John O’Meara, in Rome this past March to present a poster at the “Science with the Hubble Space Telescope IV” meeting, poses in the Vatican Museum beside a celestial globe made in 1567 by Giavanni Antonio Vanosino, dramatizing how much leading scientists’ view of the heavens has changed in the last 400-plus years.
The world’s top scientists compete for time on the Hubble Space Telescope -- time measured and allocated by orbits -- and only a small percentage of proposals get the green light.
That’s why John O’Meara, a Saint Michael’s College physics professor and internationally prominent researcher on galaxy-formation, feels so lucky that he and some colleagues recently got a “go” with a $333,338 grant from the NASA-funded Space Telescope Science Institute for their relatively large “60-orbit” investigation into million-degree (K) gas in the outer regions of galaxies. They hope to be the first ever to scientifically detect this gas in the so-called “circum-galactic medium” of a distant galaxy thanks to changing “viewing” conditions in the universe that might allow observation of once-unobservable phenomena.
O’Meara says they already obtained their data in April and May and analysis is under way. “This gas would be a very exciting advance if we detect it,” he says, explaining that the main reason it never has been detected before is that “the signatures typically occur at X-ray wavelengths, but because of the expansion of the universe, the wavelengths have been red-shifted to the ultraviolent, where an instrument called the Cosmic Origins Spectrograph on Hubble can measure them.”
He says their new data will be combined with data from the powerful Keck Telescope in Hawaii and other instruments on Hubble to facilitate the analysis. The principal investigator is Todd Tripp of UMass Amherst, with whom O’Meara has collaborated before. If they find what they think they’ll find, he says, it will tell them a lot more about how galaxies get the gas fuel that they need to make stars, and what they do once they make the stars.
O’Meara says Hubble orbits Earth every hour and a half and costs NASA something like $50 per second to operate, give or take maybe $20. Typically, proposals for using it require anywhere from 20 up to 100 or more orbits to complete in most cases, though much smaller ones are possible too. For instance, he was principal investigator in a 40-orbit program once, but also for a smaller project called a “snapshot program.”
Most of the NASA grant money O’Meara and his colleagues just received will pay for post-doctorate research, graduate students, travel, publication costs, summer salary for professors and other similar expenses. Whenever NASA grants time using Hubble for a project they are interested in, there’s no charge to the researchers for that time.
He says he’s seen “how the sausage is made from the other side” in the granting of Hubble time since he once was on the panel that goes through proposals. “The best science always gets orbits,” O’Meara says, adding that he has been in on lots of proposals that haven’t been approved, including three others in the recent round of applications that were ranked in the upper 20 percent.
“If you’re writing a proposal for Hubble, you have to be writing science that only Hubble can do,” he says. “If it looks like it can be done on the ground, then no way.”
He says the Goddard Space Flight Center in Maryland tells the Hubble where to point and the data goes to the Space Telescope Science Institute to their archives so scientists like O’Meara and his colleagues can just call it up on their computers. “I’ve downloaded Hubble data from the beach in Hawaii,” he says.
“When we look at these galaxies we’re seeing light that’s billions of years old from a time when the universe was billions of years younger, so the expansion of the universe is shifting this light,” he explains. “The universe is 13.7 billion years old and the light left this object when the universe was only 3 billion or so years old – still just in its adolescence!”
“Where this science got lucky is that we found a specific object and are using Hubble to point at just one thing for 60 orbits, which normally doesn’t happen,” he says, “but we need very high quality data to look for very weak features indicative of this million-degree gas.” The object they’ve been pointing Hubble at repeatedly is a quasar, which O’Meara describes as “the bright central engine of the galaxy.”
“Every galaxy has a giant black hole in the center, gas falls onto the black hole, heats up and as it heats up it emits light, so we use the quasar as a background light source – we just use it as a light bulb and the light comes from the quasar towards the telescope and gets absorbed along the way, so if there’s a gas cloud between us and the quasar, it will eat up some of the light – you could say we’re doing physics in silhouette since we can’t actually see these gas clouds – they’re way too faint.”
With 60 orbits, “you get exquisite data so you can look at lots and lots of things, which is why the grant is as large as it is,” he says. The broader point of the work is that “it just helps us confirm certain models of galaxy formation and extends our knowledge of the surroundings of galaxies.”
O’Meara has been principal on Hubble projects three times and a co-investigator on more than he can count. The Hubble, launched in 1990, will celebrate its 25th anniversary soon. O’Meara is on sabbatical for the coming year, his first at Saint Michael’s, and his Hubble work will be a big part of it. During the sabbatical O’Meara plans a lot of travel to his most commonly visited work sites, for telescope observations or research: Hawaii, Chile, Maryland, the University of Notre Dame, and perhaps Australia or Europe.
The red-shifting wavelengths of light that make their recent observations possible were a longshot to occur, he says. “The chances of it happening were very small since less than one percent of quasars will allow us to do this trick, but this one happens to be very bright.”
“We got lucky – the universe gave us a present, and we’re just trying to open it,” he says.