Space oddities at Astronomy on Tap Seattle

Things got a little strange at the most recent gathering of Astronomy on Tap Seattle, and not just because we were all drinking beer at Hilliard’s Beer Taproom in Ballard and enjoying eats from the Cave Man Food Truck parked outside. The event, organized by astronomy graduate students at the University of Washington, took on space oddities like Hanny’s Voorwerp and Thorne-Żytkow Objects.

Seattle Astronomy gets all sentimental about Hanny’s Voorwerp because it has a cool name and it was a subject of our third post ever when we started this effort in January 2011. The Voorwerp was noticed by Hanny van Arkle, a Dutch schoolteacher who was categorizing galaxies in Sloan Digital Sky Survey images as part of the Galaxy Zoo project. The object (voorwerp is Dutch for thing or object) appeared as a blue blob near the galaxy IC 2497.

What’s a voorwerp?

Ruan

During his talk titled, “Citizen Discovers Strange Black Hole Echoes: The Science Behind Hanny’s Voorwerp,” UW graduate student John Ruan said there were four ideas about what it was. All of them were wrong.

Imaging artifact. It could have been just a blip on the camera, Ruan said, but other observers were able to spot it.

Unknown solar system object. Ruan said solar system objects move rapidly, but the Voorwerp was found on photographic plates made more than 50 years ago, and it hadn’t budged.

Distant, high-redshift galaxy. The redshift was not high enough for the Voorwerp to be at great distance.

Milky Way nebula. Conversely, it wasn’t something in our own galaxy, either, this time because the redshift was not great enough.
It was in examining the spectra, though, that Ruan said a clue was found. The emission lines were strong.

“To get emission lines that are this strong, you need a really, really bright source that emits a lot of high-energy light,” Ruan said, the kind of light you get from gas falling onto a black hole. “This is evidence that this object was produced by a quasar.”

Hanny’s Voorwerp appears as a green blob
in this photo by NASA, ESA, W. Keel
(University of Alabama), and the Galaxy Zoo Team.

There was just one small problem with the idea. There’s no quasar in any of the photos. Ruan said the quasar was probably created when the galaxy merged with a smaller one.

“It disturbs the gas in this larger galaxy, and this gas, some of it, because it’s disturbed it will fall into the center of the galaxy and fall into the black hole,” Ruan explained. This ignited the quasar, but at some point it literally ran out of gas.

“That quasar became quiet again, and it looked like just a normal galaxy, however the gas cloud that the quasar was shining on still appears to be lit up,” he said. “And that is Hanny’s Voorwerp.”

Similar objects have been discovered and are generally referred to as quasar ionization echoes. Ruan said Hanny’s Voorwerp will gradually fade as the ionization of the gas wears off.

The weirdest stars in the universe

Emily Levesque is just finishing her first year on the astronomy faculty at the University of Washington, and her research bailiwick fit perfectly into space oddity night.

Levesque

“I study weird stars, strange stars, the really oddball stars that we can’t easily explain,” Levesque said. Indeed, she started out looking at the odd couple of stars: red supergiants and neutron stars.
Red supergiants are enormous, massive, relatively cool stars. The largest one found so far is so big that it’s surface, if it were plunked into our solar system in place of the Sun, would reach almost out to the orbit of Saturn. Neutron stars are the small, dense remains of supernovae. They are no bigger than a city.

“There’s only one thing that I can do to red supergiants and neutron stars to make them weirder at this point,” Levesque said. “If we put a red supergiant and a neutron star into a binary, and we merge them, we get a very, very weird object.”

The TŻO

The weird object is called a Thorne-Żytkow Object (TŻO) because Kip Thorne of Caltech and Anna Żytkow of the University of Cambridge hypothesized just this sort of thing way back in 1977. Żytkow heard that Levesque was studying red supergiants, and sent an email asking if she’d like to give a shot at spotting a TŻO. It was quite a challenge.

“A neutron star is the size of the city of Seattle,” Levesque said. “A red supergiant is bigger than the orbit of Jupiter. If you embed a neutron star inside a red supergiant it’s virtually impossible to detect.”

As with Hanny’s Voorwerp, the spectra were the key. Inside a TŻO, convection pockets would circulate material and create bizarre chemical processes. As stuff nears the neutron star at the core it would be bombarded with protons, changing it into a different element. Then as it nears the surface of the star, it would decay into yet something else. The process repeats. If the spectrum reveals the presence of elements that you would not normally expect to see at the surface of a cold star, you may be onto something.

Two years ago Levesque and her team looked at 100 red supergiants, and 99 of them appeared normal. The spectrum of one of them, HV 2112, showed unusual concentrations of rubidium, lithium, and molybdenum.

“This was a signature that we’d actually found the first example of a Thorne-Żytkow Object in the universe,” Levesque said.

If true, it means a new way to make stars and a new way to make elements. Levesque said they’re still calling the star a candidate or possible TŻO because of the Sagan Standard that holds that extraordinary claims require extraordinary evidence.

“The evidence that we have is really compelling, but it’s three little blips in a spectrum,” Levesque said. “We desperately want to find more of these, we want to find other ways of detecting them. We’d ultimately love to have a whole set of Thorne-Żytkow Objects, and have a whole set of stars that we can look at that can hold the title of weirdest star in the universe.”

The universe is big, even in small spaces

The universe is pretty vast even in confined spaces. That was the lesson given on opposite ends of the size scale at the most recent Astronomy on Tap Seattle event hosted at Hilliard’s Beer Taproom by University of Washington graduate students in astronomy.

Ethan Kruse

Grad student Ethan Kruse was all set to give a talk that concluded we would never even get out of our solar system because it is way too big. Then a few weeks before the talk Stephen Hawking and friends announced their plan for getting all the way to neighboring star Alpha Centauri in 20 years through a project called Breakthrough Starshot.

“If I’m disagreeing with Stephen Hawking,” Kruse recalled thinking, “I should probably stop for a minute and reevaluate my thesis.”

Kruse remained on point about the mind-boggling scale of the universe. He said that if our Sun was the size of a basketball sitting on the stage of Hilliard’s, Earth would be the size of a sesame seed in the back of the room, 84 feet away, and the orbiting Moon would be the size of a grain of salt. At this scale Jupiter would be a golf ball on the Ballard Bridge and Pluto would be a grain of salt about a kilometer away—about the distance to Bad Jimmy’s Brewing Company, which served as the venue for Astronomy on Tap Seattle for its first year. Alpha Centauri, in this set-up, is some 4,400 miles away—in London or Tokyo.

Kruse pointed out that the fastest spacecraft we have built so far, New Horizons, took a decade to get to Pluto.

“We went from Hilliard’s to Bad Jimmy’s in ten years,” he observed. “Don’t worry guys, we’re going to go to London in 20 years!”

The idea behind Starshot is that a super-light craft with a light sail could be accelerated by lasers to up to 20 percent of the speed of light. Kruse outlined a litany of technological challenges with the concept, including the ability to generate sufficient laser power, creating an adequately reflective material for the sails, being able to accurately aim the lasers at great distances, and shielding the craft from possible collisions with space debris. Still, he concluded, the idea is worth exploring, especially since the same technology could be used to explore the solar system more quickly.

“This is honestly the most realistic thing that anyone has proposed so far for getting to any other star system,” Kruse said.

It will, however, take a great deal of research and development.

“Don’t necessarily count on this before you die,” Kruse concluded. “Space is big.”

Jessica Werk

Professor Jessica Werk, one of the newest hires onto the astronomy faculty at the University of Washington, also used sports equipment to illustrate her talk, “The History of You: The Rather Tumultuous Past of the Atoms in Your Body.” Werk pointed out that atoms are mostly empty space. If the nucleus of an atom were the size of a baseball, the nearest electrons would be a football field away.

After the Big Bang the universe was mostly light atoms: hydrogen and helium and a few others. Where did the carbon and calcium and other heavier stuff we’re made of come from?

“All evidence suggests that these atoms were fused in the cores of very, very massive stars twelve-and-a-half billion years ago,” Werk said. “Since then they have been on an absolutely crazy, long, sometimes violent journey to end up in your body 93 million miles from the Sun on this speck named Earth.”

Those atoms took a somewhat circuitous route to get here.

“Sixty percent of the atoms in your body we at one point outside of the galaxy in the circumgalactic or intergalactic medium,” Werk said. We don’t really know how they got here, but the best theory is that the atoms tend to cool off, and the gas rains back down on the galaxy, collapsing in star formation or becoming part of the debris disk out of which planets form.

There’s some mind-bending scale at the atomic level, too. Werk pointed out that there are 10²³ atoms in a breath of air.

“Each breath-full of air contains more atoms than the number of breath-fulls of air in the entire Earth’s atmosphere,” she said. “What that means is that it is very likely that the last breath of air you just took contained at least one oxygen atom from the first breath of air that you ever took as a human being on planet Earth.”

That reminds us of a recent post by Ethan Siegel on the blog Starts With a Bang, in which he concluded that we all probably share atoms that were once part of King Tut or any other historical figure you might name.

“The matter that makes up your physical body is part of a huge universe that is continually evolving and recycling the material in it into new forms,” Werk concluded.