining if it’s there because of biological activity.

“The idea is together they can get the data that will allow us to conclude that there really is life,” Charbonneau said.

TESS and MEarth

While we wait for these two observatories to be completed, astronomers are not sitting idly by. NASA’s Transiting Exoplanet Survey Satellite (TESS) is continuing the work of Kepler, using the transit method to search for more exoplanets.

“Our mission is to find hundreds of nearby small planets amenable to detailed characterization,” said Charbonneau, who is a co-investigator on the mission. TESS will survey the entire sky over a period of two years. It was launched in April, began science work in August, and found its first exoplanet in September. Charbonneau said that by December they should have the data to determine if this new exoplanet has an atmosphere.

Charbonneau is the primary investigator for the MEarth Project, which is searching for habitable exoplanets around nearby stars. MEarth consists of two automated observatories, one near Tucson, Arizona and the other in Chile. Each employs eight robotic 16-inch telescopes that constantly watch M-dwarf stars for transiting exoplanets. There are several good reasons to look at these “red dwarf” stars. They’re plentiful—there are about 240 of them within 30 light years of us, compared to just 20 G-stars like the Sun. Since they’re smaller stars and not as bright, they won’t wash out an orbiting planet’s atmosphere, making the observation technically easier.

The following time-lapse video shows the MEarth-North observatory in action.

The point of both TESS and MEarth is to create a good list of things for GMT and JWST to check out once they come on line.

“The search for atmospheric biomarkers such as oxygen will be humanity’s first attempt to really answer this great question about whether or not we are alone,” Charbonneau said.

You can watch the entire lecture here: